Patchwork [v2,06/10] CMA: generalize CMA reserved area management functionality

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Submitter Joonsoo Kim
Date June 12, 2014, 3:21 a.m.
Message ID <1402543307-29800-7-git-send-email-iamjoonsoo.kim@lge.com>
Download mbox | patch
Permalink /patch/358956/
State New
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Comments

Joonsoo Kim - June 12, 2014, 3:21 a.m.
Currently, there are two users on CMA functionality, one is the DMA
subsystem and the other is the kvm on powerpc. They have their own code
to manage CMA reserved area even if they looks really similar.
From my guess, it is caused by some needs on bitmap management. Kvm side
wants to maintain bitmap not for 1 page, but for more size. Eventually it
use bitmap where one bit represents 64 pages.

When I implement CMA related patches, I should change those two places
to apply my change and it seem to be painful to me. I want to change
this situation and reduce future code management overhead through
this patch.

This change could also help developer who want to use CMA in their
new feature development, since they can use CMA easily without
copying & pasting this reserved area management code.

In previous patches, we have prepared some features to generalize
CMA reserved area management and now it's time to do it. This patch
moves core functions to mm/cma.c and change DMA APIs to use
these functions.

There is no functional change in DMA APIs.

v2: There is no big change from v1 in mm/cma.c. Mostly renaming.

Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Minchan Kim - June 12, 2014, 7:13 a.m.
On Thu, Jun 12, 2014 at 12:21:43PM +0900, Joonsoo Kim wrote:
> Currently, there are two users on CMA functionality, one is the DMA
> subsystem and the other is the kvm on powerpc. They have their own code
> to manage CMA reserved area even if they looks really similar.
> >From my guess, it is caused by some needs on bitmap management. Kvm side
> wants to maintain bitmap not for 1 page, but for more size. Eventually it
> use bitmap where one bit represents 64 pages.
> 
> When I implement CMA related patches, I should change those two places
> to apply my change and it seem to be painful to me. I want to change
> this situation and reduce future code management overhead through
> this patch.
> 
> This change could also help developer who want to use CMA in their
> new feature development, since they can use CMA easily without
> copying & pasting this reserved area management code.
> 
> In previous patches, we have prepared some features to generalize
> CMA reserved area management and now it's time to do it. This patch
> moves core functions to mm/cma.c and change DMA APIs to use
> these functions.
> 
> There is no functional change in DMA APIs.
> 
> v2: There is no big change from v1 in mm/cma.c. Mostly renaming.
> 
> Acked-by: Michal Nazarewicz <mina86@mina86.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Acutally, I want to remove bool return of cma_release but it's not
a out of scope in this patchset.

Acked-by: Minchan Kim <minchan@kernel.org>

> 
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index 00e13ce..4eac559 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -283,16 +283,6 @@ config CMA_ALIGNMENT
>  
>  	  If unsure, leave the default value "8".
>  
> -config CMA_AREAS
> -	int "Maximum count of the CMA device-private areas"
> -	default 7
> -	help
> -	  CMA allows to create CMA areas for particular devices. This parameter
> -	  sets the maximum number of such device private CMA areas in the
> -	  system.
> -
> -	  If unsure, leave the default value "7".
> -
>  endif
>  
>  endmenu
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index 9bc9340..f177f73 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -24,25 +24,10 @@
>  
>  #include <linux/memblock.h>
>  #include <linux/err.h>
> -#include <linux/mm.h>
> -#include <linux/mutex.h>
> -#include <linux/page-isolation.h>
>  #include <linux/sizes.h>
> -#include <linux/slab.h>
> -#include <linux/swap.h>
> -#include <linux/mm_types.h>
>  #include <linux/dma-contiguous.h>
>  #include <linux/log2.h>

Should we remain log2.h in here?

> -
> -struct cma {
> -	unsigned long	base_pfn;
> -	unsigned long	count;
> -	unsigned long	*bitmap;
> -	int order_per_bit; /* Order of pages represented by one bit */
> -	struct mutex	lock;
> -};
> -
> -struct cma *dma_contiguous_default_area;
> +#include <linux/cma.h>
>  
>  #ifdef CONFIG_CMA_SIZE_MBYTES
>  #define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES
> @@ -50,6 +35,8 @@ struct cma *dma_contiguous_default_area;
>  #define CMA_SIZE_MBYTES 0
>  #endif
>  
> +struct cma *dma_contiguous_default_area;
> +
>  /*
>   * Default global CMA area size can be defined in kernel's .config.
>   * This is useful mainly for distro maintainers to create a kernel
> @@ -156,199 +143,13 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
>  	}
>  }
>  
> -static DEFINE_MUTEX(cma_mutex);
> -
> -static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> -{
> -	return (1 << (align_order >> cma->order_per_bit)) - 1;
> -}
> -
> -static unsigned long cma_bitmap_maxno(struct cma *cma)
> -{
> -	return cma->count >> cma->order_per_bit;
> -}
> -
> -static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
> -						unsigned long pages)
> -{
> -	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
> -}
> -
> -static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
> -{
> -	unsigned long bitmapno, nr_bits;
> -
> -	bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
> -	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> -
> -	mutex_lock(&cma->lock);
> -	bitmap_clear(cma->bitmap, bitmapno, nr_bits);
> -	mutex_unlock(&cma->lock);
> -}
> -
> -static int __init cma_activate_area(struct cma *cma)
> -{
> -	int bitmap_maxno = cma_bitmap_maxno(cma);
> -	int bitmap_size = BITS_TO_LONGS(bitmap_maxno) * sizeof(long);
> -	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
> -	unsigned i = cma->count >> pageblock_order;
> -	struct zone *zone;
> -
> -	pr_debug("%s()\n", __func__);
> -
> -	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> -	if (!cma->bitmap)
> -		return -ENOMEM;
> -
> -	WARN_ON_ONCE(!pfn_valid(pfn));
> -	zone = page_zone(pfn_to_page(pfn));
> -
> -	do {
> -		unsigned j;
> -		base_pfn = pfn;
> -		for (j = pageblock_nr_pages; j; --j, pfn++) {
> -			WARN_ON_ONCE(!pfn_valid(pfn));
> -			/*
> -			 * alloc_contig_range requires the pfn range
> -			 * specified to be in the same zone. Make this
> -			 * simple by forcing the entire CMA resv range
> -			 * to be in the same zone.
> -			 */
> -			if (page_zone(pfn_to_page(pfn)) != zone)
> -				goto err;
> -		}
> -		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
> -	} while (--i);
> -
> -	mutex_init(&cma->lock);
> -	return 0;
> -
> -err:
> -	kfree(cma->bitmap);
> -	return -EINVAL;
> -}
> -
> -static struct cma cma_areas[MAX_CMA_AREAS];
> -static unsigned cma_area_count;
> -
> -static int __init cma_init_reserved_areas(void)
> -{
> -	int i;
> -
> -	for (i = 0; i < cma_area_count; i++) {
> -		int ret = cma_activate_area(&cma_areas[i]);
> -		if (ret)
> -			return ret;
> -	}
> -
> -	return 0;
> -}
> -core_initcall(cma_init_reserved_areas);
> -
> -/**
> - * dma_contiguous_reserve_area() - reserve custom contiguous area
> - * @size: Size of the reserved area (in bytes),
> - * @base: Base address of the reserved area optional, use 0 for any
> - * @limit: End address of the reserved memory (optional, 0 for any).
> - * @alignment: Alignment for the contiguous memory area, should be power of 2
> - * @order_per_bit: Order of pages represented by one bit on bitmap.
> - * @res_cma: Pointer to store the created cma region.
> - * @fixed: hint about where to place the reserved area
> - *
> - * This function reserves memory from early allocator. It should be
> - * called by arch specific code once the early allocator (memblock or bootmem)
> - * has been activated and all other subsystems have already allocated/reserved
> - * memory. This function allows to create custom reserved areas for specific
> - * devices.
> - *
> - * If @fixed is true, reserve contiguous area at exactly @base.  If false,
> - * reserve in range from @base to @limit.
> - */
> -static int __init __dma_contiguous_reserve_area(phys_addr_t size,
> -				phys_addr_t base, phys_addr_t limit,
> -				phys_addr_t alignment, int order_per_bit,
> -				struct cma **res_cma, bool fixed)
> -{
> -	struct cma *cma = &cma_areas[cma_area_count];
> -	int ret = 0;
> -
> -	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> -		__func__, (unsigned long)size, (unsigned long)base,
> -		(unsigned long)limit, (unsigned long)alignment);
> -
> -	/* Sanity checks */
> -	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
> -		pr_err("%s(): Not enough slots for CMA reserved regions!\n",
> -			__func__);
> -		return -ENOSPC;
> -	}
> -
> -	if (!size)
> -		return -EINVAL;
> -
> -	if (alignment && !is_power_of_2(alignment))
> -		return -EINVAL;
> -
> -	/*
> -	 * Sanitise input arguments.
> -	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
> -	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
> -	 * and CMA property will be broken.
> -	 */
> -	alignment = max(alignment,
> -		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
> -	base = ALIGN(base, alignment);
> -	size = ALIGN(size, alignment);
> -	limit &= ~(alignment - 1);
> -	/* size should be aligned with order_per_bit */
> -	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit));
> -
> -	/* Reserve memory */
> -	if (base && fixed) {
> -		if (memblock_is_region_reserved(base, size) ||
> -		    memblock_reserve(base, size) < 0) {
> -			ret = -EBUSY;
> -			goto err;
> -		}
> -	} else {
> -		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
> -							limit);
> -		if (!addr) {
> -			ret = -ENOMEM;
> -			goto err;
> -		} else {
> -			base = addr;
> -		}
> -	}
> -
> -	/*
> -	 * Each reserved area must be initialised later, when more kernel
> -	 * subsystems (like slab allocator) are available.
> -	 */
> -	cma->base_pfn = PFN_DOWN(base);
> -	cma->count = size >> PAGE_SHIFT;
> -	cma->order_per_bit = order_per_bit;
> -	*res_cma = cma;
> -	cma_area_count++;
> -
> -	pr_info("%s(): reserved %ld MiB at %08lx\n",
> -		__func__, (unsigned long)size / SZ_1M, (unsigned long)base);
> -	return 0;
> -
> -err:
> -	pr_err("%s(): failed to reserve %ld MiB\n",
> -		__func__, (unsigned long)size / SZ_1M);
> -	return ret;
> -}
> -
>  int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  				       phys_addr_t limit, struct cma **res_cma,
>  				       bool fixed)
>  {
>  	int ret;
>  
> -	ret = __dma_contiguous_reserve_area(size, base, limit, 0, 0,
> -						res_cma, fixed);
> +	ret = cma_declare_contiguous(size, base, limit, 0, 0, res_cma, fixed);
>  	if (ret)
>  		return ret;
>  
> @@ -358,124 +159,17 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  	return 0;
>  }
>  
> -/**
> - * dma_alloc_from_contiguous() - allocate pages from contiguous area
> - * @dev:   Pointer to device for which the allocation is performed.
> - * @count: Requested number of pages.
> - * @align: Requested alignment of pages (in PAGE_SIZE order).
> - *
> - * This function allocates memory buffer for specified device. It uses
> - * device specific contiguous memory area if available or the default
> - * global one. Requires architecture specific dev_get_cma_area() helper
> - * function.
> - */
> -static struct page *__dma_alloc_from_contiguous(struct cma *cma, int count,
> -				       unsigned int align)
> -{
> -	unsigned long mask, pfn, start = 0;
> -	unsigned long bitmap_maxno, bitmapno, nr_bits;
> -	struct page *page = NULL;
> -	int ret;
> -
> -	if (!cma || !cma->count)
> -		return NULL;
> -
> -	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
> -		 count, align);
> -
> -	if (!count)
> -		return NULL;
> -
> -	mask = cma_bitmap_aligned_mask(cma, align);
> -	bitmap_maxno = cma_bitmap_maxno(cma);
> -	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> -
> -	for (;;) {
> -		mutex_lock(&cma->lock);
> -		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
> -					bitmap_maxno, start, nr_bits, mask);
> -		if (bitmapno >= bitmap_maxno) {
> -			mutex_unlock(&cma->lock);
> -			break;
> -		}
> -		bitmap_set(cma->bitmap, bitmapno, nr_bits);
> -		/*
> -		 * It's safe to drop the lock here. We've marked this region for
> -		 * our exclusive use. If the migration fails we will take the
> -		 * lock again and unmark it.
> -		 */
> -		mutex_unlock(&cma->lock);
> -
> -		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
> -		mutex_lock(&cma_mutex);
> -		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
> -		mutex_unlock(&cma_mutex);
> -		if (ret == 0) {
> -			page = pfn_to_page(pfn);
> -			break;
> -		} else if (ret != -EBUSY) {
> -			clear_cma_bitmap(cma, pfn, count);
> -			break;
> -		}
> -		clear_cma_bitmap(cma, pfn, count);
> -		pr_debug("%s(): memory range at %p is busy, retrying\n",
> -			 __func__, pfn_to_page(pfn));
> -		/* try again with a bit different memory target */
> -		start = bitmapno + mask + 1;
> -	}
> -
> -	pr_debug("%s(): returned %p\n", __func__, page);
> -	return page;
> -}
> -
>  struct page *dma_alloc_from_contiguous(struct device *dev, int count,
>  				       unsigned int align)
>  {
> -	struct cma *cma = dev_get_cma_area(dev);
> -
>  	if (align > CONFIG_CMA_ALIGNMENT)
>  		align = CONFIG_CMA_ALIGNMENT;
>  
> -	return __dma_alloc_from_contiguous(cma, count, align);
> -}
> -
> -/**
> - * dma_release_from_contiguous() - release allocated pages
> - * @dev:   Pointer to device for which the pages were allocated.
> - * @pages: Allocated pages.
> - * @count: Number of allocated pages.
> - *
> - * This function releases memory allocated by dma_alloc_from_contiguous().
> - * It returns false when provided pages do not belong to contiguous area and
> - * true otherwise.
> - */
> -static bool __dma_release_from_contiguous(struct cma *cma, struct page *pages,
> -				 int count)
> -{
> -	unsigned long pfn;
> -
> -	if (!cma || !pages)
> -		return false;
> -
> -	pr_debug("%s(page %p)\n", __func__, (void *)pages);
> -
> -	pfn = page_to_pfn(pages);
> -
> -	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> -		return false;
> -
> -	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
> -
> -	free_contig_range(pfn, count);
> -	clear_cma_bitmap(cma, pfn, count);
> -
> -	return true;
> +	return cma_alloc(dev_get_cma_area(dev), count, align);
>  }
>  
>  bool dma_release_from_contiguous(struct device *dev, struct page *pages,
>  				 int count)
>  {
> -	struct cma *cma = dev_get_cma_area(dev);
> -
> -	return __dma_release_from_contiguous(cma, pages, count);
> +	return cma_release(dev_get_cma_area(dev), pages, count);
>  }
> diff --git a/include/linux/cma.h b/include/linux/cma.h
> new file mode 100644
> index 0000000..e38efe9
> --- /dev/null
> +++ b/include/linux/cma.h
> @@ -0,0 +1,12 @@
> +#ifndef __CMA_H__
> +#define __CMA_H__
> +
> +struct cma;
> +
> +extern int __init cma_declare_contiguous(phys_addr_t size,
> +				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment, int order_per_bit,
> +				struct cma **res_cma, bool fixed);
> +extern struct page *cma_alloc(struct cma *cma, int count, unsigned int align);
> +extern bool cma_release(struct cma *cma, struct page *pages, int count);
> +#endif
> diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h
> index 772eab5..a40c1f3 100644
> --- a/include/linux/dma-contiguous.h
> +++ b/include/linux/dma-contiguous.h
> @@ -53,9 +53,10 @@
>  
>  #ifdef __KERNEL__
>  
> +#include <linux/device.h>
> +
>  struct cma;
>  struct page;
> -struct device;
>  
>  #ifdef CONFIG_DMA_CMA
>  
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 3e9977a..f4899ec 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -508,6 +508,17 @@ config CMA_DEBUG
>  	  processing calls such as dma_alloc_from_contiguous().
>  	  This option does not affect warning and error messages.
>  
> +config CMA_AREAS
> +	int "Maximum count of the CMA areas"
> +	depends on CMA
> +	default 7
> +	help
> +	  CMA allows to create CMA areas for particular purpose, mainly,
> +	  used as device private area. This parameter sets the maximum
> +	  number of CMA area in the system.
> +
> +	  If unsure, leave the default value "7".
> +
>  config ZBUD
>  	tristate
>  	default n
> diff --git a/mm/Makefile b/mm/Makefile
> index 1eaa70b..bc0422b 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -62,3 +62,4 @@ obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
>  obj-$(CONFIG_ZBUD)	+= zbud.o
>  obj-$(CONFIG_ZSMALLOC)	+= zsmalloc.o
>  obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
> +obj-$(CONFIG_CMA)	+= cma.o
> diff --git a/mm/cma.c b/mm/cma.c
> new file mode 100644
> index 0000000..1e1b017
> --- /dev/null
> +++ b/mm/cma.c
> @@ -0,0 +1,330 @@
> +/*
> + * Contiguous Memory Allocator
> + *
> + * Copyright (c) 2010-2011 by Samsung Electronics.
> + * Copyright IBM Corporation, 2013
> + * Copyright LG Electronics Inc., 2014
> + * Written by:
> + *	Marek Szyprowski <m.szyprowski@samsung.com>
> + *	Michal Nazarewicz <mina86@mina86.com>
> + *	Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> + *	Joonsoo Kim <iamjoonsoo.kim@lge.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation; either version 2 of the
> + * License or (at your optional) any later version of the license.
> + */
> +
> +#define pr_fmt(fmt) "cma: " fmt
> +
> +#ifdef CONFIG_CMA_DEBUG
> +#ifndef DEBUG
> +#  define DEBUG
> +#endif
> +#endif
> +
> +#include <linux/memblock.h>
> +#include <linux/err.h>
> +#include <linux/mm.h>
> +#include <linux/mutex.h>
> +#include <linux/sizes.h>
> +#include <linux/slab.h>
> +
> +struct cma {
> +	unsigned long	base_pfn;
> +	unsigned long	count;
> +	unsigned long	*bitmap;
> +	int order_per_bit; /* Order of pages represented by one bit */
> +	struct mutex	lock;
> +};
> +
> +/*
> + * There is always at least global CMA area and a few optional
> + * areas configured in kernel .config.
> + */
> +#define MAX_CMA_AREAS	(1 + CONFIG_CMA_AREAS)
> +
> +static struct cma cma_areas[MAX_CMA_AREAS];
> +static unsigned cma_area_count;
> +static DEFINE_MUTEX(cma_mutex);
> +
> +static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> +{
> +	return (1 << (align_order >> cma->order_per_bit)) - 1;
> +}
> +
> +static unsigned long cma_bitmap_maxno(struct cma *cma)
> +{
> +	return cma->count >> cma->order_per_bit;
> +}
> +
> +static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
> +						unsigned long pages)
> +{
> +	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
> +}
> +
> +static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
> +{
> +	unsigned long bitmapno, nr_bits;
> +
> +	bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
> +	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> +
> +	mutex_lock(&cma->lock);
> +	bitmap_clear(cma->bitmap, bitmapno, nr_bits);
> +	mutex_unlock(&cma->lock);
> +}
> +
> +static int __init cma_activate_area(struct cma *cma)
> +{
> +	int bitmap_maxno = cma_bitmap_maxno(cma);
> +	int bitmap_size = BITS_TO_LONGS(bitmap_maxno) * sizeof(long);
> +	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
> +	unsigned i = cma->count >> pageblock_order;
> +	struct zone *zone;
> +
> +	pr_debug("%s()\n", __func__);
> +
> +	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> +	if (!cma->bitmap)
> +		return -ENOMEM;
> +
> +	WARN_ON_ONCE(!pfn_valid(pfn));
> +	zone = page_zone(pfn_to_page(pfn));
> +
> +	do {
> +		unsigned j;
> +
> +		base_pfn = pfn;
> +		for (j = pageblock_nr_pages; j; --j, pfn++) {
> +			WARN_ON_ONCE(!pfn_valid(pfn));
> +			/*
> +			 * alloc_contig_range requires the pfn range
> +			 * specified to be in the same zone. Make this
> +			 * simple by forcing the entire CMA resv range
> +			 * to be in the same zone.
> +			 */
> +			if (page_zone(pfn_to_page(pfn)) != zone)
> +				goto err;
> +		}
> +		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
> +	} while (--i);
> +
> +	mutex_init(&cma->lock);
> +	return 0;
> +
> +err:
> +	kfree(cma->bitmap);
> +	return -EINVAL;
> +}
> +
> +static int __init cma_init_reserved_areas(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < cma_area_count; i++) {
> +		int ret = cma_activate_area(&cma_areas[i]);
> +
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +core_initcall(cma_init_reserved_areas);
> +
> +/**
> + * cma_declare_contiguous() - reserve custom contiguous area
> + * @size: Size of the reserved area (in bytes),
> + * @base: Base address of the reserved area optional, use 0 for any
> + * @limit: End address of the reserved memory (optional, 0 for any).
> + * @alignment: Alignment for the contiguous memory area, should be power of 2
> + * @order_per_bit: Order of pages represented by one bit on bitmap.
> + * @res_cma: Pointer to store the created cma region.
> + * @fixed: hint about where to place the reserved area
> + *
> + * This function reserves memory from early allocator. It should be
> + * called by arch specific code once the early allocator (memblock or bootmem)
> + * has been activated and all other subsystems have already allocated/reserved
> + * memory. This function allows to create custom reserved areas.
> + *
> + * If @fixed is true, reserve contiguous area at exactly @base.  If false,
> + * reserve in range from @base to @limit.
> + */
> +int __init cma_declare_contiguous(phys_addr_t size,
> +				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment, int order_per_bit,
> +				struct cma **res_cma, bool fixed)
> +{
> +	struct cma *cma = &cma_areas[cma_area_count];
> +	int ret = 0;
> +
> +	pr_debug("%s(size %lx, base %08lx, limit %08lx alignment %08lx)\n",
> +		__func__, (unsigned long)size, (unsigned long)base,
> +		(unsigned long)limit, (unsigned long)alignment);
> +
> +	/* Sanity checks */
> +	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
> +		pr_err("%s(): Not enough slots for CMA reserved regions!\n",
> +			__func__);
> +		return -ENOSPC;
> +	}
> +
> +	if (!size)
> +		return -EINVAL;
> +
> +	if (alignment && !is_power_of_2(alignment))
> +		return -EINVAL;
> +
> +	/*
> +	 * Sanitise input arguments.
> +	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
> +	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
> +	 * and CMA property will be broken.
> +	 */
> +	alignment = max(alignment,
> +		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
> +	base = ALIGN(base, alignment);
> +	size = ALIGN(size, alignment);
> +	limit &= ~(alignment - 1);
> +	/* size should be aligned with order_per_bit */
> +	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit));
> +
> +	/* Reserve memory */
> +	if (base && fixed) {
> +		if (memblock_is_region_reserved(base, size) ||
> +		    memblock_reserve(base, size) < 0) {
> +			ret = -EBUSY;
> +			goto err;
> +		}
> +	} else {
> +		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
> +							limit);
> +		if (!addr) {
> +			ret = -ENOMEM;
> +			goto err;
> +		} else {
> +			base = addr;
> +		}
> +	}
> +
> +	/*
> +	 * Each reserved area must be initialised later, when more kernel
> +	 * subsystems (like slab allocator) are available.
> +	 */
> +	cma->base_pfn = PFN_DOWN(base);
> +	cma->count = size >> PAGE_SHIFT;
> +	cma->order_per_bit = order_per_bit;
> +	*res_cma = cma;
> +	cma_area_count++;
> +
> +	pr_info("%s(): reserved %ld MiB at %08lx\n",
> +		__func__, (unsigned long)size / SZ_1M, (unsigned long)base);
> +	return 0;
> +
> +err:
> +	pr_err("%s(): failed to reserve %ld MiB\n",
> +		__func__, (unsigned long)size / SZ_1M);
> +	return ret;
> +}
> +
> +/**
> + * cma_alloc() - allocate pages from contiguous area
> + * @cma:   Contiguous memory region for which the allocation is performed.
> + * @count: Requested number of pages.
> + * @align: Requested alignment of pages (in PAGE_SIZE order).
> + *
> + * This function allocates part of contiguous memory on specific
> + * contiguous memory area.
> + */
> +struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
> +{
> +	unsigned long mask, pfn, start = 0;
> +	unsigned long bitmap_maxno, bitmapno, nr_bits;
> +	struct page *page = NULL;
> +	int ret;
> +
> +	if (!cma || !cma->count)
> +		return NULL;
> +
> +	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
> +		 count, align);
> +
> +	if (!count)
> +		return NULL;
> +
> +	mask = cma_bitmap_aligned_mask(cma, align);
> +	bitmap_maxno = cma_bitmap_maxno(cma);
> +	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> +
> +	for (;;) {
> +		mutex_lock(&cma->lock);
> +		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
> +					bitmap_maxno, start, nr_bits, mask);
> +		if (bitmapno >= bitmap_maxno) {
> +			mutex_unlock(&cma->lock);
> +			break;
> +		}
> +		bitmap_set(cma->bitmap, bitmapno, nr_bits);
> +		/*
> +		 * It's safe to drop the lock here. We've marked this region for
> +		 * our exclusive use. If the migration fails we will take the
> +		 * lock again and unmark it.
> +		 */
> +		mutex_unlock(&cma->lock);
> +
> +		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
> +		mutex_lock(&cma_mutex);
> +		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
> +		mutex_unlock(&cma_mutex);
> +		if (ret == 0) {
> +			page = pfn_to_page(pfn);
> +			break;
> +		} else if (ret != -EBUSY) {
> +			clear_cma_bitmap(cma, pfn, count);
> +			break;
> +		}
> +		clear_cma_bitmap(cma, pfn, count);
> +		pr_debug("%s(): memory range at %p is busy, retrying\n",
> +			 __func__, pfn_to_page(pfn));
> +		/* try again with a bit different memory target */
> +		start = bitmapno + mask + 1;
> +	}
> +
> +	pr_debug("%s(): returned %p\n", __func__, page);
> +	return page;
> +}
> +
> +/**
> + * cma_release() - release allocated pages
> + * @cma:   Contiguous memory region for which the allocation is performed.
> + * @pages: Allocated pages.
> + * @count: Number of allocated pages.
> + *
> + * This function releases memory allocated by alloc_cma().
> + * It returns false when provided pages do not belong to contiguous area and
> + * true otherwise.
> + */
> +bool cma_release(struct cma *cma, struct page *pages, int count)
> +{
> +	unsigned long pfn;
> +
> +	if (!cma || !pages)
> +		return false;
> +
> +	pr_debug("%s(page %p)\n", __func__, (void *)pages);
> +
> +	pfn = page_to_pfn(pages);
> +
> +	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> +		return false;
> +
> +	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
> +
> +	free_contig_range(pfn, count);
> +	clear_cma_bitmap(cma, pfn, count);
> +
> +	return true;
> +}
> -- 
> 1.7.9.5
Joonsoo Kim - June 12, 2014, 7:42 a.m.
On Thu, Jun 12, 2014 at 04:13:11PM +0900, Minchan Kim wrote:
> On Thu, Jun 12, 2014 at 12:21:43PM +0900, Joonsoo Kim wrote:
> > Currently, there are two users on CMA functionality, one is the DMA
> > subsystem and the other is the kvm on powerpc. They have their own code
> > to manage CMA reserved area even if they looks really similar.
> > >From my guess, it is caused by some needs on bitmap management. Kvm side
> > wants to maintain bitmap not for 1 page, but for more size. Eventually it
> > use bitmap where one bit represents 64 pages.
> > 
> > When I implement CMA related patches, I should change those two places
> > to apply my change and it seem to be painful to me. I want to change
> > this situation and reduce future code management overhead through
> > this patch.
> > 
> > This change could also help developer who want to use CMA in their
> > new feature development, since they can use CMA easily without
> > copying & pasting this reserved area management code.
> > 
> > In previous patches, we have prepared some features to generalize
> > CMA reserved area management and now it's time to do it. This patch
> > moves core functions to mm/cma.c and change DMA APIs to use
> > these functions.
> > 
> > There is no functional change in DMA APIs.
> > 
> > v2: There is no big change from v1 in mm/cma.c. Mostly renaming.
> > 
> > Acked-by: Michal Nazarewicz <mina86@mina86.com>
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> 
> Acutally, I want to remove bool return of cma_release but it's not
> a out of scope in this patchset.
> 
> Acked-by: Minchan Kim <minchan@kernel.org>
> 
> > 
> > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> > index 00e13ce..4eac559 100644
> > --- a/drivers/base/Kconfig
> > +++ b/drivers/base/Kconfig
> > @@ -283,16 +283,6 @@ config CMA_ALIGNMENT
> >  
> >  	  If unsure, leave the default value "8".
> >  
> > -config CMA_AREAS
> > -	int "Maximum count of the CMA device-private areas"
> > -	default 7
> > -	help
> > -	  CMA allows to create CMA areas for particular devices. This parameter
> > -	  sets the maximum number of such device private CMA areas in the
> > -	  system.
> > -
> > -	  If unsure, leave the default value "7".
> > -
> >  endif
> >  
> >  endmenu
> > diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> > index 9bc9340..f177f73 100644
> > --- a/drivers/base/dma-contiguous.c
> > +++ b/drivers/base/dma-contiguous.c
> > @@ -24,25 +24,10 @@
> >  
> >  #include <linux/memblock.h>
> >  #include <linux/err.h>
> > -#include <linux/mm.h>
> > -#include <linux/mutex.h>
> > -#include <linux/page-isolation.h>
> >  #include <linux/sizes.h>
> > -#include <linux/slab.h>
> > -#include <linux/swap.h>
> > -#include <linux/mm_types.h>
> >  #include <linux/dma-contiguous.h>
> >  #include <linux/log2.h>
> 
> Should we remain log2.h in here?
> 

We should remove it. I will fix it.

Thanks.

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Zhang Yanfei - June 12, 2014, 8:29 a.m.
On 06/12/2014 11:21 AM, Joonsoo Kim wrote:
> Currently, there are two users on CMA functionality, one is the DMA
> subsystem and the other is the kvm on powerpc. They have their own code
> to manage CMA reserved area even if they looks really similar.
>>From my guess, it is caused by some needs on bitmap management. Kvm side
> wants to maintain bitmap not for 1 page, but for more size. Eventually it
> use bitmap where one bit represents 64 pages.
> 
> When I implement CMA related patches, I should change those two places
> to apply my change and it seem to be painful to me. I want to change
> this situation and reduce future code management overhead through
> this patch.
> 
> This change could also help developer who want to use CMA in their
> new feature development, since they can use CMA easily without
> copying & pasting this reserved area management code.
> 
> In previous patches, we have prepared some features to generalize
> CMA reserved area management and now it's time to do it. This patch
> moves core functions to mm/cma.c and change DMA APIs to use
> these functions.
> 
> There is no functional change in DMA APIs.
> 
> v2: There is no big change from v1 in mm/cma.c. Mostly renaming.
> 
> Acked-by: Michal Nazarewicz <mina86@mina86.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Acked-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>

> 
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index 00e13ce..4eac559 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -283,16 +283,6 @@ config CMA_ALIGNMENT
>  
>  	  If unsure, leave the default value "8".
>  
> -config CMA_AREAS
> -	int "Maximum count of the CMA device-private areas"
> -	default 7
> -	help
> -	  CMA allows to create CMA areas for particular devices. This parameter
> -	  sets the maximum number of such device private CMA areas in the
> -	  system.
> -
> -	  If unsure, leave the default value "7".
> -
>  endif
>  
>  endmenu
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index 9bc9340..f177f73 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -24,25 +24,10 @@
>  
>  #include <linux/memblock.h>
>  #include <linux/err.h>
> -#include <linux/mm.h>
> -#include <linux/mutex.h>
> -#include <linux/page-isolation.h>
>  #include <linux/sizes.h>
> -#include <linux/slab.h>
> -#include <linux/swap.h>
> -#include <linux/mm_types.h>
>  #include <linux/dma-contiguous.h>
>  #include <linux/log2.h>
> -
> -struct cma {
> -	unsigned long	base_pfn;
> -	unsigned long	count;
> -	unsigned long	*bitmap;
> -	int order_per_bit; /* Order of pages represented by one bit */
> -	struct mutex	lock;
> -};
> -
> -struct cma *dma_contiguous_default_area;
> +#include <linux/cma.h>
>  
>  #ifdef CONFIG_CMA_SIZE_MBYTES
>  #define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES
> @@ -50,6 +35,8 @@ struct cma *dma_contiguous_default_area;
>  #define CMA_SIZE_MBYTES 0
>  #endif
>  
> +struct cma *dma_contiguous_default_area;
> +
>  /*
>   * Default global CMA area size can be defined in kernel's .config.
>   * This is useful mainly for distro maintainers to create a kernel
> @@ -156,199 +143,13 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
>  	}
>  }
>  
> -static DEFINE_MUTEX(cma_mutex);
> -
> -static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> -{
> -	return (1 << (align_order >> cma->order_per_bit)) - 1;
> -}
> -
> -static unsigned long cma_bitmap_maxno(struct cma *cma)
> -{
> -	return cma->count >> cma->order_per_bit;
> -}
> -
> -static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
> -						unsigned long pages)
> -{
> -	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
> -}
> -
> -static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
> -{
> -	unsigned long bitmapno, nr_bits;
> -
> -	bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
> -	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> -
> -	mutex_lock(&cma->lock);
> -	bitmap_clear(cma->bitmap, bitmapno, nr_bits);
> -	mutex_unlock(&cma->lock);
> -}
> -
> -static int __init cma_activate_area(struct cma *cma)
> -{
> -	int bitmap_maxno = cma_bitmap_maxno(cma);
> -	int bitmap_size = BITS_TO_LONGS(bitmap_maxno) * sizeof(long);
> -	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
> -	unsigned i = cma->count >> pageblock_order;
> -	struct zone *zone;
> -
> -	pr_debug("%s()\n", __func__);
> -
> -	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> -	if (!cma->bitmap)
> -		return -ENOMEM;
> -
> -	WARN_ON_ONCE(!pfn_valid(pfn));
> -	zone = page_zone(pfn_to_page(pfn));
> -
> -	do {
> -		unsigned j;
> -		base_pfn = pfn;
> -		for (j = pageblock_nr_pages; j; --j, pfn++) {
> -			WARN_ON_ONCE(!pfn_valid(pfn));
> -			/*
> -			 * alloc_contig_range requires the pfn range
> -			 * specified to be in the same zone. Make this
> -			 * simple by forcing the entire CMA resv range
> -			 * to be in the same zone.
> -			 */
> -			if (page_zone(pfn_to_page(pfn)) != zone)
> -				goto err;
> -		}
> -		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
> -	} while (--i);
> -
> -	mutex_init(&cma->lock);
> -	return 0;
> -
> -err:
> -	kfree(cma->bitmap);
> -	return -EINVAL;
> -}
> -
> -static struct cma cma_areas[MAX_CMA_AREAS];
> -static unsigned cma_area_count;
> -
> -static int __init cma_init_reserved_areas(void)
> -{
> -	int i;
> -
> -	for (i = 0; i < cma_area_count; i++) {
> -		int ret = cma_activate_area(&cma_areas[i]);
> -		if (ret)
> -			return ret;
> -	}
> -
> -	return 0;
> -}
> -core_initcall(cma_init_reserved_areas);
> -
> -/**
> - * dma_contiguous_reserve_area() - reserve custom contiguous area
> - * @size: Size of the reserved area (in bytes),
> - * @base: Base address of the reserved area optional, use 0 for any
> - * @limit: End address of the reserved memory (optional, 0 for any).
> - * @alignment: Alignment for the contiguous memory area, should be power of 2
> - * @order_per_bit: Order of pages represented by one bit on bitmap.
> - * @res_cma: Pointer to store the created cma region.
> - * @fixed: hint about where to place the reserved area
> - *
> - * This function reserves memory from early allocator. It should be
> - * called by arch specific code once the early allocator (memblock or bootmem)
> - * has been activated and all other subsystems have already allocated/reserved
> - * memory. This function allows to create custom reserved areas for specific
> - * devices.
> - *
> - * If @fixed is true, reserve contiguous area at exactly @base.  If false,
> - * reserve in range from @base to @limit.
> - */
> -static int __init __dma_contiguous_reserve_area(phys_addr_t size,
> -				phys_addr_t base, phys_addr_t limit,
> -				phys_addr_t alignment, int order_per_bit,
> -				struct cma **res_cma, bool fixed)
> -{
> -	struct cma *cma = &cma_areas[cma_area_count];
> -	int ret = 0;
> -
> -	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> -		__func__, (unsigned long)size, (unsigned long)base,
> -		(unsigned long)limit, (unsigned long)alignment);
> -
> -	/* Sanity checks */
> -	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
> -		pr_err("%s(): Not enough slots for CMA reserved regions!\n",
> -			__func__);
> -		return -ENOSPC;
> -	}
> -
> -	if (!size)
> -		return -EINVAL;
> -
> -	if (alignment && !is_power_of_2(alignment))
> -		return -EINVAL;
> -
> -	/*
> -	 * Sanitise input arguments.
> -	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
> -	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
> -	 * and CMA property will be broken.
> -	 */
> -	alignment = max(alignment,
> -		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
> -	base = ALIGN(base, alignment);
> -	size = ALIGN(size, alignment);
> -	limit &= ~(alignment - 1);
> -	/* size should be aligned with order_per_bit */
> -	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit));
> -
> -	/* Reserve memory */
> -	if (base && fixed) {
> -		if (memblock_is_region_reserved(base, size) ||
> -		    memblock_reserve(base, size) < 0) {
> -			ret = -EBUSY;
> -			goto err;
> -		}
> -	} else {
> -		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
> -							limit);
> -		if (!addr) {
> -			ret = -ENOMEM;
> -			goto err;
> -		} else {
> -			base = addr;
> -		}
> -	}
> -
> -	/*
> -	 * Each reserved area must be initialised later, when more kernel
> -	 * subsystems (like slab allocator) are available.
> -	 */
> -	cma->base_pfn = PFN_DOWN(base);
> -	cma->count = size >> PAGE_SHIFT;
> -	cma->order_per_bit = order_per_bit;
> -	*res_cma = cma;
> -	cma_area_count++;
> -
> -	pr_info("%s(): reserved %ld MiB at %08lx\n",
> -		__func__, (unsigned long)size / SZ_1M, (unsigned long)base);
> -	return 0;
> -
> -err:
> -	pr_err("%s(): failed to reserve %ld MiB\n",
> -		__func__, (unsigned long)size / SZ_1M);
> -	return ret;
> -}
> -
>  int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  				       phys_addr_t limit, struct cma **res_cma,
>  				       bool fixed)
>  {
>  	int ret;
>  
> -	ret = __dma_contiguous_reserve_area(size, base, limit, 0, 0,
> -						res_cma, fixed);
> +	ret = cma_declare_contiguous(size, base, limit, 0, 0, res_cma, fixed);
>  	if (ret)
>  		return ret;
>  
> @@ -358,124 +159,17 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  	return 0;
>  }
>  
> -/**
> - * dma_alloc_from_contiguous() - allocate pages from contiguous area
> - * @dev:   Pointer to device for which the allocation is performed.
> - * @count: Requested number of pages.
> - * @align: Requested alignment of pages (in PAGE_SIZE order).
> - *
> - * This function allocates memory buffer for specified device. It uses
> - * device specific contiguous memory area if available or the default
> - * global one. Requires architecture specific dev_get_cma_area() helper
> - * function.
> - */
> -static struct page *__dma_alloc_from_contiguous(struct cma *cma, int count,
> -				       unsigned int align)
> -{
> -	unsigned long mask, pfn, start = 0;
> -	unsigned long bitmap_maxno, bitmapno, nr_bits;
> -	struct page *page = NULL;
> -	int ret;
> -
> -	if (!cma || !cma->count)
> -		return NULL;
> -
> -	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
> -		 count, align);
> -
> -	if (!count)
> -		return NULL;
> -
> -	mask = cma_bitmap_aligned_mask(cma, align);
> -	bitmap_maxno = cma_bitmap_maxno(cma);
> -	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> -
> -	for (;;) {
> -		mutex_lock(&cma->lock);
> -		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
> -					bitmap_maxno, start, nr_bits, mask);
> -		if (bitmapno >= bitmap_maxno) {
> -			mutex_unlock(&cma->lock);
> -			break;
> -		}
> -		bitmap_set(cma->bitmap, bitmapno, nr_bits);
> -		/*
> -		 * It's safe to drop the lock here. We've marked this region for
> -		 * our exclusive use. If the migration fails we will take the
> -		 * lock again and unmark it.
> -		 */
> -		mutex_unlock(&cma->lock);
> -
> -		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
> -		mutex_lock(&cma_mutex);
> -		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
> -		mutex_unlock(&cma_mutex);
> -		if (ret == 0) {
> -			page = pfn_to_page(pfn);
> -			break;
> -		} else if (ret != -EBUSY) {
> -			clear_cma_bitmap(cma, pfn, count);
> -			break;
> -		}
> -		clear_cma_bitmap(cma, pfn, count);
> -		pr_debug("%s(): memory range at %p is busy, retrying\n",
> -			 __func__, pfn_to_page(pfn));
> -		/* try again with a bit different memory target */
> -		start = bitmapno + mask + 1;
> -	}
> -
> -	pr_debug("%s(): returned %p\n", __func__, page);
> -	return page;
> -}
> -
>  struct page *dma_alloc_from_contiguous(struct device *dev, int count,
>  				       unsigned int align)
>  {
> -	struct cma *cma = dev_get_cma_area(dev);
> -
>  	if (align > CONFIG_CMA_ALIGNMENT)
>  		align = CONFIG_CMA_ALIGNMENT;
>  
> -	return __dma_alloc_from_contiguous(cma, count, align);
> -}
> -
> -/**
> - * dma_release_from_contiguous() - release allocated pages
> - * @dev:   Pointer to device for which the pages were allocated.
> - * @pages: Allocated pages.
> - * @count: Number of allocated pages.
> - *
> - * This function releases memory allocated by dma_alloc_from_contiguous().
> - * It returns false when provided pages do not belong to contiguous area and
> - * true otherwise.
> - */
> -static bool __dma_release_from_contiguous(struct cma *cma, struct page *pages,
> -				 int count)
> -{
> -	unsigned long pfn;
> -
> -	if (!cma || !pages)
> -		return false;
> -
> -	pr_debug("%s(page %p)\n", __func__, (void *)pages);
> -
> -	pfn = page_to_pfn(pages);
> -
> -	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> -		return false;
> -
> -	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
> -
> -	free_contig_range(pfn, count);
> -	clear_cma_bitmap(cma, pfn, count);
> -
> -	return true;
> +	return cma_alloc(dev_get_cma_area(dev), count, align);
>  }
>  
>  bool dma_release_from_contiguous(struct device *dev, struct page *pages,
>  				 int count)
>  {
> -	struct cma *cma = dev_get_cma_area(dev);
> -
> -	return __dma_release_from_contiguous(cma, pages, count);
> +	return cma_release(dev_get_cma_area(dev), pages, count);
>  }
> diff --git a/include/linux/cma.h b/include/linux/cma.h
> new file mode 100644
> index 0000000..e38efe9
> --- /dev/null
> +++ b/include/linux/cma.h
> @@ -0,0 +1,12 @@
> +#ifndef __CMA_H__
> +#define __CMA_H__
> +
> +struct cma;
> +
> +extern int __init cma_declare_contiguous(phys_addr_t size,
> +				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment, int order_per_bit,
> +				struct cma **res_cma, bool fixed);
> +extern struct page *cma_alloc(struct cma *cma, int count, unsigned int align);
> +extern bool cma_release(struct cma *cma, struct page *pages, int count);
> +#endif
> diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h
> index 772eab5..a40c1f3 100644
> --- a/include/linux/dma-contiguous.h
> +++ b/include/linux/dma-contiguous.h
> @@ -53,9 +53,10 @@
>  
>  #ifdef __KERNEL__
>  
> +#include <linux/device.h>
> +
>  struct cma;
>  struct page;
> -struct device;
>  
>  #ifdef CONFIG_DMA_CMA
>  
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 3e9977a..f4899ec 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -508,6 +508,17 @@ config CMA_DEBUG
>  	  processing calls such as dma_alloc_from_contiguous().
>  	  This option does not affect warning and error messages.
>  
> +config CMA_AREAS
> +	int "Maximum count of the CMA areas"
> +	depends on CMA
> +	default 7
> +	help
> +	  CMA allows to create CMA areas for particular purpose, mainly,
> +	  used as device private area. This parameter sets the maximum
> +	  number of CMA area in the system.
> +
> +	  If unsure, leave the default value "7".
> +
>  config ZBUD
>  	tristate
>  	default n
> diff --git a/mm/Makefile b/mm/Makefile
> index 1eaa70b..bc0422b 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -62,3 +62,4 @@ obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
>  obj-$(CONFIG_ZBUD)	+= zbud.o
>  obj-$(CONFIG_ZSMALLOC)	+= zsmalloc.o
>  obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
> +obj-$(CONFIG_CMA)	+= cma.o
> diff --git a/mm/cma.c b/mm/cma.c
> new file mode 100644
> index 0000000..1e1b017
> --- /dev/null
> +++ b/mm/cma.c
> @@ -0,0 +1,330 @@
> +/*
> + * Contiguous Memory Allocator
> + *
> + * Copyright (c) 2010-2011 by Samsung Electronics.
> + * Copyright IBM Corporation, 2013
> + * Copyright LG Electronics Inc., 2014
> + * Written by:
> + *	Marek Szyprowski <m.szyprowski@samsung.com>
> + *	Michal Nazarewicz <mina86@mina86.com>
> + *	Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> + *	Joonsoo Kim <iamjoonsoo.kim@lge.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation; either version 2 of the
> + * License or (at your optional) any later version of the license.
> + */
> +
> +#define pr_fmt(fmt) "cma: " fmt
> +
> +#ifdef CONFIG_CMA_DEBUG
> +#ifndef DEBUG
> +#  define DEBUG
> +#endif
> +#endif
> +
> +#include <linux/memblock.h>
> +#include <linux/err.h>
> +#include <linux/mm.h>
> +#include <linux/mutex.h>
> +#include <linux/sizes.h>
> +#include <linux/slab.h>
> +
> +struct cma {
> +	unsigned long	base_pfn;
> +	unsigned long	count;
> +	unsigned long	*bitmap;
> +	int order_per_bit; /* Order of pages represented by one bit */
> +	struct mutex	lock;
> +};
> +
> +/*
> + * There is always at least global CMA area and a few optional
> + * areas configured in kernel .config.
> + */
> +#define MAX_CMA_AREAS	(1 + CONFIG_CMA_AREAS)
> +
> +static struct cma cma_areas[MAX_CMA_AREAS];
> +static unsigned cma_area_count;
> +static DEFINE_MUTEX(cma_mutex);
> +
> +static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> +{
> +	return (1 << (align_order >> cma->order_per_bit)) - 1;
> +}
> +
> +static unsigned long cma_bitmap_maxno(struct cma *cma)
> +{
> +	return cma->count >> cma->order_per_bit;
> +}
> +
> +static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
> +						unsigned long pages)
> +{
> +	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
> +}
> +
> +static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
> +{
> +	unsigned long bitmapno, nr_bits;
> +
> +	bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
> +	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> +
> +	mutex_lock(&cma->lock);
> +	bitmap_clear(cma->bitmap, bitmapno, nr_bits);
> +	mutex_unlock(&cma->lock);
> +}
> +
> +static int __init cma_activate_area(struct cma *cma)
> +{
> +	int bitmap_maxno = cma_bitmap_maxno(cma);
> +	int bitmap_size = BITS_TO_LONGS(bitmap_maxno) * sizeof(long);
> +	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
> +	unsigned i = cma->count >> pageblock_order;
> +	struct zone *zone;
> +
> +	pr_debug("%s()\n", __func__);
> +
> +	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> +	if (!cma->bitmap)
> +		return -ENOMEM;
> +
> +	WARN_ON_ONCE(!pfn_valid(pfn));
> +	zone = page_zone(pfn_to_page(pfn));
> +
> +	do {
> +		unsigned j;
> +
> +		base_pfn = pfn;
> +		for (j = pageblock_nr_pages; j; --j, pfn++) {
> +			WARN_ON_ONCE(!pfn_valid(pfn));
> +			/*
> +			 * alloc_contig_range requires the pfn range
> +			 * specified to be in the same zone. Make this
> +			 * simple by forcing the entire CMA resv range
> +			 * to be in the same zone.
> +			 */
> +			if (page_zone(pfn_to_page(pfn)) != zone)
> +				goto err;
> +		}
> +		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
> +	} while (--i);
> +
> +	mutex_init(&cma->lock);
> +	return 0;
> +
> +err:
> +	kfree(cma->bitmap);
> +	return -EINVAL;
> +}
> +
> +static int __init cma_init_reserved_areas(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < cma_area_count; i++) {
> +		int ret = cma_activate_area(&cma_areas[i]);
> +
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +core_initcall(cma_init_reserved_areas);
> +
> +/**
> + * cma_declare_contiguous() - reserve custom contiguous area
> + * @size: Size of the reserved area (in bytes),
> + * @base: Base address of the reserved area optional, use 0 for any
> + * @limit: End address of the reserved memory (optional, 0 for any).
> + * @alignment: Alignment for the contiguous memory area, should be power of 2
> + * @order_per_bit: Order of pages represented by one bit on bitmap.
> + * @res_cma: Pointer to store the created cma region.
> + * @fixed: hint about where to place the reserved area
> + *
> + * This function reserves memory from early allocator. It should be
> + * called by arch specific code once the early allocator (memblock or bootmem)
> + * has been activated and all other subsystems have already allocated/reserved
> + * memory. This function allows to create custom reserved areas.
> + *
> + * If @fixed is true, reserve contiguous area at exactly @base.  If false,
> + * reserve in range from @base to @limit.
> + */
> +int __init cma_declare_contiguous(phys_addr_t size,
> +				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment, int order_per_bit,
> +				struct cma **res_cma, bool fixed)
> +{
> +	struct cma *cma = &cma_areas[cma_area_count];
> +	int ret = 0;
> +
> +	pr_debug("%s(size %lx, base %08lx, limit %08lx alignment %08lx)\n",
> +		__func__, (unsigned long)size, (unsigned long)base,
> +		(unsigned long)limit, (unsigned long)alignment);
> +
> +	/* Sanity checks */
> +	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
> +		pr_err("%s(): Not enough slots for CMA reserved regions!\n",
> +			__func__);
> +		return -ENOSPC;
> +	}
> +
> +	if (!size)
> +		return -EINVAL;
> +
> +	if (alignment && !is_power_of_2(alignment))
> +		return -EINVAL;
> +
> +	/*
> +	 * Sanitise input arguments.
> +	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
> +	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
> +	 * and CMA property will be broken.
> +	 */
> +	alignment = max(alignment,
> +		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
> +	base = ALIGN(base, alignment);
> +	size = ALIGN(size, alignment);
> +	limit &= ~(alignment - 1);
> +	/* size should be aligned with order_per_bit */
> +	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit));
> +
> +	/* Reserve memory */
> +	if (base && fixed) {
> +		if (memblock_is_region_reserved(base, size) ||
> +		    memblock_reserve(base, size) < 0) {
> +			ret = -EBUSY;
> +			goto err;
> +		}
> +	} else {
> +		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
> +							limit);
> +		if (!addr) {
> +			ret = -ENOMEM;
> +			goto err;
> +		} else {
> +			base = addr;
> +		}
> +	}
> +
> +	/*
> +	 * Each reserved area must be initialised later, when more kernel
> +	 * subsystems (like slab allocator) are available.
> +	 */
> +	cma->base_pfn = PFN_DOWN(base);
> +	cma->count = size >> PAGE_SHIFT;
> +	cma->order_per_bit = order_per_bit;
> +	*res_cma = cma;
> +	cma_area_count++;
> +
> +	pr_info("%s(): reserved %ld MiB at %08lx\n",
> +		__func__, (unsigned long)size / SZ_1M, (unsigned long)base);
> +	return 0;
> +
> +err:
> +	pr_err("%s(): failed to reserve %ld MiB\n",
> +		__func__, (unsigned long)size / SZ_1M);
> +	return ret;
> +}
> +
> +/**
> + * cma_alloc() - allocate pages from contiguous area
> + * @cma:   Contiguous memory region for which the allocation is performed.
> + * @count: Requested number of pages.
> + * @align: Requested alignment of pages (in PAGE_SIZE order).
> + *
> + * This function allocates part of contiguous memory on specific
> + * contiguous memory area.
> + */
> +struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
> +{
> +	unsigned long mask, pfn, start = 0;
> +	unsigned long bitmap_maxno, bitmapno, nr_bits;
> +	struct page *page = NULL;
> +	int ret;
> +
> +	if (!cma || !cma->count)
> +		return NULL;
> +
> +	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
> +		 count, align);
> +
> +	if (!count)
> +		return NULL;
> +
> +	mask = cma_bitmap_aligned_mask(cma, align);
> +	bitmap_maxno = cma_bitmap_maxno(cma);
> +	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> +
> +	for (;;) {
> +		mutex_lock(&cma->lock);
> +		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
> +					bitmap_maxno, start, nr_bits, mask);
> +		if (bitmapno >= bitmap_maxno) {
> +			mutex_unlock(&cma->lock);
> +			break;
> +		}
> +		bitmap_set(cma->bitmap, bitmapno, nr_bits);
> +		/*
> +		 * It's safe to drop the lock here. We've marked this region for
> +		 * our exclusive use. If the migration fails we will take the
> +		 * lock again and unmark it.
> +		 */
> +		mutex_unlock(&cma->lock);
> +
> +		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
> +		mutex_lock(&cma_mutex);
> +		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
> +		mutex_unlock(&cma_mutex);
> +		if (ret == 0) {
> +			page = pfn_to_page(pfn);
> +			break;
> +		} else if (ret != -EBUSY) {
> +			clear_cma_bitmap(cma, pfn, count);
> +			break;
> +		}
> +		clear_cma_bitmap(cma, pfn, count);
> +		pr_debug("%s(): memory range at %p is busy, retrying\n",
> +			 __func__, pfn_to_page(pfn));
> +		/* try again with a bit different memory target */
> +		start = bitmapno + mask + 1;
> +	}
> +
> +	pr_debug("%s(): returned %p\n", __func__, page);
> +	return page;
> +}
> +
> +/**
> + * cma_release() - release allocated pages
> + * @cma:   Contiguous memory region for which the allocation is performed.
> + * @pages: Allocated pages.
> + * @count: Number of allocated pages.
> + *
> + * This function releases memory allocated by alloc_cma().
> + * It returns false when provided pages do not belong to contiguous area and
> + * true otherwise.
> + */
> +bool cma_release(struct cma *cma, struct page *pages, int count)
> +{
> +	unsigned long pfn;
> +
> +	if (!cma || !pages)
> +		return false;
> +
> +	pr_debug("%s(page %p)\n", __func__, (void *)pages);
> +
> +	pfn = page_to_pfn(pages);
> +
> +	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> +		return false;
> +
> +	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
> +
> +	free_contig_range(pfn, count);
> +	clear_cma_bitmap(cma, pfn, count);
> +
> +	return true;
> +}
>
Aneesh Kumar K.V - June 14, 2014, 10:06 a.m.
Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:

> Currently, there are two users on CMA functionality, one is the DMA
> subsystem and the other is the kvm on powerpc. They have their own code
> to manage CMA reserved area even if they looks really similar.
> From my guess, it is caused by some needs on bitmap management. Kvm side
> wants to maintain bitmap not for 1 page, but for more size. Eventually it
> use bitmap where one bit represents 64 pages.
>
> When I implement CMA related patches, I should change those two places
> to apply my change and it seem to be painful to me. I want to change
> this situation and reduce future code management overhead through
> this patch.
>
> This change could also help developer who want to use CMA in their
> new feature development, since they can use CMA easily without
> copying & pasting this reserved area management code.
>
> In previous patches, we have prepared some features to generalize
> CMA reserved area management and now it's time to do it. This patch
> moves core functions to mm/cma.c and change DMA APIs to use
> these functions.
>
> There is no functional change in DMA APIs.
>
> v2: There is no big change from v1 in mm/cma.c. Mostly renaming.
>
> Acked-by: Michal Nazarewicz <mina86@mina86.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

>
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index 00e13ce..4eac559 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -283,16 +283,6 @@ config CMA_ALIGNMENT
>
>  	  If unsure, leave the default value "8".
>
> -config CMA_AREAS
> -	int "Maximum count of the CMA device-private areas"
> -	default 7
> -	help
> -	  CMA allows to create CMA areas for particular devices. This parameter
> -	  sets the maximum number of such device private CMA areas in the
> -	  system.
> -
> -	  If unsure, leave the default value "7".
> -
>  endif
>
>  endmenu
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index 9bc9340..f177f73 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -24,25 +24,10 @@
>
>  #include <linux/memblock.h>
>  #include <linux/err.h>
> -#include <linux/mm.h>
> -#include <linux/mutex.h>
> -#include <linux/page-isolation.h>
>  #include <linux/sizes.h>
> -#include <linux/slab.h>
> -#include <linux/swap.h>
> -#include <linux/mm_types.h>
>  #include <linux/dma-contiguous.h>
>  #include <linux/log2.h>
> -
> -struct cma {
> -	unsigned long	base_pfn;
> -	unsigned long	count;
> -	unsigned long	*bitmap;
> -	int order_per_bit; /* Order of pages represented by one bit */
> -	struct mutex	lock;
> -};
> -
> -struct cma *dma_contiguous_default_area;
> +#include <linux/cma.h>
>
>  #ifdef CONFIG_CMA_SIZE_MBYTES
>  #define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES
> @@ -50,6 +35,8 @@ struct cma *dma_contiguous_default_area;
>  #define CMA_SIZE_MBYTES 0
>  #endif
>
> +struct cma *dma_contiguous_default_area;
> +
>  /*
>   * Default global CMA area size can be defined in kernel's .config.
>   * This is useful mainly for distro maintainers to create a kernel
> @@ -156,199 +143,13 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
>  	}
>  }
>
> -static DEFINE_MUTEX(cma_mutex);
> -
> -static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> -{
> -	return (1 << (align_order >> cma->order_per_bit)) - 1;
> -}
> -
> -static unsigned long cma_bitmap_maxno(struct cma *cma)
> -{
> -	return cma->count >> cma->order_per_bit;
> -}
> -
> -static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
> -						unsigned long pages)
> -{
> -	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
> -}
> -
> -static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
> -{
> -	unsigned long bitmapno, nr_bits;
> -
> -	bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
> -	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> -
> -	mutex_lock(&cma->lock);
> -	bitmap_clear(cma->bitmap, bitmapno, nr_bits);
> -	mutex_unlock(&cma->lock);
> -}
> -
> -static int __init cma_activate_area(struct cma *cma)
> -{
> -	int bitmap_maxno = cma_bitmap_maxno(cma);
> -	int bitmap_size = BITS_TO_LONGS(bitmap_maxno) * sizeof(long);
> -	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
> -	unsigned i = cma->count >> pageblock_order;
> -	struct zone *zone;
> -
> -	pr_debug("%s()\n", __func__);
> -
> -	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> -	if (!cma->bitmap)
> -		return -ENOMEM;
> -
> -	WARN_ON_ONCE(!pfn_valid(pfn));
> -	zone = page_zone(pfn_to_page(pfn));
> -
> -	do {
> -		unsigned j;
> -		base_pfn = pfn;
> -		for (j = pageblock_nr_pages; j; --j, pfn++) {
> -			WARN_ON_ONCE(!pfn_valid(pfn));
> -			/*
> -			 * alloc_contig_range requires the pfn range
> -			 * specified to be in the same zone. Make this
> -			 * simple by forcing the entire CMA resv range
> -			 * to be in the same zone.
> -			 */
> -			if (page_zone(pfn_to_page(pfn)) != zone)
> -				goto err;
> -		}
> -		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
> -	} while (--i);
> -
> -	mutex_init(&cma->lock);
> -	return 0;
> -
> -err:
> -	kfree(cma->bitmap);
> -	return -EINVAL;
> -}
> -
> -static struct cma cma_areas[MAX_CMA_AREAS];
> -static unsigned cma_area_count;
> -
> -static int __init cma_init_reserved_areas(void)
> -{
> -	int i;
> -
> -	for (i = 0; i < cma_area_count; i++) {
> -		int ret = cma_activate_area(&cma_areas[i]);
> -		if (ret)
> -			return ret;
> -	}
> -
> -	return 0;
> -}
> -core_initcall(cma_init_reserved_areas);
> -
> -/**
> - * dma_contiguous_reserve_area() - reserve custom contiguous area
> - * @size: Size of the reserved area (in bytes),
> - * @base: Base address of the reserved area optional, use 0 for any
> - * @limit: End address of the reserved memory (optional, 0 for any).
> - * @alignment: Alignment for the contiguous memory area, should be power of 2
> - * @order_per_bit: Order of pages represented by one bit on bitmap.
> - * @res_cma: Pointer to store the created cma region.
> - * @fixed: hint about where to place the reserved area
> - *
> - * This function reserves memory from early allocator. It should be
> - * called by arch specific code once the early allocator (memblock or bootmem)
> - * has been activated and all other subsystems have already allocated/reserved
> - * memory. This function allows to create custom reserved areas for specific
> - * devices.
> - *
> - * If @fixed is true, reserve contiguous area at exactly @base.  If false,
> - * reserve in range from @base to @limit.
> - */
> -static int __init __dma_contiguous_reserve_area(phys_addr_t size,
> -				phys_addr_t base, phys_addr_t limit,
> -				phys_addr_t alignment, int order_per_bit,
> -				struct cma **res_cma, bool fixed)
> -{
> -	struct cma *cma = &cma_areas[cma_area_count];
> -	int ret = 0;
> -
> -	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> -		__func__, (unsigned long)size, (unsigned long)base,
> -		(unsigned long)limit, (unsigned long)alignment);
> -
> -	/* Sanity checks */
> -	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
> -		pr_err("%s(): Not enough slots for CMA reserved regions!\n",
> -			__func__);
> -		return -ENOSPC;
> -	}
> -
> -	if (!size)
> -		return -EINVAL;
> -
> -	if (alignment && !is_power_of_2(alignment))
> -		return -EINVAL;
> -
> -	/*
> -	 * Sanitise input arguments.
> -	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
> -	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
> -	 * and CMA property will be broken.
> -	 */
> -	alignment = max(alignment,
> -		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
> -	base = ALIGN(base, alignment);
> -	size = ALIGN(size, alignment);
> -	limit &= ~(alignment - 1);
> -	/* size should be aligned with order_per_bit */
> -	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit));
> -
> -	/* Reserve memory */
> -	if (base && fixed) {
> -		if (memblock_is_region_reserved(base, size) ||
> -		    memblock_reserve(base, size) < 0) {
> -			ret = -EBUSY;
> -			goto err;
> -		}
> -	} else {
> -		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
> -							limit);
> -		if (!addr) {
> -			ret = -ENOMEM;
> -			goto err;
> -		} else {
> -			base = addr;
> -		}
> -	}
> -
> -	/*
> -	 * Each reserved area must be initialised later, when more kernel
> -	 * subsystems (like slab allocator) are available.
> -	 */
> -	cma->base_pfn = PFN_DOWN(base);
> -	cma->count = size >> PAGE_SHIFT;
> -	cma->order_per_bit = order_per_bit;
> -	*res_cma = cma;
> -	cma_area_count++;
> -
> -	pr_info("%s(): reserved %ld MiB at %08lx\n",
> -		__func__, (unsigned long)size / SZ_1M, (unsigned long)base);
> -	return 0;
> -
> -err:
> -	pr_err("%s(): failed to reserve %ld MiB\n",
> -		__func__, (unsigned long)size / SZ_1M);
> -	return ret;
> -}
> -
>  int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  				       phys_addr_t limit, struct cma **res_cma,
>  				       bool fixed)
>  {
>  	int ret;
>
> -	ret = __dma_contiguous_reserve_area(size, base, limit, 0, 0,
> -						res_cma, fixed);
> +	ret = cma_declare_contiguous(size, base, limit, 0, 0, res_cma, fixed);
>  	if (ret)
>  		return ret;
>
> @@ -358,124 +159,17 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  	return 0;
>  }
>
> -/**
> - * dma_alloc_from_contiguous() - allocate pages from contiguous area
> - * @dev:   Pointer to device for which the allocation is performed.
> - * @count: Requested number of pages.
> - * @align: Requested alignment of pages (in PAGE_SIZE order).
> - *
> - * This function allocates memory buffer for specified device. It uses
> - * device specific contiguous memory area if available or the default
> - * global one. Requires architecture specific dev_get_cma_area() helper
> - * function.
> - */
> -static struct page *__dma_alloc_from_contiguous(struct cma *cma, int count,
> -				       unsigned int align)
> -{
> -	unsigned long mask, pfn, start = 0;
> -	unsigned long bitmap_maxno, bitmapno, nr_bits;
> -	struct page *page = NULL;
> -	int ret;
> -
> -	if (!cma || !cma->count)
> -		return NULL;
> -
> -	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
> -		 count, align);
> -
> -	if (!count)
> -		return NULL;
> -
> -	mask = cma_bitmap_aligned_mask(cma, align);
> -	bitmap_maxno = cma_bitmap_maxno(cma);
> -	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> -
> -	for (;;) {
> -		mutex_lock(&cma->lock);
> -		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
> -					bitmap_maxno, start, nr_bits, mask);
> -		if (bitmapno >= bitmap_maxno) {
> -			mutex_unlock(&cma->lock);
> -			break;
> -		}
> -		bitmap_set(cma->bitmap, bitmapno, nr_bits);
> -		/*
> -		 * It's safe to drop the lock here. We've marked this region for
> -		 * our exclusive use. If the migration fails we will take the
> -		 * lock again and unmark it.
> -		 */
> -		mutex_unlock(&cma->lock);
> -
> -		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
> -		mutex_lock(&cma_mutex);
> -		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
> -		mutex_unlock(&cma_mutex);
> -		if (ret == 0) {
> -			page = pfn_to_page(pfn);
> -			break;
> -		} else if (ret != -EBUSY) {
> -			clear_cma_bitmap(cma, pfn, count);
> -			break;
> -		}
> -		clear_cma_bitmap(cma, pfn, count);
> -		pr_debug("%s(): memory range at %p is busy, retrying\n",
> -			 __func__, pfn_to_page(pfn));
> -		/* try again with a bit different memory target */
> -		start = bitmapno + mask + 1;
> -	}
> -
> -	pr_debug("%s(): returned %p\n", __func__, page);
> -	return page;
> -}
> -
>  struct page *dma_alloc_from_contiguous(struct device *dev, int count,
>  				       unsigned int align)
>  {
> -	struct cma *cma = dev_get_cma_area(dev);
> -
>  	if (align > CONFIG_CMA_ALIGNMENT)
>  		align = CONFIG_CMA_ALIGNMENT;
>
> -	return __dma_alloc_from_contiguous(cma, count, align);
> -}
> -
> -/**
> - * dma_release_from_contiguous() - release allocated pages
> - * @dev:   Pointer to device for which the pages were allocated.
> - * @pages: Allocated pages.
> - * @count: Number of allocated pages.
> - *
> - * This function releases memory allocated by dma_alloc_from_contiguous().
> - * It returns false when provided pages do not belong to contiguous area and
> - * true otherwise.
> - */
> -static bool __dma_release_from_contiguous(struct cma *cma, struct page *pages,
> -				 int count)
> -{
> -	unsigned long pfn;
> -
> -	if (!cma || !pages)
> -		return false;
> -
> -	pr_debug("%s(page %p)\n", __func__, (void *)pages);
> -
> -	pfn = page_to_pfn(pages);
> -
> -	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> -		return false;
> -
> -	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
> -
> -	free_contig_range(pfn, count);
> -	clear_cma_bitmap(cma, pfn, count);
> -
> -	return true;
> +	return cma_alloc(dev_get_cma_area(dev), count, align);
>  }
>
>  bool dma_release_from_contiguous(struct device *dev, struct page *pages,
>  				 int count)
>  {
> -	struct cma *cma = dev_get_cma_area(dev);
> -
> -	return __dma_release_from_contiguous(cma, pages, count);
> +	return cma_release(dev_get_cma_area(dev), pages, count);
>  }
> diff --git a/include/linux/cma.h b/include/linux/cma.h
> new file mode 100644
> index 0000000..e38efe9
> --- /dev/null
> +++ b/include/linux/cma.h
> @@ -0,0 +1,12 @@
> +#ifndef __CMA_H__
> +#define __CMA_H__
> +
> +struct cma;
> +
> +extern int __init cma_declare_contiguous(phys_addr_t size,
> +				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment, int order_per_bit,
> +				struct cma **res_cma, bool fixed);
> +extern struct page *cma_alloc(struct cma *cma, int count, unsigned int align);
> +extern bool cma_release(struct cma *cma, struct page *pages, int count);
> +#endif
> diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h
> index 772eab5..a40c1f3 100644
> --- a/include/linux/dma-contiguous.h
> +++ b/include/linux/dma-contiguous.h
> @@ -53,9 +53,10 @@
>
>  #ifdef __KERNEL__
>
> +#include <linux/device.h>
> +
>  struct cma;
>  struct page;
> -struct device;
>
>  #ifdef CONFIG_DMA_CMA
>
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 3e9977a..f4899ec 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -508,6 +508,17 @@ config CMA_DEBUG
>  	  processing calls such as dma_alloc_from_contiguous().
>  	  This option does not affect warning and error messages.
>
> +config CMA_AREAS
> +	int "Maximum count of the CMA areas"
> +	depends on CMA
> +	default 7
> +	help
> +	  CMA allows to create CMA areas for particular purpose, mainly,
> +	  used as device private area. This parameter sets the maximum
> +	  number of CMA area in the system.
> +
> +	  If unsure, leave the default value "7".
> +
>  config ZBUD
>  	tristate
>  	default n
> diff --git a/mm/Makefile b/mm/Makefile
> index 1eaa70b..bc0422b 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -62,3 +62,4 @@ obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
>  obj-$(CONFIG_ZBUD)	+= zbud.o
>  obj-$(CONFIG_ZSMALLOC)	+= zsmalloc.o
>  obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
> +obj-$(CONFIG_CMA)	+= cma.o
> diff --git a/mm/cma.c b/mm/cma.c
> new file mode 100644
> index 0000000..1e1b017
> --- /dev/null
> +++ b/mm/cma.c
> @@ -0,0 +1,330 @@
> +/*
> + * Contiguous Memory Allocator
> + *
> + * Copyright (c) 2010-2011 by Samsung Electronics.
> + * Copyright IBM Corporation, 2013
> + * Copyright LG Electronics Inc., 2014
> + * Written by:
> + *	Marek Szyprowski <m.szyprowski@samsung.com>
> + *	Michal Nazarewicz <mina86@mina86.com>
> + *	Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> + *	Joonsoo Kim <iamjoonsoo.kim@lge.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation; either version 2 of the
> + * License or (at your optional) any later version of the license.
> + */
> +
> +#define pr_fmt(fmt) "cma: " fmt
> +
> +#ifdef CONFIG_CMA_DEBUG
> +#ifndef DEBUG
> +#  define DEBUG
> +#endif
> +#endif
> +
> +#include <linux/memblock.h>
> +#include <linux/err.h>
> +#include <linux/mm.h>
> +#include <linux/mutex.h>
> +#include <linux/sizes.h>
> +#include <linux/slab.h>
> +
> +struct cma {
> +	unsigned long	base_pfn;
> +	unsigned long	count;
> +	unsigned long	*bitmap;
> +	int order_per_bit; /* Order of pages represented by one bit */
> +	struct mutex	lock;
> +};
> +
> +/*
> + * There is always at least global CMA area and a few optional
> + * areas configured in kernel .config.
> + */
> +#define MAX_CMA_AREAS	(1 + CONFIG_CMA_AREAS)
> +
> +static struct cma cma_areas[MAX_CMA_AREAS];
> +static unsigned cma_area_count;
> +static DEFINE_MUTEX(cma_mutex);
> +
> +static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> +{
> +	return (1 << (align_order >> cma->order_per_bit)) - 1;
> +}
> +
> +static unsigned long cma_bitmap_maxno(struct cma *cma)
> +{
> +	return cma->count >> cma->order_per_bit;
> +}
> +
> +static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
> +						unsigned long pages)
> +{
> +	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
> +}
> +
> +static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
> +{
> +	unsigned long bitmapno, nr_bits;
> +
> +	bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
> +	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> +
> +	mutex_lock(&cma->lock);
> +	bitmap_clear(cma->bitmap, bitmapno, nr_bits);
> +	mutex_unlock(&cma->lock);
> +}
> +
> +static int __init cma_activate_area(struct cma *cma)
> +{
> +	int bitmap_maxno = cma_bitmap_maxno(cma);
> +	int bitmap_size = BITS_TO_LONGS(bitmap_maxno) * sizeof(long);
> +	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
> +	unsigned i = cma->count >> pageblock_order;
> +	struct zone *zone;
> +
> +	pr_debug("%s()\n", __func__);
> +
> +	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> +	if (!cma->bitmap)
> +		return -ENOMEM;
> +
> +	WARN_ON_ONCE(!pfn_valid(pfn));
> +	zone = page_zone(pfn_to_page(pfn));
> +
> +	do {
> +		unsigned j;
> +
> +		base_pfn = pfn;
> +		for (j = pageblock_nr_pages; j; --j, pfn++) {
> +			WARN_ON_ONCE(!pfn_valid(pfn));
> +			/*
> +			 * alloc_contig_range requires the pfn range
> +			 * specified to be in the same zone. Make this
> +			 * simple by forcing the entire CMA resv range
> +			 * to be in the same zone.
> +			 */
> +			if (page_zone(pfn_to_page(pfn)) != zone)
> +				goto err;
> +		}
> +		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
> +	} while (--i);
> +
> +	mutex_init(&cma->lock);
> +	return 0;
> +
> +err:
> +	kfree(cma->bitmap);
> +	return -EINVAL;
> +}
> +
> +static int __init cma_init_reserved_areas(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < cma_area_count; i++) {
> +		int ret = cma_activate_area(&cma_areas[i]);
> +
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +core_initcall(cma_init_reserved_areas);
> +
> +/**
> + * cma_declare_contiguous() - reserve custom contiguous area
> + * @size: Size of the reserved area (in bytes),
> + * @base: Base address of the reserved area optional, use 0 for any
> + * @limit: End address of the reserved memory (optional, 0 for any).
> + * @alignment: Alignment for the contiguous memory area, should be power of 2
> + * @order_per_bit: Order of pages represented by one bit on bitmap.
> + * @res_cma: Pointer to store the created cma region.
> + * @fixed: hint about where to place the reserved area
> + *
> + * This function reserves memory from early allocator. It should be
> + * called by arch specific code once the early allocator (memblock or bootmem)
> + * has been activated and all other subsystems have already allocated/reserved
> + * memory. This function allows to create custom reserved areas.
> + *
> + * If @fixed is true, reserve contiguous area at exactly @base.  If false,
> + * reserve in range from @base to @limit.
> + */
> +int __init cma_declare_contiguous(phys_addr_t size,
> +				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment, int order_per_bit,
> +				struct cma **res_cma, bool fixed)
> +{
> +	struct cma *cma = &cma_areas[cma_area_count];
> +	int ret = 0;
> +
> +	pr_debug("%s(size %lx, base %08lx, limit %08lx alignment %08lx)\n",
> +		__func__, (unsigned long)size, (unsigned long)base,
> +		(unsigned long)limit, (unsigned long)alignment);
> +
> +	/* Sanity checks */
> +	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
> +		pr_err("%s(): Not enough slots for CMA reserved regions!\n",
> +			__func__);
> +		return -ENOSPC;
> +	}
> +
> +	if (!size)
> +		return -EINVAL;
> +
> +	if (alignment && !is_power_of_2(alignment))
> +		return -EINVAL;
> +
> +	/*
> +	 * Sanitise input arguments.
> +	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
> +	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
> +	 * and CMA property will be broken.
> +	 */
> +	alignment = max(alignment,
> +		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
> +	base = ALIGN(base, alignment);
> +	size = ALIGN(size, alignment);
> +	limit &= ~(alignment - 1);
> +	/* size should be aligned with order_per_bit */
> +	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit));
> +
> +	/* Reserve memory */
> +	if (base && fixed) {
> +		if (memblock_is_region_reserved(base, size) ||
> +		    memblock_reserve(base, size) < 0) {
> +			ret = -EBUSY;
> +			goto err;
> +		}
> +	} else {
> +		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
> +							limit);
> +		if (!addr) {
> +			ret = -ENOMEM;
> +			goto err;
> +		} else {
> +			base = addr;
> +		}
> +	}
> +
> +	/*
> +	 * Each reserved area must be initialised later, when more kernel
> +	 * subsystems (like slab allocator) are available.
> +	 */
> +	cma->base_pfn = PFN_DOWN(base);
> +	cma->count = size >> PAGE_SHIFT;
> +	cma->order_per_bit = order_per_bit;
> +	*res_cma = cma;
> +	cma_area_count++;
> +
> +	pr_info("%s(): reserved %ld MiB at %08lx\n",
> +		__func__, (unsigned long)size / SZ_1M, (unsigned long)base);
> +	return 0;
> +
> +err:
> +	pr_err("%s(): failed to reserve %ld MiB\n",
> +		__func__, (unsigned long)size / SZ_1M);
> +	return ret;
> +}
> +
> +/**
> + * cma_alloc() - allocate pages from contiguous area
> + * @cma:   Contiguous memory region for which the allocation is performed.
> + * @count: Requested number of pages.
> + * @align: Requested alignment of pages (in PAGE_SIZE order).
> + *
> + * This function allocates part of contiguous memory on specific
> + * contiguous memory area.
> + */
> +struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
> +{
> +	unsigned long mask, pfn, start = 0;
> +	unsigned long bitmap_maxno, bitmapno, nr_bits;
> +	struct page *page = NULL;
> +	int ret;
> +
> +	if (!cma || !cma->count)
> +		return NULL;
> +
> +	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
> +		 count, align);
> +
> +	if (!count)
> +		return NULL;
> +
> +	mask = cma_bitmap_aligned_mask(cma, align);
> +	bitmap_maxno = cma_bitmap_maxno(cma);
> +	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> +
> +	for (;;) {
> +		mutex_lock(&cma->lock);
> +		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
> +					bitmap_maxno, start, nr_bits, mask);
> +		if (bitmapno >= bitmap_maxno) {
> +			mutex_unlock(&cma->lock);
> +			break;
> +		}
> +		bitmap_set(cma->bitmap, bitmapno, nr_bits);
> +		/*
> +		 * It's safe to drop the lock here. We've marked this region for
> +		 * our exclusive use. If the migration fails we will take the
> +		 * lock again and unmark it.
> +		 */
> +		mutex_unlock(&cma->lock);
> +
> +		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
> +		mutex_lock(&cma_mutex);
> +		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
> +		mutex_unlock(&cma_mutex);
> +		if (ret == 0) {
> +			page = pfn_to_page(pfn);
> +			break;
> +		} else if (ret != -EBUSY) {
> +			clear_cma_bitmap(cma, pfn, count);
> +			break;
> +		}
> +		clear_cma_bitmap(cma, pfn, count);
> +		pr_debug("%s(): memory range at %p is busy, retrying\n",
> +			 __func__, pfn_to_page(pfn));
> +		/* try again with a bit different memory target */
> +		start = bitmapno + mask + 1;
> +	}
> +
> +	pr_debug("%s(): returned %p\n", __func__, page);
> +	return page;
> +}
> +
> +/**
> + * cma_release() - release allocated pages
> + * @cma:   Contiguous memory region for which the allocation is performed.
> + * @pages: Allocated pages.
> + * @count: Number of allocated pages.
> + *
> + * This function releases memory allocated by alloc_cma().
> + * It returns false when provided pages do not belong to contiguous area and
> + * true otherwise.
> + */
> +bool cma_release(struct cma *cma, struct page *pages, int count)
> +{
> +	unsigned long pfn;
> +
> +	if (!cma || !pages)
> +		return false;
> +
> +	pr_debug("%s(page %p)\n", __func__, (void *)pages);
> +
> +	pfn = page_to_pfn(pages);
> +
> +	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> +		return false;
> +
> +	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
> +
> +	free_contig_range(pfn, count);
> +	clear_cma_bitmap(cma, pfn, count);
> +
> +	return true;
> +}
> -- 
> 1.7.9.5

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Aneesh Kumar K.V - June 14, 2014, 10:08 a.m.
Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:

> Currently, there are two users on CMA functionality, one is the DMA
> subsystem and the other is the kvm on powerpc. They have their own code
> to manage CMA reserved area even if they looks really similar.
> From my guess, it is caused by some needs on bitmap management. Kvm side
> wants to maintain bitmap not for 1 page, but for more size. Eventually it
> use bitmap where one bit represents 64 pages.
>
> When I implement CMA related patches, I should change those two places
> to apply my change and it seem to be painful to me. I want to change
> this situation and reduce future code management overhead through
> this patch.
>
> This change could also help developer who want to use CMA in their
> new feature development, since they can use CMA easily without
> copying & pasting this reserved area management code.
>
> In previous patches, we have prepared some features to generalize
> CMA reserved area management and now it's time to do it. This patch
> moves core functions to mm/cma.c and change DMA APIs to use
> these functions.
>
> There is no functional change in DMA APIs.
>
> v2: There is no big change from v1 in mm/cma.c. Mostly renaming.
>
> Acked-by: Michal Nazarewicz <mina86@mina86.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

>
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index 00e13ce..4eac559 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -283,16 +283,6 @@ config CMA_ALIGNMENT
>
>  	  If unsure, leave the default value "8".
>
> -config CMA_AREAS
> -	int "Maximum count of the CMA device-private areas"
> -	default 7
> -	help
> -	  CMA allows to create CMA areas for particular devices. This parameter
> -	  sets the maximum number of such device private CMA areas in the
> -	  system.
> -
> -	  If unsure, leave the default value "7".
> -
>  endif
>
>  endmenu
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index 9bc9340..f177f73 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -24,25 +24,10 @@
>
>  #include <linux/memblock.h>
>  #include <linux/err.h>
> -#include <linux/mm.h>
> -#include <linux/mutex.h>
> -#include <linux/page-isolation.h>
>  #include <linux/sizes.h>
> -#include <linux/slab.h>
> -#include <linux/swap.h>
> -#include <linux/mm_types.h>
>  #include <linux/dma-contiguous.h>
>  #include <linux/log2.h>
> -
> -struct cma {
> -	unsigned long	base_pfn;
> -	unsigned long	count;
> -	unsigned long	*bitmap;
> -	int order_per_bit; /* Order of pages represented by one bit */
> -	struct mutex	lock;
> -};
> -
> -struct cma *dma_contiguous_default_area;
> +#include <linux/cma.h>
>
>  #ifdef CONFIG_CMA_SIZE_MBYTES
>  #define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES
> @@ -50,6 +35,8 @@ struct cma *dma_contiguous_default_area;
>  #define CMA_SIZE_MBYTES 0
>  #endif
>
> +struct cma *dma_contiguous_default_area;
> +
>  /*
>   * Default global CMA area size can be defined in kernel's .config.
>   * This is useful mainly for distro maintainers to create a kernel
> @@ -156,199 +143,13 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
>  	}
>  }
>
> -static DEFINE_MUTEX(cma_mutex);
> -
> -static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> -{
> -	return (1 << (align_order >> cma->order_per_bit)) - 1;
> -}
> -
> -static unsigned long cma_bitmap_maxno(struct cma *cma)
> -{
> -	return cma->count >> cma->order_per_bit;
> -}
> -
> -static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
> -						unsigned long pages)
> -{
> -	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
> -}
> -
> -static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
> -{
> -	unsigned long bitmapno, nr_bits;
> -
> -	bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
> -	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> -
> -	mutex_lock(&cma->lock);
> -	bitmap_clear(cma->bitmap, bitmapno, nr_bits);
> -	mutex_unlock(&cma->lock);
> -}
> -
> -static int __init cma_activate_area(struct cma *cma)
> -{
> -	int bitmap_maxno = cma_bitmap_maxno(cma);
> -	int bitmap_size = BITS_TO_LONGS(bitmap_maxno) * sizeof(long);
> -	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
> -	unsigned i = cma->count >> pageblock_order;
> -	struct zone *zone;
> -
> -	pr_debug("%s()\n", __func__);
> -
> -	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> -	if (!cma->bitmap)
> -		return -ENOMEM;
> -
> -	WARN_ON_ONCE(!pfn_valid(pfn));
> -	zone = page_zone(pfn_to_page(pfn));
> -
> -	do {
> -		unsigned j;
> -		base_pfn = pfn;
> -		for (j = pageblock_nr_pages; j; --j, pfn++) {
> -			WARN_ON_ONCE(!pfn_valid(pfn));
> -			/*
> -			 * alloc_contig_range requires the pfn range
> -			 * specified to be in the same zone. Make this
> -			 * simple by forcing the entire CMA resv range
> -			 * to be in the same zone.
> -			 */
> -			if (page_zone(pfn_to_page(pfn)) != zone)
> -				goto err;
> -		}
> -		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
> -	} while (--i);
> -
> -	mutex_init(&cma->lock);
> -	return 0;
> -
> -err:
> -	kfree(cma->bitmap);
> -	return -EINVAL;
> -}
> -
> -static struct cma cma_areas[MAX_CMA_AREAS];
> -static unsigned cma_area_count;
> -
> -static int __init cma_init_reserved_areas(void)
> -{
> -	int i;
> -
> -	for (i = 0; i < cma_area_count; i++) {
> -		int ret = cma_activate_area(&cma_areas[i]);
> -		if (ret)
> -			return ret;
> -	}
> -
> -	return 0;
> -}
> -core_initcall(cma_init_reserved_areas);
> -
> -/**
> - * dma_contiguous_reserve_area() - reserve custom contiguous area
> - * @size: Size of the reserved area (in bytes),
> - * @base: Base address of the reserved area optional, use 0 for any
> - * @limit: End address of the reserved memory (optional, 0 for any).
> - * @alignment: Alignment for the contiguous memory area, should be power of 2
> - * @order_per_bit: Order of pages represented by one bit on bitmap.
> - * @res_cma: Pointer to store the created cma region.
> - * @fixed: hint about where to place the reserved area
> - *
> - * This function reserves memory from early allocator. It should be
> - * called by arch specific code once the early allocator (memblock or bootmem)
> - * has been activated and all other subsystems have already allocated/reserved
> - * memory. This function allows to create custom reserved areas for specific
> - * devices.
> - *
> - * If @fixed is true, reserve contiguous area at exactly @base.  If false,
> - * reserve in range from @base to @limit.
> - */
> -static int __init __dma_contiguous_reserve_area(phys_addr_t size,
> -				phys_addr_t base, phys_addr_t limit,
> -				phys_addr_t alignment, int order_per_bit,
> -				struct cma **res_cma, bool fixed)
> -{
> -	struct cma *cma = &cma_areas[cma_area_count];
> -	int ret = 0;
> -
> -	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> -		__func__, (unsigned long)size, (unsigned long)base,
> -		(unsigned long)limit, (unsigned long)alignment);
> -
> -	/* Sanity checks */
> -	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
> -		pr_err("%s(): Not enough slots for CMA reserved regions!\n",
> -			__func__);
> -		return -ENOSPC;
> -	}
> -
> -	if (!size)
> -		return -EINVAL;
> -
> -	if (alignment && !is_power_of_2(alignment))
> -		return -EINVAL;
> -
> -	/*
> -	 * Sanitise input arguments.
> -	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
> -	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
> -	 * and CMA property will be broken.
> -	 */
> -	alignment = max(alignment,
> -		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
> -	base = ALIGN(base, alignment);
> -	size = ALIGN(size, alignment);
> -	limit &= ~(alignment - 1);
> -	/* size should be aligned with order_per_bit */
> -	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit));
> -
> -	/* Reserve memory */
> -	if (base && fixed) {
> -		if (memblock_is_region_reserved(base, size) ||
> -		    memblock_reserve(base, size) < 0) {
> -			ret = -EBUSY;
> -			goto err;
> -		}
> -	} else {
> -		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
> -							limit);
> -		if (!addr) {
> -			ret = -ENOMEM;
> -			goto err;
> -		} else {
> -			base = addr;
> -		}
> -	}
> -
> -	/*
> -	 * Each reserved area must be initialised later, when more kernel
> -	 * subsystems (like slab allocator) are available.
> -	 */
> -	cma->base_pfn = PFN_DOWN(base);
> -	cma->count = size >> PAGE_SHIFT;
> -	cma->order_per_bit = order_per_bit;
> -	*res_cma = cma;
> -	cma_area_count++;
> -
> -	pr_info("%s(): reserved %ld MiB at %08lx\n",
> -		__func__, (unsigned long)size / SZ_1M, (unsigned long)base);
> -	return 0;
> -
> -err:
> -	pr_err("%s(): failed to reserve %ld MiB\n",
> -		__func__, (unsigned long)size / SZ_1M);
> -	return ret;
> -}
> -
>  int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  				       phys_addr_t limit, struct cma **res_cma,
>  				       bool fixed)
>  {
>  	int ret;
>
> -	ret = __dma_contiguous_reserve_area(size, base, limit, 0, 0,
> -						res_cma, fixed);
> +	ret = cma_declare_contiguous(size, base, limit, 0, 0, res_cma, fixed);
>  	if (ret)
>  		return ret;
>
> @@ -358,124 +159,17 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  	return 0;
>  }
>
> -/**
> - * dma_alloc_from_contiguous() - allocate pages from contiguous area
> - * @dev:   Pointer to device for which the allocation is performed.
> - * @count: Requested number of pages.
> - * @align: Requested alignment of pages (in PAGE_SIZE order).
> - *
> - * This function allocates memory buffer for specified device. It uses
> - * device specific contiguous memory area if available or the default
> - * global one. Requires architecture specific dev_get_cma_area() helper
> - * function.
> - */
> -static struct page *__dma_alloc_from_contiguous(struct cma *cma, int count,
> -				       unsigned int align)
> -{
> -	unsigned long mask, pfn, start = 0;
> -	unsigned long bitmap_maxno, bitmapno, nr_bits;
> -	struct page *page = NULL;
> -	int ret;
> -
> -	if (!cma || !cma->count)
> -		return NULL;
> -
> -	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
> -		 count, align);
> -
> -	if (!count)
> -		return NULL;
> -
> -	mask = cma_bitmap_aligned_mask(cma, align);
> -	bitmap_maxno = cma_bitmap_maxno(cma);
> -	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> -
> -	for (;;) {
> -		mutex_lock(&cma->lock);
> -		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
> -					bitmap_maxno, start, nr_bits, mask);
> -		if (bitmapno >= bitmap_maxno) {
> -			mutex_unlock(&cma->lock);
> -			break;
> -		}
> -		bitmap_set(cma->bitmap, bitmapno, nr_bits);
> -		/*
> -		 * It's safe to drop the lock here. We've marked this region for
> -		 * our exclusive use. If the migration fails we will take the
> -		 * lock again and unmark it.
> -		 */
> -		mutex_unlock(&cma->lock);
> -
> -		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
> -		mutex_lock(&cma_mutex);
> -		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
> -		mutex_unlock(&cma_mutex);
> -		if (ret == 0) {
> -			page = pfn_to_page(pfn);
> -			break;
> -		} else if (ret != -EBUSY) {
> -			clear_cma_bitmap(cma, pfn, count);
> -			break;
> -		}
> -		clear_cma_bitmap(cma, pfn, count);
> -		pr_debug("%s(): memory range at %p is busy, retrying\n",
> -			 __func__, pfn_to_page(pfn));
> -		/* try again with a bit different memory target */
> -		start = bitmapno + mask + 1;
> -	}
> -
> -	pr_debug("%s(): returned %p\n", __func__, page);
> -	return page;
> -}
> -
>  struct page *dma_alloc_from_contiguous(struct device *dev, int count,
>  				       unsigned int align)
>  {
> -	struct cma *cma = dev_get_cma_area(dev);
> -
>  	if (align > CONFIG_CMA_ALIGNMENT)
>  		align = CONFIG_CMA_ALIGNMENT;
>
> -	return __dma_alloc_from_contiguous(cma, count, align);
> -}
> -
> -/**
> - * dma_release_from_contiguous() - release allocated pages
> - * @dev:   Pointer to device for which the pages were allocated.
> - * @pages: Allocated pages.
> - * @count: Number of allocated pages.
> - *
> - * This function releases memory allocated by dma_alloc_from_contiguous().
> - * It returns false when provided pages do not belong to contiguous area and
> - * true otherwise.
> - */
> -static bool __dma_release_from_contiguous(struct cma *cma, struct page *pages,
> -				 int count)
> -{
> -	unsigned long pfn;
> -
> -	if (!cma || !pages)
> -		return false;
> -
> -	pr_debug("%s(page %p)\n", __func__, (void *)pages);
> -
> -	pfn = page_to_pfn(pages);
> -
> -	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> -		return false;
> -
> -	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
> -
> -	free_contig_range(pfn, count);
> -	clear_cma_bitmap(cma, pfn, count);
> -
> -	return true;
> +	return cma_alloc(dev_get_cma_area(dev), count, align);
>  }
>
>  bool dma_release_from_contiguous(struct device *dev, struct page *pages,
>  				 int count)
>  {
> -	struct cma *cma = dev_get_cma_area(dev);
> -
> -	return __dma_release_from_contiguous(cma, pages, count);
> +	return cma_release(dev_get_cma_area(dev), pages, count);
>  }
> diff --git a/include/linux/cma.h b/include/linux/cma.h
> new file mode 100644
> index 0000000..e38efe9
> --- /dev/null
> +++ b/include/linux/cma.h
> @@ -0,0 +1,12 @@
> +#ifndef __CMA_H__
> +#define __CMA_H__
> +
> +struct cma;
> +
> +extern int __init cma_declare_contiguous(phys_addr_t size,
> +				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment, int order_per_bit,
> +				struct cma **res_cma, bool fixed);
> +extern struct page *cma_alloc(struct cma *cma, int count, unsigned int align);
> +extern bool cma_release(struct cma *cma, struct page *pages, int count);
> +#endif
> diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h
> index 772eab5..a40c1f3 100644
> --- a/include/linux/dma-contiguous.h
> +++ b/include/linux/dma-contiguous.h
> @@ -53,9 +53,10 @@
>
>  #ifdef __KERNEL__
>
> +#include <linux/device.h>
> +
>  struct cma;
>  struct page;
> -struct device;
>
>  #ifdef CONFIG_DMA_CMA
>
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 3e9977a..f4899ec 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -508,6 +508,17 @@ config CMA_DEBUG
>  	  processing calls such as dma_alloc_from_contiguous().
>  	  This option does not affect warning and error messages.
>
> +config CMA_AREAS
> +	int "Maximum count of the CMA areas"
> +	depends on CMA
> +	default 7
> +	help
> +	  CMA allows to create CMA areas for particular purpose, mainly,
> +	  used as device private area. This parameter sets the maximum
> +	  number of CMA area in the system.
> +
> +	  If unsure, leave the default value "7".
> +
>  config ZBUD
>  	tristate
>  	default n
> diff --git a/mm/Makefile b/mm/Makefile
> index 1eaa70b..bc0422b 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -62,3 +62,4 @@ obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
>  obj-$(CONFIG_ZBUD)	+= zbud.o
>  obj-$(CONFIG_ZSMALLOC)	+= zsmalloc.o
>  obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
> +obj-$(CONFIG_CMA)	+= cma.o
> diff --git a/mm/cma.c b/mm/cma.c
> new file mode 100644
> index 0000000..1e1b017
> --- /dev/null
> +++ b/mm/cma.c
> @@ -0,0 +1,330 @@
> +/*
> + * Contiguous Memory Allocator
> + *
> + * Copyright (c) 2010-2011 by Samsung Electronics.
> + * Copyright IBM Corporation, 2013
> + * Copyright LG Electronics Inc., 2014
> + * Written by:
> + *	Marek Szyprowski <m.szyprowski@samsung.com>
> + *	Michal Nazarewicz <mina86@mina86.com>
> + *	Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> + *	Joonsoo Kim <iamjoonsoo.kim@lge.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation; either version 2 of the
> + * License or (at your optional) any later version of the license.
> + */
> +
> +#define pr_fmt(fmt) "cma: " fmt
> +
> +#ifdef CONFIG_CMA_DEBUG
> +#ifndef DEBUG
> +#  define DEBUG
> +#endif
> +#endif
> +
> +#include <linux/memblock.h>
> +#include <linux/err.h>
> +#include <linux/mm.h>
> +#include <linux/mutex.h>
> +#include <linux/sizes.h>
> +#include <linux/slab.h>
> +
> +struct cma {
> +	unsigned long	base_pfn;
> +	unsigned long	count;
> +	unsigned long	*bitmap;
> +	int order_per_bit; /* Order of pages represented by one bit */
> +	struct mutex	lock;
> +};
> +
> +/*
> + * There is always at least global CMA area and a few optional
> + * areas configured in kernel .config.
> + */
> +#define MAX_CMA_AREAS	(1 + CONFIG_CMA_AREAS)
> +
> +static struct cma cma_areas[MAX_CMA_AREAS];
> +static unsigned cma_area_count;
> +static DEFINE_MUTEX(cma_mutex);
> +
> +static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> +{
> +	return (1 << (align_order >> cma->order_per_bit)) - 1;
> +}
> +
> +static unsigned long cma_bitmap_maxno(struct cma *cma)
> +{
> +	return cma->count >> cma->order_per_bit;
> +}
> +
> +static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
> +						unsigned long pages)
> +{
> +	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
> +}
> +
> +static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
> +{
> +	unsigned long bitmapno, nr_bits;
> +
> +	bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
> +	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> +
> +	mutex_lock(&cma->lock);
> +	bitmap_clear(cma->bitmap, bitmapno, nr_bits);
> +	mutex_unlock(&cma->lock);
> +}
> +
> +static int __init cma_activate_area(struct cma *cma)
> +{
> +	int bitmap_maxno = cma_bitmap_maxno(cma);
> +	int bitmap_size = BITS_TO_LONGS(bitmap_maxno) * sizeof(long);
> +	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
> +	unsigned i = cma->count >> pageblock_order;
> +	struct zone *zone;
> +
> +	pr_debug("%s()\n", __func__);
> +
> +	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> +	if (!cma->bitmap)
> +		return -ENOMEM;
> +
> +	WARN_ON_ONCE(!pfn_valid(pfn));
> +	zone = page_zone(pfn_to_page(pfn));
> +
> +	do {
> +		unsigned j;
> +
> +		base_pfn = pfn;
> +		for (j = pageblock_nr_pages; j; --j, pfn++) {
> +			WARN_ON_ONCE(!pfn_valid(pfn));
> +			/*
> +			 * alloc_contig_range requires the pfn range
> +			 * specified to be in the same zone. Make this
> +			 * simple by forcing the entire CMA resv range
> +			 * to be in the same zone.
> +			 */
> +			if (page_zone(pfn_to_page(pfn)) != zone)
> +				goto err;
> +		}
> +		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
> +	} while (--i);
> +
> +	mutex_init(&cma->lock);
> +	return 0;
> +
> +err:
> +	kfree(cma->bitmap);
> +	return -EINVAL;
> +}
> +
> +static int __init cma_init_reserved_areas(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < cma_area_count; i++) {
> +		int ret = cma_activate_area(&cma_areas[i]);
> +
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +core_initcall(cma_init_reserved_areas);
> +
> +/**
> + * cma_declare_contiguous() - reserve custom contiguous area
> + * @size: Size of the reserved area (in bytes),
> + * @base: Base address of the reserved area optional, use 0 for any
> + * @limit: End address of the reserved memory (optional, 0 for any).
> + * @alignment: Alignment for the contiguous memory area, should be power of 2
> + * @order_per_bit: Order of pages represented by one bit on bitmap.
> + * @res_cma: Pointer to store the created cma region.
> + * @fixed: hint about where to place the reserved area
> + *
> + * This function reserves memory from early allocator. It should be
> + * called by arch specific code once the early allocator (memblock or bootmem)
> + * has been activated and all other subsystems have already allocated/reserved
> + * memory. This function allows to create custom reserved areas.
> + *
> + * If @fixed is true, reserve contiguous area at exactly @base.  If false,
> + * reserve in range from @base to @limit.
> + */
> +int __init cma_declare_contiguous(phys_addr_t size,
> +				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment, int order_per_bit,
> +				struct cma **res_cma, bool fixed)
> +{
> +	struct cma *cma = &cma_areas[cma_area_count];
> +	int ret = 0;
> +
> +	pr_debug("%s(size %lx, base %08lx, limit %08lx alignment %08lx)\n",
> +		__func__, (unsigned long)size, (unsigned long)base,
> +		(unsigned long)limit, (unsigned long)alignment);
> +
> +	/* Sanity checks */
> +	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
> +		pr_err("%s(): Not enough slots for CMA reserved regions!\n",
> +			__func__);
> +		return -ENOSPC;
> +	}
> +
> +	if (!size)
> +		return -EINVAL;
> +
> +	if (alignment && !is_power_of_2(alignment))
> +		return -EINVAL;
> +
> +	/*
> +	 * Sanitise input arguments.
> +	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
> +	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
> +	 * and CMA property will be broken.
> +	 */
> +	alignment = max(alignment,
> +		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
> +	base = ALIGN(base, alignment);
> +	size = ALIGN(size, alignment);
> +	limit &= ~(alignment - 1);
> +	/* size should be aligned with order_per_bit */
> +	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit));
> +
> +	/* Reserve memory */
> +	if (base && fixed) {
> +		if (memblock_is_region_reserved(base, size) ||
> +		    memblock_reserve(base, size) < 0) {
> +			ret = -EBUSY;
> +			goto err;
> +		}
> +	} else {
> +		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
> +							limit);
> +		if (!addr) {
> +			ret = -ENOMEM;
> +			goto err;
> +		} else {
> +			base = addr;
> +		}
> +	}
> +
> +	/*
> +	 * Each reserved area must be initialised later, when more kernel
> +	 * subsystems (like slab allocator) are available.
> +	 */
> +	cma->base_pfn = PFN_DOWN(base);
> +	cma->count = size >> PAGE_SHIFT;
> +	cma->order_per_bit = order_per_bit;
> +	*res_cma = cma;
> +	cma_area_count++;
> +
> +	pr_info("%s(): reserved %ld MiB at %08lx\n",
> +		__func__, (unsigned long)size / SZ_1M, (unsigned long)base);
> +	return 0;
> +
> +err:
> +	pr_err("%s(): failed to reserve %ld MiB\n",
> +		__func__, (unsigned long)size / SZ_1M);
> +	return ret;
> +}
> +
> +/**
> + * cma_alloc() - allocate pages from contiguous area
> + * @cma:   Contiguous memory region for which the allocation is performed.
> + * @count: Requested number of pages.
> + * @align: Requested alignment of pages (in PAGE_SIZE order).
> + *
> + * This function allocates part of contiguous memory on specific
> + * contiguous memory area.
> + */
> +struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
> +{
> +	unsigned long mask, pfn, start = 0;
> +	unsigned long bitmap_maxno, bitmapno, nr_bits;
> +	struct page *page = NULL;
> +	int ret;
> +
> +	if (!cma || !cma->count)
> +		return NULL;
> +
> +	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
> +		 count, align);
> +
> +	if (!count)
> +		return NULL;
> +
> +	mask = cma_bitmap_aligned_mask(cma, align);
> +	bitmap_maxno = cma_bitmap_maxno(cma);
> +	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> +
> +	for (;;) {
> +		mutex_lock(&cma->lock);
> +		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
> +					bitmap_maxno, start, nr_bits, mask);
> +		if (bitmapno >= bitmap_maxno) {
> +			mutex_unlock(&cma->lock);
> +			break;
> +		}
> +		bitmap_set(cma->bitmap, bitmapno, nr_bits);
> +		/*
> +		 * It's safe to drop the lock here. We've marked this region for
> +		 * our exclusive use. If the migration fails we will take the
> +		 * lock again and unmark it.
> +		 */
> +		mutex_unlock(&cma->lock);
> +
> +		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
> +		mutex_lock(&cma_mutex);
> +		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
> +		mutex_unlock(&cma_mutex);
> +		if (ret == 0) {
> +			page = pfn_to_page(pfn);
> +			break;
> +		} else if (ret != -EBUSY) {
> +			clear_cma_bitmap(cma, pfn, count);
> +			break;
> +		}
> +		clear_cma_bitmap(cma, pfn, count);
> +		pr_debug("%s(): memory range at %p is busy, retrying\n",
> +			 __func__, pfn_to_page(pfn));
> +		/* try again with a bit different memory target */
> +		start = bitmapno + mask + 1;
> +	}
> +
> +	pr_debug("%s(): returned %p\n", __func__, page);
> +	return page;
> +}
> +
> +/**
> + * cma_release() - release allocated pages
> + * @cma:   Contiguous memory region for which the allocation is performed.
> + * @pages: Allocated pages.
> + * @count: Number of allocated pages.
> + *
> + * This function releases memory allocated by alloc_cma().
> + * It returns false when provided pages do not belong to contiguous area and
> + * true otherwise.
> + */
> +bool cma_release(struct cma *cma, struct page *pages, int count)
> +{
> +	unsigned long pfn;
> +
> +	if (!cma || !pages)
> +		return false;
> +
> +	pr_debug("%s(page %p)\n", __func__, (void *)pages);
> +
> +	pfn = page_to_pfn(pages);
> +
> +	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> +		return false;
> +
> +	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
> +
> +	free_contig_range(pfn, count);
> +	clear_cma_bitmap(cma, pfn, count);
> +
> +	return true;
> +}
> -- 
> 1.7.9.5

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Aneesh Kumar K.V - June 14, 2014, 10:16 a.m.
Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:

> Currently, there are two users on CMA functionality, one is the DMA
> subsystem and the other is the kvm on powerpc. They have their own code
> to manage CMA reserved area even if they looks really similar.
> From my guess, it is caused by some needs on bitmap management. Kvm side
> wants to maintain bitmap not for 1 page, but for more size. Eventually it
> use bitmap where one bit represents 64 pages.
>
> When I implement CMA related patches, I should change those two places
> to apply my change and it seem to be painful to me. I want to change
> this situation and reduce future code management overhead through
> this patch.
>
> This change could also help developer who want to use CMA in their
> new feature development, since they can use CMA easily without
> copying & pasting this reserved area management code.
>
> In previous patches, we have prepared some features to generalize
> CMA reserved area management and now it's time to do it. This patch
> moves core functions to mm/cma.c and change DMA APIs to use
> these functions.
>
> There is no functional change in DMA APIs.
>
> v2: There is no big change from v1 in mm/cma.c. Mostly renaming.
>
> Acked-by: Michal Nazarewicz <mina86@mina86.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>

.....

> +
> +	mask = cma_bitmap_aligned_mask(cma, align);
> +	bitmap_maxno = cma_bitmap_maxno(cma);
> +	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> +
> +	for (;;) {
> +		mutex_lock(&cma->lock);
> +		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
> +					bitmap_maxno, start, nr_bits, mask);
> +		if (bitmapno >= bitmap_maxno) {
> +			mutex_unlock(&cma->lock);
> +			break;
> +		}
> +		bitmap_set(cma->bitmap, bitmapno, nr_bits);
> +		/*
> +		 * It's safe to drop the lock here. We've marked this region for
> +		 * our exclusive use. If the migration fails we will take the
> +		 * lock again and unmark it.
> +		 */
> +		mutex_unlock(&cma->lock);
> +
> +		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
> +		mutex_lock(&cma_mutex);
> +		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
> +		mutex_unlock(&cma_mutex);
> +		if (ret == 0) {
> +			page = pfn_to_page(pfn);
> +			break;
> +		} else if (ret != -EBUSY) {
> +			clear_cma_bitmap(cma, pfn, count);
> +			break;
> +		}
> +		


For setting bit map we do
		bitmap_set(cma->bitmap, bitmapno, nr_bits);
                alloc_contig()..
                if (error)
                        clear_cma_bitmap(cma, pfn, count);

Why ?

why not bitmap_clear() ?

-aneesh

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Joonsoo Kim - June 16, 2014, 5:27 a.m.
On Sat, Jun 14, 2014 at 03:46:44PM +0530, Aneesh Kumar K.V wrote:
> Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:
> 
> > Currently, there are two users on CMA functionality, one is the DMA
> > subsystem and the other is the kvm on powerpc. They have their own code
> > to manage CMA reserved area even if they looks really similar.
> > From my guess, it is caused by some needs on bitmap management. Kvm side
> > wants to maintain bitmap not for 1 page, but for more size. Eventually it
> > use bitmap where one bit represents 64 pages.
> >
> > When I implement CMA related patches, I should change those two places
> > to apply my change and it seem to be painful to me. I want to change
> > this situation and reduce future code management overhead through
> > this patch.
> >
> > This change could also help developer who want to use CMA in their
> > new feature development, since they can use CMA easily without
> > copying & pasting this reserved area management code.
> >
> > In previous patches, we have prepared some features to generalize
> > CMA reserved area management and now it's time to do it. This patch
> > moves core functions to mm/cma.c and change DMA APIs to use
> > these functions.
> >
> > There is no functional change in DMA APIs.
> >
> > v2: There is no big change from v1 in mm/cma.c. Mostly renaming.
> >
> > Acked-by: Michal Nazarewicz <mina86@mina86.com>
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> >
> 
> .....
> 
> > +
> > +	mask = cma_bitmap_aligned_mask(cma, align);
> > +	bitmap_maxno = cma_bitmap_maxno(cma);
> > +	nr_bits = cma_bitmap_pages_to_bits(cma, count);
> > +
> > +	for (;;) {
> > +		mutex_lock(&cma->lock);
> > +		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
> > +					bitmap_maxno, start, nr_bits, mask);
> > +		if (bitmapno >= bitmap_maxno) {
> > +			mutex_unlock(&cma->lock);
> > +			break;
> > +		}
> > +		bitmap_set(cma->bitmap, bitmapno, nr_bits);
> > +		/*
> > +		 * It's safe to drop the lock here. We've marked this region for
> > +		 * our exclusive use. If the migration fails we will take the
> > +		 * lock again and unmark it.
> > +		 */
> > +		mutex_unlock(&cma->lock);
> > +
> > +		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
> > +		mutex_lock(&cma_mutex);
> > +		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
> > +		mutex_unlock(&cma_mutex);
> > +		if (ret == 0) {
> > +			page = pfn_to_page(pfn);
> > +			break;
> > +		} else if (ret != -EBUSY) {
> > +			clear_cma_bitmap(cma, pfn, count);
> > +			break;
> > +		}
> > +		
> 
> 
> For setting bit map we do
> 		bitmap_set(cma->bitmap, bitmapno, nr_bits);
>                 alloc_contig()..
>                 if (error)
>                         clear_cma_bitmap(cma, pfn, count);
> 
> Why ?
> 
> why not bitmap_clear() ?
> 

Unlike your psuedo code, for setting bitmap, we do
- grab the mutex
- bitmap_set
- release the mutex

clear_cma_bitmap() handles these things.

Thanks.

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Patch

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 00e13ce..4eac559 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -283,16 +283,6 @@  config CMA_ALIGNMENT
 
 	  If unsure, leave the default value "8".
 
-config CMA_AREAS
-	int "Maximum count of the CMA device-private areas"
-	default 7
-	help
-	  CMA allows to create CMA areas for particular devices. This parameter
-	  sets the maximum number of such device private CMA areas in the
-	  system.
-
-	  If unsure, leave the default value "7".
-
 endif
 
 endmenu
diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
index 9bc9340..f177f73 100644
--- a/drivers/base/dma-contiguous.c
+++ b/drivers/base/dma-contiguous.c
@@ -24,25 +24,10 @@ 
 
 #include <linux/memblock.h>
 #include <linux/err.h>
-#include <linux/mm.h>
-#include <linux/mutex.h>
-#include <linux/page-isolation.h>
 #include <linux/sizes.h>
-#include <linux/slab.h>
-#include <linux/swap.h>
-#include <linux/mm_types.h>
 #include <linux/dma-contiguous.h>
 #include <linux/log2.h>
-
-struct cma {
-	unsigned long	base_pfn;
-	unsigned long	count;
-	unsigned long	*bitmap;
-	int order_per_bit; /* Order of pages represented by one bit */
-	struct mutex	lock;
-};
-
-struct cma *dma_contiguous_default_area;
+#include <linux/cma.h>
 
 #ifdef CONFIG_CMA_SIZE_MBYTES
 #define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES
@@ -50,6 +35,8 @@  struct cma *dma_contiguous_default_area;
 #define CMA_SIZE_MBYTES 0
 #endif
 
+struct cma *dma_contiguous_default_area;
+
 /*
  * Default global CMA area size can be defined in kernel's .config.
  * This is useful mainly for distro maintainers to create a kernel
@@ -156,199 +143,13 @@  void __init dma_contiguous_reserve(phys_addr_t limit)
 	}
 }
 
-static DEFINE_MUTEX(cma_mutex);
-
-static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
-{
-	return (1 << (align_order >> cma->order_per_bit)) - 1;
-}
-
-static unsigned long cma_bitmap_maxno(struct cma *cma)
-{
-	return cma->count >> cma->order_per_bit;
-}
-
-static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
-						unsigned long pages)
-{
-	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
-}
-
-static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
-{
-	unsigned long bitmapno, nr_bits;
-
-	bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
-	nr_bits = cma_bitmap_pages_to_bits(cma, count);
-
-	mutex_lock(&cma->lock);
-	bitmap_clear(cma->bitmap, bitmapno, nr_bits);
-	mutex_unlock(&cma->lock);
-}
-
-static int __init cma_activate_area(struct cma *cma)
-{
-	int bitmap_maxno = cma_bitmap_maxno(cma);
-	int bitmap_size = BITS_TO_LONGS(bitmap_maxno) * sizeof(long);
-	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
-	unsigned i = cma->count >> pageblock_order;
-	struct zone *zone;
-
-	pr_debug("%s()\n", __func__);
-
-	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
-	if (!cma->bitmap)
-		return -ENOMEM;
-
-	WARN_ON_ONCE(!pfn_valid(pfn));
-	zone = page_zone(pfn_to_page(pfn));
-
-	do {
-		unsigned j;
-		base_pfn = pfn;
-		for (j = pageblock_nr_pages; j; --j, pfn++) {
-			WARN_ON_ONCE(!pfn_valid(pfn));
-			/*
-			 * alloc_contig_range requires the pfn range
-			 * specified to be in the same zone. Make this
-			 * simple by forcing the entire CMA resv range
-			 * to be in the same zone.
-			 */
-			if (page_zone(pfn_to_page(pfn)) != zone)
-				goto err;
-		}
-		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
-	} while (--i);
-
-	mutex_init(&cma->lock);
-	return 0;
-
-err:
-	kfree(cma->bitmap);
-	return -EINVAL;
-}
-
-static struct cma cma_areas[MAX_CMA_AREAS];
-static unsigned cma_area_count;
-
-static int __init cma_init_reserved_areas(void)
-{
-	int i;
-
-	for (i = 0; i < cma_area_count; i++) {
-		int ret = cma_activate_area(&cma_areas[i]);
-		if (ret)
-			return ret;
-	}
-
-	return 0;
-}
-core_initcall(cma_init_reserved_areas);
-
-/**
- * dma_contiguous_reserve_area() - reserve custom contiguous area
- * @size: Size of the reserved area (in bytes),
- * @base: Base address of the reserved area optional, use 0 for any
- * @limit: End address of the reserved memory (optional, 0 for any).
- * @alignment: Alignment for the contiguous memory area, should be power of 2
- * @order_per_bit: Order of pages represented by one bit on bitmap.
- * @res_cma: Pointer to store the created cma region.
- * @fixed: hint about where to place the reserved area
- *
- * This function reserves memory from early allocator. It should be
- * called by arch specific code once the early allocator (memblock or bootmem)
- * has been activated and all other subsystems have already allocated/reserved
- * memory. This function allows to create custom reserved areas for specific
- * devices.
- *
- * If @fixed is true, reserve contiguous area at exactly @base.  If false,
- * reserve in range from @base to @limit.
- */
-static int __init __dma_contiguous_reserve_area(phys_addr_t size,
-				phys_addr_t base, phys_addr_t limit,
-				phys_addr_t alignment, int order_per_bit,
-				struct cma **res_cma, bool fixed)
-{
-	struct cma *cma = &cma_areas[cma_area_count];
-	int ret = 0;
-
-	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
-		__func__, (unsigned long)size, (unsigned long)base,
-		(unsigned long)limit, (unsigned long)alignment);
-
-	/* Sanity checks */
-	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
-		pr_err("%s(): Not enough slots for CMA reserved regions!\n",
-			__func__);
-		return -ENOSPC;
-	}
-
-	if (!size)
-		return -EINVAL;
-
-	if (alignment && !is_power_of_2(alignment))
-		return -EINVAL;
-
-	/*
-	 * Sanitise input arguments.
-	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
-	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
-	 * and CMA property will be broken.
-	 */
-	alignment = max(alignment,
-		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
-	base = ALIGN(base, alignment);
-	size = ALIGN(size, alignment);
-	limit &= ~(alignment - 1);
-	/* size should be aligned with order_per_bit */
-	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit));
-
-	/* Reserve memory */
-	if (base && fixed) {
-		if (memblock_is_region_reserved(base, size) ||
-		    memblock_reserve(base, size) < 0) {
-			ret = -EBUSY;
-			goto err;
-		}
-	} else {
-		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
-							limit);
-		if (!addr) {
-			ret = -ENOMEM;
-			goto err;
-		} else {
-			base = addr;
-		}
-	}
-
-	/*
-	 * Each reserved area must be initialised later, when more kernel
-	 * subsystems (like slab allocator) are available.
-	 */
-	cma->base_pfn = PFN_DOWN(base);
-	cma->count = size >> PAGE_SHIFT;
-	cma->order_per_bit = order_per_bit;
-	*res_cma = cma;
-	cma_area_count++;
-
-	pr_info("%s(): reserved %ld MiB at %08lx\n",
-		__func__, (unsigned long)size / SZ_1M, (unsigned long)base);
-	return 0;
-
-err:
-	pr_err("%s(): failed to reserve %ld MiB\n",
-		__func__, (unsigned long)size / SZ_1M);
-	return ret;
-}
-
 int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
 				       phys_addr_t limit, struct cma **res_cma,
 				       bool fixed)
 {
 	int ret;
 
-	ret = __dma_contiguous_reserve_area(size, base, limit, 0, 0,
-						res_cma, fixed);
+	ret = cma_declare_contiguous(size, base, limit, 0, 0, res_cma, fixed);
 	if (ret)
 		return ret;
 
@@ -358,124 +159,17 @@  int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
 	return 0;
 }
 
-/**
- * dma_alloc_from_contiguous() - allocate pages from contiguous area
- * @dev:   Pointer to device for which the allocation is performed.
- * @count: Requested number of pages.
- * @align: Requested alignment of pages (in PAGE_SIZE order).
- *
- * This function allocates memory buffer for specified device. It uses
- * device specific contiguous memory area if available or the default
- * global one. Requires architecture specific dev_get_cma_area() helper
- * function.
- */
-static struct page *__dma_alloc_from_contiguous(struct cma *cma, int count,
-				       unsigned int align)
-{
-	unsigned long mask, pfn, start = 0;
-	unsigned long bitmap_maxno, bitmapno, nr_bits;
-	struct page *page = NULL;
-	int ret;
-
-	if (!cma || !cma->count)
-		return NULL;
-
-	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
-		 count, align);
-
-	if (!count)
-		return NULL;
-
-	mask = cma_bitmap_aligned_mask(cma, align);
-	bitmap_maxno = cma_bitmap_maxno(cma);
-	nr_bits = cma_bitmap_pages_to_bits(cma, count);
-
-	for (;;) {
-		mutex_lock(&cma->lock);
-		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
-					bitmap_maxno, start, nr_bits, mask);
-		if (bitmapno >= bitmap_maxno) {
-			mutex_unlock(&cma->lock);
-			break;
-		}
-		bitmap_set(cma->bitmap, bitmapno, nr_bits);
-		/*
-		 * It's safe to drop the lock here. We've marked this region for
-		 * our exclusive use. If the migration fails we will take the
-		 * lock again and unmark it.
-		 */
-		mutex_unlock(&cma->lock);
-
-		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
-		mutex_lock(&cma_mutex);
-		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
-		mutex_unlock(&cma_mutex);
-		if (ret == 0) {
-			page = pfn_to_page(pfn);
-			break;
-		} else if (ret != -EBUSY) {
-			clear_cma_bitmap(cma, pfn, count);
-			break;
-		}
-		clear_cma_bitmap(cma, pfn, count);
-		pr_debug("%s(): memory range at %p is busy, retrying\n",
-			 __func__, pfn_to_page(pfn));
-		/* try again with a bit different memory target */
-		start = bitmapno + mask + 1;
-	}
-
-	pr_debug("%s(): returned %p\n", __func__, page);
-	return page;
-}
-
 struct page *dma_alloc_from_contiguous(struct device *dev, int count,
 				       unsigned int align)
 {
-	struct cma *cma = dev_get_cma_area(dev);
-
 	if (align > CONFIG_CMA_ALIGNMENT)
 		align = CONFIG_CMA_ALIGNMENT;
 
-	return __dma_alloc_from_contiguous(cma, count, align);
-}
-
-/**
- * dma_release_from_contiguous() - release allocated pages
- * @dev:   Pointer to device for which the pages were allocated.
- * @pages: Allocated pages.
- * @count: Number of allocated pages.
- *
- * This function releases memory allocated by dma_alloc_from_contiguous().
- * It returns false when provided pages do not belong to contiguous area and
- * true otherwise.
- */
-static bool __dma_release_from_contiguous(struct cma *cma, struct page *pages,
-				 int count)
-{
-	unsigned long pfn;
-
-	if (!cma || !pages)
-		return false;
-
-	pr_debug("%s(page %p)\n", __func__, (void *)pages);
-
-	pfn = page_to_pfn(pages);
-
-	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
-		return false;
-
-	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
-
-	free_contig_range(pfn, count);
-	clear_cma_bitmap(cma, pfn, count);
-
-	return true;
+	return cma_alloc(dev_get_cma_area(dev), count, align);
 }
 
 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
 				 int count)
 {
-	struct cma *cma = dev_get_cma_area(dev);
-
-	return __dma_release_from_contiguous(cma, pages, count);
+	return cma_release(dev_get_cma_area(dev), pages, count);
 }
diff --git a/include/linux/cma.h b/include/linux/cma.h
new file mode 100644
index 0000000..e38efe9
--- /dev/null
+++ b/include/linux/cma.h
@@ -0,0 +1,12 @@ 
+#ifndef __CMA_H__
+#define __CMA_H__
+
+struct cma;
+
+extern int __init cma_declare_contiguous(phys_addr_t size,
+				phys_addr_t base, phys_addr_t limit,
+				phys_addr_t alignment, int order_per_bit,
+				struct cma **res_cma, bool fixed);
+extern struct page *cma_alloc(struct cma *cma, int count, unsigned int align);
+extern bool cma_release(struct cma *cma, struct page *pages, int count);
+#endif
diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h
index 772eab5..a40c1f3 100644
--- a/include/linux/dma-contiguous.h
+++ b/include/linux/dma-contiguous.h
@@ -53,9 +53,10 @@ 
 
 #ifdef __KERNEL__
 
+#include <linux/device.h>
+
 struct cma;
 struct page;
-struct device;
 
 #ifdef CONFIG_DMA_CMA
 
diff --git a/mm/Kconfig b/mm/Kconfig
index 3e9977a..f4899ec 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -508,6 +508,17 @@  config CMA_DEBUG
 	  processing calls such as dma_alloc_from_contiguous().
 	  This option does not affect warning and error messages.
 
+config CMA_AREAS
+	int "Maximum count of the CMA areas"
+	depends on CMA
+	default 7
+	help
+	  CMA allows to create CMA areas for particular purpose, mainly,
+	  used as device private area. This parameter sets the maximum
+	  number of CMA area in the system.
+
+	  If unsure, leave the default value "7".
+
 config ZBUD
 	tristate
 	default n
diff --git a/mm/Makefile b/mm/Makefile
index 1eaa70b..bc0422b 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -62,3 +62,4 @@  obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
 obj-$(CONFIG_ZBUD)	+= zbud.o
 obj-$(CONFIG_ZSMALLOC)	+= zsmalloc.o
 obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
+obj-$(CONFIG_CMA)	+= cma.o
diff --git a/mm/cma.c b/mm/cma.c
new file mode 100644
index 0000000..1e1b017
--- /dev/null
+++ b/mm/cma.c
@@ -0,0 +1,330 @@ 
+/*
+ * Contiguous Memory Allocator
+ *
+ * Copyright (c) 2010-2011 by Samsung Electronics.
+ * Copyright IBM Corporation, 2013
+ * Copyright LG Electronics Inc., 2014
+ * Written by:
+ *	Marek Szyprowski <m.szyprowski@samsung.com>
+ *	Michal Nazarewicz <mina86@mina86.com>
+ *	Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *	Joonsoo Kim <iamjoonsoo.kim@lge.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License or (at your optional) any later version of the license.
+ */
+
+#define pr_fmt(fmt) "cma: " fmt
+
+#ifdef CONFIG_CMA_DEBUG
+#ifndef DEBUG
+#  define DEBUG
+#endif
+#endif
+
+#include <linux/memblock.h>
+#include <linux/err.h>
+#include <linux/mm.h>
+#include <linux/mutex.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+
+struct cma {
+	unsigned long	base_pfn;
+	unsigned long	count;
+	unsigned long	*bitmap;
+	int order_per_bit; /* Order of pages represented by one bit */
+	struct mutex	lock;
+};
+
+/*
+ * There is always at least global CMA area and a few optional
+ * areas configured in kernel .config.
+ */
+#define MAX_CMA_AREAS	(1 + CONFIG_CMA_AREAS)
+
+static struct cma cma_areas[MAX_CMA_AREAS];
+static unsigned cma_area_count;
+static DEFINE_MUTEX(cma_mutex);
+
+static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
+{
+	return (1 << (align_order >> cma->order_per_bit)) - 1;
+}
+
+static unsigned long cma_bitmap_maxno(struct cma *cma)
+{
+	return cma->count >> cma->order_per_bit;
+}
+
+static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
+						unsigned long pages)
+{
+	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
+}
+
+static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
+{
+	unsigned long bitmapno, nr_bits;
+
+	bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
+	nr_bits = cma_bitmap_pages_to_bits(cma, count);
+
+	mutex_lock(&cma->lock);
+	bitmap_clear(cma->bitmap, bitmapno, nr_bits);
+	mutex_unlock(&cma->lock);
+}
+
+static int __init cma_activate_area(struct cma *cma)
+{
+	int bitmap_maxno = cma_bitmap_maxno(cma);
+	int bitmap_size = BITS_TO_LONGS(bitmap_maxno) * sizeof(long);
+	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
+	unsigned i = cma->count >> pageblock_order;
+	struct zone *zone;
+
+	pr_debug("%s()\n", __func__);
+
+	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
+	if (!cma->bitmap)
+		return -ENOMEM;
+
+	WARN_ON_ONCE(!pfn_valid(pfn));
+	zone = page_zone(pfn_to_page(pfn));
+
+	do {
+		unsigned j;
+
+		base_pfn = pfn;
+		for (j = pageblock_nr_pages; j; --j, pfn++) {
+			WARN_ON_ONCE(!pfn_valid(pfn));
+			/*
+			 * alloc_contig_range requires the pfn range
+			 * specified to be in the same zone. Make this
+			 * simple by forcing the entire CMA resv range
+			 * to be in the same zone.
+			 */
+			if (page_zone(pfn_to_page(pfn)) != zone)
+				goto err;
+		}
+		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
+	} while (--i);
+
+	mutex_init(&cma->lock);
+	return 0;
+
+err:
+	kfree(cma->bitmap);
+	return -EINVAL;
+}
+
+static int __init cma_init_reserved_areas(void)
+{
+	int i;
+
+	for (i = 0; i < cma_area_count; i++) {
+		int ret = cma_activate_area(&cma_areas[i]);
+
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+core_initcall(cma_init_reserved_areas);
+
+/**
+ * cma_declare_contiguous() - reserve custom contiguous area
+ * @size: Size of the reserved area (in bytes),
+ * @base: Base address of the reserved area optional, use 0 for any
+ * @limit: End address of the reserved memory (optional, 0 for any).
+ * @alignment: Alignment for the contiguous memory area, should be power of 2
+ * @order_per_bit: Order of pages represented by one bit on bitmap.
+ * @res_cma: Pointer to store the created cma region.
+ * @fixed: hint about where to place the reserved area
+ *
+ * This function reserves memory from early allocator. It should be
+ * called by arch specific code once the early allocator (memblock or bootmem)
+ * has been activated and all other subsystems have already allocated/reserved
+ * memory. This function allows to create custom reserved areas.
+ *
+ * If @fixed is true, reserve contiguous area at exactly @base.  If false,
+ * reserve in range from @base to @limit.
+ */
+int __init cma_declare_contiguous(phys_addr_t size,
+				phys_addr_t base, phys_addr_t limit,
+				phys_addr_t alignment, int order_per_bit,
+				struct cma **res_cma, bool fixed)
+{
+	struct cma *cma = &cma_areas[cma_area_count];
+	int ret = 0;
+
+	pr_debug("%s(size %lx, base %08lx, limit %08lx alignment %08lx)\n",
+		__func__, (unsigned long)size, (unsigned long)base,
+		(unsigned long)limit, (unsigned long)alignment);
+
+	/* Sanity checks */
+	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
+		pr_err("%s(): Not enough slots for CMA reserved regions!\n",
+			__func__);
+		return -ENOSPC;
+	}
+
+	if (!size)
+		return -EINVAL;
+
+	if (alignment && !is_power_of_2(alignment))
+		return -EINVAL;
+
+	/*
+	 * Sanitise input arguments.
+	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
+	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
+	 * and CMA property will be broken.
+	 */
+	alignment = max(alignment,
+		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
+	base = ALIGN(base, alignment);
+	size = ALIGN(size, alignment);
+	limit &= ~(alignment - 1);
+	/* size should be aligned with order_per_bit */
+	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit));
+
+	/* Reserve memory */
+	if (base && fixed) {
+		if (memblock_is_region_reserved(base, size) ||
+		    memblock_reserve(base, size) < 0) {
+			ret = -EBUSY;
+			goto err;
+		}
+	} else {
+		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
+							limit);
+		if (!addr) {
+			ret = -ENOMEM;
+			goto err;
+		} else {
+			base = addr;
+		}
+	}
+
+	/*
+	 * Each reserved area must be initialised later, when more kernel
+	 * subsystems (like slab allocator) are available.
+	 */
+	cma->base_pfn = PFN_DOWN(base);
+	cma->count = size >> PAGE_SHIFT;
+	cma->order_per_bit = order_per_bit;
+	*res_cma = cma;
+	cma_area_count++;
+
+	pr_info("%s(): reserved %ld MiB at %08lx\n",
+		__func__, (unsigned long)size / SZ_1M, (unsigned long)base);
+	return 0;
+
+err:
+	pr_err("%s(): failed to reserve %ld MiB\n",
+		__func__, (unsigned long)size / SZ_1M);
+	return ret;
+}
+
+/**
+ * cma_alloc() - allocate pages from contiguous area
+ * @cma:   Contiguous memory region for which the allocation is performed.
+ * @count: Requested number of pages.
+ * @align: Requested alignment of pages (in PAGE_SIZE order).
+ *
+ * This function allocates part of contiguous memory on specific
+ * contiguous memory area.
+ */
+struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
+{
+	unsigned long mask, pfn, start = 0;
+	unsigned long bitmap_maxno, bitmapno, nr_bits;
+	struct page *page = NULL;
+	int ret;
+
+	if (!cma || !cma->count)
+		return NULL;
+
+	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
+		 count, align);
+
+	if (!count)
+		return NULL;
+
+	mask = cma_bitmap_aligned_mask(cma, align);
+	bitmap_maxno = cma_bitmap_maxno(cma);
+	nr_bits = cma_bitmap_pages_to_bits(cma, count);
+
+	for (;;) {
+		mutex_lock(&cma->lock);
+		bitmapno = bitmap_find_next_zero_area(cma->bitmap,
+					bitmap_maxno, start, nr_bits, mask);
+		if (bitmapno >= bitmap_maxno) {
+			mutex_unlock(&cma->lock);
+			break;
+		}
+		bitmap_set(cma->bitmap, bitmapno, nr_bits);
+		/*
+		 * It's safe to drop the lock here. We've marked this region for
+		 * our exclusive use. If the migration fails we will take the
+		 * lock again and unmark it.
+		 */
+		mutex_unlock(&cma->lock);
+
+		pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
+		mutex_lock(&cma_mutex);
+		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
+		mutex_unlock(&cma_mutex);
+		if (ret == 0) {
+			page = pfn_to_page(pfn);
+			break;
+		} else if (ret != -EBUSY) {
+			clear_cma_bitmap(cma, pfn, count);
+			break;
+		}
+		clear_cma_bitmap(cma, pfn, count);
+		pr_debug("%s(): memory range at %p is busy, retrying\n",
+			 __func__, pfn_to_page(pfn));
+		/* try again with a bit different memory target */
+		start = bitmapno + mask + 1;
+	}
+
+	pr_debug("%s(): returned %p\n", __func__, page);
+	return page;
+}
+
+/**
+ * cma_release() - release allocated pages
+ * @cma:   Contiguous memory region for which the allocation is performed.
+ * @pages: Allocated pages.
+ * @count: Number of allocated pages.
+ *
+ * This function releases memory allocated by alloc_cma().
+ * It returns false when provided pages do not belong to contiguous area and
+ * true otherwise.
+ */
+bool cma_release(struct cma *cma, struct page *pages, int count)
+{
+	unsigned long pfn;
+
+	if (!cma || !pages)
+		return false;
+
+	pr_debug("%s(page %p)\n", __func__, (void *)pages);
+
+	pfn = page_to_pfn(pages);
+
+	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
+		return false;
+
+	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
+
+	free_contig_range(pfn, count);
+	clear_cma_bitmap(cma, pfn, count);
+
+	return true;
+}