Patchwork [2/8] v2 Add section count to memory_block struct

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Submitter Nathan Fontenot
Date Sept. 27, 2010, 7:22 p.m.
Message ID <4CA0EEF0.70402@austin.ibm.com>
Download mbox | patch
Permalink /patch/65909/
State Not Applicable
Headers show

Comments

Nathan Fontenot - Sept. 27, 2010, 7:22 p.m.
Add a section count property to the memory_block struct to track the number
of memory sections that have been added/removed from a memory block. This
allows us to know when the last memory section of a memory block has been
removed so we can remove the memory block.

Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com>

---
 drivers/base/memory.c  |   16 ++++++++++------
 include/linux/memory.h |    3 +++
 2 files changed, 13 insertions(+), 6 deletions(-)
holt@sgi.com - Sept. 28, 2010, 9:31 a.m.
In the next patch, you introduce a mutex for adding/removing memory blocks.
Is there really a need for this to be atomic?  If you reorder the patches
so the mutex comes first, would the atomic be needed any longer?

Robin

On Mon, Sep 27, 2010 at 02:22:24PM -0500, Nathan Fontenot wrote:
> Add a section count property to the memory_block struct to track the number
> of memory sections that have been added/removed from a memory block. This
> allows us to know when the last memory section of a memory block has been
> removed so we can remove the memory block.
> 
> Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com>
> 
> ---
>  drivers/base/memory.c  |   16 ++++++++++------
>  include/linux/memory.h |    3 +++
>  2 files changed, 13 insertions(+), 6 deletions(-)
> 
> Index: linux-next/drivers/base/memory.c
> ===================================================================
> --- linux-next.orig/drivers/base/memory.c	2010-09-27 09:17:20.000000000 -0500
> +++ linux-next/drivers/base/memory.c	2010-09-27 09:31:35.000000000 -0500
> @@ -478,6 +478,7 @@
>  
>  	mem->phys_index = __section_nr(section);
>  	mem->state = state;
> +	atomic_inc(&mem->section_count);
>  	mutex_init(&mem->state_mutex);
>  	start_pfn = section_nr_to_pfn(mem->phys_index);
>  	mem->phys_device = arch_get_memory_phys_device(start_pfn);
> @@ -505,12 +506,15 @@
>  	struct memory_block *mem;
>  
>  	mem = find_memory_block(section);
> -	unregister_mem_sect_under_nodes(mem);
> -	mem_remove_simple_file(mem, phys_index);
> -	mem_remove_simple_file(mem, state);
> -	mem_remove_simple_file(mem, phys_device);
> -	mem_remove_simple_file(mem, removable);
> -	unregister_memory(mem, section);
> +
> +	if (atomic_dec_and_test(&mem->section_count)) {
> +		unregister_mem_sect_under_nodes(mem);
> +		mem_remove_simple_file(mem, phys_index);
> +		mem_remove_simple_file(mem, state);
> +		mem_remove_simple_file(mem, phys_device);
> +		mem_remove_simple_file(mem, removable);
> +		unregister_memory(mem, section);
> +	}
>  
>  	return 0;
>  }
> Index: linux-next/include/linux/memory.h
> ===================================================================
> --- linux-next.orig/include/linux/memory.h	2010-09-27 09:17:20.000000000 -0500
> +++ linux-next/include/linux/memory.h	2010-09-27 09:22:56.000000000 -0500
> @@ -19,10 +19,13 @@
>  #include <linux/node.h>
>  #include <linux/compiler.h>
>  #include <linux/mutex.h>
> +#include <asm/atomic.h>
>  
>  struct memory_block {
>  	unsigned long phys_index;
>  	unsigned long state;
> +	atomic_t section_count;
> +
>  	/*
>  	 * This serializes all state change requests.  It isn't
>  	 * held during creation because the control files are
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
Nathan Fontenot - Sept. 28, 2010, 6:14 p.m.
On 09/28/2010 04:31 AM, Robin Holt wrote:
> In the next patch, you introduce a mutex for adding/removing memory blocks.
> Is there really a need for this to be atomic?  If you reorder the patches
> so the mutex comes first, would the atomic be needed any longer?
> 

I think you're right.  Looking at the code with all patches applied I am only
updating the atomic when holding the mem_sysfs_mutex.  I think the atomic
could safely be changed to a regular int.

-Nathan

> Robin
> 
> On Mon, Sep 27, 2010 at 02:22:24PM -0500, Nathan Fontenot wrote:
>> Add a section count property to the memory_block struct to track the number
>> of memory sections that have been added/removed from a memory block. This
>> allows us to know when the last memory section of a memory block has been
>> removed so we can remove the memory block.
>>
>> Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com>
>>
>> ---
>>  drivers/base/memory.c  |   16 ++++++++++------
>>  include/linux/memory.h |    3 +++
>>  2 files changed, 13 insertions(+), 6 deletions(-)
>>
>> Index: linux-next/drivers/base/memory.c
>> ===================================================================
>> --- linux-next.orig/drivers/base/memory.c	2010-09-27 09:17:20.000000000 -0500
>> +++ linux-next/drivers/base/memory.c	2010-09-27 09:31:35.000000000 -0500
>> @@ -478,6 +478,7 @@
>>  
>>  	mem->phys_index = __section_nr(section);
>>  	mem->state = state;
>> +	atomic_inc(&mem->section_count);
>>  	mutex_init(&mem->state_mutex);
>>  	start_pfn = section_nr_to_pfn(mem->phys_index);
>>  	mem->phys_device = arch_get_memory_phys_device(start_pfn);
>> @@ -505,12 +506,15 @@
>>  	struct memory_block *mem;
>>  
>>  	mem = find_memory_block(section);
>> -	unregister_mem_sect_under_nodes(mem);
>> -	mem_remove_simple_file(mem, phys_index);
>> -	mem_remove_simple_file(mem, state);
>> -	mem_remove_simple_file(mem, phys_device);
>> -	mem_remove_simple_file(mem, removable);
>> -	unregister_memory(mem, section);
>> +
>> +	if (atomic_dec_and_test(&mem->section_count)) {
>> +		unregister_mem_sect_under_nodes(mem);
>> +		mem_remove_simple_file(mem, phys_index);
>> +		mem_remove_simple_file(mem, state);
>> +		mem_remove_simple_file(mem, phys_device);
>> +		mem_remove_simple_file(mem, removable);
>> +		unregister_memory(mem, section);
>> +	}
>>  
>>  	return 0;
>>  }
>> Index: linux-next/include/linux/memory.h
>> ===================================================================
>> --- linux-next.orig/include/linux/memory.h	2010-09-27 09:17:20.000000000 -0500
>> +++ linux-next/include/linux/memory.h	2010-09-27 09:22:56.000000000 -0500
>> @@ -19,10 +19,13 @@
>>  #include <linux/node.h>
>>  #include <linux/compiler.h>
>>  #include <linux/mutex.h>
>> +#include <asm/atomic.h>
>>  
>>  struct memory_block {
>>  	unsigned long phys_index;
>>  	unsigned long state;
>> +	atomic_t section_count;
>> +
>>  	/*
>>  	 * This serializes all state change requests.  It isn't
>>  	 * held during creation because the control files are
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at  http://www.tux.org/lkml/

Patch

Index: linux-next/drivers/base/memory.c
===================================================================
--- linux-next.orig/drivers/base/memory.c	2010-09-27 09:17:20.000000000 -0500
+++ linux-next/drivers/base/memory.c	2010-09-27 09:31:35.000000000 -0500
@@ -478,6 +478,7 @@ 
 
 	mem->phys_index = __section_nr(section);
 	mem->state = state;
+	atomic_inc(&mem->section_count);
 	mutex_init(&mem->state_mutex);
 	start_pfn = section_nr_to_pfn(mem->phys_index);
 	mem->phys_device = arch_get_memory_phys_device(start_pfn);
@@ -505,12 +506,15 @@ 
 	struct memory_block *mem;
 
 	mem = find_memory_block(section);
-	unregister_mem_sect_under_nodes(mem);
-	mem_remove_simple_file(mem, phys_index);
-	mem_remove_simple_file(mem, state);
-	mem_remove_simple_file(mem, phys_device);
-	mem_remove_simple_file(mem, removable);
-	unregister_memory(mem, section);
+
+	if (atomic_dec_and_test(&mem->section_count)) {
+		unregister_mem_sect_under_nodes(mem);
+		mem_remove_simple_file(mem, phys_index);
+		mem_remove_simple_file(mem, state);
+		mem_remove_simple_file(mem, phys_device);
+		mem_remove_simple_file(mem, removable);
+		unregister_memory(mem, section);
+	}
 
 	return 0;
 }
Index: linux-next/include/linux/memory.h
===================================================================
--- linux-next.orig/include/linux/memory.h	2010-09-27 09:17:20.000000000 -0500
+++ linux-next/include/linux/memory.h	2010-09-27 09:22:56.000000000 -0500
@@ -19,10 +19,13 @@ 
 #include <linux/node.h>
 #include <linux/compiler.h>
 #include <linux/mutex.h>
+#include <asm/atomic.h>
 
 struct memory_block {
 	unsigned long phys_index;
 	unsigned long state;
+	atomic_t section_count;
+
 	/*
 	 * This serializes all state change requests.  It isn't
 	 * held during creation because the control files are