Patchwork sparc/srmmu: clear trailing edge of bitmap properly

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Submitter Akinobu Mita
Date March 29, 2013, 1:44 p.m.
Message ID <1364564684-15469-1-git-send-email-akinobu.mita@gmail.com>
Download mbox | patch
Permalink /patch/232410/
State Accepted
Delegated to: David Miller
Headers show

Comments

Akinobu Mita - March 29, 2013, 1:44 p.m.
srmmu_nocache_bitmap is cleared by bit_map_init().  But bit_map_init()
attempts to clear by memset(), so it can't clear the trailing edge of
bitmap properly on big-endian architecture if the number of bits is not
a multiple of BITS_PER_LONG.

Actually, the number of bits in srmmu_nocache_bitmap is not always
a multiple of BITS_PER_LONG.  It is calculated as below:

        bitmap_bits = srmmu_nocache_size >> SRMMU_NOCACHE_BITMAP_SHIFT;

srmmu_nocache_size is decided proportionally by the amount of system RAM
and it is rounded to a multiple of PAGE_SIZE.  SRMMU_NOCACHE_BITMAP_SHIFT
is defined as (PAGE_SHIFT - 4).  So it can only be said that bitmap_bits
is a multiple of 16.

This fixes the problem by using bitmap_clear() instead of memset()
in bit_map_init() and this also uses BITS_TO_LONGS() to calculate correct
size at bitmap allocation time.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
---

This patch is a combination of the patches I sent:
"sparc: clear bitmap correctly in bit_map_init()" and
"sparc/srmmu: use BITS_TO_LONGS() to calculate bitmap size", but
the patch description is rewritten.

 arch/sparc/lib/bitext.c | 6 +-----
 arch/sparc/mm/srmmu.c   | 4 +++-
 2 files changed, 4 insertions(+), 6 deletions(-)
Sam Ravnborg - March 29, 2013, 2:45 p.m.
On Fri, Mar 29, 2013 at 10:44:43PM +0900, Akinobu Mita wrote:
> srmmu_nocache_bitmap is cleared by bit_map_init().  But bit_map_init()
> attempts to clear by memset(), so it can't clear the trailing edge of
> bitmap properly on big-endian architecture if the number of bits is not
> a multiple of BITS_PER_LONG.
> 
> Actually, the number of bits in srmmu_nocache_bitmap is not always
> a multiple of BITS_PER_LONG.  It is calculated as below:
> 
>         bitmap_bits = srmmu_nocache_size >> SRMMU_NOCACHE_BITMAP_SHIFT;
> 
> srmmu_nocache_size is decided proportionally by the amount of system RAM
> and it is rounded to a multiple of PAGE_SIZE.  SRMMU_NOCACHE_BITMAP_SHIFT
> is defined as (PAGE_SHIFT - 4).  So it can only be said that bitmap_bits
> is a multiple of 16.
> 
> This fixes the problem by using bitmap_clear() instead of memset()
> in bit_map_init() and this also uses BITS_TO_LONGS() to calculate correct
> size at bitmap allocation time.
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: sparclinux@vger.kernel.org
> ---
> 
> This patch is a combination of the patches I sent:
> "sparc: clear bitmap correctly in bit_map_init()" and
> "sparc/srmmu: use BITS_TO_LONGS() to calculate bitmap size", but
> the patch description is rewritten.
> 
>  arch/sparc/lib/bitext.c | 6 +-----
>  arch/sparc/mm/srmmu.c   | 4 +++-
>  2 files changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/sparc/lib/bitext.c b/arch/sparc/lib/bitext.c
> index d516fda..04d8bad 100644
> --- a/arch/sparc/lib/bitext.c
> +++ b/arch/sparc/lib/bitext.c
> @@ -111,11 +111,7 @@ void bit_map_clear(struct bit_map *t, int offset, int len)
>  
>  void bit_map_init(struct bit_map *t, unsigned long *map, int size)
>  {
> -
> -	if ((size & 07) != 0)
> -		BUG();
> -	memset(map, 0, size>>3);
> -
> +	bitmap_zero(map, size);
>  	memset(t, 0, sizeof *t);
>  	spin_lock_init(&t->lock);
>  	t->map = map;

This mixes sparc internal bit_map functions with lib/bitmap functions.
Please do not do this.


> diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
> index c38bb72..036c279 100644
> --- a/arch/sparc/mm/srmmu.c
> +++ b/arch/sparc/mm/srmmu.c
> @@ -280,7 +280,9 @@ static void __init srmmu_nocache_init(void)
>  		SRMMU_NOCACHE_ALIGN_MAX, 0UL);
>  	memset(srmmu_nocache_pool, 0, srmmu_nocache_size);
>  
> -	srmmu_nocache_bitmap = __alloc_bootmem(bitmap_bits >> 3, SMP_CACHE_BYTES, 0UL);
> +	srmmu_nocache_bitmap =
> +		__alloc_bootmem(BITS_TO_LONGS(bitmap_bits) * sizeof(long),
> +				SMP_CACHE_BYTES, 0UL);

Anything that touches the sparc32 nocache stuff should improve read-ability
or fix real bugs. This does neither - so I prefer to leave it as is.

	Sam
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David Miller - March 31, 2013, 11:31 p.m.
From: Akinobu Mita <akinobu.mita@gmail.com>
Date: Fri, 29 Mar 2013 22:44:43 +0900

> srmmu_nocache_bitmap is cleared by bit_map_init().  But bit_map_init()
> attempts to clear by memset(), so it can't clear the trailing edge of
> bitmap properly on big-endian architecture if the number of bits is not
> a multiple of BITS_PER_LONG.
> 
> Actually, the number of bits in srmmu_nocache_bitmap is not always
> a multiple of BITS_PER_LONG.  It is calculated as below:
> 
>         bitmap_bits = srmmu_nocache_size >> SRMMU_NOCACHE_BITMAP_SHIFT;
> 
> srmmu_nocache_size is decided proportionally by the amount of system RAM
> and it is rounded to a multiple of PAGE_SIZE.  SRMMU_NOCACHE_BITMAP_SHIFT
> is defined as (PAGE_SHIFT - 4).  So it can only be said that bitmap_bits
> is a multiple of 16.
> 
> This fixes the problem by using bitmap_clear() instead of memset()
> in bit_map_init() and this also uses BITS_TO_LONGS() to calculate correct
> size at bitmap allocation time.
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>

Applied.
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Patch

diff --git a/arch/sparc/lib/bitext.c b/arch/sparc/lib/bitext.c
index d516fda..04d8bad 100644
--- a/arch/sparc/lib/bitext.c
+++ b/arch/sparc/lib/bitext.c
@@ -111,11 +111,7 @@  void bit_map_clear(struct bit_map *t, int offset, int len)
 
 void bit_map_init(struct bit_map *t, unsigned long *map, int size)
 {
-
-	if ((size & 07) != 0)
-		BUG();
-	memset(map, 0, size>>3);
-
+	bitmap_zero(map, size);
 	memset(t, 0, sizeof *t);
 	spin_lock_init(&t->lock);
 	t->map = map;
diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
index c38bb72..036c279 100644
--- a/arch/sparc/mm/srmmu.c
+++ b/arch/sparc/mm/srmmu.c
@@ -280,7 +280,9 @@  static void __init srmmu_nocache_init(void)
 		SRMMU_NOCACHE_ALIGN_MAX, 0UL);
 	memset(srmmu_nocache_pool, 0, srmmu_nocache_size);
 
-	srmmu_nocache_bitmap = __alloc_bootmem(bitmap_bits >> 3, SMP_CACHE_BYTES, 0UL);
+	srmmu_nocache_bitmap =
+		__alloc_bootmem(BITS_TO_LONGS(bitmap_bits) * sizeof(long),
+				SMP_CACHE_BYTES, 0UL);
 	bit_map_init(&srmmu_nocache_map, srmmu_nocache_bitmap, bitmap_bits);
 
 	srmmu_swapper_pg_dir = __srmmu_get_nocache(SRMMU_PGD_TABLE_SIZE, SRMMU_PGD_TABLE_SIZE);