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mm/cma: fix cma bitmap aligned mask computing 

The current cma bitmap aligned mask computation is incorrect.  It could
cause an unexpected alignment when using cma_alloc() if the wanted align
order is larger than cma->order_per_bit.

Take kvm for example (PAGE_SHIFT = 12), kvm_cma->order_per_bit is set to
6.  When kvm_alloc_rma() tries to alloc kvm_rma_pages, it will use 15 as
the expected align value.  After using the current implementation however,
we get 0 as cma bitmap aligned mask other than 511.

This patch fixes the cma bitmap aligned mask calculation.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Weijie Yang <weijie.yang@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org>	[3.17]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Weijie Yang 2014-10-13 15:51:03 -07:00 committed by Linus Torvalds
parent 85c9f4b04a
commit 68faed630f
1 changed files with 3 additions and 1 deletions
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4
mm/cma.c
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@ -58,7 +58,9 @@ unsigned long cma_get_size(struct cma *cma)
static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
{
return (1UL << (align_order >> cma->order_per_bit)) - 1;
if (align_order <= cma->order_per_bit)
return 0;
return (1UL << (align_order - cma->order_per_bit)) - 1;
}
static unsigned long cma_bitmap_maxno(struct cma *cma)