mm/cma: fix cma bitmap aligned mask computing

commit 68faed630fc151a7a1c4853df00fb3dcacf782b4 upstream.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/cma.c b/mm/cma.c
index c17751c0dcafb95eda9f41e9cdc9ce101edbebed..0ab564623ea843fe597d4f2f547a90b412c9aa5b 100644 (file)
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -57,7 +57,9 @@ 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)