Commit 68faed63 authored by Weijie Yang's avatar Weijie Yang Committed by Linus Torvalds

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.

[ coding-style fixes]
Signed-off-by: default avatarWeijie Yang <>
Acked-by: default avatarMichal Nazarewicz <>
Cc: Joonsoo Kim <>
Cc: "Aneesh Kumar K.V" <>
Cc: <>	[3.17]
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 85c9f4b0
......@@ -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)
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