Commit 4cbf320b authored by Baolin Wang's avatar Baolin Wang Committed by Andrew Morton
Browse files

mm: shmem: fix incorrect aligned index when checking conflicts 

In the shmem_suitable_orders() function, xa_find() is used to check for
conflicts in the pagecache to select suitable huge orders.  However, when
checking each huge order in every loop, the aligned index is calculated
from the previous iteration, which may cause suitable huge orders to be
missed.

We should use the original index each time in the loop to calculate a new
aligned index for checking conflicts to avoid this issue.

Link: https://lkml.kernel.org/r/07433b0f16a152bffb8cee34934a5c040e8e2ad6.1722404078.git.baolin.wang@linux.alibaba.com


Fixes: e7a2ab7b ("mm: shmem: add mTHP support for anonymous shmem")
Signed-off-by: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Barry Song <21cnbao@gmail.com>
Cc: Gavin Shan <gshan@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b66b1b71

mm/shmem.c

+4 −3
Original line number Diff line number Diff line
@@ -1681,6 +1681,7 @@ static unsigned long shmem_suitable_orders(struct inode *inode, struct vm_fault 
					   unsigned long orders)

{

	struct vm_area_struct *vma = vmf->vma;

	pgoff_t aligned_index;

	unsigned long pages;

	int order;
@@ -1692,9 +1693,9 @@ static unsigned long shmem_suitable_orders(struct inode *inode, struct vm_fault 
	order = highest_order(orders);

	while (orders) {

		pages = 1UL << order;

		index = round_down(index, pages);

		if (!xa_find(&mapping->i_pages, &index,

			     index + pages - 1, XA_PRESENT))

		aligned_index = round_down(index, pages);

		if (!xa_find(&mapping->i_pages, &aligned_index,

			     aligned_index + pages - 1, XA_PRESENT))

			break;

		order = next_order(&orders, order);

	}