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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2018-03-22 16:17:35 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-03-22 17:07:01 -0700
commitb3cd54b257ad95d344d121dc563d943ca39b0921 (patch)
tree49b4df8b32b64f2bdbb00fc2737ff3819051c758
parentfa41b900c30b45fab03783724932dc30cd46a6be (diff)
downloadlinux-stericsson-b3cd54b257ad95d344d121dc563d943ca39b0921.tar.gz
mm/shmem: do not wait for lock_page() in shmem_unused_huge_shrink()
shmem_unused_huge_shrink() gets called from reclaim path. Waiting for page lock may lead to deadlock there. There was a bug report that may be attributed to this: http://lkml.kernel.org/r/alpine.LRH.2.11.1801242349220.30642@mail.ewheeler.net Replace lock_page() with trylock_page() and skip the page if we failed to lock it. We will get to the page on the next scan. We can test for the PageTransHuge() outside the page lock as we only need protection against splitting the page under us. Holding pin oni the page is enough for this. Link: http://lkml.kernel.org/r/20180316210830.43738-1-kirill.shutemov@linux.intel.com Fixes: 779750d20b93 ("shmem: split huge pages beyond i_size under memory pressure") Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Eric Wheeler <linux-mm@lists.ewheeler.net> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> [4.8+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/shmem.c31
1 files changed, 20 insertions, 11 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index 1907688b75ee..b85919243399 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -493,36 +493,45 @@ next:
info = list_entry(pos, struct shmem_inode_info, shrinklist);
inode = &info->vfs_inode;
- if (nr_to_split && split >= nr_to_split) {
- iput(inode);
- continue;
- }
+ if (nr_to_split && split >= nr_to_split)
+ goto leave;
- page = find_lock_page(inode->i_mapping,
+ page = find_get_page(inode->i_mapping,
(inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT);
if (!page)
goto drop;
+ /* No huge page at the end of the file: nothing to split */
if (!PageTransHuge(page)) {
- unlock_page(page);
put_page(page);
goto drop;
}
+ /*
+ * Leave the inode on the list if we failed to lock
+ * the page at this time.
+ *
+ * Waiting for the lock may lead to deadlock in the
+ * reclaim path.
+ */
+ if (!trylock_page(page)) {
+ put_page(page);
+ goto leave;
+ }
+
ret = split_huge_page(page);
unlock_page(page);
put_page(page);
- if (ret) {
- /* split failed: leave it on the list */
- iput(inode);
- continue;
- }
+ /* If split failed leave the inode on the list */
+ if (ret)
+ goto leave;
split++;
drop:
list_del_init(&info->shrinklist);
removed++;
+leave:
iput(inode);
}