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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2018-03-22 16:17:35 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-28 18:39:22 +0200
commit8ab899550b9a7ab2eebf84c1a694aafbd1e2121f (patch)
treecc6f980e2cb7ca3ec57a5553740214a89ff8497f /mm
parent142d9dda9e3b55c2b4604bd3d90f3db1c3219e55 (diff)
mm/shmem: do not wait for lock_page() in shmem_unused_huge_shrink()
commit b3cd54b257ad95d344d121dc563d943ca39b0921 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/shmem.c31
1 files changed, 20 insertions, 11 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index 2123bfc39ef2..42ca5df2c0e3 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -466,36 +466,45 @@ 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);
}