shmem_unused_huge_shrink() gets called from reclaim path. Waiting for page lock may lead to deadlock there.
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. Signed-off-by: Kirill A. Shutemov <[email protected]> Fixes: 779750d20b93 ("shmem: split huge pages beyond i_size under memory pressure") Cc: [email protected] # v4.8+ --- mm/shmem.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 1907688b75ee..2afe809d4bd4 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -498,31 +498,42 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo, continue; } - 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); } -- 2.16.1
