[PATCH] mm/thp: Do not wait for lock_page() in deferred_split_scan()

[Kirill A. Shutemov]

deferred_split_scan() 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 <kirill.shute...@linux.intel.com>
---
 mm/huge_memory.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 87ab9b8f56b5..529cf36b7edb 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2783,11 +2783,13 @@ static unsigned long deferred_split_scan(struct 
shrinker *shrink,
 
        list_for_each_safe(pos, next, &list) {
                page = list_entry((void *)pos, struct page, mapping);
-               lock_page(page);
+               if (!trylock_page(page))
+                       goto next;
                /* split_huge_page() removes page from list on success */
                if (!split_huge_page(page))
                        split++;
                unlock_page(page);
+next:
                put_page(page);
        }
 
-- 
2.16.1