patches/kernel/0023-mm-thp-Do-not-wait-for-lock_page-in-deferred_split_s.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
   3 Date: Thu, 15 Mar 2018 18:07:47 +0300
   4 Subject: [PATCH] mm/thp: Do not wait for lock_page() in deferred_split_scan()
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 deferred_split_scan() gets called from reclaim path. Waiting for page
  10 lock may lead to deadlock there.
  11
  12 Replace lock_page() with trylock_page() and skip the page if we failed
  13 to lock it. We will get to the page on the next scan.
  14
  15 Fixes: 9a982250f773 ("thp: introduce deferred_split_huge_page()")
  16
  17 Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
  18 Acked-by: Michal Hocko <mhocko@suse.com>
  19 (cherry-picked from https://patchwork.kernel.org/patch/10284703/)
  20 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  21 ---
  22  mm/huge_memory.c | 4 +++-
  23  1 file changed, 3 insertions(+), 1 deletion(-)
  24
  25 diff --git a/mm/huge_memory.c b/mm/huge_memory.c
  26 index 8b887db33383..5c4093e0be8d 100644
  27 --- a/mm/huge_memory.c
  28 +++ b/mm/huge_memory.c
  29 @@ -2621,11 +2621,13 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
  30
  31         list_for_each_safe(pos, next, &list) {
  32                 page = list_entry((void *)pos, struct page, mapping);
  33 -               lock_page(page);
  34 +               if (!trylock_page(page))
  35 +                       goto next;
  36                 /* split_huge_page() removes page from list on success */
  37                 if (!split_huge_page(page))
  38                         split++;
  39                 unlock_page(page);
  40 +next:
  41                 put_page(page);
  42         }
  43
  44 --
  45 2.14.2
  46