This is a note to let you know that I've just added the patch titled

mm/thp: do not wait for lock_page() in deferred_split_scan()

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: mm-thp-do-not-wait-for-lock_page-in-deferred_split_scan.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From fa41b900c30b45fab03783724932dc30cd46a6be Mon Sep 17 00:00:00 2001

From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Date: Thu, 22 Mar 2018 16:17:31 -0700 Subject: mm/thp: do not wait for lock_page() in deferred_split_scan()

From: Kirill A. Shutemov kirill.shutemov@linux.intel.com

commit fa41b900c30b45fab03783724932dc30cd46a6be upstream.

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.

Link: http://lkml.kernel.org/r/20180315150747.31945-1-kirill.shutemov@linux.intel.... Fixes: 9a982250f773 ("thp: introduce deferred_split_huge_page()") Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Acked-by: Michal Hocko mhocko@suse.com Cc: stable@vger.kernel.org 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

--- mm/huge_memory.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2279,11 +2279,13 @@ static unsigned long deferred_split_scan

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); }

Patches currently in stable-queue which might be from kirill.shutemov@linux.intel.com are

queue-4.9/mm-khugepaged.c-convert-vm_bug_on-to-collapse-fail.patch queue-4.9/mm-thp-do-not-wait-for-lock_page-in-deferred_split_scan.patch queue-4.9/mm-shmem-do-not-wait-for-lock_page-in-shmem_unused_huge_shrink.patch