4.9-stable review patch. If anyone has any objections, please let me know.
------------------
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); }