From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Subject: mm/thp: do not wait for lock_page() in deferred_split_scan()

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 <> ---

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

diff -puN mm/huge_memory.c~mm-thp-do-not-wait-for-lock_page-in-deferred_split_scan mm/huge_memory.c --- a/mm/huge_memory.c~mm-thp-do-not-wait-for-lock_page-in-deferred_split_scan +++ a/mm/huge_memory.c @@ -2783,11 +2783,13 @@ 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); }

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