mm/shmem: do not wait for lock_page() in shmem_unused_huge_shrink()
authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Thu, 22 Mar 2018 23:17:35 +0000 (16:17 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 23 Mar 2018 00:07:01 +0000 (17:07 -0700)
commitb3cd54b257ad95d344d121dc563d943ca39b0921
tree49b4df8b32b64f2bdbb00fc2737ff3819051c758
parentfa41b900c30b45fab03783724932dc30cd46a6be
mm/shmem: do not wait for lock_page() in shmem_unused_huge_shrink()

shmem_unused_huge_shrink() gets called from reclaim path.  Waiting for
page lock may lead to deadlock there.

There was a bug report that may be attributed to this:

  http://lkml.kernel.org/r/alpine.LRH.2.11.1801242349220.30642@mail.ewheeler.net

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.

We can test for the PageTransHuge() outside the page lock as we only
need protection against splitting the page under us.  Holding pin oni
the page is enough for this.

Link: http://lkml.kernel.org/r/20180316210830.43738-1-kirill.shutemov@linux.intel.com
Fixes: 779750d20b93 ("shmem: split huge pages beyond i_size under memory pressure")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Eric Wheeler <linux-mm@lists.ewheeler.net>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org> [4.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/shmem.c