aio: make aio_setup_ring killable

aio_setup_ring waits for mmap_sem in writable mode.  If the waiting task
gets killed by the oom killer it would block oom_reaper from
asynchronous address space reclaim and reduce the chances of timely OOM
resolving.  Wait for the lock in the killable mode and return with EINTR
if the task got killed while waiting.  This will also expedite the
return to the userspace and do_exit.

Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Benamin LaHaise <bcrl@kvack.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/aio.c b/fs/aio.c
index a6deaa7..fb8e45b 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -496,7 +496,12 @@ static int aio_setup_ring(struct kioctx *ctx)
 	ctx->mmap_size = nr_pages * PAGE_SIZE;
 	pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
 
-	down_write(&mm->mmap_sem);
+	if (down_write_killable(&mm->mmap_sem)) {
+		ctx->mmap_size = 0;
+		aio_free_ring(ctx);
+		return -EINTR;
+	}
+
 	ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
 				       PROT_READ | PROT_WRITE,
 				       MAP_SHARED, 0, &unused);