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 <[email protected]>
Acked-by: Jeff Moyer <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Benamin LaHaise <[email protected]>
Cc: Alexander Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/aio.c b/fs/aio.c
index a6deaa78326d..fb8e45b88cd4 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);