dm: free io_barrier after blk_cleanup_queue call

commit d09960b0032174eb493c4c13be5b9c9ef36dc9a7 upstream.

dm_old_request_fn() has paths that access md->io_barrier.  The party
destroying io_barrier should ensure that no future execution of
dm_old_request_fn() is possible.  Move io_barrier destruction to below
blk_cleanup_queue() to ensure this and avoid a NULL pointer crash during
request-based DM device shutdown.

Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 84aa8b1d048031d26f76d11972e8ba1e3449dfde..3384a3eef917bc3a98f4a1598e5629f705c309e2 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2260,8 +2260,6 @@ static void cleanup_mapped_device(struct mapped_device *md)
        if (md->bs)
                bioset_free(md->bs);
 
-       cleanup_srcu_struct(&md->io_barrier);
-
        if (md->disk) {
                spin_lock(&_minor_lock);
                md->disk->private_data = NULL;
@@ -2273,6 +2271,8 @@ static void cleanup_mapped_device(struct mapped_device *md)
        if (md->queue)
                blk_cleanup_queue(md->queue);
 
+       cleanup_srcu_struct(&md->io_barrier);
+
        if (md->bdev) {
                bdput(md->bdev);
                md->bdev = NULL;