dm-ebs: fix prefetch-vs-suspend race

There's a possible race condition in dm-ebs - dm bufio prefetch may be in
progress while the device is suspended. Fix this by calling
dm_bufio_client_reset in the postsuspend hook.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org

Author: Mikulas Patocka

drivers/md/dm-ebs-target.c

@@ -390,6 +390,12 @@ static int ebs_map(struct dm_target *ti, struct bio *bio)
 	return DM_MAPIO_REMAPPED;
 }
 
+static void ebs_postsuspend(struct dm_target *ti)
+{
+	struct ebs_c *ec = ti->private;
+	dm_bufio_client_reset(ec->bufio);
+}
+
 static void ebs_status(struct dm_target *ti, status_type_t type,
 		       unsigned int status_flags, char *result, unsigned int maxlen)
 {
@@ -447,6 +453,7 @@ static struct target_type ebs_target = {
 	.ctr		 = ebs_ctr,
 	.dtr		 = ebs_dtr,
 	.map		 = ebs_map,
+	.postsuspend	 = ebs_postsuspend,
 	.status		 = ebs_status,
 	.io_hints	 = ebs_io_hints,
 	.prepare_ioctl	 = ebs_prepare_ioctl,