dm-mpath, scsi_dh: don't let dm detach device handlers

While allowing dm-mpath to attach device handlers is a functionality we need
for backwards compatibility reason there is no reason to reference count
them and detach them if dm-mpath stops using the device for some reason.

If the device handler works for the given device it can just stay attached,
and we can take the retain_hw_handler codepath.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Hannes Reinecke <hare@Suse.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

1 files changed, 6 insertions, 15 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index eff7bdd7731d..a9f58fdb5d69 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -159,12 +159,9 @@ static struct priority_group *alloc_priority_group(void)
 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 {
 	struct pgpath *pgpath, *tmp;
-	struct multipath *m = ti->private;
 
 	list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 		list_del(&pgpath->list);
-		if (m->hw_handler_name)
-			scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 		dm_put_device(ti, pgpath->path.dev);
 		free_pgpath(pgpath);
 	}
@@ -580,6 +577,7 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps
 		q = bdev_get_queue(p->path.dev->bdev);
 
 	if (m->retain_attached_hw_handler) {
+retain:
 		attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 		if (attached_handler_name) {
 			/*
@@ -599,20 +597,14 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps
 	}
 
 	if (m->hw_handler_name) {
-		/*
-		 * Increments scsi_dh reference, even when using an
-		 * already-attached handler.
-		 */
 		r = scsi_dh_attach(q, m->hw_handler_name);
 		if (r == -EBUSY) {
-			/*
-			 * Already attached to different hw_handler:
-			 * try to reattach with correct one.
-			 */
-			scsi_dh_detach(q);
-			r = scsi_dh_attach(q, m->hw_handler_name);
-		}
+			char b[BDEVNAME_SIZE];
 
+			printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
+				bdevname(p->path.dev->bdev, b));
+			goto retain;
+		}
 		if (r < 0) {
 			ti->error = "error attaching hardware handler";
 			dm_put_device(ti, p->path.dev);
@@ -624,7 +616,6 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps
 			if (r < 0) {
 				ti->error = "unable to set hardware "
 							"handler parameters";
-				scsi_dh_detach(q);
 				dm_put_device(ti, p->path.dev);
 				goto bad;
 			}