dm mpath: fix ioctl deadlock when no paths
When multipath needs to retry an ioctl the reference to the
current live table needs to be dropped. Otherwise a deadlock
occurs when all paths are down:
- dm_blk_ioctl takes a reference to the current table
and spins in multipath_ioctl().
- A new table is being loaded, but upon resume the process
hangs in dm_table_destroy() waiting for references to
drop to zero.
With this patch the reference to the old table is dropped
prior to retry, thereby avoiding the deadlock.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index d5370a9..33f2010 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -386,10 +386,12 @@
unsigned int cmd, unsigned long arg)
{
struct mapped_device *md = bdev->bd_disk->private_data;
- struct dm_table *map = dm_get_live_table(md);
+ struct dm_table *map;
struct dm_target *tgt;
int r = -ENOTTY;
+retry:
+ map = dm_get_live_table(md);
if (!map || !dm_table_get_size(map))
goto out;
@@ -410,6 +412,11 @@
out:
dm_table_put(map);
+ if (r == -ENOTCONN) {
+ msleep(10);
+ goto retry;
+ }
+
return r;
}