From: Hannes Reinecke 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 Cc: Mike Snitzer Cc: stable@vger.kernel.org Signed-off-by: Alasdair G Kergon --- drivers/md/dm-mpath.c | 8 ++------ drivers/md/dm.c | 9 ++++++++- 2 files changed, 10 insertions(+), 7 deletions(-) Index: linux/drivers/md/dm-mpath.c =================================================================== --- linux.orig/drivers/md/dm-mpath.c +++ linux/drivers/md/dm-mpath.c @@ -1561,7 +1561,6 @@ static int multipath_ioctl(struct dm_tar unsigned long flags; int r; -again: bdev = NULL; mode = 0; r = 0; @@ -1579,7 +1578,7 @@ again: } if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path)) - r = -EAGAIN; + r = -ENOTCONN; else if (!bdev) r = -EIO; @@ -1591,11 +1590,8 @@ again: if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT) r = scsi_verify_blk_ioctl(NULL, cmd); - if (r == -EAGAIN && !fatal_signal_pending(current)) { + if (r == -ENOTCONN && !fatal_signal_pending(current)) queue_work(kmultipathd, &m->process_queued_ios); - msleep(10); - goto again; - } return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg); } Index: linux/drivers/md/dm.c =================================================================== --- linux.orig/drivers/md/dm.c +++ linux/drivers/md/dm.c @@ -386,10 +386,12 @@ static int dm_blk_ioctl(struct block_dev 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 @@ static int dm_blk_ioctl(struct block_dev out: dm_table_put(map); + if (r == -ENOTCONN) { + msleep(10); + goto retry; + } + return r; }