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-mpath.c b/drivers/md/dm-mpath.c
index bdf26f5..5adede1 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1561,7 +1561,6 @@
unsigned long flags;
int r;
-again:
bdev = NULL;
mode = 0;
r = 0;
@@ -1579,7 +1578,7 @@
}
if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path))
- r = -EAGAIN;
+ r = -ENOTCONN;
else if (!bdev)
r = -EIO;
@@ -1591,11 +1590,8 @@
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);
}