Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hannes Reinecke , Mike Snitzer , Alasdair G Kergon Subject: [ 63/99] dm mpath: fix ioctl deadlock when no paths Date: Fri, 2 Aug 2013 18:08:16 +0800 Message-Id: <20130802100234.817702880@linuxfoundation.org> In-Reply-To: <20130802100225.478715166@linuxfoundation.org> References: <20130802100225.478715166@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hannes Reinecke commit 6c182cd88d179cbbd06f4f8a8a19b6977940753f upstream. 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 Signed-off-by: Alasdair G Kergon Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-mpath.c | 8 ++------ drivers/md/dm.c | 9 ++++++++- 2 files changed, 10 insertions(+), 7 deletions(-) --- a/drivers/md/dm-mpath.c +++ b/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); } --- a/drivers/md/dm.c +++ b/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; }