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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>
This commit is contained in:
Hannes Reinecke 2013-07-10 23:41:15 +01:00 committed by Alasdair G Kergon
parent 8bb495e3f0
commit 6c182cd88d
2 changed files with 10 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/md/dm-mpath.c
View File

@ -1561,7 +1561,6 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
unsigned long flags; unsigned long flags;
int r; int r;
again:
bdev = NULL; bdev = NULL;
mode = 0; mode = 0;
r = 0; r = 0;
@ -1579,7 +1578,7 @@ again:
} }
if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path)) if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path))
r = -EAGAIN; r = -ENOTCONN;
else if (!bdev) else if (!bdev)
r = -EIO; r = -EIO;
@ -1591,11 +1590,8 @@ again:
if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT) if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
r = scsi_verify_blk_ioctl(NULL, cmd); 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); queue_work(kmultipathd, &m->process_queued_ios);
msleep(10);
goto again;
}
return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg); return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
} }

9
drivers/md/dm.c
View File

@ -386,10 +386,12 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
unsigned int cmd, unsigned long arg) unsigned int cmd, unsigned long arg)
{ {
struct mapped_device *md = bdev->bd_disk->private_data; 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; struct dm_target *tgt;
int r = -ENOTTY; int r = -ENOTTY;
retry:
map = dm_get_live_table(md);
if (!map || !dm_table_get_size(map)) if (!map || !dm_table_get_size(map))
goto out; goto out;
@ -410,6 +412,11 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
out: out:
dm_table_put(map); dm_table_put(map);
if (r == -ENOTCONN) {
msleep(10);
goto retry;
}
return r; return r;
} }