This is a note to let you know that I've just added the patch titled
dm mpath: fix ioctl deadlock when no paths
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dm-mpath-fix-ioctl-deadlock-when-no-paths.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6c182cd88d179cbbd06f4f8a8a19b6977940753f Mon Sep 17 00:00:00 2001
From: Hannes Reinecke <hare@xxxxxxx>
Date: Wed, 10 Jul 2013 23:41:15 +0100
Subject: dm mpath: fix ioctl deadlock when no paths
From: Hannes Reinecke <hare@xxxxxxx>
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 <hare@xxxxxxx>
Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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;
}
Patches currently in stable-queue which might be from hare@xxxxxxx are
queue-3.10/dm-mpath-fix-ioctl-deadlock-when-no-paths.patch
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