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[3.8.y.z,extended,stable] Patch "dm mpath: fix ioctl deadlock when no paths" has been added to staging queue

Message ID 1374015244-28327-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa July 16, 2013, 10:54 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    dm mpath: fix ioctl deadlock when no paths

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.5.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From 5e3ddc032015ab632ce1936cc60607b22c158d93 Mon Sep 17 00:00:00 2001
From: Hannes Reinecke <hare@suse.de>
Date: Wed, 10 Jul 2013 23:41:15 +0100
Subject: dm mpath: fix ioctl deadlock when no paths

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@suse.de>
Cc: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/md/dm-mpath.c | 8 ++------
 drivers/md/dm.c       | 9 ++++++++-
 2 files changed, 10 insertions(+), 7 deletions(-)

--
1.8.1.2
diff mbox

Patch

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index d267bb5..9f330c1 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1560,7 +1560,6 @@  static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
 	unsigned long flags;
 	int r;

-again:
 	bdev = NULL;
 	mode = 0;
 	r = 0;
@@ -1578,7 +1577,7 @@  again:
 	}

 	if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path))
-		r = -EAGAIN;
+		r = -ENOTCONN;
 	else if (!bdev)
 		r = -EIO;

@@ -1590,11 +1589,8 @@  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);
 }
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 0d8f086..6a82721 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -404,10 +404,12 @@  static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
 			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;

@@ -428,6 +430,11 @@  static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
 out:
 	dm_table_put(map);

+	if (r == -ENOTCONN) {
+		msleep(10);
+		goto retry;
+	}
+
 	return r;
 }