linux-kernel - [PATCH 3.19.y-ckt 054/128] dm: fix ioctl retry termination with signal

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Date:	Wed, 16 Dec 2015 09:38:14 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Jun'ichi Nomura <j-nomura@...jp.nec.com>,
	Hannes Reinecke <hare@...e.de>,
	Mikulas Patocka <mpatocka@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>,
	Luis Henriques <luis.henriques@...onical.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 054/128] dm: fix ioctl retry termination with signal

3.19.8-ckt12 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Junichi Nomura <j-nomura@...jp.nec.com>

commit 5bbbfdf685657771fda05b926b28ca0f79163a28 upstream.

dm-mpath retries ioctl, when no path is readily available and the device
is configured to queue I/O in such a case. If you want to stop the retry
before multipathd decides to turn off queueing mode, you could send
signal for the process to exit from the loop.

However the check of fatal signal has not carried along when commit
6c182cd88d17 ("dm mpath: fix ioctl deadlock when no paths") moved the
loop from dm-mpath to dm core. As a result, we can't terminate such
a process in the retry loop.

Easy reproducer of the situation is:

  # dmsetup create mp --table '0 1024 multipath 0 0 0 0'
  # dmsetup message mp 0 'queue_if_no_path'
  # sg_inq /dev/mapper/mp

then you should be able to terminate sg_inq by pressing Ctrl+C.

Fixes: 6c182cd88d17 ("dm mpath: fix ioctl deadlock when no paths")
Signed-off-by: Jun'ichi Nomura <j-nomura@...jp.nec.com>
Cc: Hannes Reinecke <hare@...e.de>
Cc: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/md/dm-mpath.c | 2 +-
 drivers/md/dm.c       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 7ed0e7b..35cbc2a 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1548,7 +1548,7 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
 	if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
 		r = scsi_verify_blk_ioctl(NULL, cmd);
 
-	if (r == -ENOTCONN && !fatal_signal_pending(current)) {
+	if (r == -ENOTCONN) {
 		spin_lock_irqsave(&m->lock, flags);
 		if (!m->current_pg) {
 			/* Path status changed, redo selection */
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index df81bbd..b93f32d 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -543,7 +543,7 @@ retry:
 out:
 	dm_put_live_table(md, srcu_idx);
 
-	if (r == -ENOTCONN) {
+	if (r == -ENOTCONN && !fatal_signal_pending(current)) {
 		msleep(10);
 		goto retry;
 	}
-- 
1.9.1

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