linux-kernel - [PATCH 3.16.y-ckt 059/126] dm: fix ioctl retry termination with signal

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Date:	Wed,  6 Jan 2016 10:36:28 +0000
From:	Luis Henriques <luis.henriques@...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>
Subject: [PATCH 3.16.y-ckt 059/126] dm: fix ioctl retry termination with signal

3.16.7-ckt22 -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>
---
 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 43e2b498732f..34601cc0c508 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 91b239489785..f62d4c8bd9f9 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -528,7 +528,7 @@ retry:
 out:
 	dm_put_live_table(md, srcu_idx);
 
-	if (r == -ENOTCONN) {
+	if (r == -ENOTCONN && !fatal_signal_pending(current)) {
 		msleep(10);
 		goto retry;
 	}
--
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