linux-kernel - [PATCH 3.16 115/370] scsi: avoid a permanent stop of the scsi device's request queue

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Message-ID: <lsq.1489146382.398507138@decadent.org.uk>
Date:   Fri, 10 Mar 2017 11:46:22 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Wei Fang" <fangwei1@...wei.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Zengxi Chen" <chenzengxi@...wei.com>,
        "Ewan D. Milne" <emilne@...hat.com>
Subject: [PATCH 3.16 115/370] scsi: avoid a permanent stop of the scsi
 device's request queue

3.16.42-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Wei Fang <fangwei1@...wei.com>

commit d2a145252c52792bc59e4767b486b26c430af4bb upstream.

A race between scanning and fc_remote_port_delete() may result in a
permanent stop if the device gets blocked before scsi_sysfs_add_sdev()
and unblocked after.  The reason is that blocking a device sets both the
SDEV_BLOCKED state and the QUEUE_FLAG_STOPPED.  However,
scsi_sysfs_add_sdev() unconditionally sets SDEV_RUNNING which causes the
device to be ignored by scsi_target_unblock() and thus never have its
QUEUE_FLAG_STOPPED cleared leading to a device which is apparently
running but has a stopped queue.

We actually have two places where SDEV_RUNNING is set: once in
scsi_add_lun() which respects the blocked flag and once in
scsi_sysfs_add_sdev() which doesn't.  Since the second set is entirely
spurious, simply remove it to fix the problem.

Reported-by: Zengxi Chen <chenzengxi@...wei.com>
Signed-off-by: Wei Fang <fangwei1@...wei.com>
Reviewed-by: Ewan D. Milne <emilne@...hat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/scsi/scsi_sysfs.c | 4 ----
 1 file changed, 4 deletions(-)

--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1002,10 +1002,6 @@ int scsi_sysfs_add_sdev(struct scsi_devi
 	struct request_queue *rq = sdev->request_queue;
 	struct scsi_target *starget = sdev->sdev_target;

-	error = scsi_device_set_state(sdev, SDEV_RUNNING);
-	if (error)
-		return error;
-
 	error = scsi_target_add(starget);
 	if (error)
 		return error;