[PATCH 3/4] Avoid re-enabling I/O after the transport became offline

Bart Van Assche
2013-07-02T13:07:25Z

Disallow the SDEV_TRANSPORT_OFFLINE to SDEV_CANCEL transition such
that no I/O is sent to devices for which the transport is offline.
Notes:
- Functions like sd_shutdown() use scsi_execute_req() and hence
set the REQ_PREEMPT flag. Such requests are passed to the LLD
queuecommand callback in the SDEV_CANCEL state.
- This patch does not affect Fibre Channel LLD drivers since these
drivers invoke fc_remote_port_chkready() before submitting a SCSI
request to the HBA. That prevents a timeout to occur in state
SDEV_CANCEL if the transport is offline.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: James Bottomley <JBottomley@Parallels.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Tejun Heo <tj@kernel.org>
---
drivers/scsi/scsi_lib.c | 1 -
drivers/scsi/scsi_sysfs.c | 9 ++++++++-
2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 124392f..a0fb56b 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2178,7 +2178,6 @@ scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
case SDEV_RUNNING:
case SDEV_QUIESCE:
case SDEV_OFFLINE:
- case SDEV_TRANSPORT_OFFLINE:
case SDEV_BLOCK:
break;
default:
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 931a7d9..1711617 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -955,7 +955,14 @@ void __scsi_remove_device(struct scsi_device *sdev)
struct device *dev = &sdev->sdev_gendev;

if (sdev->is_visible) {
- if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0)
+ /*
+ * The transition from SDEV_TRANSPORT_OFFLINE into
+ * SDEV_CANCEL is not allowed since this transition would
+ * reenable I/O. However, if the device state was already
+ * SDEV_TRANSPORT_OFFLINE, proceed with device removal.
+ */
+ if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0 &&
+ sdev->sdev_state != SDEV_TRANSPORT_OFFLINE)
return;

bsg_unregister_queue(sdev->request_queue);
--
1.7.10.4