[PATCH v2] scsi: avoid repetitive logging of device offline messages

[PATCH v2] scsi: avoid repetitive logging of device offline messages

[Ewan D. Milne]

Large queues of I/O to offline devices that are eventually
submitted when devices are unblocked result in a many repeated
"rejecting I/O to offline device" messages.  These messages
can fill up the dmesg buffer in crash dumps so no useful
prior messages remain.  In addition, if a serial console
is used, the flood of messages can cause a hard lockup in
the console code.

Introduce a flag indicating the message has already been logged
for the device, and reset the flag when scsi_device_set_state()
changes the device state.

v2:
	Changed flag type from bitfield to bool by request

Signed-off-by: Ewan D. Milne <emilne@redhat.com>
---
 drivers/scsi/scsi_lib.c    | 8 ++++++--
 include/scsi/scsi_device.h | 3 +++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 610ee41..a45e728 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1240,8 +1240,11 @@ scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
 		 * commands.  The device must be brought online
 		 * before trying any recovery commands.
 		 */
-		sdev_printk(KERN_ERR, sdev,
-			    "rejecting I/O to offline device\n");
+		if (!sdev->offline_already) {
+			sdev->offline_already = true;
+			sdev_printk(KERN_ERR, sdev,
+				    "rejecting I/O to offline device\n");
+		}
 		return BLK_STS_IOERR;
 	case SDEV_DEL:
 		/*
@@ -2340,6 +2343,7 @@ scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
 		break;
 
 	}
+	sdev->offline_already = false;
 	sdev->sdev_state = state;
 	return 0;
 
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index f8312a3..cd9656f 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -204,6 +204,9 @@ struct scsi_device {
 	unsigned unmap_limit_for_ws:1;	/* Use the UNMAP limit for WRITE SAME */
 	unsigned rpm_autosuspend:1;	/* Enable runtime autosuspend at device
 					 * creation time */
+
+	bool offline_already;		/* Device offline message logged */
+
 	atomic_t disk_events_disable_depth; /* disable depth for disk events */
 
 	DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */
-- 
2.1.0

Re: [PATCH v2] scsi: avoid repetitive logging of device offline messages

[Bart Van Assche]

On 2020-03-11 07:39, Ewan D. Milne wrote:
> Large queues of I/O to offline devices that are eventually
> submitted when devices are unblocked result in a many repeated
> "rejecting I/O to offline device" messages.  These messages
> can fill up the dmesg buffer in crash dumps so no useful
> prior messages remain.  In addition, if a serial console
> is used, the flood of messages can cause a hard lockup in
> the console code.
> 
> Introduce a flag indicating the message has already been logged
> for the device, and reset the flag when scsi_device_set_state()
> changes the device state.
> 
> v2:
> 	Changed flag type from bitfield to bool by request

Thanks!

Reviewed-by: Bart van Assche <bvanassche@acm.org>

Re: [PATCH v2] scsi: avoid repetitive logging of device offline messages

[Martin K. Petersen]

Ewan,

> Large queues of I/O to offline devices that are eventually submitted
> when devices are unblocked result in a many repeated "rejecting I/O to
> offline device" messages.  These messages can fill up the dmesg buffer
> in crash dumps so no useful prior messages remain.  In addition, if a
> serial console is used, the flood of messages can cause a hard lockup
> in the console code.
>
> Introduce a flag indicating the message has already been logged for
> the device, and reset the flag when scsi_device_set_state() changes
> the device state.

Applied to 5.7/scsi-queue, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering