linux-kernel - [PATCH AUTOSEL 5.6 100/149] scsi: core: avoid repetitive logging of device offline messages

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Date:   Sat, 11 Apr 2020 19:02:57 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Ewan D. Milne" <emilne@...hat.com>,
        Bart van Assche <bvanassche@....org>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>, linux-scsi@...r.kernel.org
Subject: [PATCH AUTOSEL 5.6 100/149] scsi: core: avoid repetitive logging of device offline messages

From: "Ewan D. Milne" <emilne@...hat.com>

[ Upstream commit b0962c53bde9a485c8ebc401fa1dbe821a76bc3e ]

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.

Link: https://lore.kernel.org/r/20200311143930.20674-1-emilne@redhat.com
Reviewed-by: Bart van Assche <bvanassche@....org>
Signed-off-by: Ewan D. Milne <emilne@...hat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 610ee41fa54cb..a45e7289dbbe7 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 f8312a3e5b429..cd9656ff3c43c 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 */
-- 
2.20.1