scsi: scsi_error: count medium access timeout only once per EH run

The current medium access timeout counter will be increased for
each command, so if there are enough failed commands we'll hit
the medium access timeout for even a single device failure and
the following kernel message is displayed:

sd H:C:T:L: [sdXY] Medium access timeout failure. Offlining disk!

Fix this by making the timeout per EH run, ie the counter will
only be increased once per device and EH run.

Fixes: 18a4d0a ("[SCSI] Handle disk devices which can not process medium access commands")
Cc: Ewan Milne <emilne@redhat.com>
Cc: Lawrence Obermann <loberman@redhat.com>
Cc: Benjamin Block <bblock@linux.vnet.ibm.com>
Cc: Steffen Maier <maier@linux.vnet.ibm.com>
Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 26 insertions, 1 deletions

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index d277e86..bd2a38e 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -115,6 +115,7 @@ static void sd_rescan(struct device *);
 static int sd_init_command(struct scsi_cmnd *SCpnt);
 static void sd_uninit_command(struct scsi_cmnd *SCpnt);
 static int sd_done(struct scsi_cmnd *);
+static void sd_eh_reset(struct scsi_cmnd *);
 static int sd_eh_action(struct scsi_cmnd *, int);
 static void sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer);
 static void scsi_disk_release(struct device *cdev);
@@ -532,6 +533,7 @@ static struct scsi_driver sd_template = {
 	.uninit_command		= sd_uninit_command,
 	.done			= sd_done,
 	.eh_action		= sd_eh_action,
+	.eh_reset		= sd_eh_reset,
 };
 
 /*
@@ -1686,6 +1688,26 @@ static const struct block_device_operations sd_fops = {
 };
 
 /**
+ *	sd_eh_reset - reset error handling callback
+ *	@scmd:		sd-issued command that has failed
+ *
+ *	This function is called by the SCSI midlayer before starting
+ *	SCSI EH. When counting medium access failures we have to be
+ *	careful to register it only only once per device and SCSI EH run;
+ *	there might be several timed out commands which will cause the
+ *	'max_medium_access_timeouts' counter to trigger after the first
+ *	SCSI EH run already and set the device to offline.
+ *	So this function resets the internal counter before starting SCSI EH.
+ **/
+static void sd_eh_reset(struct scsi_cmnd *scmd)
+{
+	struct scsi_disk *sdkp = scsi_disk(scmd->request->rq_disk);
+
+	/* New SCSI EH run, reset gate variable */
+	sdkp->ignore_medium_access_errors = false;
+}
+
+/**
  *	sd_eh_action - error handling callback
  *	@scmd:		sd-issued command that has failed
  *	@eh_disp:	The recovery disposition suggested by the midlayer
@@ -1714,7 +1736,10 @@ static int sd_eh_action(struct scsi_cmnd *scmd, int eh_disp)
 	 * process of recovering or has it suffered an internal failure
 	 * that prevents access to the storage medium.
 	 */
-	sdkp->medium_access_timed_out++;
+	if (!sdkp->ignore_medium_access_errors) {
+		sdkp->medium_access_timed_out++;
+		sdkp->ignore_medium_access_errors = true;
+	}
 
 	/*
 	 * If the device keeps failing read/write commands but TEST UNIT