[PATCH] scsi_error: count medium access timeout only once per EH run

[Hannes Reinecke <hare@suse.de>]

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

Cc: Ewan Milne <emilne@redhat.com>
Cc: Lawrence Oberman <loberman@redhat.com>
Cc: Benjamin Block <bblock@linux.vnet.ibm.vom>
Cc: Steffen Maier <maier@de.ibm.com>
Signed-off-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/scsi_error.c |  2 ++
 drivers/scsi/sd.c         | 16 ++++++++++++++--
 drivers/scsi/sd.h         |  1 +
 include/scsi/scsi.h       |  1 +
 4 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index f2cafae..481ea1b 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -58,6 +58,7 @@
 static int scsi_eh_try_stu(struct scsi_cmnd *scmd);
 static int scsi_try_to_abort_cmd(struct scsi_host_template *,
 				 struct scsi_cmnd *);
+static int scsi_eh_action(struct scsi_cmnd *scmd, int rtn);
 
 /* called with shost->host_lock held */
 void scsi_eh_wakeup(struct Scsi_Host *shost)
@@ -249,6 +250,7 @@ int scsi_eh_scmd_add(struct scsi_cmnd *scmd, int eh_flag)
 	if (scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED)
 		eh_flag &= ~SCSI_EH_CANCEL_CMD;
 	scmd->eh_eflags |= eh_flag;
+	scsi_eh_action(scmd, NEEDS_RESET);
 	list_add_tail(&scmd->eh_entry, &shost->eh_cmd_q);
 	shost->host_failed++;
 	scsi_eh_wakeup(shost);
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index be535d4..cd9f290 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1696,12 +1696,21 @@ static int sd_pr_clear(struct block_device *bdev, u64 key)
  *	the eh command is passed in eh_disp.  We're looking for devices that
  *	fail medium access commands but are OK with non access commands like
  *	test unit ready (so wrongly see the device as having a successful
- *	recovery)
+ *	recovery).
+ *	We have to be careful to count a medium access failure only once
+ *	per 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.
  **/
 static int sd_eh_action(struct scsi_cmnd *scmd, int eh_disp)
 {
 	struct scsi_disk *sdkp = scsi_disk(scmd->request->rq_disk);
 
+	if (eh_disp == NEEDS_RESET) {
+		/* New SCSI EH run, reset gate variable */
+		sdkp->medium_access_reset = 0;
+		return eh_disp;
+	}
 	if (!scsi_device_online(scmd->device) ||
 	    !scsi_medium_access_command(scmd) ||
 	    host_byte(scmd->result) != DID_TIME_OUT ||
@@ -1715,7 +1724,10 @@ 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->medium_access_reset) {
+		sdkp->medium_access_timed_out++;
+		sdkp->medium_access_reset++;
+	}
 
 	/*
 	 * If the device keeps failing read/write commands but TEST UNIT
diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
index 4dac35e..19e0bab 100644
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -85,6 +85,7 @@ struct scsi_disk {
 	unsigned int	physical_block_size;
 	unsigned int	max_medium_access_timeouts;
 	unsigned int	medium_access_timed_out;
+	unsigned int	medium_access_reset;
 	u8		media_present;
 	u8		write_prot;
 	u8		protection_type;/* Data Integrity Field */
diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index a1e1930..b6c750f 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -185,6 +185,7 @@ static inline int scsi_is_wlun(u64 lun)
 #define TIMEOUT_ERROR   0x2007
 #define SCSI_RETURN_NOT_HANDLED   0x2008
 #define FAST_IO_FAIL	0x2009
+#define NEEDS_RESET     0x2010
 
 /*
  * Midlevel queue return values.
-- 
1.8.5.6