[SCSI] scsi/block: increase flush/sync timeout

We have been seeing the flush request timeout with a wide
range of hardware from tgt+iser to FC targets from a major vendor.

After discussions about if the value should be configurable and
what the best value should be, this patch just increases the flush/sync
cache timeout to 1 minute. 2 minutes was determined to be too long, and
making it configurable was troublesome for users.

This patch was made over Linus's tree. It is not made over scsi-misc
or scsi-rc-fixes, because Linus's had block layer changes that my
patch was built over.
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/sd.c

@@ -477,7 +477,7 @@ static int scsi_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq)
 
 static int scsi_setup_flush_cmnd(struct scsi_device *sdp, struct request *rq)
 {
-	rq->timeout = SD_TIMEOUT;
+	rq->timeout = SD_FLUSH_TIMEOUT;
 	rq->retries = SD_MAX_RETRIES;
 	rq->cmd[0] = SYNCHRONIZE_CACHE;
 	rq->cmd_len = 10;
@@ -1072,7 +1072,7 @@ static int sd_sync_cache(struct scsi_disk *sdkp)
 		 * flush everything.
 		 */
 		res = scsi_execute_req(sdp, cmd, DMA_NONE, NULL, 0, &sshdr,
-				       SD_TIMEOUT, SD_MAX_RETRIES, NULL);
+				       SD_FLUSH_TIMEOUT, SD_MAX_RETRIES, NULL);
 		if (res == 0)
 			break;
 	}

drivers/scsi/sd.h

@@ -19,6 +19,7 @@
  */
 #define SD_TIMEOUT		(30 * HZ)
 #define SD_MOD_TIMEOUT		(75 * HZ)
+#define SD_FLUSH_TIMEOUT	(60 * HZ)
 
 /*
  * Number of allowed retries