From: Mike Christie <mchristi@redhat.com>
Date: Thu, 16 Sep 2010 01:32:38 -0400
Subject: [scsi] increase sync cache timeout
Message-id: <1284600758-29184-1-git-send-email-mchristi@redhat.com>
Patchwork-id: 28251
O-Subject: [PATCH RHEL 5.6]: scsi: increase sync cache timeout
Bugzilla: 592322
RH-Acked-by: Rob Evers <revers@redhat.com>
RH-Acked-by: Tomas Henzl <thenzl@redhat.com>

From: Mike Christie <mchristi@redhat.com>

This is for bz 592322.

>From the upstream commit:
http://git.kernel.org/?p=linux/kernel/git/jejb/scsi-misc-2.6.git;a=commit;h=e3b3e6246726cd05950677ed843010b8e8c5884c

	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.

I have tested the patch by doing writes and causing the
flush (scsi sync cache) to be sent. I have not been
able to replicate the user's problem here. For the specific
problem in the bz we probably need to modify the target
code. This patch will still help other setups like it
did in RHEL 6 though.


diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 9252987..a8ab20a 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -101,6 +101,7 @@ MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK15_MAJOR);
  */
 #define SD_TIMEOUT		(30 * HZ)
 #define SD_MOD_TIMEOUT		(75 * HZ)
+#define SD_FLUSH_TIMEOUT	(60 * HZ)
 
 /*
  * Number of allowed retries
@@ -843,7 +844,7 @@ static int sd_sync_cache(struct scsi_device *sdp)
 		 * flush everything.
 		 */
 		res = scsi_execute_req(sdp, cmd, DMA_NONE, NULL, 0, &sshdr,
-				       SD_TIMEOUT, SD_MAX_RETRIES);
+				       SD_FLUSH_TIMEOUT, SD_MAX_RETRIES);
 		if (res == 0)
 			break;
 	}
@@ -878,7 +879,7 @@ static void sd_prepare_flush(request_queue_t *q, struct request *rq)
 {
 	memset(rq->cmd, 0, sizeof(rq->cmd));
 	rq->flags |= REQ_BLOCK_PC;
-	rq->timeout = SD_TIMEOUT;
+	rq->timeout = SD_FLUSH_TIMEOUT;
 	rq->cmd[0] = SYNCHRONIZE_CACHE;
 	rq->cmd_len = 10;
 }