On Sat, 2013-05-04 at 19:02 +0200, Bart Van Assche wrote:
> On 05/03/13 20:23, James Bottomley wrote:
> > + const unsigned long stall_for = min(msecs_to_jiffies(10), 1UL);
>
> Hello James,
>
> Can you please clarify what the intention of this statement is ? Is the
> purpose of this statement to avoid that stall_for would be zero in case
> HZ < 100 ? If that is the case, maybe you meant max() instead of min() ?
> Also, are you aware that msecs_to_jiffies() already rounds up the result
> of the division ?
Yes, I thought afterwards I should dump the bogus min statement as well.
Plus HZ/10 is actually 100ms, so the value is 10x wrong. I've fixed it
up below (plus a bit of comment rework and some style fixes).
Thanks,
James
---
>From 4bd9ef9789ad86656d8e52e8fff5422b741097e1 Mon Sep 17 00:00:00 2001
From: Hannes Reinecke <h...@suse.de>
Date: Thu, 25 Apr 2013 08:10:00 +0200
Subject: [PATCH] [SCSI] Handle MLQUEUE busy response in scsi_send_eh_cmnd
scsi_send_eh_cmnd() is calling queuecommand() directly, so
it needs to check the return value here.
The only valid return codes for queuecommand() are 'busy'
states, so we need to wait for a bit to allow the LLDD
to recover.
Based on an earlier patch from Wen Xiong.
[jejb: fix confusion between msec and jiffies values and other issues]
[bvanassche: correct stall_for interval]
Cc: Wen Xiong <wenxi...@linux.vnet.ibm.com>
Cc: Brian King <brk...@linux.vnet.ibm.com>
Signed-off-by: Hannes Reinecke <h...@suse.de>
Signed-off-by: James Bottomley <jbottom...@parallels.com>
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index c1b05a8..f43de1e 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -25,6 +25,7 @@
#include <linux/interrupt.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
+#include <linux/jiffies.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
@@ -791,32 +792,48 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd,
unsigned char *cmnd,
struct scsi_device *sdev = scmd->device;
struct Scsi_Host *shost = sdev->host;
DECLARE_COMPLETION_ONSTACK(done);
- unsigned long timeleft;
+ unsigned long timeleft = timeout;
struct scsi_eh_save ses;
+ const unsigned long stall_for = msecs_to_jiffies(100);
int rtn;
+retry:
scsi_eh_prep_cmnd(scmd, &ses, cmnd, cmnd_size, sense_bytes);
shost->eh_action = &done;
scsi_log_send(scmd);
scmd->scsi_done = scsi_eh_done;
- shost->hostt->queuecommand(shost, scmd);
-
- timeleft = wait_for_completion_timeout(&done, timeout);
+ rtn = shost->hostt->queuecommand(shost, scmd);
+ if (rtn) {
+ if (timeleft > stall_for) {
+ scsi_eh_restore_cmnd(scmd, &ses);
+ timeleft -= stall_for;
+ msleep(jiffies_to_msecs(stall_for));
+ goto retry;
+ }
+ /* signal not to enter either branch of the if () below */
+ timeleft = 0;
+ rtn = NEEDS_RETRY;
+ } else {
+ timeleft = wait_for_completion_timeout(&done, timeout);
+ }
shost->eh_action = NULL;
- scsi_log_completion(scmd, SUCCESS);
+ scsi_log_completion(scmd, rtn);
SCSI_LOG_ERROR_RECOVERY(3,
printk("%s: scmd: %p, timeleft: %ld\n",
__func__, scmd, timeleft));
/*
- * If there is time left scsi_eh_done got called, and we will
- * examine the actual status codes to see whether the command
- * actually did complete normally, else tell the host to forget
- * about this command.
+ * If there is time left scsi_eh_done got called, and we will examine
+ * the actual status codes to see whether the command actually did
+ * complete normally, else if we have a zero return and no time left,
+ * the command must still be pending, so abort it and return FAILED.
+ * If we never actually managed to issue the command, because
+ * ->queuecommand() kept returning non zero, use the rtn = FAILED
+ * value above (so don't execute either branch of the if)
*/
if (timeleft) {
rtn = scsi_eh_completed_normally(scmd);
@@ -837,7 +854,7 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd,
unsigned char *cmnd,
rtn = FAILED;
break;
}
- } else {
+ } else if (!rtn) {
scsi_abort_eh_cmnd(scmd);
rtn = FAILED;
}
--
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