On Mon, 2013-04-15 at 16:55 -0500, Brian King wrote:
> On 04/15/2013 03:45 PM, James Bottomley wrote:
> > On Mon, 2013-04-15 at 13:39 -0500, wenxiong@xxxxxxxxxxxxxxxxxx wrote:
> >> In scsi_send_eh_cmnd(), this fix will check the return code of queuecomamnd
> >> when sending commands and retry for a bit if the driver returns a
> >> busy response.
> >
> > This is already handled by the timeout, I think. If a driver
> > continuously returns MLQUEUE BUSY, then we'll fail the request after the
> > timeout on the command expires.
>
> If we get a timeout in scsi_send_eh_cmnd we call scsi_abort_eh_cmnd. If the
> abort works, we return FAILED out of scsi_send_eh_cmnd, which results in
> no retry being performed, since scsi_eh_tur only retries once and
> only if NEEDS_RETRY is returned. Or am I missing something?
Sorry, I'm not being clear. It comes with being at a conference. What
I mean is that if you do this, the criterion for success or failure
should be the amount of time left not the number of retries. This is
what the non-eh submission path also does for retries of events that
don't count against the retry limit ... so something like this patch
(uncompiled and untested #include stddisclaimer.h)
James
----
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index c1b05a8..93ab4f4 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -793,6 +793,7 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
DECLARE_COMPLETION_ONSTACK(done);
unsigned long timeleft;
struct scsi_eh_save ses;
+ const int stall_for = min(HZ/10,1); /* 100 ms */
int rtn;
scsi_eh_prep_cmnd(scmd, &ses, cmnd, cmnd_size, sense_bytes);
@@ -802,6 +803,8 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
scmd->scsi_done = scsi_eh_done;
shost->hostt->queuecommand(shost, scmd);
+ retry:
+
timeleft = wait_for_completion_timeout(&done, timeout);
shost->eh_action = NULL;
@@ -831,8 +834,12 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
case TARGET_ERROR:
break;
case ADD_TO_MLQUEUE:
- rtn = NEEDS_RETRY;
- break;
+ if (timeleft > stall_for) {
+ timeout = timeleft - stall_for;
+ msleep(stall_for);
+ goto retry;
+ }
+ /* fall through */
default:
rtn = FAILED;
break;
--
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