On Tuesday 20 April 2010, Desai, Kashyap wrote:
> > > > > all block device flushes or is this more device specific? I was
> > > > > thinking that we may want to create a sysfs interface under the
> >
> > block
> >
> > > > > dirs and have blk-sysfs.c and blk-barrier.c handle this.
> >
> > queue_flush
> >
> > > > > could set the timeout and retries that is set by some new files
> >
> > under
> >
> > > > > /sys/block/sdX/queue/ ?
>
> Thanks a lot for your comments.
>
> This is very close to my understanding. I feel this is more close to block
> layer and I am almost agreeing with your thought. I tried to understand
> why upstream does not have retries at queue_flush()/sd_prepare_flush() ???
> It looks like there is not specific reason. If I am wrong can someone
> explain is there any specific reason not to set rq->retries in
> sd_prepare_flush?
I don't understand why we should need another queue timeout, when we
already have a device timeout that is used as queue timeout?
Below is an updated patch. And I think as of commit
242f9dcb8ba6f68fcd217a119a7648a4f69290e9 ("block: unify request
timeout handling") using struct request_queue->rq_timeout is correct.
What I really wonder about, if we shouldn't add a scsi sysfs entry
to set a default timeout? In some environments (e.g. ib_srp with a
large number of LUNs through an IB switch) scanning the those devices
can be slow and besides that many of those device scan functions
use SD_TIMEOUT, we also have not set timeouts using udev already,
as udev will only be called once the scan is over...
[SCSI] Use user defined timeouts for SYNCHRONIZE_CACHE
Switch to adjustable timeout value for scsi SYNCHRONIZE_CACHE commands.
We have been running into problems with fixed values on troublesome devices.
Update: add SD_MAX_RETRIES in sd_prepare_flush()
Patch originally written for Q-Leap, but DDN needs it as well.
Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
---
drivers/scsi/sd.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
Index: linux-git/drivers/scsi/sd.c
===================================================================
--- linux-git.orig/drivers/scsi/sd.c
+++ linux-git/drivers/scsi/sd.c
@@ -1020,7 +1020,8 @@ static int sd_sync_cache(struct scsi_dis
* flush everything.
*/
res = scsi_execute_req(sdp, cmd, DMA_NONE, NULL, 0, &sshdr,
- SD_TIMEOUT, SD_MAX_RETRIES, NULL);
+ sdp->request_queue->rq_timeout,
+ SD_MAX_RETRIES, NULL);
if (res == 0)
break;
}
@@ -1039,7 +1040,8 @@ static int sd_sync_cache(struct scsi_dis
static void sd_prepare_flush(struct request_queue *q, struct request *rq)
{
rq->cmd_type = REQ_TYPE_BLOCK_PC;
- rq->timeout = SD_TIMEOUT;
+ rq->timeout = q->rq_timeout;
+ rq->retries = SD_MAX_RETRIES;
rq->cmd[0] = SYNCHRONIZE_CACHE;
rq->cmd_len = 10;
}
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