On 06/24/2009 09:40 AM, Hannes Reinecke wrote:
> During heavy I/O the scsi cmd might be stuck in the cmdqueue
> and hasn't even been sent at the time the command timeout
> strikes. So we should be resetting the command timer here
> and not aborting the command.
>
> Signed-off-by: Hannes Reinecke<h...@suse.de>
> ---
> drivers/scsi/libiscsi.c | 8 ++++++++
> 1 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
> index 41bb177..e5b79cf 100644
> --- a/drivers/scsi/libiscsi.c
> +++ b/drivers/scsi/libiscsi.c
> @@ -1795,6 +1795,14 @@ static enum blk_eh_timer_return
> iscsi_eh_cmd_timed_out(struct scsi_cmnd *sc)
> goto done;
> }
>
> + if (!list_empty(&conn->cmdqueue)) {
I think you want to check for the task->state == ISCSI_TASK_PENDING. If
we just check if there is any IO on the cmdqueue, could be that one IO
is really stuck and new IO is getting added and we just happen to have
bad luck and do the check above when new IO is getting added?
I am still not sure how do we decide when to give the command to the
scsi eh layer? If a task is stuck in ISCSI_TASK_PENDING for 5 minutes,
can we say we give up and let the scsi layer have it eventually or did
you really want to continue asking for more time?
I added this code
http://git.kernel.org/?p=linux/kernel/git/jejb/scsi-misc-2.6.git;a=commitdiff;h=d355e57d58193b89283b0c8153649f0427b0bdad
to give a task more time if we have not got/send data or it during the
scsi cmd timeuot second period. Then if on the second run, it still has
not completed a pdu then we will let the scsi eh run. This still has
problems. As you saw when the queue depth is high and/or the link or
device is slow, then we can easily queue enough IO where a command does
not get run for a couple scsi cmd timeout periods. I was also working on
decreasing the queuedepth and host->can_queue, but am not done (I have
just consolidated the QUEUE_FULL ramp down code so far as you saw on
linux-scsi).
> + ISCSI_DBG_EH(session, "cmdqueue busy, reset timeout. "
> + "Last data recv at %lu. Last timeout was at "
> + "%lu\n", task->last_xfer, task->last_timeout);
> + rc = BLK_EH_RESET_TIMER;
> + goto done;
> + }
> +
> if (!conn->recv_timeout&& !conn->ping_timeout)
> goto done;
> /*
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