On Sun, Oct 07 2007, malahal@xxxxxxxxxx wrote:
> Jens Axboe [jens.axboe@xxxxxxxxxx] wrote:
> > On Thu, Oct 04 2007, malahal@xxxxxxxxxx wrote:
> > > Mike Christie's patches refreshed to 2.6.23-rc8-mm1.
> > >
> > > Signed-off-by: Mike Christie <michaelc@xxxxxxxxxxx>
> > > Signed-off-by: Malahal Naineni <malahal@xxxxxxxxxx>
> > >
> > >
> > > diff -r 3697367c6e4d block/ll_rw_blk.c
> > > --- a/block/ll_rw_blk.c Thu Sep 27 00:12:13 2007 -0700
> > > +++ b/block/ll_rw_blk.c Thu Sep 27 00:13:07 2007 -0700
> > > @@ -181,6 +181,19 @@ void blk_queue_softirq_done(struct reque
> > >
> > > EXPORT_SYMBOL(blk_queue_softirq_done);
> > >
> > > +void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
> > > +{
> > > + q->rq_timeout = timeout;
> > > +}
> > > +EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
> > > +
> > > +void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn)
> > > +{
> > > + q->rq_timed_out_fn = fn;
> > > +}
> > > +
> > > +EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out);
> > > +
> > > /**
> > > * blk_queue_make_request - define an alternate make_request function for a device
> > > * @q: the request queue for the device to be affected
> > > @@ -243,7 +256,9 @@ static void rq_init(struct request_queue
> > > {
> > > INIT_LIST_HEAD(&rq->queuelist);
> > > INIT_LIST_HEAD(&rq->donelist);
> > > -
> > > + init_timer(&rq->timer);
> > > +
> > > + rq->timeout = 0;
> > > rq->errors = 0;
> > > rq->bio = rq->biotail = NULL;
> > > INIT_HLIST_NODE(&rq->hash);
> > > @@ -2305,6 +2320,7 @@ EXPORT_SYMBOL(blk_start_queueing);
> > > */
> > > void blk_requeue_request(struct request_queue *q, struct request *rq)
> > > {
> > > + blk_delete_timer(rq);
> > > blk_add_trace_rq(q, rq, BLK_TA_REQUEUE);
> > >
> > > if (blk_rq_tagged(rq))
> > > @@ -3647,8 +3663,121 @@ static struct notifier_block blk_cpu_not
> > > };
> > >
> > > /**
> > > + * blk_delete_timer - Delete/cancel timer for a given function.
> > > + * @req: request that we are canceling timer for
> > > + *
> > > + * Return value:
> > > + * 1 if we were able to detach the timer. 0 if we blew it, and the
> > > + * timer function has already started to run.
> > > + **/
> > > +int blk_delete_timer(struct request *req)
> > > +{
> > > + int rtn;
> > > +
> > > + if (!req->q->rq_timed_out_fn)
> > > + return 1;
> > > +
> > > + rtn = del_timer(&req->timer);
> > > + req->timer.data = (unsigned long)NULL;
> > > + req->timer.function = NULL;
> > > +
> > > + return rtn;
> > > +}
> >
> > Hmm, that looks fishy. What if the timer _just_ fired, yet it hasn't
> > retrieved ->data yet?
> >
>
> Looks like it is just copied from the SCSI code. More over _run_timers()
> copies data and function on to stack variables before calling the timer
> function. So, I don't think there is a problem here but assuming that
> implementation detail is bad! I would like modify the above function to
> reinitialize data and function fields only if del_timer() returns TRUE.
> Please let me know if that is OK.
I guess it could be OK, but it then deserves a big fat comment
describing why it is ok.
> > > +
> > > +EXPORT_SYMBOL_GPL(blk_delete_timer);
> > > +
> > > +static void blk_rq_timed_out(struct request *req)
> > > +{
> > > + struct request_queue *q = req->q;
> > > +
> > > + switch (q->rq_timed_out_fn(req)) {
> > > + case BLK_EH_HANDLED:
> > > + __blk_complete_request(req);
> > > + return;
> > > + case BLK_EH_RESET_TIMER:
> > > + blk_add_timer(req);
> > > + return;
> > > + case BLK_EH_NOT_HANDLED:
> > > + /*
> > > + * LLD handles this for now but in the future
> > > + * we can send a request msg to abort the command
> > > + * and we can move more of the generic scsi eh code to
> > > + * the blk layer.
> > > + */
> > > + return;
> > > + }
> > > +}
> > > +
> > > +/**
> > > + * blk_abort_req -- Request request recovery for the specified command
> > > + * req: pointer to the request of interest
> > > + *
> > > + * This function requests that the block layer start recovery for the
> > > + * request by deleting the timer and calling the q's timeout function.
> > > + * LLDDs who implement their own error recovery MAY ignore the timeout
> > > + * event if they generated blk_abort_req.
> > > + */
> > > +void blk_abort_req(struct request *req)
> > > +{
> > > + if (!blk_delete_timer(req))
> > > + return;
> > > + blk_rq_timed_out(req);
> > > +}
> > > +
> > > +EXPORT_SYMBOL_GPL(blk_abort_req);
> > > +
> > > +/**
> > > + * blk_add_timer - Start timeout timer for a single request
> > > + * @req: request that is about to start running.
> > > + *
> > > + * Notes:
> > > + * Each request has its own timer, and as it is added to the queue, we
> > > + * set up the timer. When the request completes, we cancel the timer.
> > > + **/
> > > +void blk_add_timer(struct request *req)
> > > +{
> > > + struct request_queue *q = req->q;
> > > +
> > > + /*
> > > + * If the clock was already running for this command, then
> > > + * first delete the timer. The timer handling code gets rather
> > > + * confused if we don't do this.
> > > + */
> > > + if (req->timer.function)
> > > + del_timer(&req->timer);
> > > +
> > > + req->timer.data = (unsigned long)req;
> > > + if (req->timeout)
> > > + req->timer.expires = jiffies + req->timeout;
> > > + else
> > > + req->timer.expires = jiffies + q->rq_timeout;
> > > + req->timer.function = (void (*)(unsigned long))blk_rq_timed_out;
> >
> > Why the cast?
> >
>
> Because blk_rq_timed_out() doesn't take "unsigned long" as its input
> parameter. Again, copied from SCSI.
Don't copy stuff from SCSI just because you can, it's allowed to fix
things up along the way! I'd propose adding blk_rq_timed_out_timer()
ala:
static void blk_rq_timed_out_timer(unsigned long data)
{
struct request *rq = (struct request *) data;
blk_rq_timed_out(rq);
}
and using that to get rid of the cast.
>
> > > + add_timer(&req->timer);
> >
> > You have space vs tab issues.
> >
> > > +}
> >
> > That's an ugly interface. I'd say it's a bug to call blk_add_timer()
> > with it already pending, so fix the API.
>
> blk_add_timer is also called from the timer function (blk_rq_timed_out) if
> BLK_EH_RESET_TIMER is retuned. This is also copied from SCSI! Please let me
> know if you want to do it some other way.
I thought I just did :-)
Delete the timer first, the API you are proposing isn't very nice.
--
Jens Axboe
-
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
