On Mon, Nov 06, 2006 at 09:45:51PM +0100, Jens Axboe wrote:
> On Mon, Nov 06 2006, Mike Miller (OS Dev) wrote:
> > Patch 12 of 12
> >
> > This patch replaces complete_buffers with end_that_request_first to fix
> > programs like iostat. This has been broken for the last few kernel releases.
> > Please consider this for inclusion.
> >
> > Thanks,
> > mikem
> >
> > Signed-off-by: Mike Miller <mike.miller@xxxxxx>
> >
> >
> > ---
> >
> >
> > ---
> >
> > drivers/block/cciss.c | 20 ++++----------------
> > 1 files changed, 4 insertions(+), 16 deletions(-)
> >
> > diff -puN drivers/block/cciss.c~cciss_update_diskstats_fix drivers/block/cciss.c
> > --- linux-2.6/drivers/block/cciss.c~cciss_update_diskstats_fix 2006-11-06 13:28:53.000000000 -0600
> > +++ linux-2.6-root/drivers/block/cciss.c 2006-11-06 13:28:53.000000000 -0600
> > @@ -1156,18 +1156,6 @@ static int cciss_ioctl(struct inode *ino
> > }
> > }
> >
> > -static inline void complete_buffers(struct bio *bio, int status)
> > -{
> > - while (bio) {
> > - struct bio *xbh = bio->bi_next;
> > - int nr_sectors = bio_sectors(bio);
> > -
> > - bio->bi_next = NULL;
> > - bio_endio(bio, nr_sectors << 9, status ? 0 : -EIO);
> > - bio = xbh;
> > - }
> > -}
> > -
> > static void cciss_check_queues(ctlr_info_t *h)
> > {
> > int start_queue = h->next_to_run;
> > @@ -1236,15 +1224,15 @@ static void cciss_softirq_done(struct re
> > pci_unmap_page(h->pdev, temp64.val, cmd->SG[i].Len, ddir);
> > }
> >
> > - complete_buffers(rq->bio, rq->errors);
> > -
> > #ifdef CCISS_DEBUG
> > printk("Done with %p\n", rq);
> > #endif /* CCISS_DEBUG */
> >
> > - add_disk_randomness(rq->rq_disk);
> > spin_lock_irqsave(&h->lock, flags);
> > - end_that_request_last(rq, rq->errors);
> > + if (!end_that_request_first(rq, rq->errors, rq->nr_sectors)) {
> > + add_disk_randomness(rq->rq_disk);
> > + end_that_request_last(rq, rq->errors);
> > + }
> > cmd_free(h, cmd, 1);
> > cciss_check_queues(h);
> > spin_unlock_irqrestore(&h->lock, flags);
>
> Ah, so there's where that went. Your code isn't clear, though -
> end_that_request_first() _must_ return 0, so the above looks confusing.
> It would look cleaner and more informative like:
>
> if (end_that_request_first(rq, rq->errors, rq->nr_sectors))
> BUG();
>
> add_disk_randomness(rq->rq_disk);
> end_that_request_last(rq, rq->errors);
> ...
>
> and so on. Additionally you don't need the lock for
> end_that_request_first(), so it's a lot more optimal to rearrange it
> again.
>
> add_disk_randomness(rq->rq_disk);
> if (end_that_request_first(rq, rq->errors, rq->nr_sectors))
> BUG();
>
> spin_lock_irqsave(&h->lock, flags);
> end_that_request_last(rq, rq->errors);
> cmd_free(h, cmd, 1);
> ...
>
> Not only cleaner to read since it's obvious what will happen, also moves
> the heavy path (end_that_request_first()) outside of the controller
> lock.
>
> --
> Jens Axboe
>
Thanks Jens. I'm fighting several fires right now so the cleanup will
be done in a day or 2.
mikem
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