[PATCH 12/12] cciss: fix for iostat

[Mike Miller (OS Dev)]

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....@hp.com>

---

---

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);
_
-
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[Jens Axboe]

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

[Jens Axboe]

IOW, simple one-liner fix:

diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index 6ffe2b2..f9f128a 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -1299,6 +1299,7 @@ static void cciss_softirq_done(struct re
}

complete_buffers(rq->bio, rq->errors);
+ disk_stat_add(rq->rq_disk, sectors[rq_data_dir(rq)], rq->nr_sectors);

#ifdef CCISS_DEBUG
printk("Done with %p\n", rq);

--

[Mike Miller (OS Dev)]

Thanks Jens. I'm fighting several fires right now so the cleanup will
be done in a day or 2.

mikem