Re: [PATCH] blktrace: add missing probe argument to block_bio_complete

Jeff Moyer
2011-01-07T15:28:10Z

Jens Axboe <axboe@kernel.dk> writes:

> On 2011-01-07 15:13, Jeff Moyer wrote:
>> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> writes:
>>
>>> blktrace.c block bio complete callback needs to gain a new argument to reflect
>>> the newly added "error" tracepoint argument. This is needed to match the new
>>> block_bio_complete TRACE_EVENT as of
>>> commit de983a7bfcb7c020901ca6e2314cf55a4207ab5a.
>>>
>>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>>> CC: Jeff Moyer <jmoyer@redhat.com>
>>> CC: Steven Rostedt <rostedt@goodmis.org>
>>> CC: Frederic Weisbecker <fweisbec@gmail.com>
>>> CC: Ingo Molnar <mingo@elte.hu>
>>> CC: Thomas Gleixner <tglx@linutronix.de>
>>> CC: Jens Axboe <axboe@kernel.dk>
>>> CC: Li Zefan <lizf@cn.fujitsu.com>
>>> ---
>>> kernel/trace/blktrace.c | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> Index: linux-2.6-lttng/kernel/trace/blktrace.c
>>> ===================================================================
>>> --- linux-2.6-lttng.orig/kernel/trace/blktrace.c
>>> +++ linux-2.6-lttng/kernel/trace/blktrace.c
>>> @@ -785,7 +785,8 @@ static void blk_add_trace_bio_bounce(voi
>>> }
>>>
>>> static void blk_add_trace_bio_complete(void *ignore,
>>> - struct request_queue *q, struct bio *bio)
>>> + struct request_queue *q, struct bio *bio,
>>> + int error)
>>> {
>>> blk_add_trace_bio(q, bio, BLK_TA_COMPLETE);
>>> }
>>
>> OK, I clearly didn't look closely enough last time. There's no sense
>> passing this information down if it isn't used (as you said initially).
>> blk_add_trace_bio sets the error based on whether or not the
>> BIO_UPTODATE bit is set. So, I think we should instead revert the patch
>> I sent you (Mathieu), and then completely get rid of the error field in
>> the TP macros.
>>
>> Does that make sense to everyone else?
>
> We usually use BIO_UPTODATE if we have no other information available.
> So if we have, then we should use it.

OK, I had contemplated doing it that way, too, but I wasn't sure how
often the error differed from EIO. Anyway, this looks better.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>

>
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index fab31af..153562d 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -758,54 +758,58 @@ static void blk_add_trace_rq_complete(void *ignore,
> * @q: queue the io is for
> * @bio: the source bio
> * @what: the action
> + * @error: error, if any
> *
> * Description:
> * Records an action against a bio. Will log the bio offset + size.
> *
> **/
> static void blk_add_trace_bio(struct request_queue *q, struct bio *bio,
> - u32 what)
> + u32 what, int error)
> {
> struct blk_trace *bt = q->blk_trace;
>
> if (likely(!bt))
> return;
>
> + if (!error && !bio_flagged(bio, BIO_UPTODATE))
> + error = EIO;
> +
> __blk_add_trace(bt, bio->bi_sector, bio->bi_size, bio->bi_rw, what,
> - !bio_flagged(bio, BIO_UPTODATE), 0, NULL);
> + error, 0, NULL);
> }
>
> static void blk_add_trace_bio_bounce(void *ignore,
> struct request_queue *q, struct bio *bio)
> {
> - blk_add_trace_bio(q, bio, BLK_TA_BOUNCE);
> + blk_add_trace_bio(q, bio, BLK_TA_BOUNCE, 0);
> }
>
> static void blk_add_trace_bio_complete(void *ignore,
> struct request_queue *q, struct bio *bio,
> int error)
> {
> - blk_add_trace_bio(q, bio, BLK_TA_COMPLETE);
> + blk_add_trace_bio(q, bio, BLK_TA_COMPLETE, error);
> }
>
> static void blk_add_trace_bio_backmerge(void *ignore,
> struct request_queue *q,
> struct bio *bio)
> {
> - blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE);
> + blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE, 0);
> }
>
> static void blk_add_trace_bio_frontmerge(void *ignore,
> struct request_queue *q,
> struct bio *bio)
> {
> - blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE);
> + blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE, 0);
> }
>
> static void blk_add_trace_bio_queue(void *ignore,
> struct request_queue *q, struct bio *bio)
> {
> - blk_add_trace_bio(q, bio, BLK_TA_QUEUE);
> + blk_add_trace_bio(q, bio, BLK_TA_QUEUE, 0);
> }
>
> static void blk_add_trace_getrq(void *ignore,
> @@ -813,7 +817,7 @@ static void blk_add_trace_getrq(void *ignore,
> struct bio *bio, int rw)
> {
> if (bio)
> - blk_add_trace_bio(q, bio, BLK_TA_GETRQ);
> + blk_add_trace_bio(q, bio, BLK_TA_GETRQ, 0);
> else {
> struct blk_trace *bt = q->blk_trace;
>
> @@ -828,7 +832,7 @@ static void blk_add_trace_sleeprq(void *ignore,
> struct bio *bio, int rw)
> {
> if (bio)
> - blk_add_trace_bio(q, bio, BLK_TA_SLEEPRQ);
> + blk_add_trace_bio(q, bio, BLK_TA_SLEEPRQ, 0);
> else {
> struct blk_trace *bt = q->blk_trace;