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

[Jeff Moyer <jmoyer@redhat.com>]

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;