Messages in this thread | | | Date | Mon, 09 Jan 2012 11:57:43 +0900 | From | Namhyung Kim <> | Subject | Re: [PATCH 1/2] block: introduce BIO_IN_FLIGHT flag |
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2012-01-09 10:56 AM, Tejun Heo wrote: > On Tue, Dec 27, 2011 at 11:28:32PM +0900, Namhyung Kim wrote: >> BIO_IN_FLIGHT flag is used for tracing block I/O completion. >> This patch fixes tracing bio-based devices - except DM which >> inserts completion tracepoint explicitly - that could not be >> traced such event using blktrace. >> >> It won't affect tracing normal (request-based) disk devices >> and nested bio handling paths. >> >> Signed-off-by: Namhyung Kim<namhyung@gmail.com> >> --- >> block/blk-core.c | 5 +++++ >> fs/bio.c | 7 +++++++ >> include/linux/blk_types.h | 1 + >> 3 files changed, 13 insertions(+), 0 deletions(-) >> >> diff --git a/block/blk-core.c b/block/blk-core.c >> index 1b4fd93af2c0..f61310323954 100644 >> --- a/block/blk-core.c >> +++ b/block/blk-core.c >> @@ -165,6 +165,9 @@ static void req_bio_endio(struct request *rq, struct bio *bio, >> if (unlikely(rq->cmd_flags& REQ_QUIET)) >> set_bit(BIO_QUIET,&bio->bi_flags); >> >> + /* completion event was already reported in blk_update_request */ >> + clear_bit(BIO_IN_FLIGHT,&bio->bi_flags); >> + >> bio->bi_size -= nbytes; >> bio->bi_sector += (nbytes>> 9); >> >> @@ -1662,6 +1665,8 @@ void generic_make_request(struct bio *bio) > p> do { >> struct request_queue *q = bdev_get_queue(bio->bi_bdev); >> >> + set_bit(BIO_IN_FLIGHT,&bio->bi_flags); >> + >> q->make_request_fn(q, bio); >> >> bio = bio_list_pop(current->bio_list); >> diff --git a/fs/bio.c b/fs/bio.c >> index b1fe82cf88cf..10fb7a1d74ba 100644 >> --- a/fs/bio.c >> +++ b/fs/bio.c >> @@ -1447,6 +1447,13 @@ void bio_endio(struct bio *bio, int error) >> else if (!test_bit(BIO_UPTODATE,&bio->bi_flags)) >> error = -EIO; >> >> + if (test_bit(BIO_IN_FLIGHT,&bio->bi_flags)) { >> + struct request_queue *q = bdev_get_queue(bio->bi_bdev); >> + >> + trace_block_bio_complete(q, bio, error); >> + clear_bit(BIO_IN_FLIGHT,&bio->bi_flags); >> + } > > This really should be filtered from the consumer side. Not on TP > itself. Doing it like this makes the TP useless for other consumers > and adds unnecessary flag and operations on it even when the TP is not > in use. Why not just trigger the TP on boi_endio() and let blktrace > probe filter out bounced or cloned completions?
I understand your concerns. However, the blktrace cannot get bio->bi_flags info in its current form AFAIK. Doing it will require extending struct blk_io_trace and it'll cause a compatibility issue, I guess.
Anyway I think the needs of tracing bio based drivers are growing so it'd be great the blktrace supports it as well. Also as we've run out of act_mask bits, it might be needed a room for extending.
But before proceeding, I'd like to listen comments/advices from people. Jens?
Thanks, Namhyung Kim
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