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    SubjectRe: [PATCH 2/3] block: prevent duplicated bio completion report
    Hello,

    On Tue, Jan 17, 2012 at 10:32:07AM +0900, Namhyung Kim wrote:
    > Since previous patch make block_bio_complete TP working,
    > it will generate duplicated BLK_TA_COMPLETEs for bounced
    > bios. Fix it.
    >
    > Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
    > Cc: Tejun Heo <tj@kernel.org>

    This and the third patch should probably be merged to the first patch.
    As it currently stands, it introduces window where spurious events are
    generated.

    > diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
    > index 4053cbd4490e..45cd0074a1c8 100644
    > --- a/include/linux/blk_types.h
    > +++ b/include/linux/blk_types.h
    > @@ -97,6 +97,9 @@ struct bio {
    > #define BIO_MAPPED_INTEGRITY 11/* integrity metadata has been remapped */
    > #define bio_flagged(bio, flag) ((bio)->bi_flags & (1 << (flag)))
    >
    > +/* masked bio's won't report its completion via tracepoint */
    > +#define BIO_COMPLETE_MASK (1 << BIO_BOUNCED)

    And, who's setting this flag?

    > /*
    > * top 4 bits of bio flags indicate the pool this bio came from
    > */
    > diff --git a/include/trace/events/block.h b/include/trace/events/block.h
    > index 96955f4828b3..72888542e186 100644
    > --- a/include/trace/events/block.h
    > +++ b/include/trace/events/block.h
    > @@ -219,7 +219,8 @@ TRACE_EVENT_CONDITION(block_bio_complete,
    >
    > TP_ARGS(q, bio, error),
    >
    > - TP_CONDITION(bio->bi_bdev != NULL),
    > + TP_CONDITION(bio->bi_bdev != NULL &&
    > + !(bio->bi_flags & BIO_COMPLETE_MASK)),

    Bounced bio's are separate bio's too and I don't think masking its
    completion from the TP itself is a good idea. As I wrote before, why
    not do this from blktrace code?

    Thanks.

    --
    tejun


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