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    Subject[PATCH -block/for-next 0/2] blktrace: bio-based device tracing improvement v3

    The blktrace is used to report block device activities to user space
    using kernel tracepoint but it was focused to block I/O request struct.
    Thus bio-based devices (i.e. loop, ram, md, ...) which don't make use
    of the request structure could not be supported well - the tool only
    can detect a limited number of events such as queuing, cloning and
    remapping but it cannot know when the I/O activity is completed.

    bio_endio(), the I/O completion callback, can be used to fix this
    problem by adding appropriate tracepoint in it. However it was called
    from other paths too (normal request-based block devices and some of
    nested block I/O handling routines) so that we should recognize such
    cases to prevent duplicated reports. In this series, BIO_IN_FLIGHT flag
    is introduced and used for that purpose.

    Note that (bio-based) dm already supported completion report by adding
    the tracepoint into the path manually. With this patches, it will be
    converted to use generic mechanism.

    Changes from v2:
    * rebased on current block/for-next

    Changes from v1:
    * kill __bio_endio()
    * use BIO_IN_FLIGHT flag

    Any feedbacks are welcome.


    Namhyung Kim (2):
    block: introduce BIO_IN_FLIGHT flag
    block: don't export block_bio_complete tracepoint

    block/blk-core.c | 6 +++++-
    drivers/md/dm.c | 1 -
    fs/bio.c | 7 +++++++
    include/linux/blk_types.h | 1 +
    4 files changed, 13 insertions(+), 2 deletions(-)


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