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

[Namhyung Kim <namhyung@gmail.com>]

Hello,

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.

Thanks.


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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1.7.6