bcache: add backing_request_endio() for bi_end_io

In order to catch I/O error of backing device, a separate bi_end_io
call back is required. Then a per backing device counter can record I/O
errors number and retire the backing device if the counter reaches a
per backing device I/O error limit.

This patch adds backing_request_endio() to bcache backing device I/O code
path, this is a preparation for further complicated backing device failure
handling. So far there is no real code logic change, I make this change a
separate patch to make sure it is stable and reliable for further work.

Changelog:
v2: Fix code comments typo, remove a redundant bch_writeback_add() line
    added in v4 patch set.
v1: indeed this is new added in this patch set.

[mlyle: truncated commit subject]

Signed-off-by: Coly Li <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Michael Lyle <[email protected]>
Cc: Junhui Tang <[email protected]>
Cc: Michael Lyle <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

0 files changed, 0 insertions, 0 deletions