• Adrian Hunter's avatar
    block: prevent merges of discard and write requests · f281fb5f
    Adrian Hunter authored
    Add logic to prevent two I/O requests being merged if
    only one of them is a discard.  Ditto secure discard.
    Without this fix, it is possible for write requests
    to transform into discard requests.  For example:
      Submit bio 1 to discard 8 sectors from sector n
      Submit bio 2 to write 8 sectors from sector n + 16
      Submit bio 3 to write 8 sectors from sector n + 8
    Bio 1 becomes request 1.  Bio 2 becomes request 2.
    Bio 3 is merged with request 2, and then subsequently
    request 2 is merged with request 1 resulting in just
    one I/O request which discards all 24 sectors.
    Signed-off-by: default avatarAdrian Hunter <adrian.hunter@nokia.com>
    (Moved the checks above the position checks /Jens)
    Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
blk-merge.c 10.9 KB