• Jens Axboe's avatar
    blk-mq: punt failed direct issue to dispatch list · c616cbee
    Jens Axboe authored
    After the direct dispatch corruption fix, we permanently disallow direct
    dispatch of non read/write requests. This works fine off the normal IO
    path, as they will be retried like any other failed direct dispatch
    request. But for the blk_insert_cloned_request() that only DM uses to
    bypass the bottom level scheduler, we always first attempt direct
    dispatch. For some types of requests, that's now a permanent failure,
    and no amount of retrying will make that succeed. This results in a
    Instead of making special cases for what we can direct issue, and now
    having to deal with DM solving the livelock while still retaining a BUSY
    condition feedback loop, always just add a request that has been through
    ->queue_rq() to the hardware queue dispatch list. These are safe to use
    as no merging can take place there. Additionally, if requests do have
    prepped data from drivers, we aren't dependent on them not sharing space
    in the request structure to safely add them to the IO scheduler lists.
    This basically reverts ffe81d45 and is based on a patch from Ming,
    but with the list insert case covered as well.
    Fixes: ffe81d45 ("blk-mq: fix corruption with direct issue")
    Cc: stable@vger.kernel.org
    Suggested-by: default avatarMing Lei <ming.lei@redhat.com>
    Reported-by: default avatarBart Van Assche <bvanassche@acm.org>
    Tested-by: default avatarMing Lei <ming.lei@redhat.com>
    Acked-by: default avatarMike Snitzer <snitzer@redhat.com>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
blk-mq.c 79.5 KB