blk-mq: punt failed direct issue to dispatch list
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 livelock. 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:Ming Lei <ming.lei@redhat.com> Reported-by:
Bart Van Assche <bvanassche@acm.org> Tested-by:
Ming Lei <ming.lei@redhat.com> Acked-by:
Mike Snitzer <snitzer@redhat.com> Signed-off-by:
Jens Axboe <axboe@kernel.dk>
parent
ba7aeae5
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