This is a note to let you know that I've just added the patch titled block: Revert v5.0 blk_mq_request_issue_directly() changes to the 5.0-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: block-revert-v5.0-blk_mq_request_issue_directly-changes.patch and it can be found in the queue-5.0 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From fd9c40f64c514bdc585a21e2e33fa5f83ca8811b Mon Sep 17 00:00:00 2001 From: Bart Van Assche <bvanassche@xxxxxxx> Date: Thu, 4 Apr 2019 10:08:43 -0700 Subject: block: Revert v5.0 blk_mq_request_issue_directly() changes From: Bart Van Assche <bvanassche@xxxxxxx> commit fd9c40f64c514bdc585a21e2e33fa5f83ca8811b upstream. blk_mq_try_issue_directly() can return BLK_STS*_RESOURCE for requests that have been queued. If that happens when blk_mq_try_issue_directly() is called by the dm-mpath driver then dm-mpath will try to resubmit a request that is already queued and a kernel crash follows. Since it is nontrivial to fix blk_mq_request_issue_directly(), revert the blk_mq_request_issue_directly() changes that went into kernel v5.0. This patch reverts the following commits: * d6a51a97c0b2 ("blk-mq: replace and kill blk_mq_request_issue_directly") # v5.0. * 5b7a6f128aad ("blk-mq: issue directly with bypass 'false' in blk_mq_sched_insert_requests") # v5.0. * 7f556a44e61d ("blk-mq: refactor the code of issue request directly") # v5.0. Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> Cc: Ming Lei <ming.lei@xxxxxxxxxx> Cc: Jianchao Wang <jianchao.w.wang@xxxxxxxxxx> Cc: Hannes Reinecke <hare@xxxxxxxx> Cc: Johannes Thumshirn <jthumshirn@xxxxxxx> Cc: James Smart <james.smart@xxxxxxxxxxxx> Cc: Dongli Zhang <dongli.zhang@xxxxxxxxxx> Cc: Laurence Oberman <loberman@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Reported-by: Laurence Oberman <loberman@xxxxxxxxxx> Tested-by: Laurence Oberman <loberman@xxxxxxxxxx> Fixes: 7f556a44e61d ("blk-mq: refactor the code of issue request directly") # v5.0. Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- block/blk-core.c | 4 - block/blk-mq-sched.c | 8 ++- block/blk-mq.c | 122 ++++++++++++++++++++++++++------------------------- block/blk-mq.h | 6 -- 4 files changed, 71 insertions(+), 69 deletions(-) --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1246,8 +1246,6 @@ static int blk_cloned_rq_check_limits(st */ blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request *rq) { - blk_qc_t unused; - if (blk_cloned_rq_check_limits(q, rq)) return BLK_STS_IOERR; @@ -1263,7 +1261,7 @@ blk_status_t blk_insert_cloned_request(s * bypass a potential scheduler on the bottom device for * insert. */ - return blk_mq_try_issue_directly(rq->mq_hctx, rq, &unused, true, true); + return blk_mq_request_issue_directly(rq, true); } EXPORT_SYMBOL_GPL(blk_insert_cloned_request); --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -423,10 +423,12 @@ void blk_mq_sched_insert_requests(struct * busy in case of 'none' scheduler, and this way may save * us one extra enqueue & dequeue to sw queue. */ - if (!hctx->dispatch_busy && !e && !run_queue_async) + if (!hctx->dispatch_busy && !e && !run_queue_async) { blk_mq_try_issue_list_directly(hctx, list); - else - blk_mq_insert_requests(hctx, ctx, list); + if (list_empty(list)) + return; + } + blk_mq_insert_requests(hctx, ctx, list); } blk_mq_run_hw_queue(hctx, run_queue_async); --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1805,74 +1805,76 @@ static blk_status_t __blk_mq_issue_direc return ret; } -blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx, +static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx, struct request *rq, blk_qc_t *cookie, - bool bypass, bool last) + bool bypass_insert, bool last) { struct request_queue *q = rq->q; bool run_queue = true; - blk_status_t ret = BLK_STS_RESOURCE; - int srcu_idx; - bool force = false; - hctx_lock(hctx, &srcu_idx); /* - * hctx_lock is needed before checking quiesced flag. + * RCU or SRCU read lock is needed before checking quiesced flag. * - * When queue is stopped or quiesced, ignore 'bypass', insert - * and return BLK_STS_OK to caller, and avoid driver to try to - * dispatch again. + * When queue is stopped or quiesced, ignore 'bypass_insert' from + * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller, + * and avoid driver to try to dispatch again. */ - if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) { + if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) { run_queue = false; - bypass = false; - goto out_unlock; + bypass_insert = false; + goto insert; } - if (unlikely(q->elevator && !bypass)) - goto out_unlock; + if (q->elevator && !bypass_insert) + goto insert; if (!blk_mq_get_dispatch_budget(hctx)) - goto out_unlock; + goto insert; if (!blk_mq_get_driver_tag(rq)) { blk_mq_put_dispatch_budget(hctx); - goto out_unlock; + goto insert; } - /* - * Always add a request that has been through - *.queue_rq() to the hardware dispatch list. - */ - force = true; - ret = __blk_mq_issue_directly(hctx, rq, cookie, last); -out_unlock: + return __blk_mq_issue_directly(hctx, rq, cookie, last); +insert: + if (bypass_insert) + return BLK_STS_RESOURCE; + + blk_mq_request_bypass_insert(rq, run_queue); + return BLK_STS_OK; +} + +static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx, + struct request *rq, blk_qc_t *cookie) +{ + blk_status_t ret; + int srcu_idx; + + might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING); + + hctx_lock(hctx, &srcu_idx); + + ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false, true); + if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) + blk_mq_request_bypass_insert(rq, true); + else if (ret != BLK_STS_OK) + blk_mq_end_request(rq, ret); + + hctx_unlock(hctx, srcu_idx); +} + +blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last) +{ + blk_status_t ret; + int srcu_idx; + blk_qc_t unused_cookie; + struct blk_mq_hw_ctx *hctx = rq->mq_hctx; + + hctx_lock(hctx, &srcu_idx); + ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true, last); hctx_unlock(hctx, srcu_idx); - switch (ret) { - case BLK_STS_OK: - break; - case BLK_STS_DEV_RESOURCE: - case BLK_STS_RESOURCE: - if (force) { - blk_mq_request_bypass_insert(rq, run_queue); - /* - * We have to return BLK_STS_OK for the DM - * to avoid livelock. Otherwise, we return - * the real result to indicate whether the - * request is direct-issued successfully. - */ - ret = bypass ? BLK_STS_OK : ret; - } else if (!bypass) { - blk_mq_sched_insert_request(rq, false, - run_queue, false); - } - break; - default: - if (!bypass) - blk_mq_end_request(rq, ret); - break; - } return ret; } @@ -1880,20 +1882,22 @@ out_unlock: void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx, struct list_head *list) { - blk_qc_t unused; - blk_status_t ret = BLK_STS_OK; - while (!list_empty(list)) { + blk_status_t ret; struct request *rq = list_first_entry(list, struct request, queuelist); list_del_init(&rq->queuelist); - if (ret == BLK_STS_OK) - ret = blk_mq_try_issue_directly(hctx, rq, &unused, - false, + ret = blk_mq_request_issue_directly(rq, list_empty(list)); + if (ret != BLK_STS_OK) { + if (ret == BLK_STS_RESOURCE || + ret == BLK_STS_DEV_RESOURCE) { + blk_mq_request_bypass_insert(rq, list_empty(list)); - else - blk_mq_sched_insert_request(rq, false, true, false); + break; + } + blk_mq_end_request(rq, ret); + } } /* @@ -1901,7 +1905,7 @@ void blk_mq_try_issue_list_directly(stru * the driver there was more coming, but that turned out to * be a lie. */ - if (ret != BLK_STS_OK && hctx->queue->mq_ops->commit_rqs) + if (!list_empty(list) && hctx->queue->mq_ops->commit_rqs) hctx->queue->mq_ops->commit_rqs(hctx); } @@ -2014,13 +2018,13 @@ static blk_qc_t blk_mq_make_request(stru if (same_queue_rq) { data.hctx = same_queue_rq->mq_hctx; blk_mq_try_issue_directly(data.hctx, same_queue_rq, - &cookie, false, true); + &cookie); } } else if ((q->nr_hw_queues > 1 && is_sync) || (!q->elevator && !data.hctx->dispatch_busy)) { blk_mq_put_ctx(data.ctx); blk_mq_bio_to_request(rq, bio); - blk_mq_try_issue_directly(data.hctx, rq, &cookie, false, true); + blk_mq_try_issue_directly(data.hctx, rq, &cookie); } else { blk_mq_put_ctx(data.ctx); blk_mq_bio_to_request(rq, bio); --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -67,10 +67,8 @@ void blk_mq_request_bypass_insert(struct void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, struct list_head *list); -blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx, - struct request *rq, - blk_qc_t *cookie, - bool bypass, bool last); +/* Used by blk_insert_cloned_request() to issue request directly */ +blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last); void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx, struct list_head *list); Patches currently in stable-queue which might be from bvanassche@xxxxxxx are queue-5.0/block-revert-v5.0-blk_mq_request_issue_directly-changes.patch