Commit fd9c40f6 authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

block: Revert v5.0 blk_mq_request_issue_directly() changes 



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:
* d6a51a97 ("blk-mq: replace and kill blk_mq_request_issue_directly") # v5.0.
* 5b7a6f12 ("blk-mq: issue directly with bypass 'false' in blk_mq_sched_insert_requests") # v5.0.
* 7f556a44 ("blk-mq: refactor the code of issue request directly") # v5.0.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Jianchao Wang <jianchao.w.wang@oracle.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: James Smart <james.smart@broadcom.com>
Cc: Dongli Zhang <dongli.zhang@oracle.com>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: <stable@vger.kernel.org>
Reported-by: default avatarLaurence Oberman <loberman@redhat.com>
Tested-by: default avatarLaurence Oberman <loberman@redhat.com>
Fixes: 7f556a44 ("blk-mq: refactor the code of issue request directly") # v5.0.
Signed-off-by: default avatarBart Van Assche <bvanassche@acm.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent f0d17625

block/blk-core.c

+1 −3
Original line number Diff line number Diff line
@@ -1245,8 +1245,6 @@ static int blk_cloned_rq_check_limits(struct request_queue *q, 
 */

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;
@@ -1262,7 +1260,7 @@ blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request * 
	 * 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);

block/blk-mq-sched.c

+5 −3
Original line number Diff line number Diff line
@@ -423,9 +423,11 @@ void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx, 
		 * 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

			if (list_empty(list))

				return;

		}

		blk_mq_insert_requests(hctx, ctx, list);

	}

block/blk-mq.c

+63 −59
Original line number Diff line number Diff line
@@ -1801,95 +1801,99 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx, 
	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:

	hctx_unlock(hctx, srcu_idx);

	switch (ret) {

	case BLK_STS_OK:

		break;

	case BLK_STS_DEV_RESOURCE:

	case BLK_STS_RESOURCE:

		if (force) {

	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);

			/*

			 * 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);

	return BLK_STS_OK;

}

		break;

	default:

		if (!bypass)



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);

		break;



	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);



	return ret;

}



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);

		}

	}



	/*
@@ -1897,7 +1901,7 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx, 
	 * 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);

}
@@ -2012,13 +2016,13 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) 
			data.hctx = same_queue_rq->mq_hctx;

			trace_block_unplug(q, 1, true);

			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);

block/blk-mq.h

+2 −4
Original line number Diff line number Diff line
@@ -70,10 +70,8 @@ void blk_mq_request_bypass_insert(struct request *rq, bool run_queue); 
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);

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