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Commit 3ef28e83 authored by Dan Williams's avatar Dan Williams Committed by Jens Axboe
Browse files

block: generic request_queue reference counting 



Allow pmem, and other synchronous/bio-based block drivers, to fallback
on a per-cpu reference count managed by the core for tracking queue
live/dead state.

The existing per-cpu reference count for the blk_mq case is promoted to
be used in all block i/o scenarios.  This involves initializing it by
default, waiting for it to drop to zero at exit, and holding a live
reference over the invocation of q->make_request_fn() in
generic_make_request().  The blk_mq code continues to take its own
reference per blk_mq request and retains the ability to freeze the
queue, but the check that the queue is frozen is moved to
generic_make_request().

This fixes crash signatures like the following:

 BUG: unable to handle kernel paging request at ffff880140000000
 [..]
 Call Trace:
  [<ffffffff8145e8bf>] ? copy_user_handle_tail+0x5f/0x70
  [<ffffffffa004e1e0>] pmem_do_bvec.isra.11+0x70/0xf0 [nd_pmem]
  [<ffffffffa004e331>] pmem_make_request+0xd1/0x200 [nd_pmem]
  [<ffffffff811c3162>] ? mempool_alloc+0x72/0x1a0
  [<ffffffff8141f8b6>] generic_make_request+0xd6/0x110
  [<ffffffff8141f966>] submit_bio+0x76/0x170
  [<ffffffff81286dff>] submit_bh_wbc+0x12f/0x160
  [<ffffffff81286e62>] submit_bh+0x12/0x20
  [<ffffffff813395bd>] jbd2_write_superblock+0x8d/0x170
  [<ffffffff8133974d>] jbd2_mark_journal_empty+0x5d/0x90
  [<ffffffff813399cb>] jbd2_journal_destroy+0x24b/0x270
  [<ffffffff810bc4ca>] ? put_pwq_unlocked+0x2a/0x30
  [<ffffffff810bc6f5>] ? destroy_workqueue+0x225/0x250
  [<ffffffff81303494>] ext4_put_super+0x64/0x360
  [<ffffffff8124ab1a>] generic_shutdown_super+0x6a/0xf0

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Tested-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 4cfc766e

block/blk-core.c

+62 −9
Original line number Original line Diff line number Diff line
@@ -554,13 +554,10 @@ void blk_cleanup_queue(struct request_queue *q) 
	 * Drain all requests queued before DYING marking. Set DEAD flag to

	 * Drain all requests queued before DYING marking. Set DEAD flag to

	 * prevent that q->request_fn() gets invoked after draining finished.

	 * prevent that q->request_fn() gets invoked after draining finished.

	 */

	 */

	if (q->mq_ops) {

	blk_freeze_queue(q);

		blk_mq_freeze_queue(q);

		spin_lock_irq(lock);

	} else {

	spin_lock_irq(lock);

	spin_lock_irq(lock);

	if (!q->mq_ops)

		__blk_drain_queue(q, true);

		__blk_drain_queue(q, true);

	}

	queue_flag_set(QUEUE_FLAG_DEAD, q);

	queue_flag_set(QUEUE_FLAG_DEAD, q);

	spin_unlock_irq(lock);

	spin_unlock_irq(lock);
@@ -570,6 +567,7 @@ void blk_cleanup_queue(struct request_queue *q) 




	if (q->mq_ops)

	if (q->mq_ops)

		blk_mq_free_queue(q);

		blk_mq_free_queue(q);

	percpu_ref_exit(&q->q_usage_counter);





	spin_lock_irq(lock);

	spin_lock_irq(lock);

	if (q->queue_lock != &q->__queue_lock)

	if (q->queue_lock != &q->__queue_lock)
@@ -629,6 +627,40 @@ struct request_queue *blk_alloc_queue(gfp_t gfp_mask) 
}

}

EXPORT_SYMBOL(blk_alloc_queue);

EXPORT_SYMBOL(blk_alloc_queue);





int blk_queue_enter(struct request_queue *q, gfp_t gfp)

{

	while (true) {

		int ret;



		if (percpu_ref_tryget_live(&q->q_usage_counter))

			return 0;



		if (!(gfp & __GFP_WAIT))

			return -EBUSY;



		ret = wait_event_interruptible(q->mq_freeze_wq,

				!atomic_read(&q->mq_freeze_depth) ||

				blk_queue_dying(q));

		if (blk_queue_dying(q))

			return -ENODEV;

		if (ret)

			return ret;

	}

}



void blk_queue_exit(struct request_queue *q)

{

	percpu_ref_put(&q->q_usage_counter);

}



static void blk_queue_usage_counter_release(struct percpu_ref *ref)

{

	struct request_queue *q =

		container_of(ref, struct request_queue, q_usage_counter);



	wake_up_all(&q->mq_freeze_wq);

}



struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)

struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)

{

{

	struct request_queue *q;

	struct request_queue *q;
@@ -690,11 +722,22 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) 




	init_waitqueue_head(&q->mq_freeze_wq);

	init_waitqueue_head(&q->mq_freeze_wq);





	if (blkcg_init_queue(q))

	/*

	 * Init percpu_ref in atomic mode so that it's faster to shutdown.

	 * See blk_register_queue() for details.

	 */

	if (percpu_ref_init(&q->q_usage_counter,

				blk_queue_usage_counter_release,

				PERCPU_REF_INIT_ATOMIC, GFP_KERNEL))

		goto fail_bdi;

		goto fail_bdi;





	if (blkcg_init_queue(q))

		goto fail_ref;



	return q;

	return q;





fail_ref:

	percpu_ref_exit(&q->q_usage_counter);

fail_bdi:

fail_bdi:

	bdi_destroy(&q->backing_dev_info);

	bdi_destroy(&q->backing_dev_info);

fail_split:

fail_split:
@@ -1966,9 +2009,19 @@ void generic_make_request(struct bio *bio) 
	do {

	do {

		struct request_queue *q = bdev_get_queue(bio->bi_bdev);

		struct request_queue *q = bdev_get_queue(bio->bi_bdev);





		if (likely(blk_queue_enter(q, __GFP_WAIT) == 0)) {



			q->make_request_fn(q, bio);

			q->make_request_fn(q, bio);





			blk_queue_exit(q);



			bio = bio_list_pop(current->bio_list);

			bio = bio_list_pop(current->bio_list);

		} else {

			struct bio *bio_next = bio_list_pop(current->bio_list);



			bio_io_error(bio);

			bio = bio_next;

		}

	} while (bio);

	} while (bio);

	current->bio_list = NULL; /* deactivate */

	current->bio_list = NULL; /* deactivate */

}

}

block/blk-mq-sysfs.c

+0 −6
Original line number Original line Diff line number Diff line
@@ -413,12 +413,6 @@ static void blk_mq_sysfs_init(struct request_queue *q) 
		kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);

		kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);

}

}





/* see blk_register_queue() */

void blk_mq_finish_init(struct request_queue *q)

{

	percpu_ref_switch_to_percpu(&q->mq_usage_counter);

}



int blk_mq_register_disk(struct gendisk *disk)

int blk_mq_register_disk(struct gendisk *disk)

{

{

	struct device *dev = disk_to_dev(disk);

	struct device *dev = disk_to_dev(disk);

block/blk-mq.c

+24 −56
Original line number Original line Diff line number Diff line
@@ -78,47 +78,13 @@ static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx, 
	clear_bit(CTX_TO_BIT(hctx, ctx), &bm->word);

	clear_bit(CTX_TO_BIT(hctx, ctx), &bm->word);

}

}





static int blk_mq_queue_enter(struct request_queue *q, gfp_t gfp)

{

	while (true) {

		int ret;



		if (percpu_ref_tryget_live(&q->mq_usage_counter))

			return 0;



		if (!(gfp & __GFP_WAIT))

			return -EBUSY;



		ret = wait_event_interruptible(q->mq_freeze_wq,

				!atomic_read(&q->mq_freeze_depth) ||

				blk_queue_dying(q));

		if (blk_queue_dying(q))

			return -ENODEV;

		if (ret)

			return ret;

	}

}



static void blk_mq_queue_exit(struct request_queue *q)

{

	percpu_ref_put(&q->mq_usage_counter);

}



static void blk_mq_usage_counter_release(struct percpu_ref *ref)

{

	struct request_queue *q =

		container_of(ref, struct request_queue, mq_usage_counter);



	wake_up_all(&q->mq_freeze_wq);

}



void blk_mq_freeze_queue_start(struct request_queue *q)

void blk_mq_freeze_queue_start(struct request_queue *q)

{

{

	int freeze_depth;

	int freeze_depth;





	freeze_depth = atomic_inc_return(&q->mq_freeze_depth);

	freeze_depth = atomic_inc_return(&q->mq_freeze_depth);

	if (freeze_depth == 1) {

	if (freeze_depth == 1) {

		percpu_ref_kill(&q->mq_usage_counter);

		percpu_ref_kill(&q->q_usage_counter);

		blk_mq_run_hw_queues(q, false);

		blk_mq_run_hw_queues(q, false);

	}

	}

}

}
@@ -126,18 +92,34 @@ EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_start); 




static void blk_mq_freeze_queue_wait(struct request_queue *q)

static void blk_mq_freeze_queue_wait(struct request_queue *q)

{

{

	wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter));

	wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));

}

}





/*

/*

 * Guarantee no request is in use, so we can change any data structure of

 * Guarantee no request is in use, so we can change any data structure of

 * the queue afterward.

 * the queue afterward.

 */

 */

void blk_mq_freeze_queue(struct request_queue *q)

void blk_freeze_queue(struct request_queue *q)

{

{

	/*

	 * In the !blk_mq case we are only calling this to kill the

	 * q_usage_counter, otherwise this increases the freeze depth

	 * and waits for it to return to zero.  For this reason there is

	 * no blk_unfreeze_queue(), and blk_freeze_queue() is not

	 * exported to drivers as the only user for unfreeze is blk_mq.

	 */

	blk_mq_freeze_queue_start(q);

	blk_mq_freeze_queue_start(q);

	blk_mq_freeze_queue_wait(q);

	blk_mq_freeze_queue_wait(q);

}

}



void blk_mq_freeze_queue(struct request_queue *q)

{

	/*

	 * ...just an alias to keep freeze and unfreeze actions balanced

	 * in the blk_mq_* namespace

	 */

	blk_freeze_queue(q);

}

EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);

EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);





void blk_mq_unfreeze_queue(struct request_queue *q)

void blk_mq_unfreeze_queue(struct request_queue *q)
@@ -147,7 +129,7 @@ void blk_mq_unfreeze_queue(struct request_queue *q) 
	freeze_depth = atomic_dec_return(&q->mq_freeze_depth);

	freeze_depth = atomic_dec_return(&q->mq_freeze_depth);

	WARN_ON_ONCE(freeze_depth < 0);

	WARN_ON_ONCE(freeze_depth < 0);

	if (!freeze_depth) {

	if (!freeze_depth) {

		percpu_ref_reinit(&q->mq_usage_counter);

		percpu_ref_reinit(&q->q_usage_counter);

		wake_up_all(&q->mq_freeze_wq);

		wake_up_all(&q->mq_freeze_wq);

	}

	}

}

}
@@ -256,7 +238,7 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp, 
	struct blk_mq_alloc_data alloc_data;

	struct blk_mq_alloc_data alloc_data;

	int ret;

	int ret;





	ret = blk_mq_queue_enter(q, gfp);

	ret = blk_queue_enter(q, gfp);

	if (ret)

	if (ret)

		return ERR_PTR(ret);

		return ERR_PTR(ret);
@@ -279,7 +261,7 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp, 
	}

	}

	blk_mq_put_ctx(ctx);

	blk_mq_put_ctx(ctx);

	if (!rq) {

	if (!rq) {

		blk_mq_queue_exit(q);

		blk_queue_exit(q);

		return ERR_PTR(-EWOULDBLOCK);

		return ERR_PTR(-EWOULDBLOCK);

	}

	}

	return rq;

	return rq;
@@ -298,7 +280,7 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx, 




	clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);

	clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);

	blk_mq_put_tag(hctx, tag, &ctx->last_tag);

	blk_mq_put_tag(hctx, tag, &ctx->last_tag);

	blk_mq_queue_exit(q);

	blk_queue_exit(q);

}

}





void blk_mq_free_hctx_request(struct blk_mq_hw_ctx *hctx, struct request *rq)

void blk_mq_free_hctx_request(struct blk_mq_hw_ctx *hctx, struct request *rq)
@@ -1177,11 +1159,7 @@ static struct request *blk_mq_map_request(struct request_queue *q, 
	int rw = bio_data_dir(bio);

	int rw = bio_data_dir(bio);

	struct blk_mq_alloc_data alloc_data;

	struct blk_mq_alloc_data alloc_data;





	if (unlikely(blk_mq_queue_enter(q, GFP_KERNEL))) {

	blk_queue_enter_live(q);

		bio_io_error(bio);

		return NULL;

	}



	ctx = blk_mq_get_ctx(q);

	ctx = blk_mq_get_ctx(q);

	hctx = q->mq_ops->map_queue(q, ctx->cpu);

	hctx = q->mq_ops->map_queue(q, ctx->cpu);
@@ -2000,14 +1978,6 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, 
		hctxs[i]->queue_num = i;

		hctxs[i]->queue_num = i;

	}

	}





	/*

	 * Init percpu_ref in atomic mode so that it's faster to shutdown.

	 * See blk_register_queue() for details.

	 */

	if (percpu_ref_init(&q->mq_usage_counter, blk_mq_usage_counter_release,

			    PERCPU_REF_INIT_ATOMIC, GFP_KERNEL))

		goto err_hctxs;



	setup_timer(&q->timeout, blk_mq_rq_timer, (unsigned long) q);

	setup_timer(&q->timeout, blk_mq_rq_timer, (unsigned long) q);

	blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);

	blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
@@ -2088,8 +2058,6 @@ void blk_mq_free_queue(struct request_queue *q) 




	blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);

	blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);

	blk_mq_free_hw_queues(q, set);

	blk_mq_free_hw_queues(q, set);



	percpu_ref_exit(&q->mq_usage_counter);

}

}





/* Basically redo blk_mq_init_queue with queue frozen */

/* Basically redo blk_mq_init_queue with queue frozen */

block/blk-sysfs.c

+1 −2
Original line number Original line Diff line number Diff line
@@ -599,9 +599,8 @@ int blk_register_queue(struct gendisk *disk) 
	 */

	 */

	if (!blk_queue_init_done(q)) {

	if (!blk_queue_init_done(q)) {

		queue_flag_set_unlocked(QUEUE_FLAG_INIT_DONE, q);

		queue_flag_set_unlocked(QUEUE_FLAG_INIT_DONE, q);

		percpu_ref_switch_to_percpu(&q->q_usage_counter);

		blk_queue_bypass_end(q);

		blk_queue_bypass_end(q);

		if (q->mq_ops)

			blk_mq_finish_init(q);

	}

	}





	ret = blk_trace_init_sysfs(dev);

	ret = blk_trace_init_sysfs(dev);

block/blk.h

+14 −0
Original line number Original line Diff line number Diff line
@@ -72,6 +72,20 @@ void blk_dequeue_request(struct request *rq); 
void __blk_queue_free_tags(struct request_queue *q);

void __blk_queue_free_tags(struct request_queue *q);

bool __blk_end_bidi_request(struct request *rq, int error,

bool __blk_end_bidi_request(struct request *rq, int error,

			    unsigned int nr_bytes, unsigned int bidi_bytes);

			    unsigned int nr_bytes, unsigned int bidi_bytes);

int blk_queue_enter(struct request_queue *q, gfp_t gfp);

void blk_queue_exit(struct request_queue *q);

void blk_freeze_queue(struct request_queue *q);



static inline void blk_queue_enter_live(struct request_queue *q)

{

	/*

	 * Given that running in generic_make_request() context

	 * guarantees that a live reference against q_usage_counter has

	 * been established, further references under that same context

	 * need not check that the queue has been frozen (marked dead).

	 */

	percpu_ref_get(&q->q_usage_counter);

}





void blk_rq_timed_out_timer(unsigned long data);

void blk_rq_timed_out_timer(unsigned long data);

unsigned long blk_rq_timeout(unsigned long timeout);

unsigned long blk_rq_timeout(unsigned long timeout);