[dm-devel] [PATCH 3/3] dm: mark dm queue as blocking if any underlying is blocking

[Ming Lei]

dm request based driver doesn't set BLK_MQ_F_BLOCKING, so dm_queue_rq()
is supposed to not sleep.

However, blk_insert_cloned_request() is used by dm_queue_rq() for
queuing underlying request, but the underlying queue may be marked as
BLK_MQ_F_BLOCKING, so blk_insert_cloned_request() may become to block
current context, then rcu warning is triggered.

Fixes the issue by marking dm request based queue as BLK_MQ_F_BLOCKING
if any underlying queue is marked as BLK_MQ_F_BLOCKING, meantime we
need to allocate srcu beforehand.

Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
 drivers/md/dm-rq.c    |  5 ++++-
 drivers/md/dm-rq.h    |  3 ++-
 drivers/md/dm-table.c | 14 ++++++++++++++
 drivers/md/dm.c       |  5 +++--
 drivers/md/dm.h       |  1 +
 5 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 579ab6183d4d..2297d37c62a9 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -535,7 +535,8 @@ static const struct blk_mq_ops dm_mq_ops = {
 	.init_request = dm_mq_init_request,
 };
 
-int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t)
+int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t,
+			     bool blocking)
 {
 	struct dm_target *immutable_tgt;
 	int err;
@@ -550,6 +551,8 @@ int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t)
 	md->tag_set->flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_STACKING;
 	md->tag_set->nr_hw_queues = dm_get_blk_mq_nr_hw_queues();
 	md->tag_set->driver_data = md;
+	if (blocking)
+		md->tag_set->flags |= BLK_MQ_F_BLOCKING;
 
 	md->tag_set->cmd_size = sizeof(struct dm_rq_target_io);
 	immutable_tgt = dm_table_get_immutable_target(t);
diff --git a/drivers/md/dm-rq.h b/drivers/md/dm-rq.h
index 1eea0da641db..5f3729f277d7 100644
--- a/drivers/md/dm-rq.h
+++ b/drivers/md/dm-rq.h
@@ -30,7 +30,8 @@ struct dm_rq_clone_bio_info {
 	struct bio clone;
 };
 
-int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t);
+int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t,
+			     bool blocking);
 void dm_mq_cleanup_mapped_device(struct mapped_device *md);
 
 void dm_start_queue(struct request_queue *q);
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index aa173f5bdc3d..e4bdd4f757a3 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1875,6 +1875,20 @@ static bool dm_table_supports_write_zeroes(struct dm_table *t)
 	return true;
 }
 
+/* If the device can block inside ->queue_rq */
+static int device_is_io_blocking(struct dm_target *ti, struct dm_dev *dev,
+			      sector_t start, sector_t len, void *data)
+{
+	struct request_queue *q = bdev_get_queue(dev->bdev);
+
+	return blk_queue_blocking(q);
+}
+
+bool dm_table_has_blocking_dev(struct dm_table *t)
+{
+	return dm_table_any_dev_attr(t, device_is_io_blocking, NULL);
+}
+
 static int device_not_nowait_capable(struct dm_target *ti, struct dm_dev *dev,
 				     sector_t start, sector_t len, void *data)
 {
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 280918cdcabd..2f72877752dd 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1761,7 +1761,7 @@ static struct mapped_device *alloc_dev(int minor)
 	 * established. If request-based table is loaded: blk-mq will
 	 * override accordingly.
 	 */
-	md->disk = blk_alloc_disk(md->numa_node_id);
+	md->disk = blk_alloc_disk_srcu(md->numa_node_id);
 	if (!md->disk)
 		goto bad;
 	md->queue = md->disk->queue;
@@ -2046,7 +2046,8 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
 	switch (type) {
 	case DM_TYPE_REQUEST_BASED:
 		md->disk->fops = &dm_rq_blk_dops;
-		r = dm_mq_init_request_queue(md, t);
+		r = dm_mq_init_request_queue(md, t,
+				dm_table_has_blocking_dev(t));
 		if (r) {
 			DMERR("Cannot initialize queue for request-based dm mapped device");
 			return r;
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 742d9c80efe1..f7f92b272cce 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -60,6 +60,7 @@ int dm_calculate_queue_limits(struct dm_table *table,
 			      struct queue_limits *limits);
 int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 			      struct queue_limits *limits);
+bool dm_table_has_blocking_dev(struct dm_table *t);
 struct list_head *dm_table_get_devices(struct dm_table *t);
 void dm_table_presuspend_targets(struct dm_table *t);
 void dm_table_presuspend_undo_targets(struct dm_table *t);
-- 
2.31.1