On Tue, Dec 21 2021 at 9:14P -0500,
Ming Lei <ming.lei@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxx>
> ---
> 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);
As you can see, dm_table_get_immutable_target(t) is called here ^
Rather than pass 'blocking' in, please just call dm_table_has_blocking_dev(t);
But not a big deal, I can clean that up once this gets committed...
> 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
>
Reviewed-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Late, given holidays we know why, but this patchset is needed for 5.17
(maybe with added: 'Fixes: 704b914f15fb7 "blk-mq: move srcu from
blk_mq_hw_ctx to request_queue"' to this 3rd patch?)
Jens, can you please pick this patchset up for 5.17?
Thanks,
Mike
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