Ming Lei <ming....@redhat.com> writes:
> Now we reuse queue flag of QUEUE_FLAG_HAS_SRCU for both having srcu and
> BLK_MQ_F_BLOCKING. Actually they are two things: one is that srcu is
> allocated inside queue, another is that we need to handle blocking
> ->queue_rq. So far this way works as expected.
>
> dm-rq needs to set BLK_MQ_F_BLOCKING if any underlying queue is
> marked as BLK_MQ_F_BLOCKING. But dm queue is allocated before tagset
> is allocated, one doable way is to always allocate SRCU for dm
> queue, then set BLK_MQ_F_BLOCKING for the tagset if it is required,
> meantime we can mark the request queue as supporting blocking
> ->queue_rq.
>
> So add one new flag of QUEUE_FLAG_BLOCKING for supporting blocking
> ->queue_rq only, and use one private field to describe if request
> queue has allocated srcu instance.
OK, so you switched to has_srcu because it's an internaly only detail,
that makes sense. I think testing for blocking makes more sense than
testing for the existence of srcu, so this actually makes the code a bit
more readable in my opinion.
Reviewed-by: Jeff Moyer <jmo...@redhat.com>
>
> Signed-off-by: Ming Lei <ming....@redhat.com>
> ---
> block/blk-core.c | 2 +-
> block/blk-mq.c | 6 +++---
> block/blk-mq.h | 2 +-
> block/blk-sysfs.c | 2 +-
> include/linux/blkdev.h | 5 +++--
> 5 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 10619fd83c1b..7ba806a4e779 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -449,7 +449,7 @@ struct request_queue *blk_alloc_queue(int node_id, bool
> alloc_srcu)
> return NULL;
>
> if (alloc_srcu) {
> - blk_queue_flag_set(QUEUE_FLAG_HAS_SRCU, q);
> + q->has_srcu = true;
> if (init_srcu_struct(q->srcu) != 0)
> goto fail_q;
> }
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 0d7c9d3e0329..1408a6b8ccdc 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -259,7 +259,7 @@ EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
> */
> void blk_mq_wait_quiesce_done(struct request_queue *q)
> {
> - if (blk_queue_has_srcu(q))
> + if (blk_queue_blocking(q))
> synchronize_srcu(q->srcu);
> else
> synchronize_rcu();
> @@ -4024,8 +4024,8 @@ static void blk_mq_realloc_hw_ctxs(struct
> blk_mq_tag_set *set,
> int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
> struct request_queue *q)
> {
> - WARN_ON_ONCE(blk_queue_has_srcu(q) !=
> - !!(set->flags & BLK_MQ_F_BLOCKING));
> + if (set->flags & BLK_MQ_F_BLOCKING)
> + blk_queue_flag_set(QUEUE_FLAG_BLOCKING, q);
>
> /* mark the queue as mq asap */
> q->mq_ops = set->ops;
> diff --git a/block/blk-mq.h b/block/blk-mq.h
> index 948791ea2a3e..9601918e2034 100644
> --- a/block/blk-mq.h
> +++ b/block/blk-mq.h
> @@ -377,7 +377,7 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx
> *hctx,
> /* run the code block in @dispatch_ops with rcu/srcu read lock held */
> #define __blk_mq_run_dispatch_ops(q, check_sleep, dispatch_ops) \
> do { \
> - if (!blk_queue_has_srcu(q)) { \
> + if (!blk_queue_blocking(q)) { \
> rcu_read_lock(); \
> (dispatch_ops); \
> rcu_read_unlock(); \
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index e20eadfcf5c8..af89fabb58e3 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -736,7 +736,7 @@ static void blk_free_queue_rcu(struct rcu_head *rcu_head)
> struct request_queue *q = container_of(rcu_head, struct request_queue,
> rcu_head);
>
> - kmem_cache_free(blk_get_queue_kmem_cache(blk_queue_has_srcu(q)), q);
> + kmem_cache_free(blk_get_queue_kmem_cache(q->has_srcu), q);
> }
>
> /* Unconfigure the I/O scheduler and dissociate from the cgroup controller.
> */
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index c80cfaefc0a8..d84abdb294c4 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -365,6 +365,7 @@ struct request_queue {
> #endif
>
> bool mq_sysfs_init_done;
> + bool has_srcu;
>
> #define BLK_MAX_WRITE_HINTS 5
> u64 write_hints[BLK_MAX_WRITE_HINTS];
> @@ -385,7 +386,7 @@ struct request_queue {
> /* Keep blk_queue_flag_name[] in sync with the definitions below */
> #define QUEUE_FLAG_STOPPED 0 /* queue is stopped */
> #define QUEUE_FLAG_DYING 1 /* queue being torn down */
> -#define QUEUE_FLAG_HAS_SRCU 2 /* SRCU is allocated */
> +#define QUEUE_FLAG_BLOCKING 2 /* ->queue_rq may block */
> #define QUEUE_FLAG_NOMERGES 3 /* disable merge attempts */
> #define QUEUE_FLAG_SAME_COMP 4 /* complete on same CPU-group */
> #define QUEUE_FLAG_FAIL_IO 5 /* fake timeout */
> @@ -423,7 +424,7 @@ bool blk_queue_flag_test_and_set(unsigned int flag,
> struct request_queue *q);
>
> #define blk_queue_stopped(q) test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)
> #define blk_queue_dying(q) test_bit(QUEUE_FLAG_DYING, &(q)->queue_flags)
> -#define blk_queue_has_srcu(q) test_bit(QUEUE_FLAG_HAS_SRCU,
> &(q)->queue_flags)
> +#define blk_queue_blocking(q) test_bit(QUEUE_FLAG_BLOCKING,
> &(q)->queue_flags)
> #define blk_queue_dead(q) test_bit(QUEUE_FLAG_DEAD, &(q)->queue_flags)
> #define blk_queue_init_done(q) test_bit(QUEUE_FLAG_INIT_DONE,
> &(q)->queue_flags)
> #define blk_queue_nomerges(q) test_bit(QUEUE_FLAG_NOMERGES,
> &(q)->queue_flags)
--
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