[PATCH 6.1 021/181] blk-mq: move the srcu_struct used for quiescing to the tagset

3 Apr 2023

From: Christoph Hellwig hch@lst.de
[ Upstream commit 80bd4a7aab4c9ce59bf5e35fdf52aa23d8a3c9f5 ]
All I/O submissions have fairly similar latencies, and a tagset-wide
quiesce is a fairly common operation.
Signed-off-by: Christoph Hellwig hch@lst.de
Reviewed-by: Keith Busch kbusch@kernel.org
Reviewed-by: Ming Lei ming.lei@redhat.com
Reviewed-by: Chao Leng lengchao@huawei.com
Reviewed-by: Sagi Grimberg sagi@grimberg.me
Reviewed-by: Hannes Reinecke hare@suse.de
Reviewed-by: Chaitanya Kulkarni kch@nvidia.com
Link: https://lore.kernel.org/r/20221101150050.3510-12-hch@lst.de
[axboe: fix whitespace]
Signed-off-by: Jens Axboe axboe@kernel.dk
Stable-dep-of: 00e885efcfbb ("blk-mq: fix "bad unlock balance detected" on q->srcu in __blk_mq_run_dispatch_ops")
Signed-off-by: Sasha Levin sashal@kernel.org
---
 block/blk-core.c       | 27 +++++----------------------
 block/blk-mq.c         | 33 +++++++++++++++++++++++++--------
 block/blk-mq.h         | 14 +++++++-------
 block/blk-sysfs.c      |  9 ++-------
 block/blk.h            |  9 +--------
 block/genhd.c          |  2 +-
 include/linux/blk-mq.h |  4 ++++
 include/linux/blkdev.h |  9 ---------
 8 files changed, 45 insertions(+), 62 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 24ee7785a5ad5..d5da62bb4bc06 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -65,7 +65,6 @@ DEFINE_IDA(blk_queue_ida);
  * For queue allocation
  */
 struct kmem_cache *blk_requestq_cachep;
-struct kmem_cache *blk_requestq_srcu_cachep;
/*
  * Controlling structure to kblockd
@@ -373,26 +372,20 @@ static void blk_timeout_work(struct work_struct *work)
 {
 }
-struct request_queue *blk_alloc_queue(int node_id, bool alloc_srcu)
+struct request_queue *blk_alloc_queue(int node_id)
 {
    struct request_queue *q;
-	q = kmem_cache_alloc_node(blk_get_queue_kmem_cache(alloc_srcu),
-			GFP_KERNEL | __GFP_ZERO, node_id);
+	q = kmem_cache_alloc_node(blk_requestq_cachep, GFP_KERNEL | __GFP_ZERO,
+				  node_id);
    if (!q)
    	return NULL;
-	if (alloc_srcu) {
-		blk_queue_flag_set(QUEUE_FLAG_HAS_SRCU, q);
-		if (init_srcu_struct(q->srcu) != 0)
-			goto fail_q;
-	}
-
    q->last_merge = NULL;
q->id = ida_alloc(&blk_queue_ida, GFP_KERNEL);
    if (q->id < 0)
-		goto fail_srcu;
+		goto fail_q;
q->stats = blk_alloc_queue_stats();
    if (!q->stats)
@@ -434,11 +427,8 @@ struct request_queue *blk_alloc_queue(int node_id, bool alloc_srcu)
    blk_free_queue_stats(q->stats);
 fail_id:
    ida_free(&blk_queue_ida, q->id);
-fail_srcu:
-	if (alloc_srcu)
-		cleanup_srcu_struct(q->srcu);
 fail_q:
-	kmem_cache_free(blk_get_queue_kmem_cache(alloc_srcu), q);
+	kmem_cache_free(blk_requestq_cachep, q);
    return NULL;
 }
@@ -1190,9 +1180,6 @@ int __init blk_dev_init(void)
    		sizeof_field(struct request, cmd_flags));
    BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 *
    		sizeof_field(struct bio, bi_opf));
-	BUILD_BUG_ON(ALIGN(offsetof(struct request_queue, srcu),
-			   __alignof__(struct request_queue)) !=
-		     sizeof(struct request_queue));
/* used for unplugging and affects IO latency/throughput - HIGHPRI */
    kblockd_workqueue = alloc_workqueue("kblockd",
@@ -1203,10 +1190,6 @@ int __init blk_dev_init(void)
    blk_requestq_cachep = kmem_cache_create("request_queue",
    		sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
-	blk_requestq_srcu_cachep = kmem_cache_create("request_queue_srcu",
-			sizeof(struct request_queue) +
-			sizeof(struct srcu_struct), 0, SLAB_PANIC, NULL);
-
    blk_debugfs_root = debugfs_create_dir("block", NULL);
return 0;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index aa67a52c5a069..f8c97d75b8d1a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -261,8 +261,8 @@ EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
  */
 void blk_mq_wait_quiesce_done(struct request_queue *q)
 {
-	if (blk_queue_has_srcu(q))
-		synchronize_srcu(q->srcu);
+	if (q->tag_set->flags & BLK_MQ_F_BLOCKING)
+		synchronize_srcu(q->tag_set->srcu);
    else
    	synchronize_rcu();
 }
@@ -4022,7 +4022,7 @@ static struct request_queue *blk_mq_init_queue_data(struct blk_mq_tag_set *set,
    struct request_queue *q;
    int ret;
-	q = blk_alloc_queue(set->numa_node, set->flags & BLK_MQ_F_BLOCKING);
+	q = blk_alloc_queue(set->numa_node);
    if (!q)
    	return ERR_PTR(-ENOMEM);
    q->queuedata = queuedata;
@@ -4194,9 +4194,6 @@ static void blk_mq_update_poll_flag(struct request_queue *q)
 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));
-
    /* mark the queue as mq asap */
    q->mq_ops = set->ops;
@@ -4453,8 +4450,18 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
    if (set->nr_maps == 1 && set->nr_hw_queues > nr_cpu_ids)
    	set->nr_hw_queues = nr_cpu_ids;
-	if (blk_mq_alloc_tag_set_tags(set, set->nr_hw_queues) < 0)
-		return -ENOMEM;
+	if (set->flags & BLK_MQ_F_BLOCKING) {
+		set->srcu = kmalloc(sizeof(*set->srcu), GFP_KERNEL);
+		if (!set->srcu)
+			return -ENOMEM;
+		ret = init_srcu_struct(set->srcu);
+		if (ret)
+			goto out_free_srcu;
+	}
+
+	ret = blk_mq_alloc_tag_set_tags(set, set->nr_hw_queues);
+	if (ret)
+		goto out_cleanup_srcu;
ret = -ENOMEM;
    for (i = 0; i < set->nr_maps; i++) {
@@ -4484,6 +4491,12 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
    }
    kfree(set->tags);
    set->tags = NULL;
+out_cleanup_srcu:
+	if (set->flags & BLK_MQ_F_BLOCKING)
+		cleanup_srcu_struct(set->srcu);
+out_free_srcu:
+	if (set->flags & BLK_MQ_F_BLOCKING)
+		kfree(set->srcu);
    return ret;
 }
 EXPORT_SYMBOL(blk_mq_alloc_tag_set);
@@ -4523,6 +4536,10 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
kfree(set->tags);
    set->tags = NULL;
+	if (set->flags & BLK_MQ_F_BLOCKING) {
+		cleanup_srcu_struct(set->srcu);
+		kfree(set->srcu);
+	}
 }
 EXPORT_SYMBOL(blk_mq_free_tag_set);
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 0b2870839cdd6..ef59fee62780d 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -377,17 +377,17 @@ 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)) {				\
-		rcu_read_lock();				\
-		(dispatch_ops);					\
-		rcu_read_unlock();				\
-	} else {						\
+	if ((q)->tag_set->flags & BLK_MQ_F_BLOCKING) {		\
    	int srcu_idx;					\
    							\
    	might_sleep_if(check_sleep);			\
-		srcu_idx = srcu_read_lock((q)->srcu);		\
+		srcu_idx = srcu_read_lock((q)->tag_set->srcu);	\
    	(dispatch_ops);					\
-		srcu_read_unlock((q)->srcu, srcu_idx);		\
+		srcu_read_unlock((q)->tag_set->srcu, srcu_idx);	\
+	} else {						\
+		rcu_read_lock();				\
+		(dispatch_ops);					\
+		rcu_read_unlock();				\
    }							\
 } while (0)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index e71b3b43927c0..e7871665825a3 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -739,10 +739,8 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr,
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_requestq_cachep,
+			container_of(rcu_head, struct request_queue, rcu_head));
 }
/**
@@ -779,9 +777,6 @@ static void blk_release_queue(struct kobject *kobj)
    if (queue_is_mq(q))
    	blk_mq_release(q);
-	if (blk_queue_has_srcu(q))
-		cleanup_srcu_struct(q->srcu);
-
    ida_free(&blk_queue_ida, q->id);
    call_rcu(&q->rcu_head, blk_free_queue_rcu);
 }
diff --git a/block/blk.h b/block/blk.h
index a186ea20f39d8..4849a2efa4c50 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -27,7 +27,6 @@ struct blk_flush_queue {
 };
extern struct kmem_cache *blk_requestq_cachep;
-extern struct kmem_cache *blk_requestq_srcu_cachep;
 extern struct kobj_type blk_queue_ktype;
 extern struct ida blk_queue_ida;
@@ -428,13 +427,7 @@ int bio_add_hw_page(struct request_queue *q, struct bio *bio,
    	struct page *page, unsigned int len, unsigned int offset,
    	unsigned int max_sectors, bool *same_page);
-static inline struct kmem_cache *blk_get_queue_kmem_cache(bool srcu)
-{
-	if (srcu)
-		return blk_requestq_srcu_cachep;
-	return blk_requestq_cachep;
-}
-struct request_queue *blk_alloc_queue(int node_id, bool alloc_srcu);
+struct request_queue *blk_alloc_queue(int node_id);
int disk_scan_partitions(struct gendisk *disk, fmode_t mode);
diff --git a/block/genhd.c b/block/genhd.c
index 0b6928e948f31..4db1f905514c5 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1436,7 +1436,7 @@ struct gendisk *__blk_alloc_disk(int node, struct lock_class_key *lkclass)
    struct request_queue *q;
    struct gendisk *disk;
-	q = blk_alloc_queue(node, false);
+	q = blk_alloc_queue(node);
    if (!q)
    	return NULL;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index a9764cbf7f8d2..8e942e36f1c48 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -7,6 +7,7 @@
 #include <linux/lockdep.h>
 #include <linux/scatterlist.h>
 #include <linux/prefetch.h>
+#include <linux/srcu.h>
struct blk_mq_tags;
 struct blk_flush_queue;
@@ -507,6 +508,8 @@ enum hctx_type {
  * @tag_list_lock: Serializes tag_list accesses.
  * @tag_list:	   List of the request queues that use this tag set. See also
  *		   request_queue.tag_set_list.
+ * @srcu:	   Use as lock when type of the request queue is blocking
+ *		   (BLK_MQ_F_BLOCKING).
  */
 struct blk_mq_tag_set {
    struct blk_mq_queue_map	map[HCTX_MAX_TYPES];
@@ -527,6 +530,7 @@ struct blk_mq_tag_set {
struct mutex		tag_list_lock;
    struct list_head	tag_list;
+	struct srcu_struct	*srcu;
 };
/**
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 891f8cbcd0436..36c286d22fb23 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -22,7 +22,6 @@
 #include <linux/blkzoned.h>
 #include <linux/sched.h>
 #include <linux/sbitmap.h>
-#include <linux/srcu.h>
 #include <linux/uuid.h>
 #include <linux/xarray.h>
@@ -544,18 +543,11 @@ struct request_queue {
    struct mutex		debugfs_mutex;
bool			mq_sysfs_init_done;
-
-	/**
-	 * @srcu: Sleepable RCU. Use as lock when type of the request queue
-	 * is blocking (BLK_MQ_F_BLOCKING). Must be the last member
-	 */
-	struct srcu_struct	srcu[];
 };
/* 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_NOMERGES     3	/* disable merge attempts */
 #define QUEUE_FLAG_SAME_COMP	4	/* complete on same CPU-group */
 #define QUEUE_FLAG_FAIL_IO	5	/* fake timeout */
@@ -591,7 +583,6 @@ 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_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)
 #define blk_queue_noxmerges(q)	\
-- 
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[PATCH 6.1 021/181] blk-mq: move the srcu_struct used for quiescing to the tagset