[mirror_ubuntu-hirsute-kernel.git] / block / blk-mq.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef INT_BLK_MQ_H
#define INT_BLK_MQ_H

#include "blk-stat.h"
#include "blk-mq-tag.h"

struct blk_mq_tag_set;

struct blk_mq_ctxs {
	struct kobject kobj;
	struct blk_mq_ctx __percpu	*queue_ctx;
};

/**
 * struct blk_mq_ctx - State for a software queue facing the submitting CPUs
 */
struct blk_mq_ctx {
	struct {
		spinlock_t		lock;
		struct list_head	rq_lists[HCTX_MAX_TYPES];
	} ____cacheline_aligned_in_smp;

	unsigned int		cpu;
	unsigned short		index_hw[HCTX_MAX_TYPES];
	struct blk_mq_hw_ctx 	*hctxs[HCTX_MAX_TYPES];

	/* incremented at dispatch time */
	unsigned long		rq_dispatched[2];
	unsigned long		rq_merged;

	/* incremented at completion time */
	unsigned long		____cacheline_aligned_in_smp rq_completed[2];

	struct request_queue	*queue;
	struct blk_mq_ctxs      *ctxs;
	struct kobject		kobj;
} ____cacheline_aligned_in_smp;

void blk_mq_exit_queue(struct request_queue *q);
int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr);
void blk_mq_wake_waiters(struct request_queue *q);
bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *,
			     unsigned int);
void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
				bool kick_requeue_list);
void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list);
struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
					struct blk_mq_ctx *start);
void blk_mq_put_rq_ref(struct request *rq);

/*
 * Internal helpers for allocating/freeing the request map
 */
void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
		     unsigned int hctx_idx);
void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags);
struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
					unsigned int hctx_idx,
					unsigned int nr_tags,
					unsigned int reserved_tags,
					unsigned int flags);
int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
		     unsigned int hctx_idx, unsigned int depth);

/*
 * Internal helpers for request insertion into sw queues
 */
void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
				bool at_head);
void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
				  bool run_queue);
void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
				struct list_head *list);

/* Used by blk_insert_cloned_request() to issue request directly */
blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last);
void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
				    struct list_head *list);

/*
 * CPU -> queue mappings
 */
extern int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int);

/*
 * blk_mq_map_queue_type() - map (hctx_type,cpu) to hardware queue
 * @q: request queue
 * @type: the hctx type index
 * @cpu: CPU
 */
static inline struct blk_mq_hw_ctx *blk_mq_map_queue_type(struct request_queue *q,
							  enum hctx_type type,
							  unsigned int cpu)
{
	return q->queue_hw_ctx[q->tag_set->map[type].mq_map[cpu]];
}

/*
 * blk_mq_map_queue() - map (cmd_flags,type) to hardware queue
 * @q: request queue
 * @flags: request command flags
 * @ctx: software queue cpu ctx
 */
static inline struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *q,
						     unsigned int flags,
						     struct blk_mq_ctx *ctx)
{
	enum hctx_type type = HCTX_TYPE_DEFAULT;

	/*
	 * The caller ensure that if REQ_HIPRI, poll must be enabled.
	 */
	if (flags & REQ_HIPRI)
		type = HCTX_TYPE_POLL;
	else if ((flags & REQ_OP_MASK) == REQ_OP_READ)
		type = HCTX_TYPE_READ;
	
	return ctx->hctxs[type];
}

/*
 * sysfs helpers
 */
extern void blk_mq_sysfs_init(struct request_queue *q);
extern void blk_mq_sysfs_deinit(struct request_queue *q);
extern int __blk_mq_register_dev(struct device *dev, struct request_queue *q);
extern int blk_mq_sysfs_register(struct request_queue *q);
extern void blk_mq_sysfs_unregister(struct request_queue *q);
extern void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx);

void blk_mq_release(struct request_queue *q);

static inline struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
					   unsigned int cpu)
{
	return per_cpu_ptr(q->queue_ctx, cpu);
}

/*
 * This assumes per-cpu software queueing queues. They could be per-node
 * as well, for instance. For now this is hardcoded as-is. Note that we don't
 * care about preemption, since we know the ctx's are persistent. This does
 * mean that we can't rely on ctx always matching the currently running CPU.
 */
static inline struct blk_mq_ctx *blk_mq_get_ctx(struct request_queue *q)
{
	return __blk_mq_get_ctx(q, raw_smp_processor_id());
}

struct blk_mq_alloc_data {
	/* input parameter */
	struct request_queue *q;
	blk_mq_req_flags_t flags;
	unsigned int shallow_depth;
	unsigned int cmd_flags;

	/* input & output parameter */
	struct blk_mq_ctx *ctx;
	struct blk_mq_hw_ctx *hctx;
};

static inline bool blk_mq_is_sbitmap_shared(unsigned int flags)
{
	return flags & BLK_MQ_F_TAG_HCTX_SHARED;
}

static inline struct blk_mq_tags *blk_mq_tags_from_data(struct blk_mq_alloc_data *data)
{
	if (data->q->elevator)
		return data->hctx->sched_tags;

	return data->hctx->tags;
}

static inline bool blk_mq_hctx_stopped(struct blk_mq_hw_ctx *hctx)
{
	return test_bit(BLK_MQ_S_STOPPED, &hctx->state);
}

static inline bool blk_mq_hw_queue_mapped(struct blk_mq_hw_ctx *hctx)
{
	return hctx->nr_ctx && hctx->tags;
}

unsigned int blk_mq_in_flight(struct request_queue *q,
		struct block_device *part);
void blk_mq_in_flight_rw(struct request_queue *q, struct block_device *part,
		unsigned int inflight[2]);

static inline void blk_mq_put_dispatch_budget(struct request_queue *q)
{
	if (q->mq_ops->put_budget)
		q->mq_ops->put_budget(q);
}

static inline bool blk_mq_get_dispatch_budget(struct request_queue *q)
{
	if (q->mq_ops->get_budget)
		return q->mq_ops->get_budget(q);
	return true;
}

static inline void __blk_mq_inc_active_requests(struct blk_mq_hw_ctx *hctx)
{
	if (blk_mq_is_sbitmap_shared(hctx->flags))
		atomic_inc(&hctx->queue->nr_active_requests_shared_sbitmap);
	else
		atomic_inc(&hctx->nr_active);
}

static inline void __blk_mq_dec_active_requests(struct blk_mq_hw_ctx *hctx)
{
	if (blk_mq_is_sbitmap_shared(hctx->flags))
		atomic_dec(&hctx->queue->nr_active_requests_shared_sbitmap);
	else
		atomic_dec(&hctx->nr_active);
}

static inline int __blk_mq_active_requests(struct blk_mq_hw_ctx *hctx)
{
	if (blk_mq_is_sbitmap_shared(hctx->flags))
		return atomic_read(&hctx->queue->nr_active_requests_shared_sbitmap);
	return atomic_read(&hctx->nr_active);
}
static inline void __blk_mq_put_driver_tag(struct blk_mq_hw_ctx *hctx,
					   struct request *rq)
{
	blk_mq_put_tag(hctx->tags, rq->mq_ctx, rq->tag);
	rq->tag = BLK_MQ_NO_TAG;

	if (rq->rq_flags & RQF_MQ_INFLIGHT) {
		rq->rq_flags &= ~RQF_MQ_INFLIGHT;
		__blk_mq_dec_active_requests(hctx);
	}
}

static inline void blk_mq_put_driver_tag(struct request *rq)
{
	if (rq->tag == BLK_MQ_NO_TAG || rq->internal_tag == BLK_MQ_NO_TAG)
		return;

	__blk_mq_put_driver_tag(rq->mq_hctx, rq);
}

static inline void blk_mq_clear_mq_map(struct blk_mq_queue_map *qmap)
{
	int cpu;

	for_each_possible_cpu(cpu)
		qmap->mq_map[cpu] = 0;
}

/*
 * blk_mq_plug() - Get caller context plug
 * @q: request queue
 * @bio : the bio being submitted by the caller context
 *
 * Plugging, by design, may delay the insertion of BIOs into the elevator in
 * order to increase BIO merging opportunities. This however can cause BIO
 * insertion order to change from the order in which submit_bio() is being
 * executed in the case of multiple contexts concurrently issuing BIOs to a
 * device, even if these context are synchronized to tightly control BIO issuing
 * order. While this is not a problem with regular block devices, this ordering
 * change can cause write BIO failures with zoned block devices as these
 * require sequential write patterns to zones. Prevent this from happening by
 * ignoring the plug state of a BIO issuing context if the target request queue
 * is for a zoned block device and the BIO to plug is a write operation.
 *
 * Return current->plug if the bio can be plugged and NULL otherwise
 */
static inline struct blk_plug *blk_mq_plug(struct request_queue *q,
					   struct bio *bio)
{
	/*
	 * For regular block devices or read operations, use the context plug
	 * which may be NULL if blk_start_plug() was not executed.
	 */
	if (!blk_queue_is_zoned(q) || !op_is_write(bio_op(bio)))
		return current->plug;

	/* Zoned block device write operation case: do not plug the BIO */
	return NULL;
}

/*
 * For shared tag users, we track the number of currently active users
 * and attempt to provide a fair share of the tag depth for each of them.
 */
static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
				  struct sbitmap_queue *bt)
{
	unsigned int depth, users;

	if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED))
		return true;

	/*
	 * Don't try dividing an ant
	 */
	if (bt->sb.depth == 1)
		return true;

	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
		struct request_queue *q = hctx->queue;
		struct blk_mq_tag_set *set = q->tag_set;

		if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
			return true;
		users = atomic_read(&set->active_queues_shared_sbitmap);
	} else {
		if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
			return true;
		users = atomic_read(&hctx->tags->active_queues);
	}

	if (!users)
		return true;

	/*
	 * Allow at least some tags
	 */
	depth = max((bt->sb.depth + users - 1) / users, 4U);
	return __blk_mq_active_requests(hctx) < depth;
}


#endif
Commit	Line	Data
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
320ae51f JA	2	#ifndef INT_BLK_MQ_H
	3	#define INT_BLK_MQ_H
	4
cf43e6be	5	#include "blk-stat.h"
244c65a3	6	#include "blk-mq-tag.h"
cf43e6be	7
24d2f903 CH	8	struct blk_mq_tag_set;
24d2f903 CH	9
1db4909e ML	10	struct blk_mq_ctxs {
	11	struct kobject kobj;
	12	struct blk_mq_ctx __percpu *queue_ctx;
	13	};
	14
fe644072 LW	15	/**
	16	* struct blk_mq_ctx - State for a software queue facing the submitting CPUs
	17	*/
320ae51f JA	18	struct blk_mq_ctx {
	19	struct {
	20	spinlock_t lock;
c16d6b5a ML	21	struct list_head rq_lists[HCTX_MAX_TYPES];
c16d6b5a ML	22	} ____cacheline_aligned_in_smp;
320ae51f JA	23
320ae51f JA	24	unsigned int cpu;
f31967f0	25	unsigned short index_hw[HCTX_MAX_TYPES];
8ccdf4a3	26	struct blk_mq_hw_ctx *hctxs[HCTX_MAX_TYPES];
320ae51f JA	27
	28	/* incremented at dispatch time */
	29	unsigned long rq_dispatched[2];
	30	unsigned long rq_merged;
	31
	32	/* incremented at completion time */
	33	unsigned long ____cacheline_aligned_in_smp rq_completed[2];
	34
	35	struct request_queue *queue;
1db4909e	36	struct blk_mq_ctxs *ctxs;
320ae51f	37	struct kobject kobj;
4bb659b1	38	} ____cacheline_aligned_in_smp;
320ae51f	39
c7e2d94b	40	void blk_mq_exit_queue(struct request_queue *q);
e3a2b3f9	41	int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr);
aed3ea94	42	void blk_mq_wake_waiters(struct request_queue *q);
1fd40b5e ML	43	bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx hctx, struct list_head ,
1fd40b5e ML	44	unsigned int);
e6c98712 BVA	45	void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
e6c98712 BVA	46	bool kick_requeue_list);
2c3ad667	47	void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx hctx, struct list_head list);
b347689f ML	48	struct request blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx hctx,
b347689f ML	49	struct blk_mq_ctx *start);
4e4f3102	50	void blk_mq_put_rq_ref(struct request *rq);
2c3ad667 JA	51
	52	/*
	53	* Internal helpers for allocating/freeing the request map
	54	*/
cc71a6f4 JA	55	void blk_mq_free_rqs(struct blk_mq_tag_set set, struct blk_mq_tags tags,
cc71a6f4 JA	56	unsigned int hctx_idx);
1c0706a7	57	void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags);
cc71a6f4 JA	58	struct blk_mq_tags blk_mq_alloc_rq_map(struct blk_mq_tag_set set,
	59	unsigned int hctx_idx,
	60	unsigned int nr_tags,
1c0706a7 JG	61	unsigned int reserved_tags,
1c0706a7 JG	62	unsigned int flags);
cc71a6f4 JA	63	int blk_mq_alloc_rqs(struct blk_mq_tag_set set, struct blk_mq_tags tags,
cc71a6f4 JA	64	unsigned int hctx_idx, unsigned int depth);
2c3ad667 JA	65
	66	/*
	67	* Internal helpers for request insertion into sw queues
	68	*/
	69	void __blk_mq_insert_request(struct blk_mq_hw_ctx hctx, struct request rq,
	70	bool at_head);
01e99aec ML	71	void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
01e99aec ML	72	bool run_queue);
bd166ef1 JA	73	void blk_mq_insert_requests(struct blk_mq_hw_ctx hctx, struct blk_mq_ctx ctx,
bd166ef1 JA	74	struct list_head *list);
320ae51f	75
fd9c40f6 BVA	76	/* Used by blk_insert_cloned_request() to issue request directly */
fd9c40f6 BVA	77	blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last);
6ce3dd6e ML	78	void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
6ce3dd6e ML	79	struct list_head *list);
396eaf21	80
320ae51f JA	81	/*
	82	* CPU -> queue mappings
	83	*/
ed76e329	84	extern int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int);
320ae51f	85
b3c661b1 JA	86	/*
	87	* blk_mq_map_queue_type() - map (hctx_type,cpu) to hardware queue
	88	* @q: request queue
e20ba6e1	89	* @type: the hctx type index
b3c661b1 JA	90	* @cpu: CPU
	91	*/
	92	static inline struct blk_mq_hw_ctx blk_mq_map_queue_type(struct request_queue q,
e20ba6e1	93	enum hctx_type type,
b3c661b1	94	unsigned int cpu)
7d7e0f90	95	{
e20ba6e1	96	return q->queue_hw_ctx[q->tag_set->map[type].mq_map[cpu]];
7d7e0f90 CH	97	}
7d7e0f90 CH	98
b3c661b1 JA	99	/*
	100	* blk_mq_map_queue() - map (cmd_flags,type) to hardware queue
	101	* @q: request queue
	102	* @flags: request command flags
d220a214	103	* @ctx: software queue cpu ctx
b3c661b1 JA	104	*/
	105	static inline struct blk_mq_hw_ctx blk_mq_map_queue(struct request_queue q,
	106	unsigned int flags,
8ccdf4a3	107	struct blk_mq_ctx *ctx)
ff2c5660	108	{
e20ba6e1 CH	109	enum hctx_type type = HCTX_TYPE_DEFAULT;
e20ba6e1 CH	110
bb94aea1 JW	111	/*
	112	* The caller ensure that if REQ_HIPRI, poll must be enabled.
	113	*/
	114	if (flags & REQ_HIPRI)
e20ba6e1	115	type = HCTX_TYPE_POLL;
bb94aea1	116	else if ((flags & REQ_OP_MASK) == REQ_OP_READ)
e20ba6e1	117	type = HCTX_TYPE_READ;
5aceaeb2	118
8ccdf4a3	119	return ctx->hctxs[type];
ff2c5660 JA	120	}
ff2c5660 JA	121
67aec14c JA	122	/*
	123	* sysfs helpers
	124	*/
737f98cf	125	extern void blk_mq_sysfs_init(struct request_queue *q);
7ea5fe31	126	extern void blk_mq_sysfs_deinit(struct request_queue *q);
2d0364c8	127	extern int __blk_mq_register_dev(struct device dev, struct request_queue q);
67aec14c JA	128	extern int blk_mq_sysfs_register(struct request_queue *q);
67aec14c JA	129	extern void blk_mq_sysfs_unregister(struct request_queue *q);
868f2f0b	130	extern void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx);
67aec14c	131
e09aae7e ML	132	void blk_mq_release(struct request_queue *q);
e09aae7e ML	133
1aecfe48 ML	134	static inline struct blk_mq_ctx __blk_mq_get_ctx(struct request_queue q,
	135	unsigned int cpu)
	136	{
	137	return per_cpu_ptr(q->queue_ctx, cpu);
	138	}
	139
	140	/*
	141	* This assumes per-cpu software queueing queues. They could be per-node
	142	* as well, for instance. For now this is hardcoded as-is. Note that we don't
	143	* care about preemption, since we know the ctx's are persistent. This does
	144	* mean that we can't rely on ctx always matching the currently running CPU.
	145	*/
	146	static inline struct blk_mq_ctx blk_mq_get_ctx(struct request_queue q)
	147	{
c05f4220	148	return __blk_mq_get_ctx(q, raw_smp_processor_id());
1aecfe48 ML	149	}
1aecfe48 ML	150
cb96a42c ML	151	struct blk_mq_alloc_data {
	152	/* input parameter */
	153	struct request_queue *q;
9a95e4ef	154	blk_mq_req_flags_t flags;
229a9287	155	unsigned int shallow_depth;
f9afca4d	156	unsigned int cmd_flags;
cb96a42c ML	157
	158	/* input & output parameter */
	159	struct blk_mq_ctx *ctx;
	160	struct blk_mq_hw_ctx *hctx;
	161	};
	162
32bc15af JG	163	static inline bool blk_mq_is_sbitmap_shared(unsigned int flags)
	164	{
	165	return flags & BLK_MQ_F_TAG_HCTX_SHARED;
	166	}
	167
4941115b JA	168	static inline struct blk_mq_tags blk_mq_tags_from_data(struct blk_mq_alloc_data data)
4941115b JA	169	{
42fdc5e4	170	if (data->q->elevator)
bd166ef1 JA	171	return data->hctx->sched_tags;
bd166ef1 JA	172
4941115b JA	173	return data->hctx->tags;
	174	}
	175
5d1b25c1 BVA	176	static inline bool blk_mq_hctx_stopped(struct blk_mq_hw_ctx *hctx)
	177	{
	178	return test_bit(BLK_MQ_S_STOPPED, &hctx->state);
	179	}
	180
19c66e59 ML	181	static inline bool blk_mq_hw_queue_mapped(struct blk_mq_hw_ctx *hctx)
	182	{
	183	return hctx->nr_ctx && hctx->tags;
	184	}
	185
8446fe92 CH	186	unsigned int blk_mq_in_flight(struct request_queue *q,
	187	struct block_device *part);
	188	void blk_mq_in_flight_rw(struct request_queue q, struct block_device part,
	189	unsigned int inflight[2]);
f299b7c7	190
65c76369	191	static inline void blk_mq_put_dispatch_budget(struct request_queue *q)
de148297	192	{
de148297	193	if (q->mq_ops->put_budget)
65c76369	194	q->mq_ops->put_budget(q);
de148297 ML	195	}
de148297 ML	196
65c76369	197	static inline bool blk_mq_get_dispatch_budget(struct request_queue *q)
de148297	198	{
de148297	199	if (q->mq_ops->get_budget)
65c76369	200	return q->mq_ops->get_budget(q);
88022d72	201	return true;
de148297 ML	202	}
de148297 ML	203
bccf5e26 JG	204	static inline void __blk_mq_inc_active_requests(struct blk_mq_hw_ctx *hctx)
	205	{
	206	if (blk_mq_is_sbitmap_shared(hctx->flags))
	207	atomic_inc(&hctx->queue->nr_active_requests_shared_sbitmap);
	208	else
	209	atomic_inc(&hctx->nr_active);
	210	}
	211
	212	static inline void __blk_mq_dec_active_requests(struct blk_mq_hw_ctx *hctx)
	213	{
	214	if (blk_mq_is_sbitmap_shared(hctx->flags))
	215	atomic_dec(&hctx->queue->nr_active_requests_shared_sbitmap);
	216	else
	217	atomic_dec(&hctx->nr_active);
	218	}
	219
	220	static inline int __blk_mq_active_requests(struct blk_mq_hw_ctx *hctx)
	221	{
	222	if (blk_mq_is_sbitmap_shared(hctx->flags))
	223	return atomic_read(&hctx->queue->nr_active_requests_shared_sbitmap);
	224	return atomic_read(&hctx->nr_active);
	225	}
4e2f62e5 JA	226	static inline void __blk_mq_put_driver_tag(struct blk_mq_hw_ctx *hctx,
	227	struct request *rq)
	228	{
	229	blk_mq_put_tag(hctx->tags, rq->mq_ctx, rq->tag);
	230	rq->tag = BLK_MQ_NO_TAG;
	231
	232	if (rq->rq_flags & RQF_MQ_INFLIGHT) {
	233	rq->rq_flags &= ~RQF_MQ_INFLIGHT;
bccf5e26	234	__blk_mq_dec_active_requests(hctx);
4e2f62e5 JA	235	}
	236	}
	237
	238	static inline void blk_mq_put_driver_tag(struct request *rq)
	239	{
	240	if (rq->tag == BLK_MQ_NO_TAG \|\| rq->internal_tag == BLK_MQ_NO_TAG)
	241	return;
	242
	243	__blk_mq_put_driver_tag(rq->mq_hctx, rq);
	244	}
	245
ed76e329	246	static inline void blk_mq_clear_mq_map(struct blk_mq_queue_map *qmap)
0da73d00 MI	247	{
	248	int cpu;
	249
	250	for_each_possible_cpu(cpu)
ed76e329	251	qmap->mq_map[cpu] = 0;
0da73d00 MI	252	}
0da73d00 MI	253
b49773e7 DLM	254	/*
	255	* blk_mq_plug() - Get caller context plug
	256	* @q: request queue
	257	* @bio : the bio being submitted by the caller context
	258	*
	259	* Plugging, by design, may delay the insertion of BIOs into the elevator in
	260	* order to increase BIO merging opportunities. This however can cause BIO
	261	* insertion order to change from the order in which submit_bio() is being
	262	* executed in the case of multiple contexts concurrently issuing BIOs to a
	263	* device, even if these context are synchronized to tightly control BIO issuing
	264	* order. While this is not a problem with regular block devices, this ordering
	265	* change can cause write BIO failures with zoned block devices as these
	266	* require sequential write patterns to zones. Prevent this from happening by
	267	* ignoring the plug state of a BIO issuing context if the target request queue
	268	* is for a zoned block device and the BIO to plug is a write operation.
	269	*
	270	* Return current->plug if the bio can be plugged and NULL otherwise
	271	*/
	272	static inline struct blk_plug blk_mq_plug(struct request_queue q,
	273	struct bio *bio)
	274	{
	275	/*
	276	* For regular block devices or read operations, use the context plug
	277	* which may be NULL if blk_start_plug() was not executed.
	278	*/
	279	if (!blk_queue_is_zoned(q) \|\| !op_is_write(bio_op(bio)))
	280	return current->plug;
	281
	282	/* Zoned block device write operation case: do not plug the BIO */
	283	return NULL;
	284	}
	285
a0235d23 JG	286	/*
	287	* For shared tag users, we track the number of currently active users
	288	* and attempt to provide a fair share of the tag depth for each of them.
	289	*/
	290	static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
	291	struct sbitmap_queue *bt)
	292	{
	293	unsigned int depth, users;
	294
	295	if (!hctx \|\| !(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED))
	296	return true;
a0235d23 JG	297
	298	/*
	299	* Don't try dividing an ant
	300	*/
	301	if (bt->sb.depth == 1)
	302	return true;
	303
f1b49fdc JG	304	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
	305	struct request_queue *q = hctx->queue;
	306	struct blk_mq_tag_set *set = q->tag_set;
	307
2569063c	308	if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
f1b49fdc JG	309	return true;
	310	users = atomic_read(&set->active_queues_shared_sbitmap);
	311	} else {
	312	if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
	313	return true;
	314	users = atomic_read(&hctx->tags->active_queues);
	315	}
	316
a0235d23 JG	317	if (!users)
	318	return true;
	319
	320	/*
	321	* Allow at least some tags
	322	*/
	323	depth = max((bt->sb.depth + users - 1) / users, 4U);
bccf5e26	324	return __blk_mq_active_requests(hctx) < depth;
a0235d23 JG	325	}
	326
	327
320ae51f	328	#endif