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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef BLK_MQ_H
#define BLK_MQ_H
#include <linux/blkdev.h>
#include <linux/sbitmap.h>
#include <linux/srcu.h>
struct blk_mq_tags;
struct blk_flush_queue;
* struct blk_mq_hw_ctx - State for a hardware queue facing the hardware
* block device
struct blk_mq_hw_ctx {
struct {
/** @lock: Protects the dispatch list. */
spinlock_t lock;
* @dispatch: Used for requests that are ready to be
* dispatched to the hardware but for some reason (e.g. lack of
* resources) could not be sent to the hardware. As soon as the
* driver can send new requests, requests at this list will
* be sent first for a fairer dispatch.
struct list_head dispatch;
* @state: BLK_MQ_S_* flags. Defines the state of the hw
* queue (active, scheduled to restart, stopped).
unsigned long state;
} ____cacheline_aligned_in_smp;
* @run_work: Used for scheduling a hardware queue run at a later time.
struct delayed_work run_work;
/** @cpumask: Map of available CPUs where this hctx can run. */
cpumask_var_t cpumask;
* @next_cpu: Used by blk_mq_hctx_next_cpu() for round-robin CPU
* selection from @cpumask.
int next_cpu;
* @next_cpu_batch: Counter of how many works left in the batch before
* changing to the next CPU.
int next_cpu_batch;
/** @flags: BLK_MQ_F_* flags. Defines the behaviour of the queue. */
unsigned long flags;
* @sched_data: Pointer owned by the IO scheduler attached to a request
* queue. It's up to the IO scheduler how to use this pointer.
void *sched_data;
* @queue: Pointer to the request queue that owns this hardware context.
struct request_queue *queue;
/** @fq: Queue of requests that need to perform a flush operation. */
struct blk_flush_queue *fq;
* @driver_data: Pointer to data owned by the block driver that created
* this hctx
void *driver_data;
* @ctx_map: Bitmap for each software queue. If bit is on, there is a
* pending request in that software queue.
struct sbitmap ctx_map;
* @dispatch_from: Software queue to be used when no scheduler was
* selected.
struct blk_mq_ctx *dispatch_from;
* @dispatch_busy: Number used by blk_mq_update_dispatch_busy() to
* decide if the hw_queue is busy using Exponential Weighted Moving
* Average algorithm.
unsigned int dispatch_busy;
/** @type: HCTX_TYPE_* flags. Type of hardware queue. */
unsigned short type;
/** @nr_ctx: Number of software queues. */
unsigned short nr_ctx;
/** @ctxs: Array of software queues. */
struct blk_mq_ctx **ctxs;
/** @dispatch_wait_lock: Lock for dispatch_wait queue. */
spinlock_t dispatch_wait_lock;
* @dispatch_wait: Waitqueue to put requests when there is no tag
* available at the moment, to wait for another try in the future.
wait_queue_entry_t dispatch_wait;
* @wait_index: Index of next available dispatch_wait queue to insert
* requests.
atomic_t wait_index;
* @tags: Tags owned by the block driver. A tag at this set is only
* assigned when a request is dispatched from a hardware queue.
struct blk_mq_tags *tags;
* @sched_tags: Tags owned by I/O scheduler. If there is an I/O
* scheduler associated with a request queue, a tag is assigned when
* that request is allocated. Else, this member is not used.
struct blk_mq_tags *sched_tags;
/** @queued: Number of queued requests. */
unsigned long queued;
/** @run: Number of dispatched requests. */
unsigned long run;
/** @dispatched: Number of dispatch requests by queue. */
unsigned long dispatched[BLK_MQ_MAX_DISPATCH_ORDER];
/** @numa_node: NUMA node the storage adapter has been connected to. */
unsigned int numa_node;
/** @queue_num: Index of this hardware queue. */
unsigned int queue_num;
* @nr_active: Number of active requests. Only used when a tag set is
* shared across request queues.
atomic_t nr_active;
* @elevator_queued: Number of queued requests on hctx.
atomic_t elevator_queued;
/** @cpuhp_online: List to store request if CPU is going to die */
struct hlist_node cpuhp_online;
/** @cpuhp_dead: List to store request if some CPU die. */
struct hlist_node cpuhp_dead;
/** @kobj: Kernel object for sysfs. */
struct kobject kobj;
/** @poll_considered: Count times blk_poll() was called. */
unsigned long poll_considered;
/** @poll_invoked: Count how many requests blk_poll() polled. */
unsigned long poll_invoked;
/** @poll_success: Count how many polled requests were completed. */
unsigned long poll_success;
* @debugfs_dir: debugfs directory for this hardware queue. Named
* as cpu<cpu_number>.
struct dentry *debugfs_dir;
/** @sched_debugfs_dir: debugfs directory for the scheduler. */
struct dentry *sched_debugfs_dir;
* @hctx_list: if this hctx is not in use, this is an entry in
* q->unused_hctx_list.
struct list_head hctx_list;
* @srcu: Sleepable RCU. Use as lock when type of the hardware queue is
* blocking (BLK_MQ_F_BLOCKING). Must be the last member - see also
* blk_mq_hw_ctx_size().
struct srcu_struct srcu[];
* struct blk_mq_queue_map - Map software queues to hardware queues
* @mq_map: CPU ID to hardware queue index map. This is an array
* with nr_cpu_ids elements. Each element has a value in the range
* [@queue_offset, @queue_offset + @nr_queues).
* @nr_queues: Number of hardware queues to map CPU IDs onto.
* @queue_offset: First hardware queue to map onto. Used by the PCIe NVMe
* driver to map each hardware queue type (enum hctx_type) onto a distinct
* set of hardware queues.
struct blk_mq_queue_map {
unsigned int *mq_map;
unsigned int nr_queues;
unsigned int queue_offset;
* enum hctx_type - Type of hardware queue
* @HCTX_TYPE_DEFAULT: All I/O not otherwise accounted for.
* @HCTX_TYPE_POLL: Polled I/O of any kind.
* @HCTX_MAX_TYPES: Number of types of hctx.
enum hctx_type {
* struct blk_mq_tag_set - tag set that can be shared between request queues
* @map: One or more ctx -> hctx mappings. One map exists for each
* hardware queue type (enum hctx_type) that the driver wishes
* to support. There are no restrictions on maps being of the
* same size, and it's perfectly legal to share maps between
* types.
* @nr_maps: Number of elements in the @map array. A number in the range
* @ops: Pointers to functions that implement block driver behavior.
* @nr_hw_queues: Number of hardware queues supported by the block driver that
* owns this data structure.
* @queue_depth: Number of tags per hardware queue, reserved tags included.
* @reserved_tags: Number of tags to set aside for BLK_MQ_REQ_RESERVED tag
* allocations.
* @cmd_size: Number of additional bytes to allocate per request. The block
* driver owns these additional bytes.
* @numa_node: NUMA node the storage adapter has been connected to.
* @timeout: Request processing timeout in jiffies.
* @flags: Zero or more BLK_MQ_F_* flags.
* @driver_data: Pointer to data owned by the block driver that created this
* tag set.
* @__bitmap_tags: A shared tags sbitmap, used over all hctx's
* @__breserved_tags:
* A shared reserved tags sbitmap, used over all hctx's
* @tags: Tag sets. One tag set per hardware queue. Has @nr_hw_queues
* elements.
* @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.
struct blk_mq_tag_set {
struct blk_mq_queue_map map[HCTX_MAX_TYPES];
unsigned int nr_maps;
const struct blk_mq_ops *ops;
unsigned int nr_hw_queues;
unsigned int queue_depth;
unsigned int reserved_tags;
unsigned int cmd_size;
int numa_node;
unsigned int timeout;
unsigned int flags;
void *driver_data;
atomic_t active_queues_shared_sbitmap;
struct sbitmap_queue __bitmap_tags;
struct sbitmap_queue __breserved_tags;
struct blk_mq_tags **tags;
struct mutex tag_list_lock;
struct list_head tag_list;
* struct blk_mq_queue_data - Data about a request inserted in a queue
* @rq: Request pointer.
* @last: If it is the last request in the queue.
struct blk_mq_queue_data {
struct request *rq;
bool last;
typedef bool (busy_iter_fn)(struct blk_mq_hw_ctx *, struct request *, void *,
typedef bool (busy_tag_iter_fn)(struct request *, void *, bool);
* struct blk_mq_ops - Callback functions that implements block driver
* behaviour.
struct blk_mq_ops {
* @queue_rq: Queue a new request from block IO.
blk_status_t (*queue_rq)(struct blk_mq_hw_ctx *,
const struct blk_mq_queue_data *);
* @commit_rqs: If a driver uses bd->last to judge when to submit
* requests to hardware, it must define this function. In case of errors
* that make us stop issuing further requests, this hook serves the
* purpose of kicking the hardware (which the last request otherwise
* would have done).
void (*commit_rqs)(struct blk_mq_hw_ctx *);
* @get_budget: Reserve budget before queue request, once .queue_rq is
* run, it is driver's responsibility to release the
* reserved budget. Also we have to handle failure case
* of .get_budget for avoiding I/O deadlock.
bool (*get_budget)(struct request_queue *);
* @put_budget: Release the reserved budget.
void (*put_budget)(struct request_queue *);
* @timeout: Called on request timeout.
enum blk_eh_timer_return (*timeout)(struct request *, bool);
* @poll: Called to poll for completion of a specific tag.
int (*poll)(struct blk_mq_hw_ctx *);
* @complete: Mark the request as complete.
void (*complete)(struct request *);
* @init_hctx: Called when the block layer side of a hardware queue has
* been set up, allowing the driver to allocate/init matching
* structures.
int (*init_hctx)(struct blk_mq_hw_ctx *, void *, unsigned int);
* @exit_hctx: Ditto for exit/teardown.
void (*exit_hctx)(struct blk_mq_hw_ctx *, unsigned int);
* @init_request: Called for every command allocated by the block layer
* to allow the driver to set up driver specific data.
* Tag greater than or equal to queue_depth is for setting up
* flush request.
int (*init_request)(struct blk_mq_tag_set *set, struct request *,
unsigned int, unsigned int);
* @exit_request: Ditto for exit/teardown.
void (*exit_request)(struct blk_mq_tag_set *set, struct request *,
unsigned int);
* @initialize_rq_fn: Called from inside blk_get_request().
void (*initialize_rq_fn)(struct request *rq);
* @cleanup_rq: Called before freeing one request which isn't completed
* yet, and usually for freeing the driver private data.
void (*cleanup_rq)(struct request *);
* @busy: If set, returns whether or not this queue currently is busy.
bool (*busy)(struct request_queue *);
* @map_queues: This allows drivers specify their own queue mapping by
* overriding the setup-time function that builds the mq_map.
int (*map_queues)(struct blk_mq_tag_set *set);
* @show_rq: Used by the debugfs implementation to show driver-specific
* information about a request.
void (*show_rq)(struct seq_file *m, struct request *rq);
enum {
* Set when this device requires underlying blk-mq device for
* completing IO:
BLK_MQ_F_NO_SCHED = 1 << 6,
/* hw queue is inactive after all its CPUs become offline */
#define BLK_MQ_FLAG_TO_ALLOC_POLICY(flags) \
#define BLK_ALLOC_POLICY_TO_MQ_FLAG(policy) \
((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \
struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);
struct request_queue *blk_mq_init_queue_data(struct blk_mq_tag_set *set,
void *queuedata);
struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
struct request_queue *q,
bool elevator_init);
struct request_queue *blk_mq_init_sq_queue(struct blk_mq_tag_set *set,
const struct blk_mq_ops *ops,
unsigned int queue_depth,
unsigned int set_flags);
void blk_mq_unregister_dev(struct device *, struct request_queue *);
int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set);
void blk_mq_free_tag_set(struct blk_mq_tag_set *set);
void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule);
void blk_mq_free_request(struct request *rq);
bool blk_mq_queue_inflight(struct request_queue *q);
enum {
/* return when out of requests */
BLK_MQ_REQ_NOWAIT = (__force blk_mq_req_flags_t)(1 << 0),
/* allocate from reserved pool */
BLK_MQ_REQ_RESERVED = (__force blk_mq_req_flags_t)(1 << 1),
/* set RQF_PREEMPT */
BLK_MQ_REQ_PREEMPT = (__force blk_mq_req_flags_t)(1 << 3),
struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
blk_mq_req_flags_t flags);
struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
unsigned int op, blk_mq_req_flags_t flags,
unsigned int hctx_idx);
struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag);
enum {
u32 blk_mq_unique_tag(struct request *rq);
static inline u16 blk_mq_unique_tag_to_hwq(u32 unique_tag)
return unique_tag >> BLK_MQ_UNIQUE_TAG_BITS;
static inline u16 blk_mq_unique_tag_to_tag(u32 unique_tag)
return unique_tag & BLK_MQ_UNIQUE_TAG_MASK;
* blk_mq_rq_state() - read the current MQ_RQ_* state of a request
* @rq: target request.
static inline enum mq_rq_state blk_mq_rq_state(struct request *rq)
return READ_ONCE(rq->state);
static inline int blk_mq_request_started(struct request *rq)
return blk_mq_rq_state(rq) != MQ_RQ_IDLE;
static inline int blk_mq_request_completed(struct request *rq)
return blk_mq_rq_state(rq) == MQ_RQ_COMPLETE;
void blk_mq_start_request(struct request *rq);
void blk_mq_end_request(struct request *rq, blk_status_t error);
void __blk_mq_end_request(struct request *rq, blk_status_t error);
void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list);
void blk_mq_kick_requeue_list(struct request_queue *q);
void blk_mq_delay_kick_requeue_list(struct request_queue *q, unsigned long msecs);
void blk_mq_complete_request(struct request *rq);
bool blk_mq_complete_request_remote(struct request *rq);
bool blk_mq_queue_stopped(struct request_queue *q);
void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx);
void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx);
void blk_mq_stop_hw_queues(struct request_queue *q);
void blk_mq_start_hw_queues(struct request_queue *q);
void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async);
void blk_mq_quiesce_queue(struct request_queue *q);
void blk_mq_unquiesce_queue(struct request_queue *q);
void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs);
void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
void blk_mq_run_hw_queues(struct request_queue *q, bool async);
void blk_mq_delay_run_hw_queues(struct request_queue *q, unsigned long msecs);
void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
busy_tag_iter_fn *fn, void *priv);
void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset);
void blk_mq_freeze_queue(struct request_queue *q);
void blk_mq_unfreeze_queue(struct request_queue *q);
void blk_freeze_queue_start(struct request_queue *q);
void blk_mq_freeze_queue_wait(struct request_queue *q);
int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
unsigned long timeout);
int blk_mq_map_queues(struct blk_mq_queue_map *qmap);
void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues);
void blk_mq_quiesce_queue_nowait(struct request_queue *q);
unsigned int blk_mq_rq_cpu(struct request *rq);
bool __blk_should_fake_timeout(struct request_queue *q);
static inline bool blk_should_fake_timeout(struct request_queue *q)
test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags))
return __blk_should_fake_timeout(q);
return false;
* blk_mq_rq_from_pdu - cast a PDU to a request
* @pdu: the PDU (Protocol Data Unit) to be casted
* Return: request
* Driver command data is immediately after the request. So subtract request
* size to get back to the original request.
static inline struct request *blk_mq_rq_from_pdu(void *pdu)
return pdu - sizeof(struct request);
* blk_mq_rq_to_pdu - cast a request to a PDU
* @rq: the request to be casted
* Return: pointer to the PDU
* Driver command data is immediately after the request. So add request to get
* the PDU.
static inline void *blk_mq_rq_to_pdu(struct request *rq)
return rq + 1;
#define queue_for_each_hw_ctx(q, hctx, i) \
for ((i) = 0; (i) < (q)->nr_hw_queues && \
({ hctx = (q)->queue_hw_ctx[i]; 1; }); (i)++)
#define hctx_for_each_ctx(hctx, ctx, i) \
for ((i) = 0; (i) < (hctx)->nr_ctx && \
({ ctx = (hctx)->ctxs[(i)]; 1; }); (i)++)
static inline blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx,
struct request *rq)
if (rq->tag != -1)
return rq->tag | (hctx->queue_num << BLK_QC_T_SHIFT);
return rq->internal_tag | (hctx->queue_num << BLK_QC_T_SHIFT) |
static inline void blk_mq_cleanup_rq(struct request *rq)
if (rq->q->mq_ops->cleanup_rq)
blk_qc_t blk_mq_submit_bio(struct bio *bio);