struct blk_flush_queue;
/**
- * struct blk_mq_hw_ctx - State for a hardware queue facing the hardware block device
+ * 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;
- unsigned long state; /* BLK_MQ_S_* flags */
+ /**
+ * @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;
- unsigned long flags; /* BLK_MQ_F_* flags */
+ /** @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;
#define BLK_MQ_MAX_DISPATCH_ORDER 7
+ /** @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;
+ /** @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;
#ifdef CONFIG_BLK_DEBUG_FS
+ /**
+ * @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;
#endif
+ /** @hctx_list: List of all hardware queues. */
struct list_head hctx_list;
- /* Must be the last member - see also blk_mq_hw_ctx_size(). */
+ /**
+ * @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[0];
};
/**
- * struct blk_mq_queue_map - ctx -> hctx mapping
+ * 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).
unsigned int queue_offset;
};
+/**
+ * enum hctx_type - Type of hardware queue
+ * @HCTX_TYPE_DEFAULT: All I/O not otherwise accounted for.
+ * @HCTX_TYPE_READ: Just for READ I/O.
+ * @HCTX_TYPE_POLL: Polled I/O of any kind.
+ * @HCTX_MAX_TYPES: Number of types of hctx.
+ */
enum hctx_type {
- HCTX_TYPE_DEFAULT, /* all I/O not otherwise accounted for */
- HCTX_TYPE_READ, /* just for READ I/O */
- HCTX_TYPE_POLL, /* polled I/O of any kind */
+ HCTX_TYPE_DEFAULT,
+ HCTX_TYPE_READ,
+ HCTX_TYPE_POLL,
HCTX_MAX_TYPES,
};
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 void (complete_fn)(struct request *);
typedef void (cleanup_rq_fn)(struct request *);
-
+/**
+ * struct blk_mq_ops - Callback functions that implements block driver
+ * behaviour.
+ */
struct blk_mq_ops {
- /*
- * Queue request
+ /**
+ * @queue_rq: Queue a new request from block IO.
*/
queue_rq_fn *queue_rq;
- /*
- * 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
+ /**
+ * @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).
*/
commit_rqs_fn *commit_rqs;
- /*
- * Reserve budget before queue request, once .queue_rq is
+ /**
+ * @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.
*/
get_budget_fn *get_budget;
+ /**
+ * @put_budget: Release the reserved budget.
+ */
put_budget_fn *put_budget;
- /*
- * Called on request timeout
+ /**
+ * @timeout: Called on request timeout.
*/
timeout_fn *timeout;
- /*
- * Called to poll for completion of a specific tag.
+ /**
+ * @poll: Called to poll for completion of a specific tag.
*/
poll_fn *poll;
+ /**
+ * @complete: Mark the request as complete.
+ */
complete_fn *complete;
- /*
- * Called when the block layer side of a hardware queue has been
- * set up, allowing the driver to allocate/init matching structures.
- * Ditto for exit/teardown.
+ /**
+ * @init_hctx: Called when the block layer side of a hardware queue has
+ * been set up, allowing the driver to allocate/init matching
+ * structures.
*/
init_hctx_fn *init_hctx;
+ /**
+ * @exit_hctx: Ditto for exit/teardown.
+ */
exit_hctx_fn *exit_hctx;
- /*
- * Called for every command allocated by the block layer to allow
- * the driver to set up driver specific data.
+ /**
+ * @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.
- *
- * Ditto for exit/teardown.
*/
init_request_fn *init_request;
+ /**
+ * @exit_request: Ditto for exit/teardown.
+ */
exit_request_fn *exit_request;
- /* Called from inside blk_get_request() */
+
+ /**
+ * @initialize_rq_fn: Called from inside blk_get_request().
+ */
void (*initialize_rq_fn)(struct request *rq);
- /*
- * Called before freeing one request which isn't completed yet,
- * and usually for freeing the driver private data
+ /**
+ * @cleanup_rq: Called before freeing one request which isn't completed
+ * yet, and usually for freeing the driver private data.
*/
cleanup_rq_fn *cleanup_rq;
- /*
- * If set, returns whether or not this queue currently is busy
+ /**
+ * @busy: If set, returns whether or not this queue currently is busy.
*/
busy_fn *busy;
+ /**
+ * @map_queues: This allows drivers specify their own queue mapping by
+ * overriding the setup-time function that builds the mq_map.
+ */
map_queues_fn *map_queues;
#ifdef CONFIG_BLK_DEBUG_FS
- /*
- * Used by the debugfs implementation to show driver-specific
+ /**
+ * @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);
unsigned int blk_mq_rq_cpu(struct request *rq);
-/*
+/**
+ * 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, add request size to get the PDU.
+ * 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;
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