blk.h

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#ifndef BLK_INTERNAL_H
#define BLK_INTERNAL_H

#include <linux/idr.h>

/* Amount of time in which a process may batch requests */
#define BLK_BATCH_TIME  (HZ/50UL)

/* Number of requests a "batching" process may submit */
#define BLK_BATCH_REQ   32

extern struct kmem_cache *blk_requestq_cachep;
extern struct kobj_type blk_queue_ktype;
extern struct ida blk_queue_ida;

static inline void __blk_get_queue(struct request_queue *q)
{
    kobject_get(&q->kobj);
}

int blk_init_rl(struct request_list *rl, struct request_queue *q,
        gfp_t gfp_mask);
void blk_exit_rl(struct request_list *rl);
void init_request_from_bio(struct request *req, struct bio *bio);
void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
            struct bio *bio);
int blk_rq_append_bio(struct request_queue *q, struct request *rq,
              struct bio *bio);
void blk_queue_bypass_start(struct request_queue *q);
void blk_queue_bypass_end(struct request_queue *q);
void blk_dequeue_request(struct request *rq);
void __blk_queue_free_tags(struct request_queue *q);
bool __blk_end_bidi_request(struct request *rq, int error,
                unsigned int nr_bytes, unsigned int bidi_bytes);

void blk_rq_timed_out_timer(unsigned long data);
void blk_delete_timer(struct request *);
void blk_add_timer(struct request *);

/*
 * Internal atomic flags for request handling
 */
enum rq_atomic_flags {
    REQ_ATOM_COMPLETE = 0,
};

/*
 * EH timer and IO completion will both attempt to 'grab' the request, make
 * sure that only one of them succeeds
 */
static inline int blk_mark_rq_complete(struct request *rq)
{
    return test_and_set_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
}

static inline void blk_clear_rq_complete(struct request *rq)
{
    clear_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
}

/*
 * Internal elevator interface
 */
#define ELV_ON_HASH(rq)     (!hlist_unhashed(&(rq)->hash))

void blk_insert_flush(struct request *rq);
void blk_abort_flushes(struct request_queue *q);

static inline struct request *__elv_next_request(struct request_queue *q)
{
    struct request *rq;

    while (1) {
        if (!list_empty(&q->queue_head)) {
            rq = list_entry_rq(q->queue_head.next);
            return rq;
        }

        /*
         * Flush request is running and flush request isn't queueable
         * in the drive, we can hold the queue till flush request is
         * finished. Even we don't do this, driver can't dispatch next
         * requests and will requeue them. And this can improve
         * throughput too. For example, we have request flush1, write1,
         * flush 2. flush1 is dispatched, then queue is hold, write1
         * isn't inserted to queue. After flush1 is finished, flush2
         * will be dispatched. Since disk cache is already clean,
         * flush2 will be finished very soon, so looks like flush2 is
         * folded to flush1.
         * Since the queue is hold, a flag is set to indicate the queue
         * should be restarted later. Please see flush_end_io() for
         * details.
         */
        if (q->flush_pending_idx != q->flush_running_idx &&
                !queue_flush_queueable(q)) {
            q->flush_queue_delayed = 1;
            return NULL;
        }
        if (unlikely(blk_queue_dead(q)) ||
            !q->elevator->type->ops.elevator_dispatch_fn(q, 0))
            return NULL;
    }
}

static inline void elv_activate_rq(struct request_queue *q, struct request *rq)
{
    struct elevator_queue *e = q->elevator;

    if (e->type->ops.elevator_activate_req_fn)
        e->type->ops.elevator_activate_req_fn(q, rq);
}

static inline void elv_deactivate_rq(struct request_queue *q, struct request *rq)
{
    struct elevator_queue *e = q->elevator;

    if (e->type->ops.elevator_deactivate_req_fn)
        e->type->ops.elevator_deactivate_req_fn(q, rq);
}

#ifdef CONFIG_FAIL_IO_TIMEOUT
int blk_should_fake_timeout(struct request_queue *);
ssize_t part_timeout_show(struct device *, struct device_attribute *, char *);
ssize_t part_timeout_store(struct device *, struct device_attribute *,
                const char *, size_t);
#else
static inline int blk_should_fake_timeout(struct request_queue *q)
{
    return 0;
}
#endif

int ll_back_merge_fn(struct request_queue *q, struct request *req,
             struct bio *bio);
int ll_front_merge_fn(struct request_queue *q, struct request *req, 
              struct bio *bio);
int attempt_back_merge(struct request_queue *q, struct request *rq);
int attempt_front_merge(struct request_queue *q, struct request *rq);
int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
                struct request *next);
void blk_recalc_rq_segments(struct request *rq);
void blk_rq_set_mixed_merge(struct request *rq);
bool blk_rq_merge_ok(struct request *rq, struct bio *bio);
int blk_try_merge(struct request *rq, struct bio *bio);

void blk_queue_congestion_threshold(struct request_queue *q);

int blk_dev_init(void);


/*
 * Return the threshold (number of used requests) at which the queue is
 * considered to be congested.  It include a little hysteresis to keep the
 * context switch rate down.
 */
static inline int queue_congestion_on_threshold(struct request_queue *q)
{
    return q->nr_congestion_on;
}

/*
 * The threshold at which a queue is considered to be uncongested
 */
static inline int queue_congestion_off_threshold(struct request_queue *q)
{
    return q->nr_congestion_off;
}

/*
 * Contribute to IO statistics IFF:
 *
 *  a) it's attached to a gendisk, and
 *  b) the queue had IO stats enabled when this request was started, and
 *  c) it's a file system request
 */
static inline int blk_do_io_stat(struct request *rq)
{
    return rq->rq_disk &&
           (rq->cmd_flags & REQ_IO_STAT) &&
        (rq->cmd_type == REQ_TYPE_FS);
}

/*
 * Internal io_context interface
 */
void get_io_context(struct io_context *ioc);
struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q);
struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q,
                 gfp_t gfp_mask);
void ioc_clear_queue(struct request_queue *q);

int create_task_io_context(struct task_struct *task, gfp_t gfp_mask, int node);

static inline struct io_context *create_io_context(gfp_t gfp_mask, int node)
{
    WARN_ON_ONCE(irqs_disabled());
    if (unlikely(!current->io_context))
        create_task_io_context(current, gfp_mask, node);
    return current->io_context;
}

/*
 * Internal throttling interface
 */
#ifdef CONFIG_BLK_DEV_THROTTLING
extern bool blk_throtl_bio(struct request_queue *q, struct bio *bio);
extern void blk_throtl_drain(struct request_queue *q);
extern int blk_throtl_init(struct request_queue *q);
extern void blk_throtl_exit(struct request_queue *q);
#else /* CONFIG_BLK_DEV_THROTTLING */
static inline bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
{
    return false;
}
static inline void blk_throtl_drain(struct request_queue *q) { }
static inline int blk_throtl_init(struct request_queue *q) { return 0; }
static inline void blk_throtl_exit(struct request_queue *q) { }
#endif /* CONFIG_BLK_DEV_THROTTLING */

#endif /* BLK_INTERNAL_H */