From: Jens Axboe An updated revision of the dynamic request allocation patch. Changes since last version: - Updated to latest 2.5-BK - unplug race fix, courtesy of Nick. get_request() also looks nicer now. drivers/block/deadline-iosched.c | 105 +++++++------ drivers/block/elevator.c | 19 ++ drivers/block/ll_rw_blk.c | 308 ++++++++++++++------------------------- include/linux/blkdev.h | 12 - include/linux/elevator.h | 7 5 files changed, 208 insertions(+), 243 deletions(-) diff -puN drivers/block/deadline-iosched.c~rq-dyn-works drivers/block/deadline-iosched.c --- 25/drivers/block/deadline-iosched.c~rq-dyn-works 2003-05-05 19:04:39.000000000 -0700 +++ 25-akpm/drivers/block/deadline-iosched.c 2003-05-05 19:04:39.000000000 -0700 @@ -28,7 +28,7 @@ static int writes_starved = 2; /* max static int fifo_batch = 16; /* # of sequential requests treated as one by the above parameters. For throughput. */ -static const int deadline_hash_shift = 10; +static const int deadline_hash_shift = 5; #define DL_HASH_BLOCK(sec) ((sec) >> 3) #define DL_HASH_FN(sec) (hash_long(DL_HASH_BLOCK((sec)), deadline_hash_shift)) #define DL_HASH_ENTRIES (1 << deadline_hash_shift) @@ -71,6 +71,8 @@ struct deadline_data { int fifo_batch; int writes_starved; int front_merges; + + mempool_t *drq_pool; }; /* @@ -130,6 +132,21 @@ deadline_add_drq_hash(struct deadline_da list_add(&drq->hash, &dd->hash[DL_HASH_FN(rq_hash_key(rq))]); } +/* + * move hot entry to front of chain + */ +static inline void +deadline_hot_drq_hash(struct deadline_data *dd, struct deadline_rq *drq) +{ + struct request *rq = drq->request; + struct list_head *head = &dd->hash[DL_HASH_FN(rq_hash_key(rq))]; + + if (ON_HASH(drq) && drq->hash.prev != head) { + list_del(&drq->hash); + list_add(&drq->hash, head); + } +} + static struct request * deadline_find_drq_hash(struct deadline_data *dd, sector_t offset) { @@ -353,6 +370,8 @@ deadline_merge(request_queue_t *q, struc out: q->last_merge = &__rq->queuelist; out_insert: + if (ret) + deadline_hot_drq_hash(dd, RQ_DATA(__rq)); *insert = &__rq->queuelist; return ret; } @@ -673,28 +692,11 @@ deadline_latter_request(request_queue_t static void deadline_exit(request_queue_t *q, elevator_t *e) { struct deadline_data *dd = e->elevator_data; - struct deadline_rq *drq; - struct request *rq; - int i; BUG_ON(!list_empty(&dd->fifo_list[READ])); BUG_ON(!list_empty(&dd->fifo_list[WRITE])); - for (i = READ; i <= WRITE; i++) { - struct request_list *rl = &q->rq[i]; - struct list_head *entry; - - list_for_each(entry, &rl->free) { - rq = list_entry_rq(entry); - - if ((drq = RQ_DATA(rq)) == NULL) - continue; - - rq->elevator_private = NULL; - kmem_cache_free(drq_pool, drq); - } - } - + mempool_destroy(dd->drq_pool); kfree(dd->hash); kfree(dd); } @@ -706,9 +708,7 @@ static void deadline_exit(request_queue_ static int deadline_init(request_queue_t *q, elevator_t *e) { struct deadline_data *dd; - struct deadline_rq *drq; - struct request *rq; - int i, ret = 0; + int i; if (!drq_pool) return -ENOMEM; @@ -724,6 +724,13 @@ static int deadline_init(request_queue_t return -ENOMEM; } + dd->drq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, drq_pool); + if (!dd->drq_pool) { + kfree(dd->hash); + kfree(dd); + return -ENOMEM; + } + for (i = 0; i < DL_HASH_ENTRIES; i++) INIT_LIST_HEAD(&dd->hash[i]); @@ -739,33 +746,41 @@ static int deadline_init(request_queue_t dd->front_merges = 1; dd->fifo_batch = fifo_batch; e->elevator_data = dd; + return 0; +} - for (i = READ; i <= WRITE; i++) { - struct request_list *rl = &q->rq[i]; - struct list_head *entry; - - list_for_each(entry, &rl->free) { - rq = list_entry_rq(entry); - - drq = kmem_cache_alloc(drq_pool, GFP_KERNEL); - if (!drq) { - ret = -ENOMEM; - break; - } +static void deadline_put_request(request_queue_t *q, struct request *rq) +{ + struct deadline_data *dd = q->elevator.elevator_data; + struct deadline_rq *drq = RQ_DATA(rq); - memset(drq, 0, sizeof(*drq)); - INIT_LIST_HEAD(&drq->fifo); - INIT_LIST_HEAD(&drq->hash); - RB_CLEAR(&drq->rb_node); - drq->request = rq; - rq->elevator_private = drq; - } + if (drq) { + mempool_free(drq, dd->drq_pool); + rq->elevator_private = NULL; } +} - if (ret) - deadline_exit(q, e); +static int +deadline_set_request(request_queue_t *q, struct request *rq, int gfp_mask) +{ + struct deadline_data *dd = q->elevator.elevator_data; + struct deadline_rq *drq; - return ret; + drq = mempool_alloc(dd->drq_pool, gfp_mask); + if (drq) { + RB_CLEAR(&drq->rb_node); + drq->request = rq; + + INIT_LIST_HEAD(&drq->hash); + drq->hash_valid_count = 0; + + INIT_LIST_HEAD(&drq->fifo); + + rq->elevator_private = drq; + return 0; + } + + return 1; } /* @@ -916,6 +931,8 @@ elevator_t iosched_deadline = { .elevator_queue_empty_fn = deadline_queue_empty, .elevator_former_req_fn = deadline_former_request, .elevator_latter_req_fn = deadline_latter_request, + .elevator_set_req_fn = deadline_set_request, + .elevator_put_req_fn = deadline_put_request, .elevator_init_fn = deadline_init, .elevator_exit_fn = deadline_exit, diff -puN drivers/block/elevator.c~rq-dyn-works drivers/block/elevator.c --- 25/drivers/block/elevator.c~rq-dyn-works 2003-05-05 19:04:39.000000000 -0700 +++ 25-akpm/drivers/block/elevator.c 2003-05-05 19:04:39.000000000 -0700 @@ -408,6 +408,25 @@ struct request *elv_former_request(reque return NULL; } +int elv_set_request(request_queue_t *q, struct request *rq, int gfp_mask) +{ + elevator_t *e = &q->elevator; + + if (e->elevator_set_req_fn) + return e->elevator_set_req_fn(q, rq, gfp_mask); + + rq->elevator_private = NULL; + return 0; +} + +void elv_put_request(request_queue_t *q, struct request *rq) +{ + elevator_t *e = &q->elevator; + + if (e->elevator_put_req_fn) + e->elevator_put_req_fn(q, rq); +} + int elv_register_queue(struct gendisk *disk) { request_queue_t *q = disk->queue; diff -puN drivers/block/ll_rw_blk.c~rq-dyn-works drivers/block/ll_rw_blk.c --- 25/drivers/block/ll_rw_blk.c~rq-dyn-works 2003-05-05 19:04:39.000000000 -0700 +++ 25-akpm/drivers/block/ll_rw_blk.c 2003-05-05 19:04:40.000000000 -0700 @@ -48,12 +48,6 @@ static spinlock_t blk_plug_lock __cachel */ static int queue_nr_requests; -/* - * How many free requests must be available before we wake a process which - * is waiting for a request? - */ -static int batch_requests; - unsigned long blk_max_low_pfn, blk_max_pfn; int blk_nohighio = 0; @@ -419,7 +413,7 @@ struct request *blk_queue_find_tag(reque { struct blk_queue_tag *bqt = q->queue_tags; - if(unlikely(bqt == NULL || bqt->max_depth < tag)) + if (unlikely(bqt == NULL || bqt->max_depth < tag)) return NULL; return bqt->tag_index[tag]; @@ -1122,26 +1116,6 @@ out: spin_unlock_irq(&blk_plug_lock); } -static int __blk_cleanup_queue(struct request_list *list) -{ - struct list_head *head = &list->free; - struct request *rq; - int i = 0; - - while (!list_empty(head)) { - rq = list_entry(head->next, struct request, queuelist); - list_del_init(&rq->queuelist); - kmem_cache_free(request_cachep, rq); - i++; - } - - if (i != list->count) - printk("request list leak!\n"); - - list->count = 0; - return i; -} - /** * blk_cleanup_queue: - release a &request_queue_t when it is no longer needed * @q: the request queue to be released @@ -1158,18 +1132,14 @@ static int __blk_cleanup_queue(struct re **/ void blk_cleanup_queue(request_queue_t * q) { - int count = (queue_nr_requests*2); + struct request_list *rl = &q->rq; elevator_exit(q); - count -= __blk_cleanup_queue(&q->rq[READ]); - count -= __blk_cleanup_queue(&q->rq[WRITE]); - del_timer_sync(&q->unplug_timer); flush_scheduled_work(); - if (count) - printk("blk_cleanup_queue: leaked requests (%d)\n", count); + mempool_destroy(rl->rq_pool); if (blk_queue_tagged(q)) blk_queue_free_tags(q); @@ -1179,42 +1149,17 @@ void blk_cleanup_queue(request_queue_t * static int blk_init_free_list(request_queue_t *q) { - struct request_list *rl; - struct request *rq; - int i; + struct request_list *rl = &q->rq; - INIT_LIST_HEAD(&q->rq[READ].free); - INIT_LIST_HEAD(&q->rq[WRITE].free); - q->rq[READ].count = 0; - q->rq[WRITE].count = 0; + rl->count[READ] = BLKDEV_MAX_RQ; + rl->count[WRITE] = BLKDEV_MAX_RQ; - /* - * Divide requests in half between read and write - */ - rl = &q->rq[READ]; - for (i = 0; i < (queue_nr_requests*2); i++) { - rq = kmem_cache_alloc(request_cachep, SLAB_KERNEL); - if (!rq) - goto nomem; + rl->rq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, request_cachep); - /* - * half way through, switch to WRITE list - */ - if (i == queue_nr_requests) - rl = &q->rq[WRITE]; - - memset(rq, 0, sizeof(struct request)); - rq->rq_status = RQ_INACTIVE; - list_add(&rq->queuelist, &rl->free); - rl->count++; - } + if (!rl->rq_pool) + return -ENOMEM; - init_waitqueue_head(&q->rq[READ].wait); - init_waitqueue_head(&q->rq[WRITE].wait); return 0; -nomem: - blk_cleanup_queue(q); - return 1; } static int __make_request(request_queue_t *, struct bio *); @@ -1276,41 +1221,80 @@ int blk_init_queue(request_queue_t *q, r blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS); blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS); - INIT_LIST_HEAD(&q->plug_list); - return 0; } +static inline void blk_free_request(request_queue_t *q, struct request *rq) +{ + elv_put_request(q, rq); + mempool_free(rq, q->rq.rq_pool); +} + +static inline struct request *blk_alloc_request(request_queue_t *q,int gfp_mask) +{ + struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask); + + if (!rq) + return NULL; + + if (!elv_set_request(q, rq, gfp_mask)) + return rq; + + mempool_free(rq, q->rq.rq_pool); + return NULL; +} + #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist) /* - * Get a free request. queue lock must be held and interrupts - * disabled on the way in. + * Get a free request, queue_lock must not be held */ -static struct request *get_request(request_queue_t *q, int rw) +static struct request *get_request(request_queue_t *q, int rw, int gfp_mask) { struct request *rq = NULL; - struct request_list *rl = q->rq + rw; + struct request_list *rl = &q->rq; - if (!list_empty(&rl->free)) { - rq = blkdev_free_rq(&rl->free); - list_del_init(&rq->queuelist); - rq->ref_count = 1; - rl->count--; - if (rl->count < queue_congestion_on_threshold()) - set_queue_congested(q, rw); - rq->flags = 0; - rq->rq_status = RQ_ACTIVE; - rq->errors = 0; - rq->special = NULL; - rq->buffer = NULL; - rq->data = NULL; - rq->sense = NULL; - rq->waiting = NULL; - rq->bio = rq->biotail = NULL; - rq->q = q; - rq->rl = rl; + spin_lock_irq(q->queue_lock); + BUG_ON(rl->count[rw] < 0); + if (rl->count[rw] == 0) { + spin_unlock_irq(q->queue_lock); + goto out; } + rl->count[rw]--; + if (rl->count[rw] < queue_congestion_on_threshold()) + set_queue_congested(q, rw); + spin_unlock_irq(q->queue_lock); + rq = blk_alloc_request(q, gfp_mask); + if (!rq) { + spin_lock_irq(q->queue_lock); + rl->count[rw]++; + if (rl->count[rw] >= queue_congestion_off_threshold()) + clear_queue_congested(q, rw); + spin_unlock_irq(q->queue_lock); + goto out; + } + + INIT_LIST_HEAD(&rq->queuelist); + + /* + * first three bits are identical in rq->flags and bio->bi_rw, + * see bio.h and blkdev.h + */ + rq->flags = rw; + + rq->errors = 0; + rq->rq_status = RQ_ACTIVE; + rq->bio = rq->biotail = NULL; + rq->buffer = NULL; + rq->ref_count = 1; + rq->q = q; + rq->rl = rl; + rq->waiting = NULL; + rq->special = NULL; + rq->data = NULL; + rq->sense = NULL; + +out: return rq; } @@ -1319,31 +1303,16 @@ static struct request *get_request(reque */ static struct request *get_request_wait(request_queue_t *q, int rw) { - DEFINE_WAIT(wait); - struct request_list *rl = &q->rq[rw]; struct request *rq; - spin_lock_prefetch(q->queue_lock); - generic_unplug_device(q); do { - int block = 0; + rq = get_request(q, rw, GFP_NOIO); - prepare_to_wait_exclusive(&rl->wait, &wait, - TASK_UNINTERRUPTIBLE); - spin_lock_irq(q->queue_lock); - if (!rl->count) - block = 1; - spin_unlock_irq(q->queue_lock); - - if (block) - io_schedule(); - finish_wait(&rl->wait, &wait); + if (!rq) + blk_congestion_wait(rw, HZ / 50); + } while (!rq); - spin_lock_irq(q->queue_lock); - rq = get_request(q, rw); - spin_unlock_irq(q->queue_lock); - } while (rq == NULL); return rq; } @@ -1353,39 +1322,11 @@ struct request *blk_get_request(request_ BUG_ON(rw != READ && rw != WRITE); - spin_lock_irq(q->queue_lock); - rq = get_request(q, rw); - spin_unlock_irq(q->queue_lock); + rq = get_request(q, rw, gfp_mask); if (!rq && (gfp_mask & __GFP_WAIT)) rq = get_request_wait(q, rw); - if (rq) { - rq->flags = 0; - rq->buffer = NULL; - rq->bio = rq->biotail = NULL; - rq->waiting = NULL; - } - return rq; -} - -/* - * Non-locking blk_get_request variant, for special requests from drivers. - */ -struct request *__blk_get_request(request_queue_t *q, int rw) -{ - struct request *rq; - - BUG_ON(rw != READ && rw != WRITE); - - rq = get_request(q, rw); - - if (rq) { - rq->flags = 0; - rq->buffer = NULL; - rq->bio = rq->biotail = NULL; - rq->waiting = NULL; - } return rq; } @@ -1503,14 +1444,17 @@ void disk_round_stats(struct gendisk *di disk->stamp_idle = now; } +/* + * queue lock must be held + */ void __blk_put_request(request_queue_t *q, struct request *req) { struct request_list *rl = req->rl; - if (unlikely(--req->ref_count)) - return; if (unlikely(!q)) return; + if (unlikely(--req->ref_count)) + return; req->rq_status = RQ_INACTIVE; req->q = NULL; @@ -1521,24 +1465,15 @@ void __blk_put_request(request_queue_t * * it didn't come out of our reserved rq pools */ if (rl) { - int rw = 0; + int rw = rq_data_dir(req); BUG_ON(!list_empty(&req->queuelist)); - list_add(&req->queuelist, &rl->free); + blk_free_request(q, req); - if (rl == &q->rq[WRITE]) - rw = WRITE; - else if (rl == &q->rq[READ]) - rw = READ; - else - BUG(); - - rl->count++; - if (rl->count >= queue_congestion_off_threshold()) + rl->count[rw]++; + if (rl->count[rw] >= queue_congestion_off_threshold()) clear_queue_congested(q, rw); - if (rl->count >= batch_requests && waitqueue_active(&rl->wait)) - wake_up(&rl->wait); } } @@ -1605,24 +1540,23 @@ static int attempt_merge(request_queue_t * will have updated segment counts, update sector * counts here. */ - if (q->merge_requests_fn(q, req, next)) { - req->biotail->bi_next = next->bio; - req->biotail = next->biotail; + if (!q->merge_requests_fn(q, req, next)) + return 0; - req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors; + req->biotail->bi_next = next->bio; + req->biotail = next->biotail; - elv_merge_requests(q, req, next); + req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors; - if (req->rq_disk) { - disk_round_stats(req->rq_disk); - disk_stat_dec(req->rq_disk, in_flight); - } + elv_merge_requests(q, req, next); - __blk_put_request(q, next); - return 1; + if (req->rq_disk) { + disk_round_stats(req->rq_disk); + disk_stat_dec(req->rq_disk, in_flight); } - return 0; + __blk_put_request(q, next); + return 1; } static inline int attempt_back_merge(request_queue_t *q, struct request *rq) @@ -1698,9 +1632,9 @@ static int __make_request(request_queue_ barrier = test_bit(BIO_RW_BARRIER, &bio->bi_rw); - spin_lock_irq(q->queue_lock); again: insert_here = NULL; + spin_lock_irq(q->queue_lock); if (elv_queue_empty(q)) { blk_plug_device(q); @@ -1776,17 +1710,17 @@ get_rq: if (freereq) { req = freereq; freereq = NULL; - } else if ((req = get_request(q, rw)) == NULL) { + } else { spin_unlock_irq(q->queue_lock); - - /* - * READA bit set - */ - if (bio_flagged(bio, BIO_RW_AHEAD)) - goto end_io; - - freereq = get_request_wait(q, rw); - spin_lock_irq(q->queue_lock); + if ((freereq = get_request(q, rw, GFP_ATOMIC)) == NULL) { + /* + * READA bit set + */ + if (bio_flagged(bio, BIO_RW_AHEAD)) + goto end_io; + + freereq = get_request_wait(q, rw); + } goto again; } @@ -1813,14 +1747,15 @@ get_rq: req->bio = req->biotail = bio; req->rq_disk = bio->bi_bdev->bd_disk; req->start_time = jiffies; + add_request(q, req, insert_here); out: if (freereq) __blk_put_request(q, freereq); if (blk_queue_plugged(q)) { - int nr_queued = (queue_nr_requests - q->rq[0].count) + - (queue_nr_requests - q->rq[1].count); + int nr_queued = (queue_nr_requests - q->rq.count[0]) + + (queue_nr_requests - q->rq.count[1]); if (nr_queued == q->unplug_thresh) __generic_unplug_device(q); } @@ -2213,7 +2148,6 @@ void blk_rq_bio_prep(request_queue_t *q, int __init blk_dev_init(void) { - int total_ram = nr_free_pages() << (PAGE_SHIFT - 10); int i; request_cachep = kmem_cache_create("blkdev_requests", @@ -2221,24 +2155,11 @@ int __init blk_dev_init(void) if (!request_cachep) panic("Can't create request pool slab cache\n"); - /* - * Free request slots per queue. One per quarter-megabyte. - * We use this many requests for reads, and this many for writes. - */ - queue_nr_requests = (total_ram >> 9) & ~7; - if (queue_nr_requests < 16) - queue_nr_requests = 16; - if (queue_nr_requests > 128) - queue_nr_requests = 128; - - batch_requests = queue_nr_requests / 8; - if (batch_requests > 8) - batch_requests = 8; + queue_nr_requests = BLKDEV_MAX_RQ; printk("block request queues:\n"); - printk(" %d requests per read queue\n", queue_nr_requests); - printk(" %d requests per write queue\n", queue_nr_requests); - printk(" %d requests per batch\n", batch_requests); + printk(" %d/%d requests per read queue\n", BLKDEV_MIN_RQ, queue_nr_requests); + printk(" %d/%d requests per write queue\n", BLKDEV_MIN_RQ, queue_nr_requests); printk(" enter congestion at %d\n", queue_congestion_on_threshold()); printk(" exit congestion at %d\n", queue_congestion_off_threshold()); @@ -2281,7 +2202,6 @@ EXPORT_SYMBOL(blk_queue_assign_lock); EXPORT_SYMBOL(blk_phys_contig_segment); EXPORT_SYMBOL(blk_hw_contig_segment); EXPORT_SYMBOL(blk_get_request); -EXPORT_SYMBOL(__blk_get_request); EXPORT_SYMBOL(blk_put_request); EXPORT_SYMBOL(blk_insert_request); diff -puN include/linux/blkdev.h~rq-dyn-works include/linux/blkdev.h --- 25/include/linux/blkdev.h~rq-dyn-works 2003-05-05 19:04:39.000000000 -0700 +++ 25-akpm/include/linux/blkdev.h 2003-05-05 19:04:40.000000000 -0700 @@ -10,6 +10,7 @@ #include #include #include +#include #include @@ -18,10 +19,12 @@ typedef struct request_queue request_que struct elevator_s; typedef struct elevator_s elevator_t; +#define BLKDEV_MIN_RQ 4 +#define BLKDEV_MAX_RQ 1024 + struct request_list { - unsigned int count; - struct list_head free; - wait_queue_head_t wait; + int count[2]; + mempool_t *rq_pool; }; /* @@ -180,7 +183,7 @@ struct request_queue /* * the queue request freelist, one for reads and one for writes */ - struct request_list rq[2]; + struct request_list rq; request_fn_proc *request_fn; merge_request_fn *back_merge_fn; @@ -329,7 +332,6 @@ extern void blk_put_request(struct reque extern void blk_attempt_remerge(request_queue_t *, struct request *); extern void __blk_attempt_remerge(request_queue_t *, struct request *); extern struct request *blk_get_request(request_queue_t *, int, int); -extern struct request *__blk_get_request(request_queue_t *, int); extern void blk_put_request(struct request *); extern void blk_insert_request(request_queue_t *, struct request *, int, void *); extern void blk_plug_device(request_queue_t *); diff -puN include/linux/elevator.h~rq-dyn-works include/linux/elevator.h --- 25/include/linux/elevator.h~rq-dyn-works 2003-05-05 19:04:39.000000000 -0700 +++ 25-akpm/include/linux/elevator.h 2003-05-05 19:04:40.000000000 -0700 @@ -15,6 +15,8 @@ typedef int (elevator_queue_empty_fn) (r typedef void (elevator_remove_req_fn) (request_queue_t *, struct request *); typedef struct request *(elevator_request_list_fn) (request_queue_t *, struct request *); typedef struct list_head *(elevator_get_sort_head_fn) (request_queue_t *, struct request *); +typedef int (elevator_set_req_fn) (request_queue_t *, struct request *, int); +typedef void (elevator_put_req_fn) (request_queue_t *, struct request *); typedef int (elevator_init_fn) (request_queue_t *, elevator_t *); typedef void (elevator_exit_fn) (request_queue_t *, elevator_t *); @@ -34,6 +36,9 @@ struct elevator_s elevator_request_list_fn *elevator_former_req_fn; elevator_request_list_fn *elevator_latter_req_fn; + elevator_set_req_fn *elevator_set_req_fn; + elevator_put_req_fn *elevator_put_req_fn; + elevator_init_fn *elevator_init_fn; elevator_exit_fn *elevator_exit_fn; @@ -59,6 +64,8 @@ extern struct request *elv_former_reques extern struct request *elv_latter_request(request_queue_t *, struct request *); extern int elv_register_queue(struct gendisk *); extern void elv_unregister_queue(struct gendisk *); +extern int elv_set_request(request_queue_t *, struct request *, int); +extern void elv_put_request(request_queue_t *, struct request *); #define __elv_add_request_pos(q, rq, pos) \ (q)->elevator.elevator_add_req_fn((q), (rq), (pos)) _