| /* |
| * linux/drivers/block/elevator.c |
| * |
| * Block device elevator/IO-scheduler. |
| * |
| * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE |
| * |
| * 30042000 Jens Axboe <axboe@suse.de> : |
| * |
| * Split the elevator a bit so that it is possible to choose a different |
| * one or even write a new "plug in". There are three pieces: |
| * - elevator_fn, inserts a new request in the queue list |
| * - elevator_merge_fn, decides whether a new buffer can be merged with |
| * an existing request |
| * - elevator_dequeue_fn, called when a request is taken off the active list |
| * |
| * 20082000 Dave Jones <davej@suse.de> : |
| * Removed tests for max-bomb-segments, which was breaking elvtune |
| * when run without -bN |
| * |
| * Jens: |
| * - Rework again to work with bio instead of buffer_heads |
| * - loose bi_dev comparisons, partition handling is right now |
| * - completely modularize elevator setup and teardown |
| * |
| */ |
| #include <linux/kernel.h> |
| #include <linux/fs.h> |
| #include <linux/blkdev.h> |
| #include <linux/elevator.h> |
| #include <linux/bio.h> |
| #include <linux/config.h> |
| #include <linux/module.h> |
| #include <linux/slab.h> |
| #include <linux/init.h> |
| #include <linux/compiler.h> |
| |
| #include <asm/uaccess.h> |
| |
| static DEFINE_SPINLOCK(elv_list_lock); |
| static LIST_HEAD(elv_list); |
| |
| /* |
| * can we safely merge with this request? |
| */ |
| inline int elv_rq_merge_ok(struct request *rq, struct bio *bio) |
| { |
| if (!rq_mergeable(rq)) |
| return 0; |
| |
| /* |
| * different data direction or already started, don't merge |
| */ |
| if (bio_data_dir(bio) != rq_data_dir(rq)) |
| return 0; |
| |
| /* |
| * same device and no special stuff set, merge is ok |
| */ |
| if (rq->rq_disk == bio->bi_bdev->bd_disk && |
| !rq->waiting && !rq->special) |
| return 1; |
| |
| return 0; |
| } |
| EXPORT_SYMBOL(elv_rq_merge_ok); |
| |
| inline int elv_try_merge(struct request *__rq, struct bio *bio) |
| { |
| int ret = ELEVATOR_NO_MERGE; |
| |
| /* |
| * we can merge and sequence is ok, check if it's possible |
| */ |
| if (elv_rq_merge_ok(__rq, bio)) { |
| if (__rq->sector + __rq->nr_sectors == bio->bi_sector) |
| ret = ELEVATOR_BACK_MERGE; |
| else if (__rq->sector - bio_sectors(bio) == bio->bi_sector) |
| ret = ELEVATOR_FRONT_MERGE; |
| } |
| |
| return ret; |
| } |
| EXPORT_SYMBOL(elv_try_merge); |
| |
| inline int elv_try_last_merge(request_queue_t *q, struct bio *bio) |
| { |
| if (q->last_merge) |
| return elv_try_merge(q->last_merge, bio); |
| |
| return ELEVATOR_NO_MERGE; |
| } |
| EXPORT_SYMBOL(elv_try_last_merge); |
| |
| static struct elevator_type *elevator_find(const char *name) |
| { |
| struct elevator_type *e = NULL; |
| struct list_head *entry; |
| |
| spin_lock_irq(&elv_list_lock); |
| list_for_each(entry, &elv_list) { |
| struct elevator_type *__e; |
| |
| __e = list_entry(entry, struct elevator_type, list); |
| |
| if (!strcmp(__e->elevator_name, name)) { |
| e = __e; |
| break; |
| } |
| } |
| spin_unlock_irq(&elv_list_lock); |
| |
| return e; |
| } |
| |
| static void elevator_put(struct elevator_type *e) |
| { |
| module_put(e->elevator_owner); |
| } |
| |
| static struct elevator_type *elevator_get(const char *name) |
| { |
| struct elevator_type *e = elevator_find(name); |
| |
| if (!e) |
| return NULL; |
| if (!try_module_get(e->elevator_owner)) |
| return NULL; |
| |
| return e; |
| } |
| |
| static int elevator_attach(request_queue_t *q, struct elevator_type *e, |
| struct elevator_queue *eq) |
| { |
| int ret = 0; |
| |
| memset(eq, 0, sizeof(*eq)); |
| eq->ops = &e->ops; |
| eq->elevator_type = e; |
| |
| INIT_LIST_HEAD(&q->queue_head); |
| q->last_merge = NULL; |
| q->elevator = eq; |
| |
| if (eq->ops->elevator_init_fn) |
| ret = eq->ops->elevator_init_fn(q, eq); |
| |
| return ret; |
| } |
| |
| static char chosen_elevator[16]; |
| |
| static void elevator_setup_default(void) |
| { |
| /* |
| * check if default is set and exists |
| */ |
| if (chosen_elevator[0] && elevator_find(chosen_elevator)) |
| return; |
| |
| #if defined(CONFIG_IOSCHED_AS) |
| strcpy(chosen_elevator, "anticipatory"); |
| #elif defined(CONFIG_IOSCHED_DEADLINE) |
| strcpy(chosen_elevator, "deadline"); |
| #elif defined(CONFIG_IOSCHED_CFQ) |
| strcpy(chosen_elevator, "cfq"); |
| #elif defined(CONFIG_IOSCHED_NOOP) |
| strcpy(chosen_elevator, "noop"); |
| #else |
| #error "You must build at least 1 IO scheduler into the kernel" |
| #endif |
| } |
| |
| static int __init elevator_setup(char *str) |
| { |
| strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1); |
| return 0; |
| } |
| |
| __setup("elevator=", elevator_setup); |
| |
| int elevator_init(request_queue_t *q, char *name) |
| { |
| struct elevator_type *e = NULL; |
| struct elevator_queue *eq; |
| int ret = 0; |
| |
| elevator_setup_default(); |
| |
| if (!name) |
| name = chosen_elevator; |
| |
| e = elevator_get(name); |
| if (!e) |
| return -EINVAL; |
| |
| eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL); |
| if (!eq) { |
| elevator_put(e->elevator_type); |
| return -ENOMEM; |
| } |
| |
| ret = elevator_attach(q, e, eq); |
| if (ret) { |
| kfree(eq); |
| elevator_put(e->elevator_type); |
| } |
| |
| return ret; |
| } |
| |
| void elevator_exit(elevator_t *e) |
| { |
| if (e->ops->elevator_exit_fn) |
| e->ops->elevator_exit_fn(e); |
| |
| elevator_put(e->elevator_type); |
| e->elevator_type = NULL; |
| kfree(e); |
| } |
| |
| int elv_merge(request_queue_t *q, struct request **req, struct bio *bio) |
| { |
| elevator_t *e = q->elevator; |
| |
| if (e->ops->elevator_merge_fn) |
| return e->ops->elevator_merge_fn(q, req, bio); |
| |
| return ELEVATOR_NO_MERGE; |
| } |
| |
| void elv_merged_request(request_queue_t *q, struct request *rq) |
| { |
| elevator_t *e = q->elevator; |
| |
| if (e->ops->elevator_merged_fn) |
| e->ops->elevator_merged_fn(q, rq); |
| } |
| |
| void elv_merge_requests(request_queue_t *q, struct request *rq, |
| struct request *next) |
| { |
| elevator_t *e = q->elevator; |
| |
| if (q->last_merge == next) |
| q->last_merge = NULL; |
| |
| if (e->ops->elevator_merge_req_fn) |
| e->ops->elevator_merge_req_fn(q, rq, next); |
| } |
| |
| /* |
| * For careful internal use by the block layer. Essentially the same as |
| * a requeue in that it tells the io scheduler that this request is not |
| * active in the driver or hardware anymore, but we don't want the request |
| * added back to the scheduler. Function is not exported. |
| */ |
| void elv_deactivate_request(request_queue_t *q, struct request *rq) |
| { |
| elevator_t *e = q->elevator; |
| |
| /* |
| * it already went through dequeue, we need to decrement the |
| * in_flight count again |
| */ |
| if (blk_account_rq(rq)) |
| q->in_flight--; |
| |
| rq->flags &= ~REQ_STARTED; |
| |
| if (e->ops->elevator_deactivate_req_fn) |
| e->ops->elevator_deactivate_req_fn(q, rq); |
| } |
| |
| void elv_requeue_request(request_queue_t *q, struct request *rq) |
| { |
| elv_deactivate_request(q, rq); |
| |
| /* |
| * if this is the flush, requeue the original instead and drop the flush |
| */ |
| if (rq->flags & REQ_BAR_FLUSH) { |
| clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags); |
| rq = rq->end_io_data; |
| } |
| |
| /* |
| * the request is prepped and may have some resources allocated. |
| * allowing unprepped requests to pass this one may cause resource |
| * deadlock. turn on softbarrier. |
| */ |
| rq->flags |= REQ_SOFTBARRIER; |
| |
| /* |
| * if iosched has an explicit requeue hook, then use that. otherwise |
| * just put the request at the front of the queue |
| */ |
| if (q->elevator->ops->elevator_requeue_req_fn) |
| q->elevator->ops->elevator_requeue_req_fn(q, rq); |
| else |
| __elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0); |
| } |
| |
| void __elv_add_request(request_queue_t *q, struct request *rq, int where, |
| int plug) |
| { |
| /* |
| * barriers implicitly indicate back insertion |
| */ |
| if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER) && |
| where == ELEVATOR_INSERT_SORT) |
| where = ELEVATOR_INSERT_BACK; |
| |
| if (plug) |
| blk_plug_device(q); |
| |
| rq->q = q; |
| |
| if (!test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)) { |
| q->elevator->ops->elevator_add_req_fn(q, rq, where); |
| |
| if (blk_queue_plugged(q)) { |
| int nrq = q->rq.count[READ] + q->rq.count[WRITE] |
| - q->in_flight; |
| |
| if (nrq >= q->unplug_thresh) |
| __generic_unplug_device(q); |
| } |
| } else |
| /* |
| * if drain is set, store the request "locally". when the drain |
| * is finished, the requests will be handed ordered to the io |
| * scheduler |
| */ |
| list_add_tail(&rq->queuelist, &q->drain_list); |
| } |
| |
| void elv_add_request(request_queue_t *q, struct request *rq, int where, |
| int plug) |
| { |
| unsigned long flags; |
| |
| spin_lock_irqsave(q->queue_lock, flags); |
| __elv_add_request(q, rq, where, plug); |
| spin_unlock_irqrestore(q->queue_lock, flags); |
| } |
| |
| static inline struct request *__elv_next_request(request_queue_t *q) |
| { |
| struct request *rq = q->elevator->ops->elevator_next_req_fn(q); |
| |
| /* |
| * if this is a barrier write and the device has to issue a |
| * flush sequence to support it, check how far we are |
| */ |
| if (rq && blk_fs_request(rq) && blk_barrier_rq(rq)) { |
| BUG_ON(q->ordered == QUEUE_ORDERED_NONE); |
| |
| if (q->ordered == QUEUE_ORDERED_FLUSH && |
| !blk_barrier_preflush(rq)) |
| rq = blk_start_pre_flush(q, rq); |
| } |
| |
| return rq; |
| } |
| |
| struct request *elv_next_request(request_queue_t *q) |
| { |
| struct request *rq; |
| int ret; |
| |
| while ((rq = __elv_next_request(q)) != NULL) { |
| /* |
| * just mark as started even if we don't start it, a request |
| * that has been delayed should not be passed by new incoming |
| * requests |
| */ |
| rq->flags |= REQ_STARTED; |
| |
| if (rq == q->last_merge) |
| q->last_merge = NULL; |
| |
| if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn) |
| break; |
| |
| ret = q->prep_rq_fn(q, rq); |
| if (ret == BLKPREP_OK) { |
| break; |
| } else if (ret == BLKPREP_DEFER) { |
| /* |
| * the request may have been (partially) prepped. |
| * we need to keep this request in the front to |
| * avoid resource deadlock. turn on softbarrier. |
| */ |
| rq->flags |= REQ_SOFTBARRIER; |
| rq = NULL; |
| break; |
| } else if (ret == BLKPREP_KILL) { |
| int nr_bytes = rq->hard_nr_sectors << 9; |
| |
| if (!nr_bytes) |
| nr_bytes = rq->data_len; |
| |
| blkdev_dequeue_request(rq); |
| rq->flags |= REQ_QUIET; |
| end_that_request_chunk(rq, 0, nr_bytes); |
| end_that_request_last(rq); |
| } else { |
| printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__, |
| ret); |
| break; |
| } |
| } |
| |
| return rq; |
| } |
| |
| void elv_remove_request(request_queue_t *q, struct request *rq) |
| { |
| elevator_t *e = q->elevator; |
| |
| /* |
| * the time frame between a request being removed from the lists |
| * and to it is freed is accounted as io that is in progress at |
| * the driver side. note that we only account requests that the |
| * driver has seen (REQ_STARTED set), to avoid false accounting |
| * for request-request merges |
| */ |
| if (blk_account_rq(rq)) |
| q->in_flight++; |
| |
| /* |
| * the main clearing point for q->last_merge is on retrieval of |
| * request by driver (it calls elv_next_request()), but it _can_ |
| * also happen here if a request is added to the queue but later |
| * deleted without ever being given to driver (merged with another |
| * request). |
| */ |
| if (rq == q->last_merge) |
| q->last_merge = NULL; |
| |
| if (e->ops->elevator_remove_req_fn) |
| e->ops->elevator_remove_req_fn(q, rq); |
| } |
| |
| int elv_queue_empty(request_queue_t *q) |
| { |
| elevator_t *e = q->elevator; |
| |
| if (e->ops->elevator_queue_empty_fn) |
| return e->ops->elevator_queue_empty_fn(q); |
| |
| return list_empty(&q->queue_head); |
| } |
| |
| struct request *elv_latter_request(request_queue_t *q, struct request *rq) |
| { |
| struct list_head *next; |
| |
| elevator_t *e = q->elevator; |
| |
| if (e->ops->elevator_latter_req_fn) |
| return e->ops->elevator_latter_req_fn(q, rq); |
| |
| next = rq->queuelist.next; |
| if (next != &q->queue_head && next != &rq->queuelist) |
| return list_entry_rq(next); |
| |
| return NULL; |
| } |
| |
| struct request *elv_former_request(request_queue_t *q, struct request *rq) |
| { |
| struct list_head *prev; |
| |
| elevator_t *e = q->elevator; |
| |
| if (e->ops->elevator_former_req_fn) |
| return e->ops->elevator_former_req_fn(q, rq); |
| |
| prev = rq->queuelist.prev; |
| if (prev != &q->queue_head && prev != &rq->queuelist) |
| return list_entry_rq(prev); |
| |
| return NULL; |
| } |
| |
| int elv_set_request(request_queue_t *q, struct request *rq, struct bio *bio, |
| gfp_t gfp_mask) |
| { |
| elevator_t *e = q->elevator; |
| |
| if (e->ops->elevator_set_req_fn) |
| return e->ops->elevator_set_req_fn(q, rq, bio, 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->ops->elevator_put_req_fn) |
| e->ops->elevator_put_req_fn(q, rq); |
| } |
| |
| int elv_may_queue(request_queue_t *q, int rw, struct bio *bio) |
| { |
| elevator_t *e = q->elevator; |
| |
| if (e->ops->elevator_may_queue_fn) |
| return e->ops->elevator_may_queue_fn(q, rw, bio); |
| |
| return ELV_MQUEUE_MAY; |
| } |
| |
| void elv_completed_request(request_queue_t *q, struct request *rq) |
| { |
| elevator_t *e = q->elevator; |
| |
| /* |
| * request is released from the driver, io must be done |
| */ |
| if (blk_account_rq(rq)) |
| q->in_flight--; |
| |
| if (e->ops->elevator_completed_req_fn) |
| e->ops->elevator_completed_req_fn(q, rq); |
| } |
| |
| int elv_register_queue(struct request_queue *q) |
| { |
| elevator_t *e = q->elevator; |
| |
| e->kobj.parent = kobject_get(&q->kobj); |
| if (!e->kobj.parent) |
| return -EBUSY; |
| |
| snprintf(e->kobj.name, KOBJ_NAME_LEN, "%s", "iosched"); |
| e->kobj.ktype = e->elevator_type->elevator_ktype; |
| |
| return kobject_register(&e->kobj); |
| } |
| |
| void elv_unregister_queue(struct request_queue *q) |
| { |
| if (q) { |
| elevator_t *e = q->elevator; |
| kobject_unregister(&e->kobj); |
| kobject_put(&q->kobj); |
| } |
| } |
| |
| int elv_register(struct elevator_type *e) |
| { |
| if (elevator_find(e->elevator_name)) |
| BUG(); |
| |
| spin_lock_irq(&elv_list_lock); |
| list_add_tail(&e->list, &elv_list); |
| spin_unlock_irq(&elv_list_lock); |
| |
| printk(KERN_INFO "io scheduler %s registered", e->elevator_name); |
| if (!strcmp(e->elevator_name, chosen_elevator)) |
| printk(" (default)"); |
| printk("\n"); |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(elv_register); |
| |
| void elv_unregister(struct elevator_type *e) |
| { |
| spin_lock_irq(&elv_list_lock); |
| list_del_init(&e->list); |
| spin_unlock_irq(&elv_list_lock); |
| } |
| EXPORT_SYMBOL_GPL(elv_unregister); |
| |
| /* |
| * switch to new_e io scheduler. be careful not to introduce deadlocks - |
| * we don't free the old io scheduler, before we have allocated what we |
| * need for the new one. this way we have a chance of going back to the old |
| * one, if the new one fails init for some reason. we also do an intermediate |
| * switch to noop to ensure safety with stack-allocated requests, since they |
| * don't originate from the block layer allocator. noop is safe here, because |
| * it never needs to touch the elevator itself for completion events. DRAIN |
| * flags will make sure we don't touch it for additions either. |
| */ |
| static void elevator_switch(request_queue_t *q, struct elevator_type *new_e) |
| { |
| elevator_t *e = kmalloc(sizeof(elevator_t), GFP_KERNEL); |
| struct elevator_type *noop_elevator = NULL; |
| elevator_t *old_elevator; |
| |
| if (!e) |
| goto error; |
| |
| /* |
| * first step, drain requests from the block freelist |
| */ |
| blk_wait_queue_drained(q, 0); |
| |
| /* |
| * unregister old elevator data |
| */ |
| elv_unregister_queue(q); |
| old_elevator = q->elevator; |
| |
| /* |
| * next step, switch to noop since it uses no private rq structures |
| * and doesn't allocate any memory for anything. then wait for any |
| * non-fs requests in-flight |
| */ |
| noop_elevator = elevator_get("noop"); |
| spin_lock_irq(q->queue_lock); |
| elevator_attach(q, noop_elevator, e); |
| spin_unlock_irq(q->queue_lock); |
| |
| blk_wait_queue_drained(q, 1); |
| |
| /* |
| * attach and start new elevator |
| */ |
| if (elevator_attach(q, new_e, e)) |
| goto fail; |
| |
| if (elv_register_queue(q)) |
| goto fail_register; |
| |
| /* |
| * finally exit old elevator and start queue again |
| */ |
| elevator_exit(old_elevator); |
| blk_finish_queue_drain(q); |
| elevator_put(noop_elevator); |
| return; |
| |
| fail_register: |
| /* |
| * switch failed, exit the new io scheduler and reattach the old |
| * one again (along with re-adding the sysfs dir) |
| */ |
| elevator_exit(e); |
| fail: |
| q->elevator = old_elevator; |
| elv_register_queue(q); |
| blk_finish_queue_drain(q); |
| error: |
| if (noop_elevator) |
| elevator_put(noop_elevator); |
| elevator_put(new_e); |
| printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name); |
| } |
| |
| ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count) |
| { |
| char elevator_name[ELV_NAME_MAX]; |
| struct elevator_type *e; |
| |
| memset(elevator_name, 0, sizeof(elevator_name)); |
| strncpy(elevator_name, name, sizeof(elevator_name)); |
| |
| if (elevator_name[strlen(elevator_name) - 1] == '\n') |
| elevator_name[strlen(elevator_name) - 1] = '\0'; |
| |
| e = elevator_get(elevator_name); |
| if (!e) { |
| printk(KERN_ERR "elevator: type %s not found\n", elevator_name); |
| return -EINVAL; |
| } |
| |
| if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) |
| return count; |
| |
| elevator_switch(q, e); |
| return count; |
| } |
| |
| ssize_t elv_iosched_show(request_queue_t *q, char *name) |
| { |
| elevator_t *e = q->elevator; |
| struct elevator_type *elv = e->elevator_type; |
| struct list_head *entry; |
| int len = 0; |
| |
| spin_lock_irq(q->queue_lock); |
| list_for_each(entry, &elv_list) { |
| struct elevator_type *__e; |
| |
| __e = list_entry(entry, struct elevator_type, list); |
| if (!strcmp(elv->elevator_name, __e->elevator_name)) |
| len += sprintf(name+len, "[%s] ", elv->elevator_name); |
| else |
| len += sprintf(name+len, "%s ", __e->elevator_name); |
| } |
| spin_unlock_irq(q->queue_lock); |
| |
| len += sprintf(len+name, "\n"); |
| return len; |
| } |
| |
| EXPORT_SYMBOL(elv_add_request); |
| EXPORT_SYMBOL(__elv_add_request); |
| EXPORT_SYMBOL(elv_requeue_request); |
| EXPORT_SYMBOL(elv_next_request); |
| EXPORT_SYMBOL(elv_remove_request); |
| EXPORT_SYMBOL(elv_queue_empty); |
| EXPORT_SYMBOL(elv_completed_request); |
| EXPORT_SYMBOL(elevator_exit); |
| EXPORT_SYMBOL(elevator_init); |