linux/block/elevator.c
Jens Axboe 8ac0d9a81e elevator: allow name aliases
Since we now lookup elevator types with the appropriate multiqueue
capability, allow schedulers to register with an alias alongside
the real name. This is in preparation for allowing 'mq-deadline'
to register an alias of 'deadline' as well.

Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-10-25 12:36:50 -06:00

1181 lines
27 KiB
C

/*
* Block device elevator/IO-scheduler.
*
* Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
*
* 30042000 Jens Axboe <axboe@kernel.dk> :
*
* 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/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/compiler.h>
#include <linux/blktrace_api.h>
#include <linux/hash.h>
#include <linux/uaccess.h>
#include <linux/pm_runtime.h>
#include <linux/blk-cgroup.h>
#include <trace/events/block.h>
#include "blk.h"
#include "blk-mq-sched.h"
#include "blk-wbt.h"
static DEFINE_SPINLOCK(elv_list_lock);
static LIST_HEAD(elv_list);
/*
* Merge hash stuff.
*/
#define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
/*
* Query io scheduler to see if the current process issuing bio may be
* merged with rq.
*/
static int elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio)
{
struct request_queue *q = rq->q;
struct elevator_queue *e = q->elevator;
if (e->uses_mq && e->type->ops.mq.allow_merge)
return e->type->ops.mq.allow_merge(q, rq, bio);
else if (!e->uses_mq && e->type->ops.sq.elevator_allow_bio_merge_fn)
return e->type->ops.sq.elevator_allow_bio_merge_fn(q, rq, bio);
return 1;
}
/*
* can we safely merge with this request?
*/
bool elv_bio_merge_ok(struct request *rq, struct bio *bio)
{
if (!blk_rq_merge_ok(rq, bio))
return false;
if (!elv_iosched_allow_bio_merge(rq, bio))
return false;
return true;
}
EXPORT_SYMBOL(elv_bio_merge_ok);
static bool elevator_match(const struct elevator_type *e, const char *name)
{
if (!strcmp(e->elevator_name, name))
return true;
if (e->elevator_alias && !strcmp(e->elevator_alias, name))
return true;
return false;
}
/*
* Return scheduler with name 'name' and with matching 'mq capability
*/
static struct elevator_type *elevator_find(const char *name, bool mq)
{
struct elevator_type *e;
list_for_each_entry(e, &elv_list, list) {
if (elevator_match(e, name) && (mq == e->uses_mq))
return e;
}
return NULL;
}
static void elevator_put(struct elevator_type *e)
{
module_put(e->elevator_owner);
}
static struct elevator_type *elevator_get(struct request_queue *q,
const char *name, bool try_loading)
{
struct elevator_type *e;
spin_lock(&elv_list_lock);
e = elevator_find(name, q->mq_ops != NULL);
if (!e && try_loading) {
spin_unlock(&elv_list_lock);
request_module("%s-iosched", name);
spin_lock(&elv_list_lock);
e = elevator_find(name, q->mq_ops != NULL);
}
if (e && !try_module_get(e->elevator_owner))
e = NULL;
spin_unlock(&elv_list_lock);
return e;
}
static char chosen_elevator[ELV_NAME_MAX];
static int __init elevator_setup(char *str)
{
/*
* Be backwards-compatible with previous kernels, so users
* won't get the wrong elevator.
*/
strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
return 1;
}
__setup("elevator=", elevator_setup);
/* called during boot to load the elevator chosen by the elevator param */
void __init load_default_elevator_module(void)
{
struct elevator_type *e;
if (!chosen_elevator[0])
return;
/*
* Boot parameter is deprecated, we haven't supported that for MQ.
* Only look for non-mq schedulers from here.
*/
spin_lock(&elv_list_lock);
e = elevator_find(chosen_elevator, false);
spin_unlock(&elv_list_lock);
if (!e)
request_module("%s-iosched", chosen_elevator);
}
static struct kobj_type elv_ktype;
struct elevator_queue *elevator_alloc(struct request_queue *q,
struct elevator_type *e)
{
struct elevator_queue *eq;
eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
if (unlikely(!eq))
return NULL;
eq->type = e;
kobject_init(&eq->kobj, &elv_ktype);
mutex_init(&eq->sysfs_lock);
hash_init(eq->hash);
eq->uses_mq = e->uses_mq;
return eq;
}
EXPORT_SYMBOL(elevator_alloc);
static void elevator_release(struct kobject *kobj)
{
struct elevator_queue *e;
e = container_of(kobj, struct elevator_queue, kobj);
elevator_put(e->type);
kfree(e);
}
int elevator_init(struct request_queue *q, char *name)
{
struct elevator_type *e = NULL;
int err;
/*
* q->sysfs_lock must be held to provide mutual exclusion between
* elevator_switch() and here.
*/
lockdep_assert_held(&q->sysfs_lock);
if (unlikely(q->elevator))
return 0;
INIT_LIST_HEAD(&q->queue_head);
q->last_merge = NULL;
q->end_sector = 0;
q->boundary_rq = NULL;
if (name) {
e = elevator_get(q, name, true);
if (!e)
return -EINVAL;
}
/*
* Use the default elevator specified by config boot param for
* non-mq devices, or by config option. Don't try to load modules
* as we could be running off async and request_module() isn't
* allowed from async.
*/
if (!e && !q->mq_ops && *chosen_elevator) {
e = elevator_get(q, chosen_elevator, false);
if (!e)
printk(KERN_ERR "I/O scheduler %s not found\n",
chosen_elevator);
}
if (!e) {
/*
* For blk-mq devices, we default to using mq-deadline,
* if available, for single queue devices. If deadline
* isn't available OR we have multiple queues, default
* to "none".
*/
if (q->mq_ops) {
if (q->nr_hw_queues == 1)
e = elevator_get(q, "mq-deadline", false);
if (!e)
return 0;
} else
e = elevator_get(q, CONFIG_DEFAULT_IOSCHED, false);
if (!e) {
printk(KERN_ERR
"Default I/O scheduler not found. " \
"Using noop.\n");
e = elevator_get(q, "noop", false);
}
}
if (e->uses_mq)
err = blk_mq_init_sched(q, e);
else
err = e->ops.sq.elevator_init_fn(q, e);
if (err)
elevator_put(e);
return err;
}
EXPORT_SYMBOL(elevator_init);
void elevator_exit(struct request_queue *q, struct elevator_queue *e)
{
mutex_lock(&e->sysfs_lock);
if (e->uses_mq && e->type->ops.mq.exit_sched)
blk_mq_exit_sched(q, e);
else if (!e->uses_mq && e->type->ops.sq.elevator_exit_fn)
e->type->ops.sq.elevator_exit_fn(e);
mutex_unlock(&e->sysfs_lock);
kobject_put(&e->kobj);
}
EXPORT_SYMBOL(elevator_exit);
static inline void __elv_rqhash_del(struct request *rq)
{
hash_del(&rq->hash);
rq->rq_flags &= ~RQF_HASHED;
}
void elv_rqhash_del(struct request_queue *q, struct request *rq)
{
if (ELV_ON_HASH(rq))
__elv_rqhash_del(rq);
}
EXPORT_SYMBOL_GPL(elv_rqhash_del);
void elv_rqhash_add(struct request_queue *q, struct request *rq)
{
struct elevator_queue *e = q->elevator;
BUG_ON(ELV_ON_HASH(rq));
hash_add(e->hash, &rq->hash, rq_hash_key(rq));
rq->rq_flags |= RQF_HASHED;
}
EXPORT_SYMBOL_GPL(elv_rqhash_add);
void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
{
__elv_rqhash_del(rq);
elv_rqhash_add(q, rq);
}
struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
{
struct elevator_queue *e = q->elevator;
struct hlist_node *next;
struct request *rq;
hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
BUG_ON(!ELV_ON_HASH(rq));
if (unlikely(!rq_mergeable(rq))) {
__elv_rqhash_del(rq);
continue;
}
if (rq_hash_key(rq) == offset)
return rq;
}
return NULL;
}
/*
* RB-tree support functions for inserting/lookup/removal of requests
* in a sorted RB tree.
*/
void elv_rb_add(struct rb_root *root, struct request *rq)
{
struct rb_node **p = &root->rb_node;
struct rb_node *parent = NULL;
struct request *__rq;
while (*p) {
parent = *p;
__rq = rb_entry(parent, struct request, rb_node);
if (blk_rq_pos(rq) < blk_rq_pos(__rq))
p = &(*p)->rb_left;
else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
p = &(*p)->rb_right;
}
rb_link_node(&rq->rb_node, parent, p);
rb_insert_color(&rq->rb_node, root);
}
EXPORT_SYMBOL(elv_rb_add);
void elv_rb_del(struct rb_root *root, struct request *rq)
{
BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
rb_erase(&rq->rb_node, root);
RB_CLEAR_NODE(&rq->rb_node);
}
EXPORT_SYMBOL(elv_rb_del);
struct request *elv_rb_find(struct rb_root *root, sector_t sector)
{
struct rb_node *n = root->rb_node;
struct request *rq;
while (n) {
rq = rb_entry(n, struct request, rb_node);
if (sector < blk_rq_pos(rq))
n = n->rb_left;
else if (sector > blk_rq_pos(rq))
n = n->rb_right;
else
return rq;
}
return NULL;
}
EXPORT_SYMBOL(elv_rb_find);
/*
* Insert rq into dispatch queue of q. Queue lock must be held on
* entry. rq is sort instead into the dispatch queue. To be used by
* specific elevators.
*/
void elv_dispatch_sort(struct request_queue *q, struct request *rq)
{
sector_t boundary;
struct list_head *entry;
if (q->last_merge == rq)
q->last_merge = NULL;
elv_rqhash_del(q, rq);
q->nr_sorted--;
boundary = q->end_sector;
list_for_each_prev(entry, &q->queue_head) {
struct request *pos = list_entry_rq(entry);
if (req_op(rq) != req_op(pos))
break;
if (rq_data_dir(rq) != rq_data_dir(pos))
break;
if (pos->rq_flags & (RQF_STARTED | RQF_SOFTBARRIER))
break;
if (blk_rq_pos(rq) >= boundary) {
if (blk_rq_pos(pos) < boundary)
continue;
} else {
if (blk_rq_pos(pos) >= boundary)
break;
}
if (blk_rq_pos(rq) >= blk_rq_pos(pos))
break;
}
list_add(&rq->queuelist, entry);
}
EXPORT_SYMBOL(elv_dispatch_sort);
/*
* Insert rq into dispatch queue of q. Queue lock must be held on
* entry. rq is added to the back of the dispatch queue. To be used by
* specific elevators.
*/
void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
{
if (q->last_merge == rq)
q->last_merge = NULL;
elv_rqhash_del(q, rq);
q->nr_sorted--;
q->end_sector = rq_end_sector(rq);
q->boundary_rq = rq;
list_add_tail(&rq->queuelist, &q->queue_head);
}
EXPORT_SYMBOL(elv_dispatch_add_tail);
enum elv_merge elv_merge(struct request_queue *q, struct request **req,
struct bio *bio)
{
struct elevator_queue *e = q->elevator;
struct request *__rq;
/*
* Levels of merges:
* nomerges: No merges at all attempted
* noxmerges: Only simple one-hit cache try
* merges: All merge tries attempted
*/
if (blk_queue_nomerges(q) || !bio_mergeable(bio))
return ELEVATOR_NO_MERGE;
/*
* First try one-hit cache.
*/
if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) {
enum elv_merge ret = blk_try_merge(q->last_merge, bio);
if (ret != ELEVATOR_NO_MERGE) {
*req = q->last_merge;
return ret;
}
}
if (blk_queue_noxmerges(q))
return ELEVATOR_NO_MERGE;
/*
* See if our hash lookup can find a potential backmerge.
*/
__rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
if (__rq && elv_bio_merge_ok(__rq, bio)) {
*req = __rq;
return ELEVATOR_BACK_MERGE;
}
if (e->uses_mq && e->type->ops.mq.request_merge)
return e->type->ops.mq.request_merge(q, req, bio);
else if (!e->uses_mq && e->type->ops.sq.elevator_merge_fn)
return e->type->ops.sq.elevator_merge_fn(q, req, bio);
return ELEVATOR_NO_MERGE;
}
/*
* Attempt to do an insertion back merge. Only check for the case where
* we can append 'rq' to an existing request, so we can throw 'rq' away
* afterwards.
*
* Returns true if we merged, false otherwise
*/
bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq)
{
struct request *__rq;
bool ret;
if (blk_queue_nomerges(q))
return false;
/*
* First try one-hit cache.
*/
if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
return true;
if (blk_queue_noxmerges(q))
return false;
ret = false;
/*
* See if our hash lookup can find a potential backmerge.
*/
while (1) {
__rq = elv_rqhash_find(q, blk_rq_pos(rq));
if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
break;
/* The merged request could be merged with others, try again */
ret = true;
rq = __rq;
}
return ret;
}
void elv_merged_request(struct request_queue *q, struct request *rq,
enum elv_merge type)
{
struct elevator_queue *e = q->elevator;
if (e->uses_mq && e->type->ops.mq.request_merged)
e->type->ops.mq.request_merged(q, rq, type);
else if (!e->uses_mq && e->type->ops.sq.elevator_merged_fn)
e->type->ops.sq.elevator_merged_fn(q, rq, type);
if (type == ELEVATOR_BACK_MERGE)
elv_rqhash_reposition(q, rq);
q->last_merge = rq;
}
void elv_merge_requests(struct request_queue *q, struct request *rq,
struct request *next)
{
struct elevator_queue *e = q->elevator;
bool next_sorted = false;
if (e->uses_mq && e->type->ops.mq.requests_merged)
e->type->ops.mq.requests_merged(q, rq, next);
else if (e->type->ops.sq.elevator_merge_req_fn) {
next_sorted = (__force bool)(next->rq_flags & RQF_SORTED);
if (next_sorted)
e->type->ops.sq.elevator_merge_req_fn(q, rq, next);
}
elv_rqhash_reposition(q, rq);
if (next_sorted) {
elv_rqhash_del(q, next);
q->nr_sorted--;
}
q->last_merge = rq;
}
void elv_bio_merged(struct request_queue *q, struct request *rq,
struct bio *bio)
{
struct elevator_queue *e = q->elevator;
if (WARN_ON_ONCE(e->uses_mq))
return;
if (e->type->ops.sq.elevator_bio_merged_fn)
e->type->ops.sq.elevator_bio_merged_fn(q, rq, bio);
}
#ifdef CONFIG_PM
static void blk_pm_requeue_request(struct request *rq)
{
if (rq->q->dev && !(rq->rq_flags & RQF_PM))
rq->q->nr_pending--;
}
static void blk_pm_add_request(struct request_queue *q, struct request *rq)
{
if (q->dev && !(rq->rq_flags & RQF_PM) && q->nr_pending++ == 0 &&
(q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
pm_request_resume(q->dev);
}
#else
static inline void blk_pm_requeue_request(struct request *rq) {}
static inline void blk_pm_add_request(struct request_queue *q,
struct request *rq)
{
}
#endif
void elv_requeue_request(struct request_queue *q, struct request *rq)
{
/*
* it already went through dequeue, we need to decrement the
* in_flight count again
*/
if (blk_account_rq(rq)) {
q->in_flight[rq_is_sync(rq)]--;
if (rq->rq_flags & RQF_SORTED)
elv_deactivate_rq(q, rq);
}
rq->rq_flags &= ~RQF_STARTED;
blk_pm_requeue_request(rq);
__elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
}
void elv_drain_elevator(struct request_queue *q)
{
struct elevator_queue *e = q->elevator;
static int printed;
if (WARN_ON_ONCE(e->uses_mq))
return;
lockdep_assert_held(q->queue_lock);
while (e->type->ops.sq.elevator_dispatch_fn(q, 1))
;
if (q->nr_sorted && printed++ < 10) {
printk(KERN_ERR "%s: forced dispatching is broken "
"(nr_sorted=%u), please report this\n",
q->elevator->type->elevator_name, q->nr_sorted);
}
}
void __elv_add_request(struct request_queue *q, struct request *rq, int where)
{
trace_block_rq_insert(q, rq);
blk_pm_add_request(q, rq);
rq->q = q;
if (rq->rq_flags & RQF_SOFTBARRIER) {
/* barriers are scheduling boundary, update end_sector */
if (!blk_rq_is_passthrough(rq)) {
q->end_sector = rq_end_sector(rq);
q->boundary_rq = rq;
}
} else if (!(rq->rq_flags & RQF_ELVPRIV) &&
(where == ELEVATOR_INSERT_SORT ||
where == ELEVATOR_INSERT_SORT_MERGE))
where = ELEVATOR_INSERT_BACK;
switch (where) {
case ELEVATOR_INSERT_REQUEUE:
case ELEVATOR_INSERT_FRONT:
rq->rq_flags |= RQF_SOFTBARRIER;
list_add(&rq->queuelist, &q->queue_head);
break;
case ELEVATOR_INSERT_BACK:
rq->rq_flags |= RQF_SOFTBARRIER;
elv_drain_elevator(q);
list_add_tail(&rq->queuelist, &q->queue_head);
/*
* We kick the queue here for the following reasons.
* - The elevator might have returned NULL previously
* to delay requests and returned them now. As the
* queue wasn't empty before this request, ll_rw_blk
* won't run the queue on return, resulting in hang.
* - Usually, back inserted requests won't be merged
* with anything. There's no point in delaying queue
* processing.
*/
__blk_run_queue(q);
break;
case ELEVATOR_INSERT_SORT_MERGE:
/*
* If we succeed in merging this request with one in the
* queue already, we are done - rq has now been freed,
* so no need to do anything further.
*/
if (elv_attempt_insert_merge(q, rq))
break;
/* fall through */
case ELEVATOR_INSERT_SORT:
BUG_ON(blk_rq_is_passthrough(rq));
rq->rq_flags |= RQF_SORTED;
q->nr_sorted++;
if (rq_mergeable(rq)) {
elv_rqhash_add(q, rq);
if (!q->last_merge)
q->last_merge = rq;
}
/*
* Some ioscheds (cfq) run q->request_fn directly, so
* rq cannot be accessed after calling
* elevator_add_req_fn.
*/
q->elevator->type->ops.sq.elevator_add_req_fn(q, rq);
break;
case ELEVATOR_INSERT_FLUSH:
rq->rq_flags |= RQF_SOFTBARRIER;
blk_insert_flush(rq);
break;
default:
printk(KERN_ERR "%s: bad insertion point %d\n",
__func__, where);
BUG();
}
}
EXPORT_SYMBOL(__elv_add_request);
void elv_add_request(struct request_queue *q, struct request *rq, int where)
{
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
__elv_add_request(q, rq, where);
spin_unlock_irqrestore(q->queue_lock, flags);
}
EXPORT_SYMBOL(elv_add_request);
struct request *elv_latter_request(struct request_queue *q, struct request *rq)
{
struct elevator_queue *e = q->elevator;
if (e->uses_mq && e->type->ops.mq.next_request)
return e->type->ops.mq.next_request(q, rq);
else if (!e->uses_mq && e->type->ops.sq.elevator_latter_req_fn)
return e->type->ops.sq.elevator_latter_req_fn(q, rq);
return NULL;
}
struct request *elv_former_request(struct request_queue *q, struct request *rq)
{
struct elevator_queue *e = q->elevator;
if (e->uses_mq && e->type->ops.mq.former_request)
return e->type->ops.mq.former_request(q, rq);
if (!e->uses_mq && e->type->ops.sq.elevator_former_req_fn)
return e->type->ops.sq.elevator_former_req_fn(q, rq);
return NULL;
}
int elv_set_request(struct request_queue *q, struct request *rq,
struct bio *bio, gfp_t gfp_mask)
{
struct elevator_queue *e = q->elevator;
if (WARN_ON_ONCE(e->uses_mq))
return 0;
if (e->type->ops.sq.elevator_set_req_fn)
return e->type->ops.sq.elevator_set_req_fn(q, rq, bio, gfp_mask);
return 0;
}
void elv_put_request(struct request_queue *q, struct request *rq)
{
struct elevator_queue *e = q->elevator;
if (WARN_ON_ONCE(e->uses_mq))
return;
if (e->type->ops.sq.elevator_put_req_fn)
e->type->ops.sq.elevator_put_req_fn(rq);
}
int elv_may_queue(struct request_queue *q, unsigned int op)
{
struct elevator_queue *e = q->elevator;
if (WARN_ON_ONCE(e->uses_mq))
return 0;
if (e->type->ops.sq.elevator_may_queue_fn)
return e->type->ops.sq.elevator_may_queue_fn(q, op);
return ELV_MQUEUE_MAY;
}
void elv_completed_request(struct request_queue *q, struct request *rq)
{
struct elevator_queue *e = q->elevator;
if (WARN_ON_ONCE(e->uses_mq))
return;
/*
* request is released from the driver, io must be done
*/
if (blk_account_rq(rq)) {
q->in_flight[rq_is_sync(rq)]--;
if ((rq->rq_flags & RQF_SORTED) &&
e->type->ops.sq.elevator_completed_req_fn)
e->type->ops.sq.elevator_completed_req_fn(q, rq);
}
}
#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
static ssize_t
elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
{
struct elv_fs_entry *entry = to_elv(attr);
struct elevator_queue *e;
ssize_t error;
if (!entry->show)
return -EIO;
e = container_of(kobj, struct elevator_queue, kobj);
mutex_lock(&e->sysfs_lock);
error = e->type ? entry->show(e, page) : -ENOENT;
mutex_unlock(&e->sysfs_lock);
return error;
}
static ssize_t
elv_attr_store(struct kobject *kobj, struct attribute *attr,
const char *page, size_t length)
{
struct elv_fs_entry *entry = to_elv(attr);
struct elevator_queue *e;
ssize_t error;
if (!entry->store)
return -EIO;
e = container_of(kobj, struct elevator_queue, kobj);
mutex_lock(&e->sysfs_lock);
error = e->type ? entry->store(e, page, length) : -ENOENT;
mutex_unlock(&e->sysfs_lock);
return error;
}
static const struct sysfs_ops elv_sysfs_ops = {
.show = elv_attr_show,
.store = elv_attr_store,
};
static struct kobj_type elv_ktype = {
.sysfs_ops = &elv_sysfs_ops,
.release = elevator_release,
};
int elv_register_queue(struct request_queue *q)
{
struct elevator_queue *e = q->elevator;
int error;
error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
if (!error) {
struct elv_fs_entry *attr = e->type->elevator_attrs;
if (attr) {
while (attr->attr.name) {
if (sysfs_create_file(&e->kobj, &attr->attr))
break;
attr++;
}
}
kobject_uevent(&e->kobj, KOBJ_ADD);
e->registered = 1;
if (!e->uses_mq && e->type->ops.sq.elevator_registered_fn)
e->type->ops.sq.elevator_registered_fn(q);
}
return error;
}
EXPORT_SYMBOL(elv_register_queue);
void elv_unregister_queue(struct request_queue *q)
{
if (q) {
struct elevator_queue *e = q->elevator;
kobject_uevent(&e->kobj, KOBJ_REMOVE);
kobject_del(&e->kobj);
e->registered = 0;
/* Re-enable throttling in case elevator disabled it */
wbt_enable_default(q);
}
}
EXPORT_SYMBOL(elv_unregister_queue);
int elv_register(struct elevator_type *e)
{
char *def = "";
/* create icq_cache if requested */
if (e->icq_size) {
if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
WARN_ON(e->icq_align < __alignof__(struct io_cq)))
return -EINVAL;
snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
"%s_io_cq", e->elevator_name);
e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
e->icq_align, 0, NULL);
if (!e->icq_cache)
return -ENOMEM;
}
/* register, don't allow duplicate names */
spin_lock(&elv_list_lock);
if (elevator_find(e->elevator_name, e->uses_mq)) {
spin_unlock(&elv_list_lock);
if (e->icq_cache)
kmem_cache_destroy(e->icq_cache);
return -EBUSY;
}
list_add_tail(&e->list, &elv_list);
spin_unlock(&elv_list_lock);
/* print pretty message */
if (elevator_match(e, chosen_elevator) ||
(!*chosen_elevator &&
elevator_match(e, CONFIG_DEFAULT_IOSCHED)))
def = " (default)";
printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
def);
return 0;
}
EXPORT_SYMBOL_GPL(elv_register);
void elv_unregister(struct elevator_type *e)
{
/* unregister */
spin_lock(&elv_list_lock);
list_del_init(&e->list);
spin_unlock(&elv_list_lock);
/*
* Destroy icq_cache if it exists. icq's are RCU managed. Make
* sure all RCU operations are complete before proceeding.
*/
if (e->icq_cache) {
rcu_barrier();
kmem_cache_destroy(e->icq_cache);
e->icq_cache = NULL;
}
}
EXPORT_SYMBOL_GPL(elv_unregister);
static int elevator_switch_mq(struct request_queue *q,
struct elevator_type *new_e)
{
int ret;
blk_mq_freeze_queue(q);
if (q->elevator) {
if (q->elevator->registered)
elv_unregister_queue(q);
ioc_clear_queue(q);
elevator_exit(q, q->elevator);
}
ret = blk_mq_init_sched(q, new_e);
if (ret)
goto out;
if (new_e) {
ret = elv_register_queue(q);
if (ret) {
elevator_exit(q, q->elevator);
goto out;
}
}
if (new_e)
blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
else
blk_add_trace_msg(q, "elv switch: none");
out:
blk_mq_unfreeze_queue(q);
return ret;
}
/*
* 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.
*/
static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
{
struct elevator_queue *old = q->elevator;
bool old_registered = false;
int err;
if (q->mq_ops)
return elevator_switch_mq(q, new_e);
/*
* Turn on BYPASS and drain all requests w/ elevator private data.
* Block layer doesn't call into a quiesced elevator - all requests
* are directly put on the dispatch list without elevator data
* using INSERT_BACK. All requests have SOFTBARRIER set and no
* merge happens either.
*/
if (old) {
old_registered = old->registered;
blk_queue_bypass_start(q);
/* unregister and clear all auxiliary data of the old elevator */
if (old_registered)
elv_unregister_queue(q);
ioc_clear_queue(q);
}
/* allocate, init and register new elevator */
err = new_e->ops.sq.elevator_init_fn(q, new_e);
if (err)
goto fail_init;
err = elv_register_queue(q);
if (err)
goto fail_register;
/* done, kill the old one and finish */
if (old) {
elevator_exit(q, old);
blk_queue_bypass_end(q);
}
blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
return 0;
fail_register:
elevator_exit(q, q->elevator);
fail_init:
/* switch failed, restore and re-register old elevator */
if (old) {
q->elevator = old;
elv_register_queue(q);
blk_queue_bypass_end(q);
}
return err;
}
/*
* Switch this queue to the given IO scheduler.
*/
static int __elevator_change(struct request_queue *q, const char *name)
{
char elevator_name[ELV_NAME_MAX];
struct elevator_type *e;
/* Make sure queue is not in the middle of being removed */
if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
return -ENOENT;
/*
* Special case for mq, turn off scheduling
*/
if (q->mq_ops && !strncmp(name, "none", 4))
return elevator_switch(q, NULL);
strlcpy(elevator_name, name, sizeof(elevator_name));
e = elevator_get(q, strstrip(elevator_name), true);
if (!e)
return -EINVAL;
if (q->elevator && elevator_match(q->elevator->type, elevator_name)) {
elevator_put(e);
return 0;
}
return elevator_switch(q, e);
}
static inline bool elv_support_iosched(struct request_queue *q)
{
if (q->mq_ops && q->tag_set && (q->tag_set->flags &
BLK_MQ_F_NO_SCHED))
return false;
return true;
}
ssize_t elv_iosched_store(struct request_queue *q, const char *name,
size_t count)
{
int ret;
if (!(q->mq_ops || q->request_fn) || !elv_support_iosched(q))
return count;
ret = __elevator_change(q, name);
if (!ret)
return count;
return ret;
}
ssize_t elv_iosched_show(struct request_queue *q, char *name)
{
struct elevator_queue *e = q->elevator;
struct elevator_type *elv = NULL;
struct elevator_type *__e;
bool uses_mq = q->mq_ops != NULL;
int len = 0;
if (!queue_is_rq_based(q))
return sprintf(name, "none\n");
if (!q->elevator)
len += sprintf(name+len, "[none] ");
else
elv = e->type;
spin_lock(&elv_list_lock);
list_for_each_entry(__e, &elv_list, list) {
if (elv && elevator_match(elv, __e->elevator_name) &&
(__e->uses_mq == uses_mq)) {
len += sprintf(name+len, "[%s] ", elv->elevator_name);
continue;
}
if (__e->uses_mq && q->mq_ops && elv_support_iosched(q))
len += sprintf(name+len, "%s ", __e->elevator_name);
else if (!__e->uses_mq && !q->mq_ops)
len += sprintf(name+len, "%s ", __e->elevator_name);
}
spin_unlock(&elv_list_lock);
if (q->mq_ops && q->elevator)
len += sprintf(name+len, "none");
len += sprintf(len+name, "\n");
return len;
}
struct request *elv_rb_former_request(struct request_queue *q,
struct request *rq)
{
struct rb_node *rbprev = rb_prev(&rq->rb_node);
if (rbprev)
return rb_entry_rq(rbprev);
return NULL;
}
EXPORT_SYMBOL(elv_rb_former_request);
struct request *elv_rb_latter_request(struct request_queue *q,
struct request *rq)
{
struct rb_node *rbnext = rb_next(&rq->rb_node);
if (rbnext)
return rb_entry_rq(rbnext);
return NULL;
}
EXPORT_SYMBOL(elv_rb_latter_request);