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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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#include <trace/events/block.h>
#include "elevator.h"#include "blk.h"#include "blk-mq-sched.h"#include "blk-pm.h"#include "blk-wbt.h"#include "blk-cgroup.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 bool 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->type->ops.allow_merge) return e->type->ops.allow_merge(q, rq, bio);
return true;}
/* * 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);
/** * elevator_match - Check whether @e's name or alias matches @name * @e: Scheduler to test * @name: Elevator name to test * * Return true if the elevator @e's name or alias matches @name. */static bool elevator_match(const struct elevator_type *e, const char *name){ return !strcmp(e->elevator_name, name) || (e->elevator_alias && !strcmp(e->elevator_alias, name));}
static struct elevator_type *__elevator_find(const char *name){ struct elevator_type *e;
list_for_each_entry(e, &elv_list, list) if (elevator_match(e, name)) return e; return NULL;}
static struct elevator_type *elevator_find_get(const char *name){ struct elevator_type *e;
spin_lock(&elv_list_lock); e = __elevator_find(name); if (e && (!elevator_tryget(e))) e = NULL; spin_unlock(&elv_list_lock); return e;}
static const struct kobj_type elv_ktype;
struct elevator_queue *elevator_alloc(struct request_queue *q, struct elevator_type *e, struct elevator_resources *res){ struct elevator_queue *eq;
eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node); if (unlikely(!eq)) return NULL;
__elevator_get(e); eq->type = e; kobject_init(&eq->kobj, &elv_ktype); mutex_init(&eq->sysfs_lock); hash_init(eq->hash); eq->et = res->et; eq->elevator_data = res->data;
return eq;}
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);}
static void elevator_exit(struct request_queue *q){ struct elevator_queue *e = q->elevator;
lockdep_assert_held(&q->elevator_lock);
ioc_clear_queue(q);
mutex_lock(&e->sysfs_lock); blk_mq_exit_sched(q, e); mutex_unlock(&e->sysfs_lock);}
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);
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;
if (blk_discard_mergable(__rq)) return ELEVATOR_DISCARD_MERGE; return ELEVATOR_BACK_MERGE; }
if (e->type->ops.request_merge) return e->type->ops.request_merge(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. 'free' will contain all * requests that need to be freed. */bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq, struct list_head *free){ 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)) { list_add(&rq->queuelist, free); 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;
list_add(&rq->queuelist, free); /* 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->type->ops.request_merged) e->type->ops.request_merged(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;
if (e->type->ops.requests_merged) e->type->ops.requests_merged(q, rq, next);
elv_rqhash_reposition(q, rq); q->last_merge = rq;}
struct request *elv_latter_request(struct request_queue *q, struct request *rq){ struct elevator_queue *e = q->elevator;
if (e->type->ops.next_request) return e->type->ops.next_request(q, rq);
return NULL;}
struct request *elv_former_request(struct request_queue *q, struct request *rq){ struct elevator_queue *e = q->elevator;
if (e->type->ops.former_request) return e->type->ops.former_request(q, rq);
return NULL;}
#define to_elv(atr) container_of_const((atr), struct elv_fs_entry, attr)
static ssize_telv_attr_show(struct kobject *kobj, struct attribute *attr, char *page){ const struct elv_fs_entry *entry = to_elv(attr); struct elevator_queue *e; ssize_t error = -ENODEV;
if (!entry->show) return -EIO;
e = container_of(kobj, struct elevator_queue, kobj); mutex_lock(&e->sysfs_lock); if (!test_bit(ELEVATOR_FLAG_DYING, &e->flags)) error = entry->show(e, page); mutex_unlock(&e->sysfs_lock); return error;}
static ssize_telv_attr_store(struct kobject *kobj, struct attribute *attr, const char *page, size_t length){ const struct elv_fs_entry *entry = to_elv(attr); struct elevator_queue *e; ssize_t error = -ENODEV;
if (!entry->store) return -EIO;
e = container_of(kobj, struct elevator_queue, kobj); mutex_lock(&e->sysfs_lock); if (!test_bit(ELEVATOR_FLAG_DYING, &e->flags)) error = entry->store(e, page, length); mutex_unlock(&e->sysfs_lock); return error;}
static const struct sysfs_ops elv_sysfs_ops = { .show = elv_attr_show, .store = elv_attr_store,};
static const struct kobj_type elv_ktype = { .sysfs_ops = &elv_sysfs_ops, .release = elevator_release,};
static int elv_register_queue(struct request_queue *q, struct elevator_queue *e, bool uevent){ int error;
error = kobject_add(&e->kobj, &q->disk->queue_kobj, "iosched"); if (!error) { const 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++; } } if (uevent) kobject_uevent(&e->kobj, KOBJ_ADD);
/* * Sched is initialized, it is ready to export it via * debugfs */ blk_mq_sched_reg_debugfs(q); set_bit(ELEVATOR_FLAG_REGISTERED, &e->flags); } return error;}
static void elv_unregister_queue(struct request_queue *q, struct elevator_queue *e){ if (e && test_and_clear_bit(ELEVATOR_FLAG_REGISTERED, &e->flags)) { kobject_uevent(&e->kobj, KOBJ_REMOVE); kobject_del(&e->kobj);
/* unexport via debugfs before exiting sched */ blk_mq_sched_unreg_debugfs(q); }}
int elv_register(struct elevator_type *e){ /* finish request is mandatory */ if (WARN_ON_ONCE(!e->ops.finish_request)) return -EINVAL; /* insert_requests and dispatch_request are mandatory */ if (WARN_ON_ONCE(!e->ops.insert_requests || !e->ops.dispatch_request)) return -EINVAL;
/* 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)) { spin_unlock(&elv_list_lock); kmem_cache_destroy(e->icq_cache); return -EBUSY; } list_add_tail(&e->list, &elv_list); spin_unlock(&elv_list_lock);
printk(KERN_INFO "io scheduler %s registered\n", e->elevator_name);
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);
/* * Switch to new_e io scheduler. * * If switching fails, we are most likely running out of memory and not able * to restore the old io scheduler, so leaving the io scheduler being none. */static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx){ struct elevator_type *new_e = NULL; int ret = 0;
WARN_ON_ONCE(q->mq_freeze_depth == 0); lockdep_assert_held(&q->elevator_lock);
if (strncmp(ctx->name, "none", 4)) { new_e = elevator_find_get(ctx->name); if (!new_e) return -EINVAL; }
blk_mq_quiesce_queue(q);
if (q->elevator) { ctx->old = q->elevator; elevator_exit(q); }
if (new_e) { ret = blk_mq_init_sched(q, new_e, &ctx->res); if (ret) goto out_unfreeze; ctx->new = q->elevator; } else { blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q); q->elevator = NULL; q->nr_requests = q->tag_set->queue_depth; q->async_depth = q->tag_set->queue_depth; } blk_add_trace_msg(q, "elv switch: %s", ctx->name);
out_unfreeze: blk_mq_unquiesce_queue(q);
if (ret) { pr_warn("elv: switch to \"%s\" failed, falling back to \"none\"\n", new_e->elevator_name); }
if (new_e) elevator_put(new_e); return ret;}
static void elv_exit_and_release(struct elv_change_ctx *ctx, struct request_queue *q){ struct elevator_queue *e; unsigned memflags;
memflags = blk_mq_freeze_queue(q); mutex_lock(&q->elevator_lock); e = q->elevator; elevator_exit(q); mutex_unlock(&q->elevator_lock); blk_mq_unfreeze_queue(q, memflags); if (e) { blk_mq_free_sched_res(&ctx->res, ctx->type, q->tag_set); kobject_put(&e->kobj); }}
static int elevator_change_done(struct request_queue *q, struct elv_change_ctx *ctx){ int ret = 0;
if (ctx->old) { struct elevator_resources res = { .et = ctx->old->et, .data = ctx->old->elevator_data };
elv_unregister_queue(q, ctx->old); blk_mq_free_sched_res(&res, ctx->old->type, q->tag_set); kobject_put(&ctx->old->kobj); } if (ctx->new) { ret = elv_register_queue(q, ctx->new, !ctx->no_uevent); if (ret) elv_exit_and_release(ctx, q); } return ret;}
/* * Switch this queue to the given IO scheduler. */static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx){ unsigned int memflags; struct blk_mq_tag_set *set = q->tag_set; int ret = 0;
lockdep_assert_held(&set->update_nr_hwq_lock);
if (strncmp(ctx->name, "none", 4)) { ret = blk_mq_alloc_sched_res(q, ctx->type, &ctx->res, set->nr_hw_queues); if (ret) return ret; }
memflags = blk_mq_freeze_queue(q); /* * May be called before adding disk, when there isn't any FS I/O, * so freezing queue plus canceling dispatch work is enough to * drain any dispatch activities originated from passthrough * requests, then no need to quiesce queue which may add long boot * latency, especially when lots of disks are involved. * * Disk isn't added yet, so verifying queue lock only manually. */ blk_mq_cancel_work_sync(q); mutex_lock(&q->elevator_lock); if (!(q->elevator && elevator_match(q->elevator->type, ctx->name))) ret = elevator_switch(q, ctx); mutex_unlock(&q->elevator_lock); blk_mq_unfreeze_queue(q, memflags); if (!ret) ret = elevator_change_done(q, ctx);
/* * Free sched resource if it's allocated but we couldn't switch elevator. */ if (!ctx->new) blk_mq_free_sched_res(&ctx->res, ctx->type, set);
return ret;}
/* * The I/O scheduler depends on the number of hardware queues, this forces a * reattachment when nr_hw_queues changes. */void elv_update_nr_hw_queues(struct request_queue *q, struct elv_change_ctx *ctx){ struct blk_mq_tag_set *set = q->tag_set; int ret = -ENODEV;
WARN_ON_ONCE(q->mq_freeze_depth == 0);
if (ctx->type && !blk_queue_dying(q) && blk_queue_registered(q)) { mutex_lock(&q->elevator_lock); /* force to reattach elevator after nr_hw_queue is updated */ ret = elevator_switch(q, ctx); mutex_unlock(&q->elevator_lock); } blk_mq_unfreeze_queue_nomemrestore(q); if (!ret) WARN_ON_ONCE(elevator_change_done(q, ctx));
/* * Free sched resource if it's allocated but we couldn't switch elevator. */ if (!ctx->new) blk_mq_free_sched_res(&ctx->res, ctx->type, set);}
/* * Use the default elevator settings. If the chosen elevator initialization * fails, fall back to the "none" elevator (no elevator). */void elevator_set_default(struct request_queue *q){ struct elv_change_ctx ctx = { .name = "mq-deadline", .no_uevent = true, }; int err;
/* now we allow to switch elevator */ blk_queue_flag_clear(QUEUE_FLAG_NO_ELV_SWITCH, q);
if (q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT) return;
/* * For single queue devices, default to using mq-deadline. If we * have multiple queues or mq-deadline is not available, default * to "none". */ ctx.type = elevator_find_get(ctx.name); if (!ctx.type) return;
if ((q->nr_hw_queues == 1 || blk_mq_is_shared_tags(q->tag_set->flags))) { err = elevator_change(q, &ctx); if (err < 0) pr_warn("\"%s\" elevator initialization, failed %d, falling back to \"none\"\n", ctx.name, err); } elevator_put(ctx.type);}
void elevator_set_none(struct request_queue *q){ struct elv_change_ctx ctx = { .name = "none", }; int err;
err = elevator_change(q, &ctx); if (err < 0) pr_warn("%s: set none elevator failed %d\n", __func__, err);}
static void elv_iosched_load_module(const char *elevator_name){ struct elevator_type *found;
spin_lock(&elv_list_lock); found = __elevator_find(elevator_name); spin_unlock(&elv_list_lock);
if (!found) request_module("%s-iosched", elevator_name);}
ssize_t elv_iosched_store(struct gendisk *disk, const char *buf, size_t count){ char elevator_name[ELV_NAME_MAX]; struct elv_change_ctx ctx = {}; int ret; struct request_queue *q = disk->queue; struct blk_mq_tag_set *set = q->tag_set;
/* Make sure queue is not in the middle of being removed */ if (!blk_queue_registered(q)) return -ENOENT;
/* * If the attribute needs to load a module, do it before freezing the * queue to ensure that the module file can be read when the request * queue is the one for the device storing the module file. */ strscpy(elevator_name, buf, sizeof(elevator_name)); ctx.name = strstrip(elevator_name);
elv_iosched_load_module(ctx.name); ctx.type = elevator_find_get(ctx.name);
/* * Use trylock to avoid circular lock dependency with kernfs active * reference during concurrent disk deletion: * update_nr_hwq_lock -> kn->active (via del_gendisk -> kobject_del) * kn->active -> update_nr_hwq_lock (via this sysfs write path) * * Use the writer lock instead of the reader lock of update_nr_hwq_lock * to serialize the two-stage elevator switch steps in * elevator_change(): the core switch step under the elevator lock and * the elevator_change_done() step outside the elevator lock. */ if (!down_write_trylock(&set->update_nr_hwq_lock)) { ret = -EBUSY; goto out; } if (!blk_queue_no_elv_switch(q)) { ret = elevator_change(q, &ctx); if (!ret) ret = count; } else { ret = -ENOENT; } up_write(&set->update_nr_hwq_lock);
out: if (ctx.type) elevator_put(ctx.type); return ret;}
ssize_t elv_iosched_show(struct gendisk *disk, char *name){ struct request_queue *q = disk->queue; struct elevator_type *cur = NULL, *e; int len = 0;
mutex_lock(&q->elevator_lock); if (!q->elevator) { len += sprintf(name+len, "[none] "); } else { len += sprintf(name+len, "none "); cur = q->elevator->type; }
spin_lock(&elv_list_lock); list_for_each_entry(e, &elv_list, list) { if (e == cur) len += sprintf(name+len, "[%s] ", e->elevator_name); else len += sprintf(name+len, "%s ", e->elevator_name); } spin_unlock(&elv_list_lock);
len += sprintf(name+len, "\n"); mutex_unlock(&q->elevator_lock);
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);
static int __init elevator_setup(char *str){ pr_warn("Kernel parameter elevator= does not have any effect anymore.\n" "Please use sysfs to set IO scheduler for individual devices.\n"); return 1;}
__setup("elevator=", elevator_setup);