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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  *  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/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 <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 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->type->ops.allow_merge)
         return e->type->ops.allow_merge(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 inline bool elv_support_features(unsigned int elv_features,
                     unsigned int required_features)
 {
     return (required_features & elv_features) == required_features;
 }
 
 /**
  * elevator_match - Test an elevator name and features
  * @e: Scheduler to test
  * @name: Elevator name to test
  * @required_features: Features that the elevator must provide
  *
  * Return true if the elevator @e name matches @name and if @e provides all
  * the features specified by @required_features.
  */
 static bool elevator_match(const struct elevator_type *e, const char *name,
                unsigned int required_features)
 {
     if (!elv_support_features(e->elevator_features, required_features))
         return false;
     if (!strcmp(e->elevator_name, name))
         return true;
     if (e->elevator_alias && !strcmp(e->elevator_alias, name))
         return true;
 
     return false;
 }
 
 /**
  * elevator_find - Find an elevator
  * @name: Name of the elevator to find
  * @required_features: Features that the elevator must provide
  *
  * Return the first registered scheduler with name @name and supporting the
  * features @required_features and NULL otherwise.
  */
 static struct elevator_type *elevator_find(const char *name,
                        unsigned int required_features)
 {
     struct elevator_type *e;
 
     list_for_each_entry(e, &elv_list, list) {
         if (elevator_match(e, name, required_features))
             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->required_elevator_features);
     if (!e && try_loading) {
         spin_unlock(&elv_list_lock);
         request_module("%s-iosched", name);
         spin_lock(&elv_list_lock);
         e = elevator_find(name, q->required_elevator_features);
     }
 
     if (e && !try_module_get(e->elevator_owner))
         e = NULL;
 
     spin_unlock(&elv_list_lock);
     return e;
 }
 
 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);
 
     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);
 }
 
 void elevator_exit(struct request_queue *q)
 {
     struct elevator_queue *e = q->elevator;
 
     ioc_clear_queue(q);
     blk_mq_sched_free_rqs(q);
 
     mutex_lock(&e->sysfs_lock);
     blk_mq_exit_sched(q, e);
     mutex_unlock(&e->sysfs_lock);
 
     kobject_put(&e->kobj);
 }
 
 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((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, bool uevent)
 {
     struct elevator_queue *e = q->elevator;
     int error;
 
     lockdep_assert_held(&q->sysfs_lock);
 
     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++;
             }
         }
         if (uevent)
             kobject_uevent(&e->kobj, KOBJ_ADD);
 
         e->registered = 1;
     }
     return error;
 }
 
 void elv_unregister_queue(struct request_queue *q)
 {
     struct elevator_queue *e = q->elevator;
 
     lockdep_assert_held(&q->sysfs_lock);
 
     if (e && e->registered) {
         struct elevator_queue *e = q->elevator;
 
         kobject_uevent(&e->kobj, KOBJ_REMOVE);
         kobject_del(&e->kobj);
 
         e->registered = 0;
     }
 }
 
 int elv_register(struct elevator_type *e)
 {
     /* 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, 0)) {
         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);
 
 int elevator_switch_mq(struct request_queue *q,
                   struct elevator_type *new_e)
 {
     int ret;
 
     lockdep_assert_held(&q->sysfs_lock);
 
     if (q->elevator) {
         elv_unregister_queue(q);
         elevator_exit(q);
     }
 
     ret = blk_mq_init_sched(q, new_e);
     if (ret)
         goto out;
 
     if (new_e) {
         ret = elv_register_queue(q, true);
         if (ret) {
             elevator_exit(q);
             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:
     return ret;
 }
 
 static inline bool elv_support_iosched(struct request_queue *q)
 {
     if (!queue_is_mq(q) ||
         (q->tag_set && (q->tag_set->flags & BLK_MQ_F_NO_SCHED)))
         return false;
     return true;
 }
 
 /*
  * For single queue devices, default to using mq-deadline. If we have multiple
  * queues or mq-deadline is not available, default to "none".
  */
 static struct elevator_type *elevator_get_default(struct request_queue *q)
 {
     if (q->tag_set && q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT)
         return NULL;
 
     if (q->nr_hw_queues != 1 &&
         !blk_mq_is_shared_tags(q->tag_set->flags))
         return NULL;
 
     return elevator_get(q, "mq-deadline", false);
 }
 
 /*
  * Get the first elevator providing the features required by the request queue.
  * Default to "none" if no matching elevator is found.
  */
 static struct elevator_type *elevator_get_by_features(struct request_queue *q)
 {
     struct elevator_type *e, *found = NULL;
 
     spin_lock(&elv_list_lock);
 
     list_for_each_entry(e, &elv_list, list) {
         if (elv_support_features(e->elevator_features,
                      q->required_elevator_features)) {
             found = e;
             break;
         }
     }
 
     if (found && !try_module_get(found->elevator_owner))
         found = NULL;
 
     spin_unlock(&elv_list_lock);
     return found;
 }
 
 /*
  * For a device queue that has no required features, use the default elevator
  * settings. Otherwise, use the first elevator available matching the required
  * features. If no suitable elevator is find or if the chosen elevator
  * initialization fails, fall back to the "none" elevator (no elevator).
  */
 void elevator_init_mq(struct request_queue *q)
 {
     struct elevator_type *e;
     int err;
 
     if (!elv_support_iosched(q))
         return;
 
     WARN_ON_ONCE(blk_queue_registered(q));
 
     if (unlikely(q->elevator))
         return;
 
     if (!q->required_elevator_features)
         e = elevator_get_default(q);
     else
         e = elevator_get_by_features(q);
     if (!e)
         return;
 
     /*
      * We are 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.
      */
     blk_mq_freeze_queue(q);
     blk_mq_cancel_work_sync(q);
 
     err = blk_mq_init_sched(q, e);
 
     blk_mq_unfreeze_queue(q);
 
     if (err) {
         pr_warn("\"%s\" elevator initialization failed, "
             "falling back to \"none\"\n", e->elevator_name);
         elevator_put(e);
     }
 }
 
 /*
  * 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)
 {
     int err;
 
     lockdep_assert_held(&q->sysfs_lock);
 
     blk_mq_freeze_queue(q);
     blk_mq_quiesce_queue(q);
 
     err = elevator_switch_mq(q, new_e);
 
     blk_mq_unquiesce_queue(q);
     blk_mq_unfreeze_queue(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 (!blk_queue_registered(q))
         return -ENOENT;
 
     /*
      * Special case for mq, turn off scheduling
      */
     if (!strncmp(name, "none", 4)) {
         if (!q->elevator)
             return 0;
         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, 0)) {
         elevator_put(e);
         return 0;
     }
 
     return elevator_switch(q, e);
 }
 
 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
               size_t count)
 {
     int ret;
 
     if (!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;
     int len = 0;
 
     if (!queue_is_mq(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, 0)) {
             len += sprintf(name+len, "[%s] ", elv->elevator_name);
             continue;
         }
         if (elv_support_iosched(q) &&
             elevator_match(__e, __e->elevator_name,
                    q->required_elevator_features))
             len += sprintf(name+len, "%s ", __e->elevator_name);
     }
     spin_unlock(&elv_list_lock);
 
     if (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);
 
 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);

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