cregit-Linux how code gets into the kernel

Release 4.14 block/bfq-cgroup.c

Directory: block
/*
 * cgroups support for the BFQ I/O scheduler.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License as
 *  published by the Free Software Foundation; either version 2 of the
 *  License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  General Public License for more details.
 */
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/cgroup.h>
#include <linux/elevator.h>
#include <linux/ktime.h>
#include <linux/rbtree.h>
#include <linux/ioprio.h>
#include <linux/sbitmap.h>
#include <linux/delay.h>

#include "bfq-iosched.h"

#ifdef CONFIG_BFQ_GROUP_IOSCHED

/* bfqg stats flags */

enum bfqg_stats_flags {
	
BFQG_stats_waiting = 0,
	
BFQG_stats_idling,
	
BFQG_stats_empty,
};


#define BFQG_FLAG_FNS(name)						\
static void bfqg_stats_mark_##name(struct bfqg_stats *stats)    \
{                                                                       \
        stats->flags |= (1 << BFQG_stats_##name);                       \
}                                                                       \
static void bfqg_stats_clear_##name(struct bfqg_stats *stats)   \
{                                                                       \
        stats->flags &= ~(1 << BFQG_stats_##name);                      \
}                                                                       \
static int bfqg_stats_##name(struct bfqg_stats *stats)          \
{                                                                       \
        return (stats->flags & (1 << BFQG_stats_##name)) != 0;          \
}                                                                       \

BFQG_FLAG_FNS(waiting)
BFQG_FLAG_FNS(idling)
BFQG_FLAG_FNS(empty)

#undef BFQG_FLAG_FNS

/* This should be called with the scheduler lock held. */

static void bfqg_stats_update_group_wait_time(struct bfqg_stats *stats) { unsigned long long now; if (!bfqg_stats_waiting(stats)) return; now = sched_clock(); if (time_after64(now, stats->start_group_wait_time)) blkg_stat_add(&stats->group_wait_time, now - stats->start_group_wait_time); bfqg_stats_clear_waiting(stats); }

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/* This should be called with the scheduler lock held. */
static void bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg, struct bfq_group *curr_bfqg) { struct bfqg_stats *stats = &bfqg->stats; if (bfqg_stats_waiting(stats)) return; if (bfqg == curr_bfqg) return; stats->start_group_wait_time = sched_clock(); bfqg_stats_mark_waiting(stats); }

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/* This should be called with the scheduler lock held. */
static void bfqg_stats_end_empty_time(struct bfqg_stats *stats) { unsigned long long now; if (!bfqg_stats_empty(stats)) return; now = sched_clock(); if (time_after64(now, stats->start_empty_time)) blkg_stat_add(&stats->empty_time, now - stats->start_empty_time); bfqg_stats_clear_empty(stats); }

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void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { blkg_stat_add(&bfqg->stats.dequeue, 1); }

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void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { struct bfqg_stats *stats = &bfqg->stats; if (blkg_rwstat_total(&stats->queued)) return; /* * group is already marked empty. This can happen if bfqq got new * request in parent group and moved to this group while being added * to service tree. Just ignore the event and move on. */ if (bfqg_stats_empty(stats)) return; stats->start_empty_time = sched_clock(); bfqg_stats_mark_empty(stats); }

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void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { struct bfqg_stats *stats = &bfqg->stats; if (bfqg_stats_idling(stats)) { unsigned long long now = sched_clock(); if (time_after64(now, stats->start_idle_time)) blkg_stat_add(&stats->idle_time, now - stats->start_idle_time); bfqg_stats_clear_idling(stats); } }

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void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { struct bfqg_stats *stats = &bfqg->stats; stats->start_idle_time = sched_clock(); bfqg_stats_mark_idling(stats); }

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void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { struct bfqg_stats *stats = &bfqg->stats; blkg_stat_add(&stats->avg_queue_size_sum, blkg_rwstat_total(&stats->queued)); blkg_stat_add(&stats->avg_queue_size_samples, 1); bfqg_stats_update_group_wait_time(stats); }

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/* * blk-cgroup policy-related handlers * The following functions help in converting between blk-cgroup * internal structures and BFQ-specific structures. */
static struct bfq_group *pd_to_bfqg(struct blkg_policy_data *pd) { return pd ? container_of(pd, struct bfq_group, pd) : NULL; }

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struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg) { return pd_to_blkg(&bfqg->pd); }

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static struct bfq_group *blkg_to_bfqg(struct blkcg_gq *blkg) { return pd_to_bfqg(blkg_to_pd(blkg, &blkcg_policy_bfq)); }

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/* * bfq_group handlers * The following functions help in navigating the bfq_group hierarchy * by allowing to find the parent of a bfq_group or the bfq_group * associated to a bfq_queue. */
static struct bfq_group *bfqg_parent(struct bfq_group *bfqg) { struct blkcg_gq *pblkg = bfqg_to_blkg(bfqg)->parent; return pblkg ? blkg_to_bfqg(pblkg) : NULL; }

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struct bfq_group *bfqq_group(struct bfq_queue *bfqq) { struct bfq_entity *group_entity = bfqq->entity.parent; return group_entity ? container_of(group_entity, struct bfq_group, entity) : bfqq->bfqd->root_group; }

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/* * The following two functions handle get and put of a bfq_group by * wrapping the related blk-cgroup hooks. */
static void bfqg_get(struct bfq_group *bfqg) { bfqg->ref++; }

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static void bfqg_put(struct bfq_group *bfqg) { bfqg->ref--; if (bfqg->ref == 0) kfree(bfqg); }

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static void bfqg_and_blkg_get(struct bfq_group *bfqg) { /* see comments in bfq_bic_update_cgroup for why refcounting bfqg */ bfqg_get(bfqg); blkg_get(bfqg_to_blkg(bfqg)); }

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void bfqg_and_blkg_put(struct bfq_group *bfqg) { bfqg_put(bfqg); blkg_put(bfqg_to_blkg(bfqg)); }

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void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq, unsigned int op) { blkg_rwstat_add(&bfqg->stats.queued, op, 1); bfqg_stats_end_empty_time(&bfqg->stats); if (!(bfqq == ((struct bfq_data *)bfqg->bfqd)->in_service_queue)) bfqg_stats_set_start_group_wait_time(bfqg, bfqq_group(bfqq)); }

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void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { blkg_rwstat_add(&bfqg->stats.queued, op, -1); }

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void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { blkg_rwstat_add(&bfqg->stats.merged, op, 1); }

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void bfqg_stats_update_completion(struct bfq_group *bfqg, uint64_t start_time, uint64_t io_start_time, unsigned int op) { struct bfqg_stats *stats = &bfqg->stats; unsigned long long now = sched_clock(); if (time_after64(now, io_start_time)) blkg_rwstat_add(&stats->service_time, op, now - io_start_time); if (time_after64(io_start_time, start_time)) blkg_rwstat_add(&stats->wait_time, op, io_start_time - start_time); }

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/* @stats = 0 */
static void bfqg_stats_reset(struct bfqg_stats *stats) { /* queued stats shouldn't be cleared */ blkg_rwstat_reset(&stats->merged); blkg_rwstat_reset(&stats->service_time); blkg_rwstat_reset(&stats->wait_time); blkg_stat_reset(&stats->time); blkg_stat_reset(&stats->avg_queue_size_sum); blkg_stat_reset(&stats->avg_queue_size_samples); blkg_stat_reset(&stats->dequeue); blkg_stat_reset(&stats->group_wait_time); blkg_stat_reset(&stats->idle_time); blkg_stat_reset(&stats->empty_time); }

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/* @to += @from */
static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from) { if (!to || !from) return; /* queued stats shouldn't be cleared */ blkg_rwstat_add_aux(&to->merged, &from->merged); blkg_rwstat_add_aux(&to->service_time, &from->service_time); blkg_rwstat_add_aux(&to->wait_time, &from->wait_time); blkg_stat_add_aux(&from->time, &from->time); blkg_stat_add_aux(&to->avg_queue_size_sum, &from->avg_queue_size_sum); blkg_stat_add_aux(&to->avg_queue_size_samples, &from->avg_queue_size_samples); blkg_stat_add_aux(&to->dequeue, &from->dequeue); blkg_stat_add_aux(&to->group_wait_time, &from->group_wait_time); blkg_stat_add_aux(&to->idle_time, &from->idle_time); blkg_stat_add_aux(&to->empty_time, &from->empty_time); }

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/* * Transfer @bfqg's stats to its parent's aux counts so that the ancestors' * recursive stats can still account for the amount used by this bfqg after * it's gone. */
static void bfqg_stats_xfer_dead(struct bfq_group *bfqg) { struct bfq_group *parent; if (!bfqg) /* root_group */ return; parent = bfqg_parent(bfqg); lockdep_assert_held(bfqg_to_blkg(bfqg)->q->queue_lock); if (unlikely(!parent)) return; bfqg_stats_add_aux(&parent->stats, &bfqg->stats); bfqg_stats_reset(&bfqg->stats); }

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void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); entity->weight = entity->new_weight; entity->orig_weight = entity->new_weight; if (bfqq) { bfqq->ioprio = bfqq->new_ioprio; bfqq->ioprio_class = bfqq->new_ioprio_class; /* * Make sure that bfqg and its associated blkg do not * disappear before entity. */ bfqg_and_blkg_get(bfqg); } entity->parent = bfqg->my_entity; /* NULL for root group */ entity->sched_data = &bfqg->sched_data; }

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static void bfqg_stats_exit(struct bfqg_stats *stats) { blkg_rwstat_exit(&stats->merged); blkg_rwstat_exit(&stats->service_time); blkg_rwstat_exit(&stats->wait_time); blkg_rwstat_exit(&stats->queued); blkg_stat_exit(&stats->time); blkg_stat_exit(&stats->avg_queue_size_sum); blkg_stat_exit(&stats->avg_queue_size_samples); blkg_stat_exit(&stats->dequeue); blkg_stat_exit(&stats->group_wait_time); blkg_stat_exit(&stats->idle_time); blkg_stat_exit(&stats->empty_time); }

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static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp) { if (blkg_rwstat_init(&stats->merged, gfp) || blkg_rwstat_init(&stats->service_time, gfp) || blkg_rwstat_init(&stats->wait_time, gfp) || blkg_rwstat_init(&stats->queued, gfp) || blkg_stat_init(&stats->time, gfp) || blkg_stat_init(&stats->avg_queue_size_sum, gfp) || blkg_stat_init(&stats->avg_queue_size_samples, gfp) || blkg_stat_init(&stats->dequeue, gfp) || blkg_stat_init(&stats->group_wait_time, gfp) || blkg_stat_init(&stats->idle_time, gfp) || blkg_stat_init(&stats->empty_time, gfp)) { bfqg_stats_exit(stats); return -ENOMEM; } return 0; }

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static struct bfq_group_data *cpd_to_bfqgd(struct blkcg_policy_data *cpd) { return cpd ? container_of(cpd, struct bfq_group_data, pd) : NULL; }

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static struct bfq_group_data *blkcg_to_bfqgd(struct blkcg *blkcg) { return cpd_to_bfqgd(blkcg_to_cpd(blkcg, &blkcg_policy_bfq)); }

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static struct blkcg_policy_data *bfq_cpd_alloc(gfp_t gfp) { struct bfq_group_data *bgd; bgd = kzalloc(sizeof(*bgd), gfp); if (!bgd) return NULL; return &bgd->pd; }

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static void bfq_cpd_init(struct blkcg_policy_data *cpd) { struct bfq_group_data *d = cpd_to_bfqgd(cpd); d->weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ? CGROUP_WEIGHT_DFL : BFQ_WEIGHT_LEGACY_DFL; }

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static void bfq_cpd_free(struct blkcg_policy_data *cpd) { kfree(cpd_to_bfqgd(cpd)); }

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static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, int node) { struct bfq_group *bfqg; bfqg = kzalloc_node(sizeof(*bfqg), gfp, node); if (!bfqg) return NULL; if (bfqg_stats_init(&bfqg->stats, gfp)) { kfree(bfqg); return NULL; } /* see comments in bfq_bic_update_cgroup for why refcounting */ bfqg_get(bfqg); return &bfqg->pd; }

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static void bfq_pd_init(struct blkg_policy_data *pd) { struct blkcg_gq *blkg = pd_to_blkg(pd); struct bfq_group *bfqg = blkg_to_bfqg(blkg); struct bfq_data *bfqd = blkg->q->elevator->elevator_data; struct bfq_entity *entity = &bfqg->entity; struct bfq_group_data *d = blkcg_to_bfqgd(blkg->blkcg); entity->orig_weight = entity->weight = entity->new_weight = d->weight; entity->my_sched_data = &bfqg->sched_data; bfqg->my_entity = entity; /* * the root_group's will be set to NULL * in bfq_init_queue() */ bfqg->bfqd = bfqd; bfqg->active_entities = 0; bfqg->rq_pos_tree = RB_ROOT; }

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static void bfq_pd_free(struct blkg_policy_data *pd) { struct bfq_group *bfqg = pd_to_bfqg(pd); bfqg_stats_exit(&bfqg->stats); bfqg_put(bfqg); }

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static void bfq_pd_reset_stats(struct blkg_policy_data *pd) { struct bfq_group *bfqg = pd_to_bfqg(pd); bfqg_stats_reset(&bfqg->stats); }

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static void bfq_group_set_parent(struct bfq_group *bfqg, struct bfq_group *parent) { struct bfq_entity *entity; entity = &bfqg->entity; entity->parent = parent->my_entity; entity->sched_data = &parent->sched_data; }

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static struct bfq_group *bfq_lookup_bfqg(struct bfq_data *bfqd, struct blkcg *blkcg) { struct blkcg_gq *blkg; blkg = blkg_lookup(blkcg, bfqd->queue); if (likely(blkg)) return blkg_to_bfqg(blkg); return NULL; }

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struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd, struct blkcg *blkcg) { struct bfq_group *bfqg, *parent; struct bfq_entity *entity; bfqg = bfq_lookup_bfqg(bfqd, blkcg); if (unlikely(!bfqg)) return NULL; /* * Update chain of bfq_groups as we might be handling a leaf group * which, along with some of its relatives, has not been hooked yet * to the private hierarchy of BFQ. */ entity = &bfqg->entity; for_each_entity(entity) { bfqg = container_of(entity, struct bfq_group, entity); if (bfqg != bfqd->root_group) { parent = bfqg_parent(bfqg); if (!parent) parent = bfqd->root_group; bfq_group_set_parent(bfqg, parent); } } return bfqg; }

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/** * bfq_bfqq_move - migrate @bfqq to @bfqg. * @bfqd: queue descriptor. * @bfqq: the queue to move. * @bfqg: the group to move to. * * Move @bfqq to @bfqg, deactivating it from its old group and reactivating * it on the new one. Avoid putting the entity on the old group idle tree. * * Must be called under the scheduler lock, to make sure that the blkg * owning @bfqg does not disappear (see comments in * bfq_bic_update_cgroup on guaranteeing the consistency of blkg * objects). */
void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct bfq_group *bfqg) { struct bfq_entity *entity = &bfqq->entity; /* If bfqq is empty, then bfq_bfqq_expire also invokes * bfq_del_bfqq_busy, thereby removing bfqq and its entity * from data structures related to current group. Otherwise we * need to remove bfqq explicitly with bfq_deactivate_bfqq, as * we do below. */ if (bfqq == bfqd->in_service_queue) bfq_bfqq_expire(bfqd, bfqd->in_service_queue, false, BFQQE_PREEMPTED); if (bfq_bfqq_busy(bfqq)) bfq_deactivate_bfqq(bfqd, bfqq, false, false); else if (entity->on_st) bfq_put_idle_entity(bfq_entity_service_tree(entity), entity); bfqg_and_blkg_put(bfqq_group(bfqq)); entity->parent = bfqg->my_entity; entity->sched_data = &bfqg->sched_data; /* pin down bfqg and its associated blkg */ bfqg_and_blkg_get(bfqg); if (bfq_bfqq_busy(bfqq)) { bfq_pos_tree_add_move(bfqd, bfqq); bfq_activate_bfqq(bfqd, bfqq); } if (!bfqd->in_service_queue && !bfqd->rq_in_driver) bfq_schedule_dispatch(bfqd); }

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/** * __bfq_bic_change_cgroup - move @bic to @cgroup. * @bfqd: the queue descriptor. * @bic: the bic to move. * @blkcg: the blk-cgroup to move to. * * Move bic to blkcg, assuming that bfqd->lock is held; which makes * sure that the reference to cgroup is valid across the call (see * comments in bfq_bic_update_cgroup on this issue) * * NOTE: an alternative approach might have been to store the current * cgroup in bfqq and getting a reference to it, reducing the lookup * time here, at the price of slightly more complex code. */
static struct bfq_group *__bfq_bic_change_cgroup(struct bfq_data *bfqd, struct bfq_io_cq *bic, struct blkcg *blkcg) { struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0); struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1); struct bfq_group *bfqg; struct bfq_entity *entity; bfqg = bfq_find_set_group(bfqd, blkcg); if (unlikely(!bfqg)) bfqg = bfqd->root_group; if (async_bfqq) { entity = &async_bfqq->entity; if (entity->sched_data != &bfqg->sched_data) { bic_set_bfqq(bic, NULL, 0); bfq_log_bfqq(bfqd, async_bfqq, "bic_change_group: %p %d", async_bfqq, async_bfqq->ref); bfq_put_queue(async_bfqq); } } if (sync_bfqq) { entity = &sync_bfqq->entity; if (entity->sched_data != &bfqg->sched_data) bfq_bfqq_move(bfqd, sync_bfqq, bfqg); } return bfqg; }

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void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio) { struct bfq_data *bfqd = bic_to_bfqd(bic); struct bfq_group *bfqg = NULL; uint64_t serial_nr; rcu_read_lock(); serial_nr = bio_blkcg(bio)->css.serial_nr; /* * Check whether blkcg has changed. The condition may trigger * spuriously on a newly created cic but there's no harm. */ if (unlikely(!bfqd) || likely(bic->blkcg_serial_nr == serial_nr)) goto out; bfqg = __bfq_bic_change_cgroup(bfqd, bic, bio_blkcg(bio)); /* * Update blkg_path for bfq_log_* functions. We cache this * path, and update it here, for the following * reasons. Operations on blkg objects in blk-cgroup are * protected with the request_queue lock, and not with the * lock that protects the instances of this scheduler * (bfqd->lock). This exposes BFQ to the following sort of * race. * * The blkg_lookup performed in bfq_get_queue, protected * through rcu, may happen to return the address of a copy of * the original blkg. If this is the case, then the * bfqg_and_blkg_get performed in bfq_get_queue, to pin down * the blkg, is useless: it does not prevent blk-cgroup code * from destroying both the original blkg and all objects * directly or indirectly referred by the copy of the * blkg. * * On the bright side, destroy operations on a blkg invoke, as * a first step, hooks of the scheduler associated with the * blkg. And these hooks are executed with bfqd->lock held for * BFQ. As a consequence, for any blkg associated with the * request queue this instance of the scheduler is attached * to, we are guaranteed that such a blkg is not destroyed, and * that all the pointers it contains are consistent, while we * are holding bfqd->lock. A blkg_lookup performed with * bfqd->lock held then returns a fully consistent blkg, which * remains consistent until this lock is held. * * Thanks to the last fact, and to the fact that: (1) bfqg has * been obtained through a blkg_lookup in the above * assignment, and (2) bfqd->lock is being held, here we can * safely use the policy data for the involved blkg (i.e., the * field bfqg->pd) to get to the blkg associated with bfqg, * and then we can safely use any field of blkg. After we * release bfqd->lock, even just getting blkg through this * bfqg may cause dangling references to be traversed, as * bfqg->pd may not exist any more. * * In view of the above facts, here we cache, in the bfqg, any * blkg data we may need for this bic, and for its associated * bfq_queue. As of now, we need to cache only the path of the * blkg, which is used in the bfq_log_* functions. * * Finally, note that bfqg itself needs to be protected from * destruction on the blkg_free of the original blkg (which * invokes bfq_pd_free). We use an additional private * refcounter for bfqg, to let it disappear only after no * bfq_queue refers to it any longer. */ blkg_path(bfqg_to_blkg(bfqg), bfqg->blkg_path, sizeof(bfqg->blkg_path)); bic->blkcg_serial_nr = serial_nr; out: rcu_read_unlock(); }

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Paolo Valente115100.00%2100.00%
Total115100.00%2100.00%

/** * bfq_flush_idle_tree - deactivate any entity on the idle tree of @st. * @st: the service tree being flushed. */
static void bfq_flush_idle_tree(struct bfq_service_tree *st) { struct bfq_entity *entity = st->first_idle; for (; entity ; entity = st->first_idle) __bfq_deactivate_entity(entity, false); }

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Paolo Valente38100.00%1100.00%
Total38100.00%1100.00%

/** * bfq_reparent_leaf_entity - move leaf entity to the root_group. * @bfqd: the device data structure with the root group. * @entity: the entity to move. */
static void bfq_reparent_leaf_entity(struct bfq_data *bfqd, struct bfq_entity *entity) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); bfq_bfqq_move(bfqd, bfqq, bfqd->root_group); }

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Paolo Valente37100.00%1100.00%
Total37100.00%1100.00%

/** * bfq_reparent_active_entities - move to the root group all active * entities. * @bfqd: the device data structure with the root group. * @bfqg: the group to move from. * @st: the service tree with the entities. */
static void bfq_reparent_active_entities(struct bfq_data *bfqd, struct bfq_group *bfqg, struct bfq_service_tree *st) { struct rb_root *active = &st->active; struct bfq_entity *entity = NULL; if (!RB_EMPTY_ROOT(&st->active)) entity = bfq_entity_of(rb_first(active)); for (; entity ; entity = bfq_entity_of(rb_first(active))) bfq_reparent_leaf_entity(bfqd, entity); if (bfqg->sched_data.in_service_entity) bfq_reparent_leaf_entity(bfqd, bfqg->sched_data.in_service_entity); }

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Paolo Valente100100.00%1100.00%
Total100100.00%1100.00%

/** * bfq_pd_offline - deactivate the entity associated with @pd, * and reparent its children entities. * @pd: descriptor of the policy going offline. * * blkio already grabs the queue_lock for us, so no need to use * RCU-based magic */
static void bfq_pd_offline(struct blkg_policy_data *pd) { struct bfq_service_tree *st; struct bfq_group *bfqg = pd_to_bfqg(pd); struct bfq_data *bfqd = bfqg->bfqd; struct bfq_entity *entity = bfqg->