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-rw-r--r--block/blk-cgroup.c2162
1 files changed, 2162 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
new file mode 100644
index 0000000000..4b48c2c440
--- /dev/null
+++ b/block/blk-cgroup.c
@@ -0,0 +1,2162 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Common Block IO controller cgroup interface
+ *
+ * Based on ideas and code from CFQ, CFS and BFQ:
+ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
+ *
+ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
+ * Paolo Valente <paolo.valente@unimore.it>
+ *
+ * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
+ * Nauman Rafique <nauman@google.com>
+ *
+ * For policy-specific per-blkcg data:
+ * Copyright (C) 2015 Paolo Valente <paolo.valente@unimore.it>
+ * Arianna Avanzini <avanzini.arianna@gmail.com>
+ */
+#include <linux/ioprio.h>
+#include <linux/kdev_t.h>
+#include <linux/module.h>
+#include <linux/sched/signal.h>
+#include <linux/err.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/atomic.h>
+#include <linux/ctype.h>
+#include <linux/resume_user_mode.h>
+#include <linux/psi.h>
+#include <linux/part_stat.h>
+#include "blk.h"
+#include "blk-cgroup.h"
+#include "blk-ioprio.h"
+#include "blk-throttle.h"
+
+static void __blkcg_rstat_flush(struct blkcg *blkcg, int cpu);
+
+/*
+ * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
+ * blkcg_pol_register_mutex nests outside of it and synchronizes entire
+ * policy [un]register operations including cgroup file additions /
+ * removals. Putting cgroup file registration outside blkcg_pol_mutex
+ * allows grabbing it from cgroup callbacks.
+ */
+static DEFINE_MUTEX(blkcg_pol_register_mutex);
+static DEFINE_MUTEX(blkcg_pol_mutex);
+
+struct blkcg blkcg_root;
+EXPORT_SYMBOL_GPL(blkcg_root);
+
+struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css;
+EXPORT_SYMBOL_GPL(blkcg_root_css);
+
+static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
+
+static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */
+
+bool blkcg_debug_stats = false;
+
+static DEFINE_RAW_SPINLOCK(blkg_stat_lock);
+
+#define BLKG_DESTROY_BATCH_SIZE 64
+
+/*
+ * Lockless lists for tracking IO stats update
+ *
+ * New IO stats are stored in the percpu iostat_cpu within blkcg_gq (blkg).
+ * There are multiple blkg's (one for each block device) attached to each
+ * blkcg. The rstat code keeps track of which cpu has IO stats updated,
+ * but it doesn't know which blkg has the updated stats. If there are many
+ * block devices in a system, the cost of iterating all the blkg's to flush
+ * out the IO stats can be high. To reduce such overhead, a set of percpu
+ * lockless lists (lhead) per blkcg are used to track the set of recently
+ * updated iostat_cpu's since the last flush. An iostat_cpu will be put
+ * onto the lockless list on the update side [blk_cgroup_bio_start()] if
+ * not there yet and then removed when being flushed [blkcg_rstat_flush()].
+ * References to blkg are gotten and then put back in the process to
+ * protect against blkg removal.
+ *
+ * Return: 0 if successful or -ENOMEM if allocation fails.
+ */
+static int init_blkcg_llists(struct blkcg *blkcg)
+{
+ int cpu;
+
+ blkcg->lhead = alloc_percpu_gfp(struct llist_head, GFP_KERNEL);
+ if (!blkcg->lhead)
+ return -ENOMEM;
+
+ for_each_possible_cpu(cpu)
+ init_llist_head(per_cpu_ptr(blkcg->lhead, cpu));
+ return 0;
+}
+
+/**
+ * blkcg_css - find the current css
+ *
+ * Find the css associated with either the kthread or the current task.
+ * This may return a dying css, so it is up to the caller to use tryget logic
+ * to confirm it is alive and well.
+ */
+static struct cgroup_subsys_state *blkcg_css(void)
+{
+ struct cgroup_subsys_state *css;
+
+ css = kthread_blkcg();
+ if (css)
+ return css;
+ return task_css(current, io_cgrp_id);
+}
+
+static bool blkcg_policy_enabled(struct request_queue *q,
+ const struct blkcg_policy *pol)
+{
+ return pol && test_bit(pol->plid, q->blkcg_pols);
+}
+
+static void blkg_free_workfn(struct work_struct *work)
+{
+ struct blkcg_gq *blkg = container_of(work, struct blkcg_gq,
+ free_work);
+ struct request_queue *q = blkg->q;
+ int i;
+
+ /*
+ * pd_free_fn() can also be called from blkcg_deactivate_policy(),
+ * in order to make sure pd_free_fn() is called in order, the deletion
+ * of the list blkg->q_node is delayed to here from blkg_destroy(), and
+ * blkcg_mutex is used to synchronize blkg_free_workfn() and
+ * blkcg_deactivate_policy().
+ */
+ mutex_lock(&q->blkcg_mutex);
+ for (i = 0; i < BLKCG_MAX_POLS; i++)
+ if (blkg->pd[i])
+ blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
+ if (blkg->parent)
+ blkg_put(blkg->parent);
+ spin_lock_irq(&q->queue_lock);
+ list_del_init(&blkg->q_node);
+ spin_unlock_irq(&q->queue_lock);
+ mutex_unlock(&q->blkcg_mutex);
+
+ blk_put_queue(q);
+ free_percpu(blkg->iostat_cpu);
+ percpu_ref_exit(&blkg->refcnt);
+ kfree(blkg);
+}
+
+/**
+ * blkg_free - free a blkg
+ * @blkg: blkg to free
+ *
+ * Free @blkg which may be partially allocated.
+ */
+static void blkg_free(struct blkcg_gq *blkg)
+{
+ if (!blkg)
+ return;
+
+ /*
+ * Both ->pd_free_fn() and request queue's release handler may
+ * sleep, so free us by scheduling one work func
+ */
+ INIT_WORK(&blkg->free_work, blkg_free_workfn);
+ schedule_work(&blkg->free_work);
+}
+
+static void __blkg_release(struct rcu_head *rcu)
+{
+ struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
+ struct blkcg *blkcg = blkg->blkcg;
+ int cpu;
+
+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
+ WARN_ON(!bio_list_empty(&blkg->async_bios));
+#endif
+ /*
+ * Flush all the non-empty percpu lockless lists before releasing
+ * us, given these stat belongs to us.
+ *
+ * blkg_stat_lock is for serializing blkg stat update
+ */
+ for_each_possible_cpu(cpu)
+ __blkcg_rstat_flush(blkcg, cpu);
+
+ /* release the blkcg and parent blkg refs this blkg has been holding */
+ css_put(&blkg->blkcg->css);
+ blkg_free(blkg);
+}
+
+/*
+ * A group is RCU protected, but having an rcu lock does not mean that one
+ * can access all the fields of blkg and assume these are valid. For
+ * example, don't try to follow throtl_data and request queue links.
+ *
+ * Having a reference to blkg under an rcu allows accesses to only values
+ * local to groups like group stats and group rate limits.
+ */
+static void blkg_release(struct percpu_ref *ref)
+{
+ struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt);
+
+ call_rcu(&blkg->rcu_head, __blkg_release);
+}
+
+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
+static struct workqueue_struct *blkcg_punt_bio_wq;
+
+static void blkg_async_bio_workfn(struct work_struct *work)
+{
+ struct blkcg_gq *blkg = container_of(work, struct blkcg_gq,
+ async_bio_work);
+ struct bio_list bios = BIO_EMPTY_LIST;
+ struct bio *bio;
+ struct blk_plug plug;
+ bool need_plug = false;
+
+ /* as long as there are pending bios, @blkg can't go away */
+ spin_lock(&blkg->async_bio_lock);
+ bio_list_merge(&bios, &blkg->async_bios);
+ bio_list_init(&blkg->async_bios);
+ spin_unlock(&blkg->async_bio_lock);
+
+ /* start plug only when bio_list contains at least 2 bios */
+ if (bios.head && bios.head->bi_next) {
+ need_plug = true;
+ blk_start_plug(&plug);
+ }
+ while ((bio = bio_list_pop(&bios)))
+ submit_bio(bio);
+ if (need_plug)
+ blk_finish_plug(&plug);
+}
+
+/*
+ * When a shared kthread issues a bio for a cgroup, doing so synchronously can
+ * lead to priority inversions as the kthread can be trapped waiting for that
+ * cgroup. Use this helper instead of submit_bio to punt the actual issuing to
+ * a dedicated per-blkcg work item to avoid such priority inversions.
+ */
+void blkcg_punt_bio_submit(struct bio *bio)
+{
+ struct blkcg_gq *blkg = bio->bi_blkg;
+
+ if (blkg->parent) {
+ spin_lock(&blkg->async_bio_lock);
+ bio_list_add(&blkg->async_bios, bio);
+ spin_unlock(&blkg->async_bio_lock);
+ queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work);
+ } else {
+ /* never bounce for the root cgroup */
+ submit_bio(bio);
+ }
+}
+EXPORT_SYMBOL_GPL(blkcg_punt_bio_submit);
+
+static int __init blkcg_punt_bio_init(void)
+{
+ blkcg_punt_bio_wq = alloc_workqueue("blkcg_punt_bio",
+ WQ_MEM_RECLAIM | WQ_FREEZABLE |
+ WQ_UNBOUND | WQ_SYSFS, 0);
+ if (!blkcg_punt_bio_wq)
+ return -ENOMEM;
+ return 0;
+}
+subsys_initcall(blkcg_punt_bio_init);
+#endif /* CONFIG_BLK_CGROUP_PUNT_BIO */
+
+/**
+ * bio_blkcg_css - return the blkcg CSS associated with a bio
+ * @bio: target bio
+ *
+ * This returns the CSS for the blkcg associated with a bio, or %NULL if not
+ * associated. Callers are expected to either handle %NULL or know association
+ * has been done prior to calling this.
+ */
+struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
+{
+ if (!bio || !bio->bi_blkg)
+ return NULL;
+ return &bio->bi_blkg->blkcg->css;
+}
+EXPORT_SYMBOL_GPL(bio_blkcg_css);
+
+/**
+ * blkcg_parent - get the parent of a blkcg
+ * @blkcg: blkcg of interest
+ *
+ * Return the parent blkcg of @blkcg. Can be called anytime.
+ */
+static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
+{
+ return css_to_blkcg(blkcg->css.parent);
+}
+
+/**
+ * blkg_alloc - allocate a blkg
+ * @blkcg: block cgroup the new blkg is associated with
+ * @disk: gendisk the new blkg is associated with
+ * @gfp_mask: allocation mask to use
+ *
+ * Allocate a new blkg assocating @blkcg and @q.
+ */
+static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk,
+ gfp_t gfp_mask)
+{
+ struct blkcg_gq *blkg;
+ int i, cpu;
+
+ /* alloc and init base part */
+ blkg = kzalloc_node(sizeof(*blkg), gfp_mask, disk->queue->node);
+ if (!blkg)
+ return NULL;
+ if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask))
+ goto out_free_blkg;
+ blkg->iostat_cpu = alloc_percpu_gfp(struct blkg_iostat_set, gfp_mask);
+ if (!blkg->iostat_cpu)
+ goto out_exit_refcnt;
+ if (!blk_get_queue(disk->queue))
+ goto out_free_iostat;
+
+ blkg->q = disk->queue;
+ INIT_LIST_HEAD(&blkg->q_node);
+ blkg->blkcg = blkcg;
+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
+ spin_lock_init(&blkg->async_bio_lock);
+ bio_list_init(&blkg->async_bios);
+ INIT_WORK(&blkg->async_bio_work, blkg_async_bio_workfn);
+#endif
+
+ u64_stats_init(&blkg->iostat.sync);
+ for_each_possible_cpu(cpu) {
+ u64_stats_init(&per_cpu_ptr(blkg->iostat_cpu, cpu)->sync);
+ per_cpu_ptr(blkg->iostat_cpu, cpu)->blkg = blkg;
+ }
+
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
+ struct blkcg_policy *pol = blkcg_policy[i];
+ struct blkg_policy_data *pd;
+
+ if (!blkcg_policy_enabled(disk->queue, pol))
+ continue;
+
+ /* alloc per-policy data and attach it to blkg */
+ pd = pol->pd_alloc_fn(disk, blkcg, gfp_mask);
+ if (!pd)
+ goto out_free_pds;
+ blkg->pd[i] = pd;
+ pd->blkg = blkg;
+ pd->plid = i;
+ pd->online = false;
+ }
+
+ return blkg;
+
+out_free_pds:
+ while (--i >= 0)
+ if (blkg->pd[i])
+ blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
+ blk_put_queue(disk->queue);
+out_free_iostat:
+ free_percpu(blkg->iostat_cpu);
+out_exit_refcnt:
+ percpu_ref_exit(&blkg->refcnt);
+out_free_blkg:
+ kfree(blkg);
+ return NULL;
+}
+
+/*
+ * If @new_blkg is %NULL, this function tries to allocate a new one as
+ * necessary using %GFP_NOWAIT. @new_blkg is always consumed on return.
+ */
+static struct blkcg_gq *blkg_create(struct blkcg *blkcg, struct gendisk *disk,
+ struct blkcg_gq *new_blkg)
+{
+ struct blkcg_gq *blkg;
+ int i, ret;
+
+ lockdep_assert_held(&disk->queue->queue_lock);
+
+ /* request_queue is dying, do not create/recreate a blkg */
+ if (blk_queue_dying(disk->queue)) {
+ ret = -ENODEV;
+ goto err_free_blkg;
+ }
+
+ /* blkg holds a reference to blkcg */
+ if (!css_tryget_online(&blkcg->css)) {
+ ret = -ENODEV;
+ goto err_free_blkg;
+ }
+
+ /* allocate */
+ if (!new_blkg) {
+ new_blkg = blkg_alloc(blkcg, disk, GFP_NOWAIT | __GFP_NOWARN);
+ if (unlikely(!new_blkg)) {
+ ret = -ENOMEM;
+ goto err_put_css;
+ }
+ }
+ blkg = new_blkg;
+
+ /* link parent */
+ if (blkcg_parent(blkcg)) {
+ blkg->parent = blkg_lookup(blkcg_parent(blkcg), disk->queue);
+ if (WARN_ON_ONCE(!blkg->parent)) {
+ ret = -ENODEV;
+ goto err_put_css;
+ }
+ blkg_get(blkg->parent);
+ }
+
+ /* invoke per-policy init */
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
+ struct blkcg_policy *pol = blkcg_policy[i];
+
+ if (blkg->pd[i] && pol->pd_init_fn)
+ pol->pd_init_fn(blkg->pd[i]);
+ }
+
+ /* insert */
+ spin_lock(&blkcg->lock);
+ ret = radix_tree_insert(&blkcg->blkg_tree, disk->queue->id, blkg);
+ if (likely(!ret)) {
+ hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
+ list_add(&blkg->q_node, &disk->queue->blkg_list);
+
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
+ struct blkcg_policy *pol = blkcg_policy[i];
+
+ if (blkg->pd[i]) {
+ if (pol->pd_online_fn)
+ pol->pd_online_fn(blkg->pd[i]);
+ blkg->pd[i]->online = true;
+ }
+ }
+ }
+ blkg->online = true;
+ spin_unlock(&blkcg->lock);
+
+ if (!ret)
+ return blkg;
+
+ /* @blkg failed fully initialized, use the usual release path */
+ blkg_put(blkg);
+ return ERR_PTR(ret);
+
+err_put_css:
+ css_put(&blkcg->css);
+err_free_blkg:
+ if (new_blkg)
+ blkg_free(new_blkg);
+ return ERR_PTR(ret);
+}
+
+/**
+ * blkg_lookup_create - lookup blkg, try to create one if not there
+ * @blkcg: blkcg of interest
+ * @disk: gendisk of interest
+ *
+ * Lookup blkg for the @blkcg - @disk pair. If it doesn't exist, try to
+ * create one. blkg creation is performed recursively from blkcg_root such
+ * that all non-root blkg's have access to the parent blkg. This function
+ * should be called under RCU read lock and takes @disk->queue->queue_lock.
+ *
+ * Returns the blkg or the closest blkg if blkg_create() fails as it walks
+ * down from root.
+ */
+static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
+ struct gendisk *disk)
+{
+ struct request_queue *q = disk->queue;
+ struct blkcg_gq *blkg;
+ unsigned long flags;
+
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
+ blkg = blkg_lookup(blkcg, q);
+ if (blkg)
+ return blkg;
+
+ spin_lock_irqsave(&q->queue_lock, flags);
+ blkg = blkg_lookup(blkcg, q);
+ if (blkg) {
+ if (blkcg != &blkcg_root &&
+ blkg != rcu_dereference(blkcg->blkg_hint))
+ rcu_assign_pointer(blkcg->blkg_hint, blkg);
+ goto found;
+ }
+
+ /*
+ * Create blkgs walking down from blkcg_root to @blkcg, so that all
+ * non-root blkgs have access to their parents. Returns the closest
+ * blkg to the intended blkg should blkg_create() fail.
+ */
+ while (true) {
+ struct blkcg *pos = blkcg;
+ struct blkcg *parent = blkcg_parent(blkcg);
+ struct blkcg_gq *ret_blkg = q->root_blkg;
+
+ while (parent) {
+ blkg = blkg_lookup(parent, q);
+ if (blkg) {
+ /* remember closest blkg */
+ ret_blkg = blkg;
+ break;
+ }
+ pos = parent;
+ parent = blkcg_parent(parent);
+ }
+
+ blkg = blkg_create(pos, disk, NULL);
+ if (IS_ERR(blkg)) {
+ blkg = ret_blkg;
+ break;
+ }
+ if (pos == blkcg)
+ break;
+ }
+
+found:
+ spin_unlock_irqrestore(&q->queue_lock, flags);
+ return blkg;
+}
+
+static void blkg_destroy(struct blkcg_gq *blkg)
+{
+ struct blkcg *blkcg = blkg->blkcg;
+ int i;
+
+ lockdep_assert_held(&blkg->q->queue_lock);
+ lockdep_assert_held(&blkcg->lock);
+
+ /*
+ * blkg stays on the queue list until blkg_free_workfn(), see details in
+ * blkg_free_workfn(), hence this function can be called from
+ * blkcg_destroy_blkgs() first and again from blkg_destroy_all() before
+ * blkg_free_workfn().
+ */
+ if (hlist_unhashed(&blkg->blkcg_node))
+ return;
+
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
+ struct blkcg_policy *pol = blkcg_policy[i];
+
+ if (blkg->pd[i] && blkg->pd[i]->online) {
+ blkg->pd[i]->online = false;
+ if (pol->pd_offline_fn)
+ pol->pd_offline_fn(blkg->pd[i]);
+ }
+ }
+
+ blkg->online = false;
+
+ radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
+ hlist_del_init_rcu(&blkg->blkcg_node);
+
+ /*
+ * Both setting lookup hint to and clearing it from @blkg are done
+ * under queue_lock. If it's not pointing to @blkg now, it never
+ * will. Hint assignment itself can race safely.
+ */
+ if (rcu_access_pointer(blkcg->blkg_hint) == blkg)
+ rcu_assign_pointer(blkcg->blkg_hint, NULL);
+
+ /*
+ * Put the reference taken at the time of creation so that when all
+ * queues are gone, group can be destroyed.
+ */
+ percpu_ref_kill(&blkg->refcnt);
+}
+
+static void blkg_destroy_all(struct gendisk *disk)
+{
+ struct request_queue *q = disk->queue;
+ struct blkcg_gq *blkg, *n;
+ int count = BLKG_DESTROY_BATCH_SIZE;
+ int i;
+
+restart:
+ spin_lock_irq(&q->queue_lock);
+ list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
+ struct blkcg *blkcg = blkg->blkcg;
+
+ if (hlist_unhashed(&blkg->blkcg_node))
+ continue;
+
+ spin_lock(&blkcg->lock);
+ blkg_destroy(blkg);
+ spin_unlock(&blkcg->lock);
+
+ /*
+ * in order to avoid holding the spin lock for too long, release
+ * it when a batch of blkgs are destroyed.
+ */
+ if (!(--count)) {
+ count = BLKG_DESTROY_BATCH_SIZE;
+ spin_unlock_irq(&q->queue_lock);
+ cond_resched();
+ goto restart;
+ }
+ }
+
+ /*
+ * Mark policy deactivated since policy offline has been done, and
+ * the free is scheduled, so future blkcg_deactivate_policy() can
+ * be bypassed
+ */
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
+ struct blkcg_policy *pol = blkcg_policy[i];
+
+ if (pol)
+ __clear_bit(pol->plid, q->blkcg_pols);
+ }
+
+ q->root_blkg = NULL;
+ spin_unlock_irq(&q->queue_lock);
+}
+
+static int blkcg_reset_stats(struct cgroup_subsys_state *css,
+ struct cftype *cftype, u64 val)
+{
+ struct blkcg *blkcg = css_to_blkcg(css);
+ struct blkcg_gq *blkg;
+ int i, cpu;
+
+ mutex_lock(&blkcg_pol_mutex);
+ spin_lock_irq(&blkcg->lock);
+
+ /*
+ * Note that stat reset is racy - it doesn't synchronize against
+ * stat updates. This is a debug feature which shouldn't exist
+ * anyway. If you get hit by a race, retry.
+ */
+ hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
+ for_each_possible_cpu(cpu) {
+ struct blkg_iostat_set *bis =
+ per_cpu_ptr(blkg->iostat_cpu, cpu);
+ memset(bis, 0, sizeof(*bis));
+
+ /* Re-initialize the cleared blkg_iostat_set */
+ u64_stats_init(&bis->sync);
+ bis->blkg = blkg;
+ }
+ memset(&blkg->iostat, 0, sizeof(blkg->iostat));
+ u64_stats_init(&blkg->iostat.sync);
+
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
+ struct blkcg_policy *pol = blkcg_policy[i];
+
+ if (blkg->pd[i] && pol->pd_reset_stats_fn)
+ pol->pd_reset_stats_fn(blkg->pd[i]);
+ }
+ }
+
+ spin_unlock_irq(&blkcg->lock);
+ mutex_unlock(&blkcg_pol_mutex);
+ return 0;
+}
+
+const char *blkg_dev_name(struct blkcg_gq *blkg)
+{
+ if (!blkg->q->disk)
+ return NULL;
+ return bdi_dev_name(blkg->q->disk->bdi);
+}
+
+/**
+ * blkcg_print_blkgs - helper for printing per-blkg data
+ * @sf: seq_file to print to
+ * @blkcg: blkcg of interest
+ * @prfill: fill function to print out a blkg
+ * @pol: policy in question
+ * @data: data to be passed to @prfill
+ * @show_total: to print out sum of prfill return values or not
+ *
+ * This function invokes @prfill on each blkg of @blkcg if pd for the
+ * policy specified by @pol exists. @prfill is invoked with @sf, the
+ * policy data and @data and the matching queue lock held. If @show_total
+ * is %true, the sum of the return values from @prfill is printed with
+ * "Total" label at the end.
+ *
+ * This is to be used to construct print functions for
+ * cftype->read_seq_string method.
+ */
+void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
+ u64 (*prfill)(struct seq_file *,
+ struct blkg_policy_data *, int),
+ const struct blkcg_policy *pol, int data,
+ bool show_total)
+{
+ struct blkcg_gq *blkg;
+ u64 total = 0;
+
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
+ spin_lock_irq(&blkg->q->queue_lock);
+ if (blkcg_policy_enabled(blkg->q, pol))
+ total += prfill(sf, blkg->pd[pol->plid], data);
+ spin_unlock_irq(&blkg->q->queue_lock);
+ }
+ rcu_read_unlock();
+
+ if (show_total)
+ seq_printf(sf, "Total %llu\n", (unsigned long long)total);
+}
+EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
+
+/**
+ * __blkg_prfill_u64 - prfill helper for a single u64 value
+ * @sf: seq_file to print to
+ * @pd: policy private data of interest
+ * @v: value to print
+ *
+ * Print @v to @sf for the device associated with @pd.
+ */
+u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
+{
+ const char *dname = blkg_dev_name(pd->blkg);
+
+ if (!dname)
+ return 0;
+
+ seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
+ return v;
+}
+EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
+
+/**
+ * blkg_conf_init - initialize a blkg_conf_ctx
+ * @ctx: blkg_conf_ctx to initialize
+ * @input: input string
+ *
+ * Initialize @ctx which can be used to parse blkg config input string @input.
+ * Once initialized, @ctx can be used with blkg_conf_open_bdev() and
+ * blkg_conf_prep(), and must be cleaned up with blkg_conf_exit().
+ */
+void blkg_conf_init(struct blkg_conf_ctx *ctx, char *input)
+{
+ *ctx = (struct blkg_conf_ctx){ .input = input };
+}
+EXPORT_SYMBOL_GPL(blkg_conf_init);
+
+/**
+ * blkg_conf_open_bdev - parse and open bdev for per-blkg config update
+ * @ctx: blkg_conf_ctx initialized with blkg_conf_init()
+ *
+ * Parse the device node prefix part, MAJ:MIN, of per-blkg config update from
+ * @ctx->input and get and store the matching bdev in @ctx->bdev. @ctx->body is
+ * set to point past the device node prefix.
+ *
+ * This function may be called multiple times on @ctx and the extra calls become
+ * NOOPs. blkg_conf_prep() implicitly calls this function. Use this function
+ * explicitly if bdev access is needed without resolving the blkcg / policy part
+ * of @ctx->input. Returns -errno on error.
+ */
+int blkg_conf_open_bdev(struct blkg_conf_ctx *ctx)
+{
+ char *input = ctx->input;
+ unsigned int major, minor;
+ struct block_device *bdev;
+ int key_len;
+
+ if (ctx->bdev)
+ return 0;
+
+ if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2)
+ return -EINVAL;
+
+ input += key_len;
+ if (!isspace(*input))
+ return -EINVAL;
+ input = skip_spaces(input);
+
+ bdev = blkdev_get_no_open(MKDEV(major, minor));
+ if (!bdev)
+ return -ENODEV;
+ if (bdev_is_partition(bdev)) {
+ blkdev_put_no_open(bdev);
+ return -ENODEV;
+ }
+
+ mutex_lock(&bdev->bd_queue->rq_qos_mutex);
+ if (!disk_live(bdev->bd_disk)) {
+ blkdev_put_no_open(bdev);
+ mutex_unlock(&bdev->bd_queue->rq_qos_mutex);
+ return -ENODEV;
+ }
+
+ ctx->body = input;
+ ctx->bdev = bdev;
+ return 0;
+}
+
+/**
+ * blkg_conf_prep - parse and prepare for per-blkg config update
+ * @blkcg: target block cgroup
+ * @pol: target policy
+ * @ctx: blkg_conf_ctx initialized with blkg_conf_init()
+ *
+ * Parse per-blkg config update from @ctx->input and initialize @ctx
+ * accordingly. On success, @ctx->body points to the part of @ctx->input
+ * following MAJ:MIN, @ctx->bdev points to the target block device and
+ * @ctx->blkg to the blkg being configured.
+ *
+ * blkg_conf_open_bdev() may be called on @ctx beforehand. On success, this
+ * function returns with queue lock held and must be followed by
+ * blkg_conf_exit().
+ */
+int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
+ struct blkg_conf_ctx *ctx)
+ __acquires(&bdev->bd_queue->queue_lock)
+{
+ struct gendisk *disk;
+ struct request_queue *q;
+ struct blkcg_gq *blkg;
+ int ret;
+
+ ret = blkg_conf_open_bdev(ctx);
+ if (ret)
+ return ret;
+
+ disk = ctx->bdev->bd_disk;
+ q = disk->queue;
+
+ /*
+ * blkcg_deactivate_policy() requires queue to be frozen, we can grab
+ * q_usage_counter to prevent concurrent with blkcg_deactivate_policy().
+ */
+ ret = blk_queue_enter(q, 0);
+ if (ret)
+ goto fail;
+
+ spin_lock_irq(&q->queue_lock);
+
+ if (!blkcg_policy_enabled(q, pol)) {
+ ret = -EOPNOTSUPP;
+ goto fail_unlock;
+ }
+
+ blkg = blkg_lookup(blkcg, q);
+ if (blkg)
+ goto success;
+
+ /*
+ * Create blkgs walking down from blkcg_root to @blkcg, so that all
+ * non-root blkgs have access to their parents.
+ */
+ while (true) {
+ struct blkcg *pos = blkcg;
+ struct blkcg *parent;
+ struct blkcg_gq *new_blkg;
+
+ parent = blkcg_parent(blkcg);
+ while (parent && !blkg_lookup(parent, q)) {
+ pos = parent;
+ parent = blkcg_parent(parent);
+ }
+
+ /* Drop locks to do new blkg allocation with GFP_KERNEL. */
+ spin_unlock_irq(&q->queue_lock);
+
+ new_blkg = blkg_alloc(pos, disk, GFP_KERNEL);
+ if (unlikely(!new_blkg)) {
+ ret = -ENOMEM;
+ goto fail_exit_queue;
+ }
+
+ if (radix_tree_preload(GFP_KERNEL)) {
+ blkg_free(new_blkg);
+ ret = -ENOMEM;
+ goto fail_exit_queue;
+ }
+
+ spin_lock_irq(&q->queue_lock);
+
+ if (!blkcg_policy_enabled(q, pol)) {
+ blkg_free(new_blkg);
+ ret = -EOPNOTSUPP;
+ goto fail_preloaded;
+ }
+
+ blkg = blkg_lookup(pos, q);
+ if (blkg) {
+ blkg_free(new_blkg);
+ } else {
+ blkg = blkg_create(pos, disk, new_blkg);
+ if (IS_ERR(blkg)) {
+ ret = PTR_ERR(blkg);
+ goto fail_preloaded;
+ }
+ }
+
+ radix_tree_preload_end();
+
+ if (pos == blkcg)
+ goto success;
+ }
+success:
+ blk_queue_exit(q);
+ ctx->blkg = blkg;
+ return 0;
+
+fail_preloaded:
+ radix_tree_preload_end();
+fail_unlock:
+ spin_unlock_irq(&q->queue_lock);
+fail_exit_queue:
+ blk_queue_exit(q);
+fail:
+ /*
+ * If queue was bypassing, we should retry. Do so after a
+ * short msleep(). It isn't strictly necessary but queue
+ * can be bypassing for some time and it's always nice to
+ * avoid busy looping.
+ */
+ if (ret == -EBUSY) {
+ msleep(10);
+ ret = restart_syscall();
+ }
+ return ret;
+}
+EXPORT_SYMBOL_GPL(blkg_conf_prep);
+
+/**
+ * blkg_conf_exit - clean up per-blkg config update
+ * @ctx: blkg_conf_ctx initialized with blkg_conf_init()
+ *
+ * Clean up after per-blkg config update. This function must be called on all
+ * blkg_conf_ctx's initialized with blkg_conf_init().
+ */
+void blkg_conf_exit(struct blkg_conf_ctx *ctx)
+ __releases(&ctx->bdev->bd_queue->queue_lock)
+ __releases(&ctx->bdev->bd_queue->rq_qos_mutex)
+{
+ if (ctx->blkg) {
+ spin_unlock_irq(&bdev_get_queue(ctx->bdev)->queue_lock);
+ ctx->blkg = NULL;
+ }
+
+ if (ctx->bdev) {
+ mutex_unlock(&ctx->bdev->bd_queue->rq_qos_mutex);
+ blkdev_put_no_open(ctx->bdev);
+ ctx->body = NULL;
+ ctx->bdev = NULL;
+ }
+}
+EXPORT_SYMBOL_GPL(blkg_conf_exit);
+
+static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src)
+{
+ int i;
+
+ for (i = 0; i < BLKG_IOSTAT_NR; i++) {
+ dst->bytes[i] = src->bytes[i];
+ dst->ios[i] = src->ios[i];
+ }
+}
+
+static void blkg_iostat_add(struct blkg_iostat *dst, struct blkg_iostat *src)
+{
+ int i;
+
+ for (i = 0; i < BLKG_IOSTAT_NR; i++) {
+ dst->bytes[i] += src->bytes[i];
+ dst->ios[i] += src->ios[i];
+ }
+}
+
+static void blkg_iostat_sub(struct blkg_iostat *dst, struct blkg_iostat *src)
+{
+ int i;
+
+ for (i = 0; i < BLKG_IOSTAT_NR; i++) {
+ dst->bytes[i] -= src->bytes[i];
+ dst->ios[i] -= src->ios[i];
+ }
+}
+
+static void blkcg_iostat_update(struct blkcg_gq *blkg, struct blkg_iostat *cur,
+ struct blkg_iostat *last)
+{
+ struct blkg_iostat delta;
+ unsigned long flags;
+
+ /* propagate percpu delta to global */
+ flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
+ blkg_iostat_set(&delta, cur);
+ blkg_iostat_sub(&delta, last);
+ blkg_iostat_add(&blkg->iostat.cur, &delta);
+ blkg_iostat_add(last, &delta);
+ u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
+}
+
+static void __blkcg_rstat_flush(struct blkcg *blkcg, int cpu)
+{
+ struct llist_head *lhead = per_cpu_ptr(blkcg->lhead, cpu);
+ struct llist_node *lnode;
+ struct blkg_iostat_set *bisc, *next_bisc;
+ unsigned long flags;
+
+ rcu_read_lock();
+
+ lnode = llist_del_all(lhead);
+ if (!lnode)
+ goto out;
+
+ /*
+ * For covering concurrent parent blkg update from blkg_release().
+ *
+ * When flushing from cgroup, cgroup_rstat_lock is always held, so
+ * this lock won't cause contention most of time.
+ */
+ raw_spin_lock_irqsave(&blkg_stat_lock, flags);
+
+ /*
+ * Iterate only the iostat_cpu's queued in the lockless list.
+ */
+ llist_for_each_entry_safe(bisc, next_bisc, lnode, lnode) {
+ struct blkcg_gq *blkg = bisc->blkg;
+ struct blkcg_gq *parent = blkg->parent;
+ struct blkg_iostat cur;
+ unsigned int seq;
+
+ WRITE_ONCE(bisc->lqueued, false);
+
+ /* fetch the current per-cpu values */
+ do {
+ seq = u64_stats_fetch_begin(&bisc->sync);
+ blkg_iostat_set(&cur, &bisc->cur);
+ } while (u64_stats_fetch_retry(&bisc->sync, seq));
+
+ blkcg_iostat_update(blkg, &cur, &bisc->last);
+
+ /* propagate global delta to parent (unless that's root) */
+ if (parent && parent->parent)
+ blkcg_iostat_update(parent, &blkg->iostat.cur,
+ &blkg->iostat.last);
+ }
+ raw_spin_unlock_irqrestore(&blkg_stat_lock, flags);
+out:
+ rcu_read_unlock();
+}
+
+static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
+{
+ /* Root-level stats are sourced from system-wide IO stats */
+ if (cgroup_parent(css->cgroup))
+ __blkcg_rstat_flush(css_to_blkcg(css), cpu);
+}
+
+/*
+ * We source root cgroup stats from the system-wide stats to avoid
+ * tracking the same information twice and incurring overhead when no
+ * cgroups are defined. For that reason, cgroup_rstat_flush in
+ * blkcg_print_stat does not actually fill out the iostat in the root
+ * cgroup's blkcg_gq.
+ *
+ * However, we would like to re-use the printing code between the root and
+ * non-root cgroups to the extent possible. For that reason, we simulate
+ * flushing the root cgroup's stats by explicitly filling in the iostat
+ * with disk level statistics.
+ */
+static void blkcg_fill_root_iostats(void)
+{
+ struct class_dev_iter iter;
+ struct device *dev;
+
+ class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
+ while ((dev = class_dev_iter_next(&iter))) {
+ struct block_device *bdev = dev_to_bdev(dev);
+ struct blkcg_gq *blkg = bdev->bd_disk->queue->root_blkg;
+ struct blkg_iostat tmp;
+ int cpu;
+ unsigned long flags;
+
+ memset(&tmp, 0, sizeof(tmp));
+ for_each_possible_cpu(cpu) {
+ struct disk_stats *cpu_dkstats;
+
+ cpu_dkstats = per_cpu_ptr(bdev->bd_stats, cpu);
+ tmp.ios[BLKG_IOSTAT_READ] +=
+ cpu_dkstats->ios[STAT_READ];
+ tmp.ios[BLKG_IOSTAT_WRITE] +=
+ cpu_dkstats->ios[STAT_WRITE];
+ tmp.ios[BLKG_IOSTAT_DISCARD] +=
+ cpu_dkstats->ios[STAT_DISCARD];
+ // convert sectors to bytes
+ tmp.bytes[BLKG_IOSTAT_READ] +=
+ cpu_dkstats->sectors[STAT_READ] << 9;
+ tmp.bytes[BLKG_IOSTAT_WRITE] +=
+ cpu_dkstats->sectors[STAT_WRITE] << 9;
+ tmp.bytes[BLKG_IOSTAT_DISCARD] +=
+ cpu_dkstats->sectors[STAT_DISCARD] << 9;
+ }
+
+ flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
+ blkg_iostat_set(&blkg->iostat.cur, &tmp);
+ u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
+ }
+}
+
+static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
+{
+ struct blkg_iostat_set *bis = &blkg->iostat;
+ u64 rbytes, wbytes, rios, wios, dbytes, dios;
+ const char *dname;
+ unsigned seq;
+ int i;
+
+ if (!blkg->online)
+ return;
+
+ dname = blkg_dev_name(blkg);
+ if (!dname)
+ return;
+
+ seq_printf(s, "%s ", dname);
+
+ do {
+ seq = u64_stats_fetch_begin(&bis->sync);
+
+ rbytes = bis->cur.bytes[BLKG_IOSTAT_READ];
+ wbytes = bis->cur.bytes[BLKG_IOSTAT_WRITE];
+ dbytes = bis->cur.bytes[BLKG_IOSTAT_DISCARD];
+ rios = bis->cur.ios[BLKG_IOSTAT_READ];
+ wios = bis->cur.ios[BLKG_IOSTAT_WRITE];
+ dios = bis->cur.ios[BLKG_IOSTAT_DISCARD];
+ } while (u64_stats_fetch_retry(&bis->sync, seq));
+
+ if (rbytes || wbytes || rios || wios) {
+ seq_printf(s, "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
+ rbytes, wbytes, rios, wios,
+ dbytes, dios);
+ }
+
+ if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) {
+ seq_printf(s, " use_delay=%d delay_nsec=%llu",
+ atomic_read(&blkg->use_delay),
+ atomic64_read(&blkg->delay_nsec));
+ }
+
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
+ struct blkcg_policy *pol = blkcg_policy[i];
+
+ if (!blkg->pd[i] || !pol->pd_stat_fn)
+ continue;
+
+ pol->pd_stat_fn(blkg->pd[i], s);
+ }
+
+ seq_puts(s, "\n");
+}
+
+static int blkcg_print_stat(struct seq_file *sf, void *v)
+{
+ struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
+ struct blkcg_gq *blkg;
+
+ if (!seq_css(sf)->parent)
+ blkcg_fill_root_iostats();
+ else
+ cgroup_rstat_flush(blkcg->css.cgroup);
+
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
+ spin_lock_irq(&blkg->q->queue_lock);
+ blkcg_print_one_stat(blkg, sf);
+ spin_unlock_irq(&blkg->q->queue_lock);
+ }
+ rcu_read_unlock();
+ return 0;
+}
+
+static struct cftype blkcg_files[] = {
+ {
+ .name = "stat",
+ .seq_show = blkcg_print_stat,
+ },
+ { } /* terminate */
+};
+
+static struct cftype blkcg_legacy_files[] = {
+ {
+ .name = "reset_stats",
+ .write_u64 = blkcg_reset_stats,
+ },
+ { } /* terminate */
+};
+
+#ifdef CONFIG_CGROUP_WRITEBACK
+struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css)
+{
+ return &css_to_blkcg(css)->cgwb_list;
+}
+#endif
+
+/*
+ * blkcg destruction is a three-stage process.
+ *
+ * 1. Destruction starts. The blkcg_css_offline() callback is invoked
+ * which offlines writeback. Here we tie the next stage of blkg destruction
+ * to the completion of writeback associated with the blkcg. This lets us
+ * avoid punting potentially large amounts of outstanding writeback to root
+ * while maintaining any ongoing policies. The next stage is triggered when
+ * the nr_cgwbs count goes to zero.
+ *
+ * 2. When the nr_cgwbs count goes to zero, blkcg_destroy_blkgs() is called
+ * and handles the destruction of blkgs. Here the css reference held by
+ * the blkg is put back eventually allowing blkcg_css_free() to be called.
+ * This work may occur in cgwb_release_workfn() on the cgwb_release
+ * workqueue. Any submitted ios that fail to get the blkg ref will be
+ * punted to the root_blkg.
+ *
+ * 3. Once the blkcg ref count goes to zero, blkcg_css_free() is called.
+ * This finally frees the blkcg.
+ */
+
+/**
+ * blkcg_destroy_blkgs - responsible for shooting down blkgs
+ * @blkcg: blkcg of interest
+ *
+ * blkgs should be removed while holding both q and blkcg locks. As blkcg lock
+ * is nested inside q lock, this function performs reverse double lock dancing.
+ * Destroying the blkgs releases the reference held on the blkcg's css allowing
+ * blkcg_css_free to eventually be called.
+ *
+ * This is the blkcg counterpart of ioc_release_fn().
+ */
+static void blkcg_destroy_blkgs(struct blkcg *blkcg)
+{
+ might_sleep();
+
+ spin_lock_irq(&blkcg->lock);
+
+ while (!hlist_empty(&blkcg->blkg_list)) {
+ struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
+ struct blkcg_gq, blkcg_node);
+ struct request_queue *q = blkg->q;
+
+ if (need_resched() || !spin_trylock(&q->queue_lock)) {
+ /*
+ * Given that the system can accumulate a huge number
+ * of blkgs in pathological cases, check to see if we
+ * need to rescheduling to avoid softlockup.
+ */
+ spin_unlock_irq(&blkcg->lock);
+ cond_resched();
+ spin_lock_irq(&blkcg->lock);
+ continue;
+ }
+
+ blkg_destroy(blkg);
+ spin_unlock(&q->queue_lock);
+ }
+
+ spin_unlock_irq(&blkcg->lock);
+}
+
+/**
+ * blkcg_pin_online - pin online state
+ * @blkcg_css: blkcg of interest
+ *
+ * While pinned, a blkcg is kept online. This is primarily used to
+ * impedance-match blkg and cgwb lifetimes so that blkg doesn't go offline
+ * while an associated cgwb is still active.
+ */
+void blkcg_pin_online(struct cgroup_subsys_state *blkcg_css)
+{
+ refcount_inc(&css_to_blkcg(blkcg_css)->online_pin);
+}
+
+/**
+ * blkcg_unpin_online - unpin online state
+ * @blkcg_css: blkcg of interest
+ *
+ * This is primarily used to impedance-match blkg and cgwb lifetimes so
+ * that blkg doesn't go offline while an associated cgwb is still active.
+ * When this count goes to zero, all active cgwbs have finished so the
+ * blkcg can continue destruction by calling blkcg_destroy_blkgs().
+ */
+void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css)
+{
+ struct blkcg *blkcg = css_to_blkcg(blkcg_css);
+
+ do {
+ if (!refcount_dec_and_test(&blkcg->online_pin))
+ break;
+ blkcg_destroy_blkgs(blkcg);
+ blkcg = blkcg_parent(blkcg);
+ } while (blkcg);
+}
+
+/**
+ * blkcg_css_offline - cgroup css_offline callback
+ * @css: css of interest
+ *
+ * This function is called when @css is about to go away. Here the cgwbs are
+ * offlined first and only once writeback associated with the blkcg has
+ * finished do we start step 2 (see above).
+ */
+static void blkcg_css_offline(struct cgroup_subsys_state *css)
+{
+ /* this prevents anyone from attaching or migrating to this blkcg */
+ wb_blkcg_offline(css);
+
+ /* put the base online pin allowing step 2 to be triggered */
+ blkcg_unpin_online(css);
+}
+
+static void blkcg_css_free(struct cgroup_subsys_state *css)
+{
+ struct blkcg *blkcg = css_to_blkcg(css);
+ int i;
+
+ mutex_lock(&blkcg_pol_mutex);
+
+ list_del(&blkcg->all_blkcgs_node);
+
+ for (i = 0; i < BLKCG_MAX_POLS; i++)
+ if (blkcg->cpd[i])
+ blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
+
+ mutex_unlock(&blkcg_pol_mutex);
+
+ free_percpu(blkcg->lhead);
+ kfree(blkcg);
+}
+
+static struct cgroup_subsys_state *
+blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
+{
+ struct blkcg *blkcg;
+ int i;
+
+ mutex_lock(&blkcg_pol_mutex);
+
+ if (!parent_css) {
+ blkcg = &blkcg_root;
+ } else {
+ blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
+ if (!blkcg)
+ goto unlock;
+ }
+
+ if (init_blkcg_llists(blkcg))
+ goto free_blkcg;
+
+ for (i = 0; i < BLKCG_MAX_POLS ; i++) {
+ struct blkcg_policy *pol = blkcg_policy[i];
+ struct blkcg_policy_data *cpd;
+
+ /*
+ * If the policy hasn't been attached yet, wait for it
+ * to be attached before doing anything else. Otherwise,
+ * check if the policy requires any specific per-cgroup
+ * data: if it does, allocate and initialize it.
+ */
+ if (!pol || !pol->cpd_alloc_fn)
+ continue;
+
+ cpd = pol->cpd_alloc_fn(GFP_KERNEL);
+ if (!cpd)
+ goto free_pd_blkcg;
+
+ blkcg->cpd[i] = cpd;
+ cpd->blkcg = blkcg;
+ cpd->plid = i;
+ }
+
+ spin_lock_init(&blkcg->lock);
+ refcount_set(&blkcg->online_pin, 1);
+ INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN);
+ INIT_HLIST_HEAD(&blkcg->blkg_list);
+#ifdef CONFIG_CGROUP_WRITEBACK
+ INIT_LIST_HEAD(&blkcg->cgwb_list);
+#endif
+ list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs);
+
+ mutex_unlock(&blkcg_pol_mutex);
+ return &blkcg->css;
+
+free_pd_blkcg:
+ for (i--; i >= 0; i--)
+ if (blkcg->cpd[i])
+ blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
+ free_percpu(blkcg->lhead);
+free_blkcg:
+ if (blkcg != &blkcg_root)
+ kfree(blkcg);
+unlock:
+ mutex_unlock(&blkcg_pol_mutex);
+ return ERR_PTR(-ENOMEM);
+}
+
+static int blkcg_css_online(struct cgroup_subsys_state *css)
+{
+ struct blkcg *parent = blkcg_parent(css_to_blkcg(css));
+
+ /*
+ * blkcg_pin_online() is used to delay blkcg offline so that blkgs
+ * don't go offline while cgwbs are still active on them. Pin the
+ * parent so that offline always happens towards the root.
+ */
+ if (parent)
+ blkcg_pin_online(&parent->css);
+ return 0;
+}
+
+int blkcg_init_disk(struct gendisk *disk)
+{
+ struct request_queue *q = disk->queue;
+ struct blkcg_gq *new_blkg, *blkg;
+ bool preloaded;
+ int ret;
+
+ INIT_LIST_HEAD(&q->blkg_list);
+ mutex_init(&q->blkcg_mutex);
+
+ new_blkg = blkg_alloc(&blkcg_root, disk, GFP_KERNEL);
+ if (!new_blkg)
+ return -ENOMEM;
+
+ preloaded = !radix_tree_preload(GFP_KERNEL);
+
+ /* Make sure the root blkg exists. */
+ /* spin_lock_irq can serve as RCU read-side critical section. */
+ spin_lock_irq(&q->queue_lock);
+ blkg = blkg_create(&blkcg_root, disk, new_blkg);
+ if (IS_ERR(blkg))
+ goto err_unlock;
+ q->root_blkg = blkg;
+ spin_unlock_irq(&q->queue_lock);
+
+ if (preloaded)
+ radix_tree_preload_end();
+
+ ret = blk_ioprio_init(disk);
+ if (ret)
+ goto err_destroy_all;
+
+ ret = blk_throtl_init(disk);
+ if (ret)
+ goto err_ioprio_exit;
+
+ return 0;
+
+err_ioprio_exit:
+ blk_ioprio_exit(disk);
+err_destroy_all:
+ blkg_destroy_all(disk);
+ return ret;
+err_unlock:
+ spin_unlock_irq(&q->queue_lock);
+ if (preloaded)
+ radix_tree_preload_end();
+ return PTR_ERR(blkg);
+}
+
+void blkcg_exit_disk(struct gendisk *disk)
+{
+ blkg_destroy_all(disk);
+ blk_throtl_exit(disk);
+}
+
+static void blkcg_exit(struct task_struct *tsk)
+{
+ if (tsk->throttle_disk)
+ put_disk(tsk->throttle_disk);
+ tsk->throttle_disk = NULL;
+}
+
+struct cgroup_subsys io_cgrp_subsys = {
+ .css_alloc = blkcg_css_alloc,
+ .css_online = blkcg_css_online,
+ .css_offline = blkcg_css_offline,
+ .css_free = blkcg_css_free,
+ .css_rstat_flush = blkcg_rstat_flush,
+ .dfl_cftypes = blkcg_files,
+ .legacy_cftypes = blkcg_legacy_files,
+ .legacy_name = "blkio",
+ .exit = blkcg_exit,
+#ifdef CONFIG_MEMCG
+ /*
+ * This ensures that, if available, memcg is automatically enabled
+ * together on the default hierarchy so that the owner cgroup can
+ * be retrieved from writeback pages.
+ */
+ .depends_on = 1 << memory_cgrp_id,
+#endif
+};
+EXPORT_SYMBOL_GPL(io_cgrp_subsys);
+
+/**
+ * blkcg_activate_policy - activate a blkcg policy on a gendisk
+ * @disk: gendisk of interest
+ * @pol: blkcg policy to activate
+ *
+ * Activate @pol on @disk. Requires %GFP_KERNEL context. @disk goes through
+ * bypass mode to populate its blkgs with policy_data for @pol.
+ *
+ * Activation happens with @disk bypassed, so nobody would be accessing blkgs
+ * from IO path. Update of each blkg is protected by both queue and blkcg
+ * locks so that holding either lock and testing blkcg_policy_enabled() is
+ * always enough for dereferencing policy data.
+ *
+ * The caller is responsible for synchronizing [de]activations and policy
+ * [un]registerations. Returns 0 on success, -errno on failure.
+ */
+int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol)
+{
+ struct request_queue *q = disk->queue;
+ struct blkg_policy_data *pd_prealloc = NULL;
+ struct blkcg_gq *blkg, *pinned_blkg = NULL;
+ int ret;
+
+ if (blkcg_policy_enabled(q, pol))
+ return 0;
+
+ if (queue_is_mq(q))
+ blk_mq_freeze_queue(q);
+retry:
+ spin_lock_irq(&q->queue_lock);
+
+ /* blkg_list is pushed at the head, reverse walk to initialize parents first */
+ list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) {
+ struct blkg_policy_data *pd;
+
+ if (blkg->pd[pol->plid])
+ continue;
+
+ /* If prealloc matches, use it; otherwise try GFP_NOWAIT */
+ if (blkg == pinned_blkg) {
+ pd = pd_prealloc;
+ pd_prealloc = NULL;
+ } else {
+ pd = pol->pd_alloc_fn(disk, blkg->blkcg,
+ GFP_NOWAIT | __GFP_NOWARN);
+ }
+
+ if (!pd) {
+ /*
+ * GFP_NOWAIT failed. Free the existing one and
+ * prealloc for @blkg w/ GFP_KERNEL.
+ */
+ if (pinned_blkg)
+ blkg_put(pinned_blkg);
+ blkg_get(blkg);
+ pinned_blkg = blkg;
+
+ spin_unlock_irq(&q->queue_lock);
+
+ if (pd_prealloc)
+ pol->pd_free_fn(pd_prealloc);
+ pd_prealloc = pol->pd_alloc_fn(disk, blkg->blkcg,
+ GFP_KERNEL);
+ if (pd_prealloc)
+ goto retry;
+ else
+ goto enomem;
+ }
+
+ spin_lock(&blkg->blkcg->lock);
+
+ pd->blkg = blkg;
+ pd->plid = pol->plid;
+ blkg->pd[pol->plid] = pd;
+
+ if (pol->pd_init_fn)
+ pol->pd_init_fn(pd);
+
+ if (pol->pd_online_fn)
+ pol->pd_online_fn(pd);
+ pd->online = true;
+
+ spin_unlock(&blkg->blkcg->lock);
+ }
+
+ __set_bit(pol->plid, q->blkcg_pols);
+ ret = 0;
+
+ spin_unlock_irq(&q->queue_lock);
+out:
+ if (queue_is_mq(q))
+ blk_mq_unfreeze_queue(q);
+ if (pinned_blkg)
+ blkg_put(pinned_blkg);
+ if (pd_prealloc)
+ pol->pd_free_fn(pd_prealloc);
+ return ret;
+
+enomem:
+ /* alloc failed, take down everything */
+ spin_lock_irq(&q->queue_lock);
+ list_for_each_entry(blkg, &q->blkg_list, q_node) {
+ struct blkcg *blkcg = blkg->blkcg;
+ struct blkg_policy_data *pd;
+
+ spin_lock(&blkcg->lock);
+ pd = blkg->pd[pol->plid];
+ if (pd) {
+ if (pd->online && pol->pd_offline_fn)
+ pol->pd_offline_fn(pd);
+ pd->online = false;
+ pol->pd_free_fn(pd);
+ blkg->pd[pol->plid] = NULL;
+ }
+ spin_unlock(&blkcg->lock);
+ }
+ spin_unlock_irq(&q->queue_lock);
+ ret = -ENOMEM;
+ goto out;
+}
+EXPORT_SYMBOL_GPL(blkcg_activate_policy);
+
+/**
+ * blkcg_deactivate_policy - deactivate a blkcg policy on a gendisk
+ * @disk: gendisk of interest
+ * @pol: blkcg policy to deactivate
+ *
+ * Deactivate @pol on @disk. Follows the same synchronization rules as
+ * blkcg_activate_policy().
+ */
+void blkcg_deactivate_policy(struct gendisk *disk,
+ const struct blkcg_policy *pol)
+{
+ struct request_queue *q = disk->queue;
+ struct blkcg_gq *blkg;
+
+ if (!blkcg_policy_enabled(q, pol))
+ return;
+
+ if (queue_is_mq(q))
+ blk_mq_freeze_queue(q);
+
+ mutex_lock(&q->blkcg_mutex);
+ spin_lock_irq(&q->queue_lock);
+
+ __clear_bit(pol->plid, q->blkcg_pols);
+
+ list_for_each_entry(blkg, &q->blkg_list, q_node) {
+ struct blkcg *blkcg = blkg->blkcg;
+
+ spin_lock(&blkcg->lock);
+ if (blkg->pd[pol->plid]) {
+ if (blkg->pd[pol->plid]->online && pol->pd_offline_fn)
+ pol->pd_offline_fn(blkg->pd[pol->plid]);
+ pol->pd_free_fn(blkg->pd[pol->plid]);
+ blkg->pd[pol->plid] = NULL;
+ }
+ spin_unlock(&blkcg->lock);
+ }
+
+ spin_unlock_irq(&q->queue_lock);
+ mutex_unlock(&q->blkcg_mutex);
+
+ if (queue_is_mq(q))
+ blk_mq_unfreeze_queue(q);
+}
+EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
+
+static void blkcg_free_all_cpd(struct blkcg_policy *pol)
+{
+ struct blkcg *blkcg;
+
+ list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
+ if (blkcg->cpd[pol->plid]) {
+ pol->cpd_free_fn(blkcg->cpd[pol->plid]);
+ blkcg->cpd[pol->plid] = NULL;
+ }
+ }
+}
+
+/**
+ * blkcg_policy_register - register a blkcg policy
+ * @pol: blkcg policy to register
+ *
+ * Register @pol with blkcg core. Might sleep and @pol may be modified on
+ * successful registration. Returns 0 on success and -errno on failure.
+ */
+int blkcg_policy_register(struct blkcg_policy *pol)
+{
+ struct blkcg *blkcg;
+ int i, ret;
+
+ mutex_lock(&blkcg_pol_register_mutex);
+ mutex_lock(&blkcg_pol_mutex);
+
+ /* find an empty slot */
+ ret = -ENOSPC;
+ for (i = 0; i < BLKCG_MAX_POLS; i++)
+ if (!blkcg_policy[i])
+ break;
+ if (i >= BLKCG_MAX_POLS) {
+ pr_warn("blkcg_policy_register: BLKCG_MAX_POLS too small\n");
+ goto err_unlock;
+ }
+
+ /* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */
+ if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
+ (!pol->pd_alloc_fn ^ !pol->pd_free_fn))
+ goto err_unlock;
+
+ /* register @pol */
+ pol->plid = i;
+ blkcg_policy[pol->plid] = pol;
+
+ /* allocate and install cpd's */
+ if (pol->cpd_alloc_fn) {
+ list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
+ struct blkcg_policy_data *cpd;
+
+ cpd = pol->cpd_alloc_fn(GFP_KERNEL);
+ if (!cpd)
+ goto err_free_cpds;
+
+ blkcg->cpd[pol->plid] = cpd;
+ cpd->blkcg = blkcg;
+ cpd->plid = pol->plid;
+ }
+ }
+
+ mutex_unlock(&blkcg_pol_mutex);
+
+ /* everything is in place, add intf files for the new policy */
+ if (pol->dfl_cftypes)
+ WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys,
+ pol->dfl_cftypes));
+ if (pol->legacy_cftypes)
+ WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys,
+ pol->legacy_cftypes));
+ mutex_unlock(&blkcg_pol_register_mutex);
+ return 0;
+
+err_free_cpds:
+ if (pol->cpd_free_fn)
+ blkcg_free_all_cpd(pol);
+
+ blkcg_policy[pol->plid] = NULL;
+err_unlock:
+ mutex_unlock(&blkcg_pol_mutex);
+ mutex_unlock(&blkcg_pol_register_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(blkcg_policy_register);
+
+/**
+ * blkcg_policy_unregister - unregister a blkcg policy
+ * @pol: blkcg policy to unregister
+ *
+ * Undo blkcg_policy_register(@pol). Might sleep.
+ */
+void blkcg_policy_unregister(struct blkcg_policy *pol)
+{
+ mutex_lock(&blkcg_pol_register_mutex);
+
+ if (WARN_ON(blkcg_policy[pol->plid] != pol))
+ goto out_unlock;
+
+ /* kill the intf files first */
+ if (pol->dfl_cftypes)
+ cgroup_rm_cftypes(pol->dfl_cftypes);
+ if (pol->legacy_cftypes)
+ cgroup_rm_cftypes(pol->legacy_cftypes);
+
+ /* remove cpds and unregister */
+ mutex_lock(&blkcg_pol_mutex);
+
+ if (pol->cpd_free_fn)
+ blkcg_free_all_cpd(pol);
+
+ blkcg_policy[pol->plid] = NULL;
+
+ mutex_unlock(&blkcg_pol_mutex);
+out_unlock:
+ mutex_unlock(&blkcg_pol_register_mutex);
+}
+EXPORT_SYMBOL_GPL(blkcg_policy_unregister);
+
+/*
+ * Scale the accumulated delay based on how long it has been since we updated
+ * the delay. We only call this when we are adding delay, in case it's been a
+ * while since we added delay, and when we are checking to see if we need to
+ * delay a task, to account for any delays that may have occurred.
+ */
+static void blkcg_scale_delay(struct blkcg_gq *blkg, u64 now)
+{
+ u64 old = atomic64_read(&blkg->delay_start);
+
+ /* negative use_delay means no scaling, see blkcg_set_delay() */
+ if (atomic_read(&blkg->use_delay) < 0)
+ return;
+
+ /*
+ * We only want to scale down every second. The idea here is that we
+ * want to delay people for min(delay_nsec, NSEC_PER_SEC) in a certain
+ * time window. We only want to throttle tasks for recent delay that
+ * has occurred, in 1 second time windows since that's the maximum
+ * things can be throttled. We save the current delay window in
+ * blkg->last_delay so we know what amount is still left to be charged
+ * to the blkg from this point onward. blkg->last_use keeps track of
+ * the use_delay counter. The idea is if we're unthrottling the blkg we
+ * are ok with whatever is happening now, and we can take away more of
+ * the accumulated delay as we've already throttled enough that
+ * everybody is happy with their IO latencies.
+ */
+ if (time_before64(old + NSEC_PER_SEC, now) &&
+ atomic64_try_cmpxchg(&blkg->delay_start, &old, now)) {
+ u64 cur = atomic64_read(&blkg->delay_nsec);
+ u64 sub = min_t(u64, blkg->last_delay, now - old);
+ int cur_use = atomic_read(&blkg->use_delay);
+
+ /*
+ * We've been unthrottled, subtract a larger chunk of our
+ * accumulated delay.
+ */
+ if (cur_use < blkg->last_use)
+ sub = max_t(u64, sub, blkg->last_delay >> 1);
+
+ /*
+ * This shouldn't happen, but handle it anyway. Our delay_nsec
+ * should only ever be growing except here where we subtract out
+ * min(last_delay, 1 second), but lord knows bugs happen and I'd
+ * rather not end up with negative numbers.
+ */
+ if (unlikely(cur < sub)) {
+ atomic64_set(&blkg->delay_nsec, 0);
+ blkg->last_delay = 0;
+ } else {
+ atomic64_sub(sub, &blkg->delay_nsec);
+ blkg->last_delay = cur - sub;
+ }
+ blkg->last_use = cur_use;
+ }
+}
+
+/*
+ * This is called when we want to actually walk up the hierarchy and check to
+ * see if we need to throttle, and then actually throttle if there is some
+ * accumulated delay. This should only be called upon return to user space so
+ * we're not holding some lock that would induce a priority inversion.
+ */
+static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
+{
+ unsigned long pflags;
+ bool clamp;
+ u64 now = ktime_to_ns(ktime_get());
+ u64 exp;
+ u64 delay_nsec = 0;
+ int tok;
+
+ while (blkg->parent) {
+ int use_delay = atomic_read(&blkg->use_delay);
+
+ if (use_delay) {
+ u64 this_delay;
+
+ blkcg_scale_delay(blkg, now);
+ this_delay = atomic64_read(&blkg->delay_nsec);
+ if (this_delay > delay_nsec) {
+ delay_nsec = this_delay;
+ clamp = use_delay > 0;
+ }
+ }
+ blkg = blkg->parent;
+ }
+
+ if (!delay_nsec)
+ return;
+
+ /*
+ * Let's not sleep for all eternity if we've amassed a huge delay.
+ * Swapping or metadata IO can accumulate 10's of seconds worth of
+ * delay, and we want userspace to be able to do _something_ so cap the
+ * delays at 0.25s. If there's 10's of seconds worth of delay then the
+ * tasks will be delayed for 0.25 second for every syscall. If
+ * blkcg_set_delay() was used as indicated by negative use_delay, the
+ * caller is responsible for regulating the range.
+ */
+ if (clamp)
+ delay_nsec = min_t(u64, delay_nsec, 250 * NSEC_PER_MSEC);
+
+ if (use_memdelay)
+ psi_memstall_enter(&pflags);
+
+ exp = ktime_add_ns(now, delay_nsec);
+ tok = io_schedule_prepare();
+ do {
+ __set_current_state(TASK_KILLABLE);
+ if (!schedule_hrtimeout(&exp, HRTIMER_MODE_ABS))
+ break;
+ } while (!fatal_signal_pending(current));
+ io_schedule_finish(tok);
+
+ if (use_memdelay)
+ psi_memstall_leave(&pflags);
+}
+
+/**
+ * blkcg_maybe_throttle_current - throttle the current task if it has been marked
+ *
+ * This is only called if we've been marked with set_notify_resume(). Obviously
+ * we can be set_notify_resume() for reasons other than blkcg throttling, so we
+ * check to see if current->throttle_disk is set and if not this doesn't do
+ * anything. This should only ever be called by the resume code, it's not meant
+ * to be called by people willy-nilly as it will actually do the work to
+ * throttle the task if it is setup for throttling.
+ */
+void blkcg_maybe_throttle_current(void)
+{
+ struct gendisk *disk = current->throttle_disk;
+ struct blkcg *blkcg;
+ struct blkcg_gq *blkg;
+ bool use_memdelay = current->use_memdelay;
+
+ if (!disk)
+ return;
+
+ current->throttle_disk = NULL;
+ current->use_memdelay = false;
+
+ rcu_read_lock();
+ blkcg = css_to_blkcg(blkcg_css());
+ if (!blkcg)
+ goto out;
+ blkg = blkg_lookup(blkcg, disk->queue);
+ if (!blkg)
+ goto out;
+ if (!blkg_tryget(blkg))
+ goto out;
+ rcu_read_unlock();
+
+ blkcg_maybe_throttle_blkg(blkg, use_memdelay);
+ blkg_put(blkg);
+ put_disk(disk);
+ return;
+out:
+ rcu_read_unlock();
+}
+
+/**
+ * blkcg_schedule_throttle - this task needs to check for throttling
+ * @disk: disk to throttle
+ * @use_memdelay: do we charge this to memory delay for PSI
+ *
+ * This is called by the IO controller when we know there's delay accumulated
+ * for the blkg for this task. We do not pass the blkg because there are places
+ * we call this that may not have that information, the swapping code for
+ * instance will only have a block_device at that point. This set's the
+ * notify_resume for the task to check and see if it requires throttling before
+ * returning to user space.
+ *
+ * We will only schedule once per syscall. You can call this over and over
+ * again and it will only do the check once upon return to user space, and only
+ * throttle once. If the task needs to be throttled again it'll need to be
+ * re-set at the next time we see the task.
+ */
+void blkcg_schedule_throttle(struct gendisk *disk, bool use_memdelay)
+{
+ if (unlikely(current->flags & PF_KTHREAD))
+ return;
+
+ if (current->throttle_disk != disk) {
+ if (test_bit(GD_DEAD, &disk->state))
+ return;
+ get_device(disk_to_dev(disk));
+
+ if (current->throttle_disk)
+ put_disk(current->throttle_disk);
+ current->throttle_disk = disk;
+ }
+
+ if (use_memdelay)
+ current->use_memdelay = use_memdelay;
+ set_notify_resume(current);
+}
+
+/**
+ * blkcg_add_delay - add delay to this blkg
+ * @blkg: blkg of interest
+ * @now: the current time in nanoseconds
+ * @delta: how many nanoseconds of delay to add
+ *
+ * Charge @delta to the blkg's current delay accumulation. This is used to
+ * throttle tasks if an IO controller thinks we need more throttling.
+ */
+void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta)
+{
+ if (WARN_ON_ONCE(atomic_read(&blkg->use_delay) < 0))
+ return;
+ blkcg_scale_delay(blkg, now);
+ atomic64_add(delta, &blkg->delay_nsec);
+}
+
+/**
+ * blkg_tryget_closest - try and get a blkg ref on the closet blkg
+ * @bio: target bio
+ * @css: target css
+ *
+ * As the failure mode here is to walk up the blkg tree, this ensure that the
+ * blkg->parent pointers are always valid. This returns the blkg that it ended
+ * up taking a reference on or %NULL if no reference was taken.
+ */
+static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio,
+ struct cgroup_subsys_state *css)
+{
+ struct blkcg_gq *blkg, *ret_blkg = NULL;
+
+ rcu_read_lock();
+ blkg = blkg_lookup_create(css_to_blkcg(css), bio->bi_bdev->bd_disk);
+ while (blkg) {
+ if (blkg_tryget(blkg)) {
+ ret_blkg = blkg;
+ break;
+ }
+ blkg = blkg->parent;
+ }
+ rcu_read_unlock();
+
+ return ret_blkg;
+}
+
+/**
+ * bio_associate_blkg_from_css - associate a bio with a specified css
+ * @bio: target bio
+ * @css: target css
+ *
+ * Associate @bio with the blkg found by combining the css's blkg and the
+ * request_queue of the @bio. An association failure is handled by walking up
+ * the blkg tree. Therefore, the blkg associated can be anything between @blkg
+ * and q->root_blkg. This situation only happens when a cgroup is dying and
+ * then the remaining bios will spill to the closest alive blkg.
+ *
+ * A reference will be taken on the blkg and will be released when @bio is
+ * freed.
+ */
+void bio_associate_blkg_from_css(struct bio *bio,
+ struct cgroup_subsys_state *css)
+{
+ if (bio->bi_blkg)
+ blkg_put(bio->bi_blkg);
+
+ if (css && css->parent) {
+ bio->bi_blkg = blkg_tryget_closest(bio, css);
+ } else {
+ blkg_get(bdev_get_queue(bio->bi_bdev)->root_blkg);
+ bio->bi_blkg = bdev_get_queue(bio->bi_bdev)->root_blkg;
+ }
+}
+EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
+
+/**
+ * bio_associate_blkg - associate a bio with a blkg
+ * @bio: target bio
+ *
+ * Associate @bio with the blkg found from the bio's css and request_queue.
+ * If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is
+ * already associated, the css is reused and association redone as the
+ * request_queue may have changed.
+ */
+void bio_associate_blkg(struct bio *bio)
+{
+ struct cgroup_subsys_state *css;
+
+ rcu_read_lock();
+
+ if (bio->bi_blkg)
+ css = bio_blkcg_css(bio);
+ else
+ css = blkcg_css();
+
+ bio_associate_blkg_from_css(bio, css);
+
+ rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(bio_associate_blkg);
+
+/**
+ * bio_clone_blkg_association - clone blkg association from src to dst bio
+ * @dst: destination bio
+ * @src: source bio
+ */
+void bio_clone_blkg_association(struct bio *dst, struct bio *src)
+{
+ if (src->bi_blkg)
+ bio_associate_blkg_from_css(dst, bio_blkcg_css(src));
+}
+EXPORT_SYMBOL_GPL(bio_clone_blkg_association);
+
+static int blk_cgroup_io_type(struct bio *bio)
+{
+ if (op_is_discard(bio->bi_opf))
+ return BLKG_IOSTAT_DISCARD;
+ if (op_is_write(bio->bi_opf))
+ return BLKG_IOSTAT_WRITE;
+ return BLKG_IOSTAT_READ;
+}
+
+void blk_cgroup_bio_start(struct bio *bio)
+{
+ struct blkcg *blkcg = bio->bi_blkg->blkcg;
+ int rwd = blk_cgroup_io_type(bio), cpu;
+ struct blkg_iostat_set *bis;
+ unsigned long flags;
+
+ if (!cgroup_subsys_on_dfl(io_cgrp_subsys))
+ return;
+
+ /* Root-level stats are sourced from system-wide IO stats */
+ if (!cgroup_parent(blkcg->css.cgroup))
+ return;
+
+ cpu = get_cpu();
+ bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu);
+ flags = u64_stats_update_begin_irqsave(&bis->sync);
+
+ /*
+ * If the bio is flagged with BIO_CGROUP_ACCT it means this is a split
+ * bio and we would have already accounted for the size of the bio.
+ */
+ if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
+ bio_set_flag(bio, BIO_CGROUP_ACCT);
+ bis->cur.bytes[rwd] += bio->bi_iter.bi_size;
+ }
+ bis->cur.ios[rwd]++;
+
+ /*
+ * If the iostat_cpu isn't in a lockless list, put it into the
+ * list to indicate that a stat update is pending.
+ */
+ if (!READ_ONCE(bis->lqueued)) {
+ struct llist_head *lhead = this_cpu_ptr(blkcg->lhead);
+
+ llist_add(&bis->lnode, lhead);
+ WRITE_ONCE(bis->lqueued, true);
+ }
+
+ u64_stats_update_end_irqrestore(&bis->sync, flags);
+ cgroup_rstat_updated(blkcg->css.cgroup, cpu);
+ put_cpu();
+}
+
+bool blk_cgroup_congested(void)
+{
+ struct cgroup_subsys_state *css;
+ bool ret = false;
+
+ rcu_read_lock();
+ for (css = blkcg_css(); css; css = css->parent) {
+ if (atomic_read(&css->cgroup->congestion_count)) {
+ ret = true;
+ break;
+ }
+ }
+ rcu_read_unlock();
+ return ret;
+}
+
+module_param(blkcg_debug_stats, bool, 0644);
+MODULE_PARM_DESC(blkcg_debug_stats, "True if you want debug stats, false if not");