original development tree for Linux kernel GTP module; now long in mainline.
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/*
* 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>
*/
#include <linux/ioprio.h>
#include <linux/kdev_t.h>
#include <linux/module.h>
#include <linux/err.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/genhd.h>
#include <linux/delay.h>
#include <linux/atomic.h>
#include "blk-cgroup.h"
#include "blk.h"
#define MAX_KEY_LEN 100
static DEFINE_SPINLOCK(blkio_list_lock);
static LIST_HEAD(blkio_list);
static DEFINE_MUTEX(all_q_mutex);
static LIST_HEAD(all_q_list);
struct blkio_cgroup blkio_root_cgroup = { .cfq_weight = 2 * CFQ_WEIGHT_DEFAULT };
EXPORT_SYMBOL_GPL(blkio_root_cgroup);
static struct blkio_policy_type *blkio_policy[BLKIO_NR_POLICIES];
struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
{
return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
struct blkio_cgroup, css);
}
EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
static struct blkio_cgroup *task_blkio_cgroup(struct task_struct *tsk)
{
return container_of(task_subsys_state(tsk, blkio_subsys_id),
struct blkio_cgroup, css);
}
struct blkio_cgroup *bio_blkio_cgroup(struct bio *bio)
{
if (bio && bio->bi_css)
return container_of(bio->bi_css, struct blkio_cgroup, css);
return task_blkio_cgroup(current);
}
EXPORT_SYMBOL_GPL(bio_blkio_cgroup);
/**
* blkg_free - free a blkg
* @blkg: blkg to free
*
* Free @blkg which may be partially allocated.
*/
static void blkg_free(struct blkio_group *blkg)
{
int i;
if (!blkg)
return;
for (i = 0; i < BLKIO_NR_POLICIES; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
struct blkg_policy_data *pd = blkg->pd[i];
if (!pd)
continue;
if (pol && pol->ops.blkio_exit_group_fn)
pol->ops.blkio_exit_group_fn(blkg);
kfree(pd);
}
kfree(blkg);
}
/**
* blkg_alloc - allocate a blkg
* @blkcg: block cgroup the new blkg is associated with
* @q: request_queue the new blkg is associated with
*
* Allocate a new blkg assocating @blkcg and @q.
*/
static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
struct request_queue *q)
{
struct blkio_group *blkg;
int i;
/* alloc and init base part */
blkg = kzalloc_node(sizeof(*blkg), GFP_ATOMIC, q->node);
if (!blkg)
return NULL;
blkg->q = q;
INIT_LIST_HEAD(&blkg->q_node);
blkg->blkcg = blkcg;
blkg->refcnt = 1;
cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
for (i = 0; i < BLKIO_NR_POLICIES; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
struct blkg_policy_data *pd;
if (!pol)
continue;
/* alloc per-policy data and attach it to blkg */
pd = kzalloc_node(sizeof(*pd) + pol->pdata_size, GFP_ATOMIC,
q->node);
if (!pd) {
blkg_free(blkg);
return NULL;
}
blkg->pd[i] = pd;
pd->blkg = blkg;
}
/* invoke per-policy init */
for (i = 0; i < BLKIO_NR_POLICIES; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
if (pol)
pol->ops.blkio_init_group_fn(blkg);
}
return blkg;
}
struct blkio_group *blkg_lookup_create(struct blkio_cgroup *blkcg,
struct request_queue *q,
bool for_root)
__releases(q->queue_lock) __acquires(q->queue_lock)
{
struct blkio_group *blkg;
WARN_ON_ONCE(!rcu_read_lock_held());
lockdep_assert_held(q->queue_lock);
/*
* This could be the first entry point of blkcg implementation and
* we shouldn't allow anything to go through for a bypassing queue.
* The following can be removed if blkg lookup is guaranteed to
* fail on a bypassing queue.
*/
if (unlikely(blk_queue_bypass(q)) && !for_root)
return ERR_PTR(blk_queue_dead(q) ? -EINVAL : -EBUSY);
blkg = blkg_lookup(blkcg, q);
if (blkg)
return blkg;
/* blkg holds a reference to blkcg */
if (!css_tryget(&blkcg->css))
return ERR_PTR(-EINVAL);
/*
* Allocate and initialize.
*/
blkg = blkg_alloc(blkcg, q);
/* did alloc fail? */
if (unlikely(!blkg)) {
blkg = ERR_PTR(-ENOMEM);
goto out;
}
/* insert */
spin_lock(&blkcg->lock);
hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
list_add(&blkg->q_node, &q->blkg_list);
spin_unlock(&blkcg->lock);
out:
return blkg;
}
EXPORT_SYMBOL_GPL(blkg_lookup_create);
/* called under rcu_read_lock(). */
struct blkio_group *blkg_lookup(struct blkio_cgroup *blkcg,
struct request_queue *q)
{
struct blkio_group *blkg;
struct hlist_node *n;
hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node)
if (blkg->q == q)
return blkg;
return NULL;
}
EXPORT_SYMBOL_GPL(blkg_lookup);
static void blkg_destroy(struct blkio_group *blkg)
{
struct request_queue *q = blkg->q;
struct blkio_cgroup *blkcg = blkg->blkcg;
lockdep_assert_held(q->queue_lock);
lockdep_assert_held(&blkcg->lock);
/* Something wrong if we are trying to remove same group twice */
WARN_ON_ONCE(list_empty(&blkg->q_node));
WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
list_del_init(&blkg->q_node);
hlist_del_init_rcu(&blkg->blkcg_node);
/*
* Put the reference taken at the time of creation so that when all
* queues are gone, group can be destroyed.
*/
blkg_put(blkg);
}
/*
* XXX: This updates blkg policy data in-place for root blkg, which is
* necessary across elevator switch and policy registration as root blkgs
* aren't shot down. This broken and racy implementation is temporary.
* Eventually, blkg shoot down will be replaced by proper in-place update.
*/
void update_root_blkg_pd(struct request_queue *q, enum blkio_policy_id plid)
{
struct blkio_policy_type *pol = blkio_policy[plid];
struct blkio_group *blkg = blkg_lookup(&blkio_root_cgroup, q);
struct blkg_policy_data *pd;
if (!blkg)
return;
kfree(blkg->pd[plid]);
blkg->pd[plid] = NULL;
if (!pol)
return;
pd = kzalloc(sizeof(*pd) + pol->pdata_size, GFP_KERNEL);
WARN_ON_ONCE(!pd);
blkg->pd[plid] = pd;
pd->blkg = blkg;
pol->ops.blkio_init_group_fn(blkg);
}
EXPORT_SYMBOL_GPL(update_root_blkg_pd);
/**
* blkg_destroy_all - destroy all blkgs associated with a request_queue
* @q: request_queue of interest
* @destroy_root: whether to destroy root blkg or not
*
* Destroy blkgs associated with @q. If @destroy_root is %true, all are
* destroyed; otherwise, root blkg is left alone.
*/
void blkg_destroy_all(struct request_queue *q, bool destroy_root)
{
struct blkio_group *blkg, *n;
spin_lock_irq(q->queue_lock);
list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
struct blkio_cgroup *blkcg = blkg->blkcg;
/* skip root? */
if (!destroy_root && blkg->blkcg == &blkio_root_cgroup)
continue;
spin_lock(&blkcg->lock);
blkg_destroy(blkg);
spin_unlock(&blkcg->lock);
}
spin_unlock_irq(q->queue_lock);
}
EXPORT_SYMBOL_GPL(blkg_destroy_all);
static void blkg_rcu_free(struct rcu_head *rcu_head)
{
blkg_free(container_of(rcu_head, struct blkio_group, rcu_head));
}
void __blkg_release(struct blkio_group *blkg)
{
/* release the extra blkcg reference this blkg has been holding */
css_put(&blkg->blkcg->css);
/*
* A group is freed in rcu manner. 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 acess to only
* values local to groups like group stats and group rate limits
*/
call_rcu(&blkg->rcu_head, blkg_rcu_free);
}
EXPORT_SYMBOL_GPL(__blkg_release);
static int
blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
{
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
struct blkio_group *blkg;
struct hlist_node *n;
spin_lock(&blkio_list_lock);
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, n, &blkcg->blkg_list, blkcg_node) {
struct blkio_policy_type *pol;
list_for_each_entry(pol, &blkio_list, list)
if (pol->ops.blkio_reset_group_stats_fn)
pol->ops.blkio_reset_group_stats_fn(blkg);
}
spin_unlock_irq(&blkcg->lock);
spin_unlock(&blkio_list_lock);
return 0;
}
static const char *blkg_dev_name(struct blkio_group *blkg)
{
/* some drivers (floppy) instantiate a queue w/o disk registered */
if (blkg->q->backing_dev_info.dev)
return dev_name(blkg->q->backing_dev_info.dev);
return NULL;
}
/**
* 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. 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 blkio_cgroup *blkcg,
u64 (*prfill)(struct seq_file *, void *, int),
int pol, int data, bool show_total)
{
struct blkio_group *blkg;
struct hlist_node *n;
u64 total = 0;
spin_lock_irq(&blkcg->lock);
hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
if (blkg->pd[pol])
total += prfill(sf, blkg->pd[pol]->pdata, data);
spin_unlock_irq(&blkcg->lock);
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
* @pdata: policy private data of interest
* @v: value to print
*
* Print @v to @sf for the device assocaited with @pdata.
*/
u64 __blkg_prfill_u64(struct seq_file *sf, void *pdata, u64 v)
{
const char *dname = blkg_dev_name(pdata_to_blkg(pdata));
if (!dname)
return 0;
seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
return v;
}
EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
/**
* __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
* @sf: seq_file to print to
* @pdata: policy private data of interest
* @rwstat: rwstat to print
*
* Print @rwstat to @sf for the device assocaited with @pdata.
*/
u64 __blkg_prfill_rwstat(struct seq_file *sf, void *pdata,
const struct blkg_rwstat *rwstat)
{
static const char *rwstr[] = {
[BLKG_RWSTAT_READ] = "Read",
[BLKG_RWSTAT_WRITE] = "Write",
[BLKG_RWSTAT_SYNC] = "Sync",
[BLKG_RWSTAT_ASYNC] = "Async",
};
const char *dname = blkg_dev_name(pdata_to_blkg(pdata));
u64 v;
int i;
if (!dname)
return 0;
for (i = 0; i < BLKG_RWSTAT_NR; i++)
seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
(unsigned long long)rwstat->cnt[i]);
v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
return v;
}
/**
* blkg_prfill_stat - prfill callback for blkg_stat
* @sf: seq_file to print to
* @pdata: policy private data of interest
* @off: offset to the blkg_stat in @pdata
*
* prfill callback for printing a blkg_stat.
*/
u64 blkg_prfill_stat(struct seq_file *sf, void *pdata, int off)
{
return __blkg_prfill_u64(sf, pdata, blkg_stat_read(pdata + off));
}
EXPORT_SYMBOL_GPL(blkg_prfill_stat);
/**
* blkg_prfill_rwstat - prfill callback for blkg_rwstat
* @sf: seq_file to print to
* @pdata: policy private data of interest
* @off: offset to the blkg_rwstat in @pdata
*
* prfill callback for printing a blkg_rwstat.
*/
u64 blkg_prfill_rwstat(struct seq_file *sf, void *pdata, int off)
{
struct blkg_rwstat rwstat = blkg_rwstat_read(pdata + off);
return __blkg_prfill_rwstat(sf, pdata, &rwstat);
}
EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
/**
* blkg_conf_prep - parse and prepare for per-blkg config update
* @blkcg: target block cgroup
* @input: input string
* @ctx: blkg_conf_ctx to be filled
*
* Parse per-blkg config update from @input and initialize @ctx with the
* result. @ctx->blkg points to the blkg to be updated and @ctx->v the new
* value. This function returns with RCU read locked and must be paired
* with blkg_conf_finish().
*/
int blkg_conf_prep(struct blkio_cgroup *blkcg, const char *input,
struct blkg_conf_ctx *ctx)
__acquires(rcu)
{
struct gendisk *disk;
struct blkio_group *blkg;
unsigned int major, minor;
unsigned long long v;
int part, ret;
if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
return -EINVAL;
disk = get_gendisk(MKDEV(major, minor), &part);
if (!disk || part)
return -EINVAL;
rcu_read_lock();
spin_lock_irq(disk->queue->queue_lock);
blkg = blkg_lookup_create(blkcg, disk->queue, false);
spin_unlock_irq(disk->queue->queue_lock);
if (IS_ERR(blkg)) {
ret = PTR_ERR(blkg);
rcu_read_unlock();
put_disk(disk);
/*
* 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;
}
ctx->disk = disk;
ctx->blkg = blkg;
ctx->v = v;
return 0;
}
EXPORT_SYMBOL_GPL(blkg_conf_prep);
/**
* blkg_conf_finish - finish up per-blkg config update
* @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
*
* Finish up after per-blkg config update. This function must be paired
* with blkg_conf_prep().
*/
void blkg_conf_finish(struct blkg_conf_ctx *ctx)
__releases(rcu)
{
rcu_read_unlock();
put_disk(ctx->disk);
}
EXPORT_SYMBOL_GPL(blkg_conf_finish);
struct cftype blkio_files[] = {
{
.name = "reset_stats",
.write_u64 = blkiocg_reset_stats,
},
{ } /* terminate */
};
/**
* blkiocg_pre_destroy - cgroup pre_destroy callback
* @cgroup: cgroup of interest
*
* This function is called when @cgroup is about to go away and responsible
* for shooting down all blkgs associated with @cgroup. 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.
*
* This is the blkcg counterpart of ioc_release_fn().
*/
static int blkiocg_pre_destroy(struct cgroup *cgroup)
{
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
spin_lock_irq(&blkcg->lock);
while (!hlist_empty(&blkcg->blkg_list)) {
struct blkio_group *blkg = hlist_entry(blkcg->blkg_list.first,
struct blkio_group, blkcg_node);
struct request_queue *q = blkg->q;
if (spin_trylock(q->queue_lock)) {
blkg_destroy(blkg);
spin_unlock(q->queue_lock);
} else {
spin_unlock_irq(&blkcg->lock);
cpu_relax();
spin_lock_irq(&blkcg->lock);
}
}
spin_unlock_irq(&blkcg->lock);
return 0;
}
static void blkiocg_destroy(struct cgroup *cgroup)
{
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
if (blkcg != &blkio_root_cgroup)
kfree(blkcg);
}
static struct cgroup_subsys_state *blkiocg_create(struct cgroup *cgroup)
{
static atomic64_t id_seq = ATOMIC64_INIT(0);
struct blkio_cgroup *blkcg;
struct cgroup *parent = cgroup->parent;
if (!parent) {
blkcg = &blkio_root_cgroup;
goto done;
}
blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
if (!blkcg)
return ERR_PTR(-ENOMEM);
blkcg->cfq_weight = CFQ_WEIGHT_DEFAULT;
blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
done:
spin_lock_init(&blkcg->lock);
INIT_HLIST_HEAD(&blkcg->blkg_list);
return &blkcg->css;
}
/**
* blkcg_init_queue - initialize blkcg part of request queue
* @q: request_queue to initialize
*
* Called from blk_alloc_queue_node(). Responsible for initializing blkcg
* part of new request_queue @q.
*
* RETURNS:
* 0 on success, -errno on failure.
*/
int blkcg_init_queue(struct request_queue *q)
{
int ret;
might_sleep();
ret = blk_throtl_init(q);
if (ret)
return ret;
mutex_lock(&all_q_mutex);
INIT_LIST_HEAD(&q->all_q_node);
list_add_tail(&q->all_q_node, &all_q_list);
mutex_unlock(&all_q_mutex);
return 0;
}
/**
* blkcg_drain_queue - drain blkcg part of request_queue
* @q: request_queue to drain
*
* Called from blk_drain_queue(). Responsible for draining blkcg part.
*/
void blkcg_drain_queue(struct request_queue *q)
{
lockdep_assert_held(q->queue_lock);
blk_throtl_drain(q);
}
/**
* blkcg_exit_queue - exit and release blkcg part of request_queue
* @q: request_queue being released
*
* Called from blk_release_queue(). Responsible for exiting blkcg part.
*/
void blkcg_exit_queue(struct request_queue *q)
{
mutex_lock(&all_q_mutex);
list_del_init(&q->all_q_node);
mutex_unlock(&all_q_mutex);
blkg_destroy_all(q, true);
blk_throtl_exit(q);
}
/*
* We cannot support shared io contexts, as we have no mean to support
* two tasks with the same ioc in two different groups without major rework
* of the main cic data structures. For now we allow a task to change
* its cgroup only if it's the only owner of its ioc.
*/
static int blkiocg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
{
struct task_struct *task;
struct io_context *ioc;
int ret = 0;
/* task_lock() is needed to avoid races with exit_io_context() */
cgroup_taskset_for_each(task, cgrp, tset) {
task_lock(task);
ioc = task->io_context;
if (ioc && atomic_read(&ioc->nr_tasks) > 1)
ret = -EINVAL;
task_unlock(task);
if (ret)
break;
}
return ret;
}
static void blkcg_bypass_start(void)
__acquires(&all_q_mutex)
{
struct request_queue *q;
mutex_lock(&all_q_mutex);
list_for_each_entry(q, &all_q_list, all_q_node) {
blk_queue_bypass_start(q);
blkg_destroy_all(q, false);
}
}
static void blkcg_bypass_end(void)
__releases(&all_q_mutex)
{
struct request_queue *q;
list_for_each_entry(q, &all_q_list, all_q_node)
blk_queue_bypass_end(q);
mutex_unlock(&all_q_mutex);
}
struct cgroup_subsys blkio_subsys = {
.name = "blkio",
.create = blkiocg_create,
.can_attach = blkiocg_can_attach,
.pre_destroy = blkiocg_pre_destroy,
.destroy = blkiocg_destroy,
.subsys_id = blkio_subsys_id,
.base_cftypes = blkio_files,
.module = THIS_MODULE,
};
EXPORT_SYMBOL_GPL(blkio_subsys);
void blkio_policy_register(struct blkio_policy_type *blkiop)
{
struct request_queue *q;
blkcg_bypass_start();
spin_lock(&blkio_list_lock);
BUG_ON(blkio_policy[blkiop->plid]);
blkio_policy[blkiop->plid] = blkiop;
list_add_tail(&blkiop->list, &blkio_list);
spin_unlock(&blkio_list_lock);
list_for_each_entry(q, &all_q_list, all_q_node)
update_root_blkg_pd(q, blkiop->plid);
blkcg_bypass_end();
if (blkiop->cftypes)
WARN_ON(cgroup_add_cftypes(&blkio_subsys, blkiop->cftypes));
}
EXPORT_SYMBOL_GPL(blkio_policy_register);
void blkio_policy_unregister(struct blkio_policy_type *blkiop)
{
struct request_queue *q;
if (blkiop->cftypes)
cgroup_rm_cftypes(&blkio_subsys, blkiop->cftypes);
blkcg_bypass_start();
spin_lock(&blkio_list_lock);
BUG_ON(blkio_policy[blkiop->plid] != blkiop);
blkio_policy[blkiop->plid] = NULL;
list_del_init(&blkiop->list);
spin_unlock(&blkio_list_lock);
list_for_each_entry(q, &all_q_list, all_q_node)
update_root_blkg_pd(q, blkiop->plid);
blkcg_bypass_end();
}
EXPORT_SYMBOL_GPL(blkio_policy_unregister);