linux/mm/backing-dev.c
Tejun Heo d866dbf617 blkcg: rename blkcg->cgwb_refcnt to ->online_pin and always use it
blkcg->cgwb_refcnt is used to delay blkcg offlining so that blkgs
don't get offlined while there are active cgwbs on them.  However, it
ends up making offlining unordered sometimes causing parents to be
offlined before children.

To fix it, we want child blkcgs to pin the parents' online states
turning the refcnt into a more generic online pinning mechanism.

In prepartion,

* blkcg->cgwb_refcnt -> blkcg->online_pin
* blkcg_cgwb_get/put() -> blkcg_pin/unpin_online()
* Take them out of CONFIG_CGROUP_WRITEBACK

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-04-01 14:56:42 -06:00

1150 lines
28 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/wait.h>
#include <linux/rbtree.h>
#include <linux/backing-dev.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/writeback.h>
#include <linux/device.h>
#include <trace/events/writeback.h>
struct backing_dev_info noop_backing_dev_info = {
.name = "noop",
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
EXPORT_SYMBOL_GPL(noop_backing_dev_info);
static struct class *bdi_class;
const char *bdi_unknown_name = "(unknown)";
/*
* bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
* reader side locking.
*/
DEFINE_SPINLOCK(bdi_lock);
static u64 bdi_id_cursor;
static struct rb_root bdi_tree = RB_ROOT;
LIST_HEAD(bdi_list);
/* bdi_wq serves all asynchronous writeback tasks */
struct workqueue_struct *bdi_wq;
#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
#include <linux/seq_file.h>
static struct dentry *bdi_debug_root;
static void bdi_debug_init(void)
{
bdi_debug_root = debugfs_create_dir("bdi", NULL);
}
static int bdi_debug_stats_show(struct seq_file *m, void *v)
{
struct backing_dev_info *bdi = m->private;
struct bdi_writeback *wb = &bdi->wb;
unsigned long background_thresh;
unsigned long dirty_thresh;
unsigned long wb_thresh;
unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
struct inode *inode;
nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
spin_lock(&wb->list_lock);
list_for_each_entry(inode, &wb->b_dirty, i_io_list)
nr_dirty++;
list_for_each_entry(inode, &wb->b_io, i_io_list)
nr_io++;
list_for_each_entry(inode, &wb->b_more_io, i_io_list)
nr_more_io++;
list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
if (inode->i_state & I_DIRTY_TIME)
nr_dirty_time++;
spin_unlock(&wb->list_lock);
global_dirty_limits(&background_thresh, &dirty_thresh);
wb_thresh = wb_calc_thresh(wb, dirty_thresh);
#define K(x) ((x) << (PAGE_SHIFT - 10))
seq_printf(m,
"BdiWriteback: %10lu kB\n"
"BdiReclaimable: %10lu kB\n"
"BdiDirtyThresh: %10lu kB\n"
"DirtyThresh: %10lu kB\n"
"BackgroundThresh: %10lu kB\n"
"BdiDirtied: %10lu kB\n"
"BdiWritten: %10lu kB\n"
"BdiWriteBandwidth: %10lu kBps\n"
"b_dirty: %10lu\n"
"b_io: %10lu\n"
"b_more_io: %10lu\n"
"b_dirty_time: %10lu\n"
"bdi_list: %10u\n"
"state: %10lx\n",
(unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
(unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
K(wb_thresh),
K(dirty_thresh),
K(background_thresh),
(unsigned long) K(wb_stat(wb, WB_DIRTIED)),
(unsigned long) K(wb_stat(wb, WB_WRITTEN)),
(unsigned long) K(wb->write_bandwidth),
nr_dirty,
nr_io,
nr_more_io,
nr_dirty_time,
!list_empty(&bdi->bdi_list), bdi->wb.state);
#undef K
return 0;
}
DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
{
bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
&bdi_debug_stats_fops);
}
static void bdi_debug_unregister(struct backing_dev_info *bdi)
{
debugfs_remove_recursive(bdi->debug_dir);
}
#else
static inline void bdi_debug_init(void)
{
}
static inline void bdi_debug_register(struct backing_dev_info *bdi,
const char *name)
{
}
static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
{
}
#endif
static ssize_t read_ahead_kb_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct backing_dev_info *bdi = dev_get_drvdata(dev);
unsigned long read_ahead_kb;
ssize_t ret;
ret = kstrtoul(buf, 10, &read_ahead_kb);
if (ret < 0)
return ret;
bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
return count;
}
#define K(pages) ((pages) << (PAGE_SHIFT - 10))
#define BDI_SHOW(name, expr) \
static ssize_t name##_show(struct device *dev, \
struct device_attribute *attr, char *page) \
{ \
struct backing_dev_info *bdi = dev_get_drvdata(dev); \
\
return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
} \
static DEVICE_ATTR_RW(name);
BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
static ssize_t min_ratio_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
struct backing_dev_info *bdi = dev_get_drvdata(dev);
unsigned int ratio;
ssize_t ret;
ret = kstrtouint(buf, 10, &ratio);
if (ret < 0)
return ret;
ret = bdi_set_min_ratio(bdi, ratio);
if (!ret)
ret = count;
return ret;
}
BDI_SHOW(min_ratio, bdi->min_ratio)
static ssize_t max_ratio_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
struct backing_dev_info *bdi = dev_get_drvdata(dev);
unsigned int ratio;
ssize_t ret;
ret = kstrtouint(buf, 10, &ratio);
if (ret < 0)
return ret;
ret = bdi_set_max_ratio(bdi, ratio);
if (!ret)
ret = count;
return ret;
}
BDI_SHOW(max_ratio, bdi->max_ratio)
static ssize_t stable_pages_required_show(struct device *dev,
struct device_attribute *attr,
char *page)
{
struct backing_dev_info *bdi = dev_get_drvdata(dev);
return snprintf(page, PAGE_SIZE-1, "%d\n",
bdi_cap_stable_pages_required(bdi) ? 1 : 0);
}
static DEVICE_ATTR_RO(stable_pages_required);
static struct attribute *bdi_dev_attrs[] = {
&dev_attr_read_ahead_kb.attr,
&dev_attr_min_ratio.attr,
&dev_attr_max_ratio.attr,
&dev_attr_stable_pages_required.attr,
NULL,
};
ATTRIBUTE_GROUPS(bdi_dev);
static __init int bdi_class_init(void)
{
bdi_class = class_create(THIS_MODULE, "bdi");
if (IS_ERR(bdi_class))
return PTR_ERR(bdi_class);
bdi_class->dev_groups = bdi_dev_groups;
bdi_debug_init();
return 0;
}
postcore_initcall(bdi_class_init);
static int bdi_init(struct backing_dev_info *bdi);
static int __init default_bdi_init(void)
{
int err;
bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
WQ_SYSFS, 0);
if (!bdi_wq)
return -ENOMEM;
err = bdi_init(&noop_backing_dev_info);
return err;
}
subsys_initcall(default_bdi_init);
/*
* This function is used when the first inode for this wb is marked dirty. It
* wakes-up the corresponding bdi thread which should then take care of the
* periodic background write-out of dirty inodes. Since the write-out would
* starts only 'dirty_writeback_interval' centisecs from now anyway, we just
* set up a timer which wakes the bdi thread up later.
*
* Note, we wouldn't bother setting up the timer, but this function is on the
* fast-path (used by '__mark_inode_dirty()'), so we save few context switches
* by delaying the wake-up.
*
* We have to be careful not to postpone flush work if it is scheduled for
* earlier. Thus we use queue_delayed_work().
*/
void wb_wakeup_delayed(struct bdi_writeback *wb)
{
unsigned long timeout;
timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
spin_lock_bh(&wb->work_lock);
if (test_bit(WB_registered, &wb->state))
queue_delayed_work(bdi_wq, &wb->dwork, timeout);
spin_unlock_bh(&wb->work_lock);
}
/*
* Initial write bandwidth: 100 MB/s
*/
#define INIT_BW (100 << (20 - PAGE_SHIFT))
static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
int blkcg_id, gfp_t gfp)
{
int i, err;
memset(wb, 0, sizeof(*wb));
if (wb != &bdi->wb)
bdi_get(bdi);
wb->bdi = bdi;
wb->last_old_flush = jiffies;
INIT_LIST_HEAD(&wb->b_dirty);
INIT_LIST_HEAD(&wb->b_io);
INIT_LIST_HEAD(&wb->b_more_io);
INIT_LIST_HEAD(&wb->b_dirty_time);
spin_lock_init(&wb->list_lock);
wb->bw_time_stamp = jiffies;
wb->balanced_dirty_ratelimit = INIT_BW;
wb->dirty_ratelimit = INIT_BW;
wb->write_bandwidth = INIT_BW;
wb->avg_write_bandwidth = INIT_BW;
spin_lock_init(&wb->work_lock);
INIT_LIST_HEAD(&wb->work_list);
INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
wb->dirty_sleep = jiffies;
wb->congested = wb_congested_get_create(bdi, blkcg_id, gfp);
if (!wb->congested) {
err = -ENOMEM;
goto out_put_bdi;
}
err = fprop_local_init_percpu(&wb->completions, gfp);
if (err)
goto out_put_cong;
for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
err = percpu_counter_init(&wb->stat[i], 0, gfp);
if (err)
goto out_destroy_stat;
}
return 0;
out_destroy_stat:
while (i--)
percpu_counter_destroy(&wb->stat[i]);
fprop_local_destroy_percpu(&wb->completions);
out_put_cong:
wb_congested_put(wb->congested);
out_put_bdi:
if (wb != &bdi->wb)
bdi_put(bdi);
return err;
}
static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
/*
* Remove bdi from the global list and shutdown any threads we have running
*/
static void wb_shutdown(struct bdi_writeback *wb)
{
/* Make sure nobody queues further work */
spin_lock_bh(&wb->work_lock);
if (!test_and_clear_bit(WB_registered, &wb->state)) {
spin_unlock_bh(&wb->work_lock);
return;
}
spin_unlock_bh(&wb->work_lock);
cgwb_remove_from_bdi_list(wb);
/*
* Drain work list and shutdown the delayed_work. !WB_registered
* tells wb_workfn() that @wb is dying and its work_list needs to
* be drained no matter what.
*/
mod_delayed_work(bdi_wq, &wb->dwork, 0);
flush_delayed_work(&wb->dwork);
WARN_ON(!list_empty(&wb->work_list));
}
static void wb_exit(struct bdi_writeback *wb)
{
int i;
WARN_ON(delayed_work_pending(&wb->dwork));
for (i = 0; i < NR_WB_STAT_ITEMS; i++)
percpu_counter_destroy(&wb->stat[i]);
fprop_local_destroy_percpu(&wb->completions);
wb_congested_put(wb->congested);
if (wb != &wb->bdi->wb)
bdi_put(wb->bdi);
}
#ifdef CONFIG_CGROUP_WRITEBACK
#include <linux/memcontrol.h>
/*
* cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
* blkcg->cgwb_list, and memcg->cgwb_list. bdi->cgwb_tree is also RCU
* protected.
*/
static DEFINE_SPINLOCK(cgwb_lock);
static struct workqueue_struct *cgwb_release_wq;
/**
* wb_congested_get_create - get or create a wb_congested
* @bdi: associated bdi
* @blkcg_id: ID of the associated blkcg
* @gfp: allocation mask
*
* Look up the wb_congested for @blkcg_id on @bdi. If missing, create one.
* The returned wb_congested has its reference count incremented. Returns
* NULL on failure.
*/
struct bdi_writeback_congested *
wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
{
struct bdi_writeback_congested *new_congested = NULL, *congested;
struct rb_node **node, *parent;
unsigned long flags;
retry:
spin_lock_irqsave(&cgwb_lock, flags);
node = &bdi->cgwb_congested_tree.rb_node;
parent = NULL;
while (*node != NULL) {
parent = *node;
congested = rb_entry(parent, struct bdi_writeback_congested,
rb_node);
if (congested->blkcg_id < blkcg_id)
node = &parent->rb_left;
else if (congested->blkcg_id > blkcg_id)
node = &parent->rb_right;
else
goto found;
}
if (new_congested) {
/* !found and storage for new one already allocated, insert */
congested = new_congested;
rb_link_node(&congested->rb_node, parent, node);
rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
spin_unlock_irqrestore(&cgwb_lock, flags);
return congested;
}
spin_unlock_irqrestore(&cgwb_lock, flags);
/* allocate storage for new one and retry */
new_congested = kzalloc(sizeof(*new_congested), gfp);
if (!new_congested)
return NULL;
refcount_set(&new_congested->refcnt, 1);
new_congested->__bdi = bdi;
new_congested->blkcg_id = blkcg_id;
goto retry;
found:
refcount_inc(&congested->refcnt);
spin_unlock_irqrestore(&cgwb_lock, flags);
kfree(new_congested);
return congested;
}
/**
* wb_congested_put - put a wb_congested
* @congested: wb_congested to put
*
* Put @congested and destroy it if the refcnt reaches zero.
*/
void wb_congested_put(struct bdi_writeback_congested *congested)
{
unsigned long flags;
if (!refcount_dec_and_lock_irqsave(&congested->refcnt, &cgwb_lock, &flags))
return;
/* bdi might already have been destroyed leaving @congested unlinked */
if (congested->__bdi) {
rb_erase(&congested->rb_node,
&congested->__bdi->cgwb_congested_tree);
congested->__bdi = NULL;
}
spin_unlock_irqrestore(&cgwb_lock, flags);
kfree(congested);
}
static void cgwb_release_workfn(struct work_struct *work)
{
struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
release_work);
struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
mutex_lock(&wb->bdi->cgwb_release_mutex);
wb_shutdown(wb);
css_put(wb->memcg_css);
css_put(wb->blkcg_css);
mutex_unlock(&wb->bdi->cgwb_release_mutex);
/* triggers blkg destruction if no online users left */
blkcg_unpin_online(blkcg);
fprop_local_destroy_percpu(&wb->memcg_completions);
percpu_ref_exit(&wb->refcnt);
wb_exit(wb);
kfree_rcu(wb, rcu);
}
static void cgwb_release(struct percpu_ref *refcnt)
{
struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
refcnt);
queue_work(cgwb_release_wq, &wb->release_work);
}
static void cgwb_kill(struct bdi_writeback *wb)
{
lockdep_assert_held(&cgwb_lock);
WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
list_del(&wb->memcg_node);
list_del(&wb->blkcg_node);
percpu_ref_kill(&wb->refcnt);
}
static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
{
spin_lock_irq(&cgwb_lock);
list_del_rcu(&wb->bdi_node);
spin_unlock_irq(&cgwb_lock);
}
static int cgwb_create(struct backing_dev_info *bdi,
struct cgroup_subsys_state *memcg_css, gfp_t gfp)
{
struct mem_cgroup *memcg;
struct cgroup_subsys_state *blkcg_css;
struct blkcg *blkcg;
struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
struct bdi_writeback *wb;
unsigned long flags;
int ret = 0;
memcg = mem_cgroup_from_css(memcg_css);
blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
blkcg = css_to_blkcg(blkcg_css);
memcg_cgwb_list = &memcg->cgwb_list;
blkcg_cgwb_list = &blkcg->cgwb_list;
/* look up again under lock and discard on blkcg mismatch */
spin_lock_irqsave(&cgwb_lock, flags);
wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
if (wb && wb->blkcg_css != blkcg_css) {
cgwb_kill(wb);
wb = NULL;
}
spin_unlock_irqrestore(&cgwb_lock, flags);
if (wb)
goto out_put;
/* need to create a new one */
wb = kmalloc(sizeof(*wb), gfp);
if (!wb) {
ret = -ENOMEM;
goto out_put;
}
ret = wb_init(wb, bdi, blkcg_css->id, gfp);
if (ret)
goto err_free;
ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
if (ret)
goto err_wb_exit;
ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
if (ret)
goto err_ref_exit;
wb->memcg_css = memcg_css;
wb->blkcg_css = blkcg_css;
INIT_WORK(&wb->release_work, cgwb_release_workfn);
set_bit(WB_registered, &wb->state);
/*
* The root wb determines the registered state of the whole bdi and
* memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
* whether they're still online. Don't link @wb if any is dead.
* See wb_memcg_offline() and wb_blkcg_offline().
*/
ret = -ENODEV;
spin_lock_irqsave(&cgwb_lock, flags);
if (test_bit(WB_registered, &bdi->wb.state) &&
blkcg_cgwb_list->next && memcg_cgwb_list->next) {
/* we might have raced another instance of this function */
ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
if (!ret) {
list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
list_add(&wb->memcg_node, memcg_cgwb_list);
list_add(&wb->blkcg_node, blkcg_cgwb_list);
blkcg_pin_online(blkcg);
css_get(memcg_css);
css_get(blkcg_css);
}
}
spin_unlock_irqrestore(&cgwb_lock, flags);
if (ret) {
if (ret == -EEXIST)
ret = 0;
goto err_fprop_exit;
}
goto out_put;
err_fprop_exit:
fprop_local_destroy_percpu(&wb->memcg_completions);
err_ref_exit:
percpu_ref_exit(&wb->refcnt);
err_wb_exit:
wb_exit(wb);
err_free:
kfree(wb);
out_put:
css_put(blkcg_css);
return ret;
}
/**
* wb_get_lookup - get wb for a given memcg
* @bdi: target bdi
* @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
*
* Try to get the wb for @memcg_css on @bdi. The returned wb has its
* refcount incremented.
*
* This function uses css_get() on @memcg_css and thus expects its refcnt
* to be positive on invocation. IOW, rcu_read_lock() protection on
* @memcg_css isn't enough. try_get it before calling this function.
*
* A wb is keyed by its associated memcg. As blkcg implicitly enables
* memcg on the default hierarchy, memcg association is guaranteed to be
* more specific (equal or descendant to the associated blkcg) and thus can
* identify both the memcg and blkcg associations.
*
* Because the blkcg associated with a memcg may change as blkcg is enabled
* and disabled closer to root in the hierarchy, each wb keeps track of
* both the memcg and blkcg associated with it and verifies the blkcg on
* each lookup. On mismatch, the existing wb is discarded and a new one is
* created.
*/
struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
struct cgroup_subsys_state *memcg_css)
{
struct bdi_writeback *wb;
if (!memcg_css->parent)
return &bdi->wb;
rcu_read_lock();
wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
if (wb) {
struct cgroup_subsys_state *blkcg_css;
/* see whether the blkcg association has changed */
blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
wb = NULL;
css_put(blkcg_css);
}
rcu_read_unlock();
return wb;
}
/**
* wb_get_create - get wb for a given memcg, create if necessary
* @bdi: target bdi
* @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
* @gfp: allocation mask to use
*
* Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
* create one. See wb_get_lookup() for more details.
*/
struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
struct cgroup_subsys_state *memcg_css,
gfp_t gfp)
{
struct bdi_writeback *wb;
might_sleep_if(gfpflags_allow_blocking(gfp));
if (!memcg_css->parent)
return &bdi->wb;
do {
wb = wb_get_lookup(bdi, memcg_css);
} while (!wb && !cgwb_create(bdi, memcg_css, gfp));
return wb;
}
static int cgwb_bdi_init(struct backing_dev_info *bdi)
{
int ret;
INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
bdi->cgwb_congested_tree = RB_ROOT;
mutex_init(&bdi->cgwb_release_mutex);
init_rwsem(&bdi->wb_switch_rwsem);
ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
if (!ret) {
bdi->wb.memcg_css = &root_mem_cgroup->css;
bdi->wb.blkcg_css = blkcg_root_css;
}
return ret;
}
static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
{
struct radix_tree_iter iter;
void **slot;
struct bdi_writeback *wb;
WARN_ON(test_bit(WB_registered, &bdi->wb.state));
spin_lock_irq(&cgwb_lock);
radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
cgwb_kill(*slot);
spin_unlock_irq(&cgwb_lock);
mutex_lock(&bdi->cgwb_release_mutex);
spin_lock_irq(&cgwb_lock);
while (!list_empty(&bdi->wb_list)) {
wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
bdi_node);
spin_unlock_irq(&cgwb_lock);
wb_shutdown(wb);
spin_lock_irq(&cgwb_lock);
}
spin_unlock_irq(&cgwb_lock);
mutex_unlock(&bdi->cgwb_release_mutex);
}
/**
* wb_memcg_offline - kill all wb's associated with a memcg being offlined
* @memcg: memcg being offlined
*
* Also prevents creation of any new wb's associated with @memcg.
*/
void wb_memcg_offline(struct mem_cgroup *memcg)
{
struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
struct bdi_writeback *wb, *next;
spin_lock_irq(&cgwb_lock);
list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
cgwb_kill(wb);
memcg_cgwb_list->next = NULL; /* prevent new wb's */
spin_unlock_irq(&cgwb_lock);
}
/**
* wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
* @blkcg: blkcg being offlined
*
* Also prevents creation of any new wb's associated with @blkcg.
*/
void wb_blkcg_offline(struct blkcg *blkcg)
{
struct bdi_writeback *wb, *next;
spin_lock_irq(&cgwb_lock);
list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
cgwb_kill(wb);
blkcg->cgwb_list.next = NULL; /* prevent new wb's */
spin_unlock_irq(&cgwb_lock);
}
static void cgwb_bdi_exit(struct backing_dev_info *bdi)
{
struct rb_node *rbn;
spin_lock_irq(&cgwb_lock);
while ((rbn = rb_first(&bdi->cgwb_congested_tree))) {
struct bdi_writeback_congested *congested =
rb_entry(rbn, struct bdi_writeback_congested, rb_node);
rb_erase(rbn, &bdi->cgwb_congested_tree);
congested->__bdi = NULL; /* mark @congested unlinked */
}
spin_unlock_irq(&cgwb_lock);
}
static void cgwb_bdi_register(struct backing_dev_info *bdi)
{
spin_lock_irq(&cgwb_lock);
list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
spin_unlock_irq(&cgwb_lock);
}
static int __init cgwb_init(void)
{
/*
* There can be many concurrent release work items overwhelming
* system_wq. Put them in a separate wq and limit concurrency.
* There's no point in executing many of these in parallel.
*/
cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
if (!cgwb_release_wq)
return -ENOMEM;
return 0;
}
subsys_initcall(cgwb_init);
#else /* CONFIG_CGROUP_WRITEBACK */
static int cgwb_bdi_init(struct backing_dev_info *bdi)
{
int err;
bdi->wb_congested = kzalloc(sizeof(*bdi->wb_congested), GFP_KERNEL);
if (!bdi->wb_congested)
return -ENOMEM;
refcount_set(&bdi->wb_congested->refcnt, 1);
err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
if (err) {
wb_congested_put(bdi->wb_congested);
return err;
}
return 0;
}
static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
static void cgwb_bdi_exit(struct backing_dev_info *bdi)
{
wb_congested_put(bdi->wb_congested);
}
static void cgwb_bdi_register(struct backing_dev_info *bdi)
{
list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
}
static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
{
list_del_rcu(&wb->bdi_node);
}
#endif /* CONFIG_CGROUP_WRITEBACK */
static int bdi_init(struct backing_dev_info *bdi)
{
int ret;
bdi->dev = NULL;
kref_init(&bdi->refcnt);
bdi->min_ratio = 0;
bdi->max_ratio = 100;
bdi->max_prop_frac = FPROP_FRAC_BASE;
INIT_LIST_HEAD(&bdi->bdi_list);
INIT_LIST_HEAD(&bdi->wb_list);
init_waitqueue_head(&bdi->wb_waitq);
ret = cgwb_bdi_init(bdi);
return ret;
}
struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id)
{
struct backing_dev_info *bdi;
bdi = kmalloc_node(sizeof(struct backing_dev_info),
gfp_mask | __GFP_ZERO, node_id);
if (!bdi)
return NULL;
if (bdi_init(bdi)) {
kfree(bdi);
return NULL;
}
return bdi;
}
EXPORT_SYMBOL(bdi_alloc_node);
static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
{
struct rb_node **p = &bdi_tree.rb_node;
struct rb_node *parent = NULL;
struct backing_dev_info *bdi;
lockdep_assert_held(&bdi_lock);
while (*p) {
parent = *p;
bdi = rb_entry(parent, struct backing_dev_info, rb_node);
if (bdi->id > id)
p = &(*p)->rb_left;
else if (bdi->id < id)
p = &(*p)->rb_right;
else
break;
}
if (parentp)
*parentp = parent;
return p;
}
/**
* bdi_get_by_id - lookup and get bdi from its id
* @id: bdi id to lookup
*
* Find bdi matching @id and get it. Returns NULL if the matching bdi
* doesn't exist or is already unregistered.
*/
struct backing_dev_info *bdi_get_by_id(u64 id)
{
struct backing_dev_info *bdi = NULL;
struct rb_node **p;
spin_lock_bh(&bdi_lock);
p = bdi_lookup_rb_node(id, NULL);
if (*p) {
bdi = rb_entry(*p, struct backing_dev_info, rb_node);
bdi_get(bdi);
}
spin_unlock_bh(&bdi_lock);
return bdi;
}
int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
{
struct device *dev;
struct rb_node *parent, **p;
if (bdi->dev) /* The driver needs to use separate queues per device */
return 0;
dev = device_create_vargs(bdi_class, NULL, MKDEV(0, 0), bdi, fmt, args);
if (IS_ERR(dev))
return PTR_ERR(dev);
cgwb_bdi_register(bdi);
bdi->dev = dev;
bdi_debug_register(bdi, dev_name(dev));
set_bit(WB_registered, &bdi->wb.state);
spin_lock_bh(&bdi_lock);
bdi->id = ++bdi_id_cursor;
p = bdi_lookup_rb_node(bdi->id, &parent);
rb_link_node(&bdi->rb_node, parent, p);
rb_insert_color(&bdi->rb_node, &bdi_tree);
list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
spin_unlock_bh(&bdi_lock);
trace_writeback_bdi_register(bdi);
return 0;
}
EXPORT_SYMBOL(bdi_register_va);
int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
{
va_list args;
int ret;
va_start(args, fmt);
ret = bdi_register_va(bdi, fmt, args);
va_end(args);
return ret;
}
EXPORT_SYMBOL(bdi_register);
int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner)
{
int rc;
rc = bdi_register(bdi, "%u:%u", MAJOR(owner->devt), MINOR(owner->devt));
if (rc)
return rc;
/* Leaking owner reference... */
WARN_ON(bdi->owner);
bdi->owner = owner;
get_device(owner);
return 0;
}
EXPORT_SYMBOL(bdi_register_owner);
/*
* Remove bdi from bdi_list, and ensure that it is no longer visible
*/
static void bdi_remove_from_list(struct backing_dev_info *bdi)
{
spin_lock_bh(&bdi_lock);
rb_erase(&bdi->rb_node, &bdi_tree);
list_del_rcu(&bdi->bdi_list);
spin_unlock_bh(&bdi_lock);
synchronize_rcu_expedited();
}
void bdi_unregister(struct backing_dev_info *bdi)
{
/* make sure nobody finds us on the bdi_list anymore */
bdi_remove_from_list(bdi);
wb_shutdown(&bdi->wb);
cgwb_bdi_unregister(bdi);
if (bdi->dev) {
bdi_debug_unregister(bdi);
device_unregister(bdi->dev);
bdi->dev = NULL;
}
if (bdi->owner) {
put_device(bdi->owner);
bdi->owner = NULL;
}
}
static void release_bdi(struct kref *ref)
{
struct backing_dev_info *bdi =
container_of(ref, struct backing_dev_info, refcnt);
if (test_bit(WB_registered, &bdi->wb.state))
bdi_unregister(bdi);
WARN_ON_ONCE(bdi->dev);
wb_exit(&bdi->wb);
cgwb_bdi_exit(bdi);
kfree(bdi);
}
void bdi_put(struct backing_dev_info *bdi)
{
kref_put(&bdi->refcnt, release_bdi);
}
EXPORT_SYMBOL(bdi_put);
static wait_queue_head_t congestion_wqh[2] = {
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
};
static atomic_t nr_wb_congested[2];
void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
{
wait_queue_head_t *wqh = &congestion_wqh[sync];
enum wb_congested_state bit;
bit = sync ? WB_sync_congested : WB_async_congested;
if (test_and_clear_bit(bit, &congested->state))
atomic_dec(&nr_wb_congested[sync]);
smp_mb__after_atomic();
if (waitqueue_active(wqh))
wake_up(wqh);
}
EXPORT_SYMBOL(clear_wb_congested);
void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
{
enum wb_congested_state bit;
bit = sync ? WB_sync_congested : WB_async_congested;
if (!test_and_set_bit(bit, &congested->state))
atomic_inc(&nr_wb_congested[sync]);
}
EXPORT_SYMBOL(set_wb_congested);
/**
* congestion_wait - wait for a backing_dev to become uncongested
* @sync: SYNC or ASYNC IO
* @timeout: timeout in jiffies
*
* Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
* write congestion. If no backing_devs are congested then just wait for the
* next write to be completed.
*/
long congestion_wait(int sync, long timeout)
{
long ret;
unsigned long start = jiffies;
DEFINE_WAIT(wait);
wait_queue_head_t *wqh = &congestion_wqh[sync];
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
ret = io_schedule_timeout(timeout);
finish_wait(wqh, &wait);
trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
jiffies_to_usecs(jiffies - start));
return ret;
}
EXPORT_SYMBOL(congestion_wait);
/**
* wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
* @sync: SYNC or ASYNC IO
* @timeout: timeout in jiffies
*
* In the event of a congested backing_dev (any backing_dev) this waits
* for up to @timeout jiffies for either a BDI to exit congestion of the
* given @sync queue or a write to complete.
*
* The return value is 0 if the sleep is for the full timeout. Otherwise,
* it is the number of jiffies that were still remaining when the function
* returned. return_value == timeout implies the function did not sleep.
*/
long wait_iff_congested(int sync, long timeout)
{
long ret;
unsigned long start = jiffies;
DEFINE_WAIT(wait);
wait_queue_head_t *wqh = &congestion_wqh[sync];
/*
* If there is no congestion, yield if necessary instead
* of sleeping on the congestion queue
*/
if (atomic_read(&nr_wb_congested[sync]) == 0) {
cond_resched();
/* In case we scheduled, work out time remaining */
ret = timeout - (jiffies - start);
if (ret < 0)
ret = 0;
goto out;
}
/* Sleep until uncongested or a write happens */
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
ret = io_schedule_timeout(timeout);
finish_wait(wqh, &wait);
out:
trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
jiffies_to_usecs(jiffies - start));
return ret;
}
EXPORT_SYMBOL(wait_iff_congested);