static void cgwb_bdi_destroy(struct backing_dev_info *bdi)
{
struct radix_tree_iter iter;
struct rb_node *rbn;
void **slot;
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);
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);
/*
* All cgwb's and their congested states must be shutdown and
* released before returning. Drain the usage counter to wait for
* all cgwb's and cgwb_congested's ever created on @bdi.
*/
atomic_dec(&bdi->usage_cnt);
wait_event(cgwb_release_wait, !atomic_read(&bdi->usage_cnt));
}
/**
* 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);
}
/**
* 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 = mem_cgroup_cgwb_list(memcg);
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);
}
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);
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);
}
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 = mem_cgroup_cgwb_list(memcg);
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)
return -ENOMEM;
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) {
atomic_inc(&bdi->usage_cnt);
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);
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;
}