path: root/mm/backing-dev.c

// SPDX-License-Identifier: GPL-2.0-only

#include <linux/blkdev.h>
#include <linux/wait.h>
#include <linux/rbtree.h>
#include <linux/kthread.h>
#include <linux/backing-dev.h>
#include <linux/blk-cgroup.h>
#include <linux/freezer.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/mm.h>
#include <linux/sched/mm.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/writeback.h>
#include <linux/device.h>
#include <trace/events/writeback.h>
#include "internal.h"

struct backing_dev_info noop_backing_dev_info;
EXPORT_SYMBOL_GPL(noop_backing_dev_info);

static 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>

struct wb_stats {
	unsigned long nr_dirty;
	unsigned long nr_io;
	unsigned long nr_more_io;
	unsigned long nr_dirty_time;
	unsigned long nr_writeback;
	unsigned long nr_reclaimable;
	unsigned long nr_dirtied;
	unsigned long nr_written;
	unsigned long dirty_thresh;
	unsigned long wb_thresh;
};

static struct dentry *bdi_debug_root;

static void bdi_debug_init(void)
{
	bdi_debug_root = debugfs_create_dir("bdi", NULL);
}

static void collect_wb_stats(struct wb_stats *stats,
			     struct bdi_writeback *wb)
{
	struct inode *inode;

	spin_lock(&wb->list_lock);
	list_for_each_entry(inode, &wb->b_dirty, i_io_list)
		stats->nr_dirty++;
	list_for_each_entry(inode, &wb->b_io, i_io_list)
		stats->nr_io++;
	list_for_each_entry(inode, &wb->b_more_io, i_io_list)
		stats->nr_more_io++;
	list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
		if (inode->i_state & I_DIRTY_TIME)
			stats->nr_dirty_time++;
	spin_unlock(&wb->list_lock);

	stats->nr_writeback += wb_stat(wb, WB_WRITEBACK);
	stats->nr_reclaimable += wb_stat(wb, WB_RECLAIMABLE);
	stats->nr_dirtied += wb_stat(wb, WB_DIRTIED);
	stats->nr_written += wb_stat(wb, WB_WRITTEN);
	stats->wb_thresh += wb_calc_thresh(wb, stats->dirty_thresh);
}

#ifdef CONFIG_CGROUP_WRITEBACK
static void bdi_collect_stats(struct backing_dev_info *bdi,
			      struct wb_stats *stats)
{
	struct bdi_writeback *wb;

	rcu_read_lock();
	list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node) {
		if (!wb_tryget(wb))
			continue;

		collect_wb_stats(stats, wb);
		wb_put(wb);
	}
	rcu_read_unlock();
}
#else
static void bdi_collect_stats(struct backing_dev_info *bdi,
			      struct wb_stats *stats)
{
	collect_wb_stats(stats, &bdi->wb);
}
#endif

static int bdi_debug_stats_show(struct seq_file *m, void *v)
{
	struct backing_dev_info *bdi = m->private;
	unsigned long background_thresh;
	unsigned long dirty_thresh;
	struct wb_stats stats;
	unsigned long tot_bw;

	global_dirty_limits(&background_thresh, &dirty_thresh);

	memset(&stats, 0, sizeof(stats));
	stats.dirty_thresh = dirty_thresh;
	bdi_collect_stats(bdi, &stats);
	tot_bw = atomic_long_read(&bdi->tot_write_bandwidth