writeback: make wakeup_flusher_threads() handle multiple bdi_writeback's

}

EXPORT_SYMBOL_GPL(inode_congested);

/**

 * wb_split_bdi_pages - split nr_pages to write according to bandwidth

 * @wb: target bdi_writeback to split @nr_pages to

 * @nr_pages: number of pages to write for the whole bdi

 *

 * Split @wb's portion of @nr_pages according to @wb's write bandwidth in

 * relation to the total write bandwidth of all wb's w/ dirty inodes on

 * @wb->bdi.

 */

static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)

{

	unsigned long this_bw = wb->avg_write_bandwidth;

	unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth);

	if (nr_pages == LONG_MAX)

		return LONG_MAX;

	/*

	 * This may be called on clean wb's and proportional distribution

	 * may not make sense, just use the original @nr_pages in those

	 * cases.  In general, we wanna err on the side of writing more.

	 */

	if (!tot_bw || this_bw >= tot_bw)

		return nr_pages;

	else

		return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw);

}

#else	/* CONFIG_CGROUP_WRITEBACK */

static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)

{

	return nr_pages;

}

#endif	/* CONFIG_CGROUP_WRITEBACK */

void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,

		nr_pages = get_nr_dirty_pages();

	rcu_read_lock();

	list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)

		wb_start_writeback(&bdi->wb, nr_pages, false, reason);

	list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {

		struct bdi_writeback *wb;

		struct wb_iter iter;

		if (!bdi_has_dirty_io(bdi))

			continue;

		bdi_for_each_wb(wb, bdi, &iter, 0)

			wb_start_writeback(wb, wb_split_bdi_pages(wb, nr_pages),

					   false, reason);

	}

	rcu_read_unlock();

}