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Commit dfb8ae56 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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writeback: let balance_dirty_pages() work on the matching cgroup bdi_writeback 



Currently, balance_dirty_pages() always work on bdi->wb.  This patch
updates it to work on the wb (bdi_writeback) matching memcg and blkcg
of the current task as that's what the inode is being dirtied against.

balance_dirty_pages_ratelimited() now pins the current wb and passes
it to balance_dirty_pages().

As no filesystem has FS_CGROUP_WRITEBACK yet, this doesn't lead to
visible behavior differences.

v2: Updated for per-inode wb association.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 91018134

mm/page-writeback.c

+13 −5
Original line number Diff line number Diff line
@@ -1337,6 +1337,7 @@ static inline void wb_dirty_limits(struct bdi_writeback *wb, 
 * perform some writeout.

 */

static void balance_dirty_pages(struct address_space *mapping,

				struct bdi_writeback *wb,

				unsigned long pages_dirtied)

{

	unsigned long nr_reclaimable;	/* = file_dirty + unstable_nfs */
@@ -1352,8 +1353,7 @@ static void balance_dirty_pages(struct address_space *mapping, 
	unsigned long task_ratelimit;

	unsigned long dirty_ratelimit;

	unsigned long pos_ratio;

	struct backing_dev_info *bdi = inode_to_bdi(mapping->host);

	struct bdi_writeback *wb = &bdi->wb;

	struct backing_dev_info *bdi = wb->bdi;

	bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT;

	unsigned long start_time = jiffies;
@@ -1575,14 +1575,20 @@ DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; 
 */

void balance_dirty_pages_ratelimited(struct address_space *mapping)

{

	struct backing_dev_info *bdi = inode_to_bdi(mapping->host);

	struct bdi_writeback *wb = &bdi->wb;

	struct inode *inode = mapping->host;

	struct backing_dev_info *bdi = inode_to_bdi(inode);

	struct bdi_writeback *wb = NULL;

	int ratelimit;

	int *p;



	if (!bdi_cap_account_dirty(bdi))

		return;



	if (inode_cgwb_enabled(inode))

		wb = wb_get_create_current(bdi, GFP_KERNEL);

	if (!wb)

		wb = &bdi->wb;



	ratelimit = current->nr_dirtied_pause;

	if (wb->dirty_exceeded)

		ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10));
@@ -1616,7 +1622,9 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping) 
	preempt_enable();



	if (unlikely(current->nr_dirtied >= ratelimit))

		balance_dirty_pages(mapping, current->nr_dirtied);

		balance_dirty_pages(mapping, wb, current->nr_dirtied);



	wb_put(wb);

}

EXPORT_SYMBOL(balance_dirty_pages_ratelimited);