linux-kernel - [PATCH 24/48] writeback: let balance_dirty_pages() work on the matching cgroup bdi

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Date:	Mon, 23 Mar 2015 00:54:35 -0400
From:	Tejun Heo <tj@...nel.org>
To:	axboe@...nel.dk
Cc:	linux-kernel@...r.kernel.org, jack@...e.cz, hch@...radead.org,
	hannes@...xchg.org, linux-fsdevel@...r.kernel.org,
	vgoyal@...hat.com, lizefan@...wei.com, cgroups@...r.kernel.org,
	linux-mm@...ck.org, mhocko@...e.cz, clm@...com,
	fengguang.wu@...el.com, david@...morbit.com, gthelen@...gle.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 24/48] 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: Tejun Heo <tj@...nel.org>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Jan Kara <jack@...e.cz>
---
 mm/page-writeback.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index d5635cf..bfbd8d2 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -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);
 
-- 
2.1.0

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