[PATCH 44/45] mpage: make __mpage_writepage() honor cgroup writeback

[Tejun Heo <tj@kernel.org>]

__mpage_writepage() is used to implement mpage_writepages() which in
turn is used for ->writepages() of various filesystems.  All writeback
logic is now updated to handle cgroup writeback and the block cgroup
to issue IOs for is encoded in writeback_control and can be retrieved
using wbc_blkcg_css(); however, __mpage_writepage() currently ignores
the blkcg indicated by wbc and issues all bio's without explicit blkcg
association.

This patch updates __mpage_writepage() so that the issued bio's are
associated with wbc_blkcg_css().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
---
 fs/mpage.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/mpage.c b/fs/mpage.c
index 587c7ed..84921b2 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -595,6 +595,8 @@ page_is_mapped:
 
 alloc_new:
 	if (bio == NULL) {
+		struct cgroup_subsys_state *blkcg_css;
+
 		if (first_unmapped == blocks_per_page) {
 			if (!bdev_write_page(bdev, blocks[0] << (blkbits - 9),
 								page, wbc)) {
@@ -606,6 +608,10 @@ alloc_new:
 				bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH);
 		if (bio == NULL)
 			goto confused;
+
+		blkcg_css = wbc_blkcg_css(wbc);
+		if (blkcg_css)
+			bio_associate_blkcg(bio, blkcg_css);
 	}
 
 	/*
-- 
2.1.0