[PATCH 47/49] buffer, writeback: make __block_write_full_page() honor cgroup writeback

Tejun Heo
2015-04-06T20:00:47Z

[__]block_write_full_page() is used to implement ->writepage in
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 from the inode; however,
[__]block_write_full_page() currently ignores the blkcg indicated by
inode and issues all bio's without explicit blkcg association.

This patch adds submit_bh_blkcg() which associates the bio with the
specified blkio cgroup before issuing and uses it in
__block_write_full_page() so that the issued bio's are associated with
inode_to_wb_blkcg_css(inode).

v2: Updated for per-inode wb association.

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>
---
fs/buffer.c | 26 ++++++++++++++++++++------
include/linux/backing-dev.h | 12 ++++++++++++
2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 4aa1dc2..f2d594c 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -30,6 +30,7 @@
#include <linux/quotaops.h>
#include <linux/highmem.h>
#include <linux/export.h>
+#include <linux/backing-dev.h>
#include <linux/writeback.h>
#include <linux/hash.h>
#include <linux/suspend.h>
@@ -44,6 +45,9 @@
#include <trace/events/block.h>

static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
+static int submit_bh_blkcg(int rw, struct buffer_head *bh,
+ unsigned long bio_flags,
+ struct cgroup_subsys_state *blkcg_css);

#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)

@@ -1704,8 +1708,8 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
struct buffer_head *bh, *head;
unsigned int blocksize, bbits;
int nr_underway = 0;
- int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
- WRITE_SYNC : WRITE);
+ int write_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
+ struct cgroup_subsys_state *blkcg_css = inode_to_wb_blkcg_css(inode);

head = create_page_buffers(page, inode,
(1 << BH_Dirty)|(1 << BH_Uptodate));
@@ -1794,7 +1798,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
do {
struct buffer_head *next = bh->b_this_page;
if (buffer_async_write(bh)) {
- submit_bh(write_op, bh);
+ submit_bh_blkcg(write_op, bh, 0, blkcg_css);
nr_underway++;
}
bh = next;
@@ -1848,7 +1852,7 @@ recover:
struct buffer_head *next = bh->b_this_page;
if (buffer_async_write(bh)) {
clear_buffer_dirty(bh);
- submit_bh(write_op, bh);
+ submit_bh_blkcg(write_op, bh, 0, blkcg_css);
nr_underway++;
}
bh = next;
@@ -3017,7 +3021,9 @@ void guard_bio_eod(int rw, struct bio *bio)
}
}

-int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
+static int submit_bh_blkcg(int rw, struct buffer_head *bh,
+ unsigned long bio_flags,
+ struct cgroup_subsys_state *blkcg_css)
{
struct bio *bio;
int ret = 0;
@@ -3040,6 +3046,9 @@ int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
*/
bio = bio_alloc(GFP_NOIO, 1);

+ if (blkcg_css)
+ bio_associate_blkcg(bio, blkcg_css);
+
bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
bio->bi_bdev = bh->b_bdev;
bio->bi_io_vec[0].bv_page = bh->b_page;
@@ -3070,11 +3079,16 @@ int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
bio_put(bio);
return ret;
}
+
+int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
+{
+ return submit_bh_blkcg(rw, bh, bio_flags, NULL);
+}
EXPORT_SYMBOL_GPL(_submit_bh);

int submit_bh(int rw, struct buffer_head *bh)
{
- return _submit_bh(rw, bh, 0);
+ return submit_bh_blkcg(rw, bh, 0, NULL);
}
EXPORT_SYMBOL(submit_bh);

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 9cc11e5..e9d7373 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -393,6 +393,12 @@ static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
return inode->i_wb;
}

+static inline struct cgroup_subsys_state *
+inode_to_wb_blkcg_css(struct inode *inode)
+{
+ return inode_to_wb(inode)->blkcg_css;
+}
+
struct wb_iter {
int start_blkcg_id;
struct radix_tree_iter tree_iter;
@@ -510,6 +516,12 @@ static inline void wb_blkcg_offline(struct blkcg *blkcg)
{
}

+static inline struct cgroup_subsys_state *
+inode_to_wb_blkcg_css(struct inode *inode)
+{
+ return blkcg_root_css;
+}
+
struct wb_iter {
int next_id;
};
--
2.1.0