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Commit bdc24917 authored by Dennis Zhou (Facebook)'s avatar Dennis Zhou (Facebook) Committed by Jens Axboe
Browse files

blkcg: associate writeback bios with a blkg 



One of the goals of this series is to remove a separate reference to
the css of the bio. This can and should be accessed via bio_blkcg. In
this patch, the wbc_init_bio call is changed such that it must be called
after a queue has been associated with the bio.

Signed-off-by: default avatarDennis Zhou <dennisszhou@gmail.com>
Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 74b7c02a

Documentation/admin-guide/cgroup-v2.rst

+5 −3
Original line number Diff line number Diff line
@@ -1857,8 +1857,10 @@ following two functions. 


  wbc_init_bio(@wbc, @bio)

	Should be called for each bio carrying writeback data and

	associates the bio with the inode's owner cgroup.  Can be

	called anytime between bio allocation and submission.

	associates the bio with the inode's owner cgroup and the

	corresponding request queue.  This must be called after

	a queue (device) has been associated with the bio and

	before submission.



  wbc_account_io(@wbc, @page, @bytes)

	Should be called for each data segment being written out.
@@ -1877,7 +1879,7 @@ the configuration, the bio may be executed at a lower priority and if 
the writeback session is holding shared resources, e.g. a journal

entry, may lead to priority inversion.  There is no one easy solution

for the problem.  Filesystems can try to work around specific problem

cases by skipping wbc_init_bio() or using bio_associate_blkcg()

cases by skipping wbc_init_bio() or using bio_associate_create_blkg()

directly.

fs/buffer.c

+5 −5
Original line number Diff line number Diff line
@@ -3060,11 +3060,6 @@ static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh, 
	 */

	bio = bio_alloc(GFP_NOIO, 1);



	if (wbc) {

		wbc_init_bio(wbc, bio);

		wbc_account_io(wbc, bh->b_page, bh->b_size);

	}



	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);

	bio_set_dev(bio, bh->b_bdev);

	bio->bi_write_hint = write_hint;
@@ -3084,6 +3079,11 @@ static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh, 
		op_flags |= REQ_PRIO;

	bio_set_op_attrs(bio, op, op_flags);



	if (wbc) {

		wbc_init_bio(wbc, bio);

		wbc_account_io(wbc, bh->b_page, bh->b_size);

	}



	submit_bio(bio);

	return 0;

}

fs/ext4/page-io.c

+1 −1
Original line number Diff line number Diff line
@@ -374,13 +374,13 @@ static int io_submit_init_bio(struct ext4_io_submit *io, 
	bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);

	if (!bio)

		return -ENOMEM;

	wbc_init_bio(io->io_wbc, bio);

	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);

	bio_set_dev(bio, bh->b_bdev);

	bio->bi_end_io = ext4_end_bio;

	bio->bi_private = ext4_get_io_end(io->io_end);

	io->io_bio = bio;

	io->io_next_block = bh->b_blocknr;

	wbc_init_bio(io->io_wbc, bio);

	return 0;

}

include/linux/writeback.h

+3 −2
Original line number Diff line number Diff line
@@ -246,7 +246,8 @@ static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc, 
 *

 * @bio is a part of the writeback in progress controlled by @wbc.  Perform

 * writeback specific initialization.  This is used to apply the cgroup

 * writeback context.

 * writeback context.  Must be called after the bio has been associated with

 * a device.

 */

static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)

{
@@ -257,7 +258,7 @@ static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio) 
	 * regular writeback instead of writing things out itself.

	 */

	if (wbc->wb)

		bio_associate_blkcg(bio, wbc->wb->blkcg_css);

		bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css);

}



#else	/* CONFIG_CGROUP_WRITEBACK */