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Commit fd42df30 authored by Dennis Zhou's avatar Dennis Zhou 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, wbc_init_bio() now requires a bio to have a device
associated with it.

Signed-off-by: default avatarDennis Zhou <dennis@kernel.org>
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 6a7f6d86

Documentation/admin-guide/cgroup-v2.rst

+5 −3
Original line number Diff line number Diff line
@@ -1879,8 +1879,10 @@ 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.
@@ -1899,7 +1901,7 @@ 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() and using bio_associate_blkg()

directly.

block/bio.c

+18 −0
Original line number Diff line number Diff line
@@ -2034,6 +2034,24 @@ static void __bio_associate_blkg_from_css(struct bio *bio, 
	rcu_read_unlock();

}



/**

 * bio_associate_blkg_from_css - associate a bio with a specified css

 * @bio: target bio

 * @css: target css

 *

 * Associate @bio with the blkg found by combining the css's blkg and the

 * request_queue of the @bio.  This takes a reference on the css that will

 * be put upon freeing of @bio.

 */

void bio_associate_blkg_from_css(struct bio *bio,

				 struct cgroup_subsys_state *css)

{

	css_get(css);

	bio->bi_css = css;

	__bio_associate_blkg_from_css(bio, css);

}

EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);



#ifdef CONFIG_MEMCG

/**

 * bio_associate_blkg_from_page - associate a bio with the page's blkg

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/bio.h

+5 −0
Original line number Diff line number Diff line
@@ -515,6 +515,8 @@ static inline void bio_associate_blkg_from_page(struct bio *bio, 
int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css);

void bio_disassociate_blkg(struct bio *bio);

void bio_associate_blkg(struct bio *bio);

void bio_associate_blkg_from_css(struct bio *bio,

				 struct cgroup_subsys_state *css);

void bio_disassociate_task(struct bio *bio);

void bio_clone_blkcg_association(struct bio *dst, struct bio *src);

#else	/* CONFIG_BLK_CGROUP */
@@ -522,6 +524,9 @@ static inline int bio_associate_blkcg(struct bio *bio, 
			struct cgroup_subsys_state *blkcg_css) { return 0; }

static inline void bio_disassociate_blkg(struct bio *bio) { }

static inline void bio_associate_blkg(struct bio *bio) { }

static inline void bio_associate_blkg_from_css(struct bio *bio,

					       struct cgroup_subsys_state *css)

{ }

static inline void bio_disassociate_task(struct bio *bio) { }

static inline void bio_clone_blkcg_association(struct bio *dst,

			struct bio *src) { }