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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: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dennis Zhou 2018-12-05 12:10:34 -05:00 committed by Jens Axboe
parent 6a7f6d86a5
commit fd42df305f
6 changed files with 37 additions and 11 deletions
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8
Documentation/admin-guide/cgroup-v2.rst
View File

@ -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.

18
block/bio.c
View File

@ -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

10
fs/buffer.c
View File

@ -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;
}

2
fs/ext4/page-io.c
View File

@ -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;
}

5
include/linux/bio.h
View File

@ -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) { }

5
include/linux/writeback.h
View File

@ -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 */