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blkcg: associate writeback bios with a blkg

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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: Dennis Zhou <dennisszhou@gmail.com>
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 (Facebook)
2018-09-11 14:41:32 -04:00
committed by Jens Axboe
parent 74b7c02a9b
commit bdc2491708
4 changed files with 14 additions and 11 deletions
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8
Documentation/admin-guide/cgroup-v2.rst
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@@ -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.