linux-kernel - Re: [PATCHSET v2] cgroup, writeback, btrfs: make sure btrfs issues metadata IOs from the root cgroup

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Date:   Wed, 29 Nov 2017 17:56:08 +0100
From:   Jan Kara <jack@...e.cz>
To:     Tejun Heo <tj@...nel.org>
Cc:     jack@...e.cz, axboe@...nel.dk, clm@...com, jbacik@...com,
        kernel-team@...com, linux-kernel@...r.kernel.org,
        linux-btrfs@...r.kernel.org
Subject: Re: [PATCHSET v2] cgroup, writeback, btrfs: make sure btrfs issues
 metadata IOs from the root cgroup

Hi Tejun,

What has happened with this patch set?

Honza

On Tue 10-10-17 08:54:36, Tejun Heo wrote:
> Changes from the last version are
> 
> * blkcg_root_css exported to fix build breakage on modular btrfs.
> 
> * Use ext4_should_journal_data() test instead of
>   EXT4_MOUNT_JOURNAL_DATA.
> 
> * Separated out create_bh_bio() and used it to implement
>   submit_bh_blkcg_css() as suggested by Jan.
> 
> btrfs has different ways to issue metadata IOs and may end up issuing
> metadata or otherwise shared IOs from a non-root cgroup, which can
> lead to priority inversion and ineffective IO isolation.
> 
> This patchset makes sure that btrfs issues all metadata and shared IOs
> from the root cgroup by exempting btree_inodes from cgroup writeback
> and explicitly associating shared IOs with the root cgroup.
> 
> This patchset containst he following three patches
> 
>  [PATCH 1/5] blkcg: export blkcg_root_css
>  [PATCH 2/5] cgroup, writeback: replace SB_I_CGROUPWB with per-inode
>  [PATCH 3/5] buffer_head: separate out create_bh_bio() from
>  [PATCH 4/5] cgroup, buffer_head: implement submit_bh_blkcg_css()
>  [PATCH 5/5] btrfs: ensure that metadata and flush are issued from the
> 
> and is also available in the following git branch
> 
>  git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-cgroup-btrfs-metadata-v2
> 
> diffstat follows.  Thanks.
> 
>  block/blk-cgroup.c          |    1 +
>  fs/block_dev.c              |    3 +--
>  fs/btrfs/check-integrity.c  |    2 +-
>  fs/btrfs/disk-io.c          |    4 ++++
>  fs/btrfs/ioctl.c            |    6 +++++-
>  fs/btrfs/super.c            |    1 -
>  fs/buffer.c                 |   42 ++++++++++++++++++++++++++++++++++--------
>  fs/ext2/inode.c             |    3 ++-
>  fs/ext2/super.c             |    1 -
>  fs/ext4/inode.c             |    5 ++++-
>  fs/ext4/super.c             |    2 --
>  include/linux/backing-dev.h |    2 +-
>  include/linux/buffer_head.h |    3 +++
>  include/linux/fs.h          |    3 ++-
>  14 files changed, 58 insertions(+), 20 deletions(-)
> 
> --
> tejun
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR