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Date:	Wed,  4 Jul 2012 15:21:49 +0300
From:	Artem Bityutskiy <>
To:	Theodore Tso <>, Jan Kara <>
Cc:	Linux FS Maling List <>,
	Linux Kernel Maling List <>,
	Ext4 Mailing List <>
Subject: [PATCHv4 0/5] ext4: stop using write_super and s_dirt

This patch-set makes ext4 file-system stop using the VFS '->write_supers()'
call-back and the '->s_dirt' superblock field because I plan to remove them
once all users are gone.

Most of the ext4 changes were done or suggested by Jan Kara (thanks!). This
patch does not do anything complex - we basically notice that ext4 does not
really needd the 'write_super()' functionality and we can remove it. We
mark the superblock buffer as dirty directly, rather than posponing this till
the next 'sync_supers()' kernel thread wake-up.

Tested with xfstests (both journalled and non-journalled ext4 modes).


The goal is to get rid of the 'sync_supers()' kernel thread. This kernel thread
wakes up every 5 seconds (by default) and calls '->write_super()' for all
mounted file-systems. And the bad thing is that this is done even if all the
superblocks are clean. Moreover, many file-systems do not even need this end
they do not register the '->write_super()' method at all (e.g., btrfs).

So 'sync_supers()' most often just generates useless wake-ups and wastes power.
I am trying to make all file-systems independent of '->write_super()' and plan
to remove 'sync_supers()' and '->write_super()' completely once there are no
more users.

Overall status:

1.  ext4: patches submitted,
2.  exofs: patch submitted,
3.  sysv: patches submitted,
4.  udf: patch submitted, sits in Jan Kara's tree:
    git:// for_testing
5.  affs: patches submitted, sit in Al Viro's tree:
    git:// for-next
6.  hfs: patches submitted, sit Andrew Morton's tree
7.  hfsplus: patches submitted, sit in Andrew Morton's tree:
8.  ext2:     done, see commit f72cf5e223a28d3b3ea7dc9e40464fd534e359e8
9.  vfat:     done, see commit 78491189ddb6d84d4a4abae992ed891a236d0263
10. jffs2:    done, see commit 208b14e507c00ff7f108e1a388dd3d8cc805a443
11. reiserfs: done, see commit 033369d1af1264abc23bea2e174aa47cdd212f6f

TODO: ufs

 fs/ext4/ext4.h      |   10 +---------
 fs/ext4/ext4_jbd2.c |    9 ++-------
 fs/ext4/ext4_jbd2.h |    7 ++-----
 fs/ext4/file.c      |   14 +++++++++++++-
 fs/ext4/ialloc.c    |    2 --
 fs/ext4/inode.c     |    2 +-
 fs/ext4/mballoc.c   |    2 --
 fs/ext4/namei.c     |    4 ++--
 fs/ext4/resize.c    |    2 +-
 fs/ext4/super.c     |   15 ++-------------
 10 files changed, 24 insertions(+), 43 deletions(-)

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