[PATCH 0/3] do not use s_dirt in JFFS2

[Artem Bityutskiy]

This patch-set makes JFFS2 file-system stop using the VFS '->write_supers()'
call-back because I plan to remove it once all users are gone.

The final 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, some 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.

The '->write_supers()' method is mostly used by baroque file-systems like hfs,
udf, etc. Modern file-systems like btrfs and xfs do not use it. This justifies
removing this stuff from VFS completely and make every FS self-manage own
superblock.

Note: in the past I was trying to upstream patches which optimized 'sync_super()',
but Al Viro wanted me to kill it completely instead, which I am trying to do
now, see http://lkml.org/lkml/2010/7/22/96

======
Overall status:

1. ext4: patches submitted, waiting for reply from Ted Ts'o:
   https://lkml.org/lkml/2012/4/2/111
   Ted keeps silence so far WRT the fate of this patch-set.
2. ext2: patches are in the ext2 tree maintained by Jan Kara:
   git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git for_next
3. Version 3 of FAT FS changes were sent to Andrew and Hirofumi:
   https://lkml.org/lkml/2012/5/4/183
4. JFFS2 patches are sent being sent now.

TODO: affs, exofs, hfs, hfsplus, reiserfs, sysv, udf, ufs
======

 fs/fat/fat.h             |    1 +
 fs/fat/fatent.c          |   22 +++++++++++++-----
 fs/fat/inode.c           |   54 ++++++++++++++++++++-------------------------
 include/linux/msdos_fs.h |    3 +-
 4 files changed, 43 insertions(+), 37 deletions(-)

Thanks,
Artem.