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[PATCH v1 0/8] do not use s_dirt in ext2

March 21st, 2012 - 11:20 am ET by Artem Bityutskiy | Report spam
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This patch-set makes ext2 independent of the VFS superblock management
services. Namely, ext2 does not require to register the 'write_super()' VFS
call-back.

The reason of this exercises is to get rid of the 'sync_supers()' kernel thread
which wakes up every 5 seconds (by default) even if all superblocks are clean.
This is wasteful from power management POW (unnecessary wake-ups).

Note, I tried to optimize 'sync_supers()' instead in 2010, but Al wanted me
to get rid of it instead. See https://lkml.org/lkml/2010/6/6/87
And I think this is right because many file-systems do not need this, for
example btrfs does not use VFS superblock management services at all, so on a
btrfs-based system we currently end-up useless periodic wake-ups source.

I have sent a similar patch-set for ext4 recently to Ted, see:
http://lkml.org/lkml/2012/3/20/220

Changes for other file-systems are coming later.

The patch-set structure.
1. patch 1 exports 'dirty_writeback_interval' and I also sent it as part of the
ext4 patch-set
2. patch 2 is also and independent VFS clean-up and I also sent it as part of
the ext4 patch-set
3. patch 3 is an independent ext2 clean-up patch
4. patches 4-8 actually make ext2 independent on the 'sync_supers()' thread.

Thanks,
Artem.
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#1 Artem Bityutskiy
March 21st, 2012 - 11:20 am ET | Report spam
From: Artem Bityutskiy

Remove the 'sb_mark_dirty()', 'sb_mark_clean()' and 'sb_is_dirty()' helpers
which are not used. I introduced them 2 years and the intention was to make
all file-systems use them in order to be able to optimize 'sync_supers()'.
However, Al Viro vetoed my patches at the end and asked me to push superblock
management down to file-systems and get rid of the 's_dirt' flag completely,
as well as kill 'sync_supers()' altogether. Thus, remove the helpers.

Signed-off-by: Artem Bityutskiy

include/linux/fs.h | 13 -
1 files changed, 0 insertions(+), 13 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 69cd5bb..68387e9 100644
a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1870,19 +1870,6 @@ extern struct dentry *mount_pseudo(struct file_system_type *, char *,
const struct dentry_operations *dops,
unsigned long);

-static inline void sb_mark_dirty(struct super_block *sb)
-{
- sb->s_dirt = 1;
-}
-static inline void sb_mark_clean(struct super_block *sb)
-{
- sb->s_dirt = 0;
-}
-static inline int sb_is_dirty(struct super_block *sb)
-{
- return sb->s_dirt;
-}
-
/* Alas, no aliases. Too much hassle with bringing module.h everywhere */
#define fops_get(fops) \
(((fops) && try_module_get((fops)->owner) ? (fops) : NULL))
1.7.7.6

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