On Tue 27-03-12 16:29:58, Artem Bityutskiy wrote:
> On Thu, 2012-03-22 at 11:33 +0100, Jan Kara wrote:
> > Then we have ext4_mark_super_dirty() call from 4 places - I forgot about
> > these originally... I kind of miss their purpose. Originally they were used
> > so that we write total number of free blocks and inodes in the superblock
> > but when we do not maintain them in the journal mode I don't see a reason
> > to periodically sync them in no-journal mode. Ted, what is the purpose of
> > these calls?
>
> I do not understand what's the fundamental difference between journal
> and non-journal mode. Why when we do have the journal we do not mark the
> super-block as dirty in many places (e.g., in 'ext4_file_open()' - if we
> do have the journal, when do we make sure we save the mount point path
> change?).
We write it at least during ext4_put_super().
> May be it has something to do with behaving like the ext2 driver when
> mounting ext2-formatted media with the the ext4 driver?
I'm not really sure about this...
> Jan, since Ted did not answer, may be you can figure out the reasons
> from this commit message, which actually introduced the
> 'ext4_mark_super_dirty()' function?
Anyway, attached are two patches which you can include in your series
and which should make your cleanups simpler.
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
>From b66c62b32485ad708d91e03ebc66f618d4c9add4 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Tue, 27 Mar 2012 21:43:09 +0200
Subject: [PATCH 1/2] ext4: Remove useless marking of superblock dirty
Commit a0375156 properly notes that superblock doesn't need to be marked
as dirty when only number of free inodes / blocks / number of directories
changes since that is recomputed on each mount anyway. However that comment
leaves some unnecessary markings as dirty in place. Remove these.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/ext4/ialloc.c | 2 --
fs/ext4/mballoc.c | 2 --
2 files changed, 0 insertions(+), 4 deletions(-)
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 25d8c97..f0a17c3 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -284,7 +284,6 @@ out:
err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
if (!fatal)
fatal = err;
- ext4_mark_super_dirty(sb);
} else
ext4_error(sb, "bit already cleared for inode %lu", ino);
@@ -846,7 +845,6 @@ got:
percpu_counter_dec(&sbi->s_freeinodes_counter);
if (S_ISDIR(mode))
percpu_counter_inc(&sbi->s_dirs_counter);
- ext4_mark_super_dirty(sb);
if (sbi->s_log_groups_per_flex) {
flex_group = ext4_flex_group(sbi, group);
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index cb990b2..7daea1f 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2875,7 +2875,6 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
err = ext4_handle_dirty_metadata(handle, NULL, gdp_bh);
out_err:
- ext4_mark_super_dirty(sb);
brelse(bitmap_bh);
return err;
}
@@ -4749,7 +4748,6 @@ do_more:
put_bh(bitmap_bh);
goto do_more;
}
- ext4_mark_super_dirty(sb);
error_return:
brelse(bitmap_bh);
ext4_std_error(sb, err);
--
1.7.1
>From 7d49e3df08597241677feaadbb8463758d6e282b Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Tue, 27 Mar 2012 22:05:18 +0200
Subject: [PATCH 2/2] ext4: Convert last user of ext4_mark_super_dirty() to ext4_handle_dirty_super()
The last user of ext4_mark_super_dirty() in ext4_file_open() is so rare it
can well be modifying the superblock properly by journalling the change.
Change it and get rid of ext4_mark_super_dirty() as it's not needed anymore.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/ext4/ext4.h | 6 ------
fs/ext4/file.c | 15 ++++++++++++++-
2 files changed, 14 insertions(+), 7 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 513004f..4764d1e 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2204,12 +2204,6 @@ static inline void ext4_unlock_group(struct super_block *sb,
spin_unlock(ext4_group_lock_ptr(sb, group));
}
-static inline void ext4_mark_super_dirty(struct super_block *sb)
-{
- if (EXT4_SB(sb)->s_journal == NULL)
- sb->s_dirt =1;
-}
-
/*
* Block validity checking
*/
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index cb70f18..d7a858c 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -181,9 +181,22 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
path.dentry = mnt->mnt_root;
cp = d_path(&path, buf, sizeof(buf));
if (!IS_ERR(cp)) {
+ handle_t *handle;
+ int err;
+
+ handle = ext4_journal_start_sb(sb, 1);
+ if (IS_ERR(handle))
+ return PTR_ERR(handle);
+ err = ext4_journal_get_write_access(handle,
+ EXT4_SB(sb)->s_sbh);
+ if (err) {
+ ext4_journal_stop(sb);
+ return err;
+ }
strlcpy(sbi->s_es->s_last_mounted, cp,
sizeof(sbi->s_es->s_last_mounted));
- ext4_mark_super_dirty(sb);
+ ext4_handle_dirty_super(handle, sb);
+ ext4_journal_stop(handle);
}
}
/*
--
1.7.1
