[v2,3/4] ext4: remove unnecessary superblock dirtying

From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

This patch changes the '__ext4_handle_dirty_super()' function which is used
by ext4 to update the super-block via the journal in the following cases:

1. When creating the first large file on a file
   system without EXT4_FEATURE_RO_COMPAT_LARGE_FILE feature.
2. When re-sizing the file-system
3. When creating an xattr on a file-system without the
   EXT4_FEATURE_COMPAT_EXT_ATTR feature.

This function, however, falls back to just marking the superblock as dirty
if the file-system has no journal. But it is user really rarely and it does not
give any benefit to use the delayed superblock write (via the VFS's
'sync_supers()' kernel thread) in these cases. We can just write out the
superblock asynchronously instead.

This patch also removes 's_dirt' condition on the unmount path because we never
set it anymore, so we should not test it.

Tested using xfstests for both journalled and non-journalled ext4.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
---
 fs/ext4/ext4.h      |    1 +
 fs/ext4/ext4_jbd2.c |    2 +-
 fs/ext4/super.c     |    5 ++---
 3 files changed, 4 insertions(+), 4 deletions(-)

On Mon 02-04-12 14:45:39, Artem Bityutskiy wrote:
> From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
> 
> This patch changes the '__ext4_handle_dirty_super()' function which is used
> by ext4 to update the super-block via the journal in the following cases:
> 
> 1. When creating the first large file on a file
>    system without EXT4_FEATURE_RO_COMPAT_LARGE_FILE feature.
> 2. When re-sizing the file-system
> 3. When creating an xattr on a file-system without the
>    EXT4_FEATURE_COMPAT_EXT_ATTR feature.
> 
> This function, however, falls back to just marking the superblock as dirty
> if the file-system has no journal. But it is user really rarely and it does not
> give any benefit to use the delayed superblock write (via the VFS's
> 'sync_supers()' kernel thread) in these cases. We can just write out the
> superblock asynchronously instead.
> 
> This patch also removes 's_dirt' condition on the unmount path because we never
> set it anymore, so we should not test it.
> 
> Tested using xfstests for both journalled and non-journalled ext4.
> 
> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
  Looks good.
Reviewed-by: Jan Kara <jack@suse.cz>

									Honza
> ---
>  fs/ext4/ext4.h      |    1 +
>  fs/ext4/ext4_jbd2.c |    2 +-
>  fs/ext4/super.c     |    5 ++---
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index aba3749..ba2cf3f 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1953,6 +1953,7 @@ extern int ext4_group_extend(struct super_block *sb,
>  extern int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count);
>  
>  /* super.c */
> +int ext4_commit_super(struct super_block *sb, int sync);
>  extern void *ext4_kvmalloc(size_t size, gfp_t flags);
>  extern void *ext4_kvzalloc(size_t size, gfp_t flags);
>  extern void ext4_kvfree(void *ptr);
> diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
> index aca1790..a85f46f 100644
> --- a/fs/ext4/ext4_jbd2.c
> +++ b/fs/ext4/ext4_jbd2.c
> @@ -149,6 +149,6 @@ int __ext4_handle_dirty_super(const char *where, unsigned int line,
>  			ext4_journal_abort_handle(where, line, __func__,
>  						  bh, handle, err);
>  	} else
> -		sb->s_dirt = 1;
> +		err = ext4_commit_super(sb, 0);
>  	return err;
>  }
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index ceebaf8..6b45785 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -63,7 +63,6 @@ static struct ext4_features *ext4_feat;
>  static int ext4_load_journal(struct super_block *, struct ext4_super_block *,
>  			     unsigned long journal_devnum);
>  static int ext4_show_options(struct seq_file *seq, struct dentry *root);
> -static int ext4_commit_super(struct super_block *sb, int sync);
>  static void ext4_mark_recovery_complete(struct super_block *sb,
>  					struct ext4_super_block *es);
>  static void ext4_clear_journal_err(struct super_block *sb,
> @@ -853,7 +852,7 @@ static void ext4_put_super(struct super_block *sb)
>  		EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
>  		es->s_state = cpu_to_le16(sbi->s_mount_state);
>  	}
> -	if (sb->s_dirt || !(sb->s_flags & MS_RDONLY))
> +	if (!(sb->s_flags & MS_RDONLY))
>  		ext4_commit_super(sb, 1);
>  
>  	if (sbi->s_proc) {
> @@ -3991,7 +3990,7 @@ static int ext4_load_journal(struct super_block *sb,
>  	return 0;
>  }
>  
> -static int ext4_commit_super(struct super_block *sb, int sync)
> +int ext4_commit_super(struct super_block *sb, int sync)
>  {
>  	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
>  	struct buffer_head *sbh = EXT4_SB(sb)->s_sbh;
> -- 
> 1.7.7.6
>