Re: [PATCH] ext2: only flush DIRSYNC directories on every change

[Jan Kara]

On Tue 27-10-26 18:43:14, Josef Bacik wrote:
> Every change of an ext2 directory is written to disk before the system call
> returns, whether the directory is DIRSYNC or not: its pages with
> filemap_write_and_wait() and its inode with sync_inode_metadata().
> 
> Writes which reach the device for 2000 files, and 200 directories, in a
> directory without DIRSYNC, with the flusher turned off:
> 
>             create   rename   unlink   mkdir
>     before    4000     8000     4000     800
>     after        0        0        0       0
> 
> In a directory with chattr +D the numbers are those of "before", before and
> after.
> 
> commit bc943f4872a7 ("ext2: Don't flush page immediately for DIRSYNC
> directories") moved the flush from ext2_commit_chunk() to the new
> ext2_handle_dirsync().  The IS_DIRSYNC() check which was around it didn't
> move along.
> 
> Fix by putting the check into ext2_handle_dirsync().
> 
> Fixes: bc943f4872a7 ("ext2: Don't flush page immediately for DIRSYNC directories")
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>

Thanks! Added to my tree.

								Honza

> ---
> I ran into this while testing an overlayfs series with ext2 as the upper
> file system. Directory entries were always on disk after a crash, also
> the ones nobody had synced.
> ---
>  fs/ext2/dir.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
> index e17bbc7598c1..5de32c221a83 100644
> --- a/fs/ext2/dir.c
> +++ b/fs/ext2/dir.c
> @@ -442,6 +442,9 @@ static int ext2_handle_dirsync(struct inode *dir)
>  {
>  	int err;
>  
> +	if (!IS_DIRSYNC(dir))
> +		return 0;
> +
>  	err = filemap_write_and_wait(dir->i_mapping);
>  	if (!err)
>  		err = sync_inode_metadata(dir, 1);
> 
> ---
> base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222
> change-id: 20261027-b4-ext2-dirsync-86ca140154bc
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR