Re: [RFC 6/8] ext4: Add an inode flag for atomic writes

[Dave Chinner]

On Sat, Mar 02, 2024 at 01:12:03PM +0530, Ritesh Harjani (IBM) wrote:
> This patch adds an inode atomic writes flag to ext4
> (EXT4_ATOMICWRITES_FL which uses FS_ATOMICWRITES_FL flag).
> Also add support for setting of this flag via ioctl.
> 
> Co-developed-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
> Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx>
> ---
>  fs/ext4/ext4.h  |  6 ++++++
>  fs/ext4/ioctl.c | 11 +++++++++++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 1d2bce26e616..aa7fff2d6f96 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -495,8 +495,12 @@ struct flex_groups {
>  #define EXT4_EA_INODE_FL	        0x00200000 /* Inode used for large EA */
>  /* 0x00400000 was formerly EXT4_EOFBLOCKS_FL */
>  
> +#define EXT4_ATOMICWRITES_FL		FS_ATOMICWRITES_FL /* Inode supports atomic writes */
>  #define EXT4_DAX_FL			0x02000000 /* Inode is DAX */

Tying the on disk format to the kernel user API is a poor choice.
While the flag bits might have the same value, anything parsing the
on-disk format should not be required to include kernel syscall API
header files just to get all the on-disk format definitions it
needs.

-Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx