Re: [PATCH RFC 4/8] fs/ext4: Introduce DAX inode flag

Jan Kara
2020-04-15T12:12:55Z

On Mon 13-04-20 21:00:26, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
>
> Add a flag to preserve FS_XFLAG_DAX in the ext4 inode.
>
> Set the flag to be user visible and changeable. Set the flag to be
> inherited. Allow applications to change the flag at any time.
>
> Finally, on regular files, flag the inode to not be cached to facilitate
> changing S_DAX on the next creation of the inode.
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> ---
> fs/ext4/ext4.h | 13 +++++++++----
> fs/ext4/ioctl.c | 21 ++++++++++++++++++++-
> 2 files changed, 29 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 61b37a052052..434021fcec88 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -415,13 +415,16 @@ struct flex_groups {
> #define EXT4_VERITY_FL 0x00100000 /* Verity protected inode */
> #define EXT4_EA_INODE_FL 0x00200000 /* Inode used for large EA */
> #define EXT4_EOFBLOCKS_FL 0x00400000 /* Blocks allocated beyond EOF */
> +
> +#define EXT4_DAX_FL 0x00800000 /* Inode is DAX */
> +

You seem to be using somewhat older kernel... EXT4_EOFBLOCKS_FL doesn't
exist anymore (but still it's good to leave it reserved for some time so
the value you've chosen is OK).

> @@ -813,6 +818,17 @@ static int ext4_ioctl_get_es_cache(struct file *filp, unsigned long arg)
> return error;
> }
>
> +static void ext4_dax_dontcache(struct inode *inode, unsigned int flags)
> +{
> + struct ext4_inode_info *ei = EXT4_I(inode);
> +
> + if (S_ISDIR(inode->i_mode))
> + return;
> +
> + if ((ei->i_flags ^ flags) == EXT4_DAX_FL)
> + inode->i_state |= I_DONTCACHE;
> +}
> +

You probably want to use the function you've introduced in the XFS series
here...

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR