On May 19, 2020, at 11:57 PM, 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 with the
> exception of if VERITY or ENCRYPT is set.
> 
> Disallow setting VERITY or ENCRYPT if DAX is set.
> 
> 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>
> 
> ---
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 6235440e4c39..467c30a789b6 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 */
> /* 0x00400000 was formerly EXT4_EOFBLOCKS_FL */
> +
> +#define EXT4_DAX_FL			0x01000000 /* Inode is DAX */
> +
> #define EXT4_INLINE_DATA_FL		0x10000000 /* Inode has inline data. */
> #define EXT4_PROJINHERIT_FL		0x20000000 /* Create with parents projid */
> #define EXT4_CASEFOLD_FL		0x40000000 /* Casefolded file */
> #define EXT4_RESERVED_FL		0x80000000 /* reserved for ext4 lib */

Hi Ira,
This flag value conflicts with the reserved flag in e2fsprogs for snapshots:

#define EXT4_SNAPFILE_FL                0x01000000  /* Inode is a snapshot */

Please change EXT4_DAX_FL and FS_DAX_FL to use 0x02000000, which is not used
for anything in either case.

Cheers, Andreas


> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 379a612f8f1d..7c5f6eb51e2d 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -262,6 +262,7 @@ struct fsxattr {
> #define FS_EA_INODE_FL			0x00200000 /* Inode used for large EA */
> #define FS_EOFBLOCKS_FL			0x00400000 /* Reserved for ext4 */
> #define FS_NOCOW_FL			0x00800000 /* Do not cow file */
> +#define FS_DAX_FL			0x01000000 /* Inode is DAX */
> #define FS_INLINE_DATA_FL		0x10000000 /* Reserved for ext4 */
> #define FS_PROJINHERIT_FL		0x20000000 /* Create with parents projid */
> #define FS_CASEFOLD_FL			0x40000000 /* Folder is case insensitive */
> --
> 2.25.1
> 


Cheers, Andreas