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Date:   Mon, 27 Jul 2020 08:37:48 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Xiao Yang <yangx.jy@cn.fujitsu.com>
Cc:     darrick.wong@oracle.com, ira.weiny@intel.com, tytso@mit.edu,
        linux-ext4@vger.kernel.org
Subject: Re: [PATCH] chattr/lsattr: Support dax attribute
Message-ID: <20200727153748.GA1138@sol.localdomain>
References: <20200727092901.2728-1-yangx.jy@cn.fujitsu.com>
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On Mon, Jul 27, 2020 at 05:29:01PM +0800, Xiao Yang wrote:
> Use the letter 'x' to set/get dax attribute on a directory/file.
> 
> Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
> ---
>  lib/e2p/pf.c         |  1 +
>  lib/ext2fs/ext2_fs.h |  1 +
>  misc/chattr.1.in     | 10 ++++++++--
>  misc/chattr.c        |  3 ++-
>  4 files changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/e2p/pf.c b/lib/e2p/pf.c
> index 0c6998c4..e59cccff 100644
> --- a/lib/e2p/pf.c
> +++ b/lib/e2p/pf.c
> @@ -44,6 +44,7 @@ static struct flags_name flags_array[] = {
>  	{ EXT2_TOPDIR_FL, "T", "Top_of_Directory_Hierarchies" },
>  	{ EXT4_EXTENTS_FL, "e", "Extents" },
>  	{ FS_NOCOW_FL, "C", "No_COW" },
> +	{ FS_DAX_FL, "x", "Dax" },
>  	{ EXT4_CASEFOLD_FL, "F", "Casefold" },
>  	{ EXT4_INLINE_DATA_FL, "N", "Inline_Data" },
>  	{ EXT4_PROJINHERIT_FL, "P", "Project_Hierarchy" },
> diff --git a/lib/ext2fs/ext2_fs.h b/lib/ext2fs/ext2_fs.h
> index 6c20ea77..b5e2e42a 100644
> --- a/lib/ext2fs/ext2_fs.h
> +++ b/lib/ext2fs/ext2_fs.h
> @@ -334,6 +334,7 @@ struct ext2_dx_tail {
>  #define EXT4_EA_INODE_FL	        0x00200000 /* Inode used for large EA */
>  /* EXT4_EOFBLOCKS_FL 0x00400000 was here */
>  #define FS_NOCOW_FL			0x00800000 /* Do not cow file */
> +#define FS_DAX_FL			0x02000000 /* Inode is DAX */
>  #define EXT4_SNAPFILE_FL		0x01000000  /* Inode is a snapshot */
>  #define EXT4_SNAPFILE_DELETED_FL	0x04000000  /* Snapshot is being deleted */
>  #define EXT4_SNAPFILE_SHRUNK_FL		0x08000000  /* Snapshot shrink has completed */

How about putting the values in order?

> diff --git a/misc/chattr.1.in b/misc/chattr.1.in
> index ff2fcf00..b27c8e1f 100644
> --- a/misc/chattr.1.in
> +++ b/misc/chattr.1.in
> @@ -23,7 +23,7 @@ chattr \- change file attributes on a Linux file system
>  .B chattr
>  changes the file attributes on a Linux file system.
>  .PP
> -The format of a symbolic mode is +-=[aAcCdDeFijPsStTu].
> +The format of a symbolic mode is +-=[aAcCdDeFijPsStTux].
>  .PP
>  The operator '+' causes the selected attributes to be added to the
>  existing attributes of the files; '-' causes them to be removed; and '='
> @@ -45,7 +45,8 @@ secure deletion (s),
>  synchronous updates (S),
>  no tail-merging (t),
>  top of directory hierarchy (T),
> -and undeletable (u).
> +undeletable (u),
> +and direct access for files (x).

There's another part that needs to be updated to add "x":

"The letters 'aAcCdDeFijPsStTu' select the new attributes for the files:"