linux-ext4 - Re: [PATCH v2] chattr/lsattr: Support dax attribute

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Date:   Wed, 12 Aug 2020 17:29:54 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     Xiao Yang <yangx.jy@...fujitsu.com>
Cc:     "Darrick J. Wong" <darrick.wong@...cle.com>,
        Ira Weiny <ira.weiny@...el.com>, Theodore Ts'o <tytso@....edu>,
        Eric Biggers <ebiggers@...nel.org>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH v2] chattr/lsattr: Support dax attribute

On Jul 27, 2020, at 11:33 PM, Xiao Yang <yangx.jy@...fujitsu.com> wrote:
> 
> Use the letter 'x' to set/get dax attribute on a directory/file.
> 
> Signed-off-by: Xiao Yang <yangx.jy@...fujitsu.com>

One minor nit below, but otherwise looks OK.

Reviewed-by: Andreas Dilger <adilger@...ger.ca>

> 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" },

Should this be "DAX" ?  That is how it is commonly used in the kernel.

> 	{ 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..88f510a3 100644
> --- a/lib/ext2fs/ext2_fs.h
> +++ b/lib/ext2fs/ext2_fs.h
> @@ -335,6 +335,7 @@ struct ext2_dx_tail {
> /* EXT4_EOFBLOCKS_FL 0x00400000 was here */
> #define FS_NOCOW_FL			0x00800000 /* Do not cow file */
> #define EXT4_SNAPFILE_FL		0x01000000  /* Inode is a snapshot */
> +#define FS_DAX_FL			0x02000000 /* Inode is DAX */
> #define EXT4_SNAPFILE_DELETED_FL	0x04000000  /* Snapshot is being deleted */
> #define EXT4_SNAPFILE_SHRUNK_FL		0x08000000  /* Snapshot shrink has completed */
> #define EXT4_INLINE_DATA_FL		0x10000000 /* Inode has inline data */
> diff --git a/misc/chattr.1.in b/misc/chattr.1.in
> index ff2fcf00..5a4928a5 100644
> --- a/misc/chattr.1.in
> +++ b/misc/chattr.1.in
> @@ -23,13 +23,13 @@ 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 '='
> causes them to be the only attributes that the files have.
> .PP
> -The letters 'aAcCdDeFijPsStTu' select the new attributes for the files:
> +The letters 'aAcCdDeFijPsStTux' select the new attributes for the files:
> append only (a),
> no atime updates (A),
> compressed (c),
> @@ -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).
> .PP
> The following attributes are read-only, and may be listed by
> .BR lsattr (1)
> @@ -210,6 +211,14 @@ saved.  This allows the user to ask for its undeletion.  Note: please
> make sure to read the bugs and limitations section at the end of this
> document.
> .TP
> +.B x
> +The 'x' attribute can be set on a directory or file.  If the attribute
> +is set on an existing directory, it will be inherited by all files and
> +subdirectories that are subsequently created in the directory.  If an
> +existing directory has contained some files and subdirectories, modifying
> +the attribute on the parent directory doesn't change the attributes on
> +these files and subdirectories.
> +.TP
> .B V
> A file with the 'V' attribute set has fs-verity enabled.  It cannot be
> written to, and the filesystem will automatically verify all data read
> diff --git a/misc/chattr.c b/misc/chattr.c
> index a5d60170..c0337f86 100644
> --- a/misc/chattr.c
> +++ b/misc/chattr.c
> @@ -86,7 +86,7 @@ static unsigned long sf;
> static void usage(void)
> {
> 	fprintf(stderr,
> -		_("Usage: %s [-pRVf] [-+=aAcCdDeijPsStTuF] [-v version] files...\n"),
> +		_("Usage: %s [-pRVf] [-+=aAcCdDeijPsStTuFx] [-v version] files...\n"),
> 		program_name);
> 	exit(1);
> }
> @@ -112,6 +112,7 @@ static const struct flags_char flags_array[] = {
> 	{ EXT2_NOTAIL_FL, 't' },
> 	{ EXT2_TOPDIR_FL, 'T' },
> 	{ FS_NOCOW_FL, 'C' },
> +	{ FS_DAX_FL, 'x' },
> 	{ EXT4_CASEFOLD_FL, 'F' },
> 	{ 0, 0 }
> };
> --
> 2.21.0
> 
> 
> 


Cheers, Andreas






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