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Date:   Tue, 28 Jul 2020 13:33:21 +0800
From:   Xiao Yang <yangx.jy@...fujitsu.com>
To:     <darrick.wong@...cle.com>, <ira.weiny@...el.com>, <tytso@....edu>,
        <ebiggers@...nel.org>
CC:     <linux-ext4@...r.kernel.org>, Xiao Yang <yangx.jy@...fujitsu.com>
Subject: [PATCH v2] chattr/lsattr: Support dax attribute

Use the letter 'x' to set/get dax attribute on a directory/file.

Signed-off-by: Xiao Yang <yangx.jy@...fujitsu.com>
---

V1->V2:
1) Define FS_DAX_FL in order and add missing 'x' letter in manpage.
2) Add more detailed description about 'x' attribute.
3) 'x' is a separate attribute and doesn't always affect S_DAX(i.e.
   pagecache bypass) so remove the related info.

 lib/e2p/pf.c         |  1 +
 lib/ext2fs/ext2_fs.h |  1 +
 misc/chattr.1.in     | 15 ++++++++++++---
 misc/chattr.c        |  3 ++-
 4 files changed, 16 insertions(+), 4 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..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



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