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Date: Mon, 27 Jul 2020 17:29:01 +0800
From: Xiao Yang <yangx.jy@...fujitsu.com>
To: <darrick.wong@...cle.com>, <ira.weiny@...el.com>, <tytso@....edu>
CC: <linux-ext4@...r.kernel.org>, Xiao Yang <yangx.jy@...fujitsu.com>
Subject: [PATCH] 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>
---
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 */
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).
.PP
The following attributes are read-only, and may be listed by
.BR lsattr (1)
@@ -210,6 +211,11 @@ 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
+A file with the 'x' attribute set is accessed directly on the memory-like
+disk(e.g. /dev/pmem) by the kernel. Kernel will skip page cache and do
+reads/writes on the file directly.
+.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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