On 2020/8/8 0:03, Ira Weiny wrote:
On Tue, Jul 28, 2020 at 01:33:21PM +0800, Xiao Yang wrote:
Use the letter 'x' to set/get dax attribute on a directory/file.
Signed-off-by: Xiao Yang<yangx.jy@xxxxxxxxxxxxxx>
---
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 */
Per-file support is not supported on ext2...
So I'm suspicious of this change. It is probably not an issue but I just
wanted to check if you are trying to test on ext2?
Hi Ira,
Thanks for your reply. :-)
chattr failed to set the 'x' flag on ext2 sliently because ext2_ioctl()
in kernel drops
unsupported 'FS_DAX_FL' sliently:
----------------------------------------------
# touch file
# chattr +x file;echo $?
0
# lsattr file
--------------------- file
----------------------------------------------
ext2_ioctl() drops all unsupported flags sliently(see the following
code) so I am
not sure if we should return -EOPNOTSUPP for the unsupported FS_DAX_FL:
----------------------------------------------
long ext2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
...
case EXT2_IOC_SETFLAGS: {
...
flags = flags & EXT2_FL_USER_MODIFIABLE;
flags |= oldflags & ~EXT2_FL_USER_MODIFIABLE;
ei->i_flags = flags;
ext2_set_inode_flags(inode);
...
----------------------------------------------
Best Regards,
Xiao Yang
Ira
#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
.
