LinuxLists.cc - [PATCH] chattr/lsattr: Support dax attribute

2020-07-27 09:38:02

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 <[email protected]>
---
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

2020-07-27 15:39:31

by Eric Biggers

[permalink] [raw]

Subject: Re: [PATCH] chattr/lsattr: Support dax attribute

2020-07-27 18:48:14

by Darrick J. Wong

[permalink] [raw]

Subject: Re: [PATCH] chattr/lsattr: Support dax attribute

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 <[email protected]>
> ---
> 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.

There's much more to FS_DAX_FL than that.

See the "Enabling DAX on XFS and ext4" section of
Documentation/filesystems/dax.txt.

Note the part where you can set it on directories too; and also the part
where there's a separate state for whether or not you get the pagecache
bypass.

--D

> +.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
>
>
>

2020-07-28 01:09:53

by Xiao Yang

[permalink] [raw]

Subject: Re: [PATCH] chattr/lsattr: Support dax attribute

Hi Eric,

Thanks for your review.

On 2020/7/27 23:37, Eric Biggers wrote:
> 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<[email protected]>
>> ---
>> 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?

Sure, I will put 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:"
Good catch. :-)

Thanks,
Xiao Yang
>
> .
>

2020-07-28 01:13:23

by Xiao Yang

[permalink] [raw]

Subject: Re: [PATCH] chattr/lsattr: Support dax attribute

Hi Darrick,

Thanks for your review.

On 2020/7/28 0:08, Darrick J. Wong wrote:
> 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<[email protected]>
>> ---
>> 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.
> There's much more to FS_DAX_FL than that.

Agreed. Sorry for the rough description.

> See the "Enabling DAX on XFS and ext4" section of
> Documentation/filesystems/dax.txt.
>
> Note the part where you can set it on directories too; and also the part
> where there's a separate state for whether or not you get the pagecache
> bypass.

I will try to add more detailed description in v2 patch.

Thanks,
Xiao Yang
> --D
>
>> +.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
>>
>>
>>
>
> .
>