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

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Date:   Fri, 28 Aug 2020 09:33:12 +0800
From:   Xiao Yang <yangx.jy@...fujitsu.com>
To:     Andreas Dilger <adilger@...ger.ca>
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

Hi,

Is there any comment on the patch? :-)

Thanks,
Xiao Yang
On 2020/8/13 9:42, Xiao Yang wrote:
> On 2020/8/13 7:29, Andreas Dilger wrote:
>> 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.
> Hi Andreas,
>
> Thanks a lot for your review.
>
> Either 'Dax' or 'DAX' is fine to me because it is just the output of 
> lsattr -v.
> For example, xfs_io shows 'dax' instead of 'DAX':
> # xfs_io -c "lsattr -v" file
> [dax] file
>
> BTW:
> I just used 'Dax' to follow the current format of output(i.e. 
> capitalize the first letter).
>
> Do you want me to send v3 patch with the 'DAX'? :-)
>
> Best Regards,
> Xiao Yang
>>>     { 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
>>
>>
>>
>>
>>
>