2011-05-28 15:52:43

by Sam Gandhi

Subject: Can someone explain s_xattr field in the superblock?

Hello,

I have seen some file systems like jffs2/ext4 etc setup the s_xattr
field in the superblock structure.
But there are files systems that do not initialize s_xattr field in
the superblock.

Can someone kindly explain what functionality does s_xattr on super
block provides? What kinds of things file system wouldn't be able to
do if the superblock doesn't have this initialized?

Thanks.
-Sam

2011-06-01 02:22:27

by Theodore Ts'o

Subject: Re: Can someone explain s_xattr field in the superblock?

On Sat, May 28, 2011 at 08:52:41AM -0700, Sam Gandhi wrote:
>
> I have seen some file systems like jffs2/ext4 etc setup the s_xattr
> field in the superblock structure.
> But there are files systems that do not initialize s_xattr field in
> the superblock.
>
> Can someone kindly explain what functionality does s_xattr on super
> block provides? What kinds of things file system wouldn't be able to
> do if the superblock doesn't have this initialized?

It provides support for extended attributes, which is often
abbreviated as (not surpisingly) xattr. Some file systems don't
support extended attributes, so they don't need to setup s_xattr.

For more information, read the attr(5) man page: "man 5 attr".

- Ted