[PATCH 1/4] vfs: report change attribute in statx for IS_I_VERSION inodes

[David Howells]

Christian Brauner <brauner at kernel.org> wrote:

> > +#define STATX_CHANGE_ATTR	0x00002000U	/* Want/got stx_change_attr */
> 
> I'm a bit worried that STATX_CHANGE_ATTR isn't a good name for the flag
> and field. Or I fail to understand what exact information this will
> expose and how userspace will consume it.
> To me the naming gives the impression that some set of generic
> attributes have changed but given that statx is about querying file
> attributes this becomes confusing.
> 
> Wouldn't it make more sense this time to expose it as what it is and
> call this STATX_INO_VERSION and __u64 stx_ino_version?

I'm not sure that STATX_INO_VERSION is better that might get confused with the
version number that's used to uniquify inode slots (ie. deal with inode number
reuse).

The problem is that we need fsinfo() or similar to qualify what this means.
On some filesystems, it's only changed when the data content changes, but on
others it may get changed when, say, xattrs get changed; further, on some
filesystems it might be monotonically incremented, but on others it's just
supposed to be different between two consecutive changes (nfs, IIRC).

David