Re: [RFC PATCH v2 1/2] vfs: add provenance time (ptime)

[Amir Goldstein]

On Wed, Oct 28, 2026 at 02:56:39PM +0000, Pedro Falcato wrote:
> On Wed, Oct 28, 2026 at 02:47:27PM +0100, koraynilay wrote:
> > Add provenance time (ptime), indicating the time when a file or
> > directory was created. This is user-settable via file_setattr() and
> > retrievable via statx(2) (using STATX_PTIME) or file_getattr().
> > 
> > The semantics of when to preserve this new timestamp are the same as
> > mtime, the idea being that there is a correspondence like this:
> > 
> > ctime <-> btime
> > mtime <-> ptime
> > 
> > so every operation (copying, moving, ...) that currently preserves mtime
> > should also preserve ptime.
> > 
> > Furthermore, in order to avoid the legacy FS_IOC_FSSETXATTR accepting
> > FS_XFLAG_PTIME, add an FS_FILE_ATTR_XFLAGS_MASK mask to support new
> > xflags, and use it in fileattr_to_file_attr()/file_attr_to_fileattr() to
> > allow ptime to be used with the file_setattr()/file_getattr() syscalls.
> 
> Random comment, but: could this be doable with xattrs instead? I'm not sure
> where I would put the xattrs code (if in userspace exclusively, or if hooking
> the VFS up with this, or if doing it on the filesystem side), but it would
> surely be less disruptive than modifying a bunch of filesystems one-by-one.
> 
> This patch is quite simple, but changing btrfs, then ext4, xfs, etc is a
> mess, and inevitably you can't get these timestamps until you upgrade your
> filesystems.
> 

I disagree.

I think that creation time should be a first class property in
filesystems that support it.

Thanks,
Amir.