On Thu, Feb 14, 2019 at 02:00:07AM -0800, Omar Sandoval wrote:

From: Omar Sandoval <redacted>
Since statx was added in 4.11, userspace has had an interface for
reading btime (file creation time), but no way to set it. This RFC patch
series adds support for changing btime with utimensat(). Patch 1 adds
the VFS infrastructure, patch 2 adds the support to utimensat() with a
new flag, and the rest of the patches add filesystem support; I excluded
CIFS for now because I don't have a CIFS setup to test it on.

Updating btime is useful for at least a couple of use cases:

- Backup/restore programs (my motivation for this feature is btrfs send)
- File servers which interoperate with operating systems that allow
  updating file creation time, including Mac OS [1] and Windows [2]

I don't have anything new to add to what has been said in the thread.
The creation time is property of the filesystem and if user wants to
track additional metadata, then as external attributes.