Re: [RFC PATCH v1 0/6] provenance_time (ptime): a new settable timestamp for cross-filesystem provenance

["Theodore Tso" <tytso@mit.edu>]

On Mon, Apr 06, 2026 at 07:05:55PM -0500, Sean Smith wrote:
> The patches implement rename-over preservation in all 5
> filesystem rename handlers. When rename(source, target)
> replaces an existing file, and the source has ptime=0 (the
> default for any newly-created temp file) while the target
> has ptime != 0, the filesystem copies the target's ptime to
> the source before destroying the target's inode. This runs
> inside the rename transaction, atomic with the rename itself.

Yelch.   This is so *very* non-Unixy / non-POSIX / non-Linux.

I understand why it's convenient for your particular use case, but
rename(2) is fundamentally an operation which works on directory
entries.  We don't copy over extended attributes, or Posix ACL's, or
Unix permission mode bits, because (a) that would violate POSIX and
historical Unix behavior, and (b) because rename(2) is fundamentally a
directory entry operation.  This is despite the fact that it be more
convenient if we didn't have to copy over things like extended
attributes, ACL's, permission mode bits, etc.  So you want to make an
exception for ptime?   Yelch.  Just Yelch.

						- Ted