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[176.246.9.149]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4b2aa481a45sm122452345e9.7.2026.11.04.03.37.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Nov 2026 03:37:30 -0800 (PST) X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 Content-Type: multipart/signed; boundary=48cc1ad8402764d92e1376cc3050a9a9645276db561dde693e9f605d6644; micalg=pgp-sha512; protocol="application/pgp-signature" Date: Wed, 04 Nov 2026 12:37:22 +0100 Message-Id: Cc: "David Sterba" , "Alexander Viro" , "Christian Brauner" , "Chris Mason" , "Darrick J . Wong" , "Sean Smith" , "Andrey Albershteyn" , , , Subject: Re: [RFC PATCH 0/2] add provenance time (ptime) From: "koraynilay" To: "Jan Kara" , "koraynilay" X-Mailer: aerc 0.22.0-0-gc2f86b7abde3 References: <20261027220532.736352-1-koray.fra@gmail.com> In-Reply-To: --48cc1ad8402764d92e1376cc3050a9a9645276db561dde693e9f605d6644 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 On Wed Nov 4, 2026 at 12:33 PM CET, Jan Kara wrote: > On Tue 03-11-26 15:26:20, koraynilay wrote: >> On Tue Nov 3, 2026 at 2:25 PM CET, Jan Kara wrote: >> > On Tue 27-10-26 23:05:30, koraynilay wrote: >> >> This is an initial implementation of a new timestamp to indicate the >> >> time when a file/directory was initially created. >> >>=20 >> >> This patch series takes inspiration from the one by Sean Smith >> >> [1], but using >> >> file_setattr()/file_getattr() as suggested by Darrick J. Wong >> >> in [2]. >> >>=20 >> >> The semantics of this new timestamp should be at least these: >> >> - it should be the same as btime on a newly created file >> >> - it's user-settable, so it can be preserved for backups, filesystem >> >> conversions, archives and any similar operation >> >> - it should be preserved every time mtime gets preserved >> >>=20 >> >> and the correspondence with the other timestamps is as follows: >> >>=20 >> >> ctime <-> btime >> >> mtime <-> ptime >> > >> > One thing I miss in this series is an explanation what this new timest= amp is >> > good for. Because frankly, I don't miss such timestamp as a Linux user= :). >> > >> > Honza >>=20 >> Hello, my concrete use-cases are backups and filesystem conversions. >>=20 >> For backups, my setup is btrfs and using btrbk (so btrfs send to my nas >> with ssh) and the only missing thing from the backup is the timestamp of >> file creation (which I'm currently working around using xattrs). >>=20 >> The situation that prompted me to finally start working on this RFC >> PATCH was when I wanted to merge 2 btrfs FSs and the only way of doing >> that (AFAIK at least) is using cp/rsync, which can't set the creation >> time since btime is immutable. The workaround I used was the same as >> with backups, so with xattrs, but noticed that some files (symlinks) >> wouldn't accept xattrs, so I looked into it and found out xattrs are >> only for regular files/dirs. >>=20 >> (also see https://lore.kernel.org/DMGS4KQLY24Q.14MUTR6U93GIC@gmail.com/) > > Ah, OK, I think I finally understand why do you want this. Thanks for > explanation! > > Honza Nice, thank you! Best, koraynilay --48cc1ad8402764d92e1376cc3050a9a9645276db561dde693e9f605d6644 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQRJ2XvJtXGwULYEerQ0bnTtJTDoOAUCausY8gAKCRA0bnTtJTDo ODftAQC9g00TbhJ4fqkc0NSdA1KvBdO2hUflWG1D9U7QPJVKNwD/e1sMPB8EEpEs oOjAe8fi91WQcNkFmUDPnwGV8y9PRQ0= =eltA -----END PGP SIGNATURE----- --48cc1ad8402764d92e1376cc3050a9a9645276db561dde693e9f605d6644--