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Tue, 03 Nov 2026 09:27:52 -0800 (PST) Received: from localhost ([151.60.201.12]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e71b728ddsm25764477f8f.9.2026.11.03.09.27.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Nov 2026 09:27:50 -0800 (PST) X-Mailing-List: linux-api@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=7bf7be77af3bb2ca970a31782cf12336c55eb4edcc365a7f2b8809684642; micalg=pgp-sha512; protocol="application/pgp-signature" Date: Tue, 03 Nov 2026 18:27:48 +0100 Message-Id: Cc: "David Sterba" , "Alexander Viro" , "Christian Brauner" , "Namjae Jeon" , "Sungjong Seo" , "Konstantin Komarov" , "Chris Mason" , "Jan Kara" , "Yuezhang Mo" , "Chuck Lever" , "Darrick J . Wong" , "Sean Smith" , "Andrey Albershteyn" , "Pedro Falcato" , =?utf-8?q?Pali_Roh=C3=A1r?= , , , , , , Subject: Re: [RFC PATCH v3 1/5] vfs: add provenance time (ptime) From: "koraynilay" To: "Amir Goldstein" , "koraynilay" X-Mailer: aerc 0.22.0-0-gc2f86b7abde3 References: <20261101015551.786044-1-koray.fra@gmail.com> <20261101015551.786044-2-koray.fra@gmail.com> In-Reply-To: --7bf7be77af3bb2ca970a31782cf12336c55eb4edcc365a7f2b8809684642 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 On Tue Nov 3, 2026 at 4:14 PM CET, Amir Goldstein wrote: > On Tue, Nov 3, 2026 at 12:13=E2=80=AFPM koraynilay = wrote: >> >> On Mon Nov 2, 2026 at 3:00 PM CET, Amir Goldstein wrote: >> > On Sun, Nov 1, 2026 at 2:57=E2=80=AFAM 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 mt= ime >> >> 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() syscall= s. >> >> >> >> [ This is a re-implementation of the initial patch[1] by Sean Smith >> >> , following the advice[2] from Darrick= J. >> >> Wong of using file_setattr() instead of updatin= g >> >> utimensat() ] >> >> >> >> [1]: https://lore.kernel.org/20260405195007.1306-2-DefendTheDisabled@= gmail.com >> >> [2]: https://lore.kernel.org/20260407014129.GC6192@frogsfrogsfrogs >> >> >> >> Assisted-by: Gemini:3.8-flash-high antigravity-cli-1.4.7 >> >> Signed-off-by: koraynilay >> >> --- >> >> fs/file_attr.c | 33 +++++++++++++++++++++++++++++++-- >> >> fs/stat.c | 2 ++ >> >> include/linux/fileattr.h | 5 +++++ >> >> include/linux/stat.h | 1 + >> >> include/uapi/linux/fs.h | 8 +++++++- >> >> include/uapi/linux/stat.h | 7 ++++++- >> >> 6 files changed, 52 insertions(+), 4 deletions(-) >> >> >> >> diff --git a/fs/file_attr.c b/fs/file_attr.c >> >> index 833e03810b24..c0645cb22bf3 100644 >> >> --- a/fs/file_attr.c >> >> +++ b/fs/file_attr.c >> >> @@ -102,7 +102,7 @@ EXPORT_SYMBOL(vfs_fileattr_get); >> >> static void fileattr_to_file_attr(const struct file_kattr *fa, >> >> struct file_attr *fattr) >> >> { >> >> - __u32 mask =3D FS_XFLAGS_MASK; >> >> + __u32 mask =3D FS_FILE_ATTR_XFLAGS_MASK; >> >> >> >> memset(fattr, 0, sizeof(struct file_attr)); >> >> fattr->fa_xflags =3D fa->fsx_xflags & mask; >> >> @@ -110,6 +110,8 @@ static void fileattr_to_file_attr(const struct fi= le_kattr *fa, >> >> fattr->fa_nextents =3D fa->fsx_nextents; >> >> fattr->fa_projid =3D fa->fsx_projid; >> >> fattr->fa_cowextsize =3D fa->fsx_cowextsize; >> >> + fattr->fa_ptime_sec =3D fa->fsx_ptime.tv_sec; >> >> + fattr->fa_ptime_nsec =3D fa->fsx_ptime.tv_nsec; >> >> } >> >> >> >> /** >> >> @@ -141,15 +143,20 @@ EXPORT_SYMBOL(copy_fsxattr_to_user); >> >> static int file_attr_to_fileattr(const struct file_attr *fattr, >> >> struct file_kattr *fa) >> >> { >> >> - __u64 mask =3D FS_XFLAGS_MASK; >> >> + __u64 mask =3D FS_FILE_ATTR_XFLAGS_MASK; >> > >> > That is not the correct way to extend this API. >> > This fixed mask was added as a placeholder for >> > "We intend to add support for more xflags to selective filesystems": >> > https://lore.kernel.org/linux-fsdevel/20250329143312.1350603-2-amir73i= l@gmail.com/ >> > >> > Please see this POC patch for filesystems to publish their supported >> > xflags mask: >> > https://lore.kernel.org/linux-fsdevel/20250329143312.1350603-3-amir73i= l@gmail.com/ >> >> Thanks, I did not think of adding a dynamic mask like that, I will look >> into it and implement it for v4. >> >> > This will allow callers of file_getattr() to know if the filesystem >> > supports ptime >> > without trying to set it and failing. >> >> So after adding fsx_xflags_mask to file_kattr, every filesystem would >> populate fsx_xflags_mask with all the returned (=3D=3D supported) FS_XFL= AG_* >> in their own specific .fileattr_get, correct? > > Not all filesystems. Just the ones that wish to extend the constant > legacy FS_XFLAGS_MASK. > So just the ones that you change to support XFLAGS_PTIME Ah ok yeah that makes more sense, so like the fileattr_has_fsx_mask() (that checks if fa has fsx, ignoring the suppored/allowed ones specified as second arg) that I added, but in the opposite way: "I advertise only the extra fsx (so only 0 or FS_XFLAG_PTIME rn) that I support". Thanks, koraynilay > Thanks, > Amir. --7bf7be77af3bb2ca970a31782cf12336c55eb4edcc365a7f2b8809684642 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQRJ2XvJtXGwULYEerQ0bnTtJTDoOAUCauoZlAAKCRA0bnTtJTDo OBnVAP9J2oe3Q/z4+CIvNcDvvOtFdyX98jyvuqmiHKySHzb6XAD+N8QVNASksB7a or/C2uBDgyHnZr93FRknmz2MMzGnvwQ= =0YAO -----END PGP SIGNATURE----- --7bf7be77af3bb2ca970a31782cf12336c55eb4edcc365a7f2b8809684642--