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[133.130.115.230]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-207946d27ffsm78717035ad.121.2024.09.19.05.18.24 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 19 Sep 2024 05:18:29 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3776.700.51\)) Subject: Re: [PATCH 0/3] Backport statx(..., NULL, AT_EMPTY_PATH, ...) From: Miao Wang In-Reply-To: <2024091900-sloppy-swept-0a2e@gregkh> Date: Thu, 19 Sep 2024 20:18:10 +0800 Cc: Xi Ruoyao , stable@vger.kernel.org, Mateusz Guzik , Christian Brauner , Alexander Viro , Jan Kara , Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , =?utf-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , linux-fsdevel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20240918-statx-stable-linux-6-10-y-v1-0-8364a071074f@gmail.com> <2024091801-segment-lurk-e67b@gregkh> <2024091900-sloppy-swept-0a2e@gregkh> To: Greg Kroah-Hartman X-Mailer: Apple Mail (2.3776.700.51) > 2024=E5=B9=B49=E6=9C=8819=E6=97=A5 19:18=EF=BC=8CGreg Kroah-Hartman = =E5=86=99=E9=81=93=EF=BC=9A >=20 > On Thu, Sep 19, 2024 at 01:37:17AM +0800, Xi Ruoyao wrote: >> On Wed, 2024-09-18 at 19:33 +0200, Greg Kroah-Hartman wrote: >>> On Wed, Sep 18, 2024 at 10:01:18PM +0800, Miao Wang via B4 Relay = wrote: >>>> Commit 0ef625bba6fb ("vfs: support statx(..., NULL, AT_EMPTY_PATH, >>>> ...)") added support for passing in NULL when AT_EMPTY_PATH is = given, >>>> improving performance when statx is used for fetching stat = informantion >>>> from a given fd, which is especially important for 32-bit = platforms. >>>> This commit also improved the performance when an empty string is = given >>>> by short-circuiting the handling of such paths. >>>>=20 >>>> This series is based on the commits in the Linus=E2=80=99 tree. = Sligth >>>> modifications are applied to the context of the patches for cleanly >>>> applying. >>>>=20 >>>> Tested-by: Xi Ruoyao >>>> Signed-off-by: Miao Wang >>>=20 >>> This really looks like a brand new feature wanting to be backported, = so >>> why does it qualify under the stable kernel rules as fixing = something? >>>=20 >>> I am willing to take some kinds of "fixes performance issues" new >>> features when the subsystem maintainers agree and ask for it, but = that >>> doesn't seem to be the case here, and so without their approval and >>> agreement that this is relevant, we can't accept them. >>=20 >> Unfortunately the performance issue fix and the new feature are in = the >> same commit. Is it acceptable to separate out the performance fix = part >> for stable? (Basically remove "if (!path) return true;" from the 1st >> patch.) >=20 > What prevents you, if you wish to have the increased performance, from > just moving to a newer kernel version? We add new features and > improvements like this all the time, why is this one so special to > warrant doing backports. Especially with no maintainer or subsystem > developer asking for this to be done? We all know the long process from a new improvement getting into the = mainline kernel to landing in users' devices. Considering 32-bit archectures = which lacks 64-bit time support in fstat(), statx(fd, AT_EMPTY_PATH) is heavily = relied on. My intention on putting up this backport is that to quicken this = process, benefiting these users. Another reason is about loongarch. fstat() was not included in loongarch initially, until 6.11. Although the re-inclusion of fstat() is = backported to stable releases, we still have implementation problems on the glibc = side, that loongarch is the only architecture that may lack the support of fstat. = If dynamic probing of the existence of fstat() is implemented, this code = path would be only effective on loongarch, adding another layer of mess to = the current fstat implementation and adding maintenance burden to glibc = maintainers. Instead, if we choose to utilize statx(fd, NULL, AT_EMPTY_PATH), even if = using dynamic probing, loongarch and all other 32-bit architectures using = statx() for fstat() can benefit from this. Based on the same reason why you have accepted the re-inclusion of fstat = on loongarch into the stable trees, I believe it would be potentially = possible to let the statx(..., NULL, AT_EMPTY_PATH, ...) get into the stable trees = as well. Thanks again for your considering this. Since VFS maintainers are being = looped in the thread, if their approval is necessary, I'm happy to listen to = their opinions. Cheers, Miao Wang