linux-kernel - Re: [PATCH 2/2] vfs: support statx(..., NULL, AT_EMPTY

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Message-ID: <ae7309e4fe38896402c282b87b6a2b6c21ff12f2.camel@xry111.site>
Date: Thu, 04 Jul 2024 11:23:17 +0800
From: Xi Ruoyao <xry111@...111.site>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Christian Brauner
 <brauner@...nel.org>, libc-alpha@...rceware.org, "Andreas K. Huettel"
 <dilfridge@...too.org>, Arnd Bergmann <arnd@...db.de>, Mateusz Guzik
 <mjguzik@...il.com>, Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara
 <jack@...e.cz>, linux-kernel@...r.kernel.org,
 linux-fsdevel@...r.kernel.org,  io-uring@...r.kernel.org, Jens Axboe
 <axboe@...nel.dk>,  loongarch@...ts.linux.dev
Subject: Re: [PATCH 2/2] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...)

On Thu, 2024-07-04 at 10:38 +0800, Huacai Chen wrote:
> > So if a LoongArch Glibc is built with Linux kernel headers >= 6.11,
> > it'll use fstatat **even configured --with-kernel=5.19** and fail to run
> > on Linux kernel <= 6.10.  This will immediately blow up building Linux
> > From Scratch on a host distro with an "old" kernel.
> The patch which adds newstat back will CC the stable list and be
> backported to old kernels.

AFAIK in Glibc --enable-kernel=x.y (not with, I was too sleepy
yesterday) means it'll work with even x.y.0.  And even if we "re-
purpose" x.y to mean "the latest x.y patch release" people can still
explicitly spell the patch level, like --enable-kernel=5.19.0.

Thus we still need to handle this in Glibc.

And the backport will raise another question: assume 6.6.40 gets the
backport, what should we do with --enable-kernel=6.6.40?  Maybe we
should we assume newfstatat is available but then people will start to
complain "hey 6.9.7 > 6.6.40 but my Glibc configured with --enable-
kernel=6.6.40 does not work on 6.9.7"...

To me the only rational way seems only assuming 6.11 or later has
newfstatat on LoongArch.

-- 
Xi Ruoyao <xry111@...111.site>
School of Aerospace Science and Technology, Xidian University