linux-kernel - Re: FYI: path walking optimizations pending for 6.11

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Message-ID: <CAHk-=wiKCppvYcjHRivLbw2uPELEuEdythi_bkK9P7oF0wJ4Yw@mail.gmail.com>
Date: Tue, 9 Jul 2024 09:24:27 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Mark Rutland <mark.rutland@....com>
Cc: Christian Brauner <brauner@...nel.org>, Al Viro <viro@...iv.linux.org.uk>, 
	linux-fsdevel <linux-fsdevel@...r.kernel.org>, "the arch/x86 maintainers" <x86@...nel.org>, 
	Linux ARM <linux-arm-kernel@...ts.infradead.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: FYI: path walking optimizations pending for 6.11

On Tue, 9 Jul 2024 at 07:28, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> > For the sake of review, would you be happy to post the uaccess and
> > runtime-constants patches to the list again? I think there might be some
> > remaining issues with (real) PAN and we might need to do a bit more
> > preparatory work there.
>
> Sure. I'll fix that silly left-over store, and post again.

I only posted the (unchanged) arm64-uaccess series and the (fixed,as
per your comment today) runtime-constants one. And I only posted it to
the linux-arm-kernel list, not wanting to bother everybody.

I have two other branches in my git tree if people care:
link_path_walk and word-at-a-time. The word-at-a-time one does touch
arm64 files too, but it's pretty trivial:

 arch/arm64/include/asm/word-at-a-time.h | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

and really only involves a better instruction choice. It really only
matters if you end up looking at the generated code of link_path_walk
and strncpy_from_user().

The commit message at the top of that branch is a lot more verbose
than the actual change, because I ended up just explaining the
different phases of the zero detection more than the actual trivial
change to it.

All four branches are available in my regular tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

as 'arm64-uaccess', 'link_path_walk', 'runtime-constants', and 'word-at-a-time'.

But unlike my normal mainline branch, I still rebase these based on
feedback, so consider them unstable.

IOW, don't pull them into any tree to be used: just use "git fetch" to
look at the branches in your local tree instead, or use it for some
ephemeral testing branch.

                 Linus