linux-kernel - Re: [RFC][PATCHSET v3] non-recursive pathname resolution & RCU symlinks

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Message-ID: <CA+55aFwyBZW6cnP6Otx2mP2HAuU6OtJoGBeSQUrp0kR+4bUNOA@mail.gmail.com>
Date:	Thu, 14 May 2015 16:24:13 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jeremy Allison <jra@...ba.org>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Neil Brown <neilb@...e.de>
Subject: Re: [RFC][PATCHSET v3] non-recursive pathname resolution & RCU symlinks

On Thu, May 14, 2015 at 3:09 PM, Jeremy Allison <jra@...ba.org> wrote:
>
> Of course we tell people to just set their filesystems
> up using mkfs.xfs -n version=ci :-).

So ASCII-only case-insensitivity is sufficient for you guys?

Doing case-insensitive lookups at a vfs layer level wouldn't be
impossible (add some new lookup flag, so it would *not* be
per-filesystem, it would be per-operation!), but the *full*
case-insensitivity space in utf-8 is too much to expect. Especially
since different people have different opinions on what it even should
be.

What else is problematic? I think you want an error on symlinks in the
middle, right? So that you can do those manually? I also assume you
don't like to follow ".." due to containment issues?

Adding (again per-lookup) flags for "no symlinks" and "no dotdot")
would be trivial (much more so than the case insensitivity). Would you
require "error out on non-ascii characters" too, to then handle the
complex cases by hand?

Obviously per-lookup flags means that you can't just use "stat()", it
would be "fstatat()".

I dunno. But it *may* be worth it to really try to give samba what it
wants. Of course, if samba is happy doing all the name caching in user
space, then that's not worth worrying about.

And the reason I don't use samba myself is that I'm not a fan of
network filesystems. I want my filesystems low-latency and right there
on the local ssd, thank you very much. But if you have some
local-machine benchmarkign thing you use, I guess I could use that to
see what the profile looks like...

                         Linus
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