linux-ext4 - Re: [f2fs-dev] [PATCH v6 0/9] Support negative dentries on case-insensitive ext4 and f2fs

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Date: Tue, 21 Nov 2023 02:27:34 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Christian Brauner <brauner@...nel.org>,
	Gabriel Krisman Bertazi <krisman@...e.de>, tytso@....edu,
	linux-f2fs-devel@...ts.sourceforge.net, ebiggers@...nel.org,
	linux-fsdevel@...r.kernel.org, jaegeuk@...nel.org,
	linux-ext4@...r.kernel.org
Subject: Re: [f2fs-dev] [PATCH v6 0/9] Support negative dentries on
 case-insensitive ext4 and f2fs

On Mon, Nov 20, 2023 at 10:07:51AM -0800, Linus Torvalds wrote:

> Well, we all know - very much including Al - that Al isn't always the
> most responsive person, and tends to have his own ratholes that he
> dives deep into.

FWIW, the right now I'm getting out of one of those - rename() deadlocks
fun.  Will post that, assuming it survives local beating, then post
the dcache stuff and other branches (all rebased by now).

Other ratholes - d_name/d_parent audit is about halfway through -
we do have fun shite in quite a few ->d_revalidate() instances (UAF,
etc.); RCU pathwalk methods need to be re-audited; the fixes caught
in the last cycle are either in mainline by now, or rebased.

But that stuff is relatively easy to suspend for a few days.

> Of course, "do it in shared generic code" doesn't tend to really fix
> the braindamage, but at least it's now shared braindamage and not
> spread out all over. I'm looking at things like
> generic_ci_d_compare(), and it hurts to see the mindless "let's do
> lookups and compares one utf8 character at a time". What a disgrace.
> Somebody either *really* didn't care, or was a Unicode person who
> didn't understand the point of UTF-8.
> 
> Oh well. I guess people went "this is going to suck anyway, so let's
> make sure it *really* sucks".
> 

> The patches look fine to me. Al - do you even care about them?

I will review that series; my impression from the previous iterations
had been fairly unpleasant, TBH, but I hadn't rechecked since April
or so.

Re dcache conflicts - see #untested-pile-dcache; most the dcache-affecting
stuff should be there.  One intersting exception is the general helper
for safely picking parent/parent's inode/entry name for ->d_revalidate()
use;  we have the parent-related part boilerplated, but the name side
tends to be missing.  That's still being tweaked, looking for sane
calling conventions.