linux-kernel - Re: [PATCH 07/32] mm: Bring back vmalloc

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Message-ID: <20230620201851.qrcabl327mrofygb@moria.home.lan>
Date:   Tue, 20 Jun 2023 16:18:51 -0400
From:   Kent Overstreet <kent.overstreet@...ux.dev>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org,
        "linux-bcachefs@...r.kernel.org" <linux-bcachefs@...r.kernel.org>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        "hch@...radead.org" <hch@...radead.org>, linux-mm@...ck.org,
        Kees Cook <keescook@...omium.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH 07/32] mm: Bring back vmalloc_exec

On Tue, Jun 20, 2023 at 11:48:26AM -0700, Dave Hansen wrote:
> >> No, I'm saying your concerns are baseless and too vague to
> >> address.
> > If you don't address them, the NAK will stand forever, or at least
> > until a different group of people take over x86 maintainership.
> > That's fine with me.
> 
> I've got a specific concern: I don't see vmalloc_exec() used in this
> series anywhere.  I also don't see any of the actual assembly that's
> being generated, or the glue code that's calling into the generated
> assembly.
>
> I grepped around a bit in your git trees, but I also couldn't find it in
> there.  Any chance you could help a guy out and point us to some of the
> specifics of this new, tiny JIT?

vmalloc_exec() has already been dropped from the patchset - I'll switch
to the new jit allocator when that's available and doing sub-page
allocations.

I can however point you at the code that generates the unpack functions:

https://evilpiepirate.org/git/bcachefs.git/tree/fs/bcachefs/bkey.c#n727

> >> Andy, I replied explaining the difference between text_poke() and
> >> text_poke_sync(). It's clear you have no idea what you're talking about,
> >> so I'm not going to be wasting my time on further communications with
> >> you.
> 
> One more specific concern: This comment made me very uncomfortable and
> it read to me very much like a personal attack, something which is
> contrary to our code of conduct.

It's not; I prefer to be direct than passive aggressive, and if I have
to bow out of a discussion that isn't going anywhere I feel I owe an
explanation of _why_. Too much conflict avoidance means things don't get
resolved.

And Andy and I are talking on IRC now, so things are proceeding in a
better direction.