linux-kernel - Re: [PATCH] mm: allow huge kvmalloc() calls if they're accounted to memcg

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Date:   Sat, 16 Oct 2021 19:53:35 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     KVM list <kvm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Willy Tarreau <w@....eu>, Kees Cook <keescook@...omium.org>,
        syzbot+e0de2333cbf95ea473e8@...kaller.appspotmail.com
Subject: Re: [PATCH] mm: allow huge kvmalloc() calls if they're accounted to
 memcg

On 16/10/21 17:39, Linus Torvalds wrote:
> The big allocation warnings are not about whether we have the memory
> or not, or about whether it's accounted or not.
> It's about bugs and overflows. Which we've had.

Yes, I understand that...

> At least GFP_NOWARN would be somewhat sensible - although still wrong.

... and it also seemed wrong to overload GFP_NOWARN.

> It should really be about "I've been careful with growing my
> allocations", not about whether accounting or similar should be
> disabled. If the allocations really are expected to be that big, and
> it's actually valid, just do vmalloc(), which doesn't warn.
Sounds good, and you'll get a pull request for that tomorrow.  Then I'll 
send via Andrew a patch to add __vcalloc, so that the accounting is 
restored.

Paolo