linux-kernel - Re: [PATCH v4 00/15] follow

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Message-ID: <20201029092800.GA494@infradead.org>
Date:   Thu, 29 Oct 2020 09:28:00 +0000
From:   Christoph Hellwig <hch@...radead.org>
To:     Daniel Vetter <daniel.vetter@...ll.ch>
Cc:     Christoph Hellwig <hch@...radead.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        KVM list <kvm@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>
Subject: Re: [PATCH v4 00/15] follow_pfn and other iomap races

On Thu, Oct 29, 2020 at 10:25:16AM +0100, Daniel Vetter wrote:
> On Thu, Oct 29, 2020 at 9:57 AM Christoph Hellwig <hch@...radead.org> wrote:
> >
> > Maybe I'm missing something, but shouldn't follow_pfn be unexported
> > at the end of the series?
> 
> kvm is a legit user and modular afaict. But since you can't use this
> without an mmu_notifier anyway (or digging around in pagetable
> locking), maybe it should be EXPORT_SYMBOL_GPL now at least?

I think it should then take the notifier as an argument even if it isn't
diretly used as a safety check, and get a new name describing it.

EXPORT_SYMBOL_GPL is probably ok for now, but I'm drafting a new
EXPORT_SYMBOL_FOR_MODULE() which will export symbols that can only be
used by one specific module, with kvm being a prime user due to all
the odd exports it requires that aren't really the kernel interface by
any normal means.