linux-kernel - Re: [RFC V2] mm: Generalize notify_page

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Date:   Thu, 6 Jun 2019 08:10:28 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Matthew Wilcox <willy@...radead.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        x86@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Mark Rutland <mark.rutland@....com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Paul Mackerras <paulus@...ba.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [RFC V2] mm: Generalize notify_page_fault()



On 06/05/2019 04:53 PM, Matthew Wilcox wrote:
> On Wed, Jun 05, 2019 at 09:19:22PM +1000, Michael Ellerman wrote:
>> Anshuman Khandual <anshuman.khandual@....com> writes:
>>> Similar notify_page_fault() definitions are being used by architectures
>>> duplicating much of the same code. This attempts to unify them into a
>>> single implementation, generalize it and then move it to a common place.
>>> kprobes_built_in() can detect CONFIG_KPROBES, hence notify_page_fault()
>>> need not be wrapped again within CONFIG_KPROBES. Trap number argument can
>>> now contain upto an 'unsigned int' accommodating all possible platforms.
>> ...
>>
>> You've changed several of the architectures from something like above,
>> where it disables preemption around the call into the below:
>>
>>
>> Which skips everything if we're preemptible. Is that an equivalent
>> change? If so can you please explain why in more detail.
> 
> See the discussion in v1 of this patch, which you were cc'd on.
> 
> I agree the description here completely fails to mention why the change.
> It should mention commit a980c0ef9f6d8c.

I will update the commit message to include an explanation for this new
preempt behavior in the generic definition.