Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Fri, 11 Sep 2020 08:19:30 -0300
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     peterz@infradead.org
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Dave Hansen <dave.hansen@intel.com>,
        John Hubbard <jhubbard@nvidia.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Russell King <linux@armlinux.org.uk>,
        Mike Rapoport <rppt@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Jeff Dike <jdike@addtoit.com>,
        Richard Weinberger <richard@nod.at>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Arnd Bergmann <arnd@arndb.de>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        linux-x86 <x86@kernel.org>,
        linux-arm <linux-arm-kernel@lists.infradead.org>,
        linux-power <linuxppc-dev@lists.ozlabs.org>,
        linux-sparc <sparclinux@vger.kernel.org>,
        linux-um <linux-um@lists.infradead.org>,
        linux-s390 <linux-s390@vger.kernel.org>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>
Subject: Re: [RFC PATCH v2 1/3] mm/gup: fix gup_fast with dynamic page table
 folding
Message-ID: <20200911111930.GS87483@ziepe.ca>
References: <20200909192534.442f8984@thinkpad>
 <20200909180324.GI87483@ziepe.ca>
 <20200910093925.GB29166@oc3871087118.ibm.com>
 <CAHk-=wh4SuNvThq1nBiqk0N-fW6NsY5w=VawC=rJs7ekmjAhjA@mail.gmail.com>
 <20200910181319.GO87483@ziepe.ca>
 <CAHk-=wh3SjOE2r4WCfagL5Zq4Oj4Jsu1=1jTTi2GxGDTxP-J0Q@mail.gmail.com>
 <20200910211010.46d064a7@thinkpad>
 <CAHk-=wg3ggXU98Mnv-ss-hEcvUNc9vCtgSRc7GpcGfvyOw_h3g@mail.gmail.com>
 <20200910215921.GP87483@ziepe.ca>
 <20200911070939.GB1362448@hirez.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200911070939.GB1362448@hirez.programming.kicks-ass.net>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Sep 11, 2020 at 09:09:39AM +0200, peterz@infradead.org wrote:
> On Thu, Sep 10, 2020 at 06:59:21PM -0300, Jason Gunthorpe wrote:
> > So, I suggest pXX_offset_unlocked()
> 
> Urgh, no. Elsewhere in gup _unlocked() means it will take the lock
> itself (get_user_pages_unlocked()) -- although often it seems to mean
> the lock is already held (git grep _unlocked and marvel).
>
> What we want is _lockless().

This is clear to me!

Thanks,
Jason