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Date: Fri, 11 Sep 2020 08:19:30 -0300
From: Jason Gunthorpe <jgg@ziepe.ca>
Subject: Re: [RFC PATCH v2 1/3] mm/gup: fix gup_fast with dynamic page table
 folding
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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>

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