From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 1/4] treewide: remove unused address argument from
 pte_alloc functions (v2)
Date: Wed, 24 Oct 2018 10:37:16 +0200
Message-ID: <20181024083716.GN3109@worktop.c.hoisthospitality.com>
References: <20181013013200.206928-1-joel@joelfernandes.org>
 <20181013013200.206928-2-joel@joelfernandes.org>
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Cc: linux-mips@linux-mips.org, Rich Felker <dalias@libc.org>,
 linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
 Catalin Marinas <catalin.marinas@arm.com>,
 Dave Hansen <dave.hansen@linux.intel.com>, Will Deacon <will.deacon@arm.com>,
 Michal Hocko <mhocko@kernel.org>, linux-mm@kvack.org, lokeshgidra@google.com,
 sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org,
 elfring@users.sourceforge.net, Jonas Bonn <jonas@southpole.se>,
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 Yoshinori Sato <ysato@users.sourceforge.jp>, linux-xtensa@linux-xtensa.org,
 linux-hexagon@vger.kernel.org, Helge Deller <deller@gmx.de>,
 "maintainer:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)" <x86@kernel.org>,
 hughd@google.com, "James E.J. Bottomley" <jejb@parisc-linux.org>,
 kasan-dev@googlegroups.com, anton.ivanov@kot-begemot.co.uk,
 Ingo Molnar <mingo@redhat.com>, Geert Uytterhoeven <geert@linux-m
To: "Joel Fernandes (Google)" <joel@joelfernandes.org>
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On Fri, Oct 12, 2018 at 06:31:57PM -0700, Joel Fernandes (Google) wrote:
> This series speeds up mremap(2) syscall by copying page tables at the
> PMD level even for non-THP systems. There is concern that the extra
> 'address' argument that mremap passes to pte_alloc may do something
> subtle architecture related in the future that may make the scheme not
> work.  Also we find that there is no point in passing the 'address' to
> pte_alloc since its unused. So this patch therefore removes this
> argument tree-wide resulting in a nice negative diff as well. Also
> ensuring along the way that the enabled architectures do not do anything
> funky with 'address' argument that goes unnoticed by the optimization.

Did you happen to look at the history of where that address argument
came from? -- just being curious here. ISTR something vague about
architectures having different paging structure for different memory
ranges.