Re: [PATCH] Fix virtual address handling in hugetlb fault

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 22 Nov 2011 09:32:38 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> On Mon, 21 Nov 2011 14:27:20 -0800
> Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > On Mon, 21 Nov 2011 19:48:32 +0900
> > KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > 
> > > >From 7c29389be2890c6b6934a80b4841d07a7014fe26 Mon Sep 17 00:00:00 2001
> > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > > Date: Mon, 21 Nov 2011 19:45:27 +0900
> > > Subject: [PATCH] Fix virtual address handling in hugetlb fault
> > > 
> > > handle_mm_fault() passes 'faulted' address to hugetlb_fault().
> > > Then, the address is not aligned to hugepage boundary.
> > > 
> > > Most of functions for hugetlb pages are aware of that and
> > > calculate an alignment by itself. Some functions as copy_user_huge_page(),
> > > and clear_huge_page() doesn't handle alignment by themselves.
> > > 
> > > This patch make hugeltb_fault() to calculate the alignment and pass
> > > aligned addresss (top address of a faulted hugepage) to functions.
> > > 
> > 
> > Does this actually fix any known user-visible misbehaviour?
> > 
> 
> I just found this at reading codes. And I know 'vaddr' is ignored
> in most of per-arch implemantation of clear_user_highpage().
> It seems, in some arch, vaddr is used for flushing cache. Now,
> CONFIG_HUGETLBFS can be set on x86,powerpc,ia64,mips,sh,sparc,tile. (by grep)
> 
> it seems mips and sh uses vaddr in clear_user_(high)page.

OK.  Those architectures are probably OK with "any address within the
page" anyway.

I'm actually trying to work out which kernel(s) we should merge this
into ;)

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