linux-kernel - Re: [PATCH] x86: fix PAE pmd

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Message-Id: <1210272164.7905.66.camel@nimitz.home.sr71.net>
Date:	Thu, 08 May 2008 11:42:44 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Nishanth Aravamudan <nacc@...ibm.com>
Cc:	Hans Rosenfeld <hans.rosenfeld@....com>,
	Hugh Dickins <hugh@...itas.com>, Ingo Molnar <mingo@...e.hu>,
	Jeff Chua <jeff.chua.linux@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Gabriel C <nix.or.die@...glemail.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] x86: fix PAE pmd_bad bootup warning


On Thu, 2008-05-08 at 10:16 -0700, Nishanth Aravamudan wrote:
> 
> Dunno, seems quite clear that the bug is in pagemap_read(), not any
> hugepage code, and that the simplest fix is to make pagemap_read() do
> what the other walker-callers do, and skip hugepage regions.

Agreed, this certainly isn't a huge page bug.

But, I do think it is absolutely insane to have pmd_clear_bad() going
after perfectly good hugetlb pmds.  The way it is set up now, people are
bound to miss the hugetlb pages because just about every single
pagetable walk has to be specially coded to handle or avoid them.  We
obviously missed it, here, and we had two good examples in the same
file! :)

-- Dave

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