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Date: Thu, 13 Nov 2008 04:44:25 +0100 From: Nick Piggin <npiggin@...e.de> To: "Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com> Cc: Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>, H Peter Anvin <hpa@...or.com>, Hugh Dickins <hugh@...itas.com>, Roland Dreier <rdreier@...co.com>, Jesse Barnes <jbarnes@...tuousgeek.org>, Jeremy Fitzhardinge <jeremy@...p.org>, Arjan van de Ven <arjan@...radead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Siddha, Suresh B" <suresh.b.siddha@...el.com> Subject: Re: [patch 2/8] x86 PAT: set VM_PFNMAP flag in vm_insert_pfn On Wed, Nov 12, 2008 at 04:02:47PM -0800, Pallipadi, Venkatesh wrote: > > > >-----Original Message----- > >From: Nick Piggin [mailto:npiggin@...e.de] > >Sent: Wednesday, November 12, 2008 3:23 PM > >To: Pallipadi, Venkatesh > >Cc: Ingo Molnar; Thomas Gleixner; H.Peter Anvin; Hugh Dickins; > >Roland Dreier; Jesse Barnes; Jeremy Fitzhardinge; Arjan van de > >Ven; linux-kernel@...r.kernel.org; Siddha, Suresh B > >Subject: Re: [patch 2/8] x86 PAT: set VM_PFNMAP flag in vm_insert_pfn > > > >You have to be careful of this, because it can be called with mmap_sem > >held for read only. Hmm, I guess vm_insert_page is doing the > >same thing. > >Probably mostly works because all other modifiers of vm_flags > >are holding > >mmap_sem. > > Yes. I did the patch looking at vm_insert_page doing similar thing. > > > > >However, in some cases, code can do vm_insert_pfn and vm_insert_page > >(actually hmm, no vm_insert_mixed actually should cover most of those > >cases). > > > >Still, I'd be much happier if we could make these into BUG_ON, and then > >teach callers to set it in their .mmap routines. > > Actually, vm_insert_pfn() already has a BUG_ON() at the start for cases > where neither (or both) MIXEDMAP and PFNMAP is not set. So, that should > cover the case we are worried about it here and we can eliminate this > patch altogether. Only part I am not sure about is why we are looking > for MIXEDMAP here. Shouldn't they be using vm_insert_mixed instead? They should, but it will do an inesrt_pfn in some cases, won't it? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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