Date: Mon, 6 Feb 2006 22:29:59 +0000 (GMT)
From: Hugh Dickins <hugh@veritas.com>
To: Roland Dreier <rolandd@cisco.com>
cc: Kai Makisara <Kai.Makisara@kolumbus.fi>, Willem Riede <osst@riede.org>,
       linux-kernel@vger.kernel.org, openib-general@openib.org
Subject: Re: [git patch review 2/2] IB: Don't doublefree pages from scatterlist
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Message-ID: <Pine.LNX.4.61.0602062221200.3844@goblin.wat.veritas.com>
References: <1139070837112-3fe13a3288c20f5c@cisco.com>
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On Sat, 4 Feb 2006, Roland Dreier wrote:

> On some architectures, mapping the scatterlist may coalesce entries:
> if that coalesced list is then used for freeing the pages afterwards,
> there's a danger that pages may be doubly freed (and others leaked).
> 
> Fix Infiniband's __ib_umem_release by freeing from a separate array
> beyond the scatterlist: IB_UMEM_MAX_PAGE_CHUNK lowered to fit one page.

It's now looking like this change won't be needed after all: Andi has
just posted a patch in the "ipr" thread which should stop x86_64 from
interfering with the scatterlist *page,offset,length fields, so what
IB and others were doing should then work safely (current thinking is
that x86_64 is the only architecture which coalesced in that way).

Hugh
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