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List:       linux-mm
Subject:    Re: [RFC] reduce hugetlb_instantiation_mutex usage
From:       Hugh Dickins <hugh () veritas ! com>
Date:       2006-10-31 12:48:13
Message-ID: Pine.LNX.4.64.0610311239460.6523 () blonde ! wat ! veritas ! com
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On Tue, 31 Oct 2006, 'David Gibson' wrote:
> On Mon, Oct 30, 2006 at 09:15:20PM -0800, Chen, Kenneth W wrote:
> > 
> > Instead, I'm asking how private mapping protect race between file truncation
> > and fault? For shared mapping, it is clear to me that we are using lock_page
> > to protect file truncate with fault.  But I don't see that protection with
> > private mapping in current upstream kernel.
> 
> Oh, ok.  I can't see how it matters in the PRIVATE case, given that
> truncate() won't, and shouldn't, truncate privately mapped pages.

Bzzt, it does and should (unless we decide to make hugetlbfs pages diverge
from the standard for ordinary pages in this respect - could do, but that
would require thought of its own).  If you've been thinking otherwise,
that may explain why some of the accounting goes wrong.

Hugh

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