From: Hugh Dickins <hugh@veritas.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>,
Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [patch] mm: madvise avoid exclusive mmap_sem
Date: Fri, 13 Apr 2007 21:08:15 +0100 (BST) [thread overview]
Message-ID: <Pine.LNX.4.64.0704132101300.14508@blonde.wat.veritas.com> (raw)
In-Reply-To: <20070413115719.2bdf5705.akpm@linux-foundation.org>
On Fri, 13 Apr 2007, Andrew Morton wrote:
> On Thu, 12 Apr 2007 02:56:38 +0200
> Nick Piggin <npiggin@suse.de> wrote:
>
> > Avoid down_write of the mmap_sem in madvise when we can help it.
>
> Are we sure that running zap_page_range() under down_read() is safe?
> For hugepage regions too?
madvise_dontneed just says -EINVAL on a VM_HUGETLB vma, so I didn't
check the hugepage case further, it doesn't reach the zap_page_range.
We can indeed be sure that running zap_page_range on a normal vma
is safe under down_read (as opposed to the down_write there before),
because file truncation runs it without taking mmap_sem at all.
Hugh
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prev parent reply other threads:[~2007-04-13 20:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-12 0:56 Nick Piggin
2007-04-13 18:57 ` Andrew Morton
2007-04-13 20:08 ` Hugh Dickins [this message]
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