From: Andrew Morton <akpm@osdl.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Mike Waychison <mikew@google.com>,
linux-mm@kvack.org,
Linux Kernel list <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@osdl.org>
Subject: Re: [RFC] page fault retry with NOPAGE_RETRY
Date: Tue, 19 Sep 2006 20:05:33 -0700 [thread overview]
Message-ID: <20060919200533.2874ce36.akpm@osdl.org> (raw)
In-Reply-To: <1158717429.6002.231.camel@localhost.localdomain>
On Wed, 20 Sep 2006 11:57:09 +1000
Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> > You forget that the point of this optimisation is to undo mmap_sem while
> > waiting on the disk IO. Once we've done that we cannot go looking at ptes
> > or vmas: another thread could have munapped the whole lot or anything.
> > (And we always need to be afraid of use_mm()..)
>
> Wait wait .. .we don't need to have the mmap sem to -look- at a PTE.
The pte resides in a pagetable page. Once we've dropped mmap_sem, that
pagetable page might not be there any more: munmap() might have freed it.
We have to retake mmap_sem, do a find_vma() and a new pagetable walk.
There are some optimisations we could make to avoid all of that in the
common case, but this is the conceptual behaviour.
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next prev parent reply other threads:[~2006-09-20 3:05 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-14 22:55 Benjamin Herrenschmidt
2006-09-15 0:19 ` Linus Torvalds
2006-09-15 7:11 ` Andrew Morton
2006-09-15 7:35 ` Andrew Morton
2006-09-15 13:30 ` Hugh Dickins
2006-09-16 1:03 ` Benjamin Herrenschmidt
2006-09-19 23:35 ` Mike Waychison
2006-09-19 23:50 ` Benjamin Herrenschmidt
2006-09-19 23:59 ` Andrew Morton
2006-09-20 0:06 ` Benjamin Herrenschmidt
2006-09-20 0:05 ` Benjamin Herrenschmidt
2006-09-20 0:21 ` Andrew Morton
2006-09-20 1:57 ` Benjamin Herrenschmidt
2006-09-20 3:05 ` Andrew Morton [this message]
2006-09-20 5:04 ` Benjamin Herrenschmidt
2006-09-20 5:26 ` Andrew Morton
2006-09-20 6:54 ` Benjamin Herrenschmidt
2006-09-20 17:53 ` Andrew Morton
2006-09-21 22:05 ` Benjamin Herrenschmidt
2006-09-21 22:41 ` Andrew Morton
2006-09-21 23:09 ` Benjamin Herrenschmidt
2006-09-23 14:21 ` Hugh Dickins
2006-09-23 19:46 ` Andrew Morton
2006-09-23 22:35 ` Benjamin Herrenschmidt
2006-09-20 5:06 ` Benjamin Herrenschmidt
2006-09-20 1:14 ` Mike Waychison
2006-09-20 2:02 ` Benjamin Herrenschmidt
2006-09-15 21:35 ` Arnd Bergmann
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