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.
next prev parent reply other threads:[~2006-09-20 3:06 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-14 22:55 [RFC] page fault retry with NOPAGE_RETRY 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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