From: Andrew Morton <akpm@digeo.com>
To: Dave McCracken <dmccr@us.ibm.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 2.5.63] Teach page_mapped about the anon flag
Date: Mon, 3 Mar 2003 13:12:10 -0800 [thread overview]
Message-ID: <20030303131210.36645af6.akpm@digeo.com> (raw)
In-Reply-To: <103400000.1046725581@baldur.austin.ibm.com>
Dave McCracken <dmccr@us.ibm.com> wrote:
>
>
> --On Thursday, February 27, 2003 14:24:50 -0800 Andrew Morton
> <akpm@digeo.com> wrote:
>
> > I'm just looking at page_mapped(). It is now implicitly assuming that the
> > architecture's representation of a zero-count atomic_t is all-bits-zero.
> >
> > This is not true on sparc32 if some other CPU is in the middle of an
> > atomic_foo() against that counter. Maybe the assumption is false on other
> > architectures too.
> >
> > So page_mapped() really should be performing an atomic_read() if that is
> > appropriate to the particular page. I guess this involves testing
> > page->mapping. Which is stable only when the page is locked or
> > mapping->page_lock is held.
> >
> > It appears that all page_mapped() callers are inside lock_page() at
> > present, so a quick audit and addition of a comment would be appropriate
> > there please.
>
> I'm not at all confident that page_mapped() is adequately protected.
It is. All callers which need to be 100% accurate are under
pte_chain_lock().
> Here's a patch that explicitly handles the atomic_t case.
OK.. But it increases dependency on PageAnon. Wasn't the plan to remove
that at some time?
next prev parent reply other threads:[~2003-03-03 21:05 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-02-27 10:59 2.5.63-mm1 Andrew Morton
2003-02-27 21:22 ` Rising io_load results 2.5.63-mm1 Con Kolivas
2003-02-27 21:44 ` Andrew Morton
2003-02-27 22:01 ` Dave McCracken
2003-02-27 22:24 ` Andrew Morton
2003-03-03 21:06 ` [PATCH 2.5.63] Teach page_mapped about the anon flag Dave McCracken
2003-03-03 21:12 ` Andrew Morton [this message]
2003-03-03 21:24 ` Dave McCracken
2003-03-03 21:35 ` Andrew Morton
2003-03-03 21:52 ` Dave McCracken
2003-03-03 22:15 ` Andrew Morton
2003-03-04 18:32 ` [PATCH 2.5.63] Make objrmap mapcount non-atomic Dave McCracken
2003-02-27 23:56 ` Rising io_load results Re: 2.5.63-mm1 Con Kolivas
2003-02-28 0:06 ` Andrew Morton
2003-02-28 0:28 ` Con Kolivas
2003-02-28 7:46 ` Duncan Sands
2003-02-28 8:06 ` Andrew Morton
2003-02-28 12:48 ` Hugh Dickins
2003-02-28 15:56 ` Dave McCracken
2003-02-28 0:17 ` 2.5.63-mm1 Ed Tomlinson
2003-02-28 0:46 ` 2.5.63-mm1 Andrew Morton
2003-02-28 12:16 ` 2.5.63-mm1 steven roemen
2003-02-28 12:24 ` 2.5.63-mm1 Andrew Morton
[not found] ` <3E5F7DAD.2080306@cyberone.com.au>
[not found] ` <200302282227.56311.tomlins@cam.org>
2003-03-01 15:04 ` [PATCH] tiobench on UP and ptg-D3-mm1 Ed Tomlinson
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