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Date: Fri, 23 Mar 2001 08:21:35 -0300 (BRST)
From: Rik van Riel <riel@conectiva.com.br>
To: Richard Jerrell <jerrell@missioncriticallinux.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/memory.c, 2.4.1 : memory leak with swap cache (updated)
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On Fri, 23 Mar 2001, Richard Jerrell wrote:
> > Your idea is nice, but the patch lacks a few things:
> > 
> > - SMP locking, what if some other process faults in this page
> >   between the atomic_read of the page count and the test later?
> 
> It can't happen.  free_pte is called with the page_table_lock held in 
> addition to having the mmap_sem downed.

The page_table_lock and the mmap_sem only protect the *current*
task. Think about something like an apache with 500 children who
COW share the same page...

> > - testing if our process is the _only_ user of this swap page,
> >   for eg. apache you'll have lots of COW-shared pages .. it would
> >   be good to keep the page in memory for our siblings
> 
> This is already done in free_page_and_swap_cache.

Ok ...

regards,

Rik
--
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However, without VM there's truly nothing to lose...

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