From: Martin Schwidefsky <schwidefsky@de.ibm.com>
To: Matt Mackall <mpm@selenic.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Gerald Schaefer <gerald.schaefer@de.ibm.com>,
akpm@linux-foundation.org
Subject: Re: [PATCH] acquire mmap semaphore in pagemap_read.
Date: Thu, 12 Mar 2009 16:54:51 +0100 [thread overview]
Message-ID: <20090312165451.1a7ef22f@skybase> (raw)
In-Reply-To: <1236871414.3213.50.camel@calx>
On Thu, 12 Mar 2009 10:23:34 -0500
Matt Mackall <mpm@selenic.com> wrote:
> Well it means we may have to reintroduce the very annoying double
> buffering from various earlier implementations. But let's leave this
> discussion until after we've figured out what to do about the walker
> code.
About the walker code. I've realized that there is another way to fix
this. The TASK_SIZE definition is currently used for two things: 1) as
a maximum mappable address, 2) the size of the address space for a
process. And there lies a problem: while a process is using a reduced
page table 1) and 2) differ. If I make TASK_SIZE give you the current
size of the address space then it is not possible to mmap an object
beyond 4TB and the page table upgrade never happens. If I make
TASK_SIZE return the maximum mappable address the page table walker
breaks. The solution could be to introduce MAX_TASK_SIZE and use that
in the mmap code to find out what can be mapped.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
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next prev parent reply other threads:[~2009-03-12 15:58 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-12 10:33 [PATCH] acquire mmap semaphore in pagemap_read Martin Schwidefsky
2009-03-12 11:45 ` Alexey Dobriyan
2009-03-12 11:54 ` Martin Schwidefsky
2009-03-12 15:23 ` Matt Mackall
2009-03-12 15:27 ` Martin Schwidefsky
2009-03-12 15:41 ` Brice Goglin
2009-03-12 15:46 ` Martin Schwidefsky
2009-03-12 15:54 ` Martin Schwidefsky [this message]
2009-03-17 12:04 ` Martin Schwidefsky
2009-03-17 16:21 ` Matt Mackall
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