Subject: Re: dio_get_page() lockdep complaints
From: Peter Zijlstra <peterz@infradead.org>
To: schwidefsky@de.ibm.com
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>,
       Zach Brown <zach.brown@oracle.com>, Jens Axboe <jens.axboe@oracle.com>,
       linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
       linux-aio@kvack.org, Chris Mason <chris.mason@oracle.com>,
       linux-mm <linux-mm@kvack.org>, Hugh Dickins <hugh@veritas.com>,
       Linus Torvalds <torvalds@linux-foundation.org>
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Date: Mon, 12 Nov 2007 10:27:22 +0100
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On Mon, 2007-11-12 at 09:45 +0100, Martin Schwidefsky wrote:
> On Sun, 2007-11-11 at 20:49 +0100, Peter Zijlstra wrote:
> > Right, which gets us into all kinds of trouble because some sites need
> > mmap_sem to resolve some races, notably s390 31-bit and shm.
> 
> You are refering to the mmap_sem use in compat_linux.c:do_mmap2, aren't
> you? That check for adresses > 2GB after the call to do_mmap_pgoff can
> be removed since arch_get_unmapped_area already checks against
> TASK_SIZE. The result of the do_mmap_pgoff call will never be out of
> range. This check is a left-over from the early days of the s390 compat
> code.

Correct, that is the one I was referring to. Thanks for the explanation,
I'll clean it up when I take this patch forward.


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