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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sat, 16 Feb 2013 11:51:03 -0800
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Subject: Re: [-rc7 regression] Buggy commit: "mm: use aligned zone start for
 pfn_to_bitidx calculation"
To: Yinghai Lu <yinghai@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>, Greg KH <gregkh@suse.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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        "Theodore Ts'o" <tytso@mit.edu>, "H. Peter Anvin" <hpa@zytor.com>,
        Laura Abbott <lauraa@codeaurora.org>, Mel Gorman <mgorman@suse.de>
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On Sat, Feb 16, 2013 at 11:38 AM, Yinghai Lu <yinghai@kernel.org> wrote:
>
> but you forgot to update setup_usemap() for SPARSEMEM

Heh. I tried desperately to find a config to test my patch in, because
I couldn't see how to even disable SPARSEMEM for my normal x86-64
build. But then I *only* tested it for that non-SPARSEMEM case,
expecting that to be what showed any problems. The fact that I didn't
bother testing my normal config is a bit ironic.

But I'd still like verification that it actually fixes Ingo's issue.
It *looks* like it should, and it would explain the potential for
memory corruption, but perhaps Ingo's odd lock-up is due to something
really subtle and unrelated to the actual allocation size.

                Linus