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Date: Fri, 28 Sep 2012 11:31:41 -0400
From: Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH] thp: avoid VM_BUG_ON page_count(page) false positives in
 __collapse_huge_page_copy
Message-ID: <20120928153141.GA23734@cmpxchg.org>
References: <1348835731-27474-1-git-send-email-aarcange@redhat.com>
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To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, Rik van Riel <riel@redhat.com>, Johannes Weiner <jweiner@redhat.com>, Hugh Dickins <hughd@google.com>, Mel Gorman <mgorman@suse.de>, Petr Holasek <pholasek@redhat.com>

On Fri, Sep 28, 2012 at 02:35:31PM +0200, Andrea Arcangeli wrote:
> Speculative cache pagecache lookups can elevate the refcount from
> under us, so avoid the false positive. If the refcount is < 2 we'll be
> notified by a VM_BUG_ON in put_page_testzero as there are two
> put_page(src_page) in a row before returning from this function.
> 
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>

Much better, thank you.

Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>

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