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Date:   Tue, 18 Jun 2019 23:02:51 +0300
From:   Vladimir Davydov <vdavydov.dev@gmail.com>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Colin King <colin.king@canonical.com>,
        Michal Hocko <mhocko@suse.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>, linux-mm@kvack.org,
        kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: idle-page: fix oops because end_pfn is larger than
 max_pfn
Message-ID: <20190618200251.hd2uk6qzyvsy55py@esperanza>
References: <20190618124352.28307-1-colin.king@canonical.com>
 <20190618124502.7b9c32a00a54f0c618a12ca4@linux-foundation.org>
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On Tue, Jun 18, 2019 at 12:45:02PM -0700, Andrew Morton wrote:
> On Tue, 18 Jun 2019 13:43:52 +0100 Colin King <colin.king@canonical.com> wrote:
> 
> > From: Colin Ian King <colin.king@canonical.com>
> > 
> > Currently the calcuation of end_pfn can round up the pfn number to
> > more than the actual maximum number of pfns, causing an Oops. Fix
> > this by ensuring end_pfn is never more than max_pfn.
> > 
> > This can be easily triggered when on systems where the end_pfn gets
> > rounded up to more than max_pfn using the idle-page stress-ng
> > stress test:
> > 
> 
> cc Vladimir.  This seems rather obvious - I'm wondering if the code was
> that way for some subtle reason?

No subtle reason at all - just a bug. The patch looks good to me,

Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>