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From: Dan Williams <dan.j.williams@intel.com>
Date: Fri, 14 Sep 2018 10:40:52 -0700
Message-ID: <CAPcyv4gj1E75rZ7kUVfO--CDK_u=-Qci06qmu+cQhaH8V=szGA@mail.gmail.com>
Subject: Re: [PATCH v5 2/7] mm, devm_memremap_pages: Kill mapping "System RAM" support
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To: Christoph Hellwig <hch@lst.de>
Cc: Andrew Morton <akpm@linux-foundation.org>, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= <jglisse@redhat.com>, Logan Gunthorpe <logang@deltatee.com>, Alexander Duyck <alexander.h.duyck@intel.com>, Linux MM <linux-mm@kvack.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

On Fri, Sep 14, 2018 at 6:14 AM, Christoph Hellwig <hch@lst.de> wrote:
> On Wed, Sep 12, 2018 at 07:22:11PM -0700, Dan Williams wrote:
>> Given the fact that devm_memremap_pages() requires a percpu_ref that is
>> torn down by devm_memremap_pages_release() the current support for
>> mapping RAM is broken.
>
> I agree.  Do you remember why we even added it in the first place?

It was initially a copy over from memremap() that catches these
attempts and returns a direct-map pointer.