Re: [PATCH v3 5/6] arch: introduce memremap_cache() and memremap_wt()

From: Dan Williams <dan.j.williams@intel.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ross Zwisler <ross.zwisler@linux.intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Juergen Gross <jgross@suse.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"Kani, Toshimitsu" <toshi.kani@hp.com>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Luis Rodriguez <mcgrof@suse.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Stefan Bader <stefan.bader@canonical.com>,
	Andy Lutomirski <luto@amacapital.net>,
	linux-mm@kvack.org, Geert Uytterhoeven <geert@linux-m68k.org>,
	Ralf Baechle <ralf@linux-mips.org>,
	Henrique de Moraes Holschuh <hmh@hmh.eng.br>,
	mpe@ellerman.id.au, Tejun Heo <tj@kernel.org>,
	Paul Mackerras <paulus@samba.org>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v3 5/6] arch: introduce memremap_cache() and memremap_wt()
Date: Mon, 8 Jun 2015 12:39:33 -0700	[thread overview]
Message-ID: <CAPcyv4hi9tEdRborvfV19MhRPM-pch=mCaLD0To1N_sZejJZ2g@mail.gmail.com> (raw)
In-Reply-To: <CAHp75VdW5Pd-h1qvOm+sTT6xoAbYRY9aBR8aTMF7QQ8sT05FZw@mail.gmail.com>

On Mon, Jun 8, 2015 at 12:04 PM, Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> On Mon, Jun 8, 2015 at 9:25 PM, Dan Williams <dan.j.williams@intel.com> wrote:
>
>>>> +       if (region_is_ram(offset, size) != 0) {
>>>> +               WARN_ONCE(1, "memremap attempted on ram %pa size: %zd\n",
>>>
>>> %zu
>>
>> Sure, thanks for taking a look Andy!
>
> One more thing, can we do
> WARN_ONCE(region_is_ram(offset, size), …); ?
>

We still want to return false in this case so it would become
"if(WARN_ONCE(...)) return false;".  Neil once made the argument to me
that we should be able to compile all of the asserts out of the
kernel, also "if (WARN_ONCE(...))" is a bit harder to read as you need
to go check the macro to make sure it returns the right status, and
more than once.

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