linux-kernel - Re: [PATCH 06/25] mm: factor out a devm_request_free_mem

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Message-ID: <20190617174251.GA18249@lst.de>
Date:   Mon, 17 Jun 2019 19:42:51 +0200
From:   Christoph Hellwig <hch@....de>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Christoph Hellwig <hch@....de>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Ben Skeggs <bskeggs@...hat.com>, Linux MM <linux-mm@...ck.org>,
        nouveau@...ts.freedesktop.org,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        linux-pci@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH 06/25] mm: factor out a devm_request_free_mem_region
 helper

On Mon, Jun 17, 2019 at 07:40:18PM +0200, Christoph Hellwig wrote:
> On Mon, Jun 17, 2019 at 10:37:12AM -0700, Dan Williams wrote:
> > > +struct resource *devm_request_free_mem_region(struct device *dev,
> > > +               struct resource *base, unsigned long size);
> > 
> > This appears to need a 'static inline' helper stub in the
> > CONFIG_DEVICE_PRIVATE=n case, otherwise this compile error triggers:
> > 
> > ld: mm/hmm.o: in function `hmm_devmem_add':
> > /home/dwillia2/git/linux/mm/hmm.c:1427: undefined reference to
> > `devm_request_free_mem_region'
> 
> *sigh* - hmm_devmem_add already only works for device private memory,
> so it shouldn't be built if that option is not enabled, but in the
> current code it is.  And a few patches later in the series we just
> kill it off entirely, and the only real caller of this function
> already depends on CONFIG_DEVICE_PRIVATE.  So I'm tempted to just
> ignore the strict bisectability requirement here instead of making
> things messy by either adding the proper ifdefs in hmm.c or providing
> a stub we don't really need.

Actually, I could just move the patch to mark CONFIG_DEVICE_PUBLIC
broken earlier, which would force hmm_devmem_add to only be built
when CONFIG_DEVICE_PRIVATE ist set.