Messages in this thread | | | Date | Mon, 27 Jul 2015 16:26:03 -0700 | Subject | Re: [PATCH v2 08/25] arch: introduce memremap() | From | Dan Williams <> |
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On Sun, Jul 26, 2015 at 10:12 PM, Christoph Hellwig <hch@lst.de> wrote: > On Sun, Jul 26, 2015 at 10:49:39AM -0700, Dan Williams wrote: >> On Sun, Jul 26, 2015 at 10:25 AM, Christoph Hellwig <hch@lst.de> wrote: >> > On Fri, Jul 24, 2015 at 10:38:42PM -0400, Dan Williams wrote: >> >> The behavior change to return NULL on an unsupported request is reserved >> >> for a later patch. >> > >> > Why? >> >> This is for drivers like pmem that care about the mapping type. For >> example, if pmem can't get a cache-enabled mapping it is potentially >> putting the write durability of the persistent media at risk. > > I understand that part, but the question is why the old behavior > is retained for now and only changed later.
Oh, because all we have at this point is ioremap_cache() which silently falls back. It's not until the introduction of arch_memremp() where we update the arch code to break that behavior.
That said, I think it may be beneficial to allow a fallback if the user cares. So maybe memremap() can call plain ioremap() if MEMREMAP_STRICT is not set and none of the other mapping types are satisfied.
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