On Wed, 15 Jan 2014 14:57:56 -0800 (PST) David Rientjes [off-list ref] wrote:

On Wed, 15 Jan 2014, Geert Uytterhoeven wrote:

quoted

{,set}page_address() are macros if WANT_PAGE_VIRTUAL.
If !WANT_PAGE_VIRTUAL, they're plain C functions.

If someone calls them with a void *, this pointer is auto-converted to
struct page * if !WANT_PAGE_VIRTUAL, but causes a build failure on
architectures using WANT_PAGE_VIRTUAL (arc, m68k and sparc):

s/sparc/sparc64/

quoted

drivers/md/bcache/bset.c: In function _____btree_sort___:
drivers/md/bcache/bset.c:1190: warning: dereferencing ___void *___ pointer
drivers/md/bcache/bset.c:1190: error: request for member ___virtual___ in something not a structure or union

Convert them to static inline functions to fix this. There are already
plenty of  users of struct page members inside <linux/mm.h>, so there's no
reason to keep them as macros.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Tested-by: David Rientjes <rientjes@google.com>

I'm cringing at the page_address(mempool_alloc(..., GFP_NOIO)) in 
drivers/md/bcache/bset.c, though.

Yes, I was staring suspiciously at that as well.  Ended up deciding
that I wouldn't have coded it that way, but we should support the
casting.

 It's relying on that fact that 
mempool_alloc() can never return NULL if __GFP_WAIT but I think this could 
have all been avoided with

	struct page *page = mempool_alloc(state->pool, GFP_NOIO);
	out = page_address(page);

instead of burying the mempool_alloc() in page_address() for what I think 
is cleaner code.  Owell, it fixes the issue.

And that would make the later virt_to_page() unnecessary.

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