The page flag PGA_WRITEABLE is set and cleared exclusively by the pmap

layer, but it is read directly by the MI VM layer.  This change introduces
pmap_page_is_write_mapped() in order to completely encapsulate all direct
access to PGA_WRITEABLE in the pmap layer.

Aesthetics aside, I am making this change because amd64 will likely begin
using an alternative method to track write mappings, and having
pmap_page_is_write_mapped() in place allows me to make such a change
without further modification to the MI VM layer.

As an added bonus, tidy up some nearby comments concerning page flags.

Reviewed by:	kib
MFC after:	6 weeks

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/mips/include/pmap.h b/sys/mips/include/pmap.h
index 35d414a..fbe8dd3 100644
--- a/sys/mips/include/pmap.h
+++ b/sys/mips/include/pmap.h
@@ -151,6 +151,7 @@ extern vm_paddr_t dump_avail[PHYS_AVAIL_ENTRIES + 2];
 
 #define	pmap_page_get_memattr(m)	VM_MEMATTR_DEFAULT
 #define	pmap_page_is_mapped(m)	(!TAILQ_EMPTY(&(m)->md.pv_list))
+#define	pmap_page_is_write_mapped(m)	(((m)->aflags & PGA_WRITEABLE) != 0)
 #define	pmap_page_set_memattr(m, ma)	(void)0
 
 void pmap_bootstrap(void);