[Midnightbsd-cvs] src [8091] trunk/sys: page flag PGA_WRITEABLE is set and cleared exclusively by the pmap layer, but it is read directly by the MI VM layer.

laffer1 at midnightbsd.org laffer1 at midnightbsd.org
Thu Sep 15 18:47:28 EDT 2016 

Revision: 8091
          http://svnweb.midnightbsd.org/src/?rev=8091
Author:   laffer1
Date:     2016-09-15 18:47:28 -0400 (Thu, 15 Sep 2016)
Log Message:
-----------
page flag PGA_WRITEABLE is set and cleared exclusively by the pmap layer, but it is read directly by the MI VM layer.

Modified Paths:
--------------
    trunk/sys/amd64/include/pmap.h
    trunk/sys/i386/include/pmap.h
    trunk/sys/vm/pmap.h
    trunk/sys/vm/swap_pager.c
    trunk/sys/vm/vm_page.c
    trunk/sys/vm/vm_page.h
    trunk/sys/vm/vm_pageout.c
    trunk/sys/vm/vnode_pager.c

Modified: trunk/sys/amd64/include/pmap.h
===================================================================
--- trunk/sys/amd64/include/pmap.h	2016-09-15 22:45:54 UTC (rev 8090)
+++ trunk/sys/amd64/include/pmap.h	2016-09-15 22:47:28 UTC (rev 8091)
@@ -309,6 +309,7 @@
 extern vm_offset_t virtual_end;
 
 #define	pmap_page_get_memattr(m)	((vm_memattr_t)(m)->md.pat_mode)
+#define	pmap_page_is_write_mapped(m)	(((m)->aflags & PGA_WRITEABLE) != 0)
 #define	pmap_unmapbios(va, sz)	pmap_unmapdev((va), (sz))
 
 void	pmap_bootstrap(vm_paddr_t *);

Modified: trunk/sys/i386/include/pmap.h
===================================================================
--- trunk/sys/i386/include/pmap.h	2016-09-15 22:45:54 UTC (rev 8090)
+++ trunk/sys/i386/include/pmap.h	2016-09-15 22:47:28 UTC (rev 8091)
@@ -498,6 +498,7 @@
 extern vm_offset_t virtual_end;
 
 #define	pmap_page_get_memattr(m)	((vm_memattr_t)(m)->md.pat_mode)
+#define	pmap_page_is_write_mapped(m)	(((m)->aflags & PGA_WRITEABLE) != 0)
 #define	pmap_unmapbios(va, sz)	pmap_unmapdev((va), (sz))
 
 /*

Modified: trunk/sys/vm/pmap.h
===================================================================
--- trunk/sys/vm/pmap.h	2016-09-15 22:45:54 UTC (rev 8090)
+++ trunk/sys/vm/pmap.h	2016-09-15 22:47:28 UTC (rev 8091)
@@ -80,10 +80,11 @@
 typedef struct pmap_statistics *pmap_statistics_t;
 
 /*
- * Each machine dependent implementation is expected to provide:
+ * Each machine-dependent implementation is required to provide:
  *
  * vm_memattr_t	pmap_page_get_memattr(vm_page_t);
  * boolean_t	pmap_page_is_mapped(vm_page_t);
+ * boolean_t	pmap_page_is_write_mapped(vm_page_t);
  * void		pmap_page_set_memattr(vm_page_t, vm_memattr_t);
  */
 #include <machine/pmap.h>

Modified: trunk/sys/vm/swap_pager.c
===================================================================
--- trunk/sys/vm/swap_pager.c	2016-09-15 22:45:54 UTC (rev 8090)
+++ trunk/sys/vm/swap_pager.c	2016-09-15 22:47:28 UTC (rev 8091)
@@ -1593,7 +1593,7 @@
 			 * status, then finish the I/O ( which decrements the 
 			 * busy count and possibly wakes waiter's up ).
 			 */
-			KASSERT((m->aflags & PGA_WRITEABLE) == 0,
+			KASSERT(!pmap_page_is_write_mapped(m),
 			    ("swp_pager_async_iodone: page %p is not write"
 			    " protected", m));
 			vm_page_undirty(m);

Modified: trunk/sys/vm/vm_page.c
===================================================================
--- trunk/sys/vm/vm_page.c	2016-09-15 22:45:54 UTC (rev 8090)
+++ trunk/sys/vm/vm_page.c	2016-09-15 22:47:28 UTC (rev 8091)
@@ -965,7 +965,7 @@
 	 * Since we are inserting a new and possibly dirty page,
 	 * update the object's OBJ_MIGHTBEDIRTY flag.
 	 */
-	if (m->aflags & PGA_WRITEABLE)
+	if (pmap_page_is_write_mapped(m))
 		vm_object_set_writeable_dirty(object);
 }
 
@@ -2504,11 +2504,11 @@
 
 	/*
 	 * If the object is locked and the page is neither VPO_BUSY nor
-	 * PGA_WRITEABLE, then the page's dirty field cannot possibly be
+	 * write mapped, then the page's dirty field cannot possibly be
 	 * set by a concurrent pmap operation.
 	 */
 	VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
-	if ((m->oflags & VPO_BUSY) == 0 && (m->aflags & PGA_WRITEABLE) == 0)
+	if ((m->oflags & VPO_BUSY) == 0 && !pmap_page_is_write_mapped(m))
 		m->dirty &= ~pagebits;
 	else {
 		/*

Modified: trunk/sys/vm/vm_page.h
===================================================================
--- trunk/sys/vm/vm_page.h	2016-09-15 22:45:54 UTC (rev 8090)
+++ trunk/sys/vm/vm_page.h	2016-09-15 22:47:28 UTC (rev 8091)
@@ -237,20 +237,22 @@
 #endif
 
 #define	vm_page_queue_free_mtx	vm_page_queue_free_lock.data
+
 /*
  * These are the flags defined for vm_page.
  *
- * aflags are updated by atomic accesses. Use the vm_page_aflag_set()
+ * aflags are updated by atomic accesses.  Use the vm_page_aflag_set()
  * and vm_page_aflag_clear() functions to set and clear the flags.
  *
  * PGA_REFERENCED may be cleared only if the object containing the page is
- * locked.
+ * locked.  It is set by both the MI and MD VM layers.
  *
  * PGA_WRITEABLE is set exclusively on managed pages by pmap_enter().  When it
- * does so, the page must be VPO_BUSY.
+ * does so, the page must be VPO_BUSY.  The MI VM layer must never access this
+ * flag directly.  Instead, it should call pmap_page_is_write_mapped().
  *
  * PGA_EXECUTABLE may be set by pmap routines, and indicates that a page has
- * at least one executable mapping. It is not consumed by the VM layer.
+ * at least one executable mapping.  It is not consumed by the MI VM layer.
  */
 #define	PGA_WRITEABLE	0x01		/* page may be mapped writeable */
 #define	PGA_REFERENCED	0x02		/* page has been referenced */
@@ -262,12 +264,12 @@
  */
 #define	PG_CACHED	0x01		/* page is cached */
 #define	PG_FREE		0x02		/* page is free */
-#define	PG_FICTITIOUS	0x04		/* physical page doesn't exist (O) */
+#define	PG_FICTITIOUS	0x04		/* physical page doesn't exist */
 #define	PG_ZERO		0x08		/* page is zeroed */
 #define	PG_MARKER	0x10		/* special queue marker page */
 #define	PG_SLAB		0x20		/* object pointer is actually a slab */
 #define	PG_WINATCFLS	0x40		/* flush dirty page on inactive q */
-#define	PG_NODUMP	0x80		/* don't include this page in the dump */
+#define	PG_NODUMP	0x80		/* don't include this page in a dump */
 
 /*
  * Misc constants.

Modified: trunk/sys/vm/vm_pageout.c
===================================================================
--- trunk/sys/vm/vm_pageout.c	2016-09-15 22:45:54 UTC (rev 8090)
+++ trunk/sys/vm/vm_pageout.c	2016-09-15 22:47:28 UTC (rev 8091)
@@ -503,7 +503,7 @@
 		vm_page_t mt = mc[i];
 
 		KASSERT(pageout_status[i] == VM_PAGER_PEND ||
-		    (mt->aflags & PGA_WRITEABLE) == 0,
+		    !pmap_page_is_write_mapped(mt),
 		    ("vm_pageout_flush: page %p is not write protected", mt));
 		switch (pageout_status[i]) {
 		case VM_PAGER_OK:
@@ -922,7 +922,7 @@
 		 * be updated.
 		 */
 		if (m->dirty != VM_PAGE_BITS_ALL &&
-		    (m->aflags & PGA_WRITEABLE) != 0) {
+		    pmap_page_is_write_mapped(m)) {
 			/*
 			 * Avoid a race condition: Unless write access is
 			 * removed from the page, another processor could

Modified: trunk/sys/vm/vnode_pager.c
===================================================================
--- trunk/sys/vm/vnode_pager.c	2016-09-15 22:45:54 UTC (rev 8090)
+++ trunk/sys/vm/vnode_pager.c	2016-09-15 22:47:28 UTC (rev 8091)
@@ -1116,7 +1116,7 @@
 				m = ma[ncount - 1];
 				KASSERT(m->busy > 0,
 		("vnode_pager_generic_putpages: page %p is not busy", m));
-				KASSERT((m->aflags & PGA_WRITEABLE) == 0,
+				KASSERT(!pmap_page_is_write_mapped(m),
 		("vnode_pager_generic_putpages: page %p is not read-only", m));
 				vm_page_clear_dirty(m, pgoff, PAGE_SIZE -
 				    pgoff);

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