(6/6) Convert pmap to expect busy in write related operations now that all

callers hold it.

This simplifies pmap code and removes a dependency on the object lock.

Reviewed by:    kib, markj
Tested by:      pho
Sponsored by:   Netflix, Intel
Differential Revision:	https://reviews.freebsd.org/D21596

1 files changed, 9 insertions, 22 deletions

diff --git a/sys/sparc64/sparc64/pmap.c b/sys/sparc64/sparc64/pmap.c
index d485344230a3..5a2511779140 100644
--- a/sys/sparc64/sparc64/pmap.c
+++ b/sys/sparc64/sparc64/pmap.c
@@ -2116,12 +2116,9 @@ pmap_is_modified(vm_page_t m)
 	rv = FALSE;
 
 	/*
-	 * If the page is not exclusive busied, then PGA_WRITEABLE cannot be
-	 * concurrently set while the object is locked.  Thus, if PGA_WRITEABLE
-	 * is clear, no TTEs can have TD_W set.
+	 * If the page is not busied then this check is racy.
 	 */
-	VM_OBJECT_ASSERT_WLOCKED(m->object);
-	if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
+	if (!pmap_page_is_write_mapped(m))
 		return (rv);
 	rw_wlock(&tte_list_global_lock);
 	TAILQ_FOREACH(tp, &m->md.tte_list, tte_link) {
@@ -2195,17 +2192,11 @@ pmap_clear_modify(vm_page_t m)
 
 	KASSERT((m->oflags & VPO_UNMANAGED) == 0,
 	    ("pmap_clear_modify: page %p is not managed", m));
-	VM_OBJECT_ASSERT_WLOCKED(m->object);
-	KASSERT(!vm_page_xbusied(m),
-	    ("pmap_clear_modify: page %p is exclusive busied", m));
+	vm_page_assert_busied(m);
 
-	/*
-	 * If the page is not PGA_WRITEABLE, then no TTEs can have TD_W set.
-	 * If the object containing the page is locked and the page is not
-	 * exclusive busied, then PGA_WRITEABLE cannot be concurrently set.
-	 */
-	if ((m->aflags & PGA_WRITEABLE) == 0)
+	if (!pmap_page_is_write_mapped(m))
 		return;
+
 	rw_wlock(&tte_list_global_lock);
 	TAILQ_FOREACH(tp, &m->md.tte_list, tte_link) {
 		if ((tp->tte_data & TD_PV) == 0)
@@ -2225,15 +2216,11 @@ pmap_remove_write(vm_page_t m)
 
 	KASSERT((m->oflags & VPO_UNMANAGED) == 0,
 	    ("pmap_remove_write: page %p is not managed", m));
+	vm_page_assert_busied(m);
+
+	if (!pmap_page_is_write_mapped(m))
+	        return;
 
-	/*
-	 * If the page is not exclusive busied, then PGA_WRITEABLE cannot be
-	 * set by another thread while the object is locked.  Thus,
-	 * if PGA_WRITEABLE is clear, no page table entries need updating.
-	 */
-	VM_OBJECT_ASSERT_WLOCKED(m->object);
-	if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
-		return;
 	rw_wlock(&tte_list_global_lock);
 	TAILQ_FOREACH(tp, &m->md.tte_list, tte_link) {
 		if ((tp->tte_data & TD_PV) == 0)