Move vm_fault busy logic into its own function for clarity and re-use by

later changes.

Reviewed by:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D22820

1 files changed, 36 insertions, 35 deletions

diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index 80c7bd4fd2f1..fb86b2591a41 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -684,6 +684,41 @@ vm_fault_lock_vnode(struct faultstate *fs)
 	return (KERN_RESOURCE_SHORTAGE);
 }
 
+/*
+ * Wait/Retry if the page is busy.  We have to do this if the page is
+ * either exclusive or shared busy because the vm_pager may be using
+ * read busy for pageouts (and even pageins if it is the vnode pager),
+ * and we could end up trying to pagein and pageout the same page
+ * simultaneously.
+ *
+ * We can theoretically allow the busy case on a read fault if the page
+ * is marked valid, but since such pages are typically already pmap'd,
+ * putting that special case in might be more effort then it is worth.
+ * We cannot under any circumstances mess around with a shared busied
+ * page except, perhaps, to pmap it.
+ */
+static void
+vm_fault_busy_sleep(struct faultstate *fs)
+{
+	/*
+	 * Reference the page before unlocking and
+	 * sleeping so that the page daemon is less
+	 * likely to reclaim it.
+	 */
+	vm_page_aflag_set(fs->m, PGA_REFERENCED);
+	if (fs->object != fs->first_object) {
+		fault_page_release(&fs->first_m);
+		vm_object_pip_wakeup(fs->first_object);
+	}
+	vm_object_pip_wakeup(fs->object);
+	unlock_map(fs);
+	if (fs->m == vm_page_lookup(fs->object, fs->pindex))
+		vm_page_sleep_if_busy(fs->m, "vmpfw");
+	VM_OBJECT_WUNLOCK(fs->object);
+	VM_CNT_INC(v_intrans);
+	vm_object_deallocate(fs->first_object);
+}
+
 int
 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
     int fault_flags, vm_page_t *m_hold)
@@ -822,42 +857,8 @@ RetryFault_oom:
 		 */
 		fs.m = vm_page_lookup(fs.object, fs.pindex);
 		if (fs.m != NULL) {
-			/*
-			 * Wait/Retry if the page is busy.  We have to do this
-			 * if the page is either exclusive or shared busy
-			 * because the vm_pager may be using read busy for
-			 * pageouts (and even pageins if it is the vnode
-			 * pager), and we could end up trying to pagein and
-			 * pageout the same page simultaneously.
-			 *
-			 * We can theoretically allow the busy case on a read
-			 * fault if the page is marked valid, but since such
-			 * pages are typically already pmap'd, putting that
-			 * special case in might be more effort then it is 
-			 * worth.  We cannot under any circumstances mess
-			 * around with a shared busied page except, perhaps,
-			 * to pmap it.
-			 */
 			if (vm_page_tryxbusy(fs.m) == 0) {
-				/*
-				 * Reference the page before unlocking and
-				 * sleeping so that the page daemon is less
-				 * likely to reclaim it.
-				 */
-				vm_page_aflag_set(fs.m, PGA_REFERENCED);
-				if (fs.object != fs.first_object) {
-					fault_page_release(&fs.first_m);
-					vm_object_pip_wakeup(fs.first_object);
-				}
-				unlock_map(&fs);
-				vm_object_pip_wakeup(fs.object);
-				if (fs.m == vm_page_lookup(fs.object,
-				    fs.pindex)) {
-					vm_page_sleep_if_busy(fs.m, "vmpfw");
-				}
-				VM_OBJECT_WUNLOCK(fs.object);
-				VM_CNT_INC(v_intrans);
-				vm_object_deallocate(fs.first_object);
+				vm_fault_busy_sleep(&fs);
 				goto RetryFault;
 			}