From 9cb574590ef8075477a64baa25976f6e68378b52 Mon Sep 17 00:00:00 2001
From: Brian Feldman <green@FreeBSD.org>
Date: Thu, 14 Mar 2002 02:10:14 +0000
Subject: [PATCH] Document faultstate.lookup_still_valid more than none.

Requested by:	alfred
---
 sys/vm/vm_fault.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index cf2ab8dd57b7..02a7f460c69e 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -111,7 +111,11 @@ struct faultstate {
 	vm_pindex_t first_pindex;
 	vm_map_t map;
 	vm_map_entry_t entry;
-	int lookup_still_valid;
+	enum {
+		LSV_FALSE,	/* the lookup's lock has been dropped */
+		LSV_TRUE,	/* the lookup's lock is still valid */
+		LSV_UPGRADED	/* the lookup's lock is now exclusive */
+	} lookup_still_valid;
 	struct vnode *vp;
 };
 
@@ -126,11 +130,11 @@ release_page(struct faultstate *fs)
 static __inline void
 unlock_map(struct faultstate *fs)
 {
-	if (fs->lookup_still_valid) {
-		if (fs->lookup_still_valid == 2)
+	if (fs->lookup_still_valid != LSV_FALSE) {
+		if (fs->lookup_still_valid == LSV_UPGRADED)
 			vm_map_lock_downgrade(fs->map);
 		vm_map_lookup_done(fs->map, fs->entry);
-		fs->lookup_still_valid = FALSE;
+		fs->lookup_still_valid = LSV_FALSE;
 	}
 }
 
@@ -284,7 +288,7 @@ RetryFault:;
 			fs.first_pindex, fs.first_pindex + 1);
 	}
 
-	fs.lookup_still_valid = 1;
+	fs.lookup_still_valid = LSV_TRUE;
 
 	if (wired)
 		fault_type = prot;
@@ -658,11 +662,11 @@ RetryFault:;
 				/*
 				 * grab the lock if we need to
 				 */
-				(fs.lookup_still_valid ||
+				(fs.lookup_still_valid != LSV_FALSE ||
 				 vm_map_try_lock(fs.map) == 0)
 			    ) {
-				if (fs.lookup_still_valid == 0)
-					fs.lookup_still_valid = 2;
+				if (fs.lookup_still_valid == LSV_FALSE)
+					fs.lookup_still_valid = LSV_UPGRADED;
 				/*
 				 * get rid of the unnecessary page
 				 */
@@ -717,7 +721,7 @@ RetryFault:;
 	 * We must verify that the maps have not changed since our last
 	 * lookup.
 	 */
-	if (!fs.lookup_still_valid &&
+	if (fs.lookup_still_valid == LSV_FALSE &&
 		(fs.map->timestamp != map_generation)) {
 		vm_object_t retry_object;
 		vm_pindex_t retry_pindex;
@@ -766,7 +770,7 @@ RetryFault:;
 			unlock_and_deallocate(&fs);
 			return (result);
 		}
-		fs.lookup_still_valid = 1;
+		fs.lookup_still_valid = LSV_TRUE;
 
 		if ((retry_object != fs.first_object) ||
 		    (retry_pindex != fs.first_pindex)) {