inotify: Avoid resetting the cookie

The IN_MOVED_FROM and _TO events only apply to names in a watched
directory, never to a watched directory itself.  So, the cookie value
there is always zero, and in particular we should not reset the
caller-provided cookie value, as it may be used later.

Add a regression test.

Reported by:	arrowd
MFC after:	1 week

sys/kern/vfs_inotify.c

@@ -723,7 +723,6 @@ vn_inotify(struct vnode *vp, struct vnode *dvp, struct componentname *cnp,
 				}
 				break;
 			case IN_MOVED_FROM:
-				cookie = 0;
 				selfevent = IN_MOVE_SELF;
 				break;
 			case _IN_ATTRIB_LINKCOUNT:
@@ -734,10 +733,8 @@ vn_inotify(struct vnode *vp, struct vnode *dvp, struct componentname *cnp,
 				break;
 			}
 
-			if ((selfevent & ~_IN_DIR_EVENTS) != 0) {
-				inotify_log(vp, NULL, 0, selfevent | isdir,
-				    cookie);
-			}
+			if ((selfevent & ~_IN_DIR_EVENTS) != 0)
+				inotify_log(vp, NULL, 0, selfevent | isdir, 0);
 		}
 
 		/*

tests/sys/kern/inotify_test.c

@@ -761,6 +761,36 @@ ATF_TC_BODY(inotify_event_move, tc)
 	close_inotify(ifd);
 }
 
+ATF_TC_WITHOUT_HEAD(inotify_event_move_dir);
+ATF_TC_BODY(inotify_event_move_dir, tc)
+{
+	char dir[PATH_MAX], subdir1[PATH_MAX], subdir2[PATH_MAX];
+	uint32_t cookie1, cookie2;
+	int error, ifd, wd1, wd2;
+
+	ifd = inotify(IN_NONBLOCK);
+
+	wd1 = watch_dir(ifd, IN_MOVE, dir);
+	snprintf(subdir1, sizeof(subdir1), "%s/subdir", dir);
+	error = mkdir(subdir1, 0755);
+	ATF_REQUIRE(error == 0);
+	wd2 = inotify_add_watch(ifd, subdir1, IN_MOVE);
+	ATF_REQUIRE(wd2 != -1);
+
+	snprintf(subdir2, sizeof(subdir2), "%s/newsubdir", dir);
+	error = rename(subdir1, subdir2);
+	ATF_REQUIRE(error == 0);
+
+	cookie1 = consume_event_cookie(ifd, wd1, IN_MOVED_FROM, IN_ISDIR,
+	    "subdir");
+	cookie2 = consume_event_cookie(ifd, wd1, IN_MOVED_TO, IN_ISDIR,
+	    "newsubdir");
+	ATF_REQUIRE_MSG(cookie1 == cookie2,
+	    "expected cookie %u, got %u", cookie1, cookie2);
+
+	close_inotify(ifd);
+}
+
 ATF_TC_WITHOUT_HEAD(inotify_event_open);
 ATF_TC_BODY(inotify_event_open, tc)
 {
@@ -858,6 +888,7 @@ ATF_TP_ADD_TCS(tp)
 	ATF_TP_ADD_TC(tp, inotify_event_create);
 	ATF_TP_ADD_TC(tp, inotify_event_delete);
 	ATF_TP_ADD_TC(tp, inotify_event_move);
+	ATF_TP_ADD_TC(tp, inotify_event_move_dir);
 	ATF_TP_ADD_TC(tp, inotify_event_open);
 	ATF_TP_ADD_TC(tp, inotify_event_unmount);
 	return (atf_no_error());