bozo: Require BNODE_LOCK for DirAccessOK

DirAccessOK() currently uses two static vars (lastTime, lastResult) to
cache the result of the function to avoid overly-frequent stat()s. These
are not documented as being protected by any locks. Currently they
cannot be accessed by two different threads at the same time; the only
callers are:

- SBOZO_GetInstanceInfo(), which calls it with BNODE_LOCK held
- main(), which calls it before our rx service threads are started

But this is fragile and not documented. To avoid potential issues in the
future, document DirAccessOK() as requiring BNODE_LOCK, assert that we
have BNODE_LOCK in DirAccessOK(), and acquire BNODE_LOCK before calling
DirAccessOK() from main().

While we're here, move the declarations for the two static vars so
they're next to each other, so it's a little more obvious that we have
some static variables here.

Change-Id: I4e0e55cd8a7ebbb681e4da937efcc9c37633e3ab
Reviewed-on: https://gerrit.openafs.org/15837
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>

src/bozo/bosoprocs.c

@@ -1360,10 +1360,13 @@ StatEachEntry(IN struct bozo_bosEntryStats *stats)
     return 1;
 }
 
-/* DirAccessOK - checks the mode bits on the AFS dir and decendents and
+/*
+ * DirAccessOK - checks the mode bits on the AFS dir and decendents and
  * returns 0 if some are not OK and 1 otherwise.  For efficiency, it doesn't do
- * this check more often than every 5 seconds. */
-
+ * this check more often than every 5 seconds.
+ *
+ * @pre BNODE_LOCK must be held
+ */
 int
 DirAccessOK(void)
 {
@@ -1372,11 +1375,13 @@ DirAccessOK(void)
     return 1;
 #else
     static afs_uint32 lastTime = 0;
-    afs_uint32 now = FT_ApproxTime();
     static int lastResult = -1;
+    afs_uint32 now = FT_ApproxTime();
     int result;
     int i;
 
+    BNODE_ASSERT_LOCK();
+
     if ((now - lastTime) < 5)
 	return lastResult;
     lastTime = now;

src/bozo/bosserver.c

@@ -1174,6 +1174,8 @@ main(int argc, char **argv, char **envp)
     signal(SIGFPE, bozo_insecureme);
 #endif
 
+    BNODE_LOCK();
+
     /* Write current state of directory permissions to log file */
     DirAccessOK();
 
@@ -1203,8 +1205,6 @@ main(int argc, char **argv, char **envp)
     /* opened the cell databse */
     bozo_confdir = tdir;
 
-    BNODE_LOCK();
-
     code = bnode_Init();
     if (code) {
 	printf("bosserver: could not init bnode package, code %d\n", code);