FS-Cache: Make cookie relinquishment wait for outstanding reads

Make fscache_relinquish_cookie() log a warning and wait if there are any
outstanding reads left on the cookie it was given.

Signed-off-by: David Howells <dhowells@redhat.com>

include/linux/fscache-cache.h

@@ -301,6 +301,7 @@ struct fscache_cookie {
 #define FSCACHE_COOKIE_PENDING_FILL	3	/* T if pending initial fill on object */
 #define FSCACHE_COOKIE_FILLING		4	/* T if filling object incrementally */
 #define FSCACHE_COOKIE_UNAVAILABLE	5	/* T if cookie is unavailable (error, etc) */
+#define FSCACHE_COOKIE_WAITING_ON_READS	6	/* T if cookie is waiting on reads */
 };
 
 extern struct fscache_cookie fscache_fsdef_index;