fuse: use atomic64_t for khctr

...to get rid of one more fc->lock use.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/file.c

@@ -64,9 +64,7 @@ struct fuse_file *fuse_file_alloc(struct fuse_conn *fc)
 	RB_CLEAR_NODE(&ff->polled_node);
 	init_waitqueue_head(&ff->poll_wait);
 
-	spin_lock(&fc->lock);
-	ff->kh = ++fc->khctr;
-	spin_unlock(&fc->lock);
+	ff->kh = atomic64_inc_return(&fc->khctr);
 
 	return ff;
 }

fs/fuse/fuse_i.h

@@ -544,7 +544,7 @@ struct fuse_conn {
 	struct fuse_iqueue iq;
 
 	/** The next unique kernel file handle */
-	u64 khctr;
+	atomic64_t khctr;
 
 	/** rbtree of fuse_files waiting for poll events indexed by ph */
 	struct rb_root polled_files;

fs/fuse/inode.c

@@ -622,7 +622,7 @@ void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns)
 	atomic_set(&fc->num_waiting, 0);
 	fc->max_background = FUSE_DEFAULT_MAX_BACKGROUND;
 	fc->congestion_threshold = FUSE_DEFAULT_CONGESTION_THRESHOLD;
-	fc->khctr = 0;
+	atomic64_set(&fc->khctr, 0);
 	fc->polled_files = RB_ROOT;
 	fc->blocked = 0;
 	fc->initialized = 0;