fuse: new work queue to invalidate dentries from old epochs

With the infrastructure introduced to periodically invalidate expired
dentries, it is now possible to add an extra work queue to invalidate
dentries when an epoch is incremented. This work queue will only be
triggered when the 'inval_wq' parameter is set.

Signed-off-by: Luis Henriques <[e-mail]>
Signed-off-by: Miklos Szeredi <[e-mail]>

fs/fuse/dev.c

···
 
 /*
  * Increments the fuse connection epoch.  This will result of dentries from
- * previous epochs to be invalidated.
- *
- * XXX optimization: add call to shrink_dcache_sb()?
+ * previous epochs to be invalidated.  Additionally, if inval_wq is set, a work
+ * queue is scheduled to trigger the invalidation.
  */
 static int fuse_notify_inc_epoch(struct fuse_conn *fc)
 {
 	atomic_inc(&fc->epoch);
+	if (inval_wq)
+		schedule_work(&fc->epoch_work);
 
 	return 0;
 }

fs/fuse/dir.c

···
 				      secs_to_jiffies(inval_wq));
 }
 
+void fuse_epoch_work(struct work_struct *work)
+{
+	struct fuse_conn *fc = container_of(work, struct fuse_conn,
+					    epoch_work);
+	struct fuse_mount *fm;
+	struct inode *inode;
+
+	down_read(&fc->killsb);
+
+	inode = fuse_ilookup(fc, FUSE_ROOT_ID, &fm);
+	iput(inode);
+
+	if (fm) {
+		/* Remove all possible active references to cached inodes */
+		shrink_dcache_sb(fm->sb);
+	} else
+		pr_warn("Failed to get root inode");
+
+	up_read(&fc->killsb);
+}
+
 void fuse_dentry_tree_init(void)
 {
 	int i;

fs/fuse/fuse_i.h

···
 	/** Current epoch for up-to-date dentries */
 	atomic_t epoch;
 
+	struct work_struct epoch_work;
+
 	struct rcu_head rcu;
 
 	/** The user id for this mount */
···
 
 void fuse_dentry_tree_init(void);
 void fuse_dentry_tree_cleanup(void);
+
+void fuse_epoch_work(struct work_struct *work);
 
 /**
  * Invalidate inode attributes

fs/fuse/inode.c

···
 	refcount_set(&fc->count, 1);
 	atomic_set(&fc->dev_count, 1);
 	atomic_set(&fc->epoch, 1);
+	INIT_WORK(&fc->epoch_work, fuse_epoch_work);
 	init_waitqueue_head(&fc->blocked_waitq);
 	fuse_iqueue_init(&fc->iq, fiq_ops, fiq_priv);
 	INIT_LIST_HEAD(&fc->bg_queue);
···
 			fuse_dax_conn_free(fc);
 		if (fc->timeout.req_timeout)
 			cancel_delayed_work_sync(&fc->timeout.work);
+		cancel_work_sync(&fc->epoch_work);
 		if (fiq->ops->release)
 			fiq->ops->release(fiq);
 		put_pid_ns(fc->pid_ns);