[PATCH] fuse: add asynchronous request support

Add possibility for requests to run asynchronously and call an 'end' callback
when finished.

With this, the special handling of the INIT and RELEASE requests can be
cleaned up too.

Signed-off-by: Miklos Szeredi <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/fuse/dev.c

···
 	   fuse_putback_request() */
 	for (i = 1; i < FUSE_MAX_OUTSTANDING; i++)
 		up(&fc->outstanding_sem);
+
+	fuse_put_request(fc, req);
 }
 
 /*
···
  * occurred during communication with userspace, or the device file
  * was closed.  In case of a background request the reference to the
  * stored objects are released.  The requester thread is woken up (if
- * still waiting), and finally the reference to the request is
- * released
+ * still waiting), the 'end' callback is called if given, else the
+ * reference to the request is released
  *
  * Called with fuse_lock, unlocks it
  */
 static void request_end(struct fuse_conn *fc, struct fuse_req *req)
 {
+	void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
+	req->end = NULL;
 	list_del(&req->list);
 	req->state = FUSE_REQ_FINISHED;
 	spin_unlock(&fuse_lock);
···
 		up_read(&fc->sbput_sem);
 	}
 	wake_up(&req->waitq);
-	if (req->in.h.opcode == FUSE_INIT)
-		process_init_reply(fc, req);
-	else if (req->in.h.opcode == FUSE_RELEASE && req->inode == NULL) {
-		/* Special case for failed iget in CREATE */
-		u64 nodeid = req->in.h.nodeid;
-		fuse_reset_request(req);
-		fuse_send_forget(fc, req, nodeid, 1);
-		return;
-	}
-	fuse_put_request(fc, req);
+	if (end)
+		end(fc, req);
+	else
+		fuse_put_request(fc, req);
 }
 
 /*
···
 	req->out.argvar = 1;
 	req->out.args[0].size = sizeof(struct fuse_init_out);
 	req->out.args[0].value = &req->misc.init_out;
+	req->end = process_init_reply;
 	request_send_background(fc, req);
 }
 
···
  * The requests are set to interrupted and finished, and the request
  * waiter is woken up.  This will make request_wait_answer() wait
  * until the request is unlocked and then return.
+ *
+ * If the request is asynchronous, then the end function needs to be
+ * called after waiting for the request to be unlocked (if it was
+ * locked).
  */
 static void end_io_requests(struct fuse_conn *fc)
 {
 	while (!list_empty(&fc->io)) {
-		struct fuse_req *req;
-		req = list_entry(fc->io.next, struct fuse_req, list);
+		struct fuse_req *req =
+			list_entry(fc->io.next, struct fuse_req, list);
+		void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
+
 		req->interrupted = 1;
 		req->out.h.error = -ECONNABORTED;
 		req->state = FUSE_REQ_FINISHED;
 		list_del_init(&req->list);
 		wake_up(&req->waitq);
+		if (end) {
+			req->end = NULL;
+			/* The end function will consume this reference */
+			__fuse_get_request(req);
+			spin_unlock(&fuse_lock);
+			wait_event(req->waitq, !req->locked);
+			end(fc, req);
+			spin_lock(&fuse_lock);
+		}
 	}
 }
 

fs/fuse/file.c

···
 	return err;
 }
 
+/* Special case for failed iget in CREATE */
+static void fuse_release_end(struct fuse_conn *fc, struct fuse_req *req)
+{
+	u64 nodeid = req->in.h.nodeid;
+	fuse_reset_request(req);
+	fuse_send_forget(fc, req, nodeid, 1);
+}
+
 void fuse_send_release(struct fuse_conn *fc, struct fuse_file *ff,
 		       u64 nodeid, struct inode *inode, int flags, int isdir)
 {
···
 	req->in.args[0].size = sizeof(struct fuse_release_in);
 	req->in.args[0].value = inarg;
 	request_send_background(fc, req);
+	if (!inode)
+		req->end = fuse_release_end;
 	kfree(ff);
 }
 

fs/fuse/fuse_i.h

···
 	FUSE_REQ_FINISHED
 };
 
+struct fuse_conn;
+
 /**
  * A request to the client
  */
···
 
 	/** File used in the request (or NULL) */
 	struct file *file;
+
+	/** Request completion callback */
+	void (*end)(struct fuse_conn *, struct fuse_req *);
 };
 
 /**