fuse: add fuse_iqueue_ops callbacks

task #28910367
commit ae3aad77f46fbba56eff7141b2fc49870b60827e upstream

The /dev/fuse device uses fiq->waitq and fasync to signal that requests
are available.  These mechanisms do not apply to virtio-fs.  This patch
introduces callbacks so alternative behavior can be used.

Note that queue_interrupt() changes along these lines:

  spin_lock(&fiq->waitq.lock);
  wake_up_locked(&fiq->waitq);
+ kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
  spin_unlock(&fiq->waitq.lock);
- kill_fasync(&fiq->fasync, SIGIO, POLL_IN);

Since queue_request() and queue_forget() also call kill_fasync() inside
the spinlock this should be safe.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NLiu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

fs/fuse/cuse.c

@@ -503,7 +503,7 @@ static int cuse_channel_open(struct inode *inode, struct file *file)
 	 * Limit the cuse channel to requests that can
 	 * be represented in file->f_cred->user_ns.
 	 */
-	fuse_conn_init(&cc->fc, file->f_cred->user_ns);
+	fuse_conn_init(&cc->fc, file->f_cred->user_ns, &fuse_dev_fiq_ops, NULL);
 
 	fud = fuse_dev_alloc(&cc->fc);
 	if (!fud) {

fs/fuse/dev.c

@@ -327,13 +327,33 @@ static u64 fuse_get_unique(struct fuse_iqueue *fiq)
 	return ++fiq->reqctr;
 }
 
-static void queue_request(struct fuse_iqueue *fiq, struct fuse_req *req)
+/**
+ * A new request is available, wake fiq->waitq
+ */
+static void fuse_dev_wake_and_unlock(struct fuse_iqueue *fiq)
+__releases(fiq->lock)
 {
-	req->in.h.len = sizeof(struct fuse_in_header) +
-		fuse_len_args(req->in.numargs, (struct fuse_arg *)req->in.args);
-	list_add_tail(&req->list, &fiq->pending);
 	wake_up(&fiq->waitq);
 	kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+	spin_unlock(&fiq->lock);
+}
+
+const struct fuse_iqueue_ops fuse_dev_fiq_ops = {
+	.wake_forget_and_unlock		= fuse_dev_wake_and_unlock,
+	.wake_interrupt_and_unlock	= fuse_dev_wake_and_unlock,
+	.wake_pending_and_unlock	= fuse_dev_wake_and_unlock,
+};
+EXPORT_SYMBOL_GPL(fuse_dev_fiq_ops);
+
+static void queue_request_and_unlock(struct fuse_iqueue *fiq,
+				     struct fuse_req *req)
+__releases(fiq->lock)
+{
+	req->in.h.len = sizeof(struct fuse_in_header) +
+		fuse_len_args(req->in.numargs,
+			      (struct fuse_arg *) req->in.args);
+	list_add_tail(&req->list, &fiq->pending);
+	fiq->ops->wake_pending_and_unlock(fiq);
 }
 
 void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
@@ -348,12 +368,11 @@ void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
 	if (fiq->connected) {
 		fiq->forget_list_tail->next = forget;
 		fiq->forget_list_tail = forget;
-		wake_up(&fiq->waitq);
-		kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+		fiq->ops->wake_forget_and_unlock(fiq);
 	} else {
 		kfree(forget);
+		spin_unlock(&fiq->lock);
 	}
-	spin_unlock(&fiq->lock);
 }
 
 static void flush_bg_queue(struct fuse_conn *fc)
@@ -368,8 +387,7 @@ static void flush_bg_queue(struct fuse_conn *fc)
 		fc->active_background++;
 		spin_lock(&fiq->lock);
 		req->in.h.unique = fuse_get_unique(fiq);
-		queue_request(fiq, req);
-		spin_unlock(&fiq->lock);
+		queue_request_and_unlock(fiq, req);
 	}
 }
 
@@ -436,10 +454,10 @@ static void queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
 	}
 	if (list_empty(&req->intr_entry)) {
 		list_add_tail(&req->intr_entry, &fiq->interrupts);
-		wake_up(&fiq->waitq);
+		fiq->ops->wake_interrupt_and_unlock(fiq);
+	} else {
+		spin_unlock(&fiq->lock);
 	}
-	spin_unlock(&fiq->lock);
-	kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
 }
 
 static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req)
@@ -498,13 +516,12 @@ static void __fuse_request_send(struct fuse_conn *fc, struct fuse_req *req)
 		req->out.h.error = -ENOTCONN;
 	} else {
 		req->in.h.unique = fuse_get_unique(fiq);
-		queue_request(fiq, req);
 		/*
 		 * acquire extra reference, since request is still
 		 * needed after fuse_request_end()
 		 */
 		__fuse_get_request(req);
-		spin_unlock(&fiq->lock);
+		queue_request_and_unlock(fiq, req);
 
 		request_wait_answer(fc, req);
 		/* Pairs with smp_wmb() in fuse_request_end() */
@@ -639,10 +656,11 @@ static int fuse_request_send_notify_reply(struct fuse_conn *fc,
 	req->in.h.unique = unique;
 	spin_lock(&fiq->lock);
 	if (fiq->connected) {
-		queue_request(fiq, req);
+		queue_request_and_unlock(fiq, req);
 		err = 0;
+	} else {
+		spin_unlock(&fiq->lock);
 	}
-	spin_unlock(&fiq->lock);
 
 	return err;
 }

fs/fuse/fuse_i.h

@@ -400,6 +400,39 @@ struct fuse_req {
 	struct file *stolen_file;
 };
 
+struct fuse_iqueue;
+
+/**
+ * Input queue callbacks
+ *
+ * Input queue signalling is device-specific.  For example, the /dev/fuse file
+ * uses fiq->waitq and fasync to wake processes that are waiting on queue
+ * readiness.  These callbacks allow other device types to respond to input
+ * queue activity.
+ */
+struct fuse_iqueue_ops {
+	/**
+	 * Signal that a forget has been queued
+	 */
+	void (*wake_forget_and_unlock)(struct fuse_iqueue *fiq)
+	__releases(fiq->lock);
+
+	/**
+	 * Signal that an INTERRUPT request has been queued
+	 */
+	void (*wake_interrupt_and_unlock)(struct fuse_iqueue *fiq)
+	__releases(fiq->lock);
+
+	/**
+	 * Signal that a request has been queued
+	 */
+	void (*wake_pending_and_unlock)(struct fuse_iqueue *fiq)
+	__releases(fiq->lock);
+};
+
+/** /dev/fuse input queue operations */
+extern const struct fuse_iqueue_ops fuse_dev_fiq_ops;
+
 struct fuse_iqueue {
 	/** Connection established */
 	unsigned connected;
@@ -428,6 +461,12 @@ struct fuse_iqueue {
 
 	/** O_ASYNC requests */
 	struct fasync_struct *fasync;
+
+	/** Device-specific callbacks */
+	const struct fuse_iqueue_ops *ops;
+
+	/** Device-specific state */
+	void *priv;
 };
 
 struct fuse_pqueue {
@@ -908,7 +947,8 @@ struct fuse_conn *fuse_conn_get(struct fuse_conn *fc);
 /**
  * Initialize fuse_conn
  */
-void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns);
+void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns,
+		    const struct fuse_iqueue_ops *fiq_ops, void *fiq_priv);
 
 /**
  * Release reference to fuse_conn
@@ -928,10 +968,14 @@ int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev,
  * Fill in superblock and initialize fuse connection
  * @sb: partially-initialized superblock to fill in
  * @mount_data: mount parameters
+ * @fiq_ops: fuse input queue operations
+ * @fiq_priv: device-specific state for fuse_iqueue
  * @fudptr: fuse_dev pointer to fill in, should contain NULL on entry
  */
 int fuse_fill_super_common(struct super_block *sb,
 			   struct fuse_mount_data *mount_data,
+			   const struct fuse_iqueue_ops *fiq_ops,
+			   void *fiq_priv,
 			   void **fudptr);
 void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req);
 

fs/fuse/inode.c

@@ -568,7 +568,9 @@ static int fuse_show_options(struct seq_file *m, struct dentry *root)
 	return 0;
 }
 
-static void fuse_iqueue_init(struct fuse_iqueue *fiq)
+static void fuse_iqueue_init(struct fuse_iqueue *fiq,
+			     const struct fuse_iqueue_ops *ops,
+			     void *priv)
 {
 	memset(fiq, 0, sizeof(struct fuse_iqueue));
 	spin_lock_init(&fiq->lock);
@@ -577,6 +579,8 @@ static void fuse_iqueue_init(struct fuse_iqueue *fiq)
 	INIT_LIST_HEAD(&fiq->interrupts);
 	fiq->forget_list_tail = &fiq->forget_list_head;
 	fiq->connected = 1;
+	fiq->ops = ops;
+	fiq->priv = priv;
 }
 
 static void fuse_pqueue_init(struct fuse_pqueue *fpq)
@@ -588,7 +592,8 @@ static void fuse_pqueue_init(struct fuse_pqueue *fpq)
 	fpq->connected = 1;
 }
 
-void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns)
+void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns,
+		    const struct fuse_iqueue_ops *fiq_ops, void *fiq_priv)
 {
 	memset(fc, 0, sizeof(*fc));
 	spin_lock_init(&fc->lock);
@@ -597,7 +602,7 @@ void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns)
 	atomic_set(&fc->dev_count, 1);
 	init_waitqueue_head(&fc->blocked_waitq);
 	init_waitqueue_head(&fc->reserved_req_waitq);
-	fuse_iqueue_init(&fc->iq);
+	fuse_iqueue_init(&fc->iq, fiq_ops, fiq_priv);
 	INIT_LIST_HEAD(&fc->bg_queue);
 	INIT_LIST_HEAD(&fc->entry);
 	INIT_LIST_HEAD(&fc->devices);
@@ -1042,6 +1047,8 @@ EXPORT_SYMBOL_GPL(fuse_dev_free);
 
 int fuse_fill_super_common(struct super_block *sb,
 			   struct fuse_mount_data *mount_data,
+			   const struct fuse_iqueue_ops *fiq_ops,
+			   void *fiq_priv,
 			   void **fudptr)
 {
 	struct fuse_dev *fud;
@@ -1089,7 +1096,7 @@ int fuse_fill_super_common(struct super_block *sb,
 	if (!fc)
 		goto err;
 
-	fuse_conn_init(fc, sb->s_user_ns);
+	fuse_conn_init(fc, sb->s_user_ns, fiq_ops, fiq_priv);
 	fc->release = fuse_free_conn;
 
 	fud = fuse_dev_alloc(fc);
@@ -1191,7 +1198,8 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 		goto err_fput;
 	__set_bit(FR_BACKGROUND, &init_req->flags);
 
-	err = fuse_fill_super_common(sb, &d, &file->private_data);
+	err = fuse_fill_super_common(sb, &d, &fuse_dev_fiq_ops, NULL,
+				     &file->private_data);
 	if (err < 0)
 		goto err_free_init_req;
 	/*