fuse: introduce per-instance fuse_dev structure

Allow fuse device clones to refer to be distinguished.  This patch just
adds the infrastructure by associating a separate "struct fuse_dev" with
each clone.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reviewed-by: Ashish Samant <ashish.samant@oracle.com>

fs/fuse/cuse.c

@@ -489,6 +489,7 @@ static void cuse_fc_release(struct fuse_conn *fc)
  */
 static int cuse_channel_open(struct inode *inode, struct file *file)
 {
+	struct fuse_dev *fud;
 	struct cuse_conn *cc;
 	int rc;
 
@@ -499,16 +500,22 @@ static int cuse_channel_open(struct inode *inode, struct file *file)
 
 	fuse_conn_init(&cc->fc);
 
+	fud = fuse_dev_alloc(&cc->fc);
+	if (!fud) {
+		kfree(cc);
+		return -ENOMEM;
+	}
+
 	INIT_LIST_HEAD(&cc->list);
 	cc->fc.release = cuse_fc_release;
 
 	cc->fc.initialized = 1;
 	rc = cuse_send_init(cc);
 	if (rc) {
-		fuse_conn_put(&cc->fc);
+		fuse_dev_free(fud);
 		return rc;
 	}
-	file->private_data = &cc->fc;	/* channel owns base reference to cc */
+	file->private_data = fud;
 
 	return 0;
 }
@@ -526,7 +533,8 @@ static int cuse_channel_open(struct inode *inode, struct file *file)
  */
 static int cuse_channel_release(struct inode *inode, struct file *file)
 {
-	struct cuse_conn *cc = fc_to_cc(file->private_data);
+	struct fuse_dev *fud = file->private_data;
+	struct cuse_conn *cc = fc_to_cc(fud->fc);
 	int rc;
 
 	/* remove from the conntbl, no more access from this point on */

fs/fuse/dev.c

@@ -25,13 +25,13 @@ MODULE_ALIAS("devname:fuse");
 
 static struct kmem_cache *fuse_req_cachep;
 
-static struct fuse_conn *fuse_get_conn(struct file *file)
+static struct fuse_dev *fuse_get_dev(struct file *file)
 {
 	/*
 	 * Lockless access is OK, because file->private data is set
 	 * once during mount and is valid until the file is released.
 	 */
-	return file->private_data;
+	return ACCESS_ONCE(file->private_data);
 }
 
 static void fuse_request_init(struct fuse_req *req, struct page **pages,
@@ -1348,8 +1348,9 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, struct iov_iter *to)
 {
 	struct fuse_copy_state cs;
 	struct file *file = iocb->ki_filp;
-	struct fuse_conn *fc = fuse_get_conn(file);
-	if (!fc)
+	struct fuse_dev *fud = fuse_get_dev(file);
+
+	if (!fud)
 		return -EPERM;
 
 	if (!iter_is_iovec(to))
@@ -1357,7 +1358,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, struct iov_iter *to)
 
 	fuse_copy_init(&cs, 1, to);
 
-	return fuse_dev_do_read(fc, file, &cs, iov_iter_count(to));
+	return fuse_dev_do_read(fud->fc, file, &cs, iov_iter_count(to));
 }
 
 static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
@@ -1369,8 +1370,9 @@ static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
 	int do_wakeup = 0;
 	struct pipe_buffer *bufs;
 	struct fuse_copy_state cs;
-	struct fuse_conn *fc = fuse_get_conn(in);
-	if (!fc)
+	struct fuse_dev *fud = fuse_get_dev(in);
+
+	if (!fud)
 		return -EPERM;
 
 	bufs = kmalloc(pipe->buffers * sizeof(struct pipe_buffer), GFP_KERNEL);
@@ -1380,7 +1382,7 @@ static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
 	fuse_copy_init(&cs, 1, NULL);
 	cs.pipebufs = bufs;
 	cs.pipe = pipe;
-	ret = fuse_dev_do_read(fc, in, &cs, len);
+	ret = fuse_dev_do_read(fud->fc, in, &cs, len);
 	if (ret < 0)
 		goto out;
 
@@ -1954,8 +1956,9 @@ static ssize_t fuse_dev_do_write(struct fuse_conn *fc,
 static ssize_t fuse_dev_write(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct fuse_copy_state cs;
-	struct fuse_conn *fc = fuse_get_conn(iocb->ki_filp);
-	if (!fc)
+	struct fuse_dev *fud = fuse_get_dev(iocb->ki_filp);
+
+	if (!fud)
 		return -EPERM;
 
 	if (!iter_is_iovec(from))
@@ -1963,7 +1966,7 @@ static ssize_t fuse_dev_write(struct kiocb *iocb, struct iov_iter *from)
 
 	fuse_copy_init(&cs, 0, from);
 
-	return fuse_dev_do_write(fc, &cs, iov_iter_count(from));
+	return fuse_dev_do_write(fud->fc, &cs, iov_iter_count(from));
 }
 
 static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
@@ -1974,12 +1977,12 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
 	unsigned idx;
 	struct pipe_buffer *bufs;
 	struct fuse_copy_state cs;
-	struct fuse_conn *fc;
+	struct fuse_dev *fud;
 	size_t rem;
 	ssize_t ret;
 
-	fc = fuse_get_conn(out);
-	if (!fc)
+	fud = fuse_get_dev(out);
+	if (!fud)
 		return -EPERM;
 
 	bufs = kmalloc(pipe->buffers * sizeof(struct pipe_buffer), GFP_KERNEL);
@@ -2034,7 +2037,7 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
 	if (flags & SPLICE_F_MOVE)
 		cs.move_pages = 1;
 
-	ret = fuse_dev_do_write(fc, &cs, len);
+	ret = fuse_dev_do_write(fud->fc, &cs, len);
 
 	for (idx = 0; idx < nbuf; idx++) {
 		struct pipe_buffer *buf = &bufs[idx];
@@ -2049,11 +2052,12 @@ static unsigned fuse_dev_poll(struct file *file, poll_table *wait)
 {
 	unsigned mask = POLLOUT | POLLWRNORM;
 	struct fuse_iqueue *fiq;
-	struct fuse_conn *fc = fuse_get_conn(file);
-	if (!fc)
+	struct fuse_dev *fud = fuse_get_dev(file);
+
+	if (!fud)
 		return POLLERR;
 
-	fiq = &fc->iq;
+	fiq = &fud->fc->iq;
 	poll_wait(file, &fiq->waitq, wait);
 
 	spin_lock(&fiq->waitq.lock);
@@ -2175,12 +2179,15 @@ EXPORT_SYMBOL_GPL(fuse_abort_conn);
 
 int fuse_dev_release(struct inode *inode, struct file *file)
 {
-	struct fuse_conn *fc = fuse_get_conn(file);
-	if (fc) {
+	struct fuse_dev *fud = fuse_get_dev(file);
+
+	if (fud) {
+		struct fuse_conn *fc = fud->fc;
+
 		WARN_ON(!list_empty(&fc->pq.io));
 		WARN_ON(fc->iq.fasync != NULL);
 		fuse_abort_conn(fc);
-		fuse_conn_put(fc);
+		fuse_dev_free(fud);
 	}
 
 	return 0;
@@ -2189,20 +2196,27 @@ EXPORT_SYMBOL_GPL(fuse_dev_release);
 
 static int fuse_dev_fasync(int fd, struct file *file, int on)
 {
-	struct fuse_conn *fc = fuse_get_conn(file);
-	if (!fc)
+	struct fuse_dev *fud = fuse_get_dev(file);
+
+	if (!fud)
 		return -EPERM;
 
 	/* No locking - fasync_helper does its own locking */
-	return fasync_helper(fd, file, on, &fc->iq.fasync);
+	return fasync_helper(fd, file, on, &fud->fc->iq.fasync);
 }
 
 static int fuse_device_clone(struct fuse_conn *fc, struct file *new)
 {
+	struct fuse_dev *fud;
+
 	if (new->private_data)
 		return -EINVAL;
 
-	new->private_data = fuse_conn_get(fc);
+	fud = fuse_dev_alloc(fc);
+	if (!fud)
+		return -ENOMEM;
+
+	new->private_data = fud;
 
 	return 0;
 }
@@ -2221,11 +2235,11 @@ static long fuse_dev_ioctl(struct file *file, unsigned int cmd,
 
 			err = -EINVAL;
 			if (old) {
-				struct fuse_conn *fc = fuse_get_conn(old);
+				struct fuse_dev *fud = fuse_get_dev(old);
 
-				if (fc) {
+				if (fud) {
 					mutex_lock(&fuse_mutex);
-					err = fuse_device_clone(fc, file);
+					err = fuse_device_clone(fud->fc, file);
 					mutex_unlock(&fuse_mutex);
 				}
 				fput(old);

fs/fuse/fuse_i.h

@@ -417,6 +417,17 @@ struct fuse_pqueue {
 	struct list_head io;
 };
 
+/**
+ * Fuse device instance
+ */
+struct fuse_dev {
+	/** Fuse connection for this device */
+	struct fuse_conn *fc;
+
+	/** list entry on fc->devices */
+	struct list_head entry;
+};
+
 /**
  * A Fuse connection.
  *
@@ -629,6 +640,9 @@ struct fuse_conn {
 
 	/** Read/write semaphore to hold when accessing sb. */
 	struct rw_semaphore killsb;
+
+	/** List of device instances belonging to this connection */
+	struct list_head devices;
 };
 
 static inline struct fuse_conn *get_fuse_conn_super(struct super_block *sb)
@@ -841,6 +855,9 @@ void fuse_conn_init(struct fuse_conn *fc);
  */
 void fuse_conn_put(struct fuse_conn *fc);
 
+struct fuse_dev *fuse_dev_alloc(struct fuse_conn *fc);
+void fuse_dev_free(struct fuse_dev *fud);
+
 /**
  * Add connection to control filesystem
  */

fs/fuse/inode.c

@@ -598,6 +598,7 @@ void fuse_conn_init(struct fuse_conn *fc)
 	fuse_pqueue_init(&fc->pq);
 	INIT_LIST_HEAD(&fc->bg_queue);
 	INIT_LIST_HEAD(&fc->entry);
+	INIT_LIST_HEAD(&fc->devices);
 	atomic_set(&fc->num_waiting, 0);
 	fc->max_background = FUSE_DEFAULT_MAX_BACKGROUND;
 	fc->congestion_threshold = FUSE_DEFAULT_CONGESTION_THRESHOLD;
@@ -945,6 +946,7 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
 
 static void fuse_free_conn(struct fuse_conn *fc)
 {
+	WARN_ON(!list_empty(&fc->devices));
 	kfree_rcu(fc, rcu);
 }
 
@@ -990,8 +992,41 @@ static int fuse_bdi_init(struct fuse_conn *fc, struct super_block *sb)
 	return 0;
 }
 
+struct fuse_dev *fuse_dev_alloc(struct fuse_conn *fc)
+{
+	struct fuse_dev *fud;
+
+	fud = kzalloc(sizeof(struct fuse_dev), GFP_KERNEL);
+	if (fud) {
+		fud->fc = fuse_conn_get(fc);
+
+		spin_lock(&fc->lock);
+		list_add_tail(&fud->entry, &fc->devices);
+		spin_unlock(&fc->lock);
+	}
+
+	return fud;
+}
+EXPORT_SYMBOL_GPL(fuse_dev_alloc);
+
+void fuse_dev_free(struct fuse_dev *fud)
+{
+	struct fuse_conn *fc = fud->fc;
+
+	if (fc) {
+		spin_lock(&fc->lock);
+		list_del(&fud->entry);
+		spin_unlock(&fc->lock);
+
+		fuse_conn_put(fc);
+	}
+	kfree(fud);
+}
+EXPORT_SYMBOL_GPL(fuse_dev_free);
+
 static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 {
+	struct fuse_dev *fud;
 	struct fuse_conn *fc;
 	struct inode *root;
 	struct fuse_mount_data d;
@@ -1043,11 +1078,15 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 	fuse_conn_init(fc);
 	fc->release = fuse_free_conn;
 
+	fud = fuse_dev_alloc(fc);
+	if (!fud)
+		goto err_put_conn;
+
 	fc->dev = sb->s_dev;
 	fc->sb = sb;
 	err = fuse_bdi_init(fc, sb);
 	if (err)
-		goto err_put_conn;
+		goto err_dev_free;
 
 	sb->s_bdi = &fc->bdi;
 
@@ -1068,7 +1107,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 	root = fuse_get_root_inode(sb, d.rootmode);
 	root_dentry = d_make_root(root);
 	if (!root_dentry)
-		goto err_put_conn;
+		goto err_dev_free;
 	/* only now - we want root dentry with NULL ->d_op */
 	sb->s_d_op = &fuse_dentry_operations;
 
@@ -1094,7 +1133,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 
 	list_add_tail(&fc->entry, &fuse_conn_list);
 	sb->s_root = root_dentry;
-	file->private_data = fuse_conn_get(fc);
+	file->private_data = fud;
 	mutex_unlock(&fuse_mutex);
 	/*
 	 * atomic_dec_and_test() in fput() provides the necessary
@@ -1113,6 +1152,8 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 	fuse_request_free(init_req);
  err_put_root:
 	dput(root_dentry);
+ err_dev_free:
+	fuse_dev_free(fud);
  err_put_conn:
 	fuse_bdi_destroy(fc);
 	fuse_conn_put(fc);