1 files changed, 132 insertions, 0 deletions
diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c
new file mode 100644
index 000000000000..785af63acabd
--- /dev/null
+++ b/fs/fuse/passthrough.c
@@ -0,0 +1,132 @@
+/*
+ * Copyright (c) 2015-2016, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include "fuse_passthrough.h"
+
+#include <linux/aio.h>
+#include <linux/fs_stack.h>
+
+void fuse_setup_passthrough(struct fuse_conn *fc, struct fuse_req *req)
+{
+	int daemon_fd, fs_stack_depth;
+	unsigned open_out_index;
+	struct file *passthrough_filp;
+	struct inode *passthrough_inode;
+	struct super_block *passthrough_sb;
+	struct fuse_open_out *open_out;
+
+	req->passthrough_filp = NULL;
+
+	if (!(fc->passthrough))
+		return;
+
+	if ((req->in.h.opcode != FUSE_OPEN) &&
+	    (req->in.h.opcode != FUSE_CREATE))
+		return;
+
+	open_out_index = req->in.numargs - 1;
+
+	BUG_ON(open_out_index != 0 && open_out_index != 1);
+	BUG_ON(req->out.args[open_out_index].size != sizeof(*open_out));
+
+	open_out = req->out.args[open_out_index].value;
+
+	daemon_fd = (int)open_out->passthrough_fd;
+	if (daemon_fd < 0)
+		return;
+
+	passthrough_filp = fget_raw(daemon_fd);
+	if (!passthrough_filp)
+		return;
+
+	passthrough_inode = file_inode(passthrough_filp);
+	passthrough_sb = passthrough_inode->i_sb;
+	fs_stack_depth = passthrough_sb->s_stack_depth + 1;
+
+	/* If we reached the stacking limit go through regular io */
+	if (fs_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
+		/* Release the passthrough file. */
+		fput(passthrough_filp);
+		pr_err("FUSE: maximum fs stacking depth exceeded, cannot use passthrough for this file\n");
+		return;
+	}
+	req->passthrough_filp = passthrough_filp;
+}
+
+static ssize_t fuse_passthrough_read_write_iter(struct kiocb *iocb,
+					    struct iov_iter *iter, int do_write)
+{
+	ssize_t ret_val;
+	struct fuse_file *ff;
+	struct file *fuse_file, *passthrough_filp;
+	struct inode *fuse_inode, *passthrough_inode;
+	struct fuse_conn *fc;
+
+	ff = iocb->ki_filp->private_data;
+	fuse_file = iocb->ki_filp;
+	passthrough_filp = ff->passthrough_filp;
+	fc = ff->fc;
+
+	/* lock passthrough file to prevent it from being released */
+	get_file(passthrough_filp);
+	iocb->ki_filp = passthrough_filp;
+	fuse_inode = fuse_file->f_path.dentry->d_inode;
+	passthrough_inode = file_inode(passthrough_filp);
+
+	if (do_write) {
+		if (!passthrough_filp->f_op->write_iter)
+			return -EIO;
+		ret_val = passthrough_filp->f_op->write_iter(iocb, iter);
+
+		if (ret_val >= 0 || ret_val == -EIOCBQUEUED) {
+			spin_lock(&fc->lock);
+			fsstack_copy_inode_size(fuse_inode, passthrough_inode);
+			spin_unlock(&fc->lock);
+			fsstack_copy_attr_times(fuse_inode, passthrough_inode);
+		}
+	} else {
+		if (!passthrough_filp->f_op->read_iter)
+			return -EIO;
+		ret_val = passthrough_filp->f_op->read_iter(iocb, iter);
+		if (ret_val >= 0 || ret_val == -EIOCBQUEUED)
+			fsstack_copy_attr_atime(fuse_inode, passthrough_inode);
+	}
+
+	iocb->ki_filp = fuse_file;
+
+	/* unlock passthrough file */
+	fput(passthrough_filp);
+
+	return ret_val;
+}
+
+ssize_t fuse_passthrough_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	return fuse_passthrough_read_write_iter(iocb, to, 0);
+}
+
+ssize_t fuse_passthrough_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	return fuse_passthrough_read_write_iter(iocb, from, 1);
+}
+
+void fuse_passthrough_release(struct fuse_file *ff)
+{
+	if (!(ff->passthrough_filp))
+		return;
+
+	/* Release the passthrough file. */
+	fput(ff->passthrough_filp);
+	ff->passthrough_filp = NULL;
+}