Re: [PATCH v3] fuse: Add support for passthrough read/write

[Jann Horn]

On Wed, Jan 20, 2016 at 03:20:34PM -0800, Nikhilesh Reddy wrote:
> Add support for filesystem passthrough read/write of files
> when enabled in userspace through the option FUSE_PASSTHROUGH.
[...]
> +	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) {
> +		pr_err("FUSE: maximum fs stacking depth exceeded, cannot use passthrough for this file\n");
> +		return;
> +	}

I think this needs an fput() in the error case to prevent a refcount leak.

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