Re: [PATCH 08/22] SUNRPC: pass buffer size to svc_addsock() and svc_sock_names()

["J. Bruce Fields" <bfields@fieldses.org>]

On Fri, Dec 12, 2008 at 04:58:05PM -0500, Chuck Lever wrote:
> Pass the size of the output buffer to the RPC functions that construct
> the list of socket names in that buffer.  Add documenting comments to
> these functions.
> 
> This is a cosmetic change for now.  A subsequent patch will make sure
> the buffer length is passed to one_sock_name(), where the length will
> actually be useful.
> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
> 
>  fs/nfsd/nfsctl.c               |   12 ++++++++----
>  include/linux/sunrpc/svcsock.h |    6 ++++--
>  net/sunrpc/svcsock.c           |   34 +++++++++++++++++++++++++++++-----
>  3 files changed, 41 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index 22fc8e5..19db9f4 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -898,7 +898,7 @@ static ssize_t __write_ports_names(char *buf, size_t size)
>  static ssize_t __write_ports_addfd(char *buf, size_t size)
>  {
>  	char *mesg = buf;
> -	int fd, err;
> +	int fd, err, len;
>  
>  	err = get_int(&mesg, &fd);
>  	if (err || fd < 0)
> @@ -908,13 +908,16 @@ static ssize_t __write_ports_addfd(char *buf, size_t size)
>  	if (err)
>  		return err;
>  
> -	err = svc_addsock(nfsd_serv, fd, buf);
> +	len = SIMPLE_TRANSACTION_LIMIT;
> +	err = svc_addsock(nfsd_serv, fd, buf, len);
>  	if (err < 0)
>  		return err;
> +	len -= err;
>  
>  	err = lockd_up();
>  	if (err < 0)
> -		svc_sock_names(buf + strlen(buf) + 1, nfsd_serv, buf);
> +		svc_sock_names(nfsd_serv, buf + strlen(buf) + 1,
> +				len - strlen(buf) - 1, buf);

Since you already did len -= err above, aren't you effectly subtracing
off strlen(buf) twice here?  (And should that "len -= err" actually have
been a "len -= err + 1"?)

>  
>  	/* Decrease the count, but don't shut down the the service */
>  	nfsd_serv->sv_nrthreads--;
> @@ -935,7 +938,8 @@ static ssize_t __write_ports_delfd(char *buf, size_t size)
>  		return -ENOMEM;
>  
>  	if (nfsd_serv)
> -		len = svc_sock_names(buf, nfsd_serv, toclose);
> +		len = svc_sock_names(nfsd_serv, buf,
> +					SIMPLE_TRANSACTION_LIMIT, toclose);
>  	if (len >= 0)
>  		lockd_down();
>  
> diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
> index 483e103..f57ce85 100644
> --- a/include/linux/sunrpc/svcsock.h
> +++ b/include/linux/sunrpc/svcsock.h
> @@ -38,8 +38,10 @@ int		svc_recv(struct svc_rqst *, long);
>  int		svc_send(struct svc_rqst *);
>  void		svc_drop(struct svc_rqst *);
>  void		svc_sock_update_bufs(struct svc_serv *serv);
> -int		svc_sock_names(char *buf, struct svc_serv *serv, char *toclose);
> -int		svc_addsock(struct svc_serv *serv, int fd, char *name_return);
> +int		svc_sock_names(struct svc_serv *serv, char *buf, size_t buflen,
> +					char *toclose);
> +int		svc_addsock(struct svc_serv *serv, int fd, char *name_return,
> +					size_t len);
>  void		svc_init_xprt_sock(void);
>  void		svc_cleanup_xprt_sock(void);
>  
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index a1951dc..39f5015 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -263,8 +263,23 @@ static int one_sock_name(char *buf, struct svc_sock *svsk)
>  	return len;
>  }
>  
> -int
> -svc_sock_names(char *buf, struct svc_serv *serv, char *toclose)
> +/**
> + * svc_sock_names - construct a list of listener names in a string
> + * @serv: pointer to RPC service
> + * @buf: pointer to a buffer to fill in with socket names
> + * @buflen: size of the buffer to be filled
> + * @toclose: pointer to '\0'-terminated C string containing the name
> + *		of a listener to be closed
> + *
> + * Fills in @buf with a '\n'-separated list of names of listener
> + * sockets.  If @toclose is not NULL, the socket named by @toclose
> + * is closed, and is not included in the output list.
> + *
> + * Returns positive length of the socket name string, or a negative
> + * errno value on error.
> + */
> +int svc_sock_names(struct svc_serv *serv, char *buf, size_t buflen,
> +		   char *toclose)
>  {
>  	struct svc_sock *svsk, *closesk = NULL;
>  	int len = 0;
> @@ -1165,9 +1180,18 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
>  	return svsk;
>  }
>  
> -int svc_addsock(struct svc_serv *serv,
> -		int fd,
> -		char *name_return)
> +/**
> + * svc_addsock - add a listener socket to an RPC service
> + * @serv: pointer to RPC service to which to add a new listener
> + * @fd: file descriptor of the new listener
> + * @name_return: pointer to buffer to pass back name of listener
> + * @len: size of the buffer
> + *
> + * Fills in socket name and returns positive length of name if successful.
> + * Name is terminated with '\n'.  On error, returns a negative errno
> + * value.
> + */
> +int svc_addsock(struct svc_serv *serv, int fd, char *name_return, size_t len)
>  {
>  	int err = 0;
>  	struct socket *so = sockfd_lookup(fd, &err);
>