On Sun, 2008-11-09 at 16:04 -0500, J. Bruce Fields wrote:
> We want to transition to a new gssd upcall which is text-based and more
> easily extensible.
>
> To simplify upgrades, as well as testing and debugging, it will help if
> we can upgrade gssd (to a version which understands the new upcall)
> without having to choose at boot (or module-load) time whether we want
> the new or the old upcall.
>
> We will do this by providing two different pipes: one named, as
> currently, after the mechanism (normally "krb5"), and supporting the
> old upcall. One named "gssd" and supporting the new upcall version.
>
> We allow gssd to indicate which version it supports by its choice of
> which pipe to open.
>
> As we have no interest in supporting *simultaneous* use of both
> versions, we'll forbid opening both pipes at the same time.
>
> So, add a new pipe_open callback to the rpc_pipefs api, which the gss
> code can use to track which pipes have been open, and to refuse opens of
> incompatible pipes.
>
> We only need this to be called on the first open of a given pipe.
>
> Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>
> ---
> include/linux/sunrpc/rpc_pipe_fs.h | 1 +
> net/sunrpc/rpc_pipe.c | 21 ++++++++++++++-------
> 2 files changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/sunrpc/rpc_pipe_fs.h b/include/linux/sunrpc/rpc_pipe_fs.h
> index 51b977a..cea764c 100644
> --- a/include/linux/sunrpc/rpc_pipe_fs.h
> +++ b/include/linux/sunrpc/rpc_pipe_fs.h
> @@ -15,6 +15,7 @@ struct rpc_pipe_ops {
> ssize_t (*upcall)(struct file *, struct rpc_pipe_msg *, char __user *, size_t);
> ssize_t (*downcall)(struct file *, const char __user *, size_t);
> void (*release_pipe)(struct inode *);
> + int (*open_pipe)(struct inode *);
> void (*destroy_msg)(struct rpc_pipe_msg *);
> };
>
> diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
> index 23a2b8f..4171ab7 100644
> --- a/net/sunrpc/rpc_pipe.c
> +++ b/net/sunrpc/rpc_pipe.c
> @@ -169,16 +169,23 @@ static int
> rpc_pipe_open(struct inode *inode, struct file *filp)
> {
> struct rpc_inode *rpci = RPC_I(inode);
> + int first_open = rpci->nreaders == 0 && rpci->nwriters == 0;
> int res = -ENXIO;
>
> mutex_lock(&inode->i_mutex);
> - if (rpci->ops != NULL) {
> - if (filp->f_mode & FMODE_READ)
> - rpci->nreaders ++;
> - if (filp->f_mode & FMODE_WRITE)
> - rpci->nwriters ++;
> - res = 0;
> + if (rpci->ops == NULL)
> + goto out;
> + if (first_open && rpci->ops->open_pipe) {
> + res = rpci->ops->open_pipe(inode);
> + if (res)
> + goto out;
> }
> + if (filp->f_mode & FMODE_READ)
> + rpci->nreaders++;
> + if (filp->f_mode & FMODE_WRITE)
> + rpci->nwriters++;
> + res = 0;
> +out:
BTW: This is racy. You have to set first_open _after_ you take the
inode->i_mutex.
> mutex_unlock(&inode->i_mutex);
> return res;
> }
> @@ -748,7 +755,7 @@ rpc_rmdir(struct dentry *dentry)
> * @name: name of pipe
> * @private: private data to associate with the pipe, for the caller's use
> * @ops: operations defining the behavior of the pipe: upcall, downcall,
> - * release_pipe, and destroy_msg.
> + * release_pipe, open_pipe, and destroy_msg.
> * @flags: rpc_inode flags
> *
> * Data is made available for userspace to read by calls to
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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