nfs41: client callback structures

Adds new list of rpc_xprt structures, and a readers/writers lock to
protect the list.  The list is used to preallocate resources for
the backchannel during backchannel requests.  Callbacks are not
expected to cause significant latency, so only one callback will
be allowed at this time.

It also adds a pointer to the NFS callback service so that
requests can be directed to it for processing.

New callback members added to svc_serv. The NFSv4.1 callback service will
sleep on the svc_serv->svc_cb_waitq until new callback requests arrive.
The request will be queued in svc_serv->svc_cb_list. This patch adds this
list, the sleep queue and spinlock to svc_serv.

[nfs41: NFSv4.1 callback support]
Signed-off-by: Ricardo Labiaga <ricardo.labiaga@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 08afe43118f4..703af7ebf6cf 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -97,6 +97,12 @@ struct rpc_rqst {
 
         unsigned long           rq_xtime;       /* when transmitted */
         int                     rq_ntrans;
+
+#if defined(CONFIG_NFS_V4_1)
+        struct list_head        rq_bc_list;     /* Callback service list */
+        unsigned long           rq_bc_pa_state; /* Backchannel prealloc state */
+        struct list_head        rq_bc_pa_list;  /* Backchannel prealloc list */
+#endif /* CONFIG_NFS_V4_1 */
 };
 #define rq_svec                 rq_snd_buf.head
 #define rq_slen                 rq_snd_buf.len
@@ -174,6 +180,14 @@ struct rpc_xprt {
         spinlock_t              reserve_lock;   /* lock slot table */
         u32                     xid;            /* Next XID value to use */
         struct rpc_task *       snd_task;       /* Task blocked in send */
+#if defined(CONFIG_NFS_V4_1)
+        struct svc_serv         *bc_serv;       /* The RPC service which will */
+                                                /* process the callback */
+        spinlock_t              bc_pa_lock;     /* Protects the preallocated
+                                                 * items */
+        struct list_head        bc_pa_list;     /* List of preallocated
+                                                 * backchannel rpc_rqst's */
+#endif /* CONFIG_NFS_V4_1 */
         struct list_head        recv;
 
         struct {
@@ -192,6 +206,14 @@ struct rpc_xprt {
         const char              *address_strings[RPC_DISPLAY_MAX];
 };
 
+#if defined(CONFIG_NFS_V4_1)
+/*
+ * Backchannel flags
+ */
+#define RPC_BC_PA_IN_USE        0x0001          /* Preallocated backchannel */
+                                                /* buffer in use */
+#endif /* CONFIG_NFS_V4_1 */
+
 struct xprt_create {
         int                     ident;          /* XPRT_TRANSPORT identifier */
         struct sockaddr *       srcaddr;        /* optional local address */