NFS refactor nfs_find_client and reference client across callback processing

Fixes a bug where the nfs_client could be freed during callback processing.
Refactor nfs_find_client to use minorversion specific means to locate the
correct nfs_client structure.

In the NFS layer, V4.0 clients are found using the callback_ident field in the
CB_COMPOUND header.  V4.1 clients are found using the sessionID in the
CB_SEQUENCE operation which is also compared against the sessionID associated
with the back channel thread after a successful CREATE_SESSION.

Each of these methods finds the one an only nfs_client associated
with the incoming callback request - so nfs_find_client_next is not needed.

In the RPC layer, the pg_authenticate call needs to find the nfs_client. For
the v4.0 callback service, the callback identifier has not been decoded so a
search by address, version, and minorversion is used.  The sessionid for the
sessions based callback service has (usually) not been set for the
pg_authenticate on a CB_NULL call which can be sent prior to the return
of a CREATE_SESSION call, so the sessionid associated with the back channel
thread is not used to find the client in pg_authenticate for CB_NULL calls.

Pass the referenced nfs_client to each CB_COMPOUND operation being proceesed
via the new cb_process_state structure. The reference is held across
cb_compound processing.

Use the new cb_process_state struct to move the NFS4ERR_RETRY_UNCACHED_REP
processing from process_op into nfs4_callback_sequence where it belongs.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 18 insertions, 3 deletions

diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index c0b05497972b..15677e7bede5 100644
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -16,9 +16,7 @@
 #include <linux/freezer.h>
 #include <linux/kthread.h>
 #include <linux/sunrpc/svcauth_gss.h>
-#if defined(CONFIG_NFS_V4_1)
 #include <linux/sunrpc/bc_xprt.h>
-#endif
 
 #include <net/inet_sock.h>
 
@@ -384,6 +382,23 @@ static int check_gss_callback_principal(struct nfs_client *clp,
         return SVC_OK;
 }
 
+/* pg_authenticate method helper */
+static struct nfs_client *nfs_cb_find_client(struct svc_rqst *rqstp)
+{
+        struct nfs4_sessionid *sessionid = bc_xprt_sid(rqstp);
+        int is_cb_compound = rqstp->rq_proc == CB_COMPOUND ? 1 : 0;
+
+        dprintk("--> %s rq_proc %d\n", __func__, rqstp->rq_proc);
+        if (svc_is_backchannel(rqstp))
+                /* Sessionid (usually) set after CB_NULL ping */
+                return nfs4_find_client_sessionid(svc_addr(rqstp), sessionid,
+                                                  is_cb_compound);
+        else
+                /* No callback identifier in pg_authenticate */
+                return nfs4_find_client_no_ident(svc_addr(rqstp));
+}
+
+/* pg_authenticate method for nfsv4 callback threads. */
 static int nfs_callback_authenticate(struct svc_rqst *rqstp)
 {
         struct nfs_client *clp;
@@ -391,7 +406,7 @@ static int nfs_callback_authenticate(struct svc_rqst *rqstp)
         int ret = SVC_OK;
 
         /* Don't talk to strangers */
-        clp = nfs_find_client(svc_addr(rqstp), 4);
+        clp = nfs_cb_find_client(rqstp);
         if (clp == NULL)
                 return SVC_DROP;