NFS: Add memory barriers to the nfs_client->cl_cons_state initialisation

Ensure that a process that uses the nfs_client->cl_cons_state test
for whether the initialisation process is finished does not read
stale data.

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

3 files changed, 7 insertions, 0 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index d35664287e14..a50bdfbbc429 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -459,6 +459,8 @@ static bool nfs4_cb_match_client(const struct sockaddr *addr,
             clp->cl_cons_state == NFS_CS_SESSION_INITING))
                 return false;
 
+        smp_rmb();
+
         /* Match the version and minorversion */
         if (clp->rpc_ops->version != 4 ||
             clp->cl_minorversion != minorversion)
@@ -539,6 +541,8 @@ nfs_found_client(const struct nfs_client_initdata *cl_init,
                 return ERR_PTR(error);
         }
 
+        smp_rmb();
+
         BUG_ON(clp->cl_cons_state != NFS_CS_READY);
 
         dprintk("<-- %s found nfs_client %p for %s\n",
@@ -597,6 +601,7 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
  */
 void nfs_mark_client_ready(struct nfs_client *clp, int state)
 {
+        smp_wmb();
         clp->cl_cons_state = state;
         wake_up_all(&nfs_client_active_wq);
 }
diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index 861be75eb165..b5b86a05059c 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -548,6 +548,7 @@ restart:
                 /* Skip nfs_clients that failed to initialise */
                 if (clp->cl_cons_state < 0)
                         continue;
+                smp_rmb();
                 if (clp->rpc_ops != &nfs_v4_clientops)
                         continue;
                 cl_dentry = clp->cl_idmap->idmap_pipe->dentry;
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index c856298def7d..8f39bb3ca1b3 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5621,6 +5621,7 @@ static int nfs41_check_session_ready(struct nfs_client *clp)
         }
         if (clp->cl_cons_state < NFS_CS_READY)
                 return -EPROTONOSUPPORT;
+        smp_rmb();
         return 0;
 }