SUNRPC: Convert gss_ctx_lock to an RCU lock

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

2 files changed, 37 insertions, 17 deletions

diff --git a/include/linux/sunrpc/auth_gss.h b/include/linux/sunrpc/auth_gss.h
index 0bd1d06777b9..67658e17a375 100644
--- a/include/linux/sunrpc/auth_gss.h
+++ b/include/linux/sunrpc/auth_gss.h
@@ -75,6 +75,7 @@ struct gss_cl_ctx {
         struct xdr_netobj       gc_wire_ctx;
         u32                     gc_win;
         unsigned long           gc_expiry;
+        struct rcu_head         gc_rcu;
 };
 
 struct gss_upcall_msg;
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index 8653a92144ae..15da6f82db36 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -78,8 +78,6 @@ static const struct rpc_credops gss_credops;
 /* dump the buffer in `emacs-hexl' style */
 #define isprint(c)      ((c > 0x1f) && (c < 0x7f))
 
-static DEFINE_RWLOCK(gss_ctx_lock);
-
 struct gss_auth {
         struct rpc_auth rpc_auth;
         struct gss_api_mech *mech;
@@ -88,7 +86,7 @@ struct gss_auth {
         struct dentry *dentry;
 };
 
-static void gss_destroy_ctx(struct gss_cl_ctx *);
+static void gss_free_ctx(struct gss_cl_ctx *);
 static struct rpc_pipe_ops gss_upcall_ops;
 
 static inline struct gss_cl_ctx *
@@ -102,20 +100,24 @@ static inline void
 gss_put_ctx(struct gss_cl_ctx *ctx)
 {
         if (atomic_dec_and_test(&ctx->count))
-                gss_destroy_ctx(ctx);
+                gss_free_ctx(ctx);
 }
 
+/* gss_cred_set_ctx:
+ * called by gss_upcall_callback and gss_create_upcall in order
+ * to set the gss context. The actual exchange of an old context
+ * and a new one is protected by the inode->i_lock.
+ */
 static void
 gss_cred_set_ctx(struct rpc_cred *cred, struct gss_cl_ctx *ctx)
 {
         struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
         struct gss_cl_ctx *old;
-        write_lock(&gss_ctx_lock);
+
         old = gss_cred->gc_ctx;
-        gss_cred->gc_ctx = ctx;
+        rcu_assign_pointer(gss_cred->gc_ctx, ctx);
         set_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
         clear_bit(RPCAUTH_CRED_NEW, &cred->cr_flags);
-        write_unlock(&gss_ctx_lock);
         if (old)
                 gss_put_ctx(old);
 }
@@ -126,10 +128,10 @@ gss_cred_is_uptodate_ctx(struct rpc_cred *cred)
         struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
         int res = 0;
 
-        read_lock(&gss_ctx_lock);
+        rcu_read_lock();
         if (test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) && gss_cred->gc_ctx)
                 res = 1;
-        read_unlock(&gss_ctx_lock);
+        rcu_read_unlock();
         return res;
 }
 
@@ -168,10 +170,10 @@ gss_cred_get_ctx(struct rpc_cred *cred)
         struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
         struct gss_cl_ctx *ctx = NULL;
 
-        read_lock(&gss_ctx_lock);
+        rcu_read_lock();
         if (gss_cred->gc_ctx)
                 ctx = gss_get_ctx(gss_cred->gc_ctx);
-        read_unlock(&gss_ctx_lock);
+        rcu_read_unlock();
         return ctx;
 }
 
@@ -333,11 +335,11 @@ gss_upcall_callback(struct rpc_task *task)
         struct gss_upcall_msg *gss_msg = gss_cred->gc_upcall;
         struct inode *inode = gss_msg->auth->dentry->d_inode;
 
+        spin_lock(&inode->i_lock);
         if (gss_msg->ctx)
                 gss_cred_set_ctx(task->tk_msg.rpc_cred, gss_get_ctx(gss_msg->ctx));
         else
                 task->tk_status = gss_msg->msg.errno;
-        spin_lock(&inode->i_lock);
         gss_cred->gc_upcall = NULL;
         rpc_wake_up_status(&gss_msg->rpc_waitqueue, gss_msg->msg.errno);
         spin_unlock(&inode->i_lock);
@@ -440,7 +442,6 @@ gss_create_upcall(struct gss_auth *gss_auth, struct gss_cred *gss_cred)
                 prepare_to_wait(&gss_msg->waitqueue, &wait, TASK_INTERRUPTIBLE);
                 spin_lock(&inode->i_lock);
                 if (gss_msg->ctx != NULL || gss_msg->msg.errno < 0) {
-                        spin_unlock(&inode->i_lock);
                         break;
                 }
                 spin_unlock(&inode->i_lock);
@@ -454,6 +455,7 @@ gss_create_upcall(struct gss_auth *gss_auth, struct gss_cred *gss_cred)
                 gss_cred_set_ctx(cred, gss_get_ctx(gss_msg->ctx));
         else
                 err = gss_msg->msg.errno;
+        spin_unlock(&inode->i_lock);
 out_intr:
         finish_wait(&gss_msg->waitqueue, &wait);
         gss_release_msg(gss_msg);
@@ -681,9 +683,9 @@ gss_destroy(struct rpc_auth *auth)
  * to create a new cred or context, so they check that things have been
  * allocated before freeing them. */
 static void
-gss_destroy_ctx(struct gss_cl_ctx *ctx)
+gss_do_free_ctx(struct gss_cl_ctx *ctx)
 {
-        dprintk("RPC:       gss_destroy_ctx\n");
+        dprintk("RPC:       gss_free_ctx\n");
 
         if (ctx->gc_gss_ctx)
                 gss_delete_sec_context(&ctx->gc_gss_ctx);
@@ -693,11 +695,22 @@ gss_destroy_ctx(struct gss_cl_ctx *ctx)
 }
 
 static void
+gss_free_ctx_callback(struct rcu_head *head)
+{
+        struct gss_cl_ctx *ctx = container_of(head, struct gss_cl_ctx, gc_rcu);
+        gss_do_free_ctx(ctx);
+}
+
+static void
+gss_free_ctx(struct gss_cl_ctx *ctx)
+{
+        call_rcu(&ctx->gc_rcu, gss_free_ctx_callback);
+}
+
+static void
 gss_free_cred(struct gss_cred *gss_cred)
 {
         dprintk("RPC:       gss_free_cred %p\n", gss_cred);
-        if (gss_cred->gc_ctx)
-                gss_put_ctx(gss_cred->gc_ctx);
         kfree(gss_cred);
 }
 
@@ -711,7 +724,13 @@ gss_free_cred_callback(struct rcu_head *head)
 static void
 gss_destroy_cred(struct rpc_cred *cred)
 {
+        struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
+        struct gss_cl_ctx *ctx = gss_cred->gc_ctx;
+
+        rcu_assign_pointer(gss_cred->gc_ctx, NULL);
         call_rcu(&cred->cr_rcu, gss_free_cred_callback);
+        if (ctx)
+                gss_put_ctx(ctx);
 }
 
 /*