SUNRPC: Convert gss_ctx_lock to an RCU lock

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

diff --git a/include/linux/sunrpc/auth_gss.h b/include/linux/sunrpc/auth_gss.h
index 0bd1d06..67658e1 100644 (file)
--- 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 8653a92..15da6f8 100644 (file)
--- 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);
 }
 
 /*