sunrpc/auth: allow lockless (rcu) lookup of credential cache.
The new flag RPCAUTH_LOOKUP_RCU to credential lookup avoids locking,
does not take a reference on the returned credential, and returns
-ECHILD if a simple lookup was not possible.
The returned value can only be used within an rcu_read_lock protected
region.
The main user of this is the new rpc_lookup_cred_nonblock() which
returns a pointer to the current credential which is only rcu-safe (no
ref-count held), and might return -ECHILD if allocation was required.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/include/linux/sunrpc/auth.h b/include/linux/sunrpc/auth.h
index c683b9a..8e03007 100644
--- a/include/linux/sunrpc/auth.h
+++ b/include/linux/sunrpc/auth.h
@@ -103,6 +103,7 @@
/* Flags for rpcauth_lookupcred() */
#define RPCAUTH_LOOKUP_NEW 0x01 /* Accept an uninitialised cred */
+#define RPCAUTH_LOOKUP_RCU 0x02 /* lock-less lookup */
/*
* Client authentication ops
@@ -154,6 +155,7 @@
void rpc_destroy_authunix(void);
struct rpc_cred * rpc_lookup_cred(void);
+struct rpc_cred * rpc_lookup_cred_nonblock(void);
struct rpc_cred * rpc_lookup_machine_cred(const char *service_name);
int rpcauth_register(const struct rpc_authops *);
int rpcauth_unregister(const struct rpc_authops *);