From bd95608053b7f7813351b0defc0e3e7ef8cf2803 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 14 Jul 2014 11:28:20 +1000 Subject: 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 Signed-off-by: Trond Myklebust --- net/sunrpc/auth.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) (limited to 'net/sunrpc/auth.c') diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c index 360decdddc78..24fcbd23ae6c 100644 --- a/net/sunrpc/auth.c +++ b/net/sunrpc/auth.c @@ -557,6 +557,12 @@ rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred, hlist_for_each_entry_rcu(entry, &cache->hashtable[nr], cr_hash) { if (!entry->cr_ops->crmatch(acred, entry, flags)) continue; + if (flags & RPCAUTH_LOOKUP_RCU) { + if (test_bit(RPCAUTH_CRED_HASHED, &entry->cr_flags) && + !test_bit(RPCAUTH_CRED_NEW, &entry->cr_flags)) + cred = entry; + break; + } spin_lock(&cache->lock); if (test_bit(RPCAUTH_CRED_HASHED, &entry->cr_flags) == 0) { spin_unlock(&cache->lock); @@ -571,6 +577,9 @@ rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred, if (cred != NULL) goto found; + if (flags & RPCAUTH_LOOKUP_RCU) + return ERR_PTR(-ECHILD); + new = auth->au_ops->crcreate(auth, acred, flags); if (IS_ERR(new)) { cred = new; @@ -621,10 +630,14 @@ rpcauth_lookupcred(struct rpc_auth *auth, int flags) memset(&acred, 0, sizeof(acred)); acred.uid = cred->fsuid; acred.gid = cred->fsgid; - acred.group_info = get_group_info(((struct cred *)cred)->group_info); + if (flags & RPCAUTH_LOOKUP_RCU) + acred.group_info = rcu_dereference(cred->group_info); + else + acred.group_info = get_group_info(((struct cred *)cred)->group_info); ret = auth->au_ops->lookup_cred(auth, &acred, flags); - put_group_info(acred.group_info); + if (!(flags & RPCAUTH_LOOKUP_RCU)) + put_group_info(acred.group_info); return ret; } EXPORT_SYMBOL_GPL(rpcauth_lookupcred); -- cgit v1.2.3