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authorNeilBrown <neilb@suse.de>2014-07-14 11:28:20 +1000
committerTrond Myklebust <trond.myklebust@primarydata.com>2014-08-03 17:14:12 -0400
commitbd95608053b7f7813351b0defc0e3e7ef8cf2803 (patch)
treefde08b1ecc2c4aedd30a68244ca502ce5f81f0fe /net/sunrpc/auth.c
parentd51ac1a8e9b86b2d17d349bb256869cab6522787 (diff)
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>
Diffstat (limited to 'net/sunrpc/auth.c')
-rw-r--r--net/sunrpc/auth.c17
1 files changed, 15 insertions, 2 deletions
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);