Commit bd956080 authored by NeilBrown's avatar NeilBrown Committed by Trond Myklebust
Browse files

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: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent d51ac1a8

include/linux/sunrpc/auth.h

+2 −0
Original line number Diff line number Diff line
@@ -103,6 +103,7 @@ struct rpc_auth_create_args { 


/* 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_generic_auth(void); 
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 *);

net/sunrpc/auth.c

+15 −2
Original line number Diff line number Diff line
@@ -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;
@@ -621,9 +630,13 @@ rpcauth_lookupcred(struct rpc_auth *auth, int flags) 
	memset(&acred, 0, sizeof(acred));

	acred.uid = cred->fsuid;

	acred.gid = cred->fsgid;

	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);

	if (!(flags & RPCAUTH_LOOKUP_RCU))

		put_group_info(acred.group_info);

	return ret;

}

net/sunrpc/auth_generic.c

+6 −0
Original line number Diff line number Diff line
@@ -38,6 +38,12 @@ struct rpc_cred *rpc_lookup_cred(void) 
}

EXPORT_SYMBOL_GPL(rpc_lookup_cred);



struct rpc_cred *rpc_lookup_cred_nonblock(void)

{

	return rpcauth_lookupcred(&generic_auth, RPCAUTH_LOOKUP_RCU);

}

EXPORT_SYMBOL_GPL(rpc_lookup_cred_nonblock);



/*

 * Public call interface for looking up machine creds.

 */

net/sunrpc/auth_null.c

+2 −0
Original line number Diff line number Diff line
@@ -35,6 +35,8 @@ nul_destroy(struct rpc_auth *auth) 
static struct rpc_cred *

nul_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)

{

	if (flags & RPCAUTH_LOOKUP_RCU)

		return &null_cred;

	return get_rpccred(&null_cred);

}

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