net/sunrpc/auth.c - linux - Git at Google

 /*
  * linux/net/sunrpc/auth.c
  *
  * Generic RPC client authentication API.
  *
  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
  */

 #include <linux/types.h>
 #include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/errno.h>
 #include <linux/hash.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/spinlock.h>

 #ifdef RPC_DEBUG
 # define RPCDBG_FACILITY	RPCDBG_AUTH
 #endif

 static DEFINE_SPINLOCK(rpc_authflavor_lock);
 static const struct rpc_authops *auth_flavors[RPC_AUTH_MAXFLAVOR] = {
 	&authnull_ops,		/* AUTH_NULL */
 	&authunix_ops,		/* AUTH_UNIX */
 	NULL,			/* others can be loadable modules */
 };

 static LIST_HEAD(cred_unused);
 static unsigned long number_cred_unused;

 static u32
 pseudoflavor_to_flavor(u32 flavor) {
 	if (flavor >= RPC_AUTH_MAXFLAVOR)
 		return RPC_AUTH_GSS;
 	return flavor;
 }

 int
 rpcauth_register(const struct rpc_authops *ops)
 {
 	rpc_authflavor_t flavor;
 	int ret = -EPERM;

 	if ((flavor = ops->au_flavor) >= RPC_AUTH_MAXFLAVOR)
 		return -EINVAL;
 	spin_lock(&rpc_authflavor_lock);
 	if (auth_flavors[flavor] == NULL) {
 		auth_flavors[flavor] = ops;
 		ret = 0;
 	}
 	spin_unlock(&rpc_authflavor_lock);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(rpcauth_register);

 int
 rpcauth_unregister(const struct rpc_authops *ops)
 {
 	rpc_authflavor_t flavor;
 	int ret = -EPERM;

 	if ((flavor = ops->au_flavor) >= RPC_AUTH_MAXFLAVOR)
 		return -EINVAL;
 	spin_lock(&rpc_authflavor_lock);
 	if (auth_flavors[flavor] == ops) {
 		auth_flavors[flavor] = NULL;
 		ret = 0;
 	}
 	spin_unlock(&rpc_authflavor_lock);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(rpcauth_unregister);

 struct rpc_auth *
 rpcauth_create(rpc_authflavor_t pseudoflavor, struct rpc_clnt *clnt)
 {
 	struct rpc_auth		*auth;
 	const struct rpc_authops *ops;
 	u32			flavor = pseudoflavor_to_flavor(pseudoflavor);

 	auth = ERR_PTR(-EINVAL);
 	if (flavor >= RPC_AUTH_MAXFLAVOR)
 		goto out;

 #ifdef CONFIG_KMOD
 	if ((ops = auth_flavors[flavor]) == NULL)
 		request_module("rpc-auth-%u", flavor);
 #endif
 	spin_lock(&rpc_authflavor_lock);
 	ops = auth_flavors[flavor];
 	if (ops == NULL || !try_module_get(ops->owner)) {
 		spin_unlock(&rpc_authflavor_lock);
 		goto out;
 	}
 	spin_unlock(&rpc_authflavor_lock);
 	auth = ops->create(clnt, pseudoflavor);
 	module_put(ops->owner);
 	if (IS_ERR(auth))
 		return auth;
 	if (clnt->cl_auth)
 		rpcauth_release(clnt->cl_auth);
 	clnt->cl_auth = auth;

 out:
 	return auth;
 }
 EXPORT_SYMBOL_GPL(rpcauth_create);

 void
 rpcauth_release(struct rpc_auth *auth)
 {
 	if (!atomic_dec_and_test(&auth->au_count))
 		return;
 	auth->au_ops->destroy(auth);
 }

 static DEFINE_SPINLOCK(rpc_credcache_lock);

 static void
 rpcauth_unhash_cred_locked(struct rpc_cred *cred)
 {
 	hlist_del_rcu(&cred->cr_hash);
 	smp_mb__before_clear_bit();
 	clear_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags);
 }

 static void
 rpcauth_unhash_cred(struct rpc_cred *cred)
 {
 	spinlock_t *cache_lock;

 	cache_lock = &cred->cr_auth->au_credcache->lock;
 	spin_lock(cache_lock);
 	if (atomic_read(&cred->cr_count) == 0)
 		rpcauth_unhash_cred_locked(cred);
 	spin_unlock(cache_lock);
 }

 /*
  * Initialize RPC credential cache
  */
 int
 rpcauth_init_credcache(struct rpc_auth *auth)
 {
 	struct rpc_cred_cache *new;
 	int i;

 	new = kmalloc(sizeof(*new), GFP_KERNEL);
 	if (!new)
 		return -ENOMEM;
 	for (i = 0; i < RPC_CREDCACHE_NR; i++)
 		INIT_HLIST_HEAD(&new->hashtable[i]);
 	spin_lock_init(&new->lock);
 	auth->au_credcache = new;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(rpcauth_init_credcache);

 /*
  * Destroy a list of credentials
  */
 static inline
 void rpcauth_destroy_credlist(struct list_head *head)
 {
 	struct rpc_cred *cred;

 	while (!list_empty(head)) {
 		cred = list_entry(head->next, struct rpc_cred, cr_lru);
 		list_del_init(&cred->cr_lru);
 		put_rpccred(cred);
 	}
 }

 /*
  * Clear the RPC credential cache, and delete those credentials
  * that are not referenced.
  */
 void
 rpcauth_clear_credcache(struct rpc_cred_cache *cache)
 {
 	LIST_HEAD(free);
 	struct hlist_head *head;
 	struct rpc_cred	*cred;
 	int		i;

 	spin_lock(&rpc_credcache_lock);
 	spin_lock(&cache->lock);
 	for (i = 0; i < RPC_CREDCACHE_NR; i++) {
 		head = &cache->hashtable[i];
 		while (!hlist_empty(head)) {
 			cred = hlist_entry(head->first, struct rpc_cred, cr_hash);
 			get_rpccred(cred);
 			if (!list_empty(&cred->cr_lru)) {
 				list_del(&cred->cr_lru);
 				number_cred_unused--;
 			}
 			list_add_tail(&cred->cr_lru, &free);
 			rpcauth_unhash_cred_locked(cred);
 		}
 	}
 	spin_unlock(&cache->lock);
 	spin_unlock(&rpc_credcache_lock);
 	rpcauth_destroy_credlist(&free);
 }

 /*
  * Destroy the RPC credential cache
  */
 void
 rpcauth_destroy_credcache(struct rpc_auth *auth)
 {
 	struct rpc_cred_cache *cache = auth->au_credcache;

 	if (cache) {
 		auth->au_credcache = NULL;
 		rpcauth_clear_credcache(cache);
 		kfree(cache);
 	}
 }
 EXPORT_SYMBOL_GPL(rpcauth_destroy_credcache);

 /*
  * Remove stale credentials. Avoid sleeping inside the loop.
  */
 static int
 rpcauth_prune_expired(struct list_head *free, int nr_to_scan)
 {
 	spinlock_t *cache_lock;
 	struct rpc_cred *cred;

 	while (!list_empty(&cred_unused)) {
 		cred = list_entry(cred_unused.next, struct rpc_cred, cr_lru);
 		list_del_init(&cred->cr_lru);
 		number_cred_unused--;
 		if (atomic_read(&cred->cr_count) != 0)
 			continue;
 		cache_lock = &cred->cr_auth->au_credcache->lock;
 		spin_lock(cache_lock);
 		if (atomic_read(&cred->cr_count) == 0) {
 			get_rpccred(cred);
 			list_add_tail(&cred->cr_lru, free);
 			rpcauth_unhash_cred_locked(cred);
 			nr_to_scan--;
 		}
 		spin_unlock(cache_lock);
 		if (nr_to_scan == 0)
 			break;
 	}
 	return nr_to_scan;
 }

 /*
  * Run memory cache shrinker.
  */
 static int
 rpcauth_cache_shrinker(int nr_to_scan, gfp_t gfp_mask)
 {
 	LIST_HEAD(free);
 	int res;

 	if (list_empty(&cred_unused))
 		return 0;
 	spin_lock(&rpc_credcache_lock);
 	nr_to_scan = rpcauth_prune_expired(&free, nr_to_scan);
 	res = (number_cred_unused / 100) * sysctl_vfs_cache_pressure;
 	spin_unlock(&rpc_credcache_lock);
 	rpcauth_destroy_credlist(&free);
 	return res;
 }

 /*
  * Look up a process' credentials in the authentication cache
  */
 struct rpc_cred *
 rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
 		int flags)
 {
 	LIST_HEAD(free);
 	struct rpc_cred_cache *cache = auth->au_credcache;
 	struct hlist_node *pos;
 	struct rpc_cred	*cred = NULL,
 			*entry, *new;
 	unsigned int nr;

 	nr = hash_long(acred->uid, RPC_CREDCACHE_HASHBITS);

 	rcu_read_lock();
 	hlist_for_each_entry_rcu(entry, pos, &cache->hashtable[nr], cr_hash) {
 		if (!entry->cr_ops->crmatch(acred, entry, flags))
 			continue;
 		spin_lock(&cache->lock);
 		if (test_bit(RPCAUTH_CRED_HASHED, &entry->cr_flags) == 0) {
 			spin_unlock(&cache->lock);
 			continue;
 		}
 		cred = get_rpccred(entry);
 		spin_unlock(&cache->lock);
 		break;
 	}
 	rcu_read_unlock();

 	if (cred != NULL)
 		goto found;

 	new = auth->au_ops->crcreate(auth, acred, flags);
 	if (IS_ERR(new)) {
 		cred = new;
 		goto out;
 	}

 	spin_lock(&cache->lock);
 	hlist_for_each_entry(entry, pos, &cache->hashtable[nr], cr_hash) {
 		if (!entry->cr_ops->crmatch(acred, entry, flags))
 			continue;
 		cred = get_rpccred(entry);
 		break;
 	}
 	if (cred == NULL) {
 		cred = new;
 		set_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags);
 		hlist_add_head_rcu(&cred->cr_hash, &cache->hashtable[nr]);
 	} else
 		list_add_tail(&new->cr_lru, &free);
 	spin_unlock(&cache->lock);
 found:
 	if (test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags)
 			&& cred->cr_ops->cr_init != NULL
 			&& !(flags & RPCAUTH_LOOKUP_NEW)) {
 		int res = cred->cr_ops->cr_init(auth, cred);
 		if (res < 0) {
 			put_rpccred(cred);
 			cred = ERR_PTR(res);
 		}
 	}
 	rpcauth_destroy_credlist(&free);
 out:
 	return cred;
 }
 EXPORT_SYMBOL_GPL(rpcauth_lookup_credcache);

 struct rpc_cred *
 rpcauth_lookupcred(struct rpc_auth *auth, int flags)
 {
 	struct auth_cred acred = {
 		.uid = current->fsuid,
 		.gid = current->fsgid,
 		.group_info = current->group_info,
 	};
 	struct rpc_cred *ret;

 	dprintk("RPC:       looking up %s cred\n",
 		auth->au_ops->au_name);
 	get_group_info(acred.group_info);
 	ret = auth->au_ops->lookup_cred(auth, &acred, flags);
 	put_group_info(acred.group_info);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(rpcauth_lookupcred);

 void
 rpcauth_init_cred(struct rpc_cred *cred, const struct auth_cred *acred,
 		  struct rpc_auth *auth, const struct rpc_credops *ops)
 {
 	INIT_HLIST_NODE(&cred->cr_hash);
 	INIT_LIST_HEAD(&cred->cr_lru);
 	atomic_set(&cred->cr_count, 1);
 	cred->cr_auth = auth;
 	cred->cr_ops = ops;
 	cred->cr_expire = jiffies;
 #ifdef RPC_DEBUG
 	cred->cr_magic = RPCAUTH_CRED_MAGIC;
 #endif
 	cred->cr_uid = acred->uid;
 }
 EXPORT_SYMBOL_GPL(rpcauth_init_cred);

 static void
 rpcauth_generic_bind_cred(struct rpc_task *task, struct rpc_cred *cred)
 {
 	task->tk_msg.rpc_cred = get_rpccred(cred);
 	dprintk("RPC: %5u holding %s cred %p\n", task->tk_pid,
 			cred->cr_auth->au_ops->au_name, cred);
 }

 static void
 rpcauth_bind_root_cred(struct rpc_task *task)
 {
 	struct rpc_auth *auth = task->tk_client->cl_auth;
 	struct auth_cred acred = {
 		.uid = 0,
 		.gid = 0,
 	};
 	struct rpc_cred *ret;

 	dprintk("RPC: %5u looking up %s cred\n",
 		task->tk_pid, task->tk_client->cl_auth->au_ops->au_name);
 	ret = auth->au_ops->lookup_cred(auth, &acred, 0);
 	if (!IS_ERR(ret))
 		task->tk_msg.rpc_cred = ret;
 	else
 		task->tk_status = PTR_ERR(ret);
 }

 static void
 rpcauth_bind_new_cred(struct rpc_task *task)
 {
 	struct rpc_auth *auth = task->tk_client->cl_auth;
 	struct rpc_cred *ret;

 	dprintk("RPC: %5u looking up %s cred\n",
 		task->tk_pid, auth->au_ops->au_name);
 	ret = rpcauth_lookupcred(auth, 0);
 	if (!IS_ERR(ret))
 		task->tk_msg.rpc_cred = ret;
 	else
 		task->tk_status = PTR_ERR(ret);
 }

 void
 rpcauth_bindcred(struct rpc_task *task, struct rpc_cred *cred, int flags)
 {
 	if (cred != NULL)
 		rpcauth_generic_bind_cred(task, cred);
 	else if (flags & RPC_TASK_ROOTCREDS)
 		rpcauth_bind_root_cred(task);
 	else
 		rpcauth_bind_new_cred(task);
 }

 void
 put_rpccred(struct rpc_cred *cred)
 {
 	/* Fast path for unhashed credentials */
 	if (test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags) != 0)
 		goto need_lock;

 	if (!atomic_dec_and_test(&cred->cr_count))
 		return;
 	goto out_destroy;
 need_lock:
 	if (!atomic_dec_and_lock(&cred->cr_count, &rpc_credcache_lock))
 		return;
 	if (!list_empty(&cred->cr_lru)) {
 		number_cred_unused--;
 		list_del_init(&cred->cr_lru);
 	}
 	if (test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) == 0)
 		rpcauth_unhash_cred(cred);
 	else if (test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags) != 0) {
 		cred->cr_expire = jiffies;
 		list_add_tail(&cred->cr_lru, &cred_unused);
 		number_cred_unused++;
 		spin_unlock(&rpc_credcache_lock);
 		return;
 	}
 	spin_unlock(&rpc_credcache_lock);
 out_destroy:
 	cred->cr_ops->crdestroy(cred);
 }
 EXPORT_SYMBOL_GPL(put_rpccred);

 void
 rpcauth_unbindcred(struct rpc_task *task)
 {
 	struct rpc_cred	*cred = task->tk_msg.rpc_cred;

 	dprintk("RPC: %5u releasing %s cred %p\n",
 		task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

 	put_rpccred(cred);
 	task->tk_msg.rpc_cred = NULL;
 }

 __be32 *
 rpcauth_marshcred(struct rpc_task *task, __be32 *p)
 {
 	struct rpc_cred	*cred = task->tk_msg.rpc_cred;

 	dprintk("RPC: %5u marshaling %s cred %p\n",
 		task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

 	return cred->cr_ops->crmarshal(task, p);
 }

 __be32 *
 rpcauth_checkverf(struct rpc_task *task, __be32 *p)
 {
 	struct rpc_cred	*cred = task->tk_msg.rpc_cred;

 	dprintk("RPC: %5u validating %s cred %p\n",
 		task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

 	return cred->cr_ops->crvalidate(task, p);
 }

 int
 rpcauth_wrap_req(struct rpc_task *task, kxdrproc_t encode, void *rqstp,
 		__be32 *data, void *obj)
 {
 	struct rpc_cred *cred = task->tk_msg.rpc_cred;

 	dprintk("RPC: %5u using %s cred %p to wrap rpc data\n",
 			task->tk_pid, cred->cr_ops->cr_name, cred);
 	if (cred->cr_ops->crwrap_req)
 		return cred->cr_ops->crwrap_req(task, encode, rqstp, data, obj);
 	/* By default, we encode the arguments normally. */
 	return rpc_call_xdrproc(encode, rqstp, data, obj);
 }

 int
 rpcauth_unwrap_resp(struct rpc_task *task, kxdrproc_t decode, void *rqstp,
 		__be32 *data, void *obj)
 {
 	struct rpc_cred *cred = task->tk_msg.rpc_cred;

 	dprintk("RPC: %5u using %s cred %p to unwrap rpc data\n",
 			task->tk_pid, cred->cr_ops->cr_name, cred);
 	if (cred->cr_ops->crunwrap_resp)
 		return cred->cr_ops->crunwrap_resp(task, decode, rqstp,
 						   data, obj);
 	/* By default, we decode the arguments normally. */
 	return rpc_call_xdrproc(decode, rqstp, data, obj);
 }

 int
 rpcauth_refreshcred(struct rpc_task *task)
 {
 	struct rpc_cred	*cred = task->tk_msg.rpc_cred;
 	int err;

 	dprintk("RPC: %5u refreshing %s cred %p\n",
 		task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

 	err = cred->cr_ops->crrefresh(task);
 	if (err < 0)
 		task->tk_status = err;
 	return err;
 }

 void
 rpcauth_invalcred(struct rpc_task *task)
 {
 	struct rpc_cred *cred = task->tk_msg.rpc_cred;

 	dprintk("RPC: %5u invalidating %s cred %p\n",
 		task->tk_pid, cred->cr_auth->au_ops->au_name, cred);
 	if (cred)
 		clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
 }

 int
 rpcauth_uptodatecred(struct rpc_task *task)
 {
 	struct rpc_cred *cred = task->tk_msg.rpc_cred;

 	return cred == NULL ||
 		test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) != 0;
 }

 static struct shrinker rpc_cred_shrinker = {
 	.shrink = rpcauth_cache_shrinker,
 	.seeks = DEFAULT_SEEKS,
 };

 void __init rpcauth_init_module(void)
 {
 	rpc_init_authunix();
 	rpc_init_generic_auth();
 	register_shrinker(&rpc_cred_shrinker);
 }

 void __exit rpcauth_remove_module(void)
 {
 	unregister_shrinker(&rpc_cred_shrinker);
 }
	/*
	* linux/net/sunrpc/auth.c
	*
	* Generic RPC client authentication API.
	*
	* Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
	*/

	#include <linux/types.h>
	#include <linux/sched.h>
	#include <linux/module.h>
	#include <linux/slab.h>
	#include <linux/errno.h>
	#include <linux/hash.h>
	#include <linux/sunrpc/clnt.h>
	#include <linux/spinlock.h>

	#ifdef RPC_DEBUG
	# define RPCDBG_FACILITY RPCDBG_AUTH
	#endif

	static DEFINE_SPINLOCK(rpc_authflavor_lock);
	static const struct rpc_authops *auth_flavors[RPC_AUTH_MAXFLAVOR] = {
	&authnull_ops, /* AUTH_NULL */
	&authunix_ops, /* AUTH_UNIX */
	NULL, /* others can be loadable modules */
	};

	static LIST_HEAD(cred_unused);
	static unsigned long number_cred_unused;

	static u32
	pseudoflavor_to_flavor(u32 flavor) {
	if (flavor >= RPC_AUTH_MAXFLAVOR)
	return RPC_AUTH_GSS;
	return flavor;
	}

	int
	rpcauth_register(const struct rpc_authops *ops)
	{
	rpc_authflavor_t flavor;
	int ret = -EPERM;

	if ((flavor = ops->au_flavor) >= RPC_AUTH_MAXFLAVOR)
	return -EINVAL;
	spin_lock(&rpc_authflavor_lock);
	if (auth_flavors[flavor] == NULL) {
	auth_flavors[flavor] = ops;
	ret = 0;
	}
	spin_unlock(&rpc_authflavor_lock);
	return ret;
	}
	EXPORT_SYMBOL_GPL(rpcauth_register);

	int
	rpcauth_unregister(const struct rpc_authops *ops)
	{
	rpc_authflavor_t flavor;
	int ret = -EPERM;

	if ((flavor = ops->au_flavor) >= RPC_AUTH_MAXFLAVOR)
	return -EINVAL;
	spin_lock(&rpc_authflavor_lock);
	if (auth_flavors[flavor] == ops) {
	auth_flavors[flavor] = NULL;
	ret = 0;
	}
	spin_unlock(&rpc_authflavor_lock);
	return ret;
	}
	EXPORT_SYMBOL_GPL(rpcauth_unregister);

	struct rpc_auth *
	rpcauth_create(rpc_authflavor_t pseudoflavor, struct rpc_clnt *clnt)
	{
	struct rpc_auth *auth;
	const struct rpc_authops *ops;
	u32 flavor = pseudoflavor_to_flavor(pseudoflavor);

	auth = ERR_PTR(-EINVAL);
	if (flavor >= RPC_AUTH_MAXFLAVOR)
	goto out;

	#ifdef CONFIG_KMOD
	if ((ops = auth_flavors[flavor]) == NULL)
	request_module("rpc-auth-%u", flavor);
	#endif
	spin_lock(&rpc_authflavor_lock);
	ops = auth_flavors[flavor];
	if (ops == NULL \|\| !try_module_get(ops->owner)) {
	spin_unlock(&rpc_authflavor_lock);
	goto out;
	}
	spin_unlock(&rpc_authflavor_lock);
	auth = ops->create(clnt, pseudoflavor);
	module_put(ops->owner);
	if (IS_ERR(auth))
	return auth;
	if (clnt->cl_auth)
	rpcauth_release(clnt->cl_auth);
	clnt->cl_auth = auth;

	out:
	return auth;
	}
	EXPORT_SYMBOL_GPL(rpcauth_create);

	void
	rpcauth_release(struct rpc_auth *auth)
	{
	if (!atomic_dec_and_test(&auth->au_count))
	return;
	auth->au_ops->destroy(auth);
	}

	static DEFINE_SPINLOCK(rpc_credcache_lock);

	static void
	rpcauth_unhash_cred_locked(struct rpc_cred *cred)
	{
	hlist_del_rcu(&cred->cr_hash);
	smp_mb__before_clear_bit();
	clear_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags);
	}

	static void
	rpcauth_unhash_cred(struct rpc_cred *cred)
	{
	spinlock_t *cache_lock;

	cache_lock = &cred->cr_auth->au_credcache->lock;
	spin_lock(cache_lock);
	if (atomic_read(&cred->cr_count) == 0)
	rpcauth_unhash_cred_locked(cred);
	spin_unlock(cache_lock);
	}

	/*
	* Initialize RPC credential cache
	*/
	int
	rpcauth_init_credcache(struct rpc_auth *auth)
	{
	struct rpc_cred_cache *new;
	int i;

	new = kmalloc(sizeof(*new), GFP_KERNEL);
	if (!new)
	return -ENOMEM;
	for (i = 0; i < RPC_CREDCACHE_NR; i++)
	INIT_HLIST_HEAD(&new->hashtable[i]);
	spin_lock_init(&new->lock);
	auth->au_credcache = new;
	return 0;
	}
	EXPORT_SYMBOL_GPL(rpcauth_init_credcache);

	/*
	* Destroy a list of credentials
	*/
	static inline
	void rpcauth_destroy_credlist(struct list_head *head)
	{
	struct rpc_cred *cred;

	while (!list_empty(head)) {
	cred = list_entry(head->next, struct rpc_cred, cr_lru);
	list_del_init(&cred->cr_lru);
	put_rpccred(cred);
	}
	}

	/*
	* Clear the RPC credential cache, and delete those credentials
	* that are not referenced.
	*/
	void
	rpcauth_clear_credcache(struct rpc_cred_cache *cache)
	{
	LIST_HEAD(free);
	struct hlist_head *head;
	struct rpc_cred *cred;
	int i;

	spin_lock(&rpc_credcache_lock);
	spin_lock(&cache->lock);
	for (i = 0; i < RPC_CREDCACHE_NR; i++) {
	head = &cache->hashtable[i];
	while (!hlist_empty(head)) {
	cred = hlist_entry(head->first, struct rpc_cred, cr_hash);
	get_rpccred(cred);
	if (!list_empty(&cred->cr_lru)) {
	list_del(&cred->cr_lru);
	number_cred_unused--;
	}
	list_add_tail(&cred->cr_lru, &free);
	rpcauth_unhash_cred_locked(cred);
	}
	}
	spin_unlock(&cache->lock);
	spin_unlock(&rpc_credcache_lock);
	rpcauth_destroy_credlist(&free);
	}

	/*
	* Destroy the RPC credential cache
	*/
	void
	rpcauth_destroy_credcache(struct rpc_auth *auth)
	{
	struct rpc_cred_cache *cache = auth->au_credcache;

	if (cache) {
	auth->au_credcache = NULL;
	rpcauth_clear_credcache(cache);
	kfree(cache);
	}
	}
	EXPORT_SYMBOL_GPL(rpcauth_destroy_credcache);

	/*
	* Remove stale credentials. Avoid sleeping inside the loop.
	*/
	static int
	rpcauth_prune_expired(struct list_head *free, int nr_to_scan)
	{
	spinlock_t *cache_lock;
	struct rpc_cred *cred;

	while (!list_empty(&cred_unused)) {
	cred = list_entry(cred_unused.next, struct rpc_cred, cr_lru);
	list_del_init(&cred->cr_lru);
	number_cred_unused--;
	if (atomic_read(&cred->cr_count) != 0)
	continue;
	cache_lock = &cred->cr_auth->au_credcache->lock;
	spin_lock(cache_lock);
	if (atomic_read(&cred->cr_count) == 0) {
	get_rpccred(cred);
	list_add_tail(&cred->cr_lru, free);
	rpcauth_unhash_cred_locked(cred);
	nr_to_scan--;
	}
	spin_unlock(cache_lock);
	if (nr_to_scan == 0)
	break;
	}
	return nr_to_scan;
	}

	/*
	* Run memory cache shrinker.
	*/
	static int
	rpcauth_cache_shrinker(int nr_to_scan, gfp_t gfp_mask)
	{
	LIST_HEAD(free);
	int res;

	if (list_empty(&cred_unused))
	return 0;
	spin_lock(&rpc_credcache_lock);
	nr_to_scan = rpcauth_prune_expired(&free, nr_to_scan);
	res = (number_cred_unused / 100) * sysctl_vfs_cache_pressure;
	spin_unlock(&rpc_credcache_lock);
	rpcauth_destroy_credlist(&free);
	return res;
	}

	/*
	* Look up a process' credentials in the authentication cache
	*/
	struct rpc_cred *
	rpcauth_lookup_credcache(struct rpc_auth auth, struct auth_cred acred,
	int flags)
	{
	LIST_HEAD(free);
	struct rpc_cred_cache *cache = auth->au_credcache;
	struct hlist_node *pos;
	struct rpc_cred *cred = NULL,
	entry, new;
	unsigned int nr;

	nr = hash_long(acred->uid, RPC_CREDCACHE_HASHBITS);

	rcu_read_lock();
	hlist_for_each_entry_rcu(entry, pos, &cache->hashtable[nr], cr_hash) {
	if (!entry->cr_ops->crmatch(acred, entry, flags))
	continue;
	spin_lock(&cache->lock);
	if (test_bit(RPCAUTH_CRED_HASHED, &entry->cr_flags) == 0) {
	spin_unlock(&cache->lock);
	continue;
	}
	cred = get_rpccred(entry);
	spin_unlock(&cache->lock);
	break;
	}
	rcu_read_unlock();

	if (cred != NULL)
	goto found;

	new = auth->au_ops->crcreate(auth, acred, flags);
	if (IS_ERR(new)) {
	cred = new;
	goto out;
	}

	spin_lock(&cache->lock);
	hlist_for_each_entry(entry, pos, &cache->hashtable[nr], cr_hash) {
	if (!entry->cr_ops->crmatch(acred, entry, flags))
	continue;
	cred = get_rpccred(entry);
	break;
	}
	if (cred == NULL) {
	cred = new;
	set_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags);
	hlist_add_head_rcu(&cred->cr_hash, &cache->hashtable[nr]);
	} else
	list_add_tail(&new->cr_lru, &free);
	spin_unlock(&cache->lock);
	found:
	if (test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags)
	&& cred->cr_ops->cr_init != NULL
	&& !(flags & RPCAUTH_LOOKUP_NEW)) {
	int res = cred->cr_ops->cr_init(auth, cred);
	if (res < 0) {
	put_rpccred(cred);
	cred = ERR_PTR(res);
	}
	}
	rpcauth_destroy_credlist(&free);
	out:
	return cred;
	}
	EXPORT_SYMBOL_GPL(rpcauth_lookup_credcache);

	struct rpc_cred *
	rpcauth_lookupcred(struct rpc_auth *auth, int flags)
	{
	struct auth_cred acred = {
	.uid = current->fsuid,
	.gid = current->fsgid,
	.group_info = current->group_info,
	};
	struct rpc_cred *ret;

	dprintk("RPC: looking up %s cred\n",
	auth->au_ops->au_name);
	get_group_info(acred.group_info);
	ret = auth->au_ops->lookup_cred(auth, &acred, flags);
	put_group_info(acred.group_info);
	return ret;
	}
	EXPORT_SYMBOL_GPL(rpcauth_lookupcred);

	void
	rpcauth_init_cred(struct rpc_cred cred, const struct auth_cred acred,
	struct rpc_auth auth, const struct rpc_credops ops)
	{
	INIT_HLIST_NODE(&cred->cr_hash);
	INIT_LIST_HEAD(&cred->cr_lru);
	atomic_set(&cred->cr_count, 1);
	cred->cr_auth = auth;
	cred->cr_ops = ops;
	cred->cr_expire = jiffies;
	#ifdef RPC_DEBUG
	cred->cr_magic = RPCAUTH_CRED_MAGIC;
	#endif
	cred->cr_uid = acred->uid;
	}
	EXPORT_SYMBOL_GPL(rpcauth_init_cred);

	static void
	rpcauth_generic_bind_cred(struct rpc_task task, struct rpc_cred cred)
	{
	task->tk_msg.rpc_cred = get_rpccred(cred);
	dprintk("RPC: %5u holding %s cred %p\n", task->tk_pid,
	cred->cr_auth->au_ops->au_name, cred);
	}

	static void
	rpcauth_bind_root_cred(struct rpc_task *task)
	{
	struct rpc_auth *auth = task->tk_client->cl_auth;
	struct auth_cred acred = {
	.uid = 0,
	.gid = 0,
	};
	struct rpc_cred *ret;

	dprintk("RPC: %5u looking up %s cred\n",
	task->tk_pid, task->tk_client->cl_auth->au_ops->au_name);
	ret = auth->au_ops->lookup_cred(auth, &acred, 0);
	if (!IS_ERR(ret))
	task->tk_msg.rpc_cred = ret;
	else
	task->tk_status = PTR_ERR(ret);
	}

	static void
	rpcauth_bind_new_cred(struct rpc_task *task)
	{
	struct rpc_auth *auth = task->tk_client->cl_auth;
	struct rpc_cred *ret;

	dprintk("RPC: %5u looking up %s cred\n",
	task->tk_pid, auth->au_ops->au_name);
	ret = rpcauth_lookupcred(auth, 0);
	if (!IS_ERR(ret))
	task->tk_msg.rpc_cred = ret;
	else
	task->tk_status = PTR_ERR(ret);
	}

	void
	rpcauth_bindcred(struct rpc_task task, struct rpc_cred cred, int flags)
	{
	if (cred != NULL)
	rpcauth_generic_bind_cred(task, cred);
	else if (flags & RPC_TASK_ROOTCREDS)
	rpcauth_bind_root_cred(task);
	else
	rpcauth_bind_new_cred(task);
	}

	void
	put_rpccred(struct rpc_cred *cred)
	{
	/* Fast path for unhashed credentials */
	if (test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags) != 0)
	goto need_lock;

	if (!atomic_dec_and_test(&cred->cr_count))
	return;
	goto out_destroy;
	need_lock:
	if (!atomic_dec_and_lock(&cred->cr_count, &rpc_credcache_lock))
	return;
	if (!list_empty(&cred->cr_lru)) {
	number_cred_unused--;
	list_del_init(&cred->cr_lru);
	}
	if (test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) == 0)
	rpcauth_unhash_cred(cred);
	else if (test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags) != 0) {
	cred->cr_expire = jiffies;
	list_add_tail(&cred->cr_lru, &cred_unused);
	number_cred_unused++;
	spin_unlock(&rpc_credcache_lock);
	return;
	}
	spin_unlock(&rpc_credcache_lock);
	out_destroy:
	cred->cr_ops->crdestroy(cred);
	}
	EXPORT_SYMBOL_GPL(put_rpccred);

	void
	rpcauth_unbindcred(struct rpc_task *task)
	{
	struct rpc_cred *cred = task->tk_msg.rpc_cred;

	dprintk("RPC: %5u releasing %s cred %p\n",
	task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

	put_rpccred(cred);
	task->tk_msg.rpc_cred = NULL;
	}

	__be32 *
	rpcauth_marshcred(struct rpc_task task, __be32 p)
	{
	struct rpc_cred *cred = task->tk_msg.rpc_cred;

	dprintk("RPC: %5u marshaling %s cred %p\n",
	task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

	return cred->cr_ops->crmarshal(task, p);
	}

	__be32 *
	rpcauth_checkverf(struct rpc_task task, __be32 p)
	{
	struct rpc_cred *cred = task->tk_msg.rpc_cred;

	dprintk("RPC: %5u validating %s cred %p\n",
	task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

	return cred->cr_ops->crvalidate(task, p);
	}

	int
	rpcauth_wrap_req(struct rpc_task task, kxdrproc_t encode, void rqstp,
	__be32 data, void obj)
	{
	struct rpc_cred *cred = task->tk_msg.rpc_cred;

	dprintk("RPC: %5u using %s cred %p to wrap rpc data\n",
	task->tk_pid, cred->cr_ops->cr_name, cred);
	if (cred->cr_ops->crwrap_req)
	return cred->cr_ops->crwrap_req(task, encode, rqstp, data, obj);
	/* By default, we encode the arguments normally. */
	return rpc_call_xdrproc(encode, rqstp, data, obj);
	}

	int
	rpcauth_unwrap_resp(struct rpc_task task, kxdrproc_t decode, void rqstp,
	__be32 data, void obj)
	{
	struct rpc_cred *cred = task->tk_msg.rpc_cred;

	dprintk("RPC: %5u using %s cred %p to unwrap rpc data\n",
	task->tk_pid, cred->cr_ops->cr_name, cred);
	if (cred->cr_ops->crunwrap_resp)
	return cred->cr_ops->crunwrap_resp(task, decode, rqstp,
	data, obj);
	/* By default, we decode the arguments normally. */
	return rpc_call_xdrproc(decode, rqstp, data, obj);
	}

	int
	rpcauth_refreshcred(struct rpc_task *task)
	{
	struct rpc_cred *cred = task->tk_msg.rpc_cred;
	int err;

	dprintk("RPC: %5u refreshing %s cred %p\n",
	task->tk_pid, cred->cr_auth->au_ops->au_name, cred);

	err = cred->cr_ops->crrefresh(task);
	if (err < 0)
	task->tk_status = err;
	return err;
	}

	void
	rpcauth_invalcred(struct rpc_task *task)
	{
	struct rpc_cred *cred = task->tk_msg.rpc_cred;

	dprintk("RPC: %5u invalidating %s cred %p\n",
	task->tk_pid, cred->cr_auth->au_ops->au_name, cred);
	if (cred)
	clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
	}

	int
	rpcauth_uptodatecred(struct rpc_task *task)
	{
	struct rpc_cred *cred = task->tk_msg.rpc_cred;

	return cred == NULL \|\|
	test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) != 0;
	}

	static struct shrinker rpc_cred_shrinker = {
	.shrink = rpcauth_cache_shrinker,
	.seeks = DEFAULT_SEEKS,
	};

	void __init rpcauth_init_module(void)
	{
	rpc_init_authunix();
	rpc_init_generic_auth();
	register_shrinker(&rpc_cred_shrinker);
	}

	void __exit rpcauth_remove_module(void)
	{
	unregister_shrinker(&rpc_cred_shrinker);
	}