kernel-ark/net/sunrpc/auth_generic.c
Trond Myklebust 23918b0306 SUNRPC: Fix a performance regression in the RPC authentication code
Fix a regression reported by Max Kellermann whereby kernel profiling
showed that his clients were spending 45% of their time in
rpcauth_lookup_credcache.

It turns out that although his processes had identical uid/gid/groups,
generic_match() was failing to detect this, because the task->group_info
pointers were not shared. This again lead to the creation of a huge number
of identical credentials at the RPC layer.

The regression is fixed by comparing the contents of task->group_info
if the actual pointers are not identical.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-11-20 13:17:40 -08:00

194 lines
4.7 KiB
C

/*
* Generic RPC credential
*
* Copyright (C) 2008, Trond Myklebust <Trond.Myklebust@netapp.com>
*/
#include <linux/err.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/sunrpc/auth.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/debug.h>
#include <linux/sunrpc/sched.h>
#ifdef RPC_DEBUG
# define RPCDBG_FACILITY RPCDBG_AUTH
#endif
#define RPC_MACHINE_CRED_USERID ((uid_t)0)
#define RPC_MACHINE_CRED_GROUPID ((gid_t)0)
struct generic_cred {
struct rpc_cred gc_base;
struct auth_cred acred;
};
static struct rpc_auth generic_auth;
static struct rpc_cred_cache generic_cred_cache;
static const struct rpc_credops generic_credops;
/*
* Public call interface
*/
struct rpc_cred *rpc_lookup_cred(void)
{
return rpcauth_lookupcred(&generic_auth, 0);
}
EXPORT_SYMBOL_GPL(rpc_lookup_cred);
/*
* Public call interface for looking up machine creds.
*/
struct rpc_cred *rpc_lookup_machine_cred(void)
{
struct auth_cred acred = {
.uid = RPC_MACHINE_CRED_USERID,
.gid = RPC_MACHINE_CRED_GROUPID,
.machine_cred = 1,
};
dprintk("RPC: looking up machine cred\n");
return generic_auth.au_ops->lookup_cred(&generic_auth, &acred, 0);
}
EXPORT_SYMBOL_GPL(rpc_lookup_machine_cred);
static void
generic_bind_cred(struct rpc_task *task, struct rpc_cred *cred)
{
struct rpc_auth *auth = task->tk_client->cl_auth;
struct auth_cred *acred = &container_of(cred, struct generic_cred, gc_base)->acred;
struct rpc_cred *ret;
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);
}
/*
* Lookup generic creds for current process
*/
static struct rpc_cred *
generic_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
return rpcauth_lookup_credcache(&generic_auth, acred, flags);
}
static struct rpc_cred *
generic_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
struct generic_cred *gcred;
gcred = kmalloc(sizeof(*gcred), GFP_KERNEL);
if (gcred == NULL)
return ERR_PTR(-ENOMEM);
rpcauth_init_cred(&gcred->gc_base, acred, &generic_auth, &generic_credops);
gcred->gc_base.cr_flags = 1UL << RPCAUTH_CRED_UPTODATE;
gcred->acred.uid = acred->uid;
gcred->acred.gid = acred->gid;
gcred->acred.group_info = acred->group_info;
if (gcred->acred.group_info != NULL)
get_group_info(gcred->acred.group_info);
gcred->acred.machine_cred = acred->machine_cred;
dprintk("RPC: allocated %s cred %p for uid %d gid %d\n",
gcred->acred.machine_cred ? "machine" : "generic",
gcred, acred->uid, acred->gid);
return &gcred->gc_base;
}
static void
generic_free_cred(struct rpc_cred *cred)
{
struct generic_cred *gcred = container_of(cred, struct generic_cred, gc_base);
dprintk("RPC: generic_free_cred %p\n", gcred);
if (gcred->acred.group_info != NULL)
put_group_info(gcred->acred.group_info);
kfree(gcred);
}
static void
generic_free_cred_callback(struct rcu_head *head)
{
struct rpc_cred *cred = container_of(head, struct rpc_cred, cr_rcu);
generic_free_cred(cred);
}
static void
generic_destroy_cred(struct rpc_cred *cred)
{
call_rcu(&cred->cr_rcu, generic_free_cred_callback);
}
/*
* Match credentials against current process creds.
*/
static int
generic_match(struct auth_cred *acred, struct rpc_cred *cred, int flags)
{
struct generic_cred *gcred = container_of(cred, struct generic_cred, gc_base);
int i;
if (gcred->acred.uid != acred->uid ||
gcred->acred.gid != acred->gid ||
gcred->acred.machine_cred != acred->machine_cred)
goto out_nomatch;
/* Optimisation in the case where pointers are identical... */
if (gcred->acred.group_info == acred->group_info)
goto out_match;
/* Slow path... */
if (gcred->acred.group_info->ngroups != acred->group_info->ngroups)
goto out_nomatch;
for (i = 0; i < gcred->acred.group_info->ngroups; i++) {
if (GROUP_AT(gcred->acred.group_info, i) !=
GROUP_AT(acred->group_info, i))
goto out_nomatch;
}
out_match:
return 1;
out_nomatch:
return 0;
}
void __init rpc_init_generic_auth(void)
{
spin_lock_init(&generic_cred_cache.lock);
}
void __exit rpc_destroy_generic_auth(void)
{
rpcauth_clear_credcache(&generic_cred_cache);
}
static struct rpc_cred_cache generic_cred_cache = {
{{ NULL, },},
};
static const struct rpc_authops generic_auth_ops = {
.owner = THIS_MODULE,
.au_name = "Generic",
.lookup_cred = generic_lookup_cred,
.crcreate = generic_create_cred,
};
static struct rpc_auth generic_auth = {
.au_ops = &generic_auth_ops,
.au_count = ATOMIC_INIT(0),
.au_credcache = &generic_cred_cache,
};
static const struct rpc_credops generic_credops = {
.cr_name = "Generic cred",
.crdestroy = generic_destroy_cred,
.crbind = generic_bind_cred,
.crmatch = generic_match,
};