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From: Trond Myklebust <trondmy@gmail.com>
To: "J . Bruce Fields" <bfields@fieldses.org>
Cc: linux-nfs@vger.kernel.org
Subject: [PATCH 01/15] SUNRPC: Remove the server 'authtab_lock' and just use RCU
Date: Mon,  1 Oct 2018 10:41:43 -0400	[thread overview]
Message-ID: <20181001144157.3515-2-trond.myklebust@hammerspace.com> (raw)
In-Reply-To: <20181001144157.3515-1-trond.myklebust@hammerspace.com>

Module removal is RCU safe by design, so we really have no need to
lock the 'authtab[]' array.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 net/sunrpc/svcauth.c | 52 +++++++++++++++++++++++++++++---------------
 1 file changed, 34 insertions(+), 18 deletions(-)

diff --git a/net/sunrpc/svcauth.c b/net/sunrpc/svcauth.c
index bb8db3cb8032..f83443856cd1 100644
--- a/net/sunrpc/svcauth.c
+++ b/net/sunrpc/svcauth.c
@@ -27,12 +27,32 @@
 extern struct auth_ops svcauth_null;
 extern struct auth_ops svcauth_unix;
 
-static DEFINE_SPINLOCK(authtab_lock);
-static struct auth_ops	*authtab[RPC_AUTH_MAXFLAVOR] = {
-	[0] = &svcauth_null,
-	[1] = &svcauth_unix,
+static struct auth_ops __rcu *authtab[RPC_AUTH_MAXFLAVOR] = {
+	[RPC_AUTH_NULL] = (struct auth_ops __force __rcu *)&svcauth_null,
+	[RPC_AUTH_UNIX] = (struct auth_ops __force __rcu *)&svcauth_unix,
 };
 
+static struct auth_ops *
+svc_get_auth_ops(rpc_authflavor_t flavor)
+{
+	struct auth_ops		*aops;
+
+	if (flavor >= RPC_AUTH_MAXFLAVOR)
+		return NULL;
+	rcu_read_lock();
+	aops = rcu_dereference(authtab[flavor]);
+	if (aops != NULL && !try_module_get(aops->owner))
+		aops = NULL;
+	rcu_read_unlock();
+	return aops;
+}
+
+static void
+svc_put_auth_ops(struct auth_ops *aops)
+{
+	module_put(aops->owner);
+}
+
 int
 svc_authenticate(struct svc_rqst *rqstp, __be32 *authp)
 {
@@ -45,14 +65,11 @@ svc_authenticate(struct svc_rqst *rqstp, __be32 *authp)
 
 	dprintk("svc: svc_authenticate (%d)\n", flavor);
 
-	spin_lock(&authtab_lock);
-	if (flavor >= RPC_AUTH_MAXFLAVOR || !(aops = authtab[flavor]) ||
-	    !try_module_get(aops->owner)) {
-		spin_unlock(&authtab_lock);
+	aops = svc_get_auth_ops(flavor);
+	if (aops == NULL) {
 		*authp = rpc_autherr_badcred;
 		return SVC_DENIED;
 	}
-	spin_unlock(&authtab_lock);
 
 	rqstp->rq_auth_slack = 0;
 	init_svc_cred(&rqstp->rq_cred);
@@ -82,7 +99,7 @@ int svc_authorise(struct svc_rqst *rqstp)
 
 	if (aops) {
 		rv = aops->release(rqstp);
-		module_put(aops->owner);
+		svc_put_auth_ops(aops);
 	}
 	return rv;
 }
@@ -90,13 +107,14 @@ int svc_authorise(struct svc_rqst *rqstp)
 int
 svc_auth_register(rpc_authflavor_t flavor, struct auth_ops *aops)
 {
+	struct auth_ops *old;
 	int rv = -EINVAL;
-	spin_lock(&authtab_lock);
-	if (flavor < RPC_AUTH_MAXFLAVOR && authtab[flavor] == NULL) {
-		authtab[flavor] = aops;
-		rv = 0;
+
+	if (flavor < RPC_AUTH_MAXFLAVOR) {
+		old = cmpxchg((struct auth_ops ** __force)&authtab[flavor], NULL, aops);
+		if (old == NULL || old == aops)
+			rv = 0;
 	}
-	spin_unlock(&authtab_lock);
 	return rv;
 }
 EXPORT_SYMBOL_GPL(svc_auth_register);
@@ -104,10 +122,8 @@ EXPORT_SYMBOL_GPL(svc_auth_register);
 void
 svc_auth_unregister(rpc_authflavor_t flavor)
 {
-	spin_lock(&authtab_lock);
 	if (flavor < RPC_AUTH_MAXFLAVOR)
-		authtab[flavor] = NULL;
-	spin_unlock(&authtab_lock);
+		rcu_assign_pointer(authtab[flavor], NULL);
 }
 EXPORT_SYMBOL_GPL(svc_auth_unregister);
 
-- 
2.17.1

  reply	other threads:[~2018-10-01 21:20 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-01 14:41 [PATCH 00/15] Performance improvements for knfsd Trond Myklebust
2018-10-01 14:41 ` Trond Myklebust [this message]
2018-10-01 14:41   ` [PATCH 02/15] SUNRPC: Add lockless lookup of the server's auth domain Trond Myklebust
2018-10-01 14:41     ` [PATCH 03/15] SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock Trond Myklebust
2018-10-01 14:41       ` [PATCH 04/15] SUNRPC: Make server side AUTH_UNIX use lockless lookups Trond Myklebust
2018-10-01 14:41         ` [PATCH 05/15] knfsd: Allow lockless lookups of the exports Trond Myklebust
2018-10-01 14:41           ` [PATCH 06/15] SUNRPC: Lockless server RPCSEC_GSS context lookup Trond Myklebust
2018-10-01 14:41             ` [PATCH 07/15] knfsd: Lockless lookup of NFSv4 identities Trond Myklebust
2018-10-01 14:41               ` [PATCH 08/15] NFS: Lockless DNS lookups Trond Myklebust
2018-10-01 14:41                 ` [PATCH 09/15] SUNRPC: Remove non-RCU protected lookup Trond Myklebust
2018-10-01 14:41                   ` [PATCH 10/15] SUNRPC: Replace the cache_detail->hash_lock with a regular spinlock Trond Myklebust
2018-10-01 14:41                     ` [PATCH 11/15] SUNRPC: Simplify TCP receive code Trond Myklebust
2018-10-01 14:41                       ` [PATCH 12/15] knfsd: Remove dead code from nfsd_cache_lookup Trond Myklebust
2018-10-01 14:41                         ` [PATCH 13/15] knfsd: Simplify NFS duplicate replay cache Trond Myklebust
2018-10-01 14:41                           ` [PATCH 14/15] knfsd: Further simplify the cache lookup Trond Myklebust
2018-10-01 14:41                             ` [PATCH 15/15] knfsd: Improve lookup performance in the duplicate reply cache using an rbtree Trond Myklebust
2018-10-04  0:44                               ` J . Bruce Fields
2018-10-03 17:14                           ` [PATCH 13/15] knfsd: Simplify NFS duplicate replay cache J . Bruce Fields
2018-10-03 18:01                             ` Trond Myklebust
2018-10-03 18:11                               ` bfields
2018-10-03 23:51                                 ` bfields
2018-10-03 16:10                 ` [PATCH 08/15] NFS: Lockless DNS lookups J . Bruce Fields
2018-10-03 17:55                   ` Trond Myklebust
2018-10-03 16:08       ` [PATCH 03/15] SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock J . Bruce Fields
2018-10-02 19:39   ` [PATCH 01/15] SUNRPC: Remove the server 'authtab_lock' and just use RCU J . Bruce Fields
2018-10-01 15:29 ` [PATCH 00/15] Performance improvements for knfsd Trond Myklebust

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