[PATCH 00/15] Performance improvements for knfsd

[PATCH 00/15] Performance improvements for knfsd

[Trond Myklebust]

The following set of patches aim to remove some of the global spinlocks
that are currently being taken during the processing of every incoming
RPC call. Most of these spinlocks are protecting read-mostly structures,
and so can be replaced with taking an RCU read lock.

The patchset also replaces the current reader/writer spinlock in the
server cache implementation with an RCU read lock + a regular spinlock.
This gives a slight scalability improvement by allowing lookups to be
concurrent with updates rather than excluding them.

Finally, there is a set of changes to the NFSv2/v3/v4.0 duplicate reply
cache to further optimise it for the common case where we're only
inserting new entries. By using a red-black tree rather than a simple
linked list, we reduce the typical number of entries we need to check
(a.k.a. "chain length" in /proc/fs/nfsd/reply_cache_stats) from
roughly 80 to 9 per incoming RPC request. This significantly reduces the
total amount of time spent in nfsd_cache_lookup() according to 'perf'.

Trond Myklebust (15):
  SUNRPC: Remove the server 'authtab_lock' and just use RCU
  SUNRPC: Add lockless lookup of the server's auth domain
  SUNRPC: Allow cache lookups to use RCU protection rather than the r/w
    spinlock
  SUNRPC: Make server side AUTH_UNIX use lockless lookups
  knfsd: Allow lockless lookups of the exports
  SUNRPC: Lockless server RPCSEC_GSS context lookup
  knfsd: Lockless lookup of NFSv4 identities.
  NFS: Lockless DNS lookups
  SUNRPC: Remove non-RCU protected lookup
  SUNRPC: Replace the cache_detail->hash_lock with a regular spinlock
  SUNRPC: Simplify TCP receive code
  knfsd: Remove dead code from nfsd_cache_lookup
  knfsd: Simplify NFS duplicate replay cache
  knfsd: Further simplify the cache lookup
  knfsd: Improve lookup performance in the duplicate reply cache using
    an rbtree

 Documentation/filesystems/nfs/rpc-cache.txt |   6 +-
 fs/nfs/dns_resolve.c                        |  15 +-
 fs/nfsd/cache.h                             |  19 ++-
 fs/nfsd/export.c                            |  14 +-
 fs/nfsd/export.h                            |   2 +
 fs/nfsd/nfs4idmap.c                         |  11 +-
 fs/nfsd/nfscache.c                          | 142 +++++++++---------
 include/linux/sunrpc/cache.h                |  18 ++-
 include/linux/sunrpc/svcauth.h              |   1 +
 net/sunrpc/auth_gss/svcauth_gss.c           |  41 +++++-
 net/sunrpc/cache.c                          | 153 ++++++++++++--------
 net/sunrpc/svcauth.c                        |  74 +++++++---
 net/sunrpc/svcauth_unix.c                   |  24 ++-
 net/sunrpc/svcsock.c                        |  53 ++-----
 14 files changed, 327 insertions(+), 246 deletions(-)

-- 
2.17.1

[PATCH 01/15] SUNRPC: Remove the server 'authtab_lock' and just use RCU

[Trond Myklebust]

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

[PATCH 02/15] SUNRPC: Add lockless lookup of the server's auth domain

[Trond Myklebust]

Avoid taking the global auth_domain_lock in most lookups of the auth domain
by adding an RCU protected lookup.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 include/linux/sunrpc/svcauth.h    |  1 +
 net/sunrpc/auth_gss/svcauth_gss.c |  9 ++++++++-
 net/sunrpc/svcauth.c              | 22 +++++++++++++++++++---
 net/sunrpc/svcauth_unix.c         | 10 ++++++++--
 4 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/include/linux/sunrpc/svcauth.h b/include/linux/sunrpc/svcauth.h
index 04e404a07882..3e53a6e2ada7 100644
--- a/include/linux/sunrpc/svcauth.h
+++ b/include/linux/sunrpc/svcauth.h
@@ -82,6 +82,7 @@ struct auth_domain {
 	struct hlist_node	hash;
 	char			*name;
 	struct auth_ops		*flavour;
+	struct rcu_head		rcu_head;
 };
 
 /*
diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 860f2a1bbb67..87c71fb0f0ea 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -1764,14 +1764,21 @@ svcauth_gss_release(struct svc_rqst *rqstp)
 }
 
 static void
-svcauth_gss_domain_release(struct auth_domain *dom)
+svcauth_gss_domain_release_rcu(struct rcu_head *head)
 {
+	struct auth_domain *dom = container_of(head, struct auth_domain, rcu_head);
 	struct gss_domain *gd = container_of(dom, struct gss_domain, h);
 
 	kfree(dom->name);
 	kfree(gd);
 }
 
+static void
+svcauth_gss_domain_release(struct auth_domain *dom)
+{
+	call_rcu(&dom->rcu_head, svcauth_gss_domain_release_rcu);
+}
+
 static struct auth_ops svcauthops_gss = {
 	.name		= "rpcsec_gss",
 	.owner		= THIS_MODULE,
diff --git a/net/sunrpc/svcauth.c b/net/sunrpc/svcauth.c
index f83443856cd1..775b8c94265b 100644
--- a/net/sunrpc/svcauth.c
+++ b/net/sunrpc/svcauth.c
@@ -143,10 +143,11 @@ static struct hlist_head	auth_domain_table[DN_HASHMAX];
 static DEFINE_SPINLOCK(auth_domain_lock);
 
 static void auth_domain_release(struct kref *kref)
+	__releases(&auth_domain_lock)
 {
 	struct auth_domain *dom = container_of(kref, struct auth_domain, ref);
 
-	hlist_del(&dom->hash);
+	hlist_del_rcu(&dom->hash);
 	dom->flavour->domain_release(dom);
 	spin_unlock(&auth_domain_lock);
 }
@@ -175,7 +176,7 @@ auth_domain_lookup(char *name, struct auth_domain *new)
 		}
 	}
 	if (new)
-		hlist_add_head(&new->hash, head);
+		hlist_add_head_rcu(&new->hash, head);
 	spin_unlock(&auth_domain_lock);
 	return new;
 }
@@ -183,6 +184,21 @@ EXPORT_SYMBOL_GPL(auth_domain_lookup);
 
 struct auth_domain *auth_domain_find(char *name)
 {
-	return auth_domain_lookup(name, NULL);
+	struct auth_domain *hp;
+	struct hlist_head *head;
+
+	head = &auth_domain_table[hash_str(name, DN_HASHBITS)];
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(hp, head, hash) {
+		if (strcmp(hp->name, name)==0) {
+			if (!kref_get_unless_zero(&hp->ref))
+				hp = NULL;
+			rcu_read_unlock();
+			return hp;
+		}
+	}
+	rcu_read_unlock();
+	return NULL;
 }
 EXPORT_SYMBOL_GPL(auth_domain_find);
diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index af7f28fb8102..84cf39021a03 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -37,20 +37,26 @@ struct unix_domain {
 extern struct auth_ops svcauth_null;
 extern struct auth_ops svcauth_unix;
 
-static void svcauth_unix_domain_release(struct auth_domain *dom)
+static void svcauth_unix_domain_release_rcu(struct rcu_head *head)
 {
+	struct auth_domain *dom = container_of(head, struct auth_domain, rcu_head);
 	struct unix_domain *ud = container_of(dom, struct unix_domain, h);
 
 	kfree(dom->name);
 	kfree(ud);
 }
 
+static void svcauth_unix_domain_release(struct auth_domain *dom)
+{
+	call_rcu(&dom->rcu_head, svcauth_unix_domain_release_rcu);
+}
+
 struct auth_domain *unix_domain_find(char *name)
 {
 	struct auth_domain *rv;
 	struct unix_domain *new = NULL;
 
-	rv = auth_domain_lookup(name, NULL);
+	rv = auth_domain_find(name);
 	while(1) {
 		if (rv) {
 			if (new && rv != &new->h)
-- 
2.17.1

[PATCH 03/15] SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock

[Trond Myklebust]

Instead of the reader/writer spinlock, allow cache lookups to use RCU
for looking up entries. This is more efficient since modifications can
occur while other entries are being looked up.

Note that for now, we keep the reader/writer spinlock until all users
have been converted to use RCU-safe freeing of their cache entries.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 include/linux/sunrpc/cache.h |  12 ++++
 net/sunrpc/cache.c           | 122 +++++++++++++++++++++++++++++------
 2 files changed, 114 insertions(+), 20 deletions(-)

diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index 40d2822f0e2f..cf3e17ee2786 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -167,6 +167,9 @@ extern const struct file_operations cache_file_operations_pipefs;
 extern const struct file_operations content_file_operations_pipefs;
 extern const struct file_operations cache_flush_operations_pipefs;
 
+extern struct cache_head *
+sunrpc_cache_lookup_rcu(struct cache_detail *detail,
+			struct cache_head *key, int hash);
 extern struct cache_head *
 sunrpc_cache_lookup(struct cache_detail *detail,
 		    struct cache_head *key, int hash);
@@ -186,6 +189,12 @@ static inline struct cache_head  *cache_get(struct cache_head *h)
 	return h;
 }
 
+static inline struct cache_head  *cache_get_rcu(struct cache_head *h)
+{
+	if (kref_get_unless_zero(&h->ref))
+		return h;
+	return NULL;
+}
 
 static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
 {
@@ -227,6 +236,9 @@ extern void sunrpc_cache_unhash(struct cache_detail *, struct cache_head *);
 extern void *cache_seq_start(struct seq_file *file, loff_t *pos);
 extern void *cache_seq_next(struct seq_file *file, void *p, loff_t *pos);
 extern void cache_seq_stop(struct seq_file *file, void *p);
+extern void *cache_seq_start_rcu(struct seq_file *file, loff_t *pos);
+extern void *cache_seq_next_rcu(struct seq_file *file, void *p, loff_t *pos);
+extern void cache_seq_stop_rcu(struct seq_file *file, void *p);
 
 extern void qword_add(char **bpp, int *lp, char *str);
 extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 109fbe591e7b..7593afed9036 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -54,16 +54,34 @@ static void cache_init(struct cache_head *h, struct cache_detail *detail)
 	h->last_refresh = now;
 }
 
-struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
-				       struct cache_head *key, int hash)
+static struct cache_head *sunrpc_cache_find_rcu(struct cache_detail *detail,
+						struct cache_head *key,
+						int hash)
 {
-	struct cache_head *new = NULL, *freeme = NULL, *tmp = NULL;
-	struct hlist_head *head;
+	struct hlist_head *head = &detail->hash_table[hash];
+	struct cache_head *tmp;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(tmp, head, cache_list) {
+		if (detail->match(tmp, key)) {
+			if (cache_is_expired(detail, tmp))
+				continue;
+			tmp = cache_get_rcu(tmp);
+			rcu_read_unlock();
+			return tmp;
+		}
+	}
+	rcu_read_unlock();
+	return NULL;
+}
 
-	head = &detail->hash_table[hash];
+static struct cache_head *sunrpc_cache_find(struct cache_detail *detail,
+					    struct cache_head *key, int hash)
+{
+	struct hlist_head *head = &detail->hash_table[hash];
+	struct cache_head *tmp;
 
 	read_lock(&detail->hash_lock);
-
 	hlist_for_each_entry(tmp, head, cache_list) {
 		if (detail->match(tmp, key)) {
 			if (cache_is_expired(detail, tmp))
@@ -75,7 +93,15 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
 		}
 	}
 	read_unlock(&detail->hash_lock);
-	/* Didn't find anything, insert an empty entry */
+	return NULL;
+}
+
+static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
+						 struct cache_head *key,
+						 int hash)
+{
+	struct cache_head *new, *tmp, *freeme = NULL;
+	struct hlist_head *head = &detail->hash_table[hash];
 
 	new = detail->alloc();
 	if (!new)
@@ -90,10 +116,10 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
 	write_lock(&detail->hash_lock);
 
 	/* check if entry appeared while we slept */
-	hlist_for_each_entry(tmp, head, cache_list) {
+	hlist_for_each_entry_rcu(tmp, head, cache_list) {
 		if (detail->match(tmp, key)) {
 			if (cache_is_expired(detail, tmp)) {
-				hlist_del_init(&tmp->cache_list);
+				hlist_del_init_rcu(&tmp->cache_list);
 				detail->entries --;
 				freeme = tmp;
 				break;
@@ -105,7 +131,7 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
 		}
 	}
 
-	hlist_add_head(&new->cache_list, head);
+	hlist_add_head_rcu(&new->cache_list, head);
 	detail->entries++;
 	cache_get(new);
 	write_unlock(&detail->hash_lock);
@@ -114,6 +140,31 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
 		cache_put(freeme, detail);
 	return new;
 }
+
+struct cache_head *sunrpc_cache_lookup_rcu(struct cache_detail *detail,
+					   struct cache_head *key, int hash)
+{
+	struct cache_head *ret;
+
+	ret = sunrpc_cache_find_rcu(detail, key, hash);
+	if (ret)
+		return ret;
+	/* Didn't find anything, insert an empty entry */
+	return sunrpc_cache_add_entry(detail, key, hash);
+}
+EXPORT_SYMBOL_GPL(sunrpc_cache_lookup_rcu);
+
+struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
+				       struct cache_head *key, int hash)
+{
+	struct cache_head *ret;
+
+	ret = sunrpc_cache_find(detail, key, hash);
+	if (ret)
+		return ret;
+	/* Didn't find anything, insert an empty entry */
+	return sunrpc_cache_add_entry(detail, key, hash);
+}
 EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);
 
 
@@ -433,7 +484,7 @@ static int cache_clean(void)
 			if (!cache_is_expired(current_detail, ch))
 				continue;
 
-			hlist_del_init(&ch->cache_list);
+			hlist_del_init_rcu(&ch->cache_list);
 			current_detail->entries--;
 			rv = 1;
 			break;
@@ -504,7 +555,7 @@ void cache_purge(struct cache_detail *detail)
 	for (i = 0; i < detail->hash_size; i++) {
 		head = &detail->hash_table[i];
 		hlist_for_each_entry_safe(ch, tmp, head, cache_list) {
-			hlist_del_init(&ch->cache_list);
+			hlist_del_init_rcu(&ch->cache_list);
 			detail->entries--;
 
 			set_bit(CACHE_CLEANED, &ch->flags);
@@ -1289,21 +1340,19 @@ EXPORT_SYMBOL_GPL(qword_get);
  * get a header, then pass each real item in the cache
  */
 
-void *cache_seq_start(struct seq_file *m, loff_t *pos)
-	__acquires(cd->hash_lock)
+static void *__cache_seq_start(struct seq_file *m, loff_t *pos)
 {
 	loff_t n = *pos;
 	unsigned int hash, entry;
 	struct cache_head *ch;
 	struct cache_detail *cd = m->private;
 
-	read_lock(&cd->hash_lock);
 	if (!n--)
 		return SEQ_START_TOKEN;
 	hash = n >> 32;
 	entry = n & ((1LL<<32) - 1);
 
-	hlist_for_each_entry(ch, &cd->hash_table[hash], cache_list)
+	hlist_for_each_entry_rcu(ch, &cd->hash_table[hash], cache_list)
 		if (!entry--)
 			return ch;
 	n &= ~((1LL<<32) - 1);
@@ -1315,9 +1364,19 @@ void *cache_seq_start(struct seq_file *m, loff_t *pos)
 	if (hash >= cd->hash_size)
 		return NULL;
 	*pos = n+1;
-	return hlist_entry_safe(cd->hash_table[hash].first,
+	return hlist_entry_safe(rcu_dereference_raw(
+				hlist_first_rcu(&cd->hash_table[hash])),
 				struct cache_head, cache_list);
 }
+
+void *cache_seq_start(struct seq_file *m, loff_t *pos)
+	__acquires(cd->hash_lock)
+{
+	struct cache_detail *cd = m->private;
+
+	read_lock(&cd->hash_lock);
+	return __cache_seq_start(m, pos);
+}
 EXPORT_SYMBOL_GPL(cache_seq_start);
 
 void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
@@ -1333,7 +1392,8 @@ void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
 		*pos += 1LL<<32;
 	} else {
 		++*pos;
-		return hlist_entry_safe(ch->cache_list.next,
+		return hlist_entry_safe(rcu_dereference_raw(
+					hlist_next_rcu(&ch->cache_list)),
 					struct cache_head, cache_list);
 	}
 	*pos &= ~((1LL<<32) - 1);
@@ -1345,7 +1405,8 @@ void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
 	if (hash >= cd->hash_size)
 		return NULL;
 	++*pos;
-	return hlist_entry_safe(cd->hash_table[hash].first,
+	return hlist_entry_safe(rcu_dereference_raw(
+				hlist_first_rcu(&cd->hash_table[hash])),
 				struct cache_head, cache_list);
 }
 EXPORT_SYMBOL_GPL(cache_seq_next);
@@ -1358,6 +1419,27 @@ void cache_seq_stop(struct seq_file *m, void *p)
 }
 EXPORT_SYMBOL_GPL(cache_seq_stop);
 
+void *cache_seq_start_rcu(struct seq_file *m, loff_t *pos)
+	__acquires(RCU)
+{
+	rcu_read_lock();
+	return __cache_seq_start(m, pos);
+}
+EXPORT_SYMBOL_GPL(cache_seq_start_rcu);
+
+void *cache_seq_next_rcu(struct seq_file *file, void *p, loff_t *pos)
+{
+	return cache_seq_next(file, p, pos);
+}
+EXPORT_SYMBOL_GPL(cache_seq_next_rcu);
+
+void cache_seq_stop_rcu(struct seq_file *m, void *p)
+	__releases(RCU)
+{
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(cache_seq_stop_rcu);
+
 static int c_show(struct seq_file *m, void *p)
 {
 	struct cache_head *cp = p;
@@ -1846,7 +1928,7 @@ void sunrpc_cache_unhash(struct cache_detail *cd, struct cache_head *h)
 {
 	write_lock(&cd->hash_lock);
 	if (!hlist_unhashed(&h->cache_list)){
-		hlist_del_init(&h->cache_list);
+		hlist_del_init_rcu(&h->cache_list);
 		cd->entries--;
 		write_unlock(&cd->hash_lock);
 		cache_put(h, cd);
-- 
2.17.1

[PATCH 04/15] SUNRPC: Make server side AUTH_UNIX use lockless lookups

[Trond Myklebust]

Convert structs ip_map and unix_gid to use RCU protected lookups.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 net/sunrpc/svcauth_unix.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 84cf39021a03..fb9041b92f72 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -97,6 +97,7 @@ struct ip_map {
 	char			m_class[8]; /* e.g. "nfsd" */
 	struct in6_addr		m_addr;
 	struct unix_domain	*m_client;
+	struct rcu_head		m_rcu;
 };
 
 static void ip_map_put(struct kref *kref)
@@ -107,7 +108,7 @@ static void ip_map_put(struct kref *kref)
 	if (test_bit(CACHE_VALID, &item->flags) &&
 	    !test_bit(CACHE_NEGATIVE, &item->flags))
 		auth_domain_put(&im->m_client->h);
-	kfree(im);
+	kfree_rcu(im, m_rcu);
 }
 
 static inline int hash_ip6(const struct in6_addr *ip)
@@ -286,9 +287,9 @@ static struct ip_map *__ip_map_lookup(struct cache_detail *cd, char *class,
 
 	strcpy(ip.m_class, class);
 	ip.m_addr = *addr;
-	ch = sunrpc_cache_lookup(cd, &ip.h,
-				 hash_str(class, IP_HASHBITS) ^
-				 hash_ip6(addr));
+	ch = sunrpc_cache_lookup_rcu(cd, &ip.h,
+				     hash_str(class, IP_HASHBITS) ^
+				     hash_ip6(addr));
 
 	if (ch)
 		return container_of(ch, struct ip_map, h);
@@ -418,6 +419,7 @@ struct unix_gid {
 	struct cache_head	h;
 	kuid_t			uid;
 	struct group_info	*gi;
+	struct rcu_head		rcu;
 };
 
 static int unix_gid_hash(kuid_t uid)
@@ -432,7 +434,7 @@ static void unix_gid_put(struct kref *kref)
 	if (test_bit(CACHE_VALID, &item->flags) &&
 	    !test_bit(CACHE_NEGATIVE, &item->flags))
 		put_group_info(ug->gi);
-	kfree(ug);
+	kfree_rcu(ug, rcu);
 }
 
 static int unix_gid_match(struct cache_head *corig, struct cache_head *cnew)
@@ -625,7 +627,7 @@ static struct unix_gid *unix_gid_lookup(struct cache_detail *cd, kuid_t uid)
 	struct cache_head *ch;
 
 	ug.uid = uid;
-	ch = sunrpc_cache_lookup(cd, &ug.h, unix_gid_hash(uid));
+	ch = sunrpc_cache_lookup_rcu(cd, &ug.h, unix_gid_hash(uid));
 	if (ch)
 		return container_of(ch, struct unix_gid, h);
 	else
-- 
2.17.1

[PATCH 05/15] knfsd: Allow lockless lookups of the exports

[Trond Myklebust]

Convert structs svc_expkey and svc_export to allow RCU protected lookups.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfsd/export.c | 14 +++++++-------
 fs/nfsd/export.h |  2 ++
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index a1143f7c2201..802993d8912f 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -46,7 +46,7 @@ static void expkey_put(struct kref *ref)
 	    !test_bit(CACHE_NEGATIVE, &key->h.flags))
 		path_put(&key->ek_path);
 	auth_domain_put(key->ek_client);
-	kfree(key);
+	kfree_rcu(key, ek_rcu);
 }
 
 static void expkey_request(struct cache_detail *cd,
@@ -265,7 +265,7 @@ svc_expkey_lookup(struct cache_detail *cd, struct svc_expkey *item)
 	struct cache_head *ch;
 	int hash = svc_expkey_hash(item);
 
-	ch = sunrpc_cache_lookup(cd, &item->h, hash);
+	ch = sunrpc_cache_lookup_rcu(cd, &item->h, hash);
 	if (ch)
 		return container_of(ch, struct svc_expkey, h);
 	else
@@ -314,7 +314,7 @@ static void svc_export_put(struct kref *ref)
 	auth_domain_put(exp->ex_client);
 	nfsd4_fslocs_free(&exp->ex_fslocs);
 	kfree(exp->ex_uuid);
-	kfree(exp);
+	kfree_rcu(exp, ex_rcu);
 }
 
 static void svc_export_request(struct cache_detail *cd,
@@ -780,7 +780,7 @@ svc_export_lookup(struct svc_export *exp)
 	struct cache_head *ch;
 	int hash = svc_export_hash(exp);
 
-	ch = sunrpc_cache_lookup(exp->cd, &exp->h, hash);
+	ch = sunrpc_cache_lookup_rcu(exp->cd, &exp->h, hash);
 	if (ch)
 		return container_of(ch, struct svc_export, h);
 	else
@@ -1216,9 +1216,9 @@ static int e_show(struct seq_file *m, void *p)
 }
 
 const struct seq_operations nfs_exports_op = {
-	.start	= cache_seq_start,
-	.next	= cache_seq_next,
-	.stop	= cache_seq_stop,
+	.start	= cache_seq_start_rcu,
+	.next	= cache_seq_next_rcu,
+	.stop	= cache_seq_stop_rcu,
 	.show	= e_show,
 };
 
diff --git a/fs/nfsd/export.h b/fs/nfsd/export.h
index c8b74126ddaa..e7daa1f246f0 100644
--- a/fs/nfsd/export.h
+++ b/fs/nfsd/export.h
@@ -61,6 +61,7 @@ struct svc_export {
 	u32			ex_layout_types;
 	struct nfsd4_deviceid_map *ex_devid_map;
 	struct cache_detail	*cd;
+	struct rcu_head		ex_rcu;
 };
 
 /* an "export key" (expkey) maps a filehandlefragement to an
@@ -75,6 +76,7 @@ struct svc_expkey {
 	u32			ek_fsid[6];
 
 	struct path		ek_path;
+	struct rcu_head		ek_rcu;
 };
 
 #define EX_ISSYNC(exp)		(!((exp)->ex_flags & NFSEXP_ASYNC))
-- 
2.17.1

[PATCH 06/15] SUNRPC: Lockless server RPCSEC_GSS context lookup

[Trond Myklebust]

Use RCU protection for looking up the RPCSEC_GSS context.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 net/sunrpc/auth_gss/svcauth_gss.c | 32 +++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 87c71fb0f0ea..1ece4bc3eb8d 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -76,6 +76,7 @@ struct rsi {
 	struct xdr_netobj	in_handle, in_token;
 	struct xdr_netobj	out_handle, out_token;
 	int			major_status, minor_status;
+	struct rcu_head		rcu_head;
 };
 
 static struct rsi *rsi_update(struct cache_detail *cd, struct rsi *new, struct rsi *old);
@@ -89,13 +90,21 @@ static void rsi_free(struct rsi *rsii)
 	kfree(rsii->out_token.data);
 }
 
-static void rsi_put(struct kref *ref)
+static void rsi_free_rcu(struct rcu_head *head)
 {
-	struct rsi *rsii = container_of(ref, struct rsi, h.ref);
+	struct rsi *rsii = container_of(head, struct rsi, rcu_head);
+
 	rsi_free(rsii);
 	kfree(rsii);
 }
 
+static void rsi_put(struct kref *ref)
+{
+	struct rsi *rsii = container_of(ref, struct rsi, h.ref);
+
+	call_rcu(&rsii->rcu_head, rsi_free_rcu);
+}
+
 static inline int rsi_hash(struct rsi *item)
 {
 	return hash_mem(item->in_handle.data, item->in_handle.len, RSI_HASHBITS)
@@ -282,7 +291,7 @@ static struct rsi *rsi_lookup(struct cache_detail *cd, struct rsi *item)
 	struct cache_head *ch;
 	int hash = rsi_hash(item);
 
-	ch = sunrpc_cache_lookup(cd, &item->h, hash);
+	ch = sunrpc_cache_lookup_rcu(cd, &item->h, hash);
 	if (ch)
 		return container_of(ch, struct rsi, h);
 	else
@@ -330,6 +339,7 @@ struct rsc {
 	struct svc_cred		cred;
 	struct gss_svc_seq_data	seqdata;
 	struct gss_ctx		*mechctx;
+	struct rcu_head		rcu_head;
 };
 
 static struct rsc *rsc_update(struct cache_detail *cd, struct rsc *new, struct rsc *old);
@@ -343,12 +353,22 @@ static void rsc_free(struct rsc *rsci)
 	free_svc_cred(&rsci->cred);
 }
 
+static void rsc_free_rcu(struct rcu_head *head)
+{
+	struct rsc *rsci = container_of(head, struct rsc, rcu_head);
+
+	kfree(rsci->handle.data);
+	kfree(rsci);
+}
+
 static void rsc_put(struct kref *ref)
 {
 	struct rsc *rsci = container_of(ref, struct rsc, h.ref);
 
-	rsc_free(rsci);
-	kfree(rsci);
+	if (rsci->mechctx)
+		gss_delete_sec_context(&rsci->mechctx);
+	free_svc_cred(&rsci->cred);
+	call_rcu(&rsci->rcu_head, rsc_free_rcu);
 }
 
 static inline int
@@ -542,7 +562,7 @@ static struct rsc *rsc_lookup(struct cache_detail *cd, struct rsc *item)
 	struct cache_head *ch;
 	int hash = rsc_hash(item);
 
-	ch = sunrpc_cache_lookup(cd, &item->h, hash);
+	ch = sunrpc_cache_lookup_rcu(cd, &item->h, hash);
 	if (ch)
 		return container_of(ch, struct rsc, h);
 	else
-- 
2.17.1

[PATCH 07/15] knfsd: Lockless lookup of NFSv4 identities.

[Trond Myklebust]

Enable RCU protected lookups of the NFSv4 idmap.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfsd/nfs4idmap.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/nfsd/nfs4idmap.c b/fs/nfsd/nfs4idmap.c
index a5bb76593ce7..bf137fec33ff 100644
--- a/fs/nfsd/nfs4idmap.c
+++ b/fs/nfsd/nfs4idmap.c
@@ -65,6 +65,7 @@ struct ent {
 	u32               id;
 	char              name[IDMAP_NAMESZ];
 	char              authname[IDMAP_NAMESZ];
+	struct rcu_head	  rcu_head;
 };
 
 /* Common entry handling */
@@ -89,7 +90,7 @@ static void
 ent_put(struct kref *ref)
 {
 	struct ent *map = container_of(ref, struct ent, h.ref);
-	kfree(map);
+	kfree_rcu(map, rcu_head);
 }
 
 static struct cache_head *
@@ -264,8 +265,8 @@ idtoname_parse(struct cache_detail *cd, char *buf, int buflen)
 static struct ent *
 idtoname_lookup(struct cache_detail *cd, struct ent *item)
 {
-	struct cache_head *ch = sunrpc_cache_lookup(cd, &item->h,
-						    idtoname_hash(item));
+	struct cache_head *ch = sunrpc_cache_lookup_rcu(cd, &item->h,
+							idtoname_hash(item));
 	if (ch)
 		return container_of(ch, struct ent, h);
 	else
@@ -422,8 +423,8 @@ nametoid_parse(struct cache_detail *cd, char *buf, int buflen)
 static struct ent *
 nametoid_lookup(struct cache_detail *cd, struct ent *item)
 {
-	struct cache_head *ch = sunrpc_cache_lookup(cd, &item->h,
-						    nametoid_hash(item));
+	struct cache_head *ch = sunrpc_cache_lookup_rcu(cd, &item->h,
+							nametoid_hash(item));
 	if (ch)
 		return container_of(ch, struct ent, h);
 	else
-- 
2.17.1

[PATCH 08/15] NFS: Lockless DNS lookups

[Trond Myklebust]

Enable RCU protected lookup in the legacy DNS resolver.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/dns_resolve.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index 060c658eab66..e93a5dc07c8c 100644
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -65,6 +65,7 @@ struct nfs_dns_ent {
 
 	struct sockaddr_storage addr;
 	size_t addrlen;
+	struct rcu_head rcu_head;
 };
 
 
@@ -101,15 +102,23 @@ static void nfs_dns_ent_init(struct cache_head *cnew,
 	}
 }
 
-static void nfs_dns_ent_put(struct kref *ref)
+static void nfs_dns_ent_free_rcu(struct rcu_head *head)
 {
 	struct nfs_dns_ent *item;
 
-	item = container_of(ref, struct nfs_dns_ent, h.ref);
+	item = container_of(head, struct nfs_dns_ent, rcu_head);
 	kfree(item->hostname);
 	kfree(item);
 }
 
+static void nfs_dns_ent_put(struct kref *ref)
+{
+	struct nfs_dns_ent *item;
+
+	item = container_of(ref, struct nfs_dns_ent, h.ref);
+	call_rcu(item, nfs_dns_ent_free_rcu);
+}
+
 static struct cache_head *nfs_dns_ent_alloc(void)
 {
 	struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
@@ -195,7 +204,7 @@ static struct nfs_dns_ent *nfs_dns_lookup(struct cache_detail *cd,
 {
 	struct cache_head *ch;
 
-	ch = sunrpc_cache_lookup(cd,
+	ch = sunrpc_cache_lookup_rcu(cd,
 			&key->h,
 			nfs_dns_hash(key));
 	if (!ch)
-- 
2.17.1

[PATCH 09/15] SUNRPC: Remove non-RCU protected lookup

[Trond Myklebust]

Clean up the cache code by removing the non-RCU protected lookup.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 Documentation/filesystems/nfs/rpc-cache.txt |  6 +-
 include/linux/sunrpc/cache.h                |  6 --
 net/sunrpc/cache.c                          | 61 ++-------------------
 3 files changed, 7 insertions(+), 66 deletions(-)

diff --git a/Documentation/filesystems/nfs/rpc-cache.txt b/Documentation/filesystems/nfs/rpc-cache.txt
index ebcaaee21616..c4dac829db0f 100644
--- a/Documentation/filesystems/nfs/rpc-cache.txt
+++ b/Documentation/filesystems/nfs/rpc-cache.txt
@@ -84,7 +84,7 @@ Creating a Cache
 		A message from user space has arrived to fill out a
 		cache entry.  It is in 'buf' of length 'len'.
 		cache_parse should parse this, find the item in the
-		cache with sunrpc_cache_lookup, and update the item
+		cache with sunrpc_cache_lookup_rcu, and update the item
 		with sunrpc_cache_update.
 
 
@@ -95,7 +95,7 @@ Creating a Cache
 Using a cache
 -------------
 
-To find a value in a cache, call sunrpc_cache_lookup passing a pointer
+To find a value in a cache, call sunrpc_cache_lookup_rcu passing a pointer
 to the cache_head in a sample item with the 'key' fields filled in.
 This will be passed to ->match to identify the target entry.  If no
 entry is found, a new entry will be create, added to the cache, and
@@ -116,7 +116,7 @@ item does become valid, the deferred copy of the request will be
 revisited (->revisit).  It is expected that this method will
 reschedule the request for processing.
 
-The value returned by sunrpc_cache_lookup can also be passed to
+The value returned by sunrpc_cache_lookup_rcu can also be passed to
 sunrpc_cache_update to set the content for the item.  A second item is
 passed which should hold the content.  If the item found by _lookup
 has valid data, then it is discarded and a new item is created.  This
diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index cf3e17ee2786..c3d67e893430 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -171,9 +171,6 @@ extern struct cache_head *
 sunrpc_cache_lookup_rcu(struct cache_detail *detail,
 			struct cache_head *key, int hash);
 extern struct cache_head *
-sunrpc_cache_lookup(struct cache_detail *detail,
-		    struct cache_head *key, int hash);
-extern struct cache_head *
 sunrpc_cache_update(struct cache_detail *detail,
 		    struct cache_head *new, struct cache_head *old, int hash);
 
@@ -233,9 +230,6 @@ extern void sunrpc_cache_unregister_pipefs(struct cache_detail *);
 extern void sunrpc_cache_unhash(struct cache_detail *, struct cache_head *);
 
 /* Must store cache_detail in seq_file->private if using next three functions */
-extern void *cache_seq_start(struct seq_file *file, loff_t *pos);
-extern void *cache_seq_next(struct seq_file *file, void *p, loff_t *pos);
-extern void cache_seq_stop(struct seq_file *file, void *p);
 extern void *cache_seq_start_rcu(struct seq_file *file, loff_t *pos);
 extern void *cache_seq_next_rcu(struct seq_file *file, void *p, loff_t *pos);
 extern void cache_seq_stop_rcu(struct seq_file *file, void *p);
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 7593afed9036..593cf8607414 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -75,27 +75,6 @@ static struct cache_head *sunrpc_cache_find_rcu(struct cache_detail *detail,
 	return NULL;
 }
 
-static struct cache_head *sunrpc_cache_find(struct cache_detail *detail,
-					    struct cache_head *key, int hash)
-{
-	struct hlist_head *head = &detail->hash_table[hash];
-	struct cache_head *tmp;
-
-	read_lock(&detail->hash_lock);
-	hlist_for_each_entry(tmp, head, cache_list) {
-		if (detail->match(tmp, key)) {
-			if (cache_is_expired(detail, tmp))
-				/* This entry is expired, we will discard it. */
-				break;
-			cache_get(tmp);
-			read_unlock(&detail->hash_lock);
-			return tmp;
-		}
-	}
-	read_unlock(&detail->hash_lock);
-	return NULL;
-}
-
 static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
 						 struct cache_head *key,
 						 int hash)
@@ -154,20 +133,6 @@ struct cache_head *sunrpc_cache_lookup_rcu(struct cache_detail *detail,
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_lookup_rcu);
 
-struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
-				       struct cache_head *key, int hash)
-{
-	struct cache_head *ret;
-
-	ret = sunrpc_cache_find(detail, key, hash);
-	if (ret)
-		return ret;
-	/* Didn't find anything, insert an empty entry */
-	return sunrpc_cache_add_entry(detail, key, hash);
-}
-EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);
-
-
 static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch);
 
 static void cache_fresh_locked(struct cache_head *head, time_t expiry,
@@ -1369,17 +1334,7 @@ static void *__cache_seq_start(struct seq_file *m, loff_t *pos)
 				struct cache_head, cache_list);
 }
 
-void *cache_seq_start(struct seq_file *m, loff_t *pos)
-	__acquires(cd->hash_lock)
-{
-	struct cache_detail *cd = m->private;
-
-	read_lock(&cd->hash_lock);
-	return __cache_seq_start(m, pos);
-}
-EXPORT_SYMBOL_GPL(cache_seq_start);
-
-void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
+static void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
 {
 	struct cache_head *ch = p;
 	int hash = (*pos >> 32);
@@ -1411,14 +1366,6 @@ void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
 }
 EXPORT_SYMBOL_GPL(cache_seq_next);
 
-void cache_seq_stop(struct seq_file *m, void *p)
-	__releases(cd->hash_lock)
-{
-	struct cache_detail *cd = m->private;
-	read_unlock(&cd->hash_lock);
-}
-EXPORT_SYMBOL_GPL(cache_seq_stop);
-
 void *cache_seq_start_rcu(struct seq_file *m, loff_t *pos)
 	__acquires(RCU)
 {
@@ -1466,9 +1413,9 @@ static int c_show(struct seq_file *m, void *p)
 }
 
 static const struct seq_operations cache_content_op = {
-	.start	= cache_seq_start,
-	.next	= cache_seq_next,
-	.stop	= cache_seq_stop,
+	.start	= cache_seq_start_rcu,
+	.next	= cache_seq_next_rcu,
+	.stop	= cache_seq_stop_rcu,
 	.show	= c_show,
 };
 
-- 
2.17.1

[PATCH 10/15] SUNRPC: Replace the cache_detail->hash_lock with a regular spinlock

[Trond Myklebust]

Now that the reader functions are all RCU protected, use a regular
spinlock rather than a reader/writer lock.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 include/linux/sunrpc/cache.h |  2 +-
 net/sunrpc/cache.c           | 46 ++++++++++++++++++------------------
 2 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index c3d67e893430..5a3e95017fc6 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -67,7 +67,7 @@ struct cache_detail {
 	struct module *		owner;
 	int			hash_size;
 	struct hlist_head *	hash_table;
-	rwlock_t		hash_lock;
+	spinlock_t		hash_lock;
 
 	char			*name;
 	void			(*cache_put)(struct kref *);
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 593cf8607414..f96345b1180e 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -92,7 +92,7 @@ static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
 	cache_init(new, detail);
 	detail->init(new, key);
 
-	write_lock(&detail->hash_lock);
+	spin_lock(&detail->hash_lock);
 
 	/* check if entry appeared while we slept */
 	hlist_for_each_entry_rcu(tmp, head, cache_list) {
@@ -104,7 +104,7 @@ static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
 				break;
 			}
 			cache_get(tmp);
-			write_unlock(&detail->hash_lock);
+			spin_unlock(&detail->hash_lock);
 			cache_put(new, detail);
 			return tmp;
 		}
@@ -113,7 +113,7 @@ static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
 	hlist_add_head_rcu(&new->cache_list, head);
 	detail->entries++;
 	cache_get(new);
-	write_unlock(&detail->hash_lock);
+	spin_unlock(&detail->hash_lock);
 
 	if (freeme)
 		cache_put(freeme, detail);
@@ -167,18 +167,18 @@ struct cache_head *sunrpc_cache_update(struct cache_detail *detail,
 	struct cache_head *tmp;
 
 	if (!test_bit(CACHE_VALID, &old->flags)) {
-		write_lock(&detail->hash_lock);
+		spin_lock(&detail->hash_lock);
 		if (!test_bit(CACHE_VALID, &old->flags)) {
 			if (test_bit(CACHE_NEGATIVE, &new->flags))
 				set_bit(CACHE_NEGATIVE, &old->flags);
 			else
 				detail->update(old, new);
 			cache_fresh_locked(old, new->expiry_time, detail);
-			write_unlock(&detail->hash_lock);
+			spin_unlock(&detail->hash_lock);
 			cache_fresh_unlocked(old, detail);
 			return old;
 		}
-		write_unlock(&detail->hash_lock);
+		spin_unlock(&detail->hash_lock);
 	}
 	/* We need to insert a new entry */
 	tmp = detail->alloc();
@@ -189,7 +189,7 @@ struct cache_head *sunrpc_cache_update(struct cache_detail *detail,
 	cache_init(tmp, detail);
 	detail->init(tmp, old);
 
-	write_lock(&detail->hash_lock);
+	spin_lock(&detail->hash_lock);
 	if (test_bit(CACHE_NEGATIVE, &new->flags))
 		set_bit(CACHE_NEGATIVE, &tmp->flags);
 	else
@@ -199,7 +199,7 @@ struct cache_head *sunrpc_cache_update(struct cache_detail *detail,
 	cache_get(tmp);
 	cache_fresh_locked(tmp, new->expiry_time, detail);
 	cache_fresh_locked(old, 0, detail);
-	write_unlock(&detail->hash_lock);
+	spin_unlock(&detail->hash_lock);
 	cache_fresh_unlocked(tmp, detail);
 	cache_fresh_unlocked(old, detail);
 	cache_put(old, detail);
@@ -239,7 +239,7 @@ static int try_to_negate_entry(struct cache_detail *detail, struct cache_head *h
 {
 	int rv;
 
-	write_lock(&detail->hash_lock);
+	spin_lock(&detail->hash_lock);
 	rv = cache_is_valid(h);
 	if (rv == -EAGAIN) {
 		set_bit(CACHE_NEGATIVE, &h->flags);
@@ -247,7 +247,7 @@ static int try_to_negate_entry(struct cache_detail *detail, struct cache_head *h
 				   detail);
 		rv = -ENOENT;
 	}
-	write_unlock(&detail->hash_lock);
+	spin_unlock(&detail->hash_lock);
 	cache_fresh_unlocked(h, detail);
 	return rv;
 }
@@ -357,7 +357,7 @@ static struct delayed_work cache_cleaner;
 
 void sunrpc_init_cache_detail(struct cache_detail *cd)
 {
-	rwlock_init(&cd->hash_lock);
+	spin_lock_init(&cd->hash_lock);
 	INIT_LIST_HEAD(&cd->queue);
 	spin_lock(&cache_list_lock);
 	cd->nextcheck = 0;
@@ -377,11 +377,11 @@ void sunrpc_destroy_cache_detail(struct cache_detail *cd)
 {
 	cache_purge(cd);
 	spin_lock(&cache_list_lock);
-	write_lock(&cd->hash_lock);
+	spin_lock(&cd->hash_lock);
 	if (current_detail == cd)
 		current_detail = NULL;
 	list_del_init(&cd->others);
-	write_unlock(&cd->hash_lock);
+	spin_unlock(&cd->hash_lock);
 	spin_unlock(&cache_list_lock);
 	if (list_empty(&cache_list)) {
 		/* module must be being unloaded so its safe to kill the worker */
@@ -438,7 +438,7 @@ static int cache_clean(void)
 		struct hlist_head *head;
 		struct hlist_node *tmp;
 
-		write_lock(&current_detail->hash_lock);
+		spin_lock(&current_detail->hash_lock);
 
 		/* Ok, now to clean this strand */
 
@@ -455,7 +455,7 @@ static int cache_clean(void)
 			break;
 		}
 
-		write_unlock(&current_detail->hash_lock);
+		spin_unlock(&current_detail->hash_lock);
 		d = current_detail;
 		if (!ch)
 			current_index ++;
@@ -510,9 +510,9 @@ void cache_purge(struct cache_detail *detail)
 	struct hlist_node *tmp = NULL;
 	int i = 0;
 
-	write_lock(&detail->hash_lock);
+	spin_lock(&detail->hash_lock);
 	if (!detail->entries) {
-		write_unlock(&detail->hash_lock);
+		spin_unlock(&detail->hash_lock);
 		return;
 	}
 
@@ -524,13 +524,13 @@ void cache_purge(struct cache_detail *detail)
 			detail->entries--;
 
 			set_bit(CACHE_CLEANED, &ch->flags);
-			write_unlock(&detail->hash_lock);
+			spin_unlock(&detail->hash_lock);
 			cache_fresh_unlocked(ch, detail);
 			cache_put(ch, detail);
-			write_lock(&detail->hash_lock);
+			spin_lock(&detail->hash_lock);
 		}
 	}
-	write_unlock(&detail->hash_lock);
+	spin_unlock(&detail->hash_lock);
 }
 EXPORT_SYMBOL_GPL(cache_purge);
 
@@ -1873,13 +1873,13 @@ EXPORT_SYMBOL_GPL(sunrpc_cache_unregister_pipefs);
 
 void sunrpc_cache_unhash(struct cache_detail *cd, struct cache_head *h)
 {
-	write_lock(&cd->hash_lock);
+	spin_lock(&cd->hash_lock);
 	if (!hlist_unhashed(&h->cache_list)){
 		hlist_del_init_rcu(&h->cache_list);
 		cd->entries--;
-		write_unlock(&cd->hash_lock);
+		spin_unlock(&cd->hash_lock);
 		cache_put(h, cd);
 	} else
-		write_unlock(&cd->hash_lock);
+		spin_unlock(&cd->hash_lock);
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_unhash);
-- 
2.17.1

[PATCH 11/15] SUNRPC: Simplify TCP receive code

[Trond Myklebust]

Use the fact that the iov iterators already have functionality for
skipping a base offset.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 net/sunrpc/svcsock.c | 53 ++++++++++++--------------------------------
 1 file changed, 14 insertions(+), 39 deletions(-)

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 5445145e639c..64765f08ae07 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -325,59 +325,34 @@ static int svc_one_sock_name(struct svc_sock *svsk, char *buf, int remaining)
 /*
  * Generic recvfrom routine.
  */
-static int svc_recvfrom(struct svc_rqst *rqstp, struct kvec *iov, int nr,
-			int buflen)
+static ssize_t svc_recvfrom(struct svc_rqst *rqstp, struct kvec *iov,
+			    unsigned int nr, size_t buflen, unsigned int base)
 {
 	struct svc_sock *svsk =
 		container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
-	struct msghdr msg = {
-		.msg_flags	= MSG_DONTWAIT,
-	};
-	int len;
+	struct msghdr msg = { NULL };
+	ssize_t len;
 
 	rqstp->rq_xprt_hlen = 0;
 
 	clear_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
 	iov_iter_kvec(&msg.msg_iter, READ | ITER_KVEC, iov, nr, buflen);
-	len = sock_recvmsg(svsk->sk_sock, &msg, msg.msg_flags);
+	if (base != 0) {
+		iov_iter_advance(&msg.msg_iter, base);
+		buflen -= base;
+	}
+	len = sock_recvmsg(svsk->sk_sock, &msg, MSG_DONTWAIT);
 	/* If we read a full record, then assume there may be more
 	 * data to read (stream based sockets only!)
 	 */
 	if (len == buflen)
 		set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
 
-	dprintk("svc: socket %p recvfrom(%p, %zu) = %d\n",
+	dprintk("svc: socket %p recvfrom(%p, %zu) = %zd\n",
 		svsk, iov[0].iov_base, iov[0].iov_len, len);
 	return len;
 }
 
-static int svc_partial_recvfrom(struct svc_rqst *rqstp,
-				struct kvec *iov, int nr,
-				int buflen, unsigned int base)
-{
-	size_t save_iovlen;
-	void *save_iovbase;
-	unsigned int i;
-	int ret;
-
-	if (base == 0)
-		return svc_recvfrom(rqstp, iov, nr, buflen);
-
-	for (i = 0; i < nr; i++) {
-		if (iov[i].iov_len > base)
-			break;
-		base -= iov[i].iov_len;
-	}
-	save_iovlen = iov[i].iov_len;
-	save_iovbase = iov[i].iov_base;
-	iov[i].iov_len -= base;
-	iov[i].iov_base += base;
-	ret = svc_recvfrom(rqstp, &iov[i], nr - i, buflen);
-	iov[i].iov_len = save_iovlen;
-	iov[i].iov_base = save_iovbase;
-	return ret;
-}
-
 /*
  * Set socket snd and rcv buffer lengths
  */
@@ -962,7 +937,8 @@ static int svc_tcp_recv_record(struct svc_sock *svsk, struct svc_rqst *rqstp)
 		want = sizeof(rpc_fraghdr) - svsk->sk_tcplen;
 		iov.iov_base = ((char *) &svsk->sk_reclen) + svsk->sk_tcplen;
 		iov.iov_len  = want;
-		if ((len = svc_recvfrom(rqstp, &iov, 1, want)) < 0)
+		len = svc_recvfrom(rqstp, &iov, 1, want, 0);
+		if (len < 0)
 			goto error;
 		svsk->sk_tcplen += len;
 
@@ -1088,14 +1064,13 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
 
 	vec = rqstp->rq_vec;
 
-	pnum = copy_pages_to_kvecs(&vec[0], &rqstp->rq_pages[0],
-						svsk->sk_datalen + want);
+	pnum = copy_pages_to_kvecs(&vec[0], &rqstp->rq_pages[0], base + want);
 
 	rqstp->rq_respages = &rqstp->rq_pages[pnum];
 	rqstp->rq_next_page = rqstp->rq_respages + 1;
 
 	/* Now receive data */
-	len = svc_partial_recvfrom(rqstp, vec, pnum, want, base);
+	len = svc_recvfrom(rqstp, vec, pnum, base + want, base);
 	if (len >= 0) {
 		svsk->sk_tcplen += len;
 		svsk->sk_datalen += len;
-- 
2.17.1

[PATCH 12/15] knfsd: Remove dead code from nfsd_cache_lookup

[Trond Myklebust]

The preallocated cache entry is always set to type RC_NOCACHE, and that
type isn't changed until we later call nfsd_cache_update().

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfsd/nfscache.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index dbdeb9d6af03..cef4686f87ef 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -446,14 +446,6 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
 	rp->c_csum = csum;
 
 	lru_put_end(b, rp);
-
-	/* release any buffer */
-	if (rp->c_type == RC_REPLBUFF) {
-		drc_mem_usage -= rp->c_replvec.iov_len;
-		kfree(rp->c_replvec.iov_base);
-		rp->c_replvec.iov_base = NULL;
-	}
-	rp->c_type = RC_NOCACHE;
  out:
 	spin_unlock(&b->cache_lock);
 	return rtn;
-- 
2.17.1

[PATCH 13/15] knfsd: Simplify NFS duplicate replay cache

[Trond Myklebust]

Simplify the duplicate replay cache by initialising the preallocated
cache entry, so that we can use it as a key for the cache lookup.

Note that the 99.999% case we want to optimise for is still the one
where the lookup fails, and we have to add this entry to the cache,
so preinitialising should not cause a performance penalty.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfsd/cache.h    |  6 +--
 fs/nfsd/nfscache.c | 94 ++++++++++++++++++++++------------------------
 2 files changed, 47 insertions(+), 53 deletions(-)

diff --git a/fs/nfsd/cache.h b/fs/nfsd/cache.h
index b7559c6f2b97..bd77d5f6fe53 100644
--- a/fs/nfsd/cache.h
+++ b/fs/nfsd/cache.h
@@ -24,13 +24,13 @@ struct svc_cacherep {
 	unsigned char		c_state,	/* unused, inprog, done */
 				c_type,		/* status, buffer */
 				c_secure : 1;	/* req came from port < 1024 */
-	struct sockaddr_in6	c_addr;
 	__be32			c_xid;
-	u32			c_prot;
+	__wsum			c_csum;
 	u32			c_proc;
+	u32			c_prot;
 	u32			c_vers;
 	unsigned int		c_len;
-	__wsum			c_csum;
+	struct sockaddr_in6	c_addr;
 	unsigned long		c_timestamp;
 	union {
 		struct kvec	u_vec;
diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index cef4686f87ef..527ce4c65765 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -121,7 +121,7 @@ nfsd_cache_hash(__be32 xid)
 }
 
 static struct svc_cacherep *
-nfsd_reply_cache_alloc(void)
+nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum)
 {
 	struct svc_cacherep	*rp;
 
@@ -130,6 +130,16 @@ nfsd_reply_cache_alloc(void)
 		rp->c_state = RC_UNUSED;
 		rp->c_type = RC_NOCACHE;
 		INIT_LIST_HEAD(&rp->c_lru);
+
+		rp->c_xid = rqstp->rq_xid;
+		rp->c_proc = rqstp->rq_proc;
+		memset(&rp->c_addr, 0, sizeof(rp->c_addr));
+		rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
+		rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
+		rp->c_prot = rqstp->rq_prot;
+		rp->c_vers = rqstp->rq_vers;
+		rp->c_len = rqstp->rq_arg.len;
+		rp->c_csum = csum;
 	}
 	return rp;
 }
@@ -141,9 +151,11 @@ nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
 		drc_mem_usage -= rp->c_replvec.iov_len;
 		kfree(rp->c_replvec.iov_base);
 	}
-	list_del(&rp->c_lru);
-	atomic_dec(&num_drc_entries);
-	drc_mem_usage -= sizeof(*rp);
+	if (rp->c_state != RC_UNUSED) {
+		list_del(&rp->c_lru);
+		atomic_dec(&num_drc_entries);
+		drc_mem_usage -= sizeof(*rp);
+	}
 	kmem_cache_free(drc_slab, rp);
 }
 
@@ -319,24 +331,23 @@ nfsd_cache_csum(struct svc_rqst *rqstp)
 }
 
 static bool
-nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
+nfsd_cache_match(const struct svc_cacherep *key, const struct svc_cacherep *rp)
 {
 	/* Check RPC XID first */
-	if (rqstp->rq_xid != rp->c_xid)
+	if (key->c_xid != rp->c_xid)
 		return false;
 	/* compare checksum of NFS data */
-	if (csum != rp->c_csum) {
+	if (key->c_csum != rp->c_csum) {
 		++payload_misses;
 		return false;
 	}
 
 	/* Other discriminators */
-	if (rqstp->rq_proc != rp->c_proc ||
-	    rqstp->rq_prot != rp->c_prot ||
-	    rqstp->rq_vers != rp->c_vers ||
-	    rqstp->rq_arg.len != rp->c_len ||
-	    !rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) ||
-	    rpc_get_port(svc_addr(rqstp)) != rpc_get_port((struct sockaddr *)&rp->c_addr))
+	if (key->c_proc != rp->c_proc ||
+	    key->c_prot != rp->c_prot ||
+	    key->c_vers != rp->c_vers ||
+	    key->c_len != rp->c_len ||
+	    memcmp(&key->c_addr, &rp->c_addr, sizeof(key->c_addr)) != 0)
 		return false;
 
 	return true;
@@ -345,19 +356,18 @@ nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
 /*
  * Search the request hash for an entry that matches the given rqstp.
  * Must be called with cache_lock held. Returns the found entry or
- * NULL on failure.
+ * inserts an empty key on failure.
  */
 static struct svc_cacherep *
-nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp,
-		__wsum csum)
+nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key)
 {
-	struct svc_cacherep	*rp, *ret = NULL;
+	struct svc_cacherep	*rp, *ret = key;
 	struct list_head 	*rh = &b->lru_head;
 	unsigned int		entries = 0;
 
 	list_for_each_entry(rp, rh, c_lru) {
 		++entries;
-		if (nfsd_cache_match(rqstp, csum, rp)) {
+		if (nfsd_cache_match(key, rp)) {
 			ret = rp;
 			break;
 		}
@@ -374,6 +384,7 @@ nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp,
 				atomic_read(&num_drc_entries));
 	}
 
+	lru_put_end(b, ret);
 	return ret;
 }
 
@@ -389,9 +400,6 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
 {
 	struct svc_cacherep	*rp, *found;
 	__be32			xid = rqstp->rq_xid;
-	u32			proto =  rqstp->rq_prot,
-				vers = rqstp->rq_vers,
-				proc = rqstp->rq_proc;
 	__wsum			csum;
 	u32 hash = nfsd_cache_hash(xid);
 	struct nfsd_drc_bucket *b = &drc_hashtbl[hash];
@@ -410,52 +418,38 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
 	 * Since the common case is a cache miss followed by an insert,
 	 * preallocate an entry.
 	 */
-	rp = nfsd_reply_cache_alloc();
-	spin_lock(&b->cache_lock);
-	if (likely(rp)) {
-		atomic_inc(&num_drc_entries);
-		drc_mem_usage += sizeof(*rp);
+	rp = nfsd_reply_cache_alloc(rqstp, csum);
+	if (!rp) {
+		dprintk("nfsd: unable to allocate DRC entry!\n");
+		return rtn;
 	}
 
-	/* go ahead and prune the cache */
-	prune_bucket(b);
-
-	found = nfsd_cache_search(b, rqstp, csum);
-	if (found) {
-		if (likely(rp))
-			nfsd_reply_cache_free_locked(rp);
+	spin_lock(&b->cache_lock);
+	found = nfsd_cache_insert(b, rp);
+	if (found != rp) {
+		nfsd_reply_cache_free_locked(rp);
 		rp = found;
 		goto found_entry;
 	}
 
-	if (!rp) {
-		dprintk("nfsd: unable to allocate DRC entry!\n");
-		goto out;
-	}
-
 	nfsdstats.rcmisses++;
 	rqstp->rq_cacherep = rp;
 	rp->c_state = RC_INPROG;
-	rp->c_xid = xid;
-	rp->c_proc = proc;
-	rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
-	rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
-	rp->c_prot = proto;
-	rp->c_vers = vers;
-	rp->c_len = rqstp->rq_arg.len;
-	rp->c_csum = csum;
 
-	lru_put_end(b, rp);
+	atomic_inc(&num_drc_entries);
+	drc_mem_usage += sizeof(*rp);
+
+	/* go ahead and prune the cache */
+	prune_bucket(b);
  out:
 	spin_unlock(&b->cache_lock);
 	return rtn;
 
 found_entry:
-	nfsdstats.rchits++;
 	/* We found a matching entry which is either in progress or done. */
-	lru_put_end(b, rp);
-
+	nfsdstats.rchits++;
 	rtn = RC_DROPIT;
+
 	/* Request being processed */
 	if (rp->c_state == RC_INPROG)
 		goto out;
-- 
2.17.1

[PATCH 14/15] knfsd: Further simplify the cache lookup

[Trond Myklebust]

Order the structure so that the key can be compared using memcmp().

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfsd/cache.h    | 18 ++++++++++--------
 fs/nfsd/nfscache.c | 45 ++++++++++++++++-----------------------------
 2 files changed, 26 insertions(+), 37 deletions(-)

diff --git a/fs/nfsd/cache.h b/fs/nfsd/cache.h
index bd77d5f6fe53..cbcdc15753b7 100644
--- a/fs/nfsd/cache.h
+++ b/fs/nfsd/cache.h
@@ -19,18 +19,20 @@
  * is much larger than a sockaddr_in6.
  */
 struct svc_cacherep {
-	struct list_head	c_lru;
+	struct {
+		__be32			k_xid;
+		__wsum			k_csum;
+		u32			k_proc;
+		u32			k_prot;
+		u32			k_vers;
+		unsigned int		k_len;
+		struct sockaddr_in6	k_addr;
+	} c_key;
 
+	struct list_head	c_lru;
 	unsigned char		c_state,	/* unused, inprog, done */
 				c_type,		/* status, buffer */
 				c_secure : 1;	/* req came from port < 1024 */
-	__be32			c_xid;
-	__wsum			c_csum;
-	u32			c_proc;
-	u32			c_prot;
-	u32			c_vers;
-	unsigned int		c_len;
-	struct sockaddr_in6	c_addr;
 	unsigned long		c_timestamp;
 	union {
 		struct kvec	u_vec;
diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index 527ce4c65765..230cc83921ad 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -131,15 +131,15 @@ nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum)
 		rp->c_type = RC_NOCACHE;
 		INIT_LIST_HEAD(&rp->c_lru);
 
-		rp->c_xid = rqstp->rq_xid;
-		rp->c_proc = rqstp->rq_proc;
-		memset(&rp->c_addr, 0, sizeof(rp->c_addr));
-		rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
-		rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
-		rp->c_prot = rqstp->rq_prot;
-		rp->c_vers = rqstp->rq_vers;
-		rp->c_len = rqstp->rq_arg.len;
-		rp->c_csum = csum;
+		memset(&rp->c_key, 0, sizeof(rp->c_key));
+		rp->c_key.k_xid = rqstp->rq_xid;
+		rp->c_key.k_proc = rqstp->rq_proc;
+		rpc_copy_addr((struct sockaddr *)&rp->c_key.k_addr, svc_addr(rqstp));
+		rpc_set_port((struct sockaddr *)&rp->c_key.k_addr, rpc_get_port(svc_addr(rqstp)));
+		rp->c_key.k_prot = rqstp->rq_prot;
+		rp->c_key.k_vers = rqstp->rq_vers;
+		rp->c_key.k_len = rqstp->rq_arg.len;
+		rp->c_key.k_csum = csum;
 	}
 	return rp;
 }
@@ -330,27 +330,14 @@ nfsd_cache_csum(struct svc_rqst *rqstp)
 	return csum;
 }
 
-static bool
-nfsd_cache_match(const struct svc_cacherep *key, const struct svc_cacherep *rp)
+static int
+nfsd_cache_key_cmp(const struct svc_cacherep *key, const struct svc_cacherep *rp)
 {
-	/* Check RPC XID first */
-	if (key->c_xid != rp->c_xid)
-		return false;
-	/* compare checksum of NFS data */
-	if (key->c_csum != rp->c_csum) {
+	if (key->c_key.k_xid == rp->c_key.k_xid &&
+	    key->c_key.k_csum != rp->c_key.k_csum)
 		++payload_misses;
-		return false;
-	}
-
-	/* Other discriminators */
-	if (key->c_proc != rp->c_proc ||
-	    key->c_prot != rp->c_prot ||
-	    key->c_vers != rp->c_vers ||
-	    key->c_len != rp->c_len ||
-	    memcmp(&key->c_addr, &rp->c_addr, sizeof(key->c_addr)) != 0)
-		return false;
 
-	return true;
+	return memcmp(&key->c_key, &rp->c_key, sizeof(key->c_key));
 }
 
 /*
@@ -367,7 +354,7 @@ nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key)
 
 	list_for_each_entry(rp, rh, c_lru) {
 		++entries;
-		if (nfsd_cache_match(key, rp)) {
+		if (nfsd_cache_key_cmp(key, rp) == 0) {
 			ret = rp;
 			break;
 		}
@@ -510,7 +497,7 @@ nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp)
 	if (!rp)
 		return;
 
-	hash = nfsd_cache_hash(rp->c_xid);
+	hash = nfsd_cache_hash(rp->c_key.k_xid);
 	b = &drc_hashtbl[hash];
 
 	len = resv->iov_len - ((char*)statp - (char*)resv->iov_base);
-- 
2.17.1

[PATCH 15/15] knfsd: Improve lookup performance in the duplicate reply cache using an rbtree

[Trond Myklebust]

Use an rbtree to ensure the lookup/insert of an entry in a DRC bucket is
O(log(N)).

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfsd/cache.h    |  1 +
 fs/nfsd/nfscache.c | 37 ++++++++++++++++++++++++++-----------
 2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/fs/nfsd/cache.h b/fs/nfsd/cache.h
index cbcdc15753b7..ef1c8aa89ca4 100644
--- a/fs/nfsd/cache.h
+++ b/fs/nfsd/cache.h
@@ -29,6 +29,7 @@ struct svc_cacherep {
 		struct sockaddr_in6	k_addr;
 	} c_key;
 
+	struct rb_node		c_node;
 	struct list_head	c_lru;
 	unsigned char		c_state,	/* unused, inprog, done */
 				c_type,		/* status, buffer */
diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index 230cc83921ad..e2fe0e9ce0df 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -30,6 +30,7 @@
 #define TARGET_BUCKET_SIZE	64
 
 struct nfsd_drc_bucket {
+	struct rb_root rb_head;
 	struct list_head lru_head;
 	spinlock_t cache_lock;
 };
@@ -129,6 +130,7 @@ nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum)
 	if (rp) {
 		rp->c_state = RC_UNUSED;
 		rp->c_type = RC_NOCACHE;
+		RB_CLEAR_NODE(&rp->c_node);
 		INIT_LIST_HEAD(&rp->c_lru);
 
 		memset(&rp->c_key, 0, sizeof(rp->c_key));
@@ -145,13 +147,14 @@ nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum)
 }
 
 static void
-nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
+nfsd_reply_cache_free_locked(struct nfsd_drc_bucket *b, struct svc_cacherep *rp)
 {
 	if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) {
 		drc_mem_usage -= rp->c_replvec.iov_len;
 		kfree(rp->c_replvec.iov_base);
 	}
 	if (rp->c_state != RC_UNUSED) {
+		rb_erase(&rp->c_node, &b->rb_head);
 		list_del(&rp->c_lru);
 		atomic_dec(&num_drc_entries);
 		drc_mem_usage -= sizeof(*rp);
@@ -163,7 +166,7 @@ static void
 nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct svc_cacherep *rp)
 {
 	spin_lock(&b->cache_lock);
-	nfsd_reply_cache_free_locked(rp);
+	nfsd_reply_cache_free_locked(b, rp);
 	spin_unlock(&b->cache_lock);
 }
 
@@ -219,7 +222,7 @@ void nfsd_reply_cache_shutdown(void)
 		struct list_head *head = &drc_hashtbl[i].lru_head;
 		while (!list_empty(head)) {
 			rp = list_first_entry(head, struct svc_cacherep, c_lru);
-			nfsd_reply_cache_free_locked(rp);
+			nfsd_reply_cache_free_locked(&drc_hashtbl[i], rp);
 		}
 	}
 
@@ -258,7 +261,7 @@ prune_bucket(struct nfsd_drc_bucket *b)
 		if (atomic_read(&num_drc_entries) <= max_drc_entries &&
 		    time_before(jiffies, rp->c_timestamp + RC_EXPIRE))
 			break;
-		nfsd_reply_cache_free_locked(rp);
+		nfsd_reply_cache_free_locked(b, rp);
 		freed++;
 	}
 	return freed;
@@ -349,17 +352,29 @@ static struct svc_cacherep *
 nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key)
 {
 	struct svc_cacherep	*rp, *ret = key;
-	struct list_head 	*rh = &b->lru_head;
+	struct rb_node		**p = &b->rb_head.rb_node,
+				*parent = NULL;
 	unsigned int		entries = 0;
+	int cmp;
 
-	list_for_each_entry(rp, rh, c_lru) {
+	while (*p != NULL) {
 		++entries;
-		if (nfsd_cache_key_cmp(key, rp) == 0) {
+		parent = *p;
+		rp = rb_entry(parent, struct svc_cacherep, c_node);
+
+		cmp = nfsd_cache_key_cmp(key, rp);
+		if (cmp < 0)
+			p = &parent->rb_left;
+		else if (cmp > 0)
+			p = &parent->rb_right;
+		else {
 			ret = rp;
-			break;
+			goto out;
 		}
 	}
-
+	rb_link_node(&key->c_node, parent, p);
+	rb_insert_color(&key->c_node, &b->rb_head);
+out:
 	/* tally hash chain length stats */
 	if (entries > longest_chain) {
 		longest_chain = entries;
@@ -414,7 +429,7 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
 	spin_lock(&b->cache_lock);
 	found = nfsd_cache_insert(b, rp);
 	if (found != rp) {
-		nfsd_reply_cache_free_locked(rp);
+		nfsd_reply_cache_free_locked(NULL, rp);
 		rp = found;
 		goto found_entry;
 	}
@@ -462,7 +477,7 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
 		break;
 	default:
 		printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type);
-		nfsd_reply_cache_free_locked(rp);
+		nfsd_reply_cache_free_locked(b, rp);
 	}
 
 	goto out;
-- 
2.17.1

Re: [PATCH 15/15] knfsd: Improve lookup performance in the duplicate reply cache using an rbtree

[J . Bruce Fields]

On Mon, Oct 01, 2018 at 10:41:57AM -0400, Trond Myklebust wrote:
> Use an rbtree to ensure the lookup/insert of an entry in a DRC bucket is
> O(log(N)).

So the naming on those hash chain statistics are off now, but I guess
that's harmless.

All looks good to me, thanks--applying.

--b.

> 
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> ---
>  fs/nfsd/cache.h    |  1 +
>  fs/nfsd/nfscache.c | 37 ++++++++++++++++++++++++++-----------
>  2 files changed, 27 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/nfsd/cache.h b/fs/nfsd/cache.h
> index cbcdc15753b7..ef1c8aa89ca4 100644
> --- a/fs/nfsd/cache.h
> +++ b/fs/nfsd/cache.h
> @@ -29,6 +29,7 @@ struct svc_cacherep {
>  		struct sockaddr_in6	k_addr;
>  	} c_key;
>  
> +	struct rb_node		c_node;
>  	struct list_head	c_lru;
>  	unsigned char		c_state,	/* unused, inprog, done */
>  				c_type,		/* status, buffer */
> diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
> index 230cc83921ad..e2fe0e9ce0df 100644
> --- a/fs/nfsd/nfscache.c
> +++ b/fs/nfsd/nfscache.c
> @@ -30,6 +30,7 @@
>  #define TARGET_BUCKET_SIZE	64
>  
>  struct nfsd_drc_bucket {
> +	struct rb_root rb_head;
>  	struct list_head lru_head;
>  	spinlock_t cache_lock;
>  };
> @@ -129,6 +130,7 @@ nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum)
>  	if (rp) {
>  		rp->c_state = RC_UNUSED;
>  		rp->c_type = RC_NOCACHE;
> +		RB_CLEAR_NODE(&rp->c_node);
>  		INIT_LIST_HEAD(&rp->c_lru);
>  
>  		memset(&rp->c_key, 0, sizeof(rp->c_key));
> @@ -145,13 +147,14 @@ nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum)
>  }
>  
>  static void
> -nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
> +nfsd_reply_cache_free_locked(struct nfsd_drc_bucket *b, struct svc_cacherep *rp)
>  {
>  	if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) {
>  		drc_mem_usage -= rp->c_replvec.iov_len;
>  		kfree(rp->c_replvec.iov_base);
>  	}
>  	if (rp->c_state != RC_UNUSED) {
> +		rb_erase(&rp->c_node, &b->rb_head);
>  		list_del(&rp->c_lru);
>  		atomic_dec(&num_drc_entries);
>  		drc_mem_usage -= sizeof(*rp);
> @@ -163,7 +166,7 @@ static void
>  nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct svc_cacherep *rp)
>  {
>  	spin_lock(&b->cache_lock);
> -	nfsd_reply_cache_free_locked(rp);
> +	nfsd_reply_cache_free_locked(b, rp);
>  	spin_unlock(&b->cache_lock);
>  }
>  
> @@ -219,7 +222,7 @@ void nfsd_reply_cache_shutdown(void)
>  		struct list_head *head = &drc_hashtbl[i].lru_head;
>  		while (!list_empty(head)) {
>  			rp = list_first_entry(head, struct svc_cacherep, c_lru);
> -			nfsd_reply_cache_free_locked(rp);
> +			nfsd_reply_cache_free_locked(&drc_hashtbl[i], rp);
>  		}
>  	}
>  
> @@ -258,7 +261,7 @@ prune_bucket(struct nfsd_drc_bucket *b)
>  		if (atomic_read(&num_drc_entries) <= max_drc_entries &&
>  		    time_before(jiffies, rp->c_timestamp + RC_EXPIRE))
>  			break;
> -		nfsd_reply_cache_free_locked(rp);
> +		nfsd_reply_cache_free_locked(b, rp);
>  		freed++;
>  	}
>  	return freed;
> @@ -349,17 +352,29 @@ static struct svc_cacherep *
>  nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key)
>  {
>  	struct svc_cacherep	*rp, *ret = key;
> -	struct list_head 	*rh = &b->lru_head;
> +	struct rb_node		**p = &b->rb_head.rb_node,
> +				*parent = NULL;
>  	unsigned int		entries = 0;
> +	int cmp;
>  
> -	list_for_each_entry(rp, rh, c_lru) {
> +	while (*p != NULL) {
>  		++entries;
> -		if (nfsd_cache_key_cmp(key, rp) == 0) {
> +		parent = *p;
> +		rp = rb_entry(parent, struct svc_cacherep, c_node);
> +
> +		cmp = nfsd_cache_key_cmp(key, rp);
> +		if (cmp < 0)
> +			p = &parent->rb_left;
> +		else if (cmp > 0)
> +			p = &parent->rb_right;
> +		else {
>  			ret = rp;
> -			break;
> +			goto out;
>  		}
>  	}
> -
> +	rb_link_node(&key->c_node, parent, p);
> +	rb_insert_color(&key->c_node, &b->rb_head);
> +out:
>  	/* tally hash chain length stats */
>  	if (entries > longest_chain) {
>  		longest_chain = entries;
> @@ -414,7 +429,7 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
>  	spin_lock(&b->cache_lock);
>  	found = nfsd_cache_insert(b, rp);
>  	if (found != rp) {
> -		nfsd_reply_cache_free_locked(rp);
> +		nfsd_reply_cache_free_locked(NULL, rp);
>  		rp = found;
>  		goto found_entry;
>  	}
> @@ -462,7 +477,7 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
>  		break;
>  	default:
>  		printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type);
> -		nfsd_reply_cache_free_locked(rp);
> +		nfsd_reply_cache_free_locked(b, rp);
>  	}
>  
>  	goto out;
> -- 
> 2.17.1

Re: [PATCH 13/15] knfsd: Simplify NFS duplicate replay cache

[J . Bruce Fields]

On Mon, Oct 01, 2018 at 10:41:55AM -0400, Trond Myklebust wrote:
> Simplify the duplicate replay cache by initialising the preallocated
> cache entry, so that we can use it as a key for the cache lookup.
> 
> Note that the 99.999% case we want to optimise for is still the one
> where the lookup fails, and we have to add this entry to the cache,
> so preinitialising should not cause a performance penalty.
> 
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> ---
>  fs/nfsd/cache.h    |  6 +--
>  fs/nfsd/nfscache.c | 94 ++++++++++++++++++++++------------------------
>  2 files changed, 47 insertions(+), 53 deletions(-)
> 
> diff --git a/fs/nfsd/cache.h b/fs/nfsd/cache.h
> index b7559c6f2b97..bd77d5f6fe53 100644
> --- a/fs/nfsd/cache.h
> +++ b/fs/nfsd/cache.h
> @@ -24,13 +24,13 @@ struct svc_cacherep {
>  	unsigned char		c_state,	/* unused, inprog, done */
>  				c_type,		/* status, buffer */
>  				c_secure : 1;	/* req came from port < 1024 */
> -	struct sockaddr_in6	c_addr;
>  	__be32			c_xid;
> -	u32			c_prot;
> +	__wsum			c_csum;
>  	u32			c_proc;
> +	u32			c_prot;
>  	u32			c_vers;
>  	unsigned int		c_len;
> -	__wsum			c_csum;
> +	struct sockaddr_in6	c_addr;
>  	unsigned long		c_timestamp;
>  	union {
>  		struct kvec	u_vec;

Unless I've missed something subtle--I'll move this chunk into the next
patch.--b.

> diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
> index cef4686f87ef..527ce4c65765 100644
> --- a/fs/nfsd/nfscache.c
> +++ b/fs/nfsd/nfscache.c
> @@ -121,7 +121,7 @@ nfsd_cache_hash(__be32 xid)
>  }
>  
>  static struct svc_cacherep *
> -nfsd_reply_cache_alloc(void)
> +nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum)
>  {
>  	struct svc_cacherep	*rp;
>  
> @@ -130,6 +130,16 @@ nfsd_reply_cache_alloc(void)
>  		rp->c_state = RC_UNUSED;
>  		rp->c_type = RC_NOCACHE;
>  		INIT_LIST_HEAD(&rp->c_lru);
> +
> +		rp->c_xid = rqstp->rq_xid;
> +		rp->c_proc = rqstp->rq_proc;
> +		memset(&rp->c_addr, 0, sizeof(rp->c_addr));
> +		rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
> +		rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
> +		rp->c_prot = rqstp->rq_prot;
> +		rp->c_vers = rqstp->rq_vers;
> +		rp->c_len = rqstp->rq_arg.len;
> +		rp->c_csum = csum;
>  	}
>  	return rp;
>  }
> @@ -141,9 +151,11 @@ nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
>  		drc_mem_usage -= rp->c_replvec.iov_len;
>  		kfree(rp->c_replvec.iov_base);
>  	}
> -	list_del(&rp->c_lru);
> -	atomic_dec(&num_drc_entries);
> -	drc_mem_usage -= sizeof(*rp);
> +	if (rp->c_state != RC_UNUSED) {
> +		list_del(&rp->c_lru);
> +		atomic_dec(&num_drc_entries);
> +		drc_mem_usage -= sizeof(*rp);
> +	}
>  	kmem_cache_free(drc_slab, rp);
>  }
>  
> @@ -319,24 +331,23 @@ nfsd_cache_csum(struct svc_rqst *rqstp)
>  }
>  
>  static bool
> -nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
> +nfsd_cache_match(const struct svc_cacherep *key, const struct svc_cacherep *rp)
>  {
>  	/* Check RPC XID first */
> -	if (rqstp->rq_xid != rp->c_xid)
> +	if (key->c_xid != rp->c_xid)
>  		return false;
>  	/* compare checksum of NFS data */
> -	if (csum != rp->c_csum) {
> +	if (key->c_csum != rp->c_csum) {
>  		++payload_misses;
>  		return false;
>  	}
>  
>  	/* Other discriminators */
> -	if (rqstp->rq_proc != rp->c_proc ||
> -	    rqstp->rq_prot != rp->c_prot ||
> -	    rqstp->rq_vers != rp->c_vers ||
> -	    rqstp->rq_arg.len != rp->c_len ||
> -	    !rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) ||
> -	    rpc_get_port(svc_addr(rqstp)) != rpc_get_port((struct sockaddr *)&rp->c_addr))
> +	if (key->c_proc != rp->c_proc ||
> +	    key->c_prot != rp->c_prot ||
> +	    key->c_vers != rp->c_vers ||
> +	    key->c_len != rp->c_len ||
> +	    memcmp(&key->c_addr, &rp->c_addr, sizeof(key->c_addr)) != 0)
>  		return false;
>  
>  	return true;
> @@ -345,19 +356,18 @@ nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
>  /*
>   * Search the request hash for an entry that matches the given rqstp.
>   * Must be called with cache_lock held. Returns the found entry or
> - * NULL on failure.
> + * inserts an empty key on failure.
>   */
>  static struct svc_cacherep *
> -nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp,
> -		__wsum csum)
> +nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key)
>  {
> -	struct svc_cacherep	*rp, *ret = NULL;
> +	struct svc_cacherep	*rp, *ret = key;
>  	struct list_head 	*rh = &b->lru_head;
>  	unsigned int		entries = 0;
>  
>  	list_for_each_entry(rp, rh, c_lru) {
>  		++entries;
> -		if (nfsd_cache_match(rqstp, csum, rp)) {
> +		if (nfsd_cache_match(key, rp)) {
>  			ret = rp;
>  			break;
>  		}
> @@ -374,6 +384,7 @@ nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp,
>  				atomic_read(&num_drc_entries));
>  	}
>  
> +	lru_put_end(b, ret);
>  	return ret;
>  }
>  
> @@ -389,9 +400,6 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
>  {
>  	struct svc_cacherep	*rp, *found;
>  	__be32			xid = rqstp->rq_xid;
> -	u32			proto =  rqstp->rq_prot,
> -				vers = rqstp->rq_vers,
> -				proc = rqstp->rq_proc;
>  	__wsum			csum;
>  	u32 hash = nfsd_cache_hash(xid);
>  	struct nfsd_drc_bucket *b = &drc_hashtbl[hash];
> @@ -410,52 +418,38 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
>  	 * Since the common case is a cache miss followed by an insert,
>  	 * preallocate an entry.
>  	 */
> -	rp = nfsd_reply_cache_alloc();
> -	spin_lock(&b->cache_lock);
> -	if (likely(rp)) {
> -		atomic_inc(&num_drc_entries);
> -		drc_mem_usage += sizeof(*rp);
> +	rp = nfsd_reply_cache_alloc(rqstp, csum);
> +	if (!rp) {
> +		dprintk("nfsd: unable to allocate DRC entry!\n");
> +		return rtn;
>  	}
>  
> -	/* go ahead and prune the cache */
> -	prune_bucket(b);
> -
> -	found = nfsd_cache_search(b, rqstp, csum);
> -	if (found) {
> -		if (likely(rp))
> -			nfsd_reply_cache_free_locked(rp);
> +	spin_lock(&b->cache_lock);
> +	found = nfsd_cache_insert(b, rp);
> +	if (found != rp) {
> +		nfsd_reply_cache_free_locked(rp);
>  		rp = found;
>  		goto found_entry;
>  	}
>  
> -	if (!rp) {
> -		dprintk("nfsd: unable to allocate DRC entry!\n");
> -		goto out;
> -	}
> -
>  	nfsdstats.rcmisses++;
>  	rqstp->rq_cacherep = rp;
>  	rp->c_state = RC_INPROG;
> -	rp->c_xid = xid;
> -	rp->c_proc = proc;
> -	rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
> -	rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
> -	rp->c_prot = proto;
> -	rp->c_vers = vers;
> -	rp->c_len = rqstp->rq_arg.len;
> -	rp->c_csum = csum;
>  
> -	lru_put_end(b, rp);
> +	atomic_inc(&num_drc_entries);
> +	drc_mem_usage += sizeof(*rp);
> +
> +	/* go ahead and prune the cache */
> +	prune_bucket(b);
>   out:
>  	spin_unlock(&b->cache_lock);
>  	return rtn;
>  
>  found_entry:
> -	nfsdstats.rchits++;
>  	/* We found a matching entry which is either in progress or done. */
> -	lru_put_end(b, rp);
> -
> +	nfsdstats.rchits++;
>  	rtn = RC_DROPIT;
> +
>  	/* Request being processed */
>  	if (rp->c_state == RC_INPROG)
>  		goto out;
> -- 
> 2.17.1

Re: [PATCH 13/15] knfsd: Simplify NFS duplicate replay cache

[Trond Myklebust]

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Re: [PATCH 13/15] knfsd: Simplify NFS duplicate replay cache

[bfields]

On Wed, Oct 03, 2018 at 06:01:36PM +0000, Trond Myklebust wrote:
> On Wed, 2018-10-03 at 13:14 -0400, J . Bruce Fields wrote:
> > On Mon, Oct 01, 2018 at 10:41:55AM -0400, Trond Myklebust wrote:
> > > Simplify the duplicate replay cache by initialising the
> > > preallocated
> > > cache entry, so that we can use it as a key for the cache lookup.
> > > 
> > > Note that the 99.999% case we want to optimise for is still the one
> > > where the lookup fails, and we have to add this entry to the cache,
> > > so preinitialising should not cause a performance penalty.
> > > 
> > > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> > > ---
> > >  fs/nfsd/cache.h    |  6 +--
> > >  fs/nfsd/nfscache.c | 94 ++++++++++++++++++++++------------------
> > > ------
> > >  2 files changed, 47 insertions(+), 53 deletions(-)
> > > 
> > > diff --git a/fs/nfsd/cache.h b/fs/nfsd/cache.h
> > > index b7559c6f2b97..bd77d5f6fe53 100644
> > > --- a/fs/nfsd/cache.h
> > > +++ b/fs/nfsd/cache.h
> > > @@ -24,13 +24,13 @@ struct svc_cacherep {
> > >  	unsigned char		c_state,	/* unused, inprog,
> > > done */
> > >  				c_type,		/* status, buffer
> > > */
> > >  				c_secure : 1;	/* req came from
> > > port < 1024 */
> > > -	struct sockaddr_in6	c_addr;
> > >  	__be32			c_xid;
> > > -	u32			c_prot;
> > > +	__wsum			c_csum;
> > >  	u32			c_proc;
> > > +	u32			c_prot;
> > >  	u32			c_vers;
> > >  	unsigned int		c_len;
> > > -	__wsum			c_csum;
> > > +	struct sockaddr_in6	c_addr;
> > >  	unsigned long		c_timestamp;
> > >  	union {
> > >  		struct kvec	u_vec;
> > 
> > Unless I've missed something subtle--I'll move this chunk into the
> > next
> > patch.--b.
> 
> Nothing too subtle. The only reason for keeping it in this patch is
> because even with the current code, most of the comparisons hit the
> c_xid and possibly sometimes the c_csum, so those are the main fields
> that you want to try to keep in the same cache line.

That could use a comment.

--b.

Re: [PATCH 13/15] knfsd: Simplify NFS duplicate replay cache

[bfields]

On Wed, Oct 03, 2018 at 02:11:50PM -0400, bfields@fieldses.org wrote:
> On Wed, Oct 03, 2018 at 06:01:36PM +0000, Trond Myklebust wrote:
> > On Wed, 2018-10-03 at 13:14 -0400, J . Bruce Fields wrote:
> > > On Mon, Oct 01, 2018 at 10:41:55AM -0400, Trond Myklebust wrote:
> > > > Simplify the duplicate replay cache by initialising the
> > > > preallocated
> > > > cache entry, so that we can use it as a key for the cache lookup.
> > > > 
> > > > Note that the 99.999% case we want to optimise for is still the one
> > > > where the lookup fails, and we have to add this entry to the cache,
> > > > so preinitialising should not cause a performance penalty.
> > > > 
> > > > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> > > > ---
> > > >  fs/nfsd/cache.h    |  6 +--
> > > >  fs/nfsd/nfscache.c | 94 ++++++++++++++++++++++------------------
> > > > ------
> > > >  2 files changed, 47 insertions(+), 53 deletions(-)
> > > > 
> > > > diff --git a/fs/nfsd/cache.h b/fs/nfsd/cache.h
> > > > index b7559c6f2b97..bd77d5f6fe53 100644
> > > > --- a/fs/nfsd/cache.h
> > > > +++ b/fs/nfsd/cache.h
> > > > @@ -24,13 +24,13 @@ struct svc_cacherep {
> > > >  	unsigned char		c_state,	/* unused, inprog,
> > > > done */
> > > >  				c_type,		/* status, buffer
> > > > */
> > > >  				c_secure : 1;	/* req came from
> > > > port < 1024 */
> > > > -	struct sockaddr_in6	c_addr;
> > > >  	__be32			c_xid;
> > > > -	u32			c_prot;
> > > > +	__wsum			c_csum;
> > > >  	u32			c_proc;
> > > > +	u32			c_prot;
> > > >  	u32			c_vers;
> > > >  	unsigned int		c_len;
> > > > -	__wsum			c_csum;
> > > > +	struct sockaddr_in6	c_addr;
> > > >  	unsigned long		c_timestamp;
> > > >  	union {
> > > >  		struct kvec	u_vec;
> > > 
> > > Unless I've missed something subtle--I'll move this chunk into the
> > > next
> > > patch.--b.
> > 
> > Nothing too subtle. The only reason for keeping it in this patch is
> > because even with the current code, most of the comparisons hit the
> > c_xid and possibly sometimes the c_csum, so those are the main fields
> > that you want to try to keep in the same cache line.
> 
> That could use a comment.

I'm adding just

 struct svc_cacherep {
 	struct {
+		/* Keep often-read xid, csum in the same cache line: */
 		__be32			k_xid;
 		__wsum			k_csum;
 		u32			k_proc;

--b.

Re: [PATCH 08/15] NFS: Lockless DNS lookups

[J . Bruce Fields]

The individual conversions of these caches looks straightforward to me.
Thanks for doing this in these small steps.  I'm assuming you're OK with
these nfs/ changes going through the nfsd tree.

--b.

On Mon, Oct 01, 2018 at 10:41:50AM -0400, Trond Myklebust wrote:
> Enable RCU protected lookup in the legacy DNS resolver.
> 
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> ---
>  fs/nfs/dns_resolve.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
> index 060c658eab66..e93a5dc07c8c 100644
> --- a/fs/nfs/dns_resolve.c
> +++ b/fs/nfs/dns_resolve.c
> @@ -65,6 +65,7 @@ struct nfs_dns_ent {
>  
>  	struct sockaddr_storage addr;
>  	size_t addrlen;
> +	struct rcu_head rcu_head;
>  };
>  
>  
> @@ -101,15 +102,23 @@ static void nfs_dns_ent_init(struct cache_head *cnew,
>  	}
>  }
>  
> -static void nfs_dns_ent_put(struct kref *ref)
> +static void nfs_dns_ent_free_rcu(struct rcu_head *head)
>  {
>  	struct nfs_dns_ent *item;
>  
> -	item = container_of(ref, struct nfs_dns_ent, h.ref);
> +	item = container_of(head, struct nfs_dns_ent, rcu_head);
>  	kfree(item->hostname);
>  	kfree(item);
>  }
>  
> +static void nfs_dns_ent_put(struct kref *ref)
> +{
> +	struct nfs_dns_ent *item;
> +
> +	item = container_of(ref, struct nfs_dns_ent, h.ref);
> +	call_rcu(item, nfs_dns_ent_free_rcu);
> +}
> +
>  static struct cache_head *nfs_dns_ent_alloc(void)
>  {
>  	struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
> @@ -195,7 +204,7 @@ static struct nfs_dns_ent *nfs_dns_lookup(struct cache_detail *cd,
>  {
>  	struct cache_head *ch;
>  
> -	ch = sunrpc_cache_lookup(cd,
> +	ch = sunrpc_cache_lookup_rcu(cd,
>  			&key->h,
>  			nfs_dns_hash(key));
>  	if (!ch)
> -- 
> 2.17.1

Re: [PATCH 08/15] NFS: Lockless DNS lookups

[Trond Myklebust]

On Wed, 2018-10-03 at 12:10 -0400, J . Bruce Fields wrote:
> The individual conversions of these caches looks straightforward to
> me.
> Thanks for doing this in these small steps.  I'm assuming you're OK
> with
> these nfs/ changes going through the nfsd tree.
> 

Yes please. With the bulk of the changes being nfsd specific, that
makes more sense to me.

> --b.
> 
> On Mon, Oct 01, 2018 at 10:41:50AM -0400, Trond Myklebust wrote:
> > Enable RCU protected lookup in the legacy DNS resolver.
> > 
> > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> > ---
> >  fs/nfs/dns_resolve.c | 15 ++++++++++++---
> >  1 file changed, 12 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
> > index 060c658eab66..e93a5dc07c8c 100644
> > --- a/fs/nfs/dns_resolve.c
> > +++ b/fs/nfs/dns_resolve.c
> > @@ -65,6 +65,7 @@ struct nfs_dns_ent {
> >  
> >  	struct sockaddr_storage addr;
> >  	size_t addrlen;
> > +	struct rcu_head rcu_head;
> >  };
> >  
> >  
> > @@ -101,15 +102,23 @@ static void nfs_dns_ent_init(struct
> > cache_head *cnew,
> >  	}
> >  }
> >  
> > -static void nfs_dns_ent_put(struct kref *ref)
> > +static void nfs_dns_ent_free_rcu(struct rcu_head *head)
> >  {
> >  	struct nfs_dns_ent *item;
> >  
> > -	item = container_of(ref, struct nfs_dns_ent, h.ref);
> > +	item = container_of(head, struct nfs_dns_ent, rcu_head);
> >  	kfree(item->hostname);
> >  	kfree(item);
> >  }
> >  
> > +static void nfs_dns_ent_put(struct kref *ref)
> > +{
> > +	struct nfs_dns_ent *item;
> > +
> > +	item = container_of(ref, struct nfs_dns_ent, h.ref);
> > +	call_rcu(item, nfs_dns_ent_free_rcu);
> > +}
> > +
> >  static struct cache_head *nfs_dns_ent_alloc(void)
> >  {
> >  	struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
> > @@ -195,7 +204,7 @@ static struct nfs_dns_ent
> > *nfs_dns_lookup(struct cache_detail *cd,
> >  {
> >  	struct cache_head *ch;
> >  
> > -	ch = sunrpc_cache_lookup(cd,
> > +	ch = sunrpc_cache_lookup_rcu(cd,
> >  			&key->h,
> >  			nfs_dns_hash(key));
> >  	if (!ch)
> > -- 
> > 2.17.1

Re: [PATCH 03/15] SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock

[J . Bruce Fields]

On Mon, Oct 01, 2018 at 10:41:45AM -0400, Trond Myklebust wrote:
> Instead of the reader/writer spinlock, allow cache lookups to use RCU
> for looking up entries. This is more efficient since modifications can
> occur while other entries are being looked up.
> 
> Note that for now, we keep the reader/writer spinlock until all users
> have been converted to use RCU-safe freeing of their cache entries.

This one's a bit easier for me to review if I separate out find/add
split from the interesting part.

Looks good to me, applying as follows:

--b.

commit b92a8fababa9
Author: Trond Myklebust <trondmy@gmail.com>
Date:   Mon Oct 1 10:41:45 2018 -0400

    SUNRPC: Refactor sunrpc_cache_lookup
    
    This is a trivial split into lookup and insert functions, no change in
    behavior.
    
    Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 109fbe591e7b..aa8e62d61f4d 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -54,13 +54,11 @@ static void cache_init(struct cache_head *h, struct cache_detail *detail)
 	h->last_refresh = now;
 }
 
-struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
-				       struct cache_head *key, int hash)
+static struct cache_head *sunrpc_cache_find(struct cache_detail *detail,
+					    struct cache_head *key, int hash)
 {
-	struct cache_head *new = NULL, *freeme = NULL, *tmp = NULL;
-	struct hlist_head *head;
-
-	head = &detail->hash_table[hash];
+	struct hlist_head *head = &detail->hash_table[hash];
+	struct cache_head *tmp;
 
 	read_lock(&detail->hash_lock);
 
@@ -75,7 +73,15 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
 		}
 	}
 	read_unlock(&detail->hash_lock);
-	/* Didn't find anything, insert an empty entry */
+	return NULL;
+}
+
+static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
+						 struct cache_head *key,
+						 int hash)
+{
+	struct cache_head *new, *tmp, *freeme = NULL;
+	struct hlist_head *head = &detail->hash_table[hash];
 
 	new = detail->alloc();
 	if (!new)
@@ -114,8 +120,19 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
 		cache_put(freeme, detail);
 	return new;
 }
-EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);
 
+struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
+				       struct cache_head *key, int hash)
+{
+	struct cache_head *ret;
+
+	ret = sunrpc_cache_find(detail, key, hash);
+	if (ret)
+		return ret;
+	/* Didn't find anything, insert an empty entry */
+	return sunrpc_cache_add_entry(detail, key, hash);
+}
+EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);
 
 static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch);
 
commit b0e4dad04223
Author: J. Bruce Fields <bfields@redhat.com>
Date:   Wed Oct 3 12:01:22 2018 -0400

    SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock
    
    Instead of the reader/writer spinlock, allow cache lookups to use RCU
    for looking up entries. This is more efficient since modifications can
    occur while other entries are being looked up.
    
    Note that for now, we keep the reader/writer spinlock until all users
    have been converted to use RCU-safe freeing of their cache entries.
    
    Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index 40d2822f0e2f..cf3e17ee2786 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -167,6 +167,9 @@ extern const struct file_operations cache_file_operations_pipefs;
 extern const struct file_operations content_file_operations_pipefs;
 extern const struct file_operations cache_flush_operations_pipefs;
 
+extern struct cache_head *
+sunrpc_cache_lookup_rcu(struct cache_detail *detail,
+			struct cache_head *key, int hash);
 extern struct cache_head *
 sunrpc_cache_lookup(struct cache_detail *detail,
 		    struct cache_head *key, int hash);
@@ -186,6 +189,12 @@ static inline struct cache_head  *cache_get(struct cache_head *h)
 	return h;
 }
 
+static inline struct cache_head  *cache_get_rcu(struct cache_head *h)
+{
+	if (kref_get_unless_zero(&h->ref))
+		return h;
+	return NULL;
+}
 
 static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
 {
@@ -227,6 +236,9 @@ extern void sunrpc_cache_unhash(struct cache_detail *, struct cache_head *);
 extern void *cache_seq_start(struct seq_file *file, loff_t *pos);
 extern void *cache_seq_next(struct seq_file *file, void *p, loff_t *pos);
 extern void cache_seq_stop(struct seq_file *file, void *p);
+extern void *cache_seq_start_rcu(struct seq_file *file, loff_t *pos);
+extern void *cache_seq_next_rcu(struct seq_file *file, void *p, loff_t *pos);
+extern void cache_seq_stop_rcu(struct seq_file *file, void *p);
 
 extern void qword_add(char **bpp, int *lp, char *str);
 extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index aa8e62d61f4d..7593afed9036 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -54,6 +54,27 @@ static void cache_init(struct cache_head *h, struct cache_detail *detail)
 	h->last_refresh = now;
 }
 
+static struct cache_head *sunrpc_cache_find_rcu(struct cache_detail *detail,
+						struct cache_head *key,
+						int hash)
+{
+	struct hlist_head *head = &detail->hash_table[hash];
+	struct cache_head *tmp;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(tmp, head, cache_list) {
+		if (detail->match(tmp, key)) {
+			if (cache_is_expired(detail, tmp))
+				continue;
+			tmp = cache_get_rcu(tmp);
+			rcu_read_unlock();
+			return tmp;
+		}
+	}
+	rcu_read_unlock();
+	return NULL;
+}
+
 static struct cache_head *sunrpc_cache_find(struct cache_detail *detail,
 					    struct cache_head *key, int hash)
 {
@@ -61,7 +82,6 @@ static struct cache_head *sunrpc_cache_find(struct cache_detail *detail,
 	struct cache_head *tmp;
 
 	read_lock(&detail->hash_lock);
-
 	hlist_for_each_entry(tmp, head, cache_list) {
 		if (detail->match(tmp, key)) {
 			if (cache_is_expired(detail, tmp))
@@ -96,10 +116,10 @@ static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
 	write_lock(&detail->hash_lock);
 
 	/* check if entry appeared while we slept */
-	hlist_for_each_entry(tmp, head, cache_list) {
+	hlist_for_each_entry_rcu(tmp, head, cache_list) {
 		if (detail->match(tmp, key)) {
 			if (cache_is_expired(detail, tmp)) {
-				hlist_del_init(&tmp->cache_list);
+				hlist_del_init_rcu(&tmp->cache_list);
 				detail->entries --;
 				freeme = tmp;
 				break;
@@ -111,7 +131,7 @@ static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
 		}
 	}
 
-	hlist_add_head(&new->cache_list, head);
+	hlist_add_head_rcu(&new->cache_list, head);
 	detail->entries++;
 	cache_get(new);
 	write_unlock(&detail->hash_lock);
@@ -121,6 +141,19 @@ static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
 	return new;
 }
 
+struct cache_head *sunrpc_cache_lookup_rcu(struct cache_detail *detail,
+					   struct cache_head *key, int hash)
+{
+	struct cache_head *ret;
+
+	ret = sunrpc_cache_find_rcu(detail, key, hash);
+	if (ret)
+		return ret;
+	/* Didn't find anything, insert an empty entry */
+	return sunrpc_cache_add_entry(detail, key, hash);
+}
+EXPORT_SYMBOL_GPL(sunrpc_cache_lookup_rcu);
+
 struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
 				       struct cache_head *key, int hash)
 {
@@ -134,6 +167,7 @@ struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);
 
+
 static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch);
 
 static void cache_fresh_locked(struct cache_head *head, time_t expiry,
@@ -450,7 +484,7 @@ static int cache_clean(void)
 			if (!cache_is_expired(current_detail, ch))
 				continue;
 
-			hlist_del_init(&ch->cache_list);
+			hlist_del_init_rcu(&ch->cache_list);
 			current_detail->entries--;
 			rv = 1;
 			break;
@@ -521,7 +555,7 @@ void cache_purge(struct cache_detail *detail)
 	for (i = 0; i < detail->hash_size; i++) {
 		head = &detail->hash_table[i];
 		hlist_for_each_entry_safe(ch, tmp, head, cache_list) {
-			hlist_del_init(&ch->cache_list);
+			hlist_del_init_rcu(&ch->cache_list);
 			detail->entries--;
 
 			set_bit(CACHE_CLEANED, &ch->flags);
@@ -1306,21 +1340,19 @@ EXPORT_SYMBOL_GPL(qword_get);
  * get a header, then pass each real item in the cache
  */
 
-void *cache_seq_start(struct seq_file *m, loff_t *pos)
-	__acquires(cd->hash_lock)
+static void *__cache_seq_start(struct seq_file *m, loff_t *pos)
 {
 	loff_t n = *pos;
 	unsigned int hash, entry;
 	struct cache_head *ch;
 	struct cache_detail *cd = m->private;
 
-	read_lock(&cd->hash_lock);
 	if (!n--)
 		return SEQ_START_TOKEN;
 	hash = n >> 32;
 	entry = n & ((1LL<<32) - 1);
 
-	hlist_for_each_entry(ch, &cd->hash_table[hash], cache_list)
+	hlist_for_each_entry_rcu(ch, &cd->hash_table[hash], cache_list)
 		if (!entry--)
 			return ch;
 	n &= ~((1LL<<32) - 1);
@@ -1332,9 +1364,19 @@ void *cache_seq_start(struct seq_file *m, loff_t *pos)
 	if (hash >= cd->hash_size)
 		return NULL;
 	*pos = n+1;
-	return hlist_entry_safe(cd->hash_table[hash].first,
+	return hlist_entry_safe(rcu_dereference_raw(
+				hlist_first_rcu(&cd->hash_table[hash])),
 				struct cache_head, cache_list);
 }
+
+void *cache_seq_start(struct seq_file *m, loff_t *pos)
+	__acquires(cd->hash_lock)
+{
+	struct cache_detail *cd = m->private;
+
+	read_lock(&cd->hash_lock);
+	return __cache_seq_start(m, pos);
+}
 EXPORT_SYMBOL_GPL(cache_seq_start);
 
 void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
@@ -1350,7 +1392,8 @@ void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
 		*pos += 1LL<<32;
 	} else {
 		++*pos;
-		return hlist_entry_safe(ch->cache_list.next,
+		return hlist_entry_safe(rcu_dereference_raw(
+					hlist_next_rcu(&ch->cache_list)),
 					struct cache_head, cache_list);
 	}
 	*pos &= ~((1LL<<32) - 1);
@@ -1362,7 +1405,8 @@ void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
 	if (hash >= cd->hash_size)
 		return NULL;
 	++*pos;
-	return hlist_entry_safe(cd->hash_table[hash].first,
+	return hlist_entry_safe(rcu_dereference_raw(
+				hlist_first_rcu(&cd->hash_table[hash])),
 				struct cache_head, cache_list);
 }
 EXPORT_SYMBOL_GPL(cache_seq_next);
@@ -1375,6 +1419,27 @@ void cache_seq_stop(struct seq_file *m, void *p)
 }
 EXPORT_SYMBOL_GPL(cache_seq_stop);
 
+void *cache_seq_start_rcu(struct seq_file *m, loff_t *pos)
+	__acquires(RCU)
+{
+	rcu_read_lock();
+	return __cache_seq_start(m, pos);
+}
+EXPORT_SYMBOL_GPL(cache_seq_start_rcu);
+
+void *cache_seq_next_rcu(struct seq_file *file, void *p, loff_t *pos)
+{
+	return cache_seq_next(file, p, pos);
+}
+EXPORT_SYMBOL_GPL(cache_seq_next_rcu);
+
+void cache_seq_stop_rcu(struct seq_file *m, void *p)
+	__releases(RCU)
+{
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(cache_seq_stop_rcu);
+
 static int c_show(struct seq_file *m, void *p)
 {
 	struct cache_head *cp = p;
@@ -1863,7 +1928,7 @@ void sunrpc_cache_unhash(struct cache_detail *cd, struct cache_head *h)
 {
 	write_lock(&cd->hash_lock);
 	if (!hlist_unhashed(&h->cache_list)){
-		hlist_del_init(&h->cache_list);
+		hlist_del_init_rcu(&h->cache_list);
 		cd->entries--;
 		write_unlock(&cd->hash_lock);
 		cache_put(h, cd);

Re: [PATCH 01/15] SUNRPC: Remove the server 'authtab_lock' and just use RCU

[J . Bruce Fields]

On Mon, Oct 01, 2018 at 10:41:43AM -0400, Trond Myklebust wrote:
> 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,

I didn't know about "__rcu" and "__force __rcu".  Grepping turns up
relevant documentation for RCU_INIT_POINTER in include/linux/rcupdate.h,
OK, I think I get it.--b.

>  };
>  
> +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

Re: [PATCH 00/15] Performance improvements for knfsd

[Trond Myklebust]

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