NFS: Lockless DNS lookups

trondmy · J. Bruce Fields · commit 437f91451349 · 2018-10-29T16:58:04.000-04:00
Enable RCU protected lookup in the legacy DNS resolver.

Signed-off-by: Trond Myklebust &lt;trond.myklebust@hammerspace.com&gt;
Signed-off-by: J. Bruce Fields &lt;bfields@redhat.com&gt;
diff --git 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)

Original file line number	Diff line number	Diff line change
`@@ -65,6 +65,7 @@ struct nfs_dns_ent {`
`65`	`65`
`66`	`66`	`struct sockaddr_storage addr;`
`67`	`67`	`size_t addrlen;`
	`68`	`+ struct rcu_head rcu_head;`
`68`	`69`	`};`
`69`	`70`
`70`	`71`
`@@ -101,15 +102,23 @@ static void nfs_dns_ent_init(struct cache_head *cnew,`
`101`	`102`	`}`
`102`	`103`	`}`
`103`	`104`
`104`		`-static void nfs_dns_ent_put(struct kref *ref)`
	`105`	`+static void nfs_dns_ent_free_rcu(struct rcu_head *head)`
`105`	`106`	`{`
`106`	`107`	`struct nfs_dns_ent *item;`
`107`	`108`
`108`		`- item = container_of(ref, struct nfs_dns_ent, h.ref);`
	`109`	`+ item = container_of(head, struct nfs_dns_ent, rcu_head);`
`109`	`110`	`kfree(item->hostname);`
`110`	`111`	`kfree(item);`
`111`	`112`	`}`
`112`	`113`
	`114`	`+static void nfs_dns_ent_put(struct kref *ref)`
	`115`	`+{`
	`116`	`+ struct nfs_dns_ent *item;`
	`117`	`+`
	`118`	`+ item = container_of(ref, struct nfs_dns_ent, h.ref);`
	`119`	`+ call_rcu(item, nfs_dns_ent_free_rcu);`
	`120`	`+}`
	`121`	`+`
`113`	`122`	`static struct cache_head *nfs_dns_ent_alloc(void)`
`114`	`123`	`{`
`115`	`124`	`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,`
`195`	`204`	`{`
`196`	`205`	`struct cache_head *ch;`
`197`	`206`
`198`		`- ch = sunrpc_cache_lookup(cd,`
	`207`	`+ ch = sunrpc_cache_lookup_rcu(cd,`
`199`	`208`	`&key->h,`
`200`	`209`	`nfs_dns_hash(key));`
`201`	`210`	`if (!ch)`