NFS: DNS resolver PipeFS notifier introduced

This patch subscribes DNS resolver caches to RPC pipefs notifications. Notifier
is registering on NFS module load. This notifier callback is responsible for
creation/destruction of PipeFS DNS resolver cache directory.
Note that no locking required in notifier callback because PipeFS superblock
pointer is passed as an argument from it's creation or destruction routine and
thus we can be sure about it's validity.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/cache_lib.c b/fs/nfs/cache_lib.c
index 5dd017bbb7a270fc8af09ca81b5e228f93b9fff0..5905a31211e50e2fec6d5f2e1caed05c678d4a47 100644 (file)
--- a/fs/nfs/cache_lib.c
+++ b/fs/nfs/cache_lib.c
@@ -112,7 +112,7 @@ int nfs_cache_wait_for_upcall(struct nfs_cache_defer_req *dreq)
        return 0;
 }
 
-static int nfs_cache_register_sb(struct super_block *sb, struct cache_detail *cd)
+int nfs_cache_register_sb(struct super_block *sb, struct cache_detail *cd)
 {
        int ret;
        struct dentry *dir;
@@ -147,7 +147,7 @@ err:
        return ret;
 }
 
-static void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
+void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
 {
        if (cd->u.pipefs.dir)
                sunrpc_cache_unregister_pipefs(cd);

diff --git a/fs/nfs/cache_lib.h b/fs/nfs/cache_lib.h
index e0a6cc4b01b9bad72bc46e3986d0b3473ba355c9..317db95e37f80375b371130afd58cb31f39161ed 100644 (file)
--- a/fs/nfs/cache_lib.h
+++ b/fs/nfs/cache_lib.h
@@ -27,3 +27,7 @@ extern void nfs_cache_init(struct cache_detail *cd);
 extern void nfs_cache_destroy(struct cache_detail *cd);
 extern int nfs_cache_register_net(struct net *net, struct cache_detail *cd);
 extern void nfs_cache_unregister_net(struct net *net, struct cache_detail *cd);
+extern int nfs_cache_register_sb(struct super_block *sb,
+                                struct cache_detail *cd);
+extern void nfs_cache_unregister_sb(struct super_block *sb,
+                                   struct cache_detail *cd);

diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index 9aea78ab86ac6dbd0a38abd0751c935fa345bdca..200eb67c95d972d81adf1a4401d796757b794676 100644 (file)
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -40,6 +40,7 @@ ssize_t nfs_dns_resolve_name(struct net *net, char *name, size_t namelen,
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/cache.h>
 #include <linux/sunrpc/svcauth.h>
+#include <linux/sunrpc/rpc_pipe_fs.h>
 
 #include "dns_resolve.h"
 #include "cache_lib.h"
@@ -400,12 +401,47 @@ void nfs_dns_resolver_cache_destroy(struct net *net)
        kfree(cd);
 }
 
+static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
+                          void *ptr)
+{
+       struct super_block *sb = ptr;
+       struct net *net = sb->s_fs_info;
+       struct nfs_net *nn = net_generic(net, nfs_net_id);
+       struct cache_detail *cd = nn->nfs_dns_resolve;
+       int ret = 0;
+
+       if (cd == NULL)
+               return 0;
+
+       if (!try_module_get(THIS_MODULE))
+               return 0;
+
+       switch (event) {
+       case RPC_PIPEFS_MOUNT:
+               ret = nfs_cache_register_sb(sb, cd);
+               break;
+       case RPC_PIPEFS_UMOUNT:
+               nfs_cache_unregister_sb(sb, cd);
+               break;
+       default:
+               ret = -ENOTSUPP;
+               break;
+       }
+       module_put(THIS_MODULE);
+       return ret;
+}
+
+static struct notifier_block nfs_dns_resolver_block = {
+       .notifier_call  = rpc_pipefs_event,
+};
+
 int nfs_dns_resolver_init(void)
 {
-       return 0;
+       return rpc_pipefs_notifier_register(&nfs_dns_resolver_block);
 }
 
 void nfs_dns_resolver_destroy(void)
 {
+       rpc_pipefs_notifier_unregister(&nfs_dns_resolver_block);
 }
 #endif