NFSv4: Fix up RCU annotations for struct nfs_netns_client

The identifier is read as an RCU protected string. Its value may
be changed during the lifetime of the network namespace by writing
a new string into the sysfs pseudofile (at which point, we free the
old string only after a call to synchronize_rcu()).

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/fs/nfs/sysfs.c b/fs/nfs/sysfs.c
index c489496..8cb7075 100644 (file)
--- a/fs/nfs/sysfs.c
+++ b/fs/nfs/sysfs.c
@@ -79,7 +79,12 @@ static ssize_t nfs_netns_identifier_show(struct kobject *kobj,
        struct nfs_netns_client *c = container_of(kobj,
                        struct nfs_netns_client,
                        kobject);
-       return scnprintf(buf, PAGE_SIZE, "%s\n", c->identifier);
+       ssize_t ret;
+
+       rcu_read_lock();
+       ret = scnprintf(buf, PAGE_SIZE, "%s\n", rcu_dereference(c->identifier));
+       rcu_read_unlock();
+       return ret;
 }
 
 /* Strip trailing '\n' */
@@ -107,7 +112,7 @@ static ssize_t nfs_netns_identifier_store(struct kobject *kobj,
        p = kmemdup_nul(buf, len, GFP_KERNEL);
        if (!p)
                return -ENOMEM;
-       old = xchg(&c->identifier, p);
+       old = rcu_dereference_protected(xchg(&c->identifier, (char __rcu *)p), 1);
        if (old) {
                synchronize_rcu();
                kfree(old);
@@ -121,7 +126,7 @@ static void nfs_netns_client_release(struct kobject *kobj)
                        struct nfs_netns_client,
                        kobject);
 
-       kfree(c->identifier);
+       kfree(rcu_dereference_raw(c->identifier));
        kfree(c);
 }
 

diff --git a/fs/nfs/sysfs.h b/fs/nfs/sysfs.h
index ebcbdc4..5501ef5 100644 (file)
--- a/fs/nfs/sysfs.h
+++ b/fs/nfs/sysfs.h
@@ -11,7 +11,7 @@
 struct nfs_netns_client {
        struct kobject kobject;
        struct net *net;
-       const char *identifier;
+       const char __rcu *identifier;
 };
 
 extern struct kobject *nfs_client_kobj;