NFS: Add sysfs support for per-container identifier

In order to identify containers to the NFS client, we add a per-net
sysfs attribute that udev can fill with the appropriate identifier.
The identifier could be a unique hostname, but in most cases it
will probably be a persisted uuid.

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

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 0acb104..6e7aeb5 100644 (file)
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -49,6 +49,7 @@
 #include "pnfs.h"
 #include "nfs.h"
 #include "netns.h"
+#include "sysfs.h"
 
 #define NFSDBG_FACILITY                NFSDBG_CLIENT
 
@@ -1072,12 +1073,15 @@ void nfs_clients_init(struct net *net)
 #endif
        spin_lock_init(&nn->nfs_client_lock);
        nn->boot_time = ktime_get_real();
+
+       nfs_netns_sysfs_setup(nn, net);
 }
 
 void nfs_clients_exit(struct net *net)
 {
        struct nfs_net *nn = net_generic(net, nfs_net_id);
 
+       nfs_netns_sysfs_destroy(nn);
        nfs_cleanup_cb_ident_idr(net);
        WARN_ON_ONCE(!list_empty(&nn->nfs_client_list));
        WARN_ON_ONCE(!list_empty(&nn->nfs_volume_list));

diff --git a/fs/nfs/netns.h b/fs/nfs/netns.h
index fc9978c..c8374f7 100644 (file)
--- a/fs/nfs/netns.h
+++ b/fs/nfs/netns.h
@@ -15,6 +15,8 @@ struct bl_dev_msg {
        uint32_t major, minor;
 };
 
+struct nfs_netns_client;
+
 struct nfs_net {
        struct cache_detail *nfs_dns_resolve;
        struct rpc_pipe *bl_device_pipe;
@@ -29,6 +31,7 @@ struct nfs_net {
        unsigned short nfs_callback_tcpport6;
        int cb_users[NFS4_MAX_MINOR_VERSION + 1];
 #endif
+       struct nfs_netns_client *nfs_client;
        spinlock_t nfs_client_lock;
        ktime_t boot_time;
 #ifdef CONFIG_PROC_FS

diff --git a/fs/nfs/sysfs.c b/fs/nfs/sysfs.c
index 7070711..4f3390b 100644 (file)
--- a/fs/nfs/sysfs.c
+++ b/fs/nfs/sysfs.c
@@ -9,7 +9,12 @@
 #include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/netdevice.h>
+#include <linux/string.h>
+#include <linux/nfs_fs.h>
+#include <linux/rcupdate.h>
 
+#include "nfs4_fs.h"
+#include "netns.h"
 #include "sysfs.h"
 
 struct kobject *nfs_client_kobj;
@@ -67,3 +72,116 @@ void nfs_sysfs_exit(void)
        kobject_put(nfs_client_kobj);
        kset_unregister(nfs_client_kset);
 }
+
+static ssize_t nfs_netns_identifier_show(struct kobject *kobj,
+               struct kobj_attribute *attr, char *buf)
+{
+       struct nfs_netns_client *c = container_of(kobj,
+                       struct nfs_netns_client,
+                       kobject);
+       return scnprintf(buf, PAGE_SIZE, "%s\n", c->identifier);
+}
+
+/* Strip trailing '\n' */
+static size_t nfs_string_strip(const char *c, size_t len)
+{
+       while (len > 0 && c[len-1] == '\n')
+               --len;
+       return len;
+}
+
+static ssize_t nfs_netns_identifier_store(struct kobject *kobj,
+               struct kobj_attribute *attr,
+               const char *buf, size_t count)
+{
+       struct nfs_netns_client *c = container_of(kobj,
+                       struct nfs_netns_client,
+                       kobject);
+       const char *old;
+       char *p;
+       size_t len;
+
+       len = nfs_string_strip(buf, min_t(size_t, count, CONTAINER_ID_MAXLEN));
+       if (!len)
+               return 0;
+       p = kmemdup_nul(buf, len, GFP_KERNEL);
+       if (!p)
+               return -ENOMEM;
+       old = xchg(&c->identifier, p);
+       if (old) {
+               synchronize_rcu();
+               kfree(old);
+       }
+       return count;
+}
+
+static void nfs_netns_client_release(struct kobject *kobj)
+{
+       struct nfs_netns_client *c = container_of(kobj,
+                       struct nfs_netns_client,
+                       kobject);
+
+       if (c->identifier)
+               kfree(c->identifier);
+       kfree(c);
+}
+
+static const void *nfs_netns_client_namespace(struct kobject *kobj)
+{
+       return container_of(kobj, struct nfs_netns_client, kobject)->net;
+}
+
+static struct kobj_attribute nfs_netns_client_id = __ATTR(identifier,
+               0644, nfs_netns_identifier_show, nfs_netns_identifier_store);
+
+static struct attribute *nfs_netns_client_attrs[] = {
+       &nfs_netns_client_id.attr,
+       NULL,
+};
+
+static struct kobj_type nfs_netns_client_type = {
+       .release = nfs_netns_client_release,
+       .default_attrs = nfs_netns_client_attrs,
+       .sysfs_ops = &kobj_sysfs_ops,
+       .namespace = nfs_netns_client_namespace,
+};
+
+static struct nfs_netns_client *nfs_netns_client_alloc(struct kobject *parent,
+               struct net *net)
+{
+       struct nfs_netns_client *p;
+
+       p = kzalloc(sizeof(*p), GFP_KERNEL);
+       if (p) {
+               p->net = net;
+               p->kobject.kset = nfs_client_kset;
+               if (kobject_init_and_add(&p->kobject, &nfs_netns_client_type,
+                                       parent, "nfs_client") == 0)
+                       return p;
+               kobject_put(&p->kobject);
+       }
+       return NULL;
+}
+
+void nfs_netns_sysfs_setup(struct nfs_net *netns, struct net *net)
+{
+       struct nfs_netns_client *clp;
+
+       clp = nfs_netns_client_alloc(nfs_client_kobj, net);
+       if (clp) {
+               netns->nfs_client = clp;
+               kobject_uevent(&clp->kobject, KOBJ_ADD);
+       }
+}
+
+void nfs_netns_sysfs_destroy(struct nfs_net *netns)
+{
+       struct nfs_netns_client *clp = netns->nfs_client;
+
+       if (clp) {
+               kobject_uevent(&clp->kobject, KOBJ_REMOVE);
+               kobject_del(&clp->kobject);
+               kobject_put(&clp->kobject);
+               netns->nfs_client = NULL;
+       }
+}

diff --git a/fs/nfs/sysfs.h b/fs/nfs/sysfs.h
index 666f8db..f1b2741 100644 (file)
--- a/fs/nfs/sysfs.h
+++ b/fs/nfs/sysfs.h
@@ -6,10 +6,20 @@
 #ifndef __NFS_SYSFS_H
 #define __NFS_SYSFS_H
 
+#define CONTAINER_ID_MAXLEN (64)
+
+struct nfs_netns_client {
+       struct kobject kobject;
+       struct net *net;
+       const char *identifier;
+};
 
 extern struct kobject *nfs_client_kobj;
 
 extern int nfs_sysfs_init(void);
 extern void nfs_sysfs_exit(void);
 
+void nfs_netns_sysfs_setup(struct nfs_net *netns, struct net *net);
+void nfs_netns_sysfs_destroy(struct nfs_net *netns);
+
 #endif