nfs: move the nfs4_data_server_cache into struct nfs_net

Since struct nfs4_pnfs_ds should not be shared between net namespaces,
move from a global list of objects to a per-netns list and spinlock.

Tested-by: Sargun Dillon <[e-mail]>
Signed-off-by: Jeff Layton <[e-mail]>
Reviewed-by: Benjamin Coddington <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/client.c

···
 #if IS_ENABLED(CONFIG_NFS_V4)
 	idr_init(&nn->cb_ident_idr);
 #endif
+#if IS_ENABLED(CONFIG_NFS_V4_1)
+	INIT_LIST_HEAD(&nn->nfs4_data_server_cache);
+	spin_lock_init(&nn->nfs4_data_server_lock);
+#endif
 	spin_lock_init(&nn->nfs_client_lock);
 	nn->boot_time = ktime_get_real();
 	memset(&nn->rpcstats, 0, sizeof(nn->rpcstats));
···
 	nfs_cleanup_cb_ident_idr(net);
 	WARN_ON_ONCE(!list_empty(&nn->nfs_client_list));
 	WARN_ON_ONCE(!list_empty(&nn->nfs_volume_list));
+#if IS_ENABLED(CONFIG_NFS_V4_1)
+	WARN_ON_ONCE(!list_empty(&nn->nfs4_data_server_cache));
+#endif
 }
 
 #ifdef CONFIG_PROC_FS

fs/nfs/netns.h

···
 	unsigned short nfs_callback_tcpport;
 	unsigned short nfs_callback_tcpport6;
 	int cb_users[NFS4_MAX_MINOR_VERSION + 1];
-#endif
+#endif /* CONFIG_NFS_V4 */
+#if IS_ENABLED(CONFIG_NFS_V4_1)
+	struct list_head nfs4_data_server_cache;
+	spinlock_t nfs4_data_server_lock;
+#endif /* CONFIG_NFS_V4_1 */
 	struct nfs_netns_client *nfs_client;
 	spinlock_t nfs_client_lock;
 	ktime_t boot_time;

fs/nfs/pnfs_nfs.c

···
 #include "nfs4session.h"
 #include "internal.h"
 #include "pnfs.h"
+#include "netns.h"
 
 #define NFSDBG_FACILITY		NFSDBG_PNFS
 
···
 /*
  * Data server cache
  *
- * Data servers can be mapped to different device ids.
- * nfs4_pnfs_ds reference counting
+ * Data servers can be mapped to different device ids, but should
+ * never be shared between net namespaces.
+ *
+ * nfs4_pnfs_ds reference counting:
  *   - set to 1 on allocation
  *   - incremented when a device id maps a data server already in the cache.
  *   - decremented when deviceid is removed from the cache.
  */
-static DEFINE_SPINLOCK(nfs4_ds_cache_lock);
-static LIST_HEAD(nfs4_data_server_cache);
 
 /* Debug routines */
 static void
···
  * Lookup DS by addresses.  nfs4_ds_cache_lock is held
  */
 static struct nfs4_pnfs_ds *
-_data_server_lookup_locked(const struct net *net, const struct list_head *dsaddrs)
+_data_server_lookup_locked(const struct nfs_net *nn, const struct list_head *dsaddrs)
 {
 	struct nfs4_pnfs_ds *ds;
 
-	list_for_each_entry(ds, &nfs4_data_server_cache, ds_node)
-		if (ds->ds_net == net && _same_data_server_addrs_locked(&ds->ds_addrs, dsaddrs))
+	list_for_each_entry(ds, &nn->nfs4_data_server_cache, ds_node)
+		if (_same_data_server_addrs_locked(&ds->ds_addrs, dsaddrs))
 			return ds;
 	return NULL;
 }
···
 
 void nfs4_pnfs_ds_put(struct nfs4_pnfs_ds *ds)
 {
-	if (refcount_dec_and_lock(&ds->ds_count,
-				&nfs4_ds_cache_lock)) {
+	struct nfs_net *nn = net_generic(ds->ds_net, nfs_net_id);
+
+	if (refcount_dec_and_lock(&ds->ds_count, &nn->nfs4_data_server_lock)) {
 		list_del_init(&ds->ds_node);
-		spin_unlock(&nfs4_ds_cache_lock);
+		spin_unlock(&nn->nfs4_data_server_lock);
 		destroy_ds(ds);
 	}
 }
···
 struct nfs4_pnfs_ds *
 nfs4_pnfs_ds_add(const struct net *net, struct list_head *dsaddrs, gfp_t gfp_flags)
 {
+	struct nfs_net *nn = net_generic(net, nfs_net_id);
 	struct nfs4_pnfs_ds *tmp_ds, *ds = NULL;
 	char *remotestr;
 
···
 	/* this is only used for debugging, so it's ok if its NULL */
 	remotestr = nfs4_pnfs_remotestr(dsaddrs, gfp_flags);
 
-	spin_lock(&nfs4_ds_cache_lock);
-	tmp_ds = _data_server_lookup_locked(net, dsaddrs);
+	spin_lock(&nn->nfs4_data_server_lock);
+	tmp_ds = _data_server_lookup_locked(nn, dsaddrs);
 	if (tmp_ds == NULL) {
 		INIT_LIST_HEAD(&ds->ds_addrs);
 		list_splice_init(dsaddrs, &ds->ds_addrs);
···
 		INIT_LIST_HEAD(&ds->ds_node);
 		ds->ds_net = net;
 		ds->ds_clp = NULL;
-		list_add(&ds->ds_node, &nfs4_data_server_cache);
+		list_add(&ds->ds_node, &nn->nfs4_data_server_cache);
 		dprintk("%s add new data server %s\n", __func__,
 			ds->ds_remotestr);
 	} else {
···
 			refcount_read(&tmp_ds->ds_count));
 		ds = tmp_ds;
 	}
-	spin_unlock(&nfs4_ds_cache_lock);
+	spin_unlock(&nn->nfs4_data_server_lock);
 out:
 	return ds;
 }