NFS: idmap PipeFS notifier introduced

v2:
1) Added "nfs_idmap_init" and "nfs_idmap_quit" definitions for kernels built
without CONFIG_NFS_V4 option set.

This patch subscribes NFS clients to RPC pipefs notifications. Idmap notifier
is registering on NFS module load. This notifier callback is responsible for
creation/destruction of PipeFS idmap pipe dentry for NFS4 clients.

Since ipdmap pipe is created in rpc client pipefs directory, we have make sure,
that this directory has been created already. IOW RPC client notifier callback
has been called already. To achive this, PipeFS notifier priorities has been
introduced (RPC clients notifier priority is greater than NFS idmap one).
But this approach gives another problem: unlink for RPC client directory will
be called before NFS idmap pipe unlink on UMOUNT event and will fail, because
directory is not empty.
The solution, introduced in this patch, is to try to remove client directory
once again after idmap pipe was unlinked. This looks like ugly hack, so
probably it should be replaced in some more elegant way.

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>

1 files changed, 75 insertions, 0 deletions

diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index 769274ed51c..ff084d258c4 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -377,6 +377,7 @@ int nfs_map_gid_to_group(const struct nfs_server *server, __u32 gid, char *buf,
 #include <linux/nfs_fs.h>
 
 #include "nfs4_fs.h"
+#include "internal.h"
 
 #define IDMAP_HASH_SZ          128
 
@@ -530,6 +531,80 @@ nfs_idmap_delete(struct nfs_client *clp)
 	kfree(idmap);
 }
 
+static int __rpc_pipefs_event(struct nfs_client *clp, unsigned long event,
+			      struct super_block *sb)
+{
+	int err = 0;
+
+	switch (event) {
+	case RPC_PIPEFS_MOUNT:
+		BUG_ON(clp->cl_rpcclient->cl_dentry == NULL);
+		err = __nfs_idmap_register(clp->cl_rpcclient->cl_dentry,
+						clp->cl_idmap,
+						clp->cl_idmap->idmap_pipe);
+		break;
+	case RPC_PIPEFS_UMOUNT:
+		if (clp->cl_idmap->idmap_pipe) {
+			struct dentry *parent;
+
+			parent = clp->cl_idmap->idmap_pipe->dentry->d_parent;
+			__nfs_idmap_unregister(clp->cl_idmap->idmap_pipe);
+			/*
+			 * Note: This is a dirty hack. SUNRPC hook has been
+			 * called already but simple_rmdir() call for the
+			 * directory returned with error because of idmap pipe
+			 * inside. Thus now we have to remove this directory
+			 * here.
+			 */
+			if (rpc_rmdir(parent))
+				printk(KERN_ERR "%s: failed to remove clnt dir!\n", __func__);
+		}
+		break;
+	default:
+		printk(KERN_ERR "%s: unknown event: %ld\n", __func__, event);
+		return -ENOTSUPP;
+	}
+	return err;
+}
+
+static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
+			    void *ptr)
+{
+	struct super_block *sb = ptr;
+	struct nfs_client *clp;
+	int error = 0;
+
+	spin_lock(&nfs_client_lock);
+	list_for_each_entry(clp, &nfs_client_list, cl_share_link) {
+		if (clp->net != sb->s_fs_info)
+			continue;
+		if (clp->rpc_ops != &nfs_v4_clientops)
+			continue;
+		error = __rpc_pipefs_event(clp, event, sb);
+		if (error)
+			break;
+	}
+	spin_unlock(&nfs_client_lock);
+	return error;
+}
+
+#define PIPEFS_NFS_PRIO		1
+
+static struct notifier_block nfs_idmap_block = {
+	.notifier_call	= rpc_pipefs_event,
+	.priority	= SUNRPC_PIPEFS_NFS_PRIO,
+};
+
+int nfs_idmap_init(void)
+{
+	return rpc_pipefs_notifier_register(&nfs_idmap_block);
+}
+
+void nfs_idmap_quit(void)
+{
+	rpc_pipefs_notifier_unregister(&nfs_idmap_block);
+}
+
 /*
  * Helper routines for manipulating the hashtable
  */