commit 6b9cad8b3caae993763b413e85d9e646cc81c163
Author: Steve Dickson <steved@redhat.com>
Date:   Wed Nov 7 12:12:54 2007 -0500

    Added an active/deactive mechanism to the nfs_server structure
    allowing async operations to hold off umount until the
    operations are done.
    
    Signed-off-by: Steve Dickson <steved@redhat.com>

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 70587f3..774283d 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -593,6 +593,10 @@ static int nfs_init_server(struct nfs_server *server,
 	server->namelen  = data->namlen;
 	/* Create a client RPC handle for the NFSv3 ACL management interface */
 	nfs_init_server_aclclient(server);
+
+	init_waitqueue_head(&server->active_wq);
+	atomic_set(&server->active, 1);
+
 	dprintk("<-- nfs_init_server() = 0 [new %p]\n", clp);
 	return 0;
 
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index fa517ae..690e485 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -202,6 +202,7 @@ static int nfs_get_sb(struct file_system_type *, int, const char *, void *, stru
 static int nfs_xdev_get_sb(struct file_system_type *fs_type,
 		int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
 static void nfs_kill_super(struct super_block *);
+static void nfs_put_super(struct super_block *);
 
 static struct file_system_type nfs_fs_type = {
 	.owner		= THIS_MODULE,
@@ -223,6 +224,7 @@ static const struct super_operations nfs_sops = {
 	.alloc_inode	= nfs_alloc_inode,
 	.destroy_inode	= nfs_destroy_inode,
 	.write_inode	= nfs_write_inode,
+	.put_super		= nfs_put_super,
 	.statfs		= nfs_statfs,
 	.clear_inode	= nfs_clear_inode,
 	.umount_begin	= nfs_umount_begin,
@@ -1767,6 +1769,20 @@ static void nfs4_kill_super(struct super_block *sb)
 	nfs_free_server(server);
 }
 
+void nfs_put_super(struct super_block *sb)
+{
+	struct nfs_server *server = NFS_SB(sb);
+	/*
+	 * Make sure there are no outstanding ops to this server.
+	 * If so, wait for them to finish before allowing the
+	 * unmount to continue.
+	 */
+	if (atomic_read(&server->active) > 1) {
+		wait_event(server->active_wq, 
+			atomic_read(&server->active) == 1);
+	}
+}
+
 /*
  * Clone an NFS4 server record on xdev traversal (FSID-change)
  */
diff --git a/fs/nfs/unlink.c b/fs/nfs/unlink.c
index 233ad38..cf12a24 100644
--- a/fs/nfs/unlink.c
+++ b/fs/nfs/unlink.c
@@ -29,6 +29,7 @@ struct nfs_unlinkdata {
 static void
 nfs_free_unlinkdata(struct nfs_unlinkdata *data)
 {
+	nfs_sb_deactive(NFS_SERVER(data->dir));
 	iput(data->dir);
 	put_rpccred(data->cred);
 	kfree(data->args.name.name);
@@ -151,6 +152,7 @@ static int nfs_do_call_unlink(struct dentry *parent, struct inode *dir, struct n
 		nfs_dec_sillycount(dir);
 		return 0;
 	}
+	nfs_sb_active(NFS_SERVER(dir));
 	data->args.fh = NFS_FH(dir);
 	nfs_fattr_init(&data->res.dir_attr);
 
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 0cac49b..70a991b 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -4,6 +4,8 @@
 #include <linux/list.h>
 #include <linux/backing-dev.h>
 
+#include <asm/atomic.h>
+
 struct nfs_iostats;
 
 /*
@@ -110,8 +112,23 @@ struct nfs_server {
 						   filesystem */
 #endif
 	void (*destroy)(struct nfs_server *);
+
+	atomic_t active; /* Keep trace of any activity to this server */
+	wait_queue_head_t active_wq;  /* Wait for any activity to stop  */
 };
 
+static inline void 
+nfs_sb_active(struct nfs_server *server)
+{
+	atomic_inc(&server->active);
+}
+static inline void 
+nfs_sb_deactive(struct nfs_server *server)
+{
+	if (atomic_dec_return(&server->active) == 1)
+		wake_up(&server->active_wq);
+}
+
 /* Server capabilities */
 #define NFS_CAP_READDIRPLUS	(1U << 0)
 #define NFS_CAP_HARDLINKS	(1U << 1)