NFS: Stop sillyname renames and unmounts from racing

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>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

4 files changed, 33 insertions, 0 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index a6f62549761..c3740f5ab97 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -729,6 +729,9 @@ static struct nfs_server *nfs_alloc_server(void)
 	INIT_LIST_HEAD(&server->client_link);
 	INIT_LIST_HEAD(&server->master_link);
 
+	init_waitqueue_head(&server->active_wq);
+	atomic_set(&server->active, 0);
+
 	server->io_stats = nfs_alloc_iostats();
 	if (!server->io_stats) {
 		kfree(server);
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index f3acf48412b..75793794aef 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -160,6 +160,8 @@ extern struct rpc_stat nfs_rpcstat;
 
 extern int __init register_nfs_fs(void);
 extern void __exit unregister_nfs_fs(void);
+extern void nfs_sb_active(struct nfs_server *server);
+extern void nfs_sb_deactive(struct nfs_server *server);
 
 /* namespace.c */
 extern char *nfs_path(const char *base,
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 0b0c72a072f..fda1635dd13 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,
@@ -325,6 +327,28 @@ void __exit unregister_nfs_fs(void)
 	unregister_filesystem(&nfs_fs_type);
 }
 
+void nfs_sb_active(struct nfs_server *server)
+{
+	atomic_inc(&server->active);
+}
+
+void nfs_sb_deactive(struct nfs_server *server)
+{
+	if (atomic_dec_and_test(&server->active))
+		wake_up(&server->active_wq);
+}
+
+static 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.
+	 */
+	wait_event(server->active_wq, atomic_read(&server->active) == 0);
+}
+
 /*
  * Deliver file system statistics to userspace
  */
diff --git a/fs/nfs/unlink.c b/fs/nfs/unlink.c
index 431981d0265..8e5428e0b86 100644
--- a/fs/nfs/unlink.c
+++ b/fs/nfs/unlink.c
@@ -14,6 +14,8 @@
 #include <linux/sched.h>
 #include <linux/wait.h>
 
+#include "internal.h"
+
 struct nfs_unlinkdata {
 	struct hlist_node list;
 	struct nfs_removeargs args;
@@ -113,6 +115,7 @@ static void nfs_async_unlink_release(void *calldata)
 	struct nfs_unlinkdata	*data = calldata;
 
 	nfs_dec_sillycount(data->dir);
+	nfs_sb_deactive(NFS_SERVER(data->dir));
 	nfs_free_unlinkdata(data);
 }
 
@@ -153,6 +156,7 @@ 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);