NFS: Add timeout to submounts

 Make automounted partitions expire using the mark_mounts_for_expiry()
 function. The timeout is controlled via a sysctl.

 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---
 fs/nfs/inode.c         |   64 +++++++++++++++++++++++++++++++++++++++++++++++++
 fs/nfs/namespace.c     |   25 ++++++++++++++++++-
 include/linux/nfs_fs.h |    2 +
 3 files changed, 90 insertions(+), 1 deletion(-)

Index: linux-2.6.12-rc1/fs/nfs/inode.c
===================================================================
--- linux-2.6.12-rc1.orig/fs/nfs/inode.c
+++ linux-2.6.12-rc1/fs/nfs/inode.c
@@ -33,6 +33,7 @@
 #include <linux/lockd/bind.h>
 #include <linux/smp_lock.h>
 #include <linux/seq_file.h>
+#include <linux/sysctl.h>
 #include <linux/mount.h>
 #include <linux/nfs_idmap.h>
 #include <linux/vfs.h>
@@ -126,6 +127,60 @@ struct rpc_program		nfsacl_program = {
 };
 #endif  /* CONFIG_NFS_V3_ACL */
 
+#ifdef CONFIG_SYSCTL
+/* Follow the established convention in NLM */
+#define CTL_UNNUMBERED -2
+
+static ctl_table nfs_sysctls[] = {
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "nfs_mountpoint_timeout",
+		.data		= &nfs_mountpoint_expiry_timeout,
+		.maxlen		= sizeof(nfs_mountpoint_expiry_timeout),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_jiffies,
+		.strategy	= &sysctl_jiffies,
+	},
+	{ .ctl_name = 0 }
+};
+
+static ctl_table nfs_sysctl_dir[] = {
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "nfs",
+		.mode		= 0555,
+		.child		= nfs_sysctls,
+	},
+	{ .ctl_name = 0 }
+};
+
+static ctl_table nfs_sysctl_root[] = {
+	{
+		.ctl_name	= CTL_FS,
+		.procname	= "fs",
+		.mode		= 0555,
+		.child		= nfs_sysctl_dir,
+	},
+	{ .ctl_name = 0 }
+};
+
+static struct ctl_table_header *nfs_sysctl_table;
+
+static inline int nfs_init_sysctl(void)
+{
+	nfs_sysctl_table = register_sysctl_table(nfs_sysctl_root, 0);
+	return nfs_sysctl_table != NULL ? 0 : -ENOMEM;
+}
+
+static inline void nfs_destroy_sysctl(void)
+{
+	unregister_sysctl_table(nfs_sysctl_table);
+}
+#else
+#define nfs_init_sysctl() (0)
+#define nfs_destroy_sysctl() do { } while(0)
+#endif /* CONFIG_SYSCTL */
+
 static inline unsigned long
 nfs_fattr_to_ino_t(struct nfs_fattr *fattr)
 {
@@ -1708,6 +1763,7 @@ static void nfs_kill_super(struct super_
 	if (server->hostname != NULL)
 		kfree(server->hostname);
 	kfree(server);
+	nfs_release_automount_timer();
 }
 
 static struct file_system_type nfs_fs_type = {
@@ -2070,6 +2126,7 @@ static void nfs4_kill_super(struct super
 	if (server->hostname != NULL)
 		kfree(server->hostname);
 	kfree(server);
+	nfs_release_automount_timer();
 }
 
 static struct file_system_type nfs4_fs_type = {
@@ -2393,6 +2450,10 @@ static int __init init_nfs_fs(void)
 {
 	int err;
 
+	err = nfs_init_sysctl();
+	if (err)
+		goto out5;
+
 	err = nfs_init_nfspagecache();
 	if (err)
 		goto out4;
@@ -2440,6 +2501,8 @@ out2:
 out3:
 	nfs_destroy_nfspagecache();
 out4:
+	nfs_destroy_sysctl();
+out5:
 	return err;
 }
 
@@ -2455,6 +2518,7 @@ static void __exit exit_nfs_fs(void)
 #ifdef CONFIG_PROC_FS
 	rpc_proc_unregister("nfs");
 #endif
+	nfs_destroy_sysctl();
 	unregister_filesystem(&nfs_fs_type);
 	unregister_nfs4fs();
 }
Index: linux-2.6.12-rc1/fs/nfs/namespace.c
===================================================================
--- linux-2.6.12-rc1.orig/fs/nfs/namespace.c
+++ linux-2.6.12-rc1/fs/nfs/namespace.c
@@ -18,6 +18,11 @@
 
 #define NFSDBG_FACILITY		NFSDBG_VFS
 
+static LIST_HEAD(nfs_automount_list);
+static void nfs_expire_automounts(void *list);
+static DECLARE_WORK(nfs_automount_task, nfs_expire_automounts, &nfs_automount_list);
+int nfs_mountpoint_expiry_timeout = 500 * HZ;
+
 /*
  * nfs_follow_mountpoint - handle crossing a mountpoint on the server
  * @dentry - dentry of mountpoint
@@ -58,7 +63,7 @@ static int nfs_follow_mountpoint(struct 
 		goto out_err;
 	}
 	mntget(mnt);
-	err = do_add_mount(mnt, nd, nd->mnt->mnt_flags, NULL);
+	err = do_add_mount(mnt, nd, nd->mnt->mnt_flags, &nfs_automount_list);
 	if (err < 0) {
 		mntput(mnt);
 		if (err == -EBUSY)
@@ -69,6 +74,7 @@ static int nfs_follow_mountpoint(struct 
 	dput(nd->dentry);
 	nd->mnt = mnt;
 	nd->dentry = dget(mnt->mnt_root);
+	schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 out:
 	dprintk("%s: done, returned %d\n", __FUNCTION__, err);
 	return err;
@@ -86,3 +92,20 @@ struct inode_operations nfs_mountpoint_i
 	.follow_link	= nfs_follow_mountpoint,
 	.getattr	= nfs_getattr,
 };
+
+static void nfs_expire_automounts(void *data)
+{
+	struct list_head *list = (struct list_head *)data;
+
+	mark_mounts_for_expiry(list);
+	if (!list_empty(list))
+		schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
+}
+
+void nfs_release_automount_timer(void)
+{
+	if (list_empty(&nfs_automount_list)) {
+		cancel_delayed_work(&nfs_automount_task);
+		flush_scheduled_work();
+	}
+}
Index: linux-2.6.12-rc1/include/linux/nfs_fs.h
===================================================================
--- linux-2.6.12-rc1.orig/include/linux/nfs_fs.h
+++ linux-2.6.12-rc1/include/linux/nfs_fs.h
@@ -378,6 +378,8 @@ extern struct inode_operations nfs_symli
  * linux/fs/nfs/namespace.c
  */
 extern struct inode_operations nfs_mountpoint_inode_operations;
+extern int nfs_mountpoint_expiry_timeout;
+extern void nfs_release_automount_timer(void);
 
 /*
  * linux/fs/nfs/unlink.c