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>

3 files changed, 37 insertions, 1 deletions

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 47167ab64f5b..3eea556d8f59 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -167,6 +167,7 @@ static void nfs_umount_begin(struct vfsmount *vfsmnt, int flags)
         struct nfs_server *server;
         struct rpc_clnt *rpc;
 
+        shrink_submounts(vfsmnt, &nfs_automount_list);
         if (!(flags & MNT_FORCE))
                 return;
         /* -EIO all pending I/O */
@@ -1943,6 +1944,7 @@ static void nfs_kill_super(struct super_block *s)
         nfs_free_iostats(server->io_stats);
         kfree(server->hostname);
         kfree(server);
+        nfs_release_automount_timer();
 }
 
 static struct file_system_type nfs_fs_type = {
@@ -2288,6 +2290,7 @@ static void nfs4_kill_super(struct super_block *sb)
         nfs_free_iostats(server->io_stats);
         kfree(server->hostname);
         kfree(server);
+        nfs_release_automount_timer();
 }
 
 static struct file_system_type nfs4_fs_type = {
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index a155505c36f1..e426516c1116 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -18,6 +18,11 @@
 
 #define NFSDBG_FACILITY         NFSDBG_VFS
 
+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
@@ -59,7 +64,7 @@ static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
                 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|MNT_SHRINKABLE, &nfs_automount_list);
         if (err < 0) {
                 mntput(mnt);
                 if (err == -EBUSY)
@@ -70,6 +75,7 @@ static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
         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_PTR(err);
@@ -87,3 +93,20 @@ struct inode_operations nfs_mountpoint_inode_operations = {
         .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();
+        }
+}
diff --git a/fs/nfs/sysctl.c b/fs/nfs/sysctl.c
index 4c486eb867ca..db61e51bb154 100644
--- a/fs/nfs/sysctl.c
+++ b/fs/nfs/sysctl.c
@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/nfs4.h>
 #include <linux/nfs_idmap.h>
+#include <linux/nfs_fs.h>
 
 #include "callback.h"
 
@@ -46,6 +47,15 @@ static ctl_table nfs_cb_sysctls[] = {
                 .strategy = &sysctl_jiffies,
         },
 #endif
+        {
+                .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 }
 };