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   1 /*
   2  * linux/fs/nfs/namespace.c
   3  *
   4  * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
   5  *
   6  * NFS namespace
   7  */
   8
   9 #include <linux/config.h>
  10
  11 #include <linux/dcache.h>
  12 #include <linux/mount.h>
  13 #include <linux/namei.h>
  14 #include <linux/nfs_fs.h>
  15 #include <linux/string.h>
  16 #include <linux/sunrpc/clnt.h>
  17 #include <linux/vfs.h>
  18
  19 #define NFSDBG_FACILITY         NFSDBG_VFS
  20
  21 LIST_HEAD(nfs_automount_list);
  22 static void nfs_expire_automounts(void *list);
  23 static DECLARE_WORK(nfs_automount_task, nfs_expire_automounts, &nfs_automount_list);
  24 int nfs_mountpoint_expiry_timeout = 500 * HZ;
  25
  26 /*
  27  * nfs_follow_mountpoint - handle crossing a mountpoint on the server
  28  * @dentry - dentry of mountpoint
  29  * @nd - nameidata info
  30  *
  31  * When we encounter a mountpoint on the server, we want to set up
  32  * a mountpoint on the client too, to prevent inode numbers from
  33  * colliding, and to allow "df" to work properly.
  34  * On NFSv4, we also want to allow for the fact that different
  35  * filesystems may be migrated to different servers in a failover
  36  * situation, and that different filesystems may want to use
  37  * different security flavours.
  38  */
  39 static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
  40 {
  41         struct vfsmount *mnt;
  42         struct nfs_server *server = NFS_SERVER(dentry->d_inode);
  43         struct dentry *parent;
  44         struct nfs_fh fh;
  45         struct nfs_fattr fattr;
  46         int err;
  47
  48         BUG_ON(IS_ROOT(dentry));
  49         dprintk("%s: enter\n", __FUNCTION__);
  50         dput(nd->dentry);
  51         nd->dentry = dget(dentry);
  52         if (d_mountpoint(nd->dentry))
  53                 goto out_follow;
  54         /* Look it up again */
  55         parent = dget_parent(nd->dentry);
  56         err = server->rpc_ops->lookup(parent->d_inode, &nd->dentry->d_name, &fh, &fattr);
  57         dput(parent);
  58         if (err != 0)
  59                 goto out_err;
  60
  61         mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr);
  62         err = PTR_ERR(mnt);
  63         if (IS_ERR(mnt))
  64                 goto out_err;
  65
  66         mntget(mnt);
  67         err = do_add_mount(mnt, nd, nd->mnt->mnt_flags|MNT_SHRINKABLE, &nfs_automount_list);
  68         if (err < 0) {
  69                 mntput(mnt);
  70                 if (err == -EBUSY)
  71                         goto out_follow;
  72                 goto out_err;
  73         }
  74         mntput(nd->mnt);
  75         dput(nd->dentry);
  76         nd->mnt = mnt;
  77         nd->dentry = dget(mnt->mnt_root);
  78         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
  79 out:
  80         dprintk("%s: done, returned %d\n", __FUNCTION__, err);
  81         return ERR_PTR(err);
  82 out_err:
  83         path_release(nd);
  84         goto out;
  85 out_follow:
  86         while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
  87                 ;
  88         err = 0;
  89         goto out;
  90 }
  91
  92 struct inode_operations nfs_mountpoint_inode_operations = {
  93         .follow_link    = nfs_follow_mountpoint,
  94         .getattr        = nfs_getattr,
  95 };
  96
  97 static void nfs_expire_automounts(void *data)
  98 {
  99         struct list_head *list = (struct list_head *)data;
 100
 101         mark_mounts_for_expiry(list);
 102         if (!list_empty(list))
 103                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 104 }
 105
 106 void nfs_release_automount_timer(void)
 107 {
 108         if (list_empty(&nfs_automount_list)) {
 109                 cancel_delayed_work(&nfs_automount_task);
 110                 flush_scheduled_work();
 111         }
 112 }