src/patches/suse-2.6.27.31/patches.fixes/nfs-02-Add-VFS-helper-functions-for-setting-up-private-namespaces

   1 From cf8d2c11cb77f129675478792122f50827e5b0ae Mon Sep 17 00:00:00 2001
   2 From: Trond Myklebust <Trond.Myklebust@netapp.com>
   3 Date: Mon, 22 Jun 2009 15:09:13 -0400
   4 Subject: [PATCH 2/5] VFS: Add VFS helper functions for setting up private namespaces
   5
   6 The purpose of this patch is to improve the remote mount path lookup
   7 support for distributed filesystems such as the NFSv4 client.
   8
   9 When given a mount command of the form "mount server:/foo/bar /mnt", the
  10 NFSv4 client is required to look up the filehandle for "server:/", and
  11 then look up each component of the remote mount path "foo/bar" in order
  12 to find the directory that is actually going to be mounted on /mnt.
  13 Following that remote mount path may involve following symlinks,
  14 crossing server-side mount points and even following referrals to
  15 filesystem volumes on other servers.
  16
  17 Since the standard VFS path lookup code already supports walking paths
  18 that contain all these features (using in-kernel automounts for
  19 following referrals) we would like to be able to reuse that rather than
  20 duplicate the full path traversal functionality in the NFSv4 client code.
  21
  22 This patch therefore defines a VFS helper function create_mnt_ns(), that
  23 sets up a temporary filesystem namespace and attaches a root filesystem to
  24 it. It exports the create_mnt_ns() and put_mnt_ns() function for use by
  25 filesystem modules.
  26
  27 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
  28 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  29 Acked-by: NeilBrown <neilb@suse.de>
  30 ---
  31  fs/namespace.c                |   45 ++++++++++++++++++++++++++++++++++--------
  32  include/linux/mnt_namespace.h |    1
  33  2 files changed, 38 insertions(+), 8 deletions(-)
  34
  35 --- a/fs/namespace.c
  36 +++ b/fs/namespace.c
  37 @@ -1939,6 +1939,21 @@ dput_out:
  38         return retval;
  39  }
  40
  41 +static struct mnt_namespace *alloc_mnt_ns(void)
  42 +{
  43 +       struct mnt_namespace *new_ns;
  44 +
  45 +       new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
  46 +       if (!new_ns)
  47 +               return ERR_PTR(-ENOMEM);
  48 +       atomic_set(&new_ns->count, 1);
  49 +       new_ns->root = NULL;
  50 +       INIT_LIST_HEAD(&new_ns->list);
  51 +       init_waitqueue_head(&new_ns->poll);
  52 +       new_ns->event = 0;
  53 +       return new_ns;
  54 +}
  55 +
  56  /*
  57   * Allocate a new namespace structure and populate it with contents
  58   * copied from the namespace of the passed in task structure.
  59 @@ -1950,14 +1965,9 @@ static struct mnt_namespace *dup_mnt_ns(
  60         struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
  61         struct vfsmount *p, *q;
  62
  63 -       new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
  64 -       if (!new_ns)
  65 -               return ERR_PTR(-ENOMEM);
  66 -
  67 -       atomic_set(&new_ns->count, 1);
  68 -       INIT_LIST_HEAD(&new_ns->list);
  69 -       init_waitqueue_head(&new_ns->poll);
  70 -       new_ns->event = 0;
  71 +       new_ns = alloc_mnt_ns();
  72 +       if (IS_ERR(new_ns))
  73 +               return new_ns;
  74
  75         down_write(&namespace_sem);
  76         /* First pass: copy the tree topology */
  77 @@ -2021,6 +2031,24 @@ struct mnt_namespace *copy_mnt_ns(unsign
  78         return new_ns;
  79  }
  80
  81 +/**
  82 + * create_mnt_ns - creates a private namespace and adds a root filesystem
  83 + * @mnt: pointer to the new root filesystem mountpoint
  84 + */
  85 +struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt)
  86 +{
  87 +       struct mnt_namespace *new_ns;
  88 +
  89 +       new_ns = alloc_mnt_ns();
  90 +       if (!IS_ERR(new_ns)) {
  91 +               mnt->mnt_ns = new_ns;
  92 +               new_ns->root = mnt;
  93 +               list_add(&new_ns->list, &new_ns->root->mnt_list);
  94 +       }
  95 +       return new_ns;
  96 +}
  97 +EXPORT_SYMBOL(create_mnt_ns);
  98 +
  99  SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
 100                 char __user *, type, unsigned long, flags, void __user *, data)
 101  {
 102 @@ -2328,3 +2356,4 @@ void put_mnt_ns(struct mnt_namespace *ns
 103         release_mounts(&umount_list);
 104         kfree(ns);
 105  }
 106 +EXPORT_SYMBOL(put_mnt_ns);
 107 --- a/include/linux/mnt_namespace.h
 108 +++ b/include/linux/mnt_namespace.h
 109 @@ -22,6 +22,7 @@ struct proc_mounts {
 110         int event;
 111  };
 112
 113 +extern struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt);
 114  extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *,
 115                 struct fs_struct *);
 116  extern void put_mnt_ns(struct mnt_namespace *ns);