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SubjectRe: [PATCH 2/5] VFS: Add VFS helper functions for setting up private namespaces
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On Tue, 2009-06-23 at 15:13 -0500, Serge E. Hallyn wrote:
> Quoting Trond Myklebust (Trond.Myklebust@netapp.com):
> > The purpose of this patch is to improve the remote mount path lookup
> > support for distributed filesystems such as the NFSv4 client.
> >
> > When given a mount command of the form "mount server:/foo/bar /mnt", the
> > NFSv4 client is required to look up the filehandle for "server:/", and
> > then look up each component of the remote mount path "foo/bar" in order
> > to find the directory that is actually going to be mounted on /mnt.
> > Following that remote mount path may involve following symlinks,
> > crossing server-side mount points and even following referrals to
> > filesystem volumes on other servers.
> >
> > Since the standard VFS path lookup code already supports walking paths
> > that contain all these features (using in-kernel automounts for
> > following referrals) we would like to be able to reuse that rather than
> > duplicate the full path traversal functionality in the NFSv4 client code.
> >
> > This patch therefore defines a VFS helper function create_mnt_ns(), that
> > sets up a temporary filesystem namespace and attaches a root filesystem to
> > it. It exports the create_mnt_ns() and put_mnt_ns() function for use by
> > filesystem modules.
> >
> > Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
>
> This looks good, thanks. Though I see no reason not to also switch over
> init_mount_tree() to the new helper.
>
> (Seems plausible that c/r code would use this as well)
>
> Reviewed-by: Serge Hallyn <serue@us.ibm.com>
>
> thanks,
> -serge

Thanks for the review! I missed the code duplication in
init_mount_tree(). Something like the following?

Cheers
Trond
--------------------------------------------------------------------
From: Trond Myklebust <Trond.Myklebust@netapp.com>
VFS: Switch init_mount_tree() to use the new create_mnt_ns() helper

Eliminates some duplicated code...

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

fs/namespace.c | 11 ++---------
1 files changed, 2 insertions(+), 9 deletions(-)


diff --git a/fs/namespace.c b/fs/namespace.c
index a7bea8c..4a86b85 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2222,16 +2222,9 @@ static void __init init_mount_tree(void)
mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
if (IS_ERR(mnt))
panic("Can't create rootfs");
- ns = kmalloc(sizeof(*ns), GFP_KERNEL);
- if (!ns)
+ ns = create_mnt_ns(mnt);
+ if (IS_ERR(ns))
panic("Can't allocate initial namespace");
- atomic_set(&ns->count, 1);
- INIT_LIST_HEAD(&ns->list);
- init_waitqueue_head(&ns->poll);
- ns->event = 0;
- list_add(&mnt->mnt_list, &ns->list);
- ns->root = mnt;
- mnt->mnt_ns = ns;

init_task.nsproxy->mnt_ns = ns;
get_mnt_ns(ns);

--
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com


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