Re: pivot_root broken in 2.6.15-rc1-mm2

[Neil Brown]

On Wednesday November 23, rob@xxxxxxxxxxx wrote:
> On Tuesday 22 November 2005 20:07, Neil Brown wrote:
> > Pivot_root seems to be broken in 2.6.15-rc1-mm2.
> >
> > I havea initramfs filesystem, mount a ext3 filesystem (which has /mnt)
> > at '/root' and
> >
> >   cd /root
> >   pivot . mnt
> >
> > and it says -EINVAL.
> 
> You can't pivot_root initramfs because initramfs is rootfs.
> 
> I wrote Documentation/filesystems/ramfs-rootfs-initramfs.txt just for this 
> occasion. :)

Unfortunately, 'man pivot_root' nor 'use the source, Luke' contain
pointers to this particular useful document.  They both list assorted
restrictions on pivot_root, but not this one.

How about the following?

Thanks,
NeilBrown

Signed-off-by: Neil Brown <neilb@xxxxxxx>

### Diffstat output
 ./fs/namespace.c |    4 ++++
 1 file changed, 4 insertions(+)

diff ./fs/namespace.c~current~ ./fs/namespace.c
--- ./fs/namespace.c~current~	2005-11-23 14:24:59.000000000 +1100
+++ ./fs/namespace.c	2005-11-24 16:07:01.000000000 +1100
@@ -1526,6 +1526,10 @@ static void chroot_fs_refs(struct nameid
  * pointed to by put_old must yield the same directory as new_root. No other
  * file system may be mounted on put_old. After all, new_root is a mountpoint.
  *
+ * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
+ * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
+ * in this situation.
+ *
  * Notes:
  *  - we don't move root/cwd if they are not at the root (reason: if something
  *    cared enough to change them, it's probably wrong to force them elsewhere)


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