Re: [PATCH 4/6] v4set_root: force "fsid=0" for all exports of '/'

["J. Bruce Fields" <bfields@xxxxxxxxxxxx>]

On Tue, Apr 24, 2012 at 03:46:38PM +1000, Neil Brown wrote:
> When "fsid=0" is not explicitly given in /etc/exports,
> v4set_root creates a pseudo (NFSEXP_V4ROOT) export for '/'
> with fsid 0 so that an NFSv4 client can find the root.
> 
> However if '/' is explicitly exported to the client, then that
> explicit export must be used, and it will not have fsid=0.
> So we must impose fsid=0 on all exports of '/'.
> Without this, if '/' is exported to a client, that client will
> not be able to mount '/' with NFSv4.

I'd also like to teach the kernel to do lookups of "/" when it wants the
pseudoroot, and then try searching for an fsid=0 export only if "/"
doesn't work.  Long term I'd rather not have the reliance on the fsid=0
convention.  (Though maybe I'm being silly, as we're likely stuck with
it.)

Anyway, I'm fine with this patch regardless.

--b.

> 
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
> ---
> 
>  utils/mountd/v4root.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/utils/mountd/v4root.c b/utils/mountd/v4root.c
> index 81f813b..b4fdcce 100644
> --- a/utils/mountd/v4root.c
> +++ b/utils/mountd/v4root.c
> @@ -192,6 +192,13 @@ v4root_set()
>  				 */
>  				continue;
>  
> +			if (strcmp(exp->m_export.e_path, "/") == 0 &&
> +			    !(exp->m_export.e_flags & NFSEXP_FSID)) {
> +				/* Force '/' to be exported as fsid == 0*/
> +				exp->m_export.e_flags |= NFSEXP_FSID;
> +				exp->m_export.e_fsid = 0;
> +			}
> +
>  			v4root_add_parents(exp);
>  			/* XXX: error handling! */
>  		}
> 
> 
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