Re: [PATCH] mountd: Ignore transient and non-fatal filesystem errors in nfsd_export

[bfields@fieldses.org (J. Bruce Fields)]

On Tue, Sep 08, 2020 at 05:19:58PM -0400, trondmy@kernel.org wrote:
> From: Trond Myklebust <trond.myklebust@hammerspace.com>
> 
> If the mount point check in nfsd_export fails due to a transient error,
> then ignore it to avoid spurious NFSERR_STALE errors being returned by
> knfsd.

What sort of transient errors?

I guess this makes the upcall (and the original rpc) eventually time
out?

--b.

> 
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> ---
>  utils/mountd/cache.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c
> index 6cba2883026f..93e868341d15 100644
> --- a/utils/mountd/cache.c
> +++ b/utils/mountd/cache.c
> @@ -1411,7 +1411,10 @@ static void nfsd_export(int f)
>  
>  		if (mp && !*mp)
>  			mp = found->m_export.e_path;
> -		if (mp && !is_mountpoint(mp))
> +		errno = 0;
> +		if (mp && !is_mountpoint(mp)) {
> +			if (errno != 0 && !path_lookup_error(errno))
> +				goto out;
>  			/* Exportpoint is not mounted, so tell kernel it is
>  			 * not available.
>  			 * This will cause it not to appear in the V4 Pseudo-root
> @@ -1420,9 +1423,12 @@ static void nfsd_export(int f)
>  			 * And filehandle for this mountpoint from an earlier
>  			 * mount will block in nfsd.fh lookup.
>  			 */
> +			xlog(L_WARNING,
> +			     "Cannot export path '%s': not a mountpoint",
> +			     path);
>  			dump_to_cache(f, buf, sizeof(buf), dom, path,
>  				      NULL, 60);
> -		else if (dump_to_cache(f, buf, sizeof(buf), dom, path,
> +		} else if (dump_to_cache(f, buf, sizeof(buf), dom, path,
>  					 &found->m_export, 0) < 0) {
>  			xlog(L_WARNING,
>  			     "Cannot export %s, possibly unsupported filesystem"
> -- 
> 2.26.2