Re: [PATCH 2/2] mount: RPC_PROGNOTREGISTERED should not be a permanent error

["J. Bruce Fields" <bfields@fieldses.org>]

Just one more thought about this one....

If you mistakenly attempt to mount a server that's using rpc for some
service other than nfs, then this will result in a hang where we
previously got a useful error, right?

Maybe that's a rare enough case not to worry about these days.

--b.

On Fri, Aug 19, 2016 at 11:45:56AM +1000, NeilBrown wrote:
> Commit: bf66c9facb8e ("mounts.nfs: v2 and v3 background mounts should retry when server is down.")
> 
> changed the behaviour of "bg" mounts so that RPC_PROGNOTREGISTERED,
> which maps to EOPNOTSUPP, is not a permanent error.
> This useful because when an NFS server starts up there is a small window between
> the moment that rpcbind (or portmap) starts responding to lookup requests,
> and the moment when nfsd registers with rpcbind.  During that window
> rpcbind will reply with RPC_PROGNOTREGISTERED, but mount should not give up.
> 
> This same reasoning applies to foreground mounts.  They don't wait for
> as long, but could still hit the window and fail prematurely.
> 
> So revert the above patch and instead add EOPNOTSUPP to the list of
> temporary errors known to nfs_is_permanent_error.
> 
> Signed-off-by: NeilBrown <neilb@suse.com>
> ---
>  utils/mount/stropts.c |    7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/utils/mount/stropts.c b/utils/mount/stropts.c
> index 9de6794c6177..d5dfb5e4a669 100644
> --- a/utils/mount/stropts.c
> +++ b/utils/mount/stropts.c
> @@ -948,6 +948,7 @@ static int nfs_is_permanent_error(int error)
>  	case ETIMEDOUT:
>  	case ECONNREFUSED:
>  	case EHOSTUNREACH:
> +	case EOPNOTSUPP:	/* aka RPC_PROGNOTREGISTERED */
>  	case EAGAIN:
>  		return 0;	/* temporary */
>  	default:
> @@ -1019,8 +1020,7 @@ static int nfsmount_parent(struct nfsmount_info *mi)
>  	if (nfs_try_mount(mi))
>  		return EX_SUCCESS;
>  
> -	/* retry background mounts when the server is not up */
> -	if (nfs_is_permanent_error(errno) && errno != EOPNOTSUPP) {
> +	if (nfs_is_permanent_error(errno)) {
>  		mount_error(mi->spec, mi->node, errno);
>  		return EX_FAIL;
>  	}
> @@ -1055,8 +1055,7 @@ static int nfsmount_child(struct nfsmount_info *mi)
>  		if (nfs_try_mount(mi))
>  			return EX_SUCCESS;
>  
> -		/* retry background mounts when the server is not up */
> -		if (nfs_is_permanent_error(errno) && errno != EOPNOTSUPP)
> +		if (nfs_is_permanent_error(errno))
>  			break;
>  
>  		if (time(NULL) > timeout)
>