Re: [PATCH 1/3] mount.nfs: Refactor mount version and protocol autonegotiation

[Neil Brown <neilb@suse.de>]

On Tue, 31 Aug 2010 17:21:31 -0400
Chuck Lever <chuck.lever@oracle.com> wrote:

> The logic that manages negotiating NFS version and protocol settings
> is getting more complex over time, so let's split this out of
> nfs_try_mount().
> 
> This should make Bruce a little happier, as it eliminates the silent
> switch case fall through in nfs_try_mount().  And it should help Neil
> fix some bugs he's found in this logic.

Hi Chuck,
 thanks for these..
 One question....

.....
> +{
> +	int result;
> +
> +	/*
> +	 * Before 2.6.32, the kernel NFS client didn't support
> +	 * "-t nfs vers=4" mounts, so NFS version 4 cannot be
> +	 * included when autonegotiating while running on
> +	 * those kernels.
> +	 */
> +	if (linux_version_code() <= MAKE_VERSION(2, 6, 31))
> +		goto fall_back;
> +
> +	errno = 0;
> +	result = nfs_try_mount_v4(mi);
> +	switch (errno) {

Should we not have e.g.

   if (result)
         return result;

before the switch(errno)??  Typically errno is 'undefined' in no error is
reported.

I realise the current code doesn't have that test either, but I still think
it is wrong not to.

Thanks
NeilBrown



> +	case EPROTONOSUPPORT:
> +		/* A clear indication that the server or our
> +		 * client does not support NFS version 4. */
> +		goto fall_back;
> +	case ENOENT:
> +		/* Legacy Linux servers don't export an NFS
> +		 * version 4 pseudoroot. */
> +		goto fall_back;
> +	case EPERM:
> +		/* Linux servers prior to 2.6.25 may return
> +		 * EPERM when NFS version 4 is not supported. */
> +		goto fall_back;
> +	default:
> +		return result;
> +	}
> +
> +fall_back:
> +	return nfs_try_mount_v3v2(mi);
> +}
> +
> +/*
>   * This is a single pass through the fg/bg loop.
>   *
>   * Returns TRUE if successful, otherwise FALSE.
> @@ -758,20 +801,8 @@ static int nfs_try_mount(struct nfsmount_info *mi)
>  
>  	switch (mi->version) {
>  	case 0:
> -		if (linux_version_code() > MAKE_VERSION(2, 6, 31)) {
> -			errno = 0;
> -			result = nfs_try_mount_v4(mi);
> -			if (errno != EPROTONOSUPPORT) {
> -				/* 
> -				 * To deal with legacy Linux servers that don't
> -				 * automatically export a pseudo root, retry
> -				 * ENOENT errors using version 3. And for
> -				 * Linux servers prior to 2.6.25, retry EPERM
> -				 */
> -				if (errno != ENOENT && errno != EPERM)
> -					break;
> -			}
> -		}
> +		result = nfs_autonegotiate(mi);
> +		break;
>  	case 2:
>  	case 3:
>  		result = nfs_try_mount_v3v2(mi);