On Sep 6, 2010, at 9:12 PM, Neil Brown wrote:
> On Tue, 31 Aug 2010 17:21:31 -0400
> Chuck Lever <chuck.lever@xxxxxxxxxx> 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.
We have
errno = 0;
just before the nfs_try_mount_v4(mi); call. This defines the value of errno even if nothing in nfs_try_mount_v4() sets it.
Perhaps that violates Bruce's "too subtle" rule and I should replace it with your suggested post-call check?
> 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);
>
--
chuck[dot]lever[at]oracle[dot]com
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
