[OpenAFS-devel] Re: RxOSD claim on 2 structure members

[Derrick Brashear]

On Mon, Jun 15, 2009 at 11:18 AM, Hartmut Reuter<reuter@rzg.mpg.de> wrote:
>
> Hi,
>
> After all the problems with claiming the SyncCounter field for RxOSD I
> would like to make a revised proposal for how AFS+RxOSD could use a
> field in struct FetchStatus. Instead of "SyncCounter" we could use
> "ResidencyMask" which has become obsolete since MR-AFS isn't used
> anymore at any site. When I decided to use the "SyncCounter" field as
> "Protocol" MR-AFS was still alive at our site so it would have been
> filled differently by the MR-AFS fileservers and could not be used for
> the new RxOSD code.

It may likewise be possible to avoid using Synccounter for the other
proposed use; None of that should stop this proposal from advancing as
it may give us leeway later when we need it.

> The field ResidencyMask was introduced by my patch
> client-64bit-file-size-support-20011031 by renaming the former field
> "SegSize". Since that time the OpenAFS fileserver fills this field with
> '1' which corresponds to the local_disk residency in MR-AFS. Presently
> this field isn't interpreted any more by the client.
>
> The AFS+RxOSD client presently copies the contents of "Protocol" (alias
> SyncCounter) into the new field "Protocol" of struct vcache. If we would
> copy instead the contents of "ResidencyMask" into avc->Protocol we would
> get a conflict with the present bit meaning of "1" which is VICEP_ACCESS
> and not the default rx-fileserver protocol (which is 0 as the default
> contents of SyncCounter used to be). This conflict could be solved
> either by using another bit for VICEO_ACCESS

> or by not having a
> one-to-one correspondence between ResidencyMask and avc->Protocol. The
> latter one is the smaller modification, but the first one may appear as
> =A0logically cleaner.

I don't see either being particularly logically cleaner.

Derrick