to den 11.08.2005 Klokka 15:22 (+0200) skreiv Michael Kerrisk:
> As noted already, I don't know much of CIFS and SAMBA.
> But are you saying that it is sensible and consistent that
> "a process can open a file read-write, and can't place a
> read lease, but can place a write lease"?
It is just as "sensible and consistent" as being able to open the file
read-write and being able to place a read lease but not a write lease.
What is your point?
Make no mistake: this is not a locking protocol. It is implementing
support for a _caching_ protocol.
> This is precisely the point of the problem. Stephen
> Rothwell, and Matthew Wilcox seem to be saying that
> the last bit is not the case.
The NFSv4 spec explicitly states that
When a client has a read open delegation, it may not make any changes
to the contents or attributes of the file but it is assured that no
other client may do so. When a client has a write open delegation,
it may modify the file data since no other client will be accessing
the file's data. The client holding a write delegation may only
affect file attributes which are intimately connected with the file
data: size, time_modify, change.
so NFSv4 cannot currently support this behaviour. If CIFS supports it,
then maybe we have a case for going to the IETF and asking for a
clarification to implement the same behaviour in NFSv4.
Cheers,
Trond
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