Re: [PATCH][RFC] nfsd/lockd: have locks_in_grace take a sb arg

[Stanislav Kinsbursky <skinsbursky@parallels.com>]

11.04.2012 00:22, J. Bruce Fields пишет:
> On Tue, Apr 10, 2012 at 04:46:38PM +0400, Stanislav Kinsbursky wrote:
>> 10.04.2012 16:16, Jeff Layton пишет:
>>> On Tue, 10 Apr 2012 15:44:42 +0400
>>>
>>> (sorry about the earlier truncated reply, my MUA has a mind of its own
>>> this morning)
>>>
>>
>> OK then. Previous letter confused me a bit.
>>
>>>
>>> TBH, I haven't considered that in depth. That is a valid situation, but
>>> one that's discouraged. It's very difficult (and expensive) to
>>> sequester off portions of a filesystem for serving.
>>>
>>> A filehandle is somewhat analogous to a device/inode combination. When
>>> the server gets a filehandle, it has to determine "is this within a
>>> path that's exported to this host"? That process is called subtree
>>> checking. It's expensive and difficult to handle. It's always better to
>>> export along filesystem boundaries.
>>>
>>> My suggestion would be to simply not deal with those cases in this
>>> patch. Possibly we could force no_subtree_check when we export an fs
>>> with a locks_in_grace option defined.
>>>
>>
>> Sorry, but without dealing with those cases your patch looks a bit... Useless.
>> I.e. it changes nothing, it there will be no support from file
>> systems, going to be exported.
>> But how are you going to push developers to implement these calls?
>> Or, even if you'll try to implement them by yourself, how they will
>> looks like?
>> Simple check only for superblock looks bad to me, because any other
>> start of NFSd will lead to grace period for all other containers
>> (which uses the same filesystem).
>
> That's the correct behavior, and it sounds simple to implement.  Let's
> just do that.
>
> If somebody doesn't like the grace period from another container
> intruding on their use of the same filesystem, they should either
> arrange to export different filesystems (not just different subtrees)
> from their containers, or arrange to start all their containers at the
> same time so their grace periods overlap.
>

Starting all at once is not a very good solution.
When you start 100 containers simultaneously - then you can't predict, when the 
process as a whole will succeed (it will produce heavy load on all subsystems). 
Moreover, there is also  server restart...
Anyway, I agree with the idea of this patch.

Please, have a look at new export option I mentioned in "Grace period" thread.

-- 
Best regards,
Stanislav Kinsbursky