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
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