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From:   Olga Kornievskaia <olga.kornievskaia@gmail.com>
Date:   Thu, 1 Aug 2019 14:24:04 -0400
Message-ID: <CAN-5tyEiO=kBQC=pLu_aeVfV+3f3KWFbz_1ooG8qBLoBqFaehQ@mail.gmail.com>
Subject: Re: [PATCH v4 5/8] NFSD check stateids against copy stateids
To:     "J. Bruce Fields" <bfields@fieldses.org>
Cc:     "J. Bruce Fields" <bfields@redhat.com>,
        linux-nfs <linux-nfs@vger.kernel.org>
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On Thu, Aug 1, 2019 at 2:12 PM J. Bruce Fields <bfields@fieldses.org> wrote:
>
> On Thu, Aug 01, 2019 at 02:06:46PM -0400, Olga Kornievskaia wrote:
> > On Thu, Aug 1, 2019 at 11:41 AM Olga Kornievskaia
> > <olga.kornievskaia@gmail.com> wrote:
> > >
> > > On Thu, Aug 1, 2019 at 11:13 AM J. Bruce Fields <bfields@fieldses.org> wrote:
> > > >
> > > > On Thu, Aug 01, 2019 at 10:12:11AM -0400, Olga Kornievskaia wrote:
> > > > > On Wed, Jul 31, 2019 at 5:51 PM J. Bruce Fields <bfields@redhat.com> wrote:
> > > > > >
> > > > > > On Wed, Jul 31, 2019 at 05:10:01PM -0400, Olga Kornievskaia wrote:
> > > > > > > I'm having difficulty with this patch because there is no good way to
> > > > > > > know when the copy_notify stateid can be freed. What I can propose is
> > > > > > > to have the linux client send a FREE_STATEID with the copy_notify
> > > > > > > stateid and use that as the trigger to free the state. In that case,
> > > > > > > I'll keep a reference on the parent until the FREE_STATEID is
> > > > > > > received.
> > > > > > >
> > > > > > > This is not in the spec (though seems like a good idea to tell the
> > > > > > > source server it's ok to clean up) so other implementations might not
> > > > > > > choose this approach so we'll have problems with stateids sticking
> > > > > > > around.
> > > > > >
> > > > > > https://tools.ietf.org/html/rfc7862#page-71
> > > > > >
> > > > > >         "If the cnr_lease_time expires while the destination server is
> > > > > >         still reading the source file, the destination server is allowed
> > > > > >         to finish reading the file.  If the cnr_lease_time expires
> > > > > >         before the destination server uses READ or READ_PLUS to begin
> > > > > >         the transfer, the source server can use NFS4ERR_PARTNER_NO_AUTH
> > > > > >         to inform the destination server that the cnr_lease_time has
> > > > > >         expired."
> > > > > >
> > > > > > The spec doesn't really define what "is allowed to finish reading the
> > > > > > file" means, but I think the source server should decide somehow whether
> > > > > > the target's done.  And "hasn't sent a read in cnr_lease_time" seems
> > > > > > like a pretty good conservative definition that would be easy to
> > > > > > enforce.
> > > > >
> > > > > "hasn't send a read in cnr_lease_time" is already enforced.
> > > > >
> > > > > The problem is when the copy did start in normal time, it might take
> > > > > unknown time to complete. If we limit copies to all be done with in a
> > > > > cnr_lease_time or even some number of that, we'll get into problems
> > > > > when files are large enough or network is slow enough that it will
> > > > > make this method unusable.
> > > >
> > > > No, I'm just suggesting that if it's been more than cnr_lease_time since
> > > > the target server last sent a read using this stateid, then we could
> > > > free the stateid.
> > >
> > > That's reasonable. Let me do that.
> >
> > Now that I need a global list for the copy_notify stateids, do you
> > have a preference for either to keep it of the nfs4_client structure
> > or the nfsd_net structure? I store async copies under the nfs4_client
> > structure but the laundromat traverses things in nfsd_net structure.
>
> If copy_notify stateids are associated with a client, then they must
> already be reachable from the client somehow so they can be destroyed at
> the time the client is, right?  I'm saying that without looking at the
> code....

yes, i agree. but since we are taking a reference on a parent stateid
and the copy_notify state is destroyed at the destruction of the
parent id, then we'll never get there (or shouldn't get there). But I
can add something to the client destruction to make sure to delete
anything if it's there.

i was just looking at close_lru and delegation_lru but I guess that's
not a list of delegation or open stateids but rather some complex of
not deleting the stateid right away but moving it to nfs4_ol_stateid
and the list on the nfsd_net. Are you looking for something similar
for the copy_notify state or can I just keep a global list of the
nfs4_client and add and delete of that (not move to the delete later)?

> --b.