From: bfields@fieldses.org (J. Bruce Fields)
To: Trond Myklebust <trondmy@primarydata.com>
Cc: "bfields@redhat.com" <bfields@redhat.com>,
"dhowells@redhat.com" <dhowells@redhat.com>,
"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH 10/10] nfsd: clients don't need to break their own delegations
Date: Tue, 20 Mar 2018 10:49:28 -0400 [thread overview]
Message-ID: <20180320144928.GA4288@fieldses.org> (raw)
In-Reply-To: <1521553578.10293.4.camel@primarydata.com>
On Tue, Mar 20, 2018 at 01:46:20PM +0000, Trond Myklebust wrote:
> On Tue, 2018-03-20 at 13:35 +0000, David Howells wrote:
> > J. Bruce Fields <bfields@redhat.com> wrote:
> >
> > > @@ -139,6 +139,9 @@ struct cred {
> > > struct key *thread_keyring; /* keyring private to
> > > this thread */
> > > struct key *request_key_auth; /* assumed
> > > request_key authority */
> > > #endif
> > > +#ifdef CONFIG_FILE_LOCKING
> > > + void *lease_breaker; /* identify NFS client
> > > breaking a delegation */
> > > +#endif
> > > #ifdef CONFIG_SECURITY
> > > void *security; /* subjective LSM
> > > security */
> > > #endif
> >
> > Sorry, but ewww.
> >
> > Two reasons for that comment:
> >
> > (1) The cred struct may get retained long past where you expect if
> > it gets
> > attached to another process or a file descriptor.
> >
> > (2) The ->lease_breaker pointer needs lifetime management in
> > cred.c. It will
> > potentially get copied around and may need cleaning up.
> >
> > Can you stick your breaker identity in a key struct as Jeff
> > suggested?
> >
>
> Bruce,
>
> Do you really need to do more than just identify that this is a knfsd
> thread vs not a knfsd thread? I'm assuming that a knfsd thread will
> usually be in a position to recall delegations before it even initiates
> an operation on the inode in question, won't it?
I think it could. I'm reluctant:
- Once we support write delegations, I think we end up having to
do that before basically every operation on a inode.
- I'd like this to make it easy for someone to extend delegation
support to userspace eventually too. I'm not sure exactly how
we'd identify self-conflicts in that case (struct files?), but
anyway I'd rather this wasn't too nfsd-specific.
That said, I'm still curious:
> IOW: what if you were to modify the lease code to allow knfsd threads
> to return a "please ignore me, and proceed with the operation that
> triggered the lease break" reply, and then handle conflicts between NFS
> clients outside the lease callback code altogether?
So if you're a random bit of code, how would you recommend testing
whether you're running in a knfsd thread?
--b.
next prev parent reply other threads:[~2018-03-20 14:49 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-19 14:36 [PATCH 00/10] Eliminate delegation self-conflicts v2 J. Bruce Fields
2018-03-19 14:36 ` [PATCH 01/10] vfs: remove unnecessary fl_owner_t typedef J. Bruce Fields
2018-03-19 14:36 ` [PATCH 02/10] nfsd: simplify put of fi_deleg_file J. Bruce Fields
2018-03-19 14:36 ` [PATCH 03/10] nfsd: simplify nfs4_put_deleg_lease calls J. Bruce Fields
2018-03-19 14:36 ` [PATCH 04/10] nfsd4: set fl_owner to delegation, not file pointer J. Bruce Fields
2018-03-19 14:36 ` [PATCH 05/10] nfsd4: dp->dl_stid.sc_file doesn't need locking J. Bruce Fields
2018-03-19 14:36 ` [PATCH 06/10] nfsd: make nfs4_get_existing_delegation less confusing J. Bruce Fields
2018-03-19 14:36 ` [PATCH 07/10] nfsd: factor out common delegation-destruction code J. Bruce Fields
2018-03-19 14:36 ` [PATCH 08/10] nfsd: move sc_file assignment into alloc_init_deleg J. Bruce Fields
2018-03-19 14:36 ` [PATCH 09/10] nfsd: create a separate lease for each delegation J. Bruce Fields
2018-03-19 14:36 ` [PATCH 10/10] nfsd: clients don't need to break their own delegations J. Bruce Fields
2018-03-20 13:10 ` [PATCH 00/10] Eliminate delegation self-conflicts v2 Jeff Layton
2018-03-20 13:35 ` [PATCH 10/10] nfsd: clients don't need to break their own delegations David Howells
2018-03-20 13:46 ` Trond Myklebust
2018-03-20 14:49 ` J. Bruce Fields [this message]
2018-03-20 15:13 ` Trond Myklebust
2018-03-20 16:02 ` bfields
2018-09-06 19:40 ` bfields
2018-03-20 14:52 ` J. Bruce Fields
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