On Thu, 2021-05-20 at 16:47 -0400, bfields@xxxxxxxxxxxx wrote:
> On Thu, May 20, 2021 at 07:08:24PM +0000, Trond Myklebust wrote:
> > On Thu, 2021-05-20 at 14:29 -0400, J. Bruce Fields wrote:
> > > On Thu, May 20, 2021 at 12:38:59PM -0400, trondmy@xxxxxxxxxx wrote:
> > > > From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> > > >
> > > > If we're unable to immediately recover all locks because the
> > > > server
> > > > is
> > > > unable to immediately service our reclaim calls, then we want to
> > > > retry
> > > > after we've finished servicing all the other asynchronous
> > > > delegation
> > > > returns on our queue.
> > >
> > > So, there's a situation where the server can't service a reclaim
> > > until
> > > some other delegation is returned? I'm not seeing how that
> > > happens.
> > >
> >
> > I can and I do... pNFS can be complicated...
>
> I don't doubt you, but does everyone get this but me?
>
> Is it too complicated to explain?
>
Not if you read the code, no.
In nfs_end_delegation_return():
do {
if (test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
break;
err = nfs_delegation_claim_opens(inode, &delegation->stateid,
delegation->type);
if (!issync || err != -EAGAIN)
break;
/*
* Guard against state recovery
*/
err = nfs4_wait_clnt_recover(clp);
} while (err == 0);
So if issync is false, then we abort the delegation return and try
again later.
...and when we later add a break_lease() call in this patch series,
then there is another condition.
> --b.
>
> >
> > > --b.
> > >
> > > >
> > > > Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> > > > ---
> > > > fs/nfs/delegation.c | 71 +++++++++++++++++++++++++++++++++++----
> > > > --
> > > > ----
> > > > fs/nfs/delegation.h | 1 +
> > > > fs/nfs/nfs4_fs.h | 1 +
> > > > 3 files changed, 58 insertions(+), 15 deletions(-)
> > > >
> > > > diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
> > > > index e6ec6f09ac6e..7c45ac3c3b0b 100644
> > > > --- a/fs/nfs/delegation.c
> > > > +++ b/fs/nfs/delegation.c
> > > > @@ -75,6 +75,13 @@ void nfs_mark_delegation_referenced(struct
> > > > nfs_delegation *delegation)
> > > > set_bit(NFS_DELEGATION_REFERENCED, &delegation->flags);
> > > > }
> > > >
> > > > +static void nfs_mark_return_delegation(struct nfs_server
> > > > *server,
> > > > + struct nfs_delegation
> > > > *delegation)
> > > > +{
> > > > + set_bit(NFS_DELEGATION_RETURN, &delegation->flags);
> > > > + set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client-
> > > > > cl_state);
> > > > +}
> > > > +
> > > > static bool
> > > > nfs4_is_valid_delegation(const struct nfs_delegation
> > > > *delegation,
> > > > fmode_t flags)
> > > > @@ -293,6 +300,7 @@ nfs_start_delegation_return_locked(struct
> > > > nfs_inode *nfsi)
> > > > goto out;
> > > > spin_lock(&delegation->lock);
> > > > if (!test_and_set_bit(NFS_DELEGATION_RETURNING,
> > > > &delegation->flags)) {
> > > > + clear_bit(NFS_DELEGATION_RETURN_DELAYED,
> > > > &delegation->flags);
> > > > /* Refcount matched in
> > > > nfs_end_delegation_return()
> > > > */
> > > > ret = nfs_get_delegation(delegation);
> > > > }
> > > > @@ -314,16 +322,17 @@ nfs_start_delegation_return(struct
> > > > nfs_inode
> > > > *nfsi)
> > > > return delegation;
> > > > }
> > > >
> > > > -static void
> > > > -nfs_abort_delegation_return(struct nfs_delegation *delegation,
> > > > - struct nfs_client *clp)
> > > > +static void nfs_abort_delegation_return(struct nfs_delegation
> > > > *delegation,
> > > > + struct nfs_client *clp,
> > > > int
> > > > err)
> > > > {
> > > >
> > > > spin_lock(&delegation->lock);
> > > > clear_bit(NFS_DELEGATION_RETURNING, &delegation->flags);
> > > > - set_bit(NFS_DELEGATION_RETURN, &delegation->flags);
> > > > + if (err == -EAGAIN) {
> > > > + set_bit(NFS_DELEGATION_RETURN_DELAYED,
> > > > &delegation-
> > > > > flags);
> > > > + set_bit(NFS4CLNT_DELEGRETURN_DELAYED, &clp-
> > > > > cl_state);
> > > > + }
> > > > spin_unlock(&delegation->lock);
> > > > - set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);
> > > > }
> > > >
> > > > static struct nfs_delegation *
> > > > @@ -539,7 +548,7 @@ static int nfs_end_delegation_return(struct
> > > > inode *inode, struct nfs_delegation
> > > > } while (err == 0);
> > > >
> > > > if (err) {
> > > > - nfs_abort_delegation_return(delegation, clp);
> > > > + nfs_abort_delegation_return(delegation, clp,
> > > > err);
> > > > goto out;
> > > > }
> > > >
> > > > @@ -568,6 +577,7 @@ static bool nfs_delegation_need_return(struct
> > > > nfs_delegation *delegation)
> > > > if (ret)
> > > > clear_bit(NFS_DELEGATION_RETURN_IF_CLOSED,
> > > > &delegation->flags);
> > > > if (test_bit(NFS_DELEGATION_RETURNING, &delegation-
> > > > >flags)
> > > > > >
> > > > + test_bit(NFS_DELEGATION_RETURN_DELAYED, &delegation-
> > > > > flags) ||
> > > > test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
> > > > ret = false;
> > > >
> > > > @@ -647,6 +657,38 @@ static int
> > > > nfs_server_return_marked_delegations(struct nfs_server *server,
> > > > return err;
> > > > }
> > > >
> > > > +static bool nfs_server_clear_delayed_delegations(struct
> > > > nfs_server
> > > > *server)
> > > > +{
> > > > + struct nfs_delegation *d;
> > > > + bool ret = false;
> > > > +
> > > > + list_for_each_entry_rcu (d, &server->delegations,
> > > > super_list) {
> > > > + if (!test_bit(NFS_DELEGATION_RETURN_DELAYED, &d-
> > > > > flags))
> > > > + continue;
> > > > + nfs_mark_return_delegation(server, d);
> > > > + clear_bit(NFS_DELEGATION_RETURN_DELAYED, &d-
> > > > > flags);
> > > > + ret = true;
> > > > + }
> > > > + return ret;
> > > > +}
> > > > +
> > > > +static bool nfs_client_clear_delayed_delegations(struct
> > > > nfs_client
> > > > *clp)
> > > > +{
> > > > + struct nfs_server *server;
> > > > + bool ret = false;
> > > > +
> > > > + if (!test_and_clear_bit(NFS4CLNT_DELEGRETURN_DELAYED,
> > > > &clp-
> > > > > cl_state))
> > > > + goto out;
> > > > + rcu_read_lock();
> > > > + list_for_each_entry_rcu (server, &clp->cl_superblocks,
> > > > client_link) {
> > > > + if (nfs_server_clear_delayed_delegations(server))
> > > > + ret = true;
> > > > + }
> > > > + rcu_read_unlock();
> > > > +out:
> > > > + return ret;
> > > > +}
> > > > +
> > > > /**
> > > > * nfs_client_return_marked_delegations - return previously
> > > > marked
> > > > delegations
> > > > * @clp: nfs_client to process
> > > > @@ -659,8 +701,14 @@ static int
> > > > nfs_server_return_marked_delegations(struct nfs_server *server,
> > > > */
> > > > int nfs_client_return_marked_delegations(struct nfs_client *clp)
> > > > {
> > > > - return nfs_client_for_each_server(clp,
> > > > - nfs_server_return_marked_delegations,
> > > > NULL);
> > > > + int err = nfs_client_for_each_server(
> > > > + clp, nfs_server_return_marked_delegations, NULL);
> > > > + if (err)
> > > > + return err;
> > > > + /* If a return was delayed, sleep to prevent hard looping
> > > > */
> > > > + if (nfs_client_clear_delayed_delegations(clp))
> > > > + ssleep(1);
> > > > + return 0;
> > > > }
> > > >
> > > > /**
> > > > @@ -775,13 +823,6 @@ static void
> > > > nfs_mark_return_if_closed_delegation(struct nfs_server *server,
> > > > set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client-
> > > > > cl_state);
> > > > }
> > > >
> > > > -static void nfs_mark_return_delegation(struct nfs_server
> > > > *server,
> > > > - struct nfs_delegation *delegation)
> > > > -{
> > > > - set_bit(NFS_DELEGATION_RETURN, &delegation->flags);
> > > > - set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client-
> > > > > cl_state);
> > > > -}
> > > > -
> > > > static bool nfs_server_mark_return_all_delegations(struct
> > > > nfs_server *server)
> > > > {
> > > > struct nfs_delegation *delegation;
> > > > diff --git a/fs/nfs/delegation.h b/fs/nfs/delegation.h
> > > > index c19b4fd20781..1c378992b7c0 100644
> > > > --- a/fs/nfs/delegation.h
> > > > +++ b/fs/nfs/delegation.h
> > > > @@ -36,6 +36,7 @@ enum {
> > > > NFS_DELEGATION_REVOKED,
> > > > NFS_DELEGATION_TEST_EXPIRED,
> > > > NFS_DELEGATION_INODE_FREEING,
> > > > + NFS_DELEGATION_RETURN_DELAYED,
> > > > };
> > > >
> > > > int nfs_inode_set_delegation(struct inode *inode, const struct
> > > > cred *cred,
> > > > diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
> > > > index 065cb04222a1..4c44322c2643 100644
> > > > --- a/fs/nfs/nfs4_fs.h
> > > > +++ b/fs/nfs/nfs4_fs.h
> > > > @@ -45,6 +45,7 @@ enum nfs4_client_state {
> > > > NFS4CLNT_RECALL_RUNNING,
> > > > NFS4CLNT_RECALL_ANY_LAYOUT_READ,
> > > > NFS4CLNT_RECALL_ANY_LAYOUT_RW,
> > > > + NFS4CLNT_DELEGRETURN_DELAYED,
> > > > };
> > > >
> > > > #define NFS4_RENEW_TIMEOUT 0x01
> > > > --
> > > > 2.31.1
> >
> > --
> > Trond Myklebust
> > Linux NFS client maintainer, Hammerspace
> > trond.myklebust@xxxxxxxxxxxxxxx
> >
> >
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx
