Re: [PATCH 2/2] NFS: Limit the number of retries

[Wenle Chen]

Trond Myklebust 於 2020/11/3 上午1:45 寫道:
> On Tue, 2020-11-03 at 00:24 +0800, Wenle Chen wrote:
> >    We can't wait forever, even if the state
> > is always delayed.
> >
> > Signed-off-by: Wenle Chen <chenwenle@xxxxxxxxxx>
> > ---
> >   fs/nfs/nfs4proc.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> > index f6b5dc792b33..bb2316bf13f6 100644
> > --- a/fs/nfs/nfs4proc.c
> > +++ b/fs/nfs/nfs4proc.c
> > @@ -7390,15 +7390,17 @@ int nfs4_lock_delegation_recall(struct
> > file_lock *fl, struct nfs4_state *state,
> >   {
> >          struct nfs_server *server = NFS_SERVER(state->inode);
> >          int err;
> > +       int retry = 3;
> >   
> >          err = nfs4_set_lock_state(state, fl);
> >          if (err != 0)
> >                  return err;
> >          do {
> >                  err = _nfs4_do_setlk(state, F_SETLK, fl,
> > NFS_LOCK_NEW);
> > -               if (err != -NFS4ERR_DELAY)
> > +               if (err != -NFS4ERR_DELAY || retry == 0)
> >                          break;
> >                  ssleep(1);
> > +               --retry;
> >          } while (1);
> >          return nfs4_handle_delegation_recall_error(server, state,
> > stateid, fl, err);
> >   }
>
> This patch will just cause the locks to be silently lost, no?
This loop was introduced in commit 3d7a9520f0c3e to simplify the delay 
retry loop. Before this, the function nfs4_lock_delegation_recall would 
return a -EAGAIN to do a whole retry loop.

When we retried three times and waited three seconds, it was still in 
delay. I think we can get a whole loop and check the other points if it 
was changed or not. It is just a proposal.