Re: [PATCH 1/1] Fixing infinite state recovery loop due to failed delegation return

From: Trond Myklebust <trond.myklebust@primarydata.com>
To: Olga Kornievskaia <aglo@umich.edu>
Cc: linux-nfs <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH 1/1] Fixing infinite state recovery loop due to failed delegation return
Date: Tue, 4 Nov 2014 19:14:14 -0500	[thread overview]
Message-ID: <CAHQdGtQWg+Fiyn7vH9pjU1GR-TKvMp+gcR7ssaA1zESQ8JdVsw@mail.gmail.com> (raw)
In-Reply-To: <CAN-5tyHVoJ60z7WBaCYvUN3GsCEGh9jGc0evRCuiVt2aA6zP0g@mail.gmail.com>

On Tue, Nov 4, 2014 at 6:22 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> Trond, can you please respond to the patch?
>
> As per earlier conversation, in this solution, state recovery is
> initiated which marks the locks lost.
>
> Please either accept this patch or let me know what needs to be fixed.
>

Please see the 3 fixes I just sent out concerning delegation recovery
w.r.t. NFSv4+NFSv4.1. In addition, we need to handle the case you
patch attempts to address (however see the question I have below).

> Thank you.
>
> On Mon, Nov 3, 2014 at 9:36 AM, Olga Kornievskaia <kolga@netapp.com> wrote:
>> If we get a bad-stateid-type of error when we send OPEN with delegate_cur
>> to return currently held delegation, we shouldn't be trying to reclaim locks
>> associated with that delegation state_id because we don't have an
>> open_stateid to be used for the LOCK operation. Thus, we should
>> return an error from the nfs4_open_delegation_recall() in that case.
>>
>> Furthermore, if an error occurs the delegation code will call
>> nfs_abort_delegation_return() which sets again the NFS4CLNT_DELEGRETURN
>> flags in the state and it leads the state manager to into an infinite loop
>> for trying to reclaim the delegated state.
>>
>> Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
>> ---
>>  fs/nfs/delegation.c |    5 +++--
>>  fs/nfs/nfs4proc.c   |    2 +-
>>  2 files changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
>> index 5853f53..8016d89 100644
>> --- a/fs/nfs/delegation.c
>> +++ b/fs/nfs/delegation.c
>> @@ -394,7 +394,7 @@ static int nfs_end_delegation_return(struct inode *inode, struct nfs_delegation
>>                 err = nfs4_wait_clnt_recover(clp);
>>         } while (err == 0);
>>
>> -       if (err) {
>> +       if (err && err != -EIO) {
>>                 nfs_abort_delegation_return(delegation, clp);

This exception for EIO now has me worried. If we detach the
delegation, then it looks to me as if we will never send a
FREE_STATEID, as required for the case of NFSv4.1.

>>                 goto out;
>>         }
>> @@ -458,7 +458,8 @@ restart:
>>                         iput(inode);
>>                         if (!err)
>>                                 goto restart;
>> -                       set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);
>> +                       if (err != -EIO)
>> +                               set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);

Please explain why this is needed. If we've cleared the bad
delegation, then why should we not attempt to return any others that
may be pending?

>>                         return err;
>>                 }
>>         }
>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>> index 5aa55c1..6871055 100644
>> --- a/fs/nfs/nfs4proc.c
>> +++ b/fs/nfs/nfs4proc.c
>> @@ -1655,7 +1655,7 @@ static int nfs4_handle_delegation_recall_error(struct nfs_server *server, struct
>>                         nfs_inode_find_state_and_recover(state->inode,
>>                                         stateid);
>>                         nfs4_schedule_stateid_recovery(server, state);
>> -                       return 0;
>> +                       return -EIO;
>>                 case -NFS4ERR_DELAY:
>>                 case -NFS4ERR_GRACE:
>>                         set_bit(NFS_DELEGATED_STATE, &state->flags);
>> --
>> 1.7.1
>>
>> --
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-- 
Trond Myklebust

Linux NFS client maintainer, PrimaryData

trond.myklebust@primarydata.com