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Message-ID: <33e93b5d-9aa4-4752-8b01-c5c6e7e41359@huawei.com>
Date: Fri, 5 Sep 2025 08:59:52 +0800
From: Li Lingfeng <lilingfeng3@...wei.com>
To: Chuck Lever <chuck.lever@...cle.com>, Jeff Layton <jlayton@...nel.org>,
<neil@...wn.name>, <okorniev@...hat.com>, <Dai.Ngo@...cle.com>,
<tom@...pey.com>, <linux-nfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <yukuai1@...weicloud.com>, <houtao1@...wei.com>, <yi.zhang@...wei.com>,
<yangerkun@...wei.com>, <lilingfeng@...weicloud.com>,
<zhangjian496@...wei.com>, <bcodding@...hat.com>
Subject: Re: [PATCH v2] nfsd: remove long-standing revoked delegations by
force
在 2025/9/4 22:08, Chuck Lever 写道:
> On 9/3/25 8:15 AM, Jeff Layton wrote:
>> On Wed, 2025-09-03 at 19:59 +0800, Li Lingfeng wrote:
>>> When file access conflicts occur between clients, the server recalls
>>> delegations. If the client holding delegation fails to return it after
>>> a recall, nfs4_laundromat adds the delegation to cl_revoked list.
>>> This causes subsequent SEQUENCE operations to set the
>>> SEQ4_STATUS_RECALLABLE_STATE_REVOKED flag, forcing the client to
>>> validate all delegations and return the revoked one.
>>>
>>> However, if the client fails to return the delegation like this:
>>> nfs4_laundromat nfsd4_delegreturn
>>> unhash_delegation_locked
>>> list_add // add dp to reaplist
>>> // by dl_recall_lru
>>> list_del_init // delete dp from
>>> // reaplist
>>> destroy_delegation
>>> unhash_delegation_locked
>>> // do nothing but return false
>>> revoke_delegation
>>> list_add // add dp to cl_revoked
>>> // by dl_recall_lru
>>>
>>> The delegation will remain in the server's cl_revoked list while the
>>> client marks it revoked and won't find it upon detecting
>>> SEQ4_STATUS_RECALLABLE_STATE_REVOKED.
>>> This leads to a loop:
>>> the server persistently sets SEQ4_STATUS_RECALLABLE_STATE_REVOKED, and the
>>> client repeatedly tests all delegations, severely impacting performance
>>> when numerous delegations exist.
>>>
>>> Since abnormal delegations are removed from flc_lease via nfs4_laundromat
>>> --> revoke_delegation --> destroy_unhashed_deleg -->
>>> nfs4_unlock_deleg_lease --> kernel_setlease, and do not block new open
>>> requests indefinitely, retaining such a delegation on the server is
>>> unnecessary.
>>>
>>> Reported-by: Zhang Jian <zhangjian496@...wei.com>
>>> Fixes: 3bd64a5ba171 ("nfsd4: implement SEQ4_STATUS_RECALLABLE_STATE_REVOKED")
>>> Closes: https://lore.kernel.org/all/ff8debe9-6877-4cf7-ba29-fc98eae0ffa0@huawei.com/
>>> Signed-off-by: Li Lingfeng <lilingfeng3@...wei.com>
>>> ---
>>> Changes in v2:
>>> 1) Set SC_STATUS_CLOSED unconditionally in destroy_delegation();
>>> 2) Determine whether to remove the delegation based on SC_STATUS_CLOSED,
>>> rather than by timeout;
>>> 3) Modify the commit message.
>>> fs/nfsd/nfs4state.c | 20 ++++++++++++++++++++
>>> 1 file changed, 20 insertions(+)
>>>
>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>>> index 88c347957da5..bb9e1df4e41f 100644
>>> --- a/fs/nfsd/nfs4state.c
>>> +++ b/fs/nfsd/nfs4state.c
>>> @@ -1336,6 +1336,11 @@ static void destroy_delegation(struct nfs4_delegation *dp)
>>>
>>> spin_lock(&state_lock);
>>> unhashed = unhash_delegation_locked(dp, SC_STATUS_CLOSED);
>>> + /*
>>> + * Unconditionally set SC_STATUS_CLOSED, regardless of whether the
>>> + * delegation is hashed, to mark the current delegation as invalid.
>>> + */
>>> + dp->dl_stid.sc_status |= SC_STATUS_CLOSED;
>>> spin_unlock(&state_lock);
>>> if (unhashed)
>>> destroy_unhashed_deleg(dp);
>>> @@ -4326,6 +4331,8 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>>> int buflen;
>>> struct net *net = SVC_NET(rqstp);
>>> struct nfsd_net *nn = net_generic(net, nfsd_net_id);
>>> + struct list_head *pos, *next;
>>> + struct nfs4_delegation *dp;
>>>
>> nit: These could be moved inside the if statement below.
>>
>>> if (resp->opcnt != 1)
>>> return nfserr_sequence_pos;
>>> @@ -4470,6 +4477,19 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>>> default:
>>> seq->status_flags = 0;
>>> }
>> I wouldn't mind a comment here that explains why we have to do this.
>> This is the sort of thing that will have us all scratching our heads in
>> a few years.
>>
>>> + if (!list_empty(&clp->cl_revoked)) {
>>> + spin_lock(&clp->cl_lock);
>>> + list_for_each_safe(pos, next, &clp->cl_revoked) {
>>> + dp = list_entry(pos, struct nfs4_delegation, dl_recall_lru);
>>> + if (dp->dl_stid.sc_status & SC_STATUS_CLOSED) {
>>> + list_del_init(&dp->dl_recall_lru);
>>> + spin_unlock(&clp->cl_lock);
>>> + nfs4_put_stid(&dp->dl_stid);
>>> + spin_lock(&clp->cl_lock);
>>> + }
>>> + }
>>> + spin_unlock(&clp->cl_lock);
>>> + }
>> nit: I'd move the if statement below inside the above if statement. No
>> need to check list_empty() twice if it was empty the first time. Maybe
>> the compiler papers over this and only does it once?
>>
>>> if (!list_empty(&clp->cl_revoked))
>>> seq->status_flags |= SEQ4_STATUS_RECALLABLE_STATE_REVOKED;
>>> if (atomic_read(&clp->cl_admin_revoked))
>> Otherwise, this looks great. Thanks for the patch!
>>
>> Reviewed-by: Jeff Layton <jlayton@...nel.org>
> Li, I'm assuming you are going to address Jeff's additional comments
> here and send another revision of this patch. So I'm waiting for
> another version... let me know if you plan not to send one.
>
Thank you for the reminder. I will send a new patch soon.
Thanks,
Lingfeng
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