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Date:   Tue, 15 Mar 2022 13:20:51 -0400
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     dai.ngo@oracle.com
Cc:     chuck.lever@oracle.com, jlayton@redhat.com,
        viro@zeniv.linux.org.uk, linux-nfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH RFC v16 03/11] NFSD: Add lm_lock_expired call out
Message-ID: <20220315172051.GD19168@fieldses.org>
References: <1647051215-2873-1-git-send-email-dai.ngo@oracle.com>
 <1647051215-2873-4-git-send-email-dai.ngo@oracle.com>
 <20220315150245.GA19168@fieldses.org>
 <1e1ff6a1-86cf-99d4-13ad-45352e58fe73@oracle.com>
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In-Reply-To: <1e1ff6a1-86cf-99d4-13ad-45352e58fe73@oracle.com>
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On Tue, Mar 15, 2022 at 09:26:46AM -0700, dai.ngo@oracle.com wrote:
> 
> On 3/15/22 8:02 AM, J. Bruce Fields wrote:
> >On Fri, Mar 11, 2022 at 06:13:27PM -0800, Dai Ngo wrote:
> >>Add callout function nfsd4_lm_lock_expired for lm_lock_expired.
> >>If lock request has conflict with courtesy client then expire the
> >>courtesy client and return no conflict to caller.
> >>
> >>Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> >>---
> >>  fs/nfsd/nfs4state.c | 37 +++++++++++++++++++++++++++++++++++++
> >>  1 file changed, 37 insertions(+)
> >>
> >>diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> >>index a65d59510681..583ac807e98d 100644
> >>--- a/fs/nfsd/nfs4state.c
> >>+++ b/fs/nfsd/nfs4state.c
> >>@@ -6578,10 +6578,47 @@ nfsd4_lm_notify(struct file_lock *fl)
> >>  	}
> >>  }
> >>+/**
> >>+ * nfsd4_lm_lock_expired - check if lock conflict can be resolved.
> >>+ *
> >>+ * @fl: pointer to file_lock with a potential conflict
> >>+ * Return values:
> >>+ *   %false: real conflict, lock conflict can not be resolved.
> >>+ *   %true: no conflict, lock conflict was resolved.
> >>+ *
> >>+ * Note that this function is called while the flc_lock is held.
> >>+ */
> >>+static bool
> >>+nfsd4_lm_lock_expired(struct file_lock *fl)
> >>+{
> >>+	struct nfs4_lockowner *lo;
> >>+	struct nfs4_client *clp;
> >>+	bool rc = false;
> >>+
> >>+	if (!fl)
> >>+		return false;
> >>+	lo = (struct nfs4_lockowner *)fl->fl_owner;
> >>+	clp = lo->lo_owner.so_client;
> >>+
> >>+	/* need to sync with courtesy client trying to reconnect */
> >>+	spin_lock(&clp->cl_cs_lock);
> >>+	if (test_bit(NFSD4_CLIENT_EXPIRED, &clp->cl_flags))
> >>+		rc = true;
> >>+	else {
> >>+		if (test_bit(NFSD4_CLIENT_COURTESY, &clp->cl_flags)) {
> >>+			set_bit(NFSD4_CLIENT_EXPIRED, &clp->cl_flags);
> >>+			rc =  true;
> >>+		}
> >>+	}
> >I'd prefer:
> >
> >	if (test_bit(NFSD4_CLIENT_COURTESY, &clp->cl_flags))
> >		set_bit(NFSD4_CLIENT_EXPIRED, &clp->cl_flags);
> 
> we also need to set rc to true here.

No, the next line does it because we set the EXPIRED bit.

--b.

> 
> >	if (test_bit(NFSD4_CLIENT_EXPIRED, &clp->cl_flags))
> >		rc = true;
> 
> With v16 we need to check for NFSD4_CLIENT_EXPIRED first then
> NFSD4_CLIENT_COURTESY because both flags can be set. In the
> next patch version, we will clear NFSD4_CLIENT_COURTESY when
> setting NFSD4_CLIENT_EXPIRED so the order of check does not
> matter.
> 
> >
> >Same result, but more compact and straightforward, I think.
> 
> Chuck wants to replace the bits used for courtesy client in
> cl_flags with a  separate u8 field so it does not have to use
> bit operation to set/test.
> 
> -Dai
> 
> >
> >--b.
> >
> >>+	spin_unlock(&clp->cl_cs_lock);
> >>+	return rc;
> >>+}
> >>+
> >>  static const struct lock_manager_operations nfsd_posix_mng_ops  = {
> >>  	.lm_notify = nfsd4_lm_notify,
> >>  	.lm_get_owner = nfsd4_lm_get_owner,
> >>  	.lm_put_owner = nfsd4_lm_put_owner,
> >>+	.lm_lock_expired = nfsd4_lm_lock_expired,
> >>  };
> >>  static inline void
> >>-- 
> >>2.9.5