Re: [PATCH RFC v16 04/11] NFSD: Update nfsd_breaker_owns_lease() to handle courtesy clients

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On 3/15/22 8:13 AM, Bruce Fields wrote:
On Sun, Mar 13, 2022 at 04:04:21PM +0000, Chuck Lever III wrote:

On Mar 11, 2022, at 9:13 PM, Dai Ngo <dai.ngo@xxxxxxxxxx> wrote:

Update nfsd_breaker_owns_lease() to handle delegation conflict
with courtesy clients. If conflict was caused by courtesy client
then discard the courtesy client by setting CLIENT_EXPIRED and
return conflict resolved. Client with CLIENT_EXPIRED is expired
by the laundromat.

Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
---
fs/nfsd/nfs4state.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 583ac807e98d..2beb0972de88 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4713,6 +4713,28 @@ nfsd_break_deleg_cb(struct file_lock *fl)
	return ret;
}

+static bool
+nfs4_check_and_expire_courtesy_client(struct nfs4_client *clp)
+{
+	/*
+	 * need to sync with courtesy client trying to reconnect using
+	 * the cl_cs_lock, nn->client_lock can not be used since this
+	 * function is called with the fl_lck held.
+	 */
+	spin_lock(&clp->cl_cs_lock);
+	if (test_bit(NFSD4_CLIENT_EXPIRED, &clp->cl_flags)) {
+		spin_unlock(&clp->cl_cs_lock);
+		return true;
+	}
+	if (test_bit(NFSD4_CLIENT_COURTESY, &clp->cl_flags)) {
+		set_bit(NFSD4_CLIENT_EXPIRED, &clp->cl_flags);
+		spin_unlock(&clp->cl_cs_lock);
+		return true;
+	}
+	spin_unlock(&clp->cl_cs_lock);
Same comment as on the previous patch.  ALso, this is the second time
we've used this logic, please define a

	static bool expire_client_if_courtesy(struct nfs4_client *clp)

and call it from both places.

I will replace the similar code in nfsd4_lm_lock_expired with
a call to nfs4_check_and_expire_courtesy_client.


+	return false;
+}
+
/**
  * nfsd_breaker_owns_lease - Check if lease conflict was resolved
  * @fl: Lock state to check
@@ -4727,6 +4749,10 @@ static bool nfsd_breaker_owns_lease(struct file_lock *fl)
	struct svc_rqst *rqst;
	struct nfs4_client *clp;

+	clp = dl->dl_stid.sc_client;
+	if (nfs4_check_and_expire_courtesy_client(clp))
Since you'll need to fix the kernel robot issue in 1/11, when you
repost, can you also just pass dl->dl_stid.sc_client directly to
nfs4_check_and_expire_courtesy_client() here?
Agreed.

This client is quite different from the one we look up from the task a
little later, and I'd just rather not have both represented by the same
variable.

fix in v17.

-Dai


--b.



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