NFSD: Add a laundromat reaper for async copy state

RFC 7862 Section 4.8 states:

> A copy offload stateid will be valid until either (A) the client
> or server restarts or (B) the client returns the resource by
> issuing an OFFLOAD_CANCEL operation or the client replies to a
> CB_OFFLOAD operation.

Instead of releasing async copy state when the CB_OFFLOAD callback
completes, now let it live until the next laundromat run after the
callback completes.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4proc.c

@@ -1308,6 +1308,39 @@ bool nfsd4_has_active_async_copies(struct nfs4_client *clp)
 	return result;
 }
 
+/**
+ * nfsd4_async_copy_reaper - Purge completed copies
+ * @nn: Network namespace with possible active copy information
+ */
+void nfsd4_async_copy_reaper(struct nfsd_net *nn)
+{
+	struct nfs4_client *clp;
+	struct nfsd4_copy *copy;
+	LIST_HEAD(reaplist);
+
+	spin_lock(&nn->client_lock);
+	list_for_each_entry(clp, &nn->client_lru, cl_lru) {
+		struct list_head *pos, *next;
+
+		spin_lock(&clp->async_lock);
+		list_for_each_safe(pos, next, &clp->async_copies) {
+			copy = list_entry(pos, struct nfsd4_copy, copies);
+			if (test_bit(NFSD4_COPY_F_OFFLOAD_DONE, &copy->cp_flags)) {
+				list_del_init(&copy->copies);
+				list_add(&copy->copies, &reaplist);
+			}
+		}
+		spin_unlock(&clp->async_lock);
+	}
+	spin_unlock(&nn->client_lock);
+
+	while (!list_empty(&reaplist)) {
+		copy = list_first_entry(&reaplist, struct nfsd4_copy, copies);
+		list_del_init(&copy->copies);
+		cleanup_async_copy(copy);
+	}
+}
+
 static void nfs4_put_copy(struct nfsd4_copy *copy)
 {
 	if (!refcount_dec_and_test(&copy->refcount))
@@ -1637,7 +1670,7 @@ static void nfsd4_cb_offload_release(struct nfsd4_callback *cb)
 	struct nfsd4_copy *copy =
 		container_of(cbo, struct nfsd4_copy, cp_cb_offload);
 
-	cleanup_async_copy(copy);
+	set_bit(NFSD4_COPY_F_OFFLOAD_DONE, &copy->cp_flags);
 }
 
 static int nfsd4_cb_offload_done(struct nfsd4_callback *cb,

fs/nfsd/nfs4state.c

@@ -6574,6 +6574,7 @@ nfs4_laundromat(struct nfsd_net *nn)
 			_free_cpntf_state_locked(nn, cps);
 	}
 	spin_unlock(&nn->s2s_cp_lock);
+	nfsd4_async_copy_reaper(nn);
 	nfs4_get_client_reaplist(nn, &reaplist, &lt);
 	nfs4_process_client_reaplist(&reaplist);
 

fs/nfsd/state.h

@@ -738,6 +738,7 @@ extern void nfsd4_init_cb(struct nfsd4_callback *cb, struct nfs4_client *clp,
 extern bool nfsd4_run_cb(struct nfsd4_callback *cb);
 extern void nfsd4_shutdown_callback(struct nfs4_client *);
 extern void nfsd4_shutdown_copy(struct nfs4_client *clp);
+void nfsd4_async_copy_reaper(struct nfsd_net *nn);
 bool nfsd4_has_active_async_copies(struct nfs4_client *clp);
 extern struct nfs4_client_reclaim *nfs4_client_to_reclaim(struct xdr_netobj name,
 				struct xdr_netobj princhash, struct nfsd_net *nn);

fs/nfsd/xdr4.h

@@ -695,6 +695,7 @@ struct nfsd4_copy {
 #define NFSD4_COPY_F_SYNCHRONOUS	(2)
 #define NFSD4_COPY_F_COMMITTED		(3)
 #define NFSD4_COPY_F_COMPLETED		(4)
+#define NFSD4_COPY_F_OFFLOAD_DONE	(5)
 
 	/* response */
 	__be32			nfserr;