A few fixes of callback typecasting (for the upcoming ClangCFI)

* zio: avoid callback typecasting
* zil: avoid zil_itxg_clean() callback typecasting
* zpl: decouple zpl_readpage() into two separate callbacks
* nvpair: explicitly declare callbacks for xdr_array()
* linux/zfs_nvops: don't use external iput() as a callback
* zcp_synctask: don't use fnvlist_free() as a callback
* zvol: don't use ops->zv_free() as a callback for taskq_dispatch()

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Mark Maybee <mark.maybee@delphix.com>
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Closes #12260

module/zfs/zcp_synctask.c

@@ -54,6 +54,12 @@ typedef struct zcp_synctask_info {
 	int blocks_modified;
 } zcp_synctask_info_t;
 
+static void
+zcp_synctask_cleanup(void *arg)
+{
+	fnvlist_free(arg);
+}
+
 /*
  * Generic synctask interface for channel program syncfuncs.
  *
@@ -275,7 +281,7 @@ zcp_synctask_snapshot(lua_State *state, boolean_t sync, nvlist_t *err_details)
 	fnvlist_add_boolean(ddsa.ddsa_snaps, dsname);
 
 	zcp_cleanup_handler_t *zch = zcp_register_cleanup(state,
-	    (zcp_cleanup_t *)&fnvlist_free, ddsa.ddsa_snaps);
+	    zcp_synctask_cleanup, ddsa.ddsa_snaps);
 
 	err = zcp_sync_task(state, dsl_dataset_snapshot_check,
 	    dsl_dataset_snapshot_sync, &ddsa, sync, dsname);
@@ -363,7 +369,7 @@ zcp_synctask_inherit_prop(lua_State *state, boolean_t sync,
 	fnvlist_add_boolean(dpsa->dpsa_props, prop);
 
 	zcp_cleanup_handler_t *zch = zcp_register_cleanup(state,
-	    (zcp_cleanup_t *)&fnvlist_free, dpsa->dpsa_props);
+	    zcp_synctask_cleanup, dpsa->dpsa_props);
 
 	err = zcp_sync_task(state, zcp_synctask_inherit_prop_check,
 	    zcp_synctask_inherit_prop_sync, &zipa, sync, dsname);
@@ -402,7 +408,7 @@ zcp_synctask_bookmark(lua_State *state, boolean_t sync, nvlist_t *err_details)
 	fnvlist_add_string(bmarks, new, source);
 
 	zcp_cleanup_handler_t *zch = zcp_register_cleanup(state,
-	    (zcp_cleanup_t *)&fnvlist_free, bmarks);
+	    zcp_synctask_cleanup, bmarks);
 
 	dsl_bookmark_create_arg_t dbca = {
 		.dbca_bmarks = bmarks,
@@ -467,8 +473,7 @@ zcp_synctask_wrapper(lua_State *state)
 	 * Make sure err_details is properly freed, even if a fatal error is
 	 * thrown during the synctask.
 	 */
-	zch = zcp_register_cleanup(state,
-	    (zcp_cleanup_t *)&fnvlist_free, err_details);
+	zch = zcp_register_cleanup(state, zcp_synctask_cleanup, err_details);
 
 	zcp_synctask_info_t *info = lua_touserdata(state, lua_upvalueindex(1));
 	boolean_t sync = lua_toboolean(state, lua_upvalueindex(2));

module/zfs/zil.c

@@ -1822,12 +1822,13 @@ zil_itx_destroy(itx_t *itx)
  * so no locks are needed.
  */
 static void
-zil_itxg_clean(itxs_t *itxs)
+zil_itxg_clean(void *arg)
 {
 	itx_t *itx;
 	list_t *list;
 	avl_tree_t *t;
 	void *cookie;
+	itxs_t *itxs = arg;
 	itx_async_node_t *ian;
 
 	list = &itxs->i_sync_list;
@@ -2047,7 +2048,7 @@ zil_clean(zilog_t *zilog, uint64_t synced_txg)
 	ASSERT3P(zilog->zl_dmu_pool, !=, NULL);
 	ASSERT3P(zilog->zl_dmu_pool->dp_zil_clean_taskq, !=, NULL);
 	taskqid_t id = taskq_dispatch(zilog->zl_dmu_pool->dp_zil_clean_taskq,
-	    (void (*)(void *))zil_itxg_clean, clean_me, TQ_NOSLEEP);
+	    zil_itxg_clean, clean_me, TQ_NOSLEEP);
 	if (id == TASKQID_INVALID)
 		zil_itxg_clean(clean_me);
 }

module/zfs/zio.c

@@ -1891,8 +1891,8 @@ zio_taskq_dispatch(zio_t *zio, zio_taskq_type_t q, boolean_t cutinline)
 	 * to dispatch the zio to another taskq at the same time.
 	 */
 	ASSERT(taskq_empty_ent(&zio->io_tqent));
-	spa_taskq_dispatch_ent(spa, t, q, (task_func_t *)zio_execute, zio,
-	    flags, &zio->io_tqent);
+	spa_taskq_dispatch_ent(spa, t, q, zio_execute, zio, flags,
+	    &zio->io_tqent);
 }
 
 static boolean_t
@@ -1923,7 +1923,7 @@ zio_issue_async(zio_t *zio)
 }
 
 void
-zio_interrupt(zio_t *zio)
+zio_interrupt(void *zio)
 {
 	zio_taskq_dispatch(zio, ZIO_TASKQ_INTERRUPT, B_FALSE);
 }
@@ -1981,8 +1981,8 @@ zio_delay_interrupt(zio_t *zio)
 				 * OpenZFS's timeout_generic().
 				 */
 				tid = taskq_dispatch_delay(system_taskq,
-				    (task_func_t *)zio_interrupt,
-				    zio, TQ_NOSLEEP, expire_at_tick);
+				    zio_interrupt, zio, TQ_NOSLEEP,
+				    expire_at_tick);
 				if (tid == TASKQID_INVALID) {
 					/*
 					 * Couldn't allocate a task.  Just
@@ -2103,7 +2103,7 @@ static zio_pipe_stage_t *zio_pipeline[];
  * it is externally visible.
  */
 void
-zio_execute(zio_t *zio)
+zio_execute(void *zio)
 {
 	fstrans_cookie_t cookie;
 
@@ -2292,8 +2292,9 @@ zio_nowait(zio_t *zio)
  */
 
 static void
-zio_reexecute(zio_t *pio)
+zio_reexecute(void *arg)
 {
+	zio_t *pio = arg;
 	zio_t *cio, *cio_next;
 
 	ASSERT(pio->io_child_type == ZIO_CHILD_LOGICAL);
@@ -4788,8 +4789,7 @@ zio_done(zio_t *zio)
 			ASSERT(taskq_empty_ent(&zio->io_tqent));
 			spa_taskq_dispatch_ent(zio->io_spa,
 			    ZIO_TYPE_CLAIM, ZIO_TASKQ_ISSUE,
-			    (task_func_t *)zio_reexecute, zio, 0,
-			    &zio->io_tqent);
+			    zio_reexecute, zio, 0, &zio->io_tqent);
 		}
 		return (NULL);
 	}

module/zfs/zvol.c

@@ -1195,6 +1195,12 @@ zvol_create_minor(const char *name)
  * Remove minors for specified dataset including children and snapshots.
  */
 
+static void
+zvol_free_task(void *arg)
+{
+	ops->zv_free(arg);
+}
+
 void
 zvol_remove_minors_impl(const char *name)
 {
@@ -1243,8 +1249,8 @@ zvol_remove_minors_impl(const char *name)
 			mutex_exit(&zv->zv_state_lock);
 
 			/* Try parallel zv_free, if failed do it in place */
-			t = taskq_dispatch(system_taskq,
-			    (task_func_t *)ops->zv_free, zv, TQ_SLEEP);
+			t = taskq_dispatch(system_taskq, zvol_free_task, zv,
+			    TQ_SLEEP);
 			if (t == TASKQID_INVALID)
 				list_insert_head(&free_list, zv);
 		} else {