spa_taskq_dispatch_ent: simplify arguments

This renames it to spa_taskq_dispatch(), and reduces and simplifies its
arguments based on these observations from its two call sites:

- arg is always the zio, so it can be typed that way, and we don't need
  to provide it twice;
- ent is always &zio->io_tqent, and zio is always provided, so we can
  use it directly;
- the only flag used is TQ_FRONT, which can just be a bool;
- zio != NULL was part of the "use allocator" test, but it never would
  have got that far, because that arg was only set to NULL in the
  reexecute path, which is forced to type CLAIM, so the condition would
  fail at t == WRITE anyway.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Signed-off-by: Rob Norris <[email protected]>

include/sys/spa_impl.h

@@ -478,8 +478,8 @@ struct spa {
 extern char *spa_config_path;
 extern const char *zfs_deadman_failmode;
 extern uint_t spa_slop_shift;
-extern void spa_taskq_dispatch_ent(spa_t *spa, zio_type_t t, zio_taskq_type_t q,
-    task_func_t *func, void *arg, uint_t flags, taskq_ent_t *ent, zio_t *zio);
+extern void spa_taskq_dispatch(spa_t *spa, zio_type_t t, zio_taskq_type_t q,
+    task_func_t *func, zio_t *zio, boolean_t cutinline);
 extern void spa_load_spares(spa_t *spa);
 extern void spa_load_l2cache(spa_t *spa);
 extern sysevent_t *spa_event_create(spa_t *spa, vdev_t *vd, nvlist_t *hist_nvl,

module/zfs/spa.c

@@ -34,6 +34,7 @@
  * Copyright (c) 2017, Intel Corporation.
  * Copyright (c) 2021, Colm Buckley <[email protected]>
  * Copyright (c) 2023 Hewlett Packard Enterprise Development LP.
+ * Copyright (c) 2024, Klara Inc.
  */
 
 /*
@@ -1485,26 +1486,34 @@ spa_taskq_write_param(ZFS_MODULE_PARAM_ARGS)
  * on the taskq itself.
  */
 void
-spa_taskq_dispatch_ent(spa_t *spa, zio_type_t t, zio_taskq_type_t q,
-    task_func_t *func, void *arg, uint_t flags, taskq_ent_t *ent,
-    zio_t *zio)
+spa_taskq_dispatch(spa_t *spa, zio_type_t t, zio_taskq_type_t q,
+    task_func_t *func, zio_t *zio, boolean_t cutinline)
 {
 	spa_taskqs_t *tqs = &spa->spa_zio_taskq[t][q];
 	taskq_t *tq;
 
 	ASSERT3P(tqs->stqs_taskq, !=, NULL);
 	ASSERT3U(tqs->stqs_count, !=, 0);
 
+	/*
+	 * NB: We are assuming that the zio can only be dispatched
+	 * to a single taskq at a time.  It would be a grievous error
+	 * to dispatch the zio to another taskq at the same time.
+	 */
+	ASSERT(zio);
+	ASSERT(taskq_empty_ent(&zio->io_tqent));
+
 	if (tqs->stqs_count == 1) {
 		tq = tqs->stqs_taskq[0];
 	} else if ((t == ZIO_TYPE_WRITE) && (q == ZIO_TASKQ_ISSUE) &&
-	    (zio != NULL) && ZIO_HAS_ALLOCATOR(zio)) {
+	    ZIO_HAS_ALLOCATOR(zio)) {
 		tq = tqs->stqs_taskq[zio->io_allocator % tqs->stqs_count];
 	} else {
 		tq = tqs->stqs_taskq[((uint64_t)gethrtime()) % tqs->stqs_count];
 	}
 
-	taskq_dispatch_ent(tq, func, arg, flags, ent);
+	taskq_dispatch_ent(tq, func, zio, cutinline ? TQ_FRONT : 0,
+	    &zio->io_tqent);
 }
 
 static void

module/zfs/zio.c

@@ -2023,7 +2023,6 @@ zio_taskq_dispatch(zio_t *zio, zio_taskq_type_t q, boolean_t cutinline)
 {
 	spa_t *spa = zio->io_spa;
 	zio_type_t t = zio->io_type;
-	int flags = (cutinline ? TQ_FRONT : 0);
 
 	/*
 	 * If we're a config writer or a probe, the normal issue and
@@ -2050,14 +2049,7 @@ zio_taskq_dispatch(zio_t *zio, zio_taskq_type_t q, boolean_t cutinline)
 
 	ASSERT3U(q, <, ZIO_TASKQ_TYPES);
 
-	/*
-	 * NB: We are assuming that the zio can only be dispatched
-	 * to a single taskq at a time.  It would be a grievous error
-	 * 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, zio_execute, zio, flags,
-	    &zio->io_tqent, zio);
+	spa_taskq_dispatch(spa, t, q, zio_execute, zio, cutinline);
 }
 
 static boolean_t
@@ -5005,10 +4997,9 @@ zio_done(zio_t *zio)
 			 * Reexecution is potentially a huge amount of work.
 			 * Hand it off to the otherwise-unused claim taskq.
 			 */
-			ASSERT(taskq_empty_ent(&zio->io_tqent));
-			spa_taskq_dispatch_ent(zio->io_spa,
+			spa_taskq_dispatch(zio->io_spa,
 			    ZIO_TYPE_CLAIM, ZIO_TASKQ_ISSUE,
-			    zio_reexecute, zio, 0, &zio->io_tqent, NULL);
+			    zio_reexecute, zio, B_FALSE);
 		}
 		return (NULL);
 	}