Use list_remove_head() where possible.

... instead of list_head() + list_remove().  On FreeBSD the list
functions are not inlined, so in addition to more compact code
this also saves another function call.

Reviewed-by: Brian Atkinson <batkinson@lanl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #14955

cmd/zed/agents/zfs_agents.c

@@ -369,9 +369,7 @@ zfs_agent_consumer_thread(void *arg)
 			return (NULL);
 		}
 
-		if ((event = (list_head(&agent_events))) != NULL) {
-			list_remove(&agent_events, event);
-
+		if ((event = list_remove_head(&agent_events)) != NULL) {
 			(void) pthread_mutex_unlock(&agent_lock);
 
 			/* dispatch to all event subscribers */
@@ -434,8 +432,7 @@ zfs_agent_fini(void)
 	(void) pthread_join(g_agents_tid, NULL);
 
 	/* drain any pending events */
-	while ((event = (list_head(&agent_events))) != NULL) {
-		list_remove(&agent_events, event);
+	while ((event = list_remove_head(&agent_events)) != NULL) {
 		nvlist_free(event->ae_nvl);
 		free(event);
 	}

cmd/zed/agents/zfs_mod.c

@@ -1288,17 +1288,14 @@ zfs_slm_fini(void)
 		tpool_destroy(g_tpool);
 	}
 
-	while ((pool = (list_head(&g_pool_list))) != NULL) {
-		list_remove(&g_pool_list, pool);
+	while ((pool = list_remove_head(&g_pool_list)) != NULL) {
 		zpool_close(pool->uap_zhp);
 		free(pool);
 	}
 	list_destroy(&g_pool_list);
 
-	while ((device = (list_head(&g_device_list))) != NULL) {
-		list_remove(&g_device_list, device);
+	while ((device = list_remove_head(&g_device_list)) != NULL)
 		free(device);
-	}
 	list_destroy(&g_device_list);
 
 	libzfs_fini(g_zfshdl);

module/os/freebsd/zfs/zfs_acl.c

@@ -495,10 +495,8 @@ zfs_acl_release_nodes(zfs_acl_t *aclp)
 {
 	zfs_acl_node_t *aclnode;
 
-	while ((aclnode = list_head(&aclp->z_acl))) {
-		list_remove(&aclp->z_acl, aclnode);
+	while ((aclnode = list_remove_head(&aclp->z_acl)))
 		zfs_acl_node_free(aclnode);
-	}
 	aclp->z_acl_count = 0;
 	aclp->z_acl_bytes = 0;
 }

module/os/linux/zfs/zfs_acl.c

@@ -493,10 +493,8 @@ zfs_acl_release_nodes(zfs_acl_t *aclp)
 {
 	zfs_acl_node_t *aclnode;
 
-	while ((aclnode = list_head(&aclp->z_acl))) {
-		list_remove(&aclp->z_acl, aclnode);
+	while ((aclnode = list_remove_head(&aclp->z_acl)))
 		zfs_acl_node_free(aclnode);
-	}
 	aclp->z_acl_count = 0;
 	aclp->z_acl_bytes = 0;
 }

module/zfs/arc.c

@@ -7866,8 +7866,7 @@ arc_fini(void)
 	taskq_destroy(arc_prune_taskq);
 
 	mutex_enter(&arc_prune_mtx);
-	while ((p = list_head(&arc_prune_list)) != NULL) {
-		list_remove(&arc_prune_list, p);
+	while ((p = list_remove_head(&arc_prune_list)) != NULL) {
 		zfs_refcount_remove(&p->p_refcnt, &arc_prune_list);
 		zfs_refcount_destroy(&p->p_refcnt);
 		kmem_free(p, sizeof (*p));
@@ -8324,20 +8323,14 @@ out:
 static void
 l2arc_do_free_on_write(void)
 {
-	list_t *buflist;
-	l2arc_data_free_t *df, *df_prev;
+	l2arc_data_free_t *df;
 
 	mutex_enter(&l2arc_free_on_write_mtx);
-	buflist = l2arc_free_on_write;
-
-	for (df = list_tail(buflist); df; df = df_prev) {
-		df_prev = list_prev(buflist, df);
+	while ((df = list_remove_head(l2arc_free_on_write)) != NULL) {
 		ASSERT3P(df->l2df_abd, !=, NULL);
 		abd_free(df->l2df_abd);
-		list_remove(buflist, df);
 		kmem_free(df, sizeof (l2arc_data_free_t));
 	}
-
 	mutex_exit(&l2arc_free_on_write_mtx);
 }
 

module/zfs/bplist.c

@@ -65,9 +65,8 @@ bplist_iterate(bplist_t *bpl, bplist_itor_t *func, void *arg, dmu_tx_t *tx)
 	bplist_entry_t *bpe;
 
 	mutex_enter(&bpl->bpl_lock);
-	while ((bpe = list_head(&bpl->bpl_list))) {
+	while ((bpe = list_remove_head(&bpl->bpl_list))) {
 		bplist_iterate_last_removed = bpe;
-		list_remove(&bpl->bpl_list, bpe);
 		mutex_exit(&bpl->bpl_lock);
 		func(arg, &bpe->bpe_blk, tx);
 		kmem_free(bpe, sizeof (*bpe));
@@ -82,10 +81,7 @@ bplist_clear(bplist_t *bpl)
 	bplist_entry_t *bpe;
 
 	mutex_enter(&bpl->bpl_lock);
-	while ((bpe = list_head(&bpl->bpl_list))) {
-		bplist_iterate_last_removed = bpe;
-		list_remove(&bpl->bpl_list, bpe);
+	while ((bpe = list_remove_head(&bpl->bpl_list)))
 		kmem_free(bpe, sizeof (*bpe));
-	}
 	mutex_exit(&bpl->bpl_lock);
 }

module/zfs/dmu_objset.c

@@ -1755,9 +1755,8 @@ dmu_objset_sync(objset_t *os, zio_t *pio, dmu_tx_t *tx)
 	taskq_wait(dmu_objset_pool(os)->dp_sync_taskq);
 
 	list = &DMU_META_DNODE(os)->dn_dirty_records[txgoff];
-	while ((dr = list_head(list)) != NULL) {
+	while ((dr = list_remove_head(list)) != NULL) {
 		ASSERT0(dr->dr_dbuf->db_level);
-		list_remove(list, dr);
 		zio_nowait(dr->dr_zio);
 	}
 

module/zfs/dmu_tx.c

@@ -1396,8 +1396,7 @@ dmu_tx_do_callbacks(list_t *cb_list, int error)
 {
 	dmu_tx_callback_t *dcb;
 
-	while ((dcb = list_tail(cb_list)) != NULL) {
-		list_remove(cb_list, dcb);
+	while ((dcb = list_remove_tail(cb_list)) != NULL) {
 		dcb->dcb_func(dcb->dcb_data, error);
 		kmem_free(dcb, sizeof (dmu_tx_callback_t));
 	}

module/zfs/dsl_dataset.c

@@ -3782,8 +3782,7 @@ snaplist_destroy(list_t *l, const void *tag)
 	if (l == NULL || !list_link_active(&l->list_head))
 		return;
 
-	while ((snap = list_tail(l)) != NULL) {
-		list_remove(l, snap);
+	while ((snap = list_remove_tail(l)) != NULL) {
 		dsl_dataset_rele(snap->ds, tag);
 		kmem_free(snap, sizeof (*snap));
 	}

module/zfs/dsl_dir.c

@@ -1490,7 +1490,7 @@ dsl_dir_tempreserve_clear(void *tr_cookie, dmu_tx_t *tx)
 	if (tr_cookie == NULL)
 		return;
 
-	while ((tr = list_head(tr_list)) != NULL) {
+	while ((tr = list_remove_head(tr_list)) != NULL) {
 		if (tr->tr_ds) {
 			mutex_enter(&tr->tr_ds->dd_lock);
 			ASSERT3U(tr->tr_ds->dd_tempreserved[txgidx], >=,
@@ -1500,7 +1500,6 @@ dsl_dir_tempreserve_clear(void *tr_cookie, dmu_tx_t *tx)
 		} else {
 			arc_tempreserve_clear(tr->tr_size);
 		}
-		list_remove(tr_list, tr);
 		kmem_free(tr, sizeof (struct tempreserve));
 	}
 

module/zfs/dsl_scan.c

@@ -3437,10 +3437,8 @@ scan_io_queues_run_one(void *arg)
 	 * If we were suspended in the middle of processing,
 	 * requeue any unfinished sios and exit.
 	 */
-	while ((sio = list_head(&sio_list)) != NULL) {
-		list_remove(&sio_list, sio);
+	while ((sio = list_remove_head(&sio_list)) != NULL)
 		scan_io_queue_insert_impl(queue, sio);
-	}
 
 	queue->q_zio = NULL;
 	mutex_exit(q_lock);

module/zfs/fm.c

@@ -148,8 +148,7 @@ zfs_zevent_drain(zevent_t *ev)
 	list_remove(&zevent_list, ev);
 
 	/* Remove references to this event in all private file data */
-	while ((ze = list_head(&ev->ev_ze_list)) != NULL) {
-		list_remove(&ev->ev_ze_list, ze);
+	while ((ze = list_remove_head(&ev->ev_ze_list)) != NULL) {
 		ze->ze_zevent = NULL;
 		ze->ze_dropped++;
 	}

module/zfs/refcount.c

@@ -88,14 +88,11 @@ zfs_refcount_destroy_many(zfs_refcount_t *rc, uint64_t number)
 	reference_t *ref;
 
 	ASSERT3U(rc->rc_count, ==, number);
-	while ((ref = list_head(&rc->rc_list))) {
-		list_remove(&rc->rc_list, ref);
+	while ((ref = list_remove_head(&rc->rc_list)))
 		kmem_cache_free(reference_cache, ref);
-	}
 	list_destroy(&rc->rc_list);
 
-	while ((ref = list_head(&rc->rc_removed))) {
-		list_remove(&rc->rc_removed, ref);
+	while ((ref = list_remove_head(&rc->rc_removed))) {
 		kmem_cache_free(reference_history_cache, ref->ref_removed);
 		kmem_cache_free(reference_cache, ref);
 	}

module/zfs/spa.c

@@ -1609,16 +1609,16 @@ spa_unload_log_sm_metadata(spa_t *spa)
 {
 	void *cookie = NULL;
 	spa_log_sm_t *sls;
+	log_summary_entry_t *e;
+
 	while ((sls = avl_destroy_nodes(&spa->spa_sm_logs_by_txg,
 	    &cookie)) != NULL) {
 		VERIFY0(sls->sls_mscount);
 		kmem_free(sls, sizeof (spa_log_sm_t));
 	}
 
-	for (log_summary_entry_t *e = list_head(&spa->spa_log_summary);
-	    e != NULL; e = list_head(&spa->spa_log_summary)) {
+	while ((e = list_remove_head(&spa->spa_log_summary)) != NULL) {
 		VERIFY0(e->lse_mscount);
-		list_remove(&spa->spa_log_summary, e);
 		kmem_free(e, sizeof (log_summary_entry_t));
 	}
 

module/zfs/spa_misc.c

@@ -814,8 +814,7 @@ spa_remove(spa_t *spa)
 	if (spa->spa_root)
 		spa_strfree(spa->spa_root);
 
-	while ((dp = list_head(&spa->spa_config_list)) != NULL) {
-		list_remove(&spa->spa_config_list, dp);
+	while ((dp = list_remove_head(&spa->spa_config_list)) != NULL) {
 		if (dp->scd_path != NULL)
 			spa_strfree(dp->scd_path);
 		kmem_free(dp, sizeof (spa_config_dirent_t));

module/zfs/vdev_indirect.c

@@ -293,17 +293,16 @@ vdev_indirect_map_free(zio_t *zio)
 	indirect_vsd_t *iv = zio->io_vsd;
 
 	indirect_split_t *is;
-	while ((is = list_head(&iv->iv_splits)) != NULL) {
+	while ((is = list_remove_head(&iv->iv_splits)) != NULL) {
 		for (int c = 0; c < is->is_children; c++) {
 			indirect_child_t *ic = &is->is_child[c];
 			if (ic->ic_data != NULL)
 				abd_free(ic->ic_data);
 		}
-		list_remove(&iv->iv_splits, is);
 
 		indirect_child_t *ic;
-		while ((ic = list_head(&is->is_unique_child)) != NULL)
-			list_remove(&is->is_unique_child, ic);
+		while ((ic = list_remove_head(&is->is_unique_child)) != NULL)
+			;
 
 		list_destroy(&is->is_unique_child);
 
@@ -1659,8 +1658,8 @@ out:
 	for (indirect_split_t *is = list_head(&iv->iv_splits);
 	    is != NULL; is = list_next(&iv->iv_splits, is)) {
 		indirect_child_t *ic;
-		while ((ic = list_head(&is->is_unique_child)) != NULL)
-			list_remove(&is->is_unique_child, ic);
+		while ((ic = list_remove_head(&is->is_unique_child)) != NULL)
+			;
 
 		is->is_unique_children = 0;
 	}

module/zfs/zfs_fm.c

@@ -1522,9 +1522,8 @@ zfs_ereport_fini(void)
 {
 	recent_events_node_t *entry;
 
-	while ((entry = list_head(&recent_events_list)) != NULL) {
+	while ((entry = list_remove_head(&recent_events_list)) != NULL) {
 		avl_remove(&recent_events_tree, entry);
-		list_remove(&recent_events_list, entry);
 		kmem_free(entry, sizeof (*entry));
 	}
 	avl_destroy(&recent_events_tree);

module/zfs/zfs_fuid.c

@@ -699,19 +699,15 @@ zfs_fuid_info_free(zfs_fuid_info_t *fuidp)
 	zfs_fuid_t *zfuid;
 	zfs_fuid_domain_t *zdomain;
 
-	while ((zfuid = list_head(&fuidp->z_fuids)) != NULL) {
-		list_remove(&fuidp->z_fuids, zfuid);
+	while ((zfuid = list_remove_head(&fuidp->z_fuids)) != NULL)
 		kmem_free(zfuid, sizeof (zfs_fuid_t));
-	}
 
 	if (fuidp->z_domain_table != NULL)
 		kmem_free(fuidp->z_domain_table,
 		    (sizeof (char *)) * fuidp->z_domain_cnt);
 
-	while ((zdomain = list_head(&fuidp->z_domains)) != NULL) {
-		list_remove(&fuidp->z_domains, zdomain);
+	while ((zdomain = list_remove_head(&fuidp->z_domains)) != NULL)
 		kmem_free(zdomain, sizeof (zfs_fuid_domain_t));
-	}
 
 	kmem_free(fuidp, sizeof (zfs_fuid_info_t));
 }

module/zfs/zfs_onexit.c

@@ -87,8 +87,7 @@ zfs_onexit_destroy(zfs_onexit_t *zo)
 	zfs_onexit_action_node_t *ap;
 
 	mutex_enter(&zo->zo_lock);
-	while ((ap = list_head(&zo->zo_actions)) != NULL) {
-		list_remove(&zo->zo_actions, ap);
+	while ((ap = list_remove_head(&zo->zo_actions)) != NULL) {
 		mutex_exit(&zo->zo_lock);
 		ap->za_func(ap->za_data);
 		kmem_free(ap, sizeof (zfs_onexit_action_node_t));

module/zfs/zvol.c

@@ -1203,8 +1203,7 @@ zvol_create_minors_recursive(const char *name)
 	 * Prefetch is completed, we can do zvol_os_create_minor
 	 * sequentially.
 	 */
-	while ((job = list_head(&minors_list)) != NULL) {
-		list_remove(&minors_list, job);
+	while ((job = list_remove_head(&minors_list)) != NULL) {
 		if (!job->error)
 			(void) zvol_os_create_minor(job->name);
 		kmem_strfree(job->name);
@@ -1311,10 +1310,8 @@ zvol_remove_minors_impl(const char *name)
 	rw_exit(&zvol_state_lock);
 
 	/* Drop zvol_state_lock before calling zvol_free() */
-	while ((zv = list_head(&free_list)) != NULL) {
-		list_remove(&free_list, zv);
+	while ((zv = list_remove_head(&free_list)) != NULL)
 		zvol_os_free(zv);
-	}
 }
 
 /* Remove minor for this specific volume only */