target: Use array_zalloc for tpg_lun_list

Turns an order-10 allocation into slab-sized ones, thereby preventing
allocation failures with memory fragmentation.

This likely saves memory as well, as the slab allocator can pack objects
more tightly than the buddy allocator.

Signed-off-by: Joern Engel <[e-mail]>
Signed-off-by: Nicholas Bellinger <[e-mail]>

drivers/target/target_core_device.c

···
 		spin_unlock(&tpg->tpg_lun_lock);
 		return NULL;
 	}
-	lun = &tpg->tpg_lun_list[unpacked_lun];
+	lun = tpg->tpg_lun_list[unpacked_lun];
 
 	if (lun->lun_status != TRANSPORT_LUN_STATUS_FREE) {
 		pr_err("%s Logical Unit Number: %u is not free on"
···
 		spin_unlock(&tpg->tpg_lun_lock);
 		return NULL;
 	}
-	lun = &tpg->tpg_lun_list[unpacked_lun];
+	lun = tpg->tpg_lun_list[unpacked_lun];
 
 	if (lun->lun_status != TRANSPORT_LUN_STATUS_ACTIVE) {
 		pr_err("%s Logical Unit Number: %u is not active on"

drivers/target/target_core_tpg.c

···
 
 	spin_lock(&tpg->tpg_lun_lock);
 	for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
-		lun = &tpg->tpg_lun_list[i];
+		lun = tpg->tpg_lun_list[i];
 		if (lun->lun_status != TRANSPORT_LUN_STATUS_ACTIVE)
 			continue;
 
···
 	}
 
 	return 0;
+}
+
+void array_free(void *array, int n)
+{
+	void **a = array;
+	int i;
+
+	for (i = 0; i < n; i++)
+		kfree(a[i]);
+	kfree(a);
+}
+
+static void *array_zalloc(int n, size_t size, gfp_t flags)
+{
+	void **a;
+	int i;
+
+	a = kzalloc(n * sizeof(void*), flags);
+	if (!a)
+		return NULL;
+	for (i = 0; i < n; i++) {
+		a[i] = kzalloc(size, flags);
+		if (!a[i]) {
+			array_free(a, n);
+			return NULL;
+		}
+	}
+	return a;
 }
 
 /*      core_create_device_list_for_node():
···
 
 	spin_lock(&tpg->tpg_lun_lock);
 	for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
-		lun = &tpg->tpg_lun_list[i];
+		lun = tpg->tpg_lun_list[i];
 
 		if ((lun->lun_status != TRANSPORT_LUN_STATUS_ACTIVE) ||
 		    (lun->lun_se_dev == NULL))
···
 	struct se_lun *lun;
 	u32 i;
 
-	se_tpg->tpg_lun_list = kzalloc((sizeof(struct se_lun) *
-				TRANSPORT_MAX_LUNS_PER_TPG), GFP_KERNEL);
+	se_tpg->tpg_lun_list = array_zalloc(TRANSPORT_MAX_LUNS_PER_TPG,
+			sizeof(struct se_lun), GFP_KERNEL);
 	if (!se_tpg->tpg_lun_list) {
 		pr_err("Unable to allocate struct se_portal_group->"
 				"tpg_lun_list\n");
···
 	}
 
 	for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
-		lun = &se_tpg->tpg_lun_list[i];
+		lun = se_tpg->tpg_lun_list[i];
 		lun->unpacked_lun = i;
 		lun->lun_status = TRANSPORT_LUN_STATUS_FREE;
 		atomic_set(&lun->lun_acl_count, 0);
···
 		core_tpg_release_virtual_lun0(se_tpg);
 
 	se_tpg->se_tpg_fabric_ptr = NULL;
-	kfree(se_tpg->tpg_lun_list);
+	array_free(se_tpg->tpg_lun_list, TRANSPORT_MAX_LUNS_PER_TPG);
 	return 0;
 }
 EXPORT_SYMBOL(core_tpg_deregister);
···
 	}
 
 	spin_lock(&tpg->tpg_lun_lock);
-	lun = &tpg->tpg_lun_list[unpacked_lun];
+	lun = tpg->tpg_lun_list[unpacked_lun];
 	if (lun->lun_status == TRANSPORT_LUN_STATUS_ACTIVE) {
 		pr_err("TPG Logical Unit Number: %u is already active"
 			" on %s Target Portal Group: %u, ignoring request.\n",
···
 	}
 
 	spin_lock(&tpg->tpg_lun_lock);
-	lun = &tpg->tpg_lun_list[unpacked_lun];
+	lun = tpg->tpg_lun_list[unpacked_lun];
 	if (lun->lun_status != TRANSPORT_LUN_STATUS_ACTIVE) {
 		pr_err("%s Logical Unit Number: %u is not active on"
 			" Target Portal Group: %u, ignoring request.\n",

include/target/target_core_backend.h

···
 void	*transport_kmap_data_sg(struct se_cmd *);
 void	transport_kunmap_data_sg(struct se_cmd *);
 
+void	array_free(void *array, int n);
+
 #endif /* TARGET_CORE_BACKEND_H */

include/target/target_core_base.h

···
 	struct list_head	se_tpg_node;
 	/* linked list for initiator ACL list */
 	struct list_head	acl_node_list;
-	struct se_lun		*tpg_lun_list;
+	struct se_lun		**tpg_lun_list;
 	struct se_lun		tpg_virt_lun0;
 	/* List of TCM sessions associated wth this TPG */
 	struct list_head	tpg_sess_list;