vm: Retire kmem_arena

It has simply been an alias for the kernel_arena for many years now.
Enough time has passed to retire it.  Any out-of-tree kernel modules
that directly use kmem_arena should switch to kernel_arena.

Reviewed by:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D46057

sys/arm/nvidia/drm2/tegra_bo.c

@@ -71,7 +71,7 @@ tegra_bo_destruct(struct tegra_bo *bo)
 
 	vm_object_deallocate(bo->cdev_pager);
 	if (bo->vbase != 0)
-		vmem_free(kmem_arena, bo->vbase, size);
+		vmem_free(kernel_arena, bo->vbase, size);
 }
 
 static void
@@ -137,7 +137,7 @@ tegra_bo_init_pager(struct tegra_bo *bo)
 	size = round_page(bo->gem_obj.size);
 
 	bo->pbase = VM_PAGE_TO_PHYS(bo->m[0]);
-	if (vmem_alloc(kmem_arena, size, M_WAITOK | M_BESTFIT, &bo->vbase))
+	if (vmem_alloc(kernel_arena, size, M_WAITOK | M_BESTFIT, &bo->vbase))
 		return (ENOMEM);
 
 	VM_OBJECT_WLOCK(bo->cdev_pager);

sys/kern/subr_vmem.c

@@ -236,9 +236,7 @@ static uma_zone_t vmem_bt_zone;
 static struct vmem kernel_arena_storage;
 static struct vmem buffer_arena_storage;
 static struct vmem transient_arena_storage;
-/* kernel and kmem arenas are aliased for backwards KPI compat. */
 vmem_t *kernel_arena = &kernel_arena_storage;
-vmem_t *kmem_arena = &kernel_arena_storage;
 vmem_t *buffer_arena = &buffer_arena_storage;
 vmem_t *transient_arena = &transient_arena_storage;
 

sys/vm/vm_kern.h

@@ -69,7 +69,6 @@ extern struct vm_map exec_map_store;
 extern struct vm_map pipe_map_store;
 #define	pipe_map	(&pipe_map_store)
 extern struct vmem *kernel_arena;
-extern struct vmem *kmem_arena;
 extern struct vmem *buffer_arena;
 extern struct vmem *transient_arena;
 extern struct vmem *memguard_arena;