On Mon, Oct 29, 2018 at 10:16:43AM +0800, miles.chen@xxxxxxxxxxxx wrote:
> The kbuf used by page owner is allocated by kmalloc(), which means it
> can use only normal memory and there might be a "out of memory"
> issue when we're out of normal memory.
>
> Use kvmalloc() so we can also allocate kbuf from
> normal/hihghmem on 32bit kernel.
That's a misconception:
ret = kmalloc_node(size, kmalloc_flags, node);
/*
* It doesn't really make sense to fallback to vmalloc for sub page
* requests
*/
if (ret || size <= PAGE_SIZE)
return ret;
Now, maybe this is an opportunity for us to improve kvmalloc. Maybe like
this ...
diff --git a/mm/util.c b/mm/util.c
index 8bf08b5b5760..fdf5b34d2c28 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -416,10 +416,10 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
ret = kmalloc_node(size, kmalloc_flags, node);
/*
- * It doesn't really make sense to fallback to vmalloc for sub page
- * requests
+ * It only makes sense to fallback to vmalloc for sub page
+ * requests if we might be able to allocate highmem pages.
*/
- if (ret || size <= PAGE_SIZE)
+ if (ret || (!IS_ENABLED(CONFIG_HIGHMEM) && size <= PAGE_SIZE))
return ret;
return __vmalloc_node_flags_caller(size, node, flags,
