On (10/05/15 16:23), Hui Zhu wrote:
> In function obj_malloc:
> if (!class->huge)
> /* record handle in the header of allocated chunk */
> link->handle = handle;
> else
> /* record handle in first_page->private */
> set_page_private(first_page, handle);
> The huge's page save handle to private directly.
>
> But in obj_to_head:
> if (class->huge) {
> VM_BUG_ON(!is_first_page(page));
> return page_private(page);
> } else
> return *(unsigned long *)obj;
> It is used as a pointer.
>
um...
obj_to_head() is not for obj_malloc(), but for record_obj() that follows.
handle is a `void *' returned from alloc_handle()->kmem_cache_alloc(), and
casted to 'unsigned long'.
we store obj as:
static void record_obj(unsigned long handle, unsigned long obj)
{
*(unsigned long *)handle = obj;
}
regardless `class->huge'.
and retrieve it as `*(unsigned long *)foo', which is either
`*(unsigned long *)page_private(page)'
or
`*(unsigned long *)obj'
'return p' and `return *p' do slightly different things for pointers.
am I missing something?
-ss
> So change obj_to_head use page_private(page) as value but not pointer
> in obj_to_head.
>
> Signed-off-by: Hui Zhu <zhuhui@xxxxxxxxxx>
> ---
> mm/zsmalloc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index f135b1b..e881d4f 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -824,7 +824,7 @@ static unsigned long obj_to_head(struct size_class *class, struct page *page,
> {
> if (class->huge) {
> VM_BUG_ON(!is_first_page(page));
> - return *(unsigned long *)page_private(page);
> + return page_private(page);
> } else
> return *(unsigned long *)obj;
> }
> --
> 1.9.1
>
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