lkml.org 
[lkml]   [2016]   [Apr]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] mm: use unsigned long constant for page flags
On Fri, 29 Apr 2016 16:15:23 -0700 Yu Zhao <yuzhao@google.com> wrote:

> struct page->flags is unsigned long, so when shifting bits we should
> use UL suffix to match it.
>
> Found this problem after I added 64-bit CPU specific page flags and
> failed to compile the kernel:
> mm/page_alloc.c: In function '__free_one_page':
> mm/page_alloc.c:672:2: error: integer overflow in expression [-Werror=overflow]
>

Fair enough.

> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -474,7 +474,7 @@ static inline void ClearPageCompound(struct page *page)
> }
> #endif
>
> -#define PG_head_mask ((1L << PG_head))
> +#define PG_head_mask ((1UL << PG_head))

We do have the BIT() macro. I don't think it would add a lot of value
here; I'd be OK with it either way.

\
 
 \ /
  Last update: 2016-04-30 01:41    [W:0.029 / U:2.404 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site