On Tue, Feb 01, 2022 at 02:29:24PM -0500, Waiman Long wrote:
> The gcc 12 compiler reports a warning on the following code:
>
> static inline struct mem_section *__nr_to_section(unsigned long nr)
> {
> #ifdef CONFIG_SPARSEMEM_EXTREME
> if (!mem_section)
> return NULL;
> #endif
> :
>
> With CONFIG_SPARSEMEM_EXTREME on, the mem_section definition is
>
> extern struct mem_section **mem_section;
>
> Obviously, mem_section cannot be NULL, but *mem_section can be if memory
> hasn't been allocated for the dynamic mem_section[] array yet. Fix this
> warning by checking for "!*mem_section" instead.
Hmm, if mem_section cannot be NULL, it means if will be never allocated,
no?
static void __init memory_present(int nid, unsigned long start, unsigned long end)
{
unsigned long pfn;
#ifdef CONFIG_SPARSEMEM_EXTREME
if (unlikely(!mem_section)) {
unsigned long size, align;
size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
align = 1 << (INTERNODE_CACHE_SHIFT);
mem_section = memblock_alloc(size, align);
if (!mem_section)
panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
__func__, size, align);
}
#endif
...
>
> Fixes: 83e3c48729d9 ("mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y")
> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> ---
> include/linux/mmzone.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index aed44e9b5d89..bd1b19925f3b 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1390,7 +1390,7 @@ static inline unsigned long *section_to_usemap(struct mem_section *ms)
> static inline struct mem_section *__nr_to_section(unsigned long nr)
> {
> #ifdef CONFIG_SPARSEMEM_EXTREME
> - if (!mem_section)
> + if (!*mem_section)
> return NULL;
> #endif
> if (!mem_section[SECTION_NR_TO_ROOT(nr)])
> --
> 2.27.0
>
>
--
Sincerely yours,
Mike.
