From: Waiman Long <longman@xxxxxxxxxx>
mm/sparsemem: Fix 'mem_section' will never be NULL gcc 12 warning
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.
Fixes: 83e3c48729d9 ("mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y")
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index blahblah..blahblah 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)])
--
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1598
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