The patch titled
Subject: mm/sparsemem: fix 'mem_section' will never be NULL gcc 12 warning
has been removed from the -mm tree. Its filename was
mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch
This patch was dropped because it had testing failures
------------------------------------------------------
From: Waiman Long <longman@xxxxxxxxxx>
Subject: mm/sparsemem: fix 'mem_section' will never be NULL gcc 12 warning
The gcc 12 compiler reports a "'mem_section' will never be NULL" 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
if (!mem_section[SECTION_NR_TO_ROOT(nr)])
return NULL;
:
It happens with both CONFIG_SPARSEMEM_EXTREME on and off. The mem_section
definition is
#ifdef CONFIG_SPARSEMEM_EXTREME
extern struct mem_section **mem_section;
#else
extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
#endif
In the CONFIG_SPARSEMEM_EXTREME case, mem_section obviously cannot be
NULL, but *mem_section can be if memory hasn't been allocated for the
dynamic mem_section[] array yet. In the !CONFIG_SPARSEMEM_EXTREME case,
mem_section is a static 2-dimensional array and so the check
"!mem_section[SECTION_NR_TO_ROOT(nr)]" doesn't make sense.
Fix this warning by checking for "!*mem_section" instead of "!mem_section"
and moving the "!mem_section[SECTION_NR_TO_ROOT(nr)]" check up inside the
CONFIG_SPARSEMEM_EXTREME block.
[longman@xxxxxxxxxx: v2]
Link: https://lkml.kernel.org/r/20220202003550.698768-1-longman@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20220201192924.672675-1-longman@xxxxxxxxxx
Fixes: 83e3c48729d9 ("mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y")
Fixes: 3e347261a80b ("sparsemem extreme implementation")
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Reported-by: Justin Forbes <jforbes@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Justin Forbes <jforbes@xxxxxxxxxx>
Cc: Rafael Aquini <aquini@xxxxxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Hector Martin <marcan@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
--- a/include/linux/mmzone.h~mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning
+++ a/include/linux/mmzone.h
@@ -1390,11 +1390,9 @@ static inline unsigned long *section_to_
static inline struct mem_section *__nr_to_section(unsigned long nr)
{
#ifdef CONFIG_SPARSEMEM_EXTREME
- if (!mem_section)
+ if (!*mem_section || !mem_section[SECTION_NR_TO_ROOT(nr)])
return NULL;
#endif
- if (!mem_section[SECTION_NR_TO_ROOT(nr)])
- return NULL;
return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
}
extern size_t mem_section_usage_size(void);
_
Patches currently in -mm which might be from longman@xxxxxxxxxx are
lib-vsprintf-avoid-redundant-work-with-0-size.patch
mm-page_owner-use-scnprintf-to-avoid-excessive-buffer-overrun-check.patch
mm-page_owner-print-memcg-information.patch
mm-page_owner-record-task-command-name.patch
ipc-mqueue-use-get_tree_nodev-in-mqueue_get_tree.patch
