+ mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/sparsemem: fix 'mem_section' will never be NULL gcc 12 warning
has been added to the -mm tree.  Its filename is
     mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch

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------------------------------------------------------
From: Waiman Long <longman@redhat.com>
Subject: 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.

Link: https://lkml.kernel.org/r/20220201192924.672675-1-longman@redhat.com
Fixes: 83e3c48729d9 ("mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y")
Signed-off-by: Waiman Long <longman@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Justin Forbes <jforbes@redhat.com>
Cc: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mmzone.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/mmzone.h~mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning
+++ a/include/linux/mmzone.h
@@ -1390,7 +1390,7 @@ 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)
 		return NULL;
 #endif
 	if (!mem_section[SECTION_NR_TO_ROOT(nr)])
_

Patches currently in -mm which might be from longman@redhat.com are

mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning.patch
ipc-mqueue-use-get_tree_nodev-in-mqueue_get_tree.patch