mm/page_alloc: restrict and formalize compound_page_dtors[]

Restrict elements in compound_page_dtors[] array per NR_COMPOUND_DTORS and explicitly position them according to enum compound_dtor_id. This improves protection against possible misalignment between compound_page_dtors[] and enum compound_dtor_id later on. Signed-off-by: Anshuman Khandual <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Reviewed-by: David Hildenbrand <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Linus Torvalds <[email protected]>
sm00th · Jun 4, 2020 · ae70edd · ae70edd
1 parent aa09259
commit ae70edd
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Showing 2 changed files with 6 additions and 6 deletions.
diff --git a/include/linux/mm.h b/include/linux/mm.h
@@ -867,7 +867,7 @@ enum compound_dtor_id {
 #endif
 	NR_COMPOUND_DTORS,
 };
-extern compound_page_dtor * const compound_page_dtors[];
+extern compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS];
 
 static inline void set_compound_page_dtor(struct page *page,
 		enum compound_dtor_id compound_dtor)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
@@ -302,14 +302,14 @@ const char * const migratetype_names[MIGRATE_TYPES] = {
 #endif
 };
 
-compound_page_dtor * const compound_page_dtors[] = {
-	NULL,
-	free_compound_page,
+compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS] = {
+	[NULL_COMPOUND_DTOR] = NULL,
+	[COMPOUND_PAGE_DTOR] = free_compound_page,
 #ifdef CONFIG_HUGETLB_PAGE
-	free_huge_page,
+	[HUGETLB_PAGE_DTOR] = free_huge_page,
 #endif
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	free_transhuge_page,
+	[TRANSHUGE_PAGE_DTOR] = free_transhuge_page,
 #endif
 };