mm/page_owner: constify dump_page_owner

dump_page_owner() only uses struct page to find the page_ext, and
lookup_page_ext() already takes a const argument.

Link: https://lkml.kernel.org/r/20210416231531.2521383-4-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/page_owner.h

@@ -14,7 +14,7 @@ extern void __set_page_owner(struct page *page,
 extern void __split_page_owner(struct page *page, unsigned int nr);
 extern void __copy_page_owner(struct page *oldpage, struct page *newpage);
 extern void __set_page_owner_migrate_reason(struct page *page, int reason);
-extern void __dump_page_owner(struct page *page);
+extern void __dump_page_owner(const struct page *page);
 extern void pagetypeinfo_showmixedcount_print(struct seq_file *m,
 					pg_data_t *pgdat, struct zone *zone);
 
@@ -46,7 +46,7 @@ static inline void set_page_owner_migrate_reason(struct page *page, int reason)
 	if (static_branch_unlikely(&page_owner_inited))
 		__set_page_owner_migrate_reason(page, reason);
 }
-static inline void dump_page_owner(struct page *page)
+static inline void dump_page_owner(const struct page *page)
 {
 	if (static_branch_unlikely(&page_owner_inited))
 		__dump_page_owner(page);
@@ -69,7 +69,7 @@ static inline void copy_page_owner(struct page *oldpage, struct page *newpage)
 static inline void set_page_owner_migrate_reason(struct page *page, int reason)
 {
 }
-static inline void dump_page_owner(struct page *page)
+static inline void dump_page_owner(const struct page *page)
 {
 }
 #endif /* CONFIG_PAGE_OWNER */

mm/page_owner.c

@@ -392,7 +392,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
 	return -ENOMEM;
 }
 
-void __dump_page_owner(struct page *page)
+void __dump_page_owner(const struct page *page)
 {
 	struct page_ext *page_ext = lookup_page_ext(page);
 	struct page_owner *page_owner;