mm: make __dump_page static

Patch series "Constify struct page arguments".

While working on various solutions to the 32-bit struct page size
regression, one of the problems I found was the networking stack expects
to be able to pass const struct page pointers around, and the mm doesn't
provide a lot of const-friendly functions to call.  The root tangle of
problems is that a lot of functions call VM_BUG_ON_PAGE(), which calls
dump_page(), which calls a lot of functions which don't take a const
struct page (but could be const).

This patch (of 6):

The only caller of __dump_page() now opencodes dump_page(), so remove it
as an externally visible symbol.

Link: https://lkml.kernel.org/r/20210416231531.2521383-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20210416231531.2521383-2-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/mmdebug.h

@@ -9,8 +9,7 @@ struct page;
 struct vm_area_struct;
 struct mm_struct;
 
-extern void dump_page(struct page *page, const char *reason);
-extern void __dump_page(struct page *page, const char *reason);
+void dump_page(struct page *page, const char *reason);
 void dump_vma(const struct vm_area_struct *vma);
 void dump_mm(const struct mm_struct *mm);
 

mm/debug.c

@@ -42,7 +42,7 @@ const struct trace_print_flags vmaflag_names[] = {
 	{0, NULL}
 };
 
-void __dump_page(struct page *page, const char *reason)
+static void __dump_page(struct page *page, const char *reason)
 {
 	struct page *head = compound_head(page);
 	struct address_space *mapping;

mm/page_alloc.c

@@ -658,8 +658,7 @@ static void bad_page(struct page *page, const char *reason)
 
 	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
 		current->comm, page_to_pfn(page));
-	__dump_page(page, reason);
-	dump_page_owner(page);
+	dump_page(page, reason);
 
 	print_modules();
 	dump_stack();