Commit 3e6f6f67 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Jinjiang Tu
Browse files

mm: improve dumping of mapcount and page_type 

mainline inclusion
from mainline-v6.10-rc1
commit 8f790d0c7cfed047a1f7aad3fcddd7a979bf7232
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IACHGW

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8f790d0c7cfed047a1f7aad3fcddd7a979bf7232

-------------------------------------------

For pages that have a page_type, set the mapcount to 0, which will reduce
the confusion in people reading page dumps ("Why does this page have a
mapcount of -128?").  Now that hugetlbfs is a page_type, read the
entire_mapcount for any large folio; this is fine for all folios as no
user reuses the entire_mapcount field.

For pages which do not have a page type, do not print it to reduce
clutter.

Link: https://lkml.kernel.org/r/20240321142448.1645400-9-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarJinjiang Tu <tujinjiang@huawei.com>
parent 27189c75

mm/debug.c

+8 −11
Original line number Diff line number Diff line
@@ -55,18 +55,14 @@ static void __dump_folio(struct folio *folio, struct page *page, 
		unsigned long pfn, unsigned long idx)

{

	struct address_space *mapping = folio_mapping(folio);

	int mapcount = 0;

	int mapcount = atomic_read(&page->_mapcount) + 1;

	char *type = "";



	/*

	 * page->_mapcount space in struct page is used by slab pages to

	 * encode own info, and we must avoid calling page_folio() again.

	 */

	if (!folio_test_slab(folio)) {

		mapcount = atomic_read(&page->_mapcount) + 1;

	/* Open-code page_mapcount() to avoid looking up a stale folio */

	if (mapcount < 0)

		mapcount = 0;

	if (folio_test_large(folio))

		mapcount += folio_entire_mapcount(folio);

	}



	pr_warn("page: refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n",

			folio_ref_count(folio), mapcount, mapping,
@@ -99,6 +95,7 @@ static void __dump_folio(struct folio *folio, struct page *page, 
	 */

	pr_warn("%sflags: %pGp%s\n", type, &folio->flags,

		is_migrate_cma_folio(folio, pfn) ? " CMA" : "");

	if (page_has_type(&folio->page))

		pr_warn("page_type: %pGt\n", &folio->page.page_type);



	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,