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mm: improve dumping of mapcount and page_type

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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: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2024-03-21 14:24:46 +00:00 committed by Andrew Morton
parent 46df8e73a4
commit 8f790d0c7c
1 changed files with 8 additions and 11 deletions
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19
mm/debug.c
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@ -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;
if (folio_test_large(folio))
mapcount += folio_entire_mapcount(folio);
}
/* 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,
@ -99,7 +95,8 @@ 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" : "");
pr_warn("page_type: %pGt\n", &folio->page.page_type);
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,
sizeof(unsigned long), page,