+ mm-page_alloc-clear-pagebuddy-using-__clearpagebuddy-for-bad-pages.patch added to mm-unstable branch

+ mm-page_alloc-clear-pagebuddy-using-__clearpagebuddy-for-bad-pages.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/page_alloc: clear PageBuddy using __ClearPageBuddy() for bad pages
has been added to the -mm mm-unstable branch.  Its filename is
     mm-page_alloc-clear-pagebuddy-using-__clearpagebuddy-for-bad-pages.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-clear-pagebuddy-using-__clearpagebuddy-for-bad-pages.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: David Hildenbrand <david@redhat.com>
Subject: mm/page_alloc: clear PageBuddy using __ClearPageBuddy() for bad pages
Date: Wed, 29 May 2024 13:19:02 +0200

Let's stop using page_mapcount_reset() and clear PageBuddy using
__ClearPageBuddy() instead.

Link: https://lkml.kernel.org/r/20240529111904.2069608-5-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/page_alloc.c~mm-page_alloc-clear-pagebuddy-using-__clearpagebuddy-for-bad-pages
+++ a/mm/page_alloc.c
@@ -498,7 +498,8 @@ static void bad_page(struct page *page,
 	dump_stack();
 out:
 	/* Leave bad fields for debug, except PageBuddy could make trouble */
-	page_mapcount_reset(page); /* remove PageBuddy */
+	if (PageBuddy(page))
+		__ClearPageBuddy(page);
 	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 }
 
@@ -1346,7 +1347,8 @@ static void check_new_page_bad(struct pa
 {
 	if (unlikely(page->flags & __PG_HWPOISON)) {
 		/* Don't complain about hwpoisoned pages */
-		page_mapcount_reset(page); /* remove PageBuddy */
+		if (PageBuddy(page))
+			__ClearPageBuddy(page);
 		return;
 	}
 
_

Patches currently in -mm which might be from david@redhat.com are

mm-memory-move-page_count-check-into-validate_page_before_insert.patch
mm-memory-cleanly-support-zeropage-in-vm_insert_page-vm_map_pages-and-vmf_insert_mixed.patch
mm-rmap-sanity-check-that-zeropages-are-not-passed-to-rmap.patch
mm-update-_mapcount-and-page_type-documentation.patch
mm-allow-reuse-of-the-lower-16-bit-of-the-page-type-with-an-actual-type.patch
mm-zsmalloc-use-a-proper-page-type.patch
mm-page_alloc-clear-pagebuddy-using-__clearpagebuddy-for-bad-pages.patch
mm-filemap-reinitialize-folio-_mapcount-directly.patch
mm-mm_init-initialize-page-_mapcount-directly-in-__init_single_page.patch