+ mmpage_owner-fix-printing-of-stack-records.patch added to mm-hotfixes-unstable branch

+ mmpage_owner-fix-printing-of-stack-records.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm,page_owner: fix printing of stack records
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mmpage_owner-fix-printing-of-stack-records.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mmpage_owner-fix-printing-of-stack-records.patch

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

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------------------------------------------------------
From: Oscar Salvador <osalvador@suse.de>
Subject: mm,page_owner: fix printing of stack records
Date: Thu, 4 Apr 2024 09:07:02 +0200

When seq_* code sees that its buffer overflowed, it re-allocates a bigger
onecand calls seq_operations->start() callback again.  stack_start()
naively though that if it got called again, it meant that the old record
got already printed so it returned the next object, but that is not true.

The consequence of that is that every time stack_stop() -> stack_start()
get called because we needed a bigger buffer, stack_start() will skip
entries, and those will not be printed.

Fix it by not advancing to the next object in stack_start().

Link: https://lkml.kernel.org/r/20240404070702.2744-5-osalvador@suse.de
Fixes: 765973a09803 ("mm,page_owner: display all stacks and their count")
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_owner.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/mm/page_owner.c~mmpage_owner-fix-printing-of-stack-records
+++ a/mm/page_owner.c
@@ -872,13 +872,11 @@ static void *stack_start(struct seq_file
 		 * value of stack_list.
 		 */
 		stack = smp_load_acquire(&stack_list);
+		m->private = stack;
 	} else {
 		stack = m->private;
-		stack = stack->next;
 	}
 
-	m->private = stack;
-
 	return stack;
 }
 
_

Patches currently in -mm which might be from osalvador@suse.de are

mmpage_owner-update-metadata-for-tail-pages.patch
mmpage_owner-fix-refcount-imbalance.patch
mmpage_owner-fix-accounting-of-pages-when-migrating.patch
mmpage_owner-fix-printing-of-stack-records.patch