linux-kernel - [PATCH v2 3/5] mm/page_owner: add debugfs file 'show

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Message-ID: <20251001175611.575861-4-mfo@igalia.com>
Date: Wed,  1 Oct 2025 14:56:09 -0300
From: Mauricio Faria de Oliveira <mfo@...lia.com>
To: Michal Hocko <mhocko@...e.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc: Oscar Salvador <osalvador@...e.de>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Brendan Jackman <jackmanb@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Zi Yan <ziy@...dia.com>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	kernel-dev@...lia.com
Subject: [PATCH v2 3/5] mm/page_owner: add debugfs file 'show_handles'

Add the flag STACK_PRINT_FLAG_HANDLE to print a stack's handle number
from stackdepot, and add the file 'show_handles' to show just handles
and their number of pages.

This is similar to 'show_stacks', with handles instead of stack traces.

Signed-off-by: Mauricio Faria de Oliveira <mfo@...lia.com>
---
 mm/page_owner.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index e983ac21a4db..5d488fce0e3d 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -47,6 +47,7 @@ static DEFINE_SPINLOCK(stack_list_lock);
 
 #define STACK_PRINT_FLAG_STACK		0x1
 #define STACK_PRINT_FLAG_PAGES		0x2
+#define STACK_PRINT_FLAG_HANDLE		0x4
 
 struct stack_print_ctx {
 	struct stack *stack;
@@ -921,6 +922,8 @@ static int stack_print(struct seq_file *m, void *v)
 		for (i = 0; i < nr_entries; i++)
 			seq_printf(m, " %pS\n", (void *)entries[i]);
 	}
+	if (ctx->flags & STACK_PRINT_FLAG_HANDLE)
+		seq_printf(m, "handle: %d\n", stack_record->handle.handle);
 	if (ctx->flags & STACK_PRINT_FLAG_PAGES)
 		seq_printf(m, "nr_base_pages: %d\n\n", nr_base_pages);
 
@@ -992,6 +995,10 @@ static int __init pageowner_init(void)
 			    (void *)(STACK_PRINT_FLAG_STACK |
 				     STACK_PRINT_FLAG_PAGES),
 			    &page_owner_stack_operations);
+	debugfs_create_file("show_handles", 0400, dir,
+			    (void *)(STACK_PRINT_FLAG_HANDLE |
+				     STACK_PRINT_FLAG_PAGES),
+			    &page_owner_stack_operations);
 	debugfs_create_file("count_threshold", 0600, dir, NULL,
 			    &proc_page_owner_threshold);
 
-- 
2.48.1