Re: [PATCH v4 0/7] mm/page_owner: misc cleanups

[Andrew Morton]

On Wed,  1 Jul 2026 09:22:26 +0800 Ye Liu <ye.liu@xxxxxxxxx> wrote:

> v4:
>  - Patch 2: also update scripts/gdb/linux/page_owner.py to use MR_NEVER
>    instead of the hardcoded -1.
>  - https://lore.kernel.org/all/20260630015331.147174-1-ye.liu@xxxxxxxxx/

I'm seeing more changes than described here?


Thanks, I updated mm.git to this version.

Here's how v4 altered mm.git:


 mm/page_owner.c                 |   16 +++-------------
 scripts/gdb/linux/page_owner.py |    4 +++-
 2 files changed, 6 insertions(+), 14 deletions(-)

--- a/mm/page_owner.c~b
+++ a/mm/page_owner.c
@@ -428,12 +428,6 @@ void __folio_copy_owner(struct folio *ne
  * to skip less than the full buddy block, but that is acceptable for page owner
  * iteration purposes.
  *
- * The lockless read of buddy_order_unsafe() can also return a garbage order if
- * the page is concurrently allocated and PageBuddy is cleared between the check
- * and the read. Clamp the advance at the next MAX_ORDER_NR_PAGES boundary so
- * that a bogus order cannot carry @pfn into an unvalidated memory section,
- * which would break callers that rely on boundary-aligned pfn_valid() checks.
- *
  * Return: true if the page was skipped (caller should continue its loop),
  *         false if the page is not a buddy page and should be processed normally.
  */
@@ -445,12 +439,8 @@ static inline bool skip_buddy_pages(unsi
 		return false;
 
 	order = buddy_order_unsafe(page);
-	if (order <= MAX_PAGE_ORDER) {
-		unsigned long new_pfn = *pfn + (1UL << order);
-		unsigned long boundary = ALIGN(*pfn + 1, MAX_ORDER_NR_PAGES);
-
-		*pfn = min(new_pfn, boundary) - 1;
-	}
+	if (order <= MAX_PAGE_ORDER)
+		*pfn += (1UL << order) - 1;
 
 	return true;
 }
@@ -561,7 +551,7 @@ static inline int print_page_owner_memcg
 	cgroup_name(memcg->css.cgroup, name, sizeof(name));
 	ret += scnprintf(kbuf + ret, count - ret,
 			"Charged %sto %smemcg %s\n",
-			(memcg_data & MEMCG_DATA_KMEM) ? "(via objcg) " : "",
+			PageMemcgKmem(page) ? "(via objcg) " : "",
 			online ? "" : "offline ",
 			name);
 out_unlock:
--- a/scripts/gdb/linux/page_owner.py~b
+++ a/scripts/gdb/linux/page_owner.py
@@ -34,6 +34,7 @@ class DumpPageOwner(gdb.Command):
     max_pfn = None
     p_ops = None
     migrate_reason_names = None
+    mr_never = None
 
     def __init__(self):
         super(DumpPageOwner, self).__init__("lx-dump-page-owner", gdb.COMMAND_SUPPORT)
@@ -65,6 +66,7 @@ class DumpPageOwner(gdb.Command):
         self.max_pfn = int(gdb.parse_and_eval("max_pfn"))
         self.page_ext_size = int(gdb.parse_and_eval("page_ext_size"))
         self.migrate_reason_names = gdb.parse_and_eval('migrate_reason_names')
+        self.mr_never = int(gdb.parse_and_eval('MR_NEVER'))
 
     def page_ext_invalid(self, page_ext):
         if page_ext == gdb.Value(0):
@@ -138,7 +140,7 @@ class DumpPageOwner(gdb.Command):
         else:
             gdb.write('page last free stack trace:\n')
             stackdepot.stack_depot_print(page_owner["free_handle"])
-        if page_owner['last_migrate_reason'] != -1:
+        if page_owner['last_migrate_reason'] != self.mr_never:
             gdb.write('page has been migrated, last migrate reason: %s\n' % self.migrate_reason_names[page_owner['last_migrate_reason']])
 
     def read_page_owner(self):
_