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

[Ye Liu <ye.liu@linux.dev>]

在 2026/7/1 11:41, Andrew Morton 写道:
> On Wed,  1 Jul 2026 09:22:26 +0800 Ye Liu <ye.liu@linux.dev> 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@linux.dev/
> 
> I'm seeing more changes than described here?
> 
> 
> Thanks, I updated mm.git to this version.
> 
> Here's how v4 altered mm.git:
> 
Patch[1] depends on this patch series and should be placed together with this part.
I will send V5 including both patches.                                             
                                                                                   
[1]:https://lore.kernel.org/all/20260625014708.87386-1-ye.liu@linux.dev/           

> 
>  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):
> _
> 

-- 
Thanks,
Ye Liu