Re: [PATCH v6 1/3] mm/page_owner: add print_mode filter

[Oscar Salvador]

On Mon, May 11, 2026 at 11:30:15AM +0800, Zhen Ni wrote:
> Add a print_mode filter to page_owner that allows users to choose between
> printing full stack traces or only stack handles, significantly reducing
> output size for debugging and analysis.
> 
> The filter provides a string-based interface under
> /sys/kernel/debug/page_owner_filter/:
> - Reading shows the current mode with [] brackets around active option
> - Writing accepts "full_stack" or "stack_handle" strings
> 
> The default full_stack mode maintains backward compatibility with existing
> usage, displaying complete stack traces for each page allocation.
> 
> The stack_handle mode dramatically reduces log size by showing only
> the handle number instead of the full stack trace. The mapping from
> handles to actual stack traces can be obtained via the
> show_stacks_handles interface.
> 
> Example usage:
>   # echo stack_handle > /sys/kernel/debug/page_owner_filter/print_mode
>   # cat /sys/kernel/debug/page_owner_filter/print_mode
>   full_stack [stack_handle]
>   # cat /sys/kernel/debug/page_owner
>   Page allocated via order 0, migratetype Unmovable, gfp_mask 0x1100ca,
>   pid 1, tgid 1 (systemd), ts 123456789 ns
>   PFN 0x1000 type Unmovable Block 1 type Unmovable
>   Flags 0x3fffe800000084(referenced|lru|active|private|node=0|zone=1)
>   handle: 17432583
>   ...
> 
> Reviewed-by: SeongJae Park <sj@xxxxxxxxxx>
> Signed-off-by: Zhen Ni <zhen.ni@xxxxxxxxxxxx>

Overall looks good to me, one comment below

Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>

> ---
...
> ---
>  mm/page_owner.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 80 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 8178e0be557f..27a412c52d41 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -1,5 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0
>  #include <linux/debugfs.h>
> +#include <linux/fs.h>

Why do we need this?


-- 
Oscar Salvador
SUSE Labs