On 10/6/22 05:19, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>
> Private is vacant for most of Non-LRU pages while the user has explicitly
> operation on page->private via set_page_private, I would like introduce
> stackdepot information on page->private for a simplified tracking mechanism
> which could be help for kernel driver's memory leak.
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
This duplicates the existing page_owner functionality in a way that
unconditionally adds overhead to all kernels that have CONFIG_STACKDEPOT
enabled build-time (and also misses the need to initialize stackdepot properly).
Also wouldn't be suprised if some existing page->private users were actually
confused by the field suddenly being non-zero without their own action.
> ---
> mm/page_alloc.c | 28 +++++++++++++++++++++++++++-
> 1 file changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e5486d4..b79a503 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -75,6 +75,7 @@
> #include <linux/khugepaged.h>
> #include <linux/buffer_head.h>
> #include <linux/delayacct.h>
> +#include <linux/stackdepot.h>
> #include <asm/sections.h>
> #include <asm/tlbflush.h>
> #include <asm/div64.h>
> @@ -2464,6 +2465,25 @@ static inline bool should_skip_init(gfp_t flags)
> return (flags & __GFP_SKIP_ZERO);
> }
>
> +#ifdef CONFIG_STACKDEPOT
> +static noinline depot_stack_handle_t set_track_prepare(void)
> +{
> + depot_stack_handle_t trace_handle;
> + unsigned long entries[16];
> + unsigned int nr_entries;
> +
> + nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
> + trace_handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
> +
> + return trace_handle;
> +}
> +#else
> +static inline depot_stack_handle_t set_track_prepare(void)
> +{
> + return 0;
> +}
> +#endif
> +
> inline void post_alloc_hook(struct page *page, unsigned int order,
> gfp_t gfp_flags)
> {
> @@ -2471,8 +2491,14 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
> !should_skip_init(gfp_flags);
> bool init_tags = init && (gfp_flags & __GFP_ZEROTAGS);
> int i;
> + depot_stack_handle_t stack_handle = set_track_prepare();
>
> - set_page_private(page, 0);
> + /*
> + * Don't worry, user will cover private directly without checking
> + * this field and has ability to trace the page. This also will not
> + * affect expected state when freeing
> + */
> + set_page_private(page, stack_handle);
> set_page_refcounted(page);
>
> arch_alloc_page(page, order);
