Re: [Resend PATCH] mm: use stack_depot for recording kmemleak's backtrace

[Zhaoyang Huang]

We can account and sort the output via backtrace under this change

On Tue, Oct 11, 2022 at 9:18 AM zhaoyang.huang
<zhaoyang.huang@xxxxxxxxxx> wrote:
>
> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>
> Using stack_depot to record kmemleak's backtrace which has been implemented
> on slub for reducing redundant information.
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> ---
>  mm/kmemleak.c | 43 +++++++++++++++++++++++++++++++++----------
>  1 file changed, 33 insertions(+), 10 deletions(-)
>
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index 1eddc01..c9cee3a 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -79,6 +79,7 @@
>  #include <linux/mutex.h>
>  #include <linux/rcupdate.h>
>  #include <linux/stacktrace.h>
> +#include <linux/stackdepot.h>
>  #include <linux/cache.h>
>  #include <linux/percpu.h>
>  #include <linux/memblock.h>
> @@ -159,8 +160,7 @@ struct kmemleak_object {
>         u32 checksum;
>         /* memory ranges to be scanned inside an object (empty for all) */
>         struct hlist_head area_list;
> -       unsigned long trace[MAX_TRACE];
> -       unsigned int trace_len;
> +       depot_stack_handle_t trace_handle;
>         unsigned long jiffies;          /* creation timestamp */
>         pid_t pid;                      /* pid of the current task */
>         char comm[TASK_COMM_LEN];       /* executable name */
> @@ -346,8 +346,11 @@ static void print_unreferenced(struct seq_file *seq,
>                                struct kmemleak_object *object)
>  {
>         int i;
> +       unsigned long *entries;
> +       unsigned int nr_entries;
>         unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
>
> +       nr_entries = stack_depot_fetch(object->trace_handle, &entries);
>         warn_or_seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
>                    object->pointer, object->size);
>         warn_or_seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
> @@ -356,10 +359,10 @@ static void print_unreferenced(struct seq_file *seq,
>         hex_dump_object(seq, object);
>         warn_or_seq_printf(seq, "  backtrace:\n");
>
> -       for (i = 0; i < object->trace_len; i++) {
> -               void *ptr = (void *)object->trace[i];
> -               warn_or_seq_printf(seq, "    [<%p>] %pS\n", ptr, ptr);
> -       }
> +       for (i = 0; i < nr_entries; i++) {
> +               void *ptr = (void *)entries[i];
> +               warn_or_seq_printf(seq, "    [<%p>] %pS\n", ptr, ptr);
> +       }
>  }
>
>  /*
> @@ -378,7 +381,8 @@ static void dump_object_info(struct kmemleak_object *object)
>         pr_notice("  flags = 0x%x\n", object->flags);
>         pr_notice("  checksum = %u\n", object->checksum);
>         pr_notice("  backtrace:\n");
> -       stack_trace_print(object->trace, object->trace_len, 4);
> +       if(object->trace_handle)
> +               stack_depot_print(object->trace_handle);
>  }
>
>  /*
> @@ -591,6 +595,25 @@ static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int ali
>         return object;
>  }
>
> +#ifdef CONFIG_STACKDEPOT
> +static noinline depot_stack_handle_t set_track_prepare(void)
> +{
> +       depot_stack_handle_t trace_handle;
> +       unsigned long entries[MAX_TRACE];
> +       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
> +
>  /*
>   * Save stack trace to the given array of MAX_TRACE size.
>   */
> @@ -654,7 +677,7 @@ static struct kmemleak_object *__create_object(unsigned long ptr, size_t size,
>         }
>
>         /* kernel backtrace */
> -       object->trace_len = __save_stack_trace(object->trace);
> +       object->trace_handle = set_track_prepare();
>
>         raw_spin_lock_irqsave(&kmemleak_lock, flags);
>
> @@ -694,7 +717,6 @@ static struct kmemleak_object *__create_object(unsigned long ptr, size_t size,
>         rb_link_node(&object->rb_node, rb_parent, link);
>         rb_insert_color(&object->rb_node, is_phys ? &object_phys_tree_root :
>                                           &object_tree_root);
> -
>         list_add_tail_rcu(&object->object_list, &object_list);
>  out:
>         raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
> @@ -1094,7 +1116,7 @@ void __ref kmemleak_update_trace(const void *ptr)
>         }
>
>         raw_spin_lock_irqsave(&object->lock, flags);
> -       object->trace_len = __save_stack_trace(object->trace);
> +       object->trace_handle = set_track_prepare();
>         raw_spin_unlock_irqrestore(&object->lock, flags);
>
>         put_object(object);
> @@ -2064,6 +2086,7 @@ void __init kmemleak_init(void)
>         if (kmemleak_error)
>                 return;
>
> +       stack_depot_init();
>         jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
>         jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
>
> --
> 1.9.1
>