On Tue, 30 Apr 2024 at 07:46, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
>
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> The stackdepot code is used by KASAN and lockdep for recoding stack
> traces. Both of these track allocation context information, and so
> their internal allocations must obey the caller allocation contexts
> to avoid generating their own false positive warnings that have
> nothing to do with the code they are instrumenting/tracking.
>
> We also don't want recording stack traces to deplete emergency
> memory reserves - debug code is useless if it creates new issues
> that can't be replicated when the debug code is disabled.
>
> Switch the stackdepot allocation masking to use gfp_nested_mask()
> to address these issues. gfp_nested_mask() also strips GFP_ZONEMASK
> naturally, so that greatly simplifies this code.
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
> ---
> lib/stackdepot.c | 11 ++---------
> 1 file changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/lib/stackdepot.c b/lib/stackdepot.c
> index 68c97387aa54..0bbae49e6177 100644
> --- a/lib/stackdepot.c
> +++ b/lib/stackdepot.c
> @@ -624,15 +624,8 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
> * we won't be able to do that under the lock.
> */
> if (unlikely(can_alloc && !READ_ONCE(new_pool))) {
> - /*
> - * Zero out zone modifiers, as we don't have specific zone
> - * requirements. Keep the flags related to allocation in atomic
> - * contexts and I/O.
> - */
> - alloc_flags &= ~GFP_ZONEMASK;
> - alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
> - alloc_flags |= __GFP_NOWARN;
> - page = alloc_pages(alloc_flags, DEPOT_POOL_ORDER);
> + page = alloc_pages(gfp_nested_mask(alloc_flags),
> + DEPOT_POOL_ORDER);
> if (page)
> prealloc = page_address(page);
> }
> --
> 2.43.0
>
