Re: [PATCH] mm/vmalloc: do not output a spurious warning when huge vmalloc() fails

Michal Hocko
2023-06-06T16:11:13Z

On Mon 05-06-23 21:11:07, Lorenzo Stoakes wrote:
> In __vmalloc_area_node() we always warn_alloc() when an allocation
> performed by vm_area_alloc_pages() fails unless it was due to a pending
> fatal signal.
>
> However, huge page allocations instigated either by vmalloc_huge() or
> __vmalloc_node_range() (or a caller that invokes this like kvmalloc() or
> kvmalloc_node()) always falls back to order-0 allocations if the huge page
> allocation fails.
>
> This renders the warning useless and noisy, especially as all callers
> appear to be aware that this may fallback. This has already resulted in at
> least one bug report from a user who was confused by this (see link).
>
> Therefore, simply update the code to only output this warning for order-0
> pages when no fatal signal is pending.

The way how high order allocations are grafted in is just horrendous.
Sigh.

> Link: https://bugzilla.suse.com/show_bug.cgi?id=1211410
> Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>

Acked-by: Michal Hocko <mhocko@suse.com>
Thanks!

> ---
> mm/vmalloc.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ab606a80f475..e563f40ad379 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3149,11 +3149,20 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> * allocation request, free them via vfree() if any.
> */
> if (area->nr_pages != nr_small_pages) {
> - /* vm_area_alloc_pages() can also fail due to a fatal signal */
> - if (!fatal_signal_pending(current))
> + /*
> + * vm_area_alloc_pages() can fail due to insufficient memory but
> + * also:-
> + *
> + * - a pending fatal signal
> + * - insufficient huge page-order pages
> + *
> + * Since we always retry allocations at order-0 in the huge page
> + * case a warning for either is spurious.
> + */
> + if (!fatal_signal_pending(current) && page_order == 0)
> warn_alloc(gfp_mask, NULL,
> - "vmalloc error: size %lu, page order %u, failed to allocate pages",
> - area->nr_pages * PAGE_SIZE, page_order);
> + "vmalloc error: size %lu, failed to allocate pages",
> + area->nr_pages * PAGE_SIZE);
> goto fail;
> }
>
> --
> 2.40.1

--
Michal Hocko
SUSE Labs