Re: [linux-next:master] [mm] 0fa2857d23: WARNING:at_mm/page_alloc.c:#__alloc_pages_noprof

[Yosry Ahmed <yosryahmed@google.com>]

On Mon, Jun 24, 2024 at 10:26 AM Usama Arif <usamaarif642@gmail.com> wrote:
>
>
> On 24/06/2024 19:56, Yosry Ahmed wrote:
> > [..]
> >>>> -       p->zeromap = bitmap_zalloc(maxpages, GFP_KERNEL);
> >>>> +       p->zeromap = kvzalloc(DIV_ROUND_UP(maxpages, 8), GFP_KERNEL);
> >>> No, 8 is not right for 32-bit kernels. I think you want
> >>>        p->zeromap = kvzalloc(BITS_TO_LONGS(maxpages), GFP_KERNEL);
> >>> but please check it carefully, I'm easily confused by such conversions.
> >>>
> >>> Hugh
> >> Ah yes, didnt take into account 32-bit kernel. I think its supposed to be
> >>
> >>    p->zeromap = kvzalloc(BITS_TO_LONGS(maxpages) * sizeof(unsigned long),
> >> GFP_KERNEL);
> > You can do something similar to bitmap_zalloc() and use:
> >
> > kvmalloc_array(BITS_TO_LONGS(nbits), sizeof(unsigned long), GFP_KERNEL
> > | __GFP_ZERO)
> >
> > I don't see a kvzalloc_array() variant to use directly, but it should
> > be trivial to add it. I can see other users of kvmalloc_array() that
> > pass in __GFP_ZERO (e.g. fs/ntfs3/bitmap.c).
> >
> > , or you could take it a step further and add bitmap_kvzalloc(),
> > assuming the maintainers are open to that.
>
> Thanks! bitmap_kvzalloc makes most sense to me. It doesnt make sense
> that bitmap should only be limited to MAX_PAGE_ORDER size. I can add
> this patch below at the start of the series and use it in the patch for
> zeropage swap optimization.
>
>
>      bitmap: add support for virtually contiguous bitmap
>
>      The current bitmap_zalloc API limits the allocation to MAX_PAGE_ORDER,
>      which prevents larger order bitmap allocations. Introduce
>      bitmap_kvzalloc that will allow larger allocations of bitmap.
>      kvmalloc_array still attempts to allocate physically contiguous memory,
>      but upon failure, falls back to non-contiguous (vmalloc) allocation.
>
>      Suggested-by: Yosry Ahmed <yosryahmed@google.com>
>      Signed-off-by: Usama Arif <usamaarif642@gmail.com>
>

LGTM with a small fix below.

> diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> index 8c4768c44a01..881c2ff2e834 100644
> --- a/include/linux/bitmap.h
> +++ b/include/linux/bitmap.h
> @@ -131,9 +131,11 @@ struct device;
>    */
>   unsigned long *bitmap_alloc(unsigned int nbits, gfp_t flags);
>   unsigned long *bitmap_zalloc(unsigned int nbits, gfp_t flags);
> +unsigned long *bitmap_kvzalloc(unsigned int nbits, gfp_t flags);
>   unsigned long *bitmap_alloc_node(unsigned int nbits, gfp_t flags, int
> node);
>   unsigned long *bitmap_zalloc_node(unsigned int nbits, gfp_t flags, int
> node);
>   void bitmap_free(const unsigned long *bitmap);
> +void bitmap_kvfree(const unsigned long *bitmap);
>
>   DEFINE_FREE(bitmap, unsigned long *, if (_T) bitmap_free(_T))
>
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index b97692854966..eabbfb85fb45 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -727,6 +727,13 @@ unsigned long *bitmap_zalloc(unsigned int nbits,
> gfp_t flags)
>   }
>   EXPORT_SYMBOL(bitmap_zalloc);
>
> +unsigned long *bitmap_kvzalloc(unsigned int nbits, gfp_t flags)
> +{
> +       return kvmalloc_array(BITS_TO_LONGS(nbits), sizeof(unsigned long),
> +                             flags | __GFP_ZERO);
> +}
> +EXPORT_SYMBOL(bitmap_zalloc);

EXPORT_SYMBOL(bitmap_kvzalloc)*