Re: [PATCH -next 2/2] PM: hibernate: add check of preallocate mem for image size pages

[Rafael J. Wysocki]

On Tue, Nov 1, 2022 at 3:28 AM TGSP <tgsp002@xxxxxxxxx> wrote:
>
> From: xiongxin <xiongxin@xxxxxxxxxx>
>
> Added a check on the return value of preallocate_image_highmem(). If
> memory preallocate is insufficient, S4 cannot be done;
>
> I am playing 4K video on a machine with AMD or other graphics card and
> only 8GiB memory, and the kernel is not configured with CONFIG_HIGHMEM.
> When doing the S4 test, the analysis found that when the pages get from
> minimum_image_size() is large enough, The preallocate_image_memory() and
> preallocate_image_highmem() calls failed to obtain enough memory. Add
> the judgment that memory preallocate is insufficient;
>
> "pages -= free_unnecessary_pages()" below will let pages to drop a lot,
> so I wonder if it makes sense to add a judgment here.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: xiongxin <xiongxin@xxxxxxxxxx>
> Signed-off-by: huanglei <huanglei@xxxxxxxxxx>
> ---
>  kernel/power/snapshot.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
> index c20ca5fb9adc..670abf89cf31 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -1738,6 +1738,7 @@ int hibernate_preallocate_memory(void)
>         struct zone *zone;
>         unsigned long saveable, size, max_size, count, highmem, pages = 0;
>         unsigned long alloc, save_highmem, pages_highmem, avail_normal;
> +       unsigned long size_highmem;

Please define this in the block where it will be used.

>         ktime_t start, stop;
>         int error;
>
> @@ -1863,7 +1864,13 @@ int hibernate_preallocate_memory(void)
>                 pages_highmem += size;

The line above can be dropped.

>                 alloc -= size;
>                 size = preallocate_image_memory(alloc, avail_normal);
> -               pages_highmem += preallocate_image_highmem(alloc - size);
> +               size_highmem += preallocate_image_highmem(alloc - size);

Did you mean "="?

Assuming you did, this could be

        size_highmem = size + preallocate_image_highmem(alloc - size);
        if (size_highmem < alloc) {

> +               if (size_highmem < (alloc - size)) {

The inner parens were not necessary.

> +                       pr_err("Image allocation is %lu pages short, exit\n",
> +                               alloc - size - pages_highmem);
> +                       goto err_out;
> +               }
> +               pages_highmem += size_highmem;
>                 pages += pages_highmem + size;
>         }
>
> --

But overall it would be better to avoid bailing out.