[Devel] [PATCH VZ9] dm-qcow2-map: disable high-order allocation warning

[Alexey Kuznetsov]

Hmm.

What are chances to get 4M with GFP_NOIO? I do not even need
to guess, I know - 0.

Damn, this is not a legal code. Leave warn in place, it must complain.

If we cannot redo this using normal sized buffers, make a pool, make
a queue to wait for pool, or use kvmalloc, or whatever. But only not this.








On Mon, Nov 11, 2024 at 3:41 PM Pavel Tikhomirov
<ptikhomirov at virtuozzo.com> wrote:
>
> Disable the warning:
>
> kernel: order 10 >= 10, gfp 0x40c00
> kernel: WARNING: CPU: 5 PID: 182 at mm/page_alloc.c:5630 __alloc_pages+0x1d7/0x3f0
> kernel: process_compressed_read+0x6f/0x590 [dm_qcow2]
>
> As with 1M clusters and in case of zstd compression the buffer size
> (clu_size + sizeof(ZSTD_DCtx) + ZSTD_BLOCKSIZE_MAX + clu_size +
> ZSTD_BLOCKSIZE_MAX + 64 = 2520776) can only fit into 4M (10-th order)
> allocation.
>
> https://virtuozzo.atlassian.net/browse/VSTOR-94596
> Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
>
> Feature: dm-qcow2: ZSTD decompression
> ---
>  drivers/md/dm-qcow2-map.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/dm-qcow2-map.c b/drivers/md/dm-qcow2-map.c
> index 6585f3fac6e7b..18f9442493831 100644
> --- a/drivers/md/dm-qcow2-map.c
> +++ b/drivers/md/dm-qcow2-map.c
> @@ -3671,7 +3671,7 @@ static void process_compressed_read(struct qcow2 *qcow2, struct list_head *read_
>                 dctxlen = zlib_inflate_workspacesize();
>
>
> -       buf = kmalloc(qcow2->clu_size + dctxlen, GFP_NOIO);
> +       buf = kmalloc(qcow2->clu_size + dctxlen, GFP_NOIO | __GFP_ORDER_NOWARN);
>         if (!buf) {
>                 end_qios(read_list, BLK_STS_RESOURCE);
>                 return;
> --
> 2.47.0
>
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