Re: [PATCH] dma/pool: do not complain if DMA pool is not allocated

Michal Hocko
2022-03-25T12:58:49Z

On Fri 25-03-22 13:25:59, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
>
> we have a system complainging about order-5 allocation for the DMA pool.
> This is something that a674e48c5443 ("dma/pool: create dma atomic pool
> only if dma zone has managed pages") has already tried to achieve but I
> do not think it went all the way to have it covered completely. In this
> particular case has_managed_dma() will not work because:
> [ 0.678539][ T0] Initmem setup node 0 [mem 0x0000000000001000-0x000000027dffffff]
> [ 0.686316][ T0] On node 0, zone DMA: 1 pages in unavailable ranges
> [ 0.687093][ T0] On node 0, zone DMA32: 36704 pages in unavailable ranges
> [ 0.694278][ T0] On node 0, zone Normal: 53252 pages in unavailable ranges
> [ 0.701257][ T0] On node 0, zone Normal: 8192 pages in unavailable ranges

Dang, I have just realized that I have misread the boot log and it has
turned out that a674e48c5443 is covering my situation because the
allocation failure message says:
Node 0 DMA free:0kB boost:0kB min:0kB low:0kB high:0kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:636kB managed:0kB mlocked:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB

I thought there are only few pages in the managed by the DMA zone. This
is still theoretically possible so I think __GFP_NOWARN makes sense here
but it would require to change the patch description.

Is this really worth it?

>
> The allocation failure on the DMA zone shouldn't be really critical for
> the system operation so just silence the warning instead.
>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
> kernel/dma/pool.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
> index 4d40dcce7604..1bf6de398986 100644
> --- a/kernel/dma/pool.c
> +++ b/kernel/dma/pool.c
> @@ -205,7 +205,7 @@ static int __init dma_atomic_pool_init(void)
> ret = -ENOMEM;
> if (has_managed_dma()) {
> atomic_pool_dma = __dma_atomic_pool_init(atomic_pool_size,
> - GFP_KERNEL | GFP_DMA);
> + GFP_KERNEL | GFP_DMA | __GFP_NOWARN);
> if (!atomic_pool_dma)
> ret = -ENOMEM;
> }
> --
> 2.30.2

--
Michal Hocko
SUSE Labs