Re: [PATCH net-next] net: remove gfp_mask from napi_alloc_skb()

[Alexander Lobakin <aleksander.lobakin@intel.com>]

From: Jakub Kicinski <kuba@kernel.org>
Date: Mon, 25 Mar 2024 15:41:14 -0700

> __napi_alloc_skb() is napi_alloc_skb() with the added flexibility
> of choosing gfp_mask. This is a NAPI function, so GFP_ATOMIC is
> implied. The only practical choice the caller has is whether to
> set __GFP_NOWARN. But that's a false choice, too, allocation failures
> in atomic context will happen, and printing warnings in logs,
> effectively for a packet drop, is both too much and very likely
> non-actionable.
> 
> This leads me to a conclusion that most uses of napi_alloc_skb()
> are simply misguided, and should use __GFP_NOWARN in the first
> place. We also have a "standard" way of reporting allocation
> failures via the queue stat API (qstats::rx-alloc-fail).
> 
> The direct motivation for this patch is that one of the drivers
> used at Meta calls napi_alloc_skb() (so prior to this patch without
> __GFP_NOWARN), and the resulting OOM warning is the top networking
> warning in our fleet.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Nice cleanup!

Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>

> ---
> This is changing mostly the Intel drivers, if the choice of
> flags is important there, please do let me know, why IDPF
> uses bare GFP_ATOMIC, specifically.

idpf uses bare atomic w/o nowarn because the author didn't pay attention
to it. The change is totally safe.

Thanks,
Olek