net: remove gfp_mask from napi_alloc_skb()

__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.

Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240327040213.3153864-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 1 insertions, 7 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 517e546a120a..b7f1ecdaec38 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3350,13 +3350,7 @@ static inline void *napi_alloc_frag_align(unsigned int fragsz,
 	return __napi_alloc_frag_align(fragsz, -align);
 }
 
-struct sk_buff *__napi_alloc_skb(struct napi_struct *napi,
-				 unsigned int length, gfp_t gfp_mask);
-static inline struct sk_buff *napi_alloc_skb(struct napi_struct *napi,
-					     unsigned int length)
-{
-	return __napi_alloc_skb(napi, length, GFP_ATOMIC);
-}
+struct sk_buff *napi_alloc_skb(struct napi_struct *napi, unsigned int length);
 void napi_consume_skb(struct sk_buff *skb, int budget);
 
 void napi_skb_free_stolen_head(struct sk_buff *skb);