net: wireless: intel: iwlwifi: fix GRO_NORMAL packet stalling
authorAlexander Lobakin <alobakin@dlink.ru>
Wed, 27 Nov 2019 09:41:23 +0000 (12:41 +0300)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 31 Dec 2019 15:45:49 +0000 (16:45 +0100)
commita18a0a5a50e59ec12d1fddabbd699e25b0e43d59
treefc38b6a07f8caf5d8c7242f0e14a34331bc10b16
parentce190475a8187121196cfe51e95b3b22d5e8a2b2
net: wireless: intel: iwlwifi: fix GRO_NORMAL packet stalling

[ Upstream commit b167191e2a851cb2e4c6ef8b91c83ff73ef41872 ]

Commit 6570bc79c0df ("net: core: use listified Rx for GRO_NORMAL in
napi_gro_receive()") has applied batched GRO_NORMAL packets processing
to all napi_gro_receive() users, including mac80211-based drivers.

However, this change has led to a regression in iwlwifi driver [1][2] as
it is required for NAPI users to call napi_complete_done() or
napi_complete() and the end of every polling iteration, whilst iwlwifi
doesn't use NAPI scheduling at all and just calls napi_gro_flush().
In that particular case, packets which have not been already flushed
from napi->rx_list stall in it until at least next Rx cycle.

Fix this by adding a manual flushing of the list to iwlwifi driver right
before napi_gro_flush() call to mimic napi_complete() logics.

I prefer to open-code gro_normal_list() rather than exporting it for 2
reasons:
* to prevent from using it and napi_gro_flush() in any new drivers,
  as it is the *really* bad way to use NAPI that should be avoided;
* to keep gro_normal_list() static and don't lose any CC optimizations.

I also don't add the "Fixes:" tag as the mentioned commit was only a
trigger that only exposed an improper usage of NAPI in this particular
driver.

[1] https://lore.kernel.org/netdev/PSXP216MB04388962C411CD0B17A86F47804A0@PSXP216MB0438.KORP216.PROD.OUTLOOK.COM
[2] https://bugzilla.kernel.org/show_bug.cgi?id=205647

Signed-off-by: Alexander Lobakin <alobakin@dlink.ru>
Acked-by: Luca Coelho <luciano.coelho@intel.com>
Reported-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
Tested-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
Reviewed-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
drivers/net/wireless/intel/iwlwifi/pcie/rx.c