net: update NAPI threaded config even for disabled NAPIs

We have to make sure that all future NAPIs will have the right threaded
state when the state is configured on the device level.
We chose not to have an "unset" state for threaded, and not to wipe
the NAPI config clean when channels are explicitly disabled.
This means the persistent config structs "exist" even when their NAPIs
are not instantiated.

Differently put - the NAPI persistent state lives in the net_device
(ncfg == struct napi_config):

    ,--- [napi 0] - [napi 1]
 [dev]      |          |
    `--- [ncfg 0] - [ncfg 1]

so say we a device with 2 queues but only 1 enabled:

    ,--- [napi 0]
 [dev]      |
    `--- [ncfg 0] - [ncfg 1]

now we set the device to threaded=1:

    ,---------- [napi 0 (thr:1)]
 [dev(thr:1)]      |
    `---------- [ncfg 0 (thr:1)] - [ncfg 1 (thr:?)]

Since [ncfg 1] was not attached to a NAPI during configuration we
skipped it. If we create a NAPI for it later it will have the old
setting (presumably disabled). One could argue if this is right
or not "in principle", but it's definitely not how things worked
before per-NAPI config..

Fixes: 2677010e7793 ("Add support to set NAPI threaded for individual NAPI")
Signed-off-by: Jakub Kicinski <[email protected]>
Reviewed-by: Joe Damato <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

1 files changed, 6 insertions, 1 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 68dc47d7e700..f180746382a1 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6999,7 +6999,7 @@ int netif_set_threaded(struct net_device *dev,
 		       enum netdev_napi_threaded threaded)
 {
 	struct napi_struct *napi;
-	int err = 0;
+	int i, err = 0;
 
 	netdev_assert_locked_or_invisible(dev);
 
@@ -7021,6 +7021,10 @@ int netif_set_threaded(struct net_device *dev,
 	list_for_each_entry(napi, &dev->napi_list, dev_list)
 		WARN_ON_ONCE(napi_set_threaded(napi, threaded));
 
+	/* Override the config for all NAPIs even if currently not listed */
+	for (i = 0; i < dev->num_napi_configs; i++)
+		dev->napi_config[i].threaded = threaded;
+
 	return err;
 }
 
@@ -11873,6 +11877,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 		goto free_all;
 	dev->cfg_pending = dev->cfg;
 
+	dev->num_napi_configs = maxqs;
 	napi_config_sz = array_size(maxqs, sizeof(*dev->napi_config));
 	dev->napi_config = kvzalloc(napi_config_sz, GFP_KERNEL_ACCOUNT);
 	if (!dev->napi_config)