Hi Johannes,

From: Johannes Berg <redacted>

This reverts commit d6f295e9def0; some userspace (in the case
we noticed it's wpa_supplicant), is relying on the current
error code to determine that a fixed name interface already
exists.

Reported-by: Jouni Malinen <redacted>
Signed-off-by: Johannes Berg <redacted>
---
 net/core/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

This revert seems to have broken networking on one of my powerpc
machines, according to git bisect.

The symptom is DHCP fails and I don't get a link, I didn't dig any
further than that. I can if it's helpful.

I think the problem is that 87c320e51519 ("net: core: dev_get_valid_name
is now the same as dev_alloc_name_ns") only makes sense while
d6f295e9def0 remains in the tree.

ie. before the entire series, dev_get_valid_name() would return EEXIST,
and that was retained when 87c320e51519 was merged, but now that
d6f295e9def0 has been reverted dev_get_valid_name() is returning ENFILE.

I can get the network up again if I also revert 87c320e51519 ("net:
core: dev_get_valid_name is now the same as dev_alloc_name_ns"), or with
the gross patch below.

cheers

diff --git a/net/core/dev.c b/net/core/dev.c
index f47e96b62308..d0304461ad32 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -1146,7 +1146,11 @@ EXPORT_SYMBOL(dev_alloc_name);
 int dev_get_valid_name(struct net *net, struct net_device *dev,
 		       const char *name)
 {
-	return dev_alloc_name_ns(net, dev, name);
+	int rc = dev_alloc_name_ns(net, dev, name);
+	if (rc == -ENFILE)
+		rc = -EEXIST;
+
+	return rc;
 }
 EXPORT_SYMBOL(dev_get_valid_name);