[PATCH net v2] tun: fix return value when the number of iovs exceeds MAX_SKB_FRAGS

[wangyunjian <wangyunjian@huawei.com>]

From: Yunjian Wang <wangyunjian@huawei.com>

Currently the tun_napi_alloc_frags() function returns -ENOMEM when the
number of iovs exceeds MAX_SKB_FRAGS + 1. However this is inappropriate,
we should use -EMSGSIZE instead of -ENOMEM.

The following distinctions are matters:
1. the caller need to drop the bad packet when -EMSGSIZE is returned,
   which means meeting a persistent failure.
2. the caller can try again when -ENOMEM is returned, which means
   meeting a transient failure.

Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")
Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Acked-by: Willem de Bruijn <willemb@google.com>
---
v2:
  * update commit log suggested by Willem de Bruijn
---
 drivers/net/tun.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 2dc1988a8973..15c6dd7fb04c 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1365,7 +1365,7 @@ static struct sk_buff *tun_napi_alloc_frags(struct tun_file *tfile,
 	int i;
 
 	if (it->nr_segs > MAX_SKB_FRAGS + 1)
-		return ERR_PTR(-ENOMEM);
+		return ERR_PTR(-EMSGSIZE);
 
 	local_bh_disable();
 	skb = napi_get_frags(&tfile->napi);
-- 
2.23.0