2022-04-05 03:47:20

by Xiaomeng Tong

Subject: [RESEND][PATCH v2] myri10ge: remove an unneeded NULL check

The define of skb_list_walk_safe(first, skb, next_skb) is:
for ((skb) = (first), (next_skb) = (skb) ? (skb)->next : NULL; (skb); \
(skb) = (next_skb), (next_skb) = (skb) ? (skb)->next : NULL)

Thus, if the 'segs' passed as 'first' into the skb_list_walk_safe is NULL,
the loop will exit immediately. In other words, it can be sure the 'segs'
is non-NULL when we run inside the loop. So just remove the unnecessary
NULL check. Also remove the unneeded assignmnets.

Signed-off-by: Xiaomeng Tong <[email protected]>
---
changes since v1:
- remove the unneeded assignmnets.

v1: https://lore.kernel.org/lkml/[email protected]/
---
drivers/net/ethernet/myricom/myri10ge/myri10ge.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
index 50ac3ee2577a..071657e3dba8 100644
--- a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
+++ b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
@@ -2903,12 +2903,8 @@ static netdev_tx_t myri10ge_sw_tso(struct sk_buff *skb,
status = myri10ge_xmit(curr, dev);
if (status != 0) {
dev_kfree_skb_any(curr);
- if (segs != NULL) {
- curr = segs;
- segs = next;
- curr->next = NULL;
- dev_kfree_skb_any(segs);
- }
+ segs->next = NULL;
+ dev_kfree_skb_any(next);
goto drop;
}
}
--
2.17.1

2022-04-06 15:14:37

by Jakub Kicinski

Subject: Re: [RESEND][PATCH v2] myri10ge: remove an unneeded NULL check

On Tue, 5 Apr 2022 08:05:53 +0800 Xiaomeng Tong wrote:
> The define of skb_list_walk_safe(first, skb, next_skb) is:
> for ((skb) = (first), (next_skb) = (skb) ? (skb)->next : NULL; (skb); \
> (skb) = (next_skb), (next_skb) = (skb) ? (skb)->next : NULL)
>
> Thus, if the 'segs' passed as 'first' into the skb_list_walk_safe is NULL,
> the loop will exit immediately. In other words, it can be sure the 'segs'
> is non-NULL when we run inside the loop. So just remove the unnecessary
> NULL check. Also remove the unneeded assignmnets.
>
> Signed-off-by: Xiaomeng Tong <[email protected]>

The existing code is pretty clearly buggy. Please fix the bugs or don't
touch it. You're obfuscating what the original intention was.

> diff --git a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
> index 50ac3ee2577a..071657e3dba8 100644
> --- a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
> +++ b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
> @@ -2903,12 +2903,8 @@ static netdev_tx_t myri10ge_sw_tso(struct sk_buff *skb,
> status = myri10ge_xmit(curr, dev);
> if (status != 0) {
> dev_kfree_skb_any(curr);
> - if (segs != NULL) {
> - curr = segs;
> - segs = next;
> - curr->next = NULL;
> - dev_kfree_skb_any(segs);
> - }
> + segs->next = NULL;
> + dev_kfree_skb_any(next);
> goto drop;
> }
> }