Merge branch 'tpacket_snd-bugs' into main

Yun Lu says:

====================
fix two issues and optimize code on tpacket_snd()

This series fix two issues and optimize the code on tpacket_snd():
1, fix the SO_SNDTIMEO constraint not effective due to the changes in
commit 581073f;
2, fix a soft lockup issue on a specific edge case, and also optimize
the loop logic to be clearer and more obvious;

---
Changes in v5:
- Still combine fix and optimization together, change to while(1).
  Thanks: Willem de Bruijn.
- Link to v4: https://lore.kernel.org/all/[email protected]/

Changes in v4:
- Fix a typo and add the missing semicolon. Thanks: Simon Horman.
- Split the second patch into two, one to fix, another to optimize.
  Thanks: Willem de Bruijn
- Link to v3: https://lore.kernel.org/all/[email protected]/

Changes in v3:
- Split in two different patches.
- Simplify the code and reuse ph to continue. Thanks: Eric Dumazet.
- Link to v2: https://lore.kernel.org/all/[email protected]/

Changes in v2:
- Add a Fixes tag.
- Link to v1: https://lore.kernel.org/all/[email protected]/
====================

Signed-off-by: David S. Miller <[email protected]>

Author: davem330

net/packet/af_packet.c

@@ -2785,7 +2785,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
 	int len_sum = 0;
 	int status = TP_STATUS_AVAILABLE;
 	int hlen, tlen, copylen = 0;
-	long timeo = 0;
+	long timeo;
 
 	mutex_lock(&po->pg_vec_lock);
 
@@ -2839,22 +2839,28 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
 	if ((size_max > dev->mtu + reserve + VLAN_HLEN) && !vnet_hdr_sz)
 		size_max = dev->mtu + reserve + VLAN_HLEN;
 
+	timeo = sock_sndtimeo(&po->sk, msg->msg_flags & MSG_DONTWAIT);
 	reinit_completion(&po->skb_completion);
 
 	do {
 		ph = packet_current_frame(po, &po->tx_ring,
 					  TP_STATUS_SEND_REQUEST);
 		if (unlikely(ph == NULL)) {
-			if (need_wait && skb) {
-				timeo = sock_sndtimeo(&po->sk, msg->msg_flags & MSG_DONTWAIT);
+			/* Note: packet_read_pending() might be slow if we
+			 * have to call it as it's per_cpu variable, but in
+			 * fast-path we don't have to call it, only when ph
+			 * is NULL, we need to check the pending_refcnt.
+			 */
+			if (need_wait && packet_read_pending(&po->tx_ring)) {
 				timeo = wait_for_completion_interruptible_timeout(&po->skb_completion, timeo);
 				if (timeo <= 0) {
 					err = !timeo ? -ETIMEDOUT : -ERESTARTSYS;
 					goto out_put;
 				}
-			}
-			/* check for additional frames */
-			continue;
+				/* check for additional frames */
+				continue;
+			} else
+				break;
 		}
 
 		skb = NULL;
@@ -2943,14 +2949,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
 		}
 		packet_increment_head(&po->tx_ring);
 		len_sum += tp_len;
-	} while (likely((ph != NULL) ||
-		/* Note: packet_read_pending() might be slow if we have
-		 * to call it as it's per_cpu variable, but in fast-path
-		 * we already short-circuit the loop with the first
-		 * condition, and luckily don't have to go that path
-		 * anyway.
-		 */
-		 (need_wait && packet_read_pending(&po->tx_ring))));
+	} while (1);
 
 	err = len_sum;
 	goto out_put;