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Date: Wed, 28 Mar 2007 17:19:37 -0700 (PDT)
From: David Miller <davem@...emloft.net>
To: netdev@...r.kernel.org
Subject: [PATCH]: Make sacktag logic splittable...
It's nearly impossible to break out tcp_sacktag_write_queue() into
smaller worker functions because there are so many local variables
that are live and updated throughout the inner loop and beyond.
So create a state block so we can start simplifying this function
properly.
Pushed to net-2.6.22
commit eb7723322ccc43f19714ac83395e5204fee0e5b8
Author: David S. Miller <davem@...set.davemloft.net>
Date: Wed Mar 28 17:17:19 2007 -0700
[TCP]: Create tcp_sacktag_state.
It is difficult to break out the inner-logic of
tcp_sacktag_write_queue() into worker functions because
so many local variables get updated in-place.
Start to overcome this by creating a structure block
of state variables that can be passed around into
worker routines.
Signed-off-by: David S. Miller <davem@...emloft.net>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a5a8987..464dc80 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -936,6 +936,15 @@ static void tcp_update_reordering(struct sock *sk, const int metric,
* Both of these heuristics are not used in Loss state, when we cannot
* account for retransmits accurately.
*/
+struct tcp_sacktag_state {
+ unsigned int flag;
+ int dup_sack;
+ int reord;
+ int prior_fackets;
+ u32 lost_retrans;
+ int first_sack_index;
+};
+
static int tcp_check_dsack(struct tcp_sock *tp, struct sk_buff *ack_skb,
struct tcp_sack_block_wire *sp, int num_sacks,
u32 prior_snd_una)
@@ -980,23 +989,18 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2);
struct sk_buff *cached_skb;
int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
- int reord = tp->packets_out;
- int prior_fackets;
- u32 lost_retrans = 0;
- int flag = 0;
- int dup_sack = 0;
+ struct tcp_sacktag_state state;
int cached_fack_count;
int i;
- int first_sack_index;
+ int force_one_sack;
if (!tp->sacked_out) {
tp->fackets_out = 0;
tp->highest_sack = tp->snd_una;
} else
*mark_lost_entry_seq = tp->highest_sack;
- prior_fackets = tp->fackets_out;
- dup_sack = tcp_check_dsack(tp, ack_skb, sp, num_sacks, prior_snd_una);
+ state.dup_sack = tcp_check_dsack(tp, ack_skb, sp, num_sacks, prior_snd_una);
/* Eliminate too old ACKs, but take into
* account more or less fresh ones, they can
@@ -1009,18 +1013,18 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
* if the only SACK change is the increase of the end_seq of
* the first block then only apply that SACK block
* and use retrans queue hinting otherwise slowpath */
- flag = 1;
+ force_one_sack = 1;
for (i = 0; i < num_sacks; i++) {
__be32 start_seq = sp[i].start_seq;
__be32 end_seq = sp[i].end_seq;
if (i == 0) {
if (tp->recv_sack_cache[i].start_seq != start_seq)
- flag = 0;
+ force_one_sack = 0;
} else {
if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
(tp->recv_sack_cache[i].end_seq != end_seq))
- flag = 0;
+ force_one_sack = 0;
}
tp->recv_sack_cache[i].start_seq = start_seq;
tp->recv_sack_cache[i].end_seq = end_seq;
@@ -1031,8 +1035,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
tp->recv_sack_cache[i].end_seq = 0;
}
- first_sack_index = 0;
- if (flag)
+ state.first_sack_index = 0;
+ if (force_one_sack)
num_sacks = 1;
else {
int j;
@@ -1050,17 +1054,14 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
sp[j+1] = tmp;
/* Track where the first SACK block goes to */
- if (j == first_sack_index)
- first_sack_index = j+1;
+ if (j == state.first_sack_index)
+ state.first_sack_index = j+1;
}
}
}
}
- /* clear flag as used for different purpose in following code */
- flag = 0;
-
/* Use SACK fastpath hint if valid */
cached_skb = tp->fastpath_skb_hint;
cached_fack_count = tp->fastpath_cnt_hint;
@@ -1069,6 +1070,11 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
cached_fack_count = 0;
}
+ state.flag = 0;
+ state.reord = tp->packets_out;
+ state.prior_fackets = tp->fackets_out;
+ state.lost_retrans = 0;
+
for (i=0; i<num_sacks; i++, sp++) {
struct sk_buff *skb;
__u32 start_seq = ntohl(sp->start_seq);
@@ -1080,7 +1086,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
/* Event "B" in the comment above. */
if (after(end_seq, tp->high_seq))
- flag |= FLAG_DATA_LOST;
+ state.flag |= FLAG_DATA_LOST;
tcp_for_write_queue_from(skb, sk) {
int in_sack, pcount;
@@ -1091,7 +1097,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
cached_skb = skb;
cached_fack_count = fack_count;
- if (i == first_sack_index) {
+ if (i == state.first_sack_index) {
tp->fastpath_skb_hint = skb;
tp->fastpath_cnt_hint = fack_count;
}
@@ -1130,7 +1136,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
sacked = TCP_SKB_CB(skb)->sacked;
/* Account D-SACK for retransmitted packet. */
- if ((dup_sack && in_sack) &&
+ if ((state.dup_sack && in_sack) &&
(sacked & TCPCB_RETRANS) &&
after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
tp->undo_retrans--;
@@ -1138,14 +1144,14 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
/* The frame is ACKed. */
if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
if (sacked&TCPCB_RETRANS) {
- if ((dup_sack && in_sack) &&
+ if ((state.dup_sack && in_sack) &&
(sacked&TCPCB_SACKED_ACKED))
- reord = min(fack_count, reord);
+ state.reord = min(fack_count, state.reord);
} else {
/* If it was in a hole, we detected reordering. */
- if (fack_count < prior_fackets &&
+ if (fack_count < state.prior_fackets &&
!(sacked&TCPCB_SACKED_ACKED))
- reord = min(fack_count, reord);
+ state.reord = min(fack_count, state.reord);
}
/* Nothing to do; acked frame is about to be dropped. */
@@ -1154,8 +1160,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
if ((sacked&TCPCB_SACKED_RETRANS) &&
after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
- (!lost_retrans || after(end_seq, lost_retrans)))
- lost_retrans = end_seq;
+ (!state.lost_retrans || after(end_seq, state.lost_retrans)))
+ state.lost_retrans = end_seq;
if (!in_sack)
continue;
@@ -1179,8 +1185,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
* which was in hole. It is reordering.
*/
if (!(sacked & TCPCB_RETRANS) &&
- fack_count < prior_fackets)
- reord = min(fack_count, reord);
+ fack_count < state.prior_fackets)
+ state.reord = min(fack_count, state.reord);
if (sacked & TCPCB_LOST) {
TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
@@ -1196,15 +1202,15 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
* Clearing correct due to in-order walk
*/
if (after(end_seq, tp->frto_highmark)) {
- flag &= ~FLAG_ONLY_ORIG_SACKED;
+ state.flag &= ~FLAG_ONLY_ORIG_SACKED;
} else {
if (!(sacked & TCPCB_RETRANS))
- flag |= FLAG_ONLY_ORIG_SACKED;
+ state.flag |= FLAG_ONLY_ORIG_SACKED;
}
}
TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
- flag |= FLAG_DATA_SACKED;
+ state.flag |= FLAG_DATA_SACKED;
tp->sacked_out += tcp_skb_pcount(skb);
if (fack_count > tp->fackets_out)
@@ -1214,8 +1220,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
tp->highest_sack))
tp->highest_sack = TCP_SKB_CB(skb)->seq;
} else {
- if (dup_sack && (sacked&TCPCB_RETRANS))
- reord = min(fack_count, reord);
+ if (state.dup_sack && (sacked&TCPCB_RETRANS))
+ state.reord = min(fack_count, state.reord);
}
/* D-SACK. We can detect redundant retransmission
@@ -1223,7 +1229,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
* undo_retrans is decreased above, L|R frames
* are accounted above as well.
*/
- if (dup_sack &&
+ if (state.dup_sack &&
(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
tp->retrans_out -= tcp_skb_pcount(skb);
@@ -1251,20 +1257,20 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
* we have to account for reordering! Ugly,
* but should help.
*/
- if (IsFack(tp) && lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) {
+ if (IsFack(tp) && state.lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) {
struct sk_buff *skb;
tcp_for_write_queue(skb, sk) {
if (skb == tcp_send_head(sk))
break;
- if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
+ if (after(TCP_SKB_CB(skb)->seq, state.lost_retrans))
break;
if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
continue;
if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
- after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
+ after(state.lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
(IsFack(tp) ||
- !before(lost_retrans,
+ !before(state.lost_retrans,
TCP_SKB_CB(skb)->ack_seq + tp->reordering *
tp->mss_cache))) {
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
@@ -1276,7 +1282,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
tp->lost_out += tcp_skb_pcount(skb);
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
- flag |= FLAG_DATA_SACKED;
+ state.flag |= FLAG_DATA_SACKED;
NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
}
}
@@ -1285,9 +1291,9 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
tp->left_out = tp->sacked_out + tp->lost_out;
- if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss &&
+ if ((state.reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss &&
(!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
- tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0);
+ tcp_update_reordering(sk, ((tp->fackets_out + 1) - state.reord), 0);
#if FASTRETRANS_DEBUG > 0
BUG_TRAP((int)tp->sacked_out >= 0);
@@ -1295,7 +1301,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
BUG_TRAP((int)tp->retrans_out >= 0);
BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
#endif
- return flag;
+ return state.flag;
}
/* F-RTO can only be used if these conditions are satisfied:
-
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