[TFRC]: Migrate TX history to singly-linked lis

This patch was based on another made by Gerrit Renker, his changelog was:

    ------------------------------------------------------
The patch set migrates TFRC TX history to a singly-linked list.

The details are:
 * use of a consistent naming scheme (all TFRC functions now begin with `tfrc_');
 * allocation and cleanup are taken care of internally;
 * provision of a lookup function, which is used by the CCID TX infrastructure
   to determine the time a packet was sent (in turn used for RTT sampling);
 * integration of the new interface with the present use in CCID3.
    ------------------------------------------------------

Simplifications I did:

. removing the tfrc_tx_hist_head that had a pointer to the list head and
  another for the slabcache.
. No need for creating a slabcache for each CCID that wants to use the TFRC
  tx history routines, create a single slabcache when the dccp_tfrc_lib module
  init routine is called.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 40 deletions

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 42893b1dfa09..f73542ab9d08 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -49,7 +49,6 @@ static int ccid3_debug;
 #define ccid3_pr_debug(format, a...)
 #endif
 
-static struct dccp_tx_hist *ccid3_tx_hist;
 static struct dccp_rx_hist *ccid3_rx_hist;
 
 /*
@@ -389,28 +388,18 @@ static void ccid3_hc_tx_packet_sent(struct sock *sk, int more,
                                     unsigned int len)
 {
         struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
-        struct dccp_tx_hist_entry *packet;
 
         ccid3_hc_tx_update_s(hctx, len);
 
-        packet = dccp_tx_hist_entry_new(ccid3_tx_hist, GFP_ATOMIC);
-        if (unlikely(packet == NULL)) {
+        if (tfrc_tx_hist_add(&hctx->ccid3hctx_hist, dccp_sk(sk)->dccps_gss))
                 DCCP_CRIT("packet history - out of memory!");
-                return;
-        }
-        dccp_tx_hist_add_entry(&hctx->ccid3hctx_hist, packet);
-
-        packet->dccphtx_tstamp = ktime_get_real();
-        packet->dccphtx_seqno  = dccp_sk(sk)->dccps_gss;
-        packet->dccphtx_rtt    = hctx->ccid3hctx_rtt;
-        packet->dccphtx_sent   = 1;
 }
 
 static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 {
         struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
         struct ccid3_options_received *opt_recv;
-        struct dccp_tx_hist_entry *packet;
+        struct tfrc_tx_hist_entry *packet;
         ktime_t now;
         unsigned long t_nfb;
         u32 pinv, r_sample;
@@ -425,16 +414,19 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
         switch (hctx->ccid3hctx_state) {
         case TFRC_SSTATE_NO_FBACK:
         case TFRC_SSTATE_FBACK:
-                /* get packet from history to look up t_recvdata */
-                packet = dccp_tx_hist_find_entry(&hctx->ccid3hctx_hist,
-                                              DCCP_SKB_CB(skb)->dccpd_ack_seq);
-                if (unlikely(packet == NULL)) {
-                        DCCP_WARN("%s(%p), seqno %llu(%s) doesn't exist "
-                                  "in history!\n",  dccp_role(sk), sk,
-                            (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
-                                dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type));
+                /* estimate RTT from history if ACK number is valid */
+                packet = tfrc_tx_hist_find_entry(hctx->ccid3hctx_hist,
+                                                 DCCP_SKB_CB(skb)->dccpd_ack_seq);
+                if (packet == NULL) {
+                        DCCP_WARN("%s(%p): %s with bogus ACK-%llu\n", dccp_role(sk), sk,
+                                  dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type),
+                                  (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq);
                         return;
                 }
+                /*
+                 * Garbage-collect older (irrelevant) entries
+                 */
+                tfrc_tx_hist_purge(&packet->next);
 
                 /* Update receive rate in units of 64 * bytes/second */
                 hctx->ccid3hctx_x_recv = opt_recv->ccid3or_receive_rate;
@@ -451,7 +443,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 /*
                  * Calculate new RTT sample and update moving average
                  */
-                r_sample = dccp_sample_rtt(sk, ktime_us_delta(now, packet->dccphtx_tstamp));
+                r_sample = dccp_sample_rtt(sk, ktime_us_delta(now, packet->stamp));
                 hctx->ccid3hctx_rtt = tfrc_ewma(hctx->ccid3hctx_rtt, r_sample, 9);
 
                 if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
@@ -493,9 +485,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 /* unschedule no feedback timer */
                 sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);
 
-                /* remove all packets older than the one acked from history */
-                dccp_tx_hist_purge_older(ccid3_tx_hist,
-                                         &hctx->ccid3hctx_hist, packet);
                 /*
                  * As we have calculated new ipi, delta, t_nom it is possible
                  * that we now can send a packet, so wake up dccp_wait_for_ccid
@@ -598,7 +587,7 @@ static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk)
         struct ccid3_hc_tx_sock *hctx = ccid_priv(ccid);
 
         hctx->ccid3hctx_state = TFRC_SSTATE_NO_SENT;
-        INIT_LIST_HEAD(&hctx->ccid3hctx_hist);
+        hctx->ccid3hctx_hist = NULL;
         setup_timer(&hctx->ccid3hctx_no_feedback_timer,
                         ccid3_hc_tx_no_feedback_timer, (unsigned long)sk);
 
@@ -612,8 +601,7 @@ static void ccid3_hc_tx_exit(struct sock *sk)
         ccid3_hc_tx_set_state(sk, TFRC_SSTATE_TERM);
         sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);
 
-        /* Empty packet history */
-        dccp_tx_hist_purge(ccid3_tx_hist, &hctx->ccid3hctx_hist);
+        tfrc_tx_hist_purge(&hctx->ccid3hctx_hist);
 }
 
 static void ccid3_hc_tx_get_info(struct sock *sk, struct tcp_info *info)
@@ -1036,19 +1024,12 @@ static __init int ccid3_module_init(void)
         if (ccid3_rx_hist == NULL)
                 goto out;
 
-        ccid3_tx_hist = dccp_tx_hist_new("ccid3");
-        if (ccid3_tx_hist == NULL)
-                goto out_free_rx;
-
         rc = ccid_register(&ccid3);
         if (rc != 0)
-                goto out_free_tx;
+                goto out_free_rx;
 out:
         return rc;
 
-out_free_tx:
-        dccp_tx_hist_delete(ccid3_tx_hist);
-        ccid3_tx_hist = NULL;
 out_free_rx:
         dccp_rx_hist_delete(ccid3_rx_hist);
         ccid3_rx_hist = NULL;
@@ -1060,10 +1041,6 @@ static __exit void ccid3_module_exit(void)
 {
         ccid_unregister(&ccid3);
 
-        if (ccid3_tx_hist != NULL) {
-                dccp_tx_hist_delete(ccid3_tx_hist);
-                ccid3_tx_hist = NULL;
-        }
         if (ccid3_rx_hist != NULL) {
                 dccp_rx_hist_delete(ccid3_rx_hist);
                 ccid3_rx_hist = NULL;