[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>

5 files changed, 102 insertions, 187 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;
diff --git a/net/dccp/ccids/ccid3.h b/net/dccp/ccids/ccid3.h
index 36eca34228f0..b842a7dd99de 100644
--- a/net/dccp/ccids/ccid3.h
+++ b/net/dccp/ccids/ccid3.h
@@ -40,6 +40,7 @@
 #include <linux/list.h>
 #include <linux/types.h>
 #include <linux/tfrc.h>
+#include "lib/packet_history.h"
 #include "../ccid.h"
 
 /* Two seconds as per RFC 3448 4.2 */
@@ -111,7 +112,7 @@ struct ccid3_hc_tx_sock {
         ktime_t                         ccid3hctx_t_ld;
         ktime_t                         ccid3hctx_t_nom;
         u32                             ccid3hctx_delta;
-        struct list_head                ccid3hctx_hist;
+        struct tfrc_tx_hist_entry       *ccid3hctx_hist;
         struct ccid3_options_received   ccid3hctx_options_received;
 };
 
diff --git a/net/dccp/ccids/lib/loss_interval.c b/net/dccp/ccids/lib/loss_interval.c
index d26b88dbbb45..f2ca4eb74ddb 100644
--- a/net/dccp/ccids/lib/loss_interval.c
+++ b/net/dccp/ccids/lib/loss_interval.c
@@ -277,7 +277,7 @@ void dccp_li_update_li(struct sock *sk,
 
 EXPORT_SYMBOL_GPL(dccp_li_update_li);
 
-static __init int dccp_li_init(void)
+int __init dccp_li_init(void)
 {
         dccp_li_cachep = kmem_cache_create("dccp_li_hist",
                                            sizeof(struct dccp_li_hist_entry),
@@ -285,10 +285,10 @@ static __init int dccp_li_init(void)
         return dccp_li_cachep == NULL ? -ENOBUFS : 0;
 }
 
-static __exit void dccp_li_exit(void)
+void dccp_li_exit(void)
 {
-        kmem_cache_destroy(dccp_li_cachep);
+        if (dccp_li_cachep != NULL) {
+                kmem_cache_destroy(dccp_li_cachep);
+                dccp_li_cachep = NULL;
+        }
 }
-
-module_init(dccp_li_init);
-module_exit(dccp_li_exit);
diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c
index 34c4f6047724..139736064713 100644
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -1,7 +1,8 @@
 /*
  *  net/dccp/packet_history.c
  *
- *  Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
+ *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
+ *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
  *
  *  An implementation of the DCCP protocol
  *
@@ -39,93 +40,48 @@
 #include "packet_history.h"
 
 /*
- *      Transmitter History Routines
+ * Transmitter History Routines
  */
-struct dccp_tx_hist *dccp_tx_hist_new(const char *name)
-{
-        struct dccp_tx_hist *hist = kmalloc(sizeof(*hist), GFP_ATOMIC);
-        static const char dccp_tx_hist_mask[] = "tx_hist_%s";
-        char *slab_name;
+static struct kmem_cache *tfrc_tx_hist;
 
-        if (hist == NULL)
-                goto out;
-
-        slab_name = kmalloc(strlen(name) + sizeof(dccp_tx_hist_mask) - 1,
-                            GFP_ATOMIC);
-        if (slab_name == NULL)
-                goto out_free_hist;
-
-        sprintf(slab_name, dccp_tx_hist_mask, name);
-        hist->dccptxh_slab = kmem_cache_create(slab_name,
-                                             sizeof(struct dccp_tx_hist_entry),
-                                               0, SLAB_HWCACHE_ALIGN,
-                                               NULL);
-        if (hist->dccptxh_slab == NULL)
-                goto out_free_slab_name;
-out:
-        return hist;
-out_free_slab_name:
-        kfree(slab_name);
-out_free_hist:
-        kfree(hist);
-        hist = NULL;
-        goto out;
-}
-
-EXPORT_SYMBOL_GPL(dccp_tx_hist_new);
-
-void dccp_tx_hist_delete(struct dccp_tx_hist *hist)
+struct tfrc_tx_hist_entry *
+        tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
 {
-        const char* name = kmem_cache_name(hist->dccptxh_slab);
+        while (head != NULL && head->seqno != seqno)
+                head = head->next;
 
-        kmem_cache_destroy(hist->dccptxh_slab);
-        kfree(name);
-        kfree(hist);
+        return head;
 }
+EXPORT_SYMBOL_GPL(tfrc_tx_hist_find_entry);
 
-EXPORT_SYMBOL_GPL(dccp_tx_hist_delete);
-
-struct dccp_tx_hist_entry *
-        dccp_tx_hist_find_entry(const struct list_head *list, const u64 seq)
+int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
 {
-        struct dccp_tx_hist_entry *packet = NULL, *entry;
-
-        list_for_each_entry(entry, list, dccphtx_node)
-                if (entry->dccphtx_seqno == seq) {
-                        packet = entry;
-                        break;
-                }
-
-        return packet;
+        struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist, gfp_any());
+
+        if (entry == NULL)
+                return -ENOBUFS;
+        entry->seqno = seqno;
+        entry->stamp = ktime_get_real();
+        entry->next  = *headp;
+        *headp       = entry;
+        return 0;
 }
+EXPORT_SYMBOL_GPL(tfrc_tx_hist_add);
 
-EXPORT_SYMBOL_GPL(dccp_tx_hist_find_entry);
-
-void dccp_tx_hist_purge(struct dccp_tx_hist *hist, struct list_head *list)
+void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
 {
-        struct dccp_tx_hist_entry *entry, *next;
+        struct tfrc_tx_hist_entry *head = *headp;
 
-        list_for_each_entry_safe(entry, next, list, dccphtx_node) {
-                list_del_init(&entry->dccphtx_node);
-                dccp_tx_hist_entry_delete(hist, entry);
-        }
-}
-
-EXPORT_SYMBOL_GPL(dccp_tx_hist_purge);
+        while (head != NULL) {
+                struct tfrc_tx_hist_entry *next = head->next;
 
-void dccp_tx_hist_purge_older(struct dccp_tx_hist *hist,
-                              struct list_head *list,
-                              struct dccp_tx_hist_entry *packet)
-{
-        struct dccp_tx_hist_entry *next;
-
-        list_for_each_entry_safe_continue(packet, next, list, dccphtx_node) {
-                list_del_init(&packet->dccphtx_node);
-                dccp_tx_hist_entry_delete(hist, packet);
+                kmem_cache_free(tfrc_tx_hist, head);
+                head = next;
         }
-}
 
-EXPORT_SYMBOL_GPL(dccp_tx_hist_purge_older);
+        *headp = NULL;
+}
+EXPORT_SYMBOL_GPL(tfrc_tx_hist_purge);
 
 /*
  *      Receiver History Routines
@@ -147,8 +103,7 @@ struct dccp_rx_hist *dccp_rx_hist_new(const char *name)
         sprintf(slab_name, dccp_rx_hist_mask, name);
         hist->dccprxh_slab = kmem_cache_create(slab_name,
                                              sizeof(struct dccp_rx_hist_entry),
-                                               0, SLAB_HWCACHE_ALIGN,
-                                               NULL);
+                                             0, SLAB_HWCACHE_ALIGN, NULL);
         if (hist->dccprxh_slab == NULL)
                 goto out_free_slab_name;
 out:
@@ -293,6 +248,37 @@ void dccp_rx_hist_purge(struct dccp_rx_hist *hist, struct list_head *list)
 
 EXPORT_SYMBOL_GPL(dccp_rx_hist_purge);
 
+extern int __init dccp_li_init(void);
+extern void dccp_li_exit(void);
+
+static __init int packet_history_init(void)
+{
+        if (dccp_li_init() != 0)
+                goto out;
+
+        tfrc_tx_hist = kmem_cache_create("tfrc_tx_hist",
+                                         sizeof(struct tfrc_tx_hist_entry), 0,
+                                         SLAB_HWCACHE_ALIGN, NULL);
+        if (tfrc_tx_hist == NULL)
+                goto out_li_exit;
+
+        return 0;
+out_li_exit:
+        dccp_li_exit();
+out:
+        return -ENOBUFS;
+}
+module_init(packet_history_init);
+
+static __exit void packet_history_exit(void)
+{
+        if (tfrc_tx_hist != NULL) {
+                kmem_cache_destroy(tfrc_tx_hist);
+                tfrc_tx_hist = NULL;
+        }
+        dccp_li_exit();
+}
+module_exit(packet_history_exit);
 
 MODULE_AUTHOR("Ian McDonald <ian.mcdonald@jandi.co.nz>, "
               "Arnaldo Carvalho de Melo <acme@ghostprotocols.net>");
diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h
index 032bb61c6e39..5c07182dd659 100644
--- a/net/dccp/ccids/lib/packet_history.h
+++ b/net/dccp/ccids/lib/packet_history.h
@@ -1,10 +1,9 @@
 /*
- *  net/dccp/packet_history.h
+ *  Packet RX/TX history data structures and routines for TFRC-based protocols.
  *
+ *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
  *  Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
  *
- *  An implementation of the DCCP protocol
- *
  *  This code has been developed by the University of Waikato WAND
  *  research group. For further information please see http://www.wand.net.nz/
  *  or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
@@ -49,71 +48,23 @@
 #define TFRC_WIN_COUNT_PER_RTT   4
 #define TFRC_WIN_COUNT_LIMIT    16
 
-/*
- *      Transmitter History data structures and declarations
+/**
+ *  tfrc_tx_hist_entry  -  Simple singly-linked TX history list
+ *  @next:  next oldest entry (LIFO order)
+ *  @seqno: sequence number of this entry
+ *  @stamp: send time of packet with sequence number @seqno
  */
-struct dccp_tx_hist_entry {
-        struct list_head dccphtx_node;
-        u64              dccphtx_seqno:48,
-                         dccphtx_sent:1;
-        u32              dccphtx_rtt;
-        ktime_t          dccphtx_tstamp;
-};
-
-struct dccp_tx_hist {
-        struct kmem_cache *dccptxh_slab;
+struct tfrc_tx_hist_entry {
+        struct tfrc_tx_hist_entry *next;
+        u64                       seqno;
+        ktime_t                   stamp;
 };
 
-extern struct dccp_tx_hist *dccp_tx_hist_new(const char *name);
-extern void                 dccp_tx_hist_delete(struct dccp_tx_hist *hist);
-
-static inline struct dccp_tx_hist_entry *
-                        dccp_tx_hist_entry_new(struct dccp_tx_hist *hist,
-                                               const gfp_t prio)
-{
-        struct dccp_tx_hist_entry *entry = kmem_cache_alloc(hist->dccptxh_slab,
-                                                            prio);
-
-        if (entry != NULL)
-                entry->dccphtx_sent = 0;
-
-        return entry;
-}
-
-static inline struct dccp_tx_hist_entry *
-                        dccp_tx_hist_head(struct list_head *list)
-{
-        struct dccp_tx_hist_entry *head = NULL;
-
-        if (!list_empty(list))
-                head = list_entry(list->next, struct dccp_tx_hist_entry,
-                                  dccphtx_node);
-        return head;
-}
-
-extern struct dccp_tx_hist_entry *
-                        dccp_tx_hist_find_entry(const struct list_head *list,
-                                                const u64 seq);
-
-static inline void dccp_tx_hist_add_entry(struct list_head *list,
-                                          struct dccp_tx_hist_entry *entry)
-{
-        list_add(&entry->dccphtx_node, list);
-}
-
-static inline void dccp_tx_hist_entry_delete(struct dccp_tx_hist *hist,
-                                             struct dccp_tx_hist_entry *entry)
-{
-        if (entry != NULL)
-                kmem_cache_free(hist->dccptxh_slab, entry);
-}
-
-extern void dccp_tx_hist_purge(struct dccp_tx_hist *hist,
-                               struct list_head *list);
+extern int  tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno);
+extern void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp);
 
-extern void dccp_tx_hist_purge_older(struct dccp_tx_hist *hist,
-                                     struct list_head *list,
-                                     struct dccp_tx_hist_entry *next);
+extern struct tfrc_tx_hist_entry *
+        tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 ackno);
 
 /*
  *      Receiver History data structures and declarations