[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>

3 files changed, 83 insertions, 146 deletions

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