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/*
* net.c - network stuff for DNBD
* Copyright (C) 2006 Thorsten Zitterell <thorsten@zitterell.de>
*/
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/random.h>
#include "net.h"
/* return pointer to server structure */
dnbd_server_t *dnbd_get_server(dnbd_servers_t * servers, int id)
{
if ((0 < id) && (id <= SERVERS_MAX))
return &servers->serverlist[id - 1];
else
return NULL;
}
/* add a new server */
int dnbd_set_serverid(dnbd_servers_t * servers, int id)
{
int result = -EINVAL;
dnbd_server_t *server;
if (!(server = dnbd_get_server(servers, id)))
goto out;
switch (server->state) {
case SERVER_INACTIVE:
break;
case SERVER_ACTIVE:
result = -EEXIST;
goto out;
case SERVER_STALLED:
server->state = SERVER_ACTIVE;
result = 0;
goto out;
}
server->state = SERVER_ACTIVE;
server->id = id;
server->srtt = servers->timeout_min;
server->weight = 0;
server->last_rx = jiffies;
server->last_tx = jiffies;
servers->count++;
result = 0;
out:
return result;
}
/* return server according to their weights (= probability) */
int dnbd_next_server(dnbd_servers_t * servers)
{
int i;
char rnd;
dnbd_server_t *server = NULL;
int id = 0;
int weightsum = 0;
/* get random byte from kernel */
get_random_bytes(&rnd, 1);
for (i = 0; i < SERVERS_MAX; i++) {
server = &servers->serverlist[i];
if ((server->state == SERVER_ACTIVE)
&& ((weightsum += server->weight) > (unsigned char) rnd)) {
id = server->id;
break;
}
}
/* alternatively, use server with highest weight */
/* for (i = 0; i < SERVERS_MAX; i++) {
server = &servers->serverlist[i];
if ((server->state == SERVER_ACTIVE)
&& (server->weight > weight))
id = server->id;
}*/
return id;
}
/* remove a server */
void dnbd_rem_servers(dnbd_servers_t * servers)
{
if (!servers->serverlist)
return;
kfree(servers->serverlist);
servers->serverlist = NULL;
}
/* remove all servers */
void dnbd_clean_servers(dnbd_servers_t * servers)
{
int i;
for (i = 0; i < SERVERS_MAX; i++) {
servers->serverlist[i].state = 0;
}
}
/* update round trip time of a server */
void dnbd_rtt_server(dnbd_servers_t * servers, int id, int rtt)
{
dnbd_server_t *server;
if (!(server = dnbd_get_server(servers, id)))
goto out;
if (rtt > servers->timeout_max)
rtt = TIMEOUT_MAX;
else if (rtt < servers->timeout_min)
rtt = TIMEOUT_MIN;
down(&servers->sema);
server->srtt = ((SRTT_BETA * server->srtt
+ (((SRTT_BETA_BASE - SRTT_BETA) * rtt) << SRTT_SHIFT))
/ SRTT_BETA_BASE);
up(&servers->sema);
out:
return;
}
/* recalculate server weights */
void dnbd_servers_weight(dnbd_servers_t * servers)
{
int i;
int num_servers = 0;
long weightsum = 0;
long prod = 0;
long asrtt = 0;
int srtt = 0;
dnbd_server_t *server;
/*
* float arithmetics in kernel would be nice...
*/
down(&servers->sema);
for (i = 0; i < SERVERS_MAX; i++) {
server = &servers->serverlist[i];
if (server->state == SERVER_ACTIVE) {
if (server->last_tx >
server->last_rx + servers->timeout_stalled) {
printk(KERN_ERR
"dnbd: disable server #%i\n",
i + 1);
server->state = SERVER_STALLED;
continue;
}
srtt = (server->srtt ? server->srtt : 1);
weightsum += WEIGHT_FACTOR / srtt;
asrtt += srtt;
num_servers++;
}
}
if (!num_servers)
goto out;
servers->asrtt = asrtt / num_servers;
for (i = 0; i < SERVERS_MAX; i++) {
server = &servers->serverlist[i];
if (server->state == SERVER_ACTIVE) {
srtt = (server->srtt ? server->srtt : 1);
prod = srtt * weightsum;
if (prod > 0)
server->weight = WEIGHT_NORMAL * WEIGHT_FACTOR / prod;
else
server->weight = WEIGHT_NORMAL / num_servers;
}
}
out:
up(&servers->sema);
}
/* fill buffer with server statistics in human readable form for /proc */
int dnbd_show_servers(dnbd_servers_t * servers, void *buf, int size)
{
int i, n = 0;
dnbd_server_t *server;
n += snprintf(buf + n, size - n,
" timeout_min: %i jiffies\n timeout_max: %i jiffies\n",
servers->timeout_min, servers->timeout_max);
n += snprintf(buf + n, size - n, "Average SRTT: %i\n",
servers->asrtt >> SRTT_SHIFT);
for (i = 0; i < SERVERS_MAX; i++) {
server = &servers->serverlist[i];
switch (server->state) {
case SERVER_INACTIVE:
continue;
case SERVER_STALLED:
n += snprintf(buf + n, size - n,
" id: %i (stalled)\n", server->id);
continue;
default:
n += snprintf(buf + n, size - n, " id: %i\n",
server->id);
}
n += snprintf(buf + n, size - n,
" srtt: %i\n", server->srtt >> SRTT_SHIFT);
n += snprintf(buf + n, size - n,
" weight: %i (of %i)\n", server->weight,WEIGHT_NORMAL);
}
return n;
}
/* initialize servers */
int dnbd_servers_init(dnbd_servers_t * servers)
{
int i;
spin_lock_init(&servers->lock);
init_MUTEX(&servers->sema);
if (!(servers->serverlist =
(dnbd_server_t *) kmalloc(SERVERS_MAX *
sizeof(dnbd_server_t),
GFP_KERNEL)))
return -EINVAL;
for (i = 0; i < SERVERS_MAX; i++) {
servers->serverlist[i].state = 0;
}
servers->count = 0;
servers->timeout_min = TIMEOUT_MIN;
servers->timeout_max = TIMEOUT_MAX;
servers->timeout_stalled = TIMEOUT_STALLED;
return 0;
}
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