linux-stable/fs/afs/server.c
David Howells 3bf0fb6f33 afs: Probe multiple fileservers simultaneously
Send probes to all the unprobed fileservers in a fileserver list on all
addresses simultaneously in an attempt to find out the fastest route whilst
not getting stuck for 20s on any server or address that we don't get a
reply from.

This alleviates the problem whereby attempting to access a new server can
take a long time because the rotation algorithm ends up rotating through
all servers and addresses until it finds one that responds.

Signed-off-by: David Howells <dhowells@redhat.com>
2018-10-24 00:41:09 +01:00

590 lines
14 KiB
C

/* AFS server record management
*
* Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/sched.h>
#include <linux/slab.h>
#include "afs_fs.h"
#include "internal.h"
#include "protocol_yfs.h"
static unsigned afs_server_gc_delay = 10; /* Server record timeout in seconds */
static unsigned afs_server_update_delay = 30; /* Time till VLDB recheck in secs */
static void afs_inc_servers_outstanding(struct afs_net *net)
{
atomic_inc(&net->servers_outstanding);
}
static void afs_dec_servers_outstanding(struct afs_net *net)
{
if (atomic_dec_and_test(&net->servers_outstanding))
wake_up_var(&net->servers_outstanding);
}
/*
* Find a server by one of its addresses.
*/
struct afs_server *afs_find_server(struct afs_net *net,
const struct sockaddr_rxrpc *srx)
{
const struct sockaddr_in6 *a = &srx->transport.sin6, *b;
const struct afs_addr_list *alist;
struct afs_server *server = NULL;
unsigned int i;
bool ipv6 = true;
int seq = 0, diff;
if (srx->transport.sin6.sin6_addr.s6_addr32[0] == 0 ||
srx->transport.sin6.sin6_addr.s6_addr32[1] == 0 ||
srx->transport.sin6.sin6_addr.s6_addr32[2] == htonl(0xffff))
ipv6 = false;
rcu_read_lock();
do {
if (server)
afs_put_server(net, server);
server = NULL;
read_seqbegin_or_lock(&net->fs_addr_lock, &seq);
if (ipv6) {
hlist_for_each_entry_rcu(server, &net->fs_addresses6, addr6_link) {
alist = rcu_dereference(server->addresses);
for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
b = &alist->addrs[i].transport.sin6;
diff = ((u16 __force)a->sin6_port -
(u16 __force)b->sin6_port);
if (diff == 0)
diff = memcmp(&a->sin6_addr,
&b->sin6_addr,
sizeof(struct in6_addr));
if (diff == 0)
goto found;
}
}
} else {
hlist_for_each_entry_rcu(server, &net->fs_addresses4, addr4_link) {
alist = rcu_dereference(server->addresses);
for (i = 0; i < alist->nr_ipv4; i++) {
b = &alist->addrs[i].transport.sin6;
diff = ((u16 __force)a->sin6_port -
(u16 __force)b->sin6_port);
if (diff == 0)
diff = ((u32 __force)a->sin6_addr.s6_addr32[3] -
(u32 __force)b->sin6_addr.s6_addr32[3]);
if (diff == 0)
goto found;
}
}
}
server = NULL;
found:
if (server && !atomic_inc_not_zero(&server->usage))
server = NULL;
} while (need_seqretry(&net->fs_addr_lock, seq));
done_seqretry(&net->fs_addr_lock, seq);
rcu_read_unlock();
return server;
}
/*
* Look up a server by its UUID
*/
struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uuid)
{
struct afs_server *server = NULL;
struct rb_node *p;
int diff, seq = 0;
_enter("%pU", uuid);
do {
/* Unfortunately, rbtree walking doesn't give reliable results
* under just the RCU read lock, so we have to check for
* changes.
*/
if (server)
afs_put_server(net, server);
server = NULL;
read_seqbegin_or_lock(&net->fs_lock, &seq);
p = net->fs_servers.rb_node;
while (p) {
server = rb_entry(p, struct afs_server, uuid_rb);
diff = memcmp(uuid, &server->uuid, sizeof(*uuid));
if (diff < 0) {
p = p->rb_left;
} else if (diff > 0) {
p = p->rb_right;
} else {
afs_get_server(server);
break;
}
server = NULL;
}
} while (need_seqretry(&net->fs_lock, seq));
done_seqretry(&net->fs_lock, seq);
_leave(" = %p", server);
return server;
}
/*
* Install a server record in the namespace tree
*/
static struct afs_server *afs_install_server(struct afs_net *net,
struct afs_server *candidate)
{
const struct afs_addr_list *alist;
struct afs_server *server;
struct rb_node **pp, *p;
int ret = -EEXIST, diff;
_enter("%p", candidate);
write_seqlock(&net->fs_lock);
/* Firstly install the server in the UUID lookup tree */
pp = &net->fs_servers.rb_node;
p = NULL;
while (*pp) {
p = *pp;
_debug("- consider %p", p);
server = rb_entry(p, struct afs_server, uuid_rb);
diff = memcmp(&candidate->uuid, &server->uuid, sizeof(uuid_t));
if (diff < 0)
pp = &(*pp)->rb_left;
else if (diff > 0)
pp = &(*pp)->rb_right;
else
goto exists;
}
server = candidate;
rb_link_node(&server->uuid_rb, p, pp);
rb_insert_color(&server->uuid_rb, &net->fs_servers);
hlist_add_head_rcu(&server->proc_link, &net->fs_proc);
write_seqlock(&net->fs_addr_lock);
alist = rcu_dereference_protected(server->addresses,
lockdep_is_held(&net->fs_addr_lock.lock));
/* Secondly, if the server has any IPv4 and/or IPv6 addresses, install
* it in the IPv4 and/or IPv6 reverse-map lists.
*
* TODO: For speed we want to use something other than a flat list
* here; even sorting the list in terms of lowest address would help a
* bit, but anything we might want to do gets messy and memory
* intensive.
*/
if (alist->nr_ipv4 > 0)
hlist_add_head_rcu(&server->addr4_link, &net->fs_addresses4);
if (alist->nr_addrs > alist->nr_ipv4)
hlist_add_head_rcu(&server->addr6_link, &net->fs_addresses6);
write_sequnlock(&net->fs_addr_lock);
ret = 0;
exists:
afs_get_server(server);
write_sequnlock(&net->fs_lock);
return server;
}
/*
* allocate a new server record
*/
static struct afs_server *afs_alloc_server(struct afs_net *net,
const uuid_t *uuid,
struct afs_addr_list *alist)
{
struct afs_server *server;
_enter("");
server = kzalloc(sizeof(struct afs_server), GFP_KERNEL);
if (!server)
goto enomem;
atomic_set(&server->usage, 1);
RCU_INIT_POINTER(server->addresses, alist);
server->addr_version = alist->version;
server->uuid = *uuid;
server->flags = (1UL << AFS_SERVER_FL_NEW);
server->update_at = ktime_get_real_seconds() + afs_server_update_delay;
rwlock_init(&server->fs_lock);
INIT_HLIST_HEAD(&server->cb_volumes);
rwlock_init(&server->cb_break_lock);
init_waitqueue_head(&server->probe_wq);
spin_lock_init(&server->probe_lock);
afs_inc_servers_outstanding(net);
_leave(" = %p", server);
return server;
enomem:
_leave(" = NULL [nomem]");
return NULL;
}
/*
* Look up an address record for a server
*/
static struct afs_addr_list *afs_vl_lookup_addrs(struct afs_cell *cell,
struct key *key, const uuid_t *uuid)
{
struct afs_vl_cursor vc;
struct afs_addr_list *alist = NULL;
int ret;
ret = -ERESTARTSYS;
if (afs_begin_vlserver_operation(&vc, cell, key)) {
while (afs_select_vlserver(&vc)) {
if (test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags))
alist = afs_yfsvl_get_endpoints(&vc, uuid);
else
alist = afs_vl_get_addrs_u(&vc, uuid);
}
ret = afs_end_vlserver_operation(&vc);
}
return ret < 0 ? ERR_PTR(ret) : alist;
}
/*
* Get or create a fileserver record.
*/
struct afs_server *afs_lookup_server(struct afs_cell *cell, struct key *key,
const uuid_t *uuid)
{
struct afs_addr_list *alist;
struct afs_server *server, *candidate;
_enter("%p,%pU", cell->net, uuid);
server = afs_find_server_by_uuid(cell->net, uuid);
if (server)
return server;
alist = afs_vl_lookup_addrs(cell, key, uuid);
if (IS_ERR(alist))
return ERR_CAST(alist);
candidate = afs_alloc_server(cell->net, uuid, alist);
if (!candidate) {
afs_put_addrlist(alist);
return ERR_PTR(-ENOMEM);
}
server = afs_install_server(cell->net, candidate);
if (server != candidate) {
afs_put_addrlist(alist);
kfree(candidate);
}
_leave(" = %p{%d}", server, atomic_read(&server->usage));
return server;
}
/*
* Set the server timer to fire after a given delay, assuming it's not already
* set for an earlier time.
*/
static void afs_set_server_timer(struct afs_net *net, time64_t delay)
{
if (net->live) {
afs_inc_servers_outstanding(net);
if (timer_reduce(&net->fs_timer, jiffies + delay * HZ))
afs_dec_servers_outstanding(net);
}
}
/*
* Server management timer. We have an increment on fs_outstanding that we
* need to pass along to the work item.
*/
void afs_servers_timer(struct timer_list *timer)
{
struct afs_net *net = container_of(timer, struct afs_net, fs_timer);
_enter("");
if (!queue_work(afs_wq, &net->fs_manager))
afs_dec_servers_outstanding(net);
}
/*
* Release a reference on a server record.
*/
void afs_put_server(struct afs_net *net, struct afs_server *server)
{
unsigned int usage;
if (!server)
return;
server->put_time = ktime_get_real_seconds();
usage = atomic_dec_return(&server->usage);
_enter("{%u}", usage);
if (likely(usage > 0))
return;
afs_set_server_timer(net, afs_server_gc_delay);
}
static void afs_server_rcu(struct rcu_head *rcu)
{
struct afs_server *server = container_of(rcu, struct afs_server, rcu);
afs_put_addrlist(rcu_access_pointer(server->addresses));
kfree(server);
}
/*
* destroy a dead server
*/
static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
{
struct afs_addr_list *alist = rcu_access_pointer(server->addresses);
struct afs_addr_cursor ac = {
.alist = alist,
.index = alist->preferred,
.error = 0,
};
_enter("%p", server);
if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
afs_fs_give_up_all_callbacks(net, server, &ac, NULL);
wait_var_event(&server->probe_outstanding,
atomic_read(&server->probe_outstanding) == 0);
call_rcu(&server->rcu, afs_server_rcu);
afs_dec_servers_outstanding(net);
}
/*
* Garbage collect any expired servers.
*/
static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
{
struct afs_server *server;
bool deleted;
int usage;
while ((server = gc_list)) {
gc_list = server->gc_next;
write_seqlock(&net->fs_lock);
usage = 1;
deleted = atomic_try_cmpxchg(&server->usage, &usage, 0);
if (deleted) {
rb_erase(&server->uuid_rb, &net->fs_servers);
hlist_del_rcu(&server->proc_link);
}
write_sequnlock(&net->fs_lock);
if (deleted) {
write_seqlock(&net->fs_addr_lock);
if (!hlist_unhashed(&server->addr4_link))
hlist_del_rcu(&server->addr4_link);
if (!hlist_unhashed(&server->addr6_link))
hlist_del_rcu(&server->addr6_link);
write_sequnlock(&net->fs_addr_lock);
afs_destroy_server(net, server);
}
}
}
/*
* Manage the records of servers known to be within a network namespace. This
* includes garbage collecting unused servers.
*
* Note also that we were given an increment on net->servers_outstanding by
* whoever queued us that we need to deal with before returning.
*/
void afs_manage_servers(struct work_struct *work)
{
struct afs_net *net = container_of(work, struct afs_net, fs_manager);
struct afs_server *gc_list = NULL;
struct rb_node *cursor;
time64_t now = ktime_get_real_seconds(), next_manage = TIME64_MAX;
bool purging = !net->live;
_enter("");
/* Trawl the server list looking for servers that have expired from
* lack of use.
*/
read_seqlock_excl(&net->fs_lock);
for (cursor = rb_first(&net->fs_servers); cursor; cursor = rb_next(cursor)) {
struct afs_server *server =
rb_entry(cursor, struct afs_server, uuid_rb);
int usage = atomic_read(&server->usage);
_debug("manage %pU %u", &server->uuid, usage);
ASSERTCMP(usage, >=, 1);
ASSERTIFCMP(purging, usage, ==, 1);
if (usage == 1) {
time64_t expire_at = server->put_time;
if (!test_bit(AFS_SERVER_FL_VL_FAIL, &server->flags) &&
!test_bit(AFS_SERVER_FL_NOT_FOUND, &server->flags))
expire_at += afs_server_gc_delay;
if (purging || expire_at <= now) {
server->gc_next = gc_list;
gc_list = server;
} else if (expire_at < next_manage) {
next_manage = expire_at;
}
}
}
read_sequnlock_excl(&net->fs_lock);
/* Update the timer on the way out. We have to pass an increment on
* servers_outstanding in the namespace that we are in to the timer or
* the work scheduler.
*/
if (!purging && next_manage < TIME64_MAX) {
now = ktime_get_real_seconds();
if (next_manage - now <= 0) {
if (queue_work(afs_wq, &net->fs_manager))
afs_inc_servers_outstanding(net);
} else {
afs_set_server_timer(net, next_manage - now);
}
}
afs_gc_servers(net, gc_list);
afs_dec_servers_outstanding(net);
_leave(" [%d]", atomic_read(&net->servers_outstanding));
}
static void afs_queue_server_manager(struct afs_net *net)
{
afs_inc_servers_outstanding(net);
if (!queue_work(afs_wq, &net->fs_manager))
afs_dec_servers_outstanding(net);
}
/*
* Purge list of servers.
*/
void afs_purge_servers(struct afs_net *net)
{
_enter("");
if (del_timer_sync(&net->fs_timer))
atomic_dec(&net->servers_outstanding);
afs_queue_server_manager(net);
_debug("wait");
wait_var_event(&net->servers_outstanding,
!atomic_read(&net->servers_outstanding));
_leave("");
}
/*
* Get an update for a server's address list.
*/
static noinline bool afs_update_server_record(struct afs_fs_cursor *fc, struct afs_server *server)
{
struct afs_addr_list *alist, *discard;
_enter("");
alist = afs_vl_lookup_addrs(fc->vnode->volume->cell, fc->key,
&server->uuid);
if (IS_ERR(alist)) {
fc->ac.error = PTR_ERR(alist);
_leave(" = f [%d]", fc->ac.error);
return false;
}
discard = alist;
if (server->addr_version != alist->version) {
write_lock(&server->fs_lock);
discard = rcu_dereference_protected(server->addresses,
lockdep_is_held(&server->fs_lock));
rcu_assign_pointer(server->addresses, alist);
server->addr_version = alist->version;
write_unlock(&server->fs_lock);
}
server->update_at = ktime_get_real_seconds() + afs_server_update_delay;
afs_put_addrlist(discard);
_leave(" = t");
return true;
}
/*
* See if a server's address list needs updating.
*/
bool afs_check_server_record(struct afs_fs_cursor *fc, struct afs_server *server)
{
time64_t now = ktime_get_real_seconds();
long diff;
bool success;
int ret, retries = 0;
_enter("");
ASSERT(server);
retry:
diff = READ_ONCE(server->update_at) - now;
if (diff > 0) {
_leave(" = t [not now %ld]", diff);
return true;
}
if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) {
success = afs_update_server_record(fc, server);
clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags);
wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING);
_leave(" = %d", success);
return success;
}
ret = wait_on_bit(&server->flags, AFS_SERVER_FL_UPDATING,
TASK_INTERRUPTIBLE);
if (ret == -ERESTARTSYS) {
fc->ac.error = ret;
_leave(" = f [intr]");
return false;
}
retries++;
if (retries == 4) {
_leave(" = f [stale]");
ret = -ESTALE;
return false;
}
goto retry;
}