linux/fs/afs/server.c
David Howells 20b8391fff afs: Make some RPC operations non-interruptible
Make certain RPC operations non-interruptible, including:

 (*) Set attributes
 (*) Store data

     We don't want to get interrupted during a flush on close, flush on
     unlock, writeback or an inode update, leaving us in a state where we
     still need to do the writeback or update.

 (*) Extend lock
 (*) Release lock

     We don't want to get lock extension interrupted as the file locks on
     the server are time-limited.  Interruption during lock release is less
     of an issue since the lock is time-limited, but it's better to
     complete the release to avoid a several-minute wait to recover it.

     *Setting* the lock isn't a problem if it's interrupted since we can
      just return to the user and tell them they were interrupted - at
      which point they can elect to retry.

 (*) Silly unlink

     We want to remove silly unlink files if we can, rather than leaving
     them for the salvager to clear up.

Note that whilst these calls are no longer interruptible, they do have
timeouts on them, so if the server stops responding the call will fail with
something like ETIME or ECONNRESET.

Without this, the following:

	kAFS: Unexpected error from FS.StoreData -512

appears in dmesg when a pending store data gets interrupted and some
processes may just hang.

Additionally, make the code that checks/updates the server record ignore
failure due to interruption if the main call is uninterruptible and if the
server has an address list.  The next op will check it again since the
expiration time on the old list has past.

Fixes: d2ddc776a4 ("afs: Overhaul volume and server record caching and fileserver rotation")
Reported-by: Jonathan Billings <jsbillings@jsbillings.org>
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
2019-05-16 16:25:20 +01:00

601 lines
15 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->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)) {
if ((PTR_ERR(alist) == -ERESTARTSYS ||
PTR_ERR(alist) == -EINTR) &&
!(fc->flags & AFS_FS_CURSOR_INTR) &&
server->addresses) {
_leave(" = t [intr]");
return true;
}
fc->error = PTR_ERR(alist);
_leave(" = f [%d]", fc->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) {
if (!(fc->flags & AFS_FS_CURSOR_INTR) && server->addresses) {
_leave(" = t [intr]");
return true;
}
fc->error = ret;
_leave(" = f [intr]");
return false;
}
retries++;
if (retries == 4) {
_leave(" = f [stale]");
ret = -ESTALE;
return false;
}
goto retry;
}