linux/fs/afs/rotate.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

651 lines
16 KiB
C

/* Handle fileserver selection and rotation.
*
* Copyright (C) 2017 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 Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/sched/signal.h>
#include "internal.h"
#include "afs_fs.h"
/*
* Begin an operation on the fileserver.
*
* Fileserver operations are serialised on the server by vnode, so we serialise
* them here also using the io_lock.
*/
bool afs_begin_vnode_operation(struct afs_fs_cursor *fc, struct afs_vnode *vnode,
struct key *key)
{
memset(fc, 0, sizeof(*fc));
fc->vnode = vnode;
fc->key = key;
fc->ac.error = SHRT_MAX;
fc->error = -EDESTADDRREQ;
if (mutex_lock_interruptible(&vnode->io_lock) < 0) {
fc->error = -EINTR;
fc->flags |= AFS_FS_CURSOR_STOP;
return false;
}
if (vnode->lock_state != AFS_VNODE_LOCK_NONE)
fc->flags |= AFS_FS_CURSOR_CUR_ONLY;
return true;
}
/*
* Begin iteration through a server list, starting with the vnode's last used
* server if possible, or the last recorded good server if not.
*/
static bool afs_start_fs_iteration(struct afs_fs_cursor *fc,
struct afs_vnode *vnode)
{
struct afs_cb_interest *cbi;
int i;
read_lock(&vnode->volume->servers_lock);
fc->server_list = afs_get_serverlist(vnode->volume->servers);
read_unlock(&vnode->volume->servers_lock);
fc->untried = (1UL << fc->server_list->nr_servers) - 1;
fc->index = READ_ONCE(fc->server_list->preferred);
cbi = vnode->cb_interest;
if (cbi) {
/* See if the vnode's preferred record is still available */
for (i = 0; i < fc->server_list->nr_servers; i++) {
if (fc->server_list->servers[i].cb_interest == cbi) {
fc->index = i;
goto found_interest;
}
}
/* If we have a lock outstanding on a server that's no longer
* serving this vnode, then we can't switch to another server
* and have to return an error.
*/
if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
fc->error = -ESTALE;
return false;
}
/* Note that the callback promise is effectively broken */
write_seqlock(&vnode->cb_lock);
ASSERTCMP(cbi, ==, vnode->cb_interest);
vnode->cb_interest = NULL;
if (test_and_clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags))
vnode->cb_break++;
write_sequnlock(&vnode->cb_lock);
afs_put_cb_interest(afs_v2net(vnode), cbi);
cbi = NULL;
}
found_interest:
return true;
}
/*
* Post volume busy note.
*/
static void afs_busy(struct afs_volume *volume, u32 abort_code)
{
const char *m;
switch (abort_code) {
case VOFFLINE: m = "offline"; break;
case VRESTARTING: m = "restarting"; break;
case VSALVAGING: m = "being salvaged"; break;
default: m = "busy"; break;
}
pr_notice("kAFS: Volume %llu '%s' is %s\n", volume->vid, volume->name, m);
}
/*
* Sleep and retry the operation to the same fileserver.
*/
static bool afs_sleep_and_retry(struct afs_fs_cursor *fc)
{
msleep_interruptible(1000);
if (signal_pending(current)) {
fc->error = -ERESTARTSYS;
return false;
}
return true;
}
/*
* Select the fileserver to use. May be called multiple times to rotate
* through the fileservers.
*/
bool afs_select_fileserver(struct afs_fs_cursor *fc)
{
struct afs_addr_list *alist;
struct afs_server *server;
struct afs_vnode *vnode = fc->vnode;
u32 rtt, abort_code;
int error = fc->ac.error, i;
_enter("%lx[%d],%lx[%d],%d,%d",
fc->untried, fc->index,
fc->ac.tried, fc->ac.index,
error, fc->ac.abort_code);
if (fc->flags & AFS_FS_CURSOR_STOP) {
_leave(" = f [stopped]");
return false;
}
fc->nr_iterations++;
/* Evaluate the result of the previous operation, if there was one. */
switch (error) {
case SHRT_MAX:
goto start;
case 0:
default:
/* Success or local failure. Stop. */
fc->error = error;
fc->flags |= AFS_FS_CURSOR_STOP;
_leave(" = f [okay/local %d]", error);
return false;
case -ECONNABORTED:
/* The far side rejected the operation on some grounds. This
* might involve the server being busy or the volume having been moved.
*/
switch (fc->ac.abort_code) {
case VNOVOL:
/* This fileserver doesn't know about the volume.
* - May indicate that the VL is wrong - retry once and compare
* the results.
* - May indicate that the fileserver couldn't attach to the vol.
*/
if (fc->flags & AFS_FS_CURSOR_VNOVOL) {
fc->error = -EREMOTEIO;
goto next_server;
}
write_lock(&vnode->volume->servers_lock);
fc->server_list->vnovol_mask |= 1 << fc->index;
write_unlock(&vnode->volume->servers_lock);
set_bit(AFS_VOLUME_NEEDS_UPDATE, &vnode->volume->flags);
error = afs_check_volume_status(vnode->volume, fc->key);
if (error < 0)
goto failed_set_error;
if (test_bit(AFS_VOLUME_DELETED, &vnode->volume->flags)) {
fc->error = -ENOMEDIUM;
goto failed;
}
/* If the server list didn't change, then assume that
* it's the fileserver having trouble.
*/
if (vnode->volume->servers == fc->server_list) {
fc->error = -EREMOTEIO;
goto next_server;
}
/* Try again */
fc->flags |= AFS_FS_CURSOR_VNOVOL;
_leave(" = t [vnovol]");
return true;
case VSALVAGE: /* TODO: Should this return an error or iterate? */
case VVOLEXISTS:
case VNOSERVICE:
case VONLINE:
case VDISKFULL:
case VOVERQUOTA:
fc->error = afs_abort_to_error(fc->ac.abort_code);
goto next_server;
case VOFFLINE:
if (!test_and_set_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags)) {
afs_busy(vnode->volume, fc->ac.abort_code);
clear_bit(AFS_VOLUME_BUSY, &vnode->volume->flags);
}
if (fc->flags & AFS_FS_CURSOR_NO_VSLEEP) {
fc->error = -EADV;
goto failed;
}
if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
fc->error = -ESTALE;
goto failed;
}
goto busy;
case VSALVAGING:
case VRESTARTING:
case VBUSY:
/* Retry after going round all the servers unless we
* have a file lock we need to maintain.
*/
if (fc->flags & AFS_FS_CURSOR_NO_VSLEEP) {
fc->error = -EBUSY;
goto failed;
}
if (!test_and_set_bit(AFS_VOLUME_BUSY, &vnode->volume->flags)) {
afs_busy(vnode->volume, fc->ac.abort_code);
clear_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags);
}
busy:
if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
if (!afs_sleep_and_retry(fc))
goto failed;
/* Retry with same server & address */
_leave(" = t [vbusy]");
return true;
}
fc->flags |= AFS_FS_CURSOR_VBUSY;
goto next_server;
case VMOVED:
/* The volume migrated to another server. We consider
* consider all locks and callbacks broken and request
* an update from the VLDB.
*
* We also limit the number of VMOVED hops we will
* honour, just in case someone sets up a loop.
*/
if (fc->flags & AFS_FS_CURSOR_VMOVED) {
fc->error = -EREMOTEIO;
goto failed;
}
fc->flags |= AFS_FS_CURSOR_VMOVED;
set_bit(AFS_VOLUME_WAIT, &vnode->volume->flags);
set_bit(AFS_VOLUME_NEEDS_UPDATE, &vnode->volume->flags);
error = afs_check_volume_status(vnode->volume, fc->key);
if (error < 0)
goto failed_set_error;
/* If the server list didn't change, then the VLDB is
* out of sync with the fileservers. This is hopefully
* a temporary condition, however, so we don't want to
* permanently block access to the file.
*
* TODO: Try other fileservers if we can.
*
* TODO: Retry a few times with sleeps.
*/
if (vnode->volume->servers == fc->server_list) {
fc->error = -ENOMEDIUM;
goto failed;
}
goto restart_from_beginning;
default:
clear_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags);
clear_bit(AFS_VOLUME_BUSY, &vnode->volume->flags);
fc->error = afs_abort_to_error(fc->ac.abort_code);
goto failed;
}
case -ETIMEDOUT:
case -ETIME:
if (fc->error != -EDESTADDRREQ)
goto iterate_address;
/* Fall through */
case -ENETUNREACH:
case -EHOSTUNREACH:
case -ECONNREFUSED:
_debug("no conn");
fc->error = error;
goto iterate_address;
case -ECONNRESET:
_debug("call reset");
fc->error = error;
goto failed;
}
restart_from_beginning:
_debug("restart");
afs_end_cursor(&fc->ac);
afs_put_cb_interest(afs_v2net(vnode), fc->cbi);
fc->cbi = NULL;
afs_put_serverlist(afs_v2net(vnode), fc->server_list);
fc->server_list = NULL;
start:
_debug("start");
/* See if we need to do an update of the volume record. Note that the
* volume may have moved or even have been deleted.
*/
error = afs_check_volume_status(vnode->volume, fc->key);
if (error < 0)
goto failed_set_error;
if (!afs_start_fs_iteration(fc, vnode))
goto failed;
_debug("__ VOL %llx __", vnode->volume->vid);
error = afs_probe_fileservers(afs_v2net(vnode), fc->key, fc->server_list);
if (error < 0)
goto failed_set_error;
pick_server:
_debug("pick [%lx]", fc->untried);
error = afs_wait_for_fs_probes(fc->server_list, fc->untried);
if (error < 0)
goto failed_set_error;
/* Pick the untried server with the lowest RTT. If we have outstanding
* callbacks, we stick with the server we're already using if we can.
*/
if (fc->cbi) {
_debug("cbi %u", fc->index);
if (test_bit(fc->index, &fc->untried))
goto selected_server;
afs_put_cb_interest(afs_v2net(vnode), fc->cbi);
fc->cbi = NULL;
_debug("nocbi");
}
fc->index = -1;
rtt = U32_MAX;
for (i = 0; i < fc->server_list->nr_servers; i++) {
struct afs_server *s = fc->server_list->servers[i].server;
if (!test_bit(i, &fc->untried) || !s->probe.responded)
continue;
if (s->probe.rtt < rtt) {
fc->index = i;
rtt = s->probe.rtt;
}
}
if (fc->index == -1)
goto no_more_servers;
selected_server:
_debug("use %d", fc->index);
__clear_bit(fc->index, &fc->untried);
/* We're starting on a different fileserver from the list. We need to
* check it, create a callback intercept, find its address list and
* probe its capabilities before we use it.
*/
ASSERTCMP(fc->ac.alist, ==, NULL);
server = fc->server_list->servers[fc->index].server;
if (!afs_check_server_record(fc, server))
goto failed;
_debug("USING SERVER: %pU", &server->uuid);
/* Make sure we've got a callback interest record for this server. We
* have to link it in before we send the request as we can be sent a
* break request before we've finished decoding the reply and
* installing the vnode.
*/
error = afs_register_server_cb_interest(vnode, fc->server_list,
fc->index);
if (error < 0)
goto failed_set_error;
fc->cbi = afs_get_cb_interest(vnode->cb_interest);
read_lock(&server->fs_lock);
alist = rcu_dereference_protected(server->addresses,
lockdep_is_held(&server->fs_lock));
afs_get_addrlist(alist);
read_unlock(&server->fs_lock);
memset(&fc->ac, 0, sizeof(fc->ac));
if (!fc->ac.alist)
fc->ac.alist = alist;
else
afs_put_addrlist(alist);
fc->ac.index = -1;
iterate_address:
ASSERT(fc->ac.alist);
/* Iterate over the current server's address list to try and find an
* address on which it will respond to us.
*/
if (!afs_iterate_addresses(&fc->ac))
goto next_server;
_debug("address [%u] %u/%u", fc->index, fc->ac.index, fc->ac.alist->nr_addrs);
_leave(" = t");
return true;
next_server:
_debug("next");
afs_end_cursor(&fc->ac);
goto pick_server;
no_more_servers:
/* That's all the servers poked to no good effect. Try again if some
* of them were busy.
*/
if (fc->flags & AFS_FS_CURSOR_VBUSY)
goto restart_from_beginning;
abort_code = 0;
error = -EDESTADDRREQ;
for (i = 0; i < fc->server_list->nr_servers; i++) {
struct afs_server *s = fc->server_list->servers[i].server;
int probe_error = READ_ONCE(s->probe.error);
switch (probe_error) {
case 0:
continue;
default:
if (error == -ETIMEDOUT ||
error == -ETIME)
continue;
case -ETIMEDOUT:
case -ETIME:
if (error == -ENOMEM ||
error == -ENONET)
continue;
case -ENOMEM:
case -ENONET:
if (error == -ENETUNREACH)
continue;
case -ENETUNREACH:
if (error == -EHOSTUNREACH)
continue;
case -EHOSTUNREACH:
if (error == -ECONNREFUSED)
continue;
case -ECONNREFUSED:
if (error == -ECONNRESET)
continue;
case -ECONNRESET: /* Responded, but call expired. */
if (error == -ECONNABORTED)
continue;
case -ECONNABORTED:
abort_code = s->probe.abort_code;
error = probe_error;
continue;
}
}
if (error == -ECONNABORTED)
error = afs_abort_to_error(abort_code);
failed_set_error:
fc->error = error;
failed:
fc->flags |= AFS_FS_CURSOR_STOP;
afs_end_cursor(&fc->ac);
_leave(" = f [failed %d]", fc->error);
return false;
}
/*
* Select the same fileserver we used for a vnode before and only that
* fileserver. We use this when we have a lock on that file, which is backed
* only by the fileserver we obtained it from.
*/
bool afs_select_current_fileserver(struct afs_fs_cursor *fc)
{
struct afs_vnode *vnode = fc->vnode;
struct afs_cb_interest *cbi = vnode->cb_interest;
struct afs_addr_list *alist;
int error = fc->ac.error;
_enter("");
switch (error) {
case SHRT_MAX:
if (!cbi) {
fc->error = -ESTALE;
fc->flags |= AFS_FS_CURSOR_STOP;
return false;
}
fc->cbi = afs_get_cb_interest(vnode->cb_interest);
read_lock(&cbi->server->fs_lock);
alist = rcu_dereference_protected(cbi->server->addresses,
lockdep_is_held(&cbi->server->fs_lock));
afs_get_addrlist(alist);
read_unlock(&cbi->server->fs_lock);
if (!alist) {
fc->error = -ESTALE;
fc->flags |= AFS_FS_CURSOR_STOP;
return false;
}
memset(&fc->ac, 0, sizeof(fc->ac));
fc->ac.alist = alist;
fc->ac.index = -1;
goto iterate_address;
case 0:
default:
/* Success or local failure. Stop. */
fc->error = error;
fc->flags |= AFS_FS_CURSOR_STOP;
_leave(" = f [okay/local %d]", error);
return false;
case -ECONNABORTED:
fc->error = afs_abort_to_error(fc->ac.abort_code);
fc->flags |= AFS_FS_CURSOR_STOP;
_leave(" = f [abort]");
return false;
case -ENETUNREACH:
case -EHOSTUNREACH:
case -ECONNREFUSED:
case -ETIMEDOUT:
case -ETIME:
_debug("no conn");
fc->error = error;
goto iterate_address;
}
iterate_address:
/* Iterate over the current server's address list to try and find an
* address on which it will respond to us.
*/
if (afs_iterate_addresses(&fc->ac)) {
_leave(" = t");
return true;
}
afs_end_cursor(&fc->ac);
return false;
}
/*
* Dump cursor state in the case of the error being EDESTADDRREQ.
*/
static void afs_dump_edestaddrreq(const struct afs_fs_cursor *fc)
{
static int count;
int i;
if (!IS_ENABLED(CONFIG_AFS_DEBUG_CURSOR) || count > 3)
return;
count++;
rcu_read_lock();
pr_notice("EDESTADDR occurred\n");
pr_notice("FC: cbb=%x cbb2=%x fl=%hx err=%hd\n",
fc->cb_break, fc->cb_break_2, fc->flags, fc->error);
pr_notice("FC: ut=%lx ix=%d ni=%u\n",
fc->untried, fc->index, fc->nr_iterations);
if (fc->server_list) {
const struct afs_server_list *sl = fc->server_list;
pr_notice("FC: SL nr=%u pr=%u vnov=%hx\n",
sl->nr_servers, sl->preferred, sl->vnovol_mask);
for (i = 0; i < sl->nr_servers; i++) {
const struct afs_server *s = sl->servers[i].server;
pr_notice("FC: server fl=%lx av=%u %pU\n",
s->flags, s->addr_version, &s->uuid);
if (s->addresses) {
const struct afs_addr_list *a =
rcu_dereference(s->addresses);
pr_notice("FC: - av=%u nr=%u/%u/%u pr=%u\n",
a->version,
a->nr_ipv4, a->nr_addrs, a->max_addrs,
a->preferred);
pr_notice("FC: - pr=%lx R=%lx F=%lx\n",
a->probed, a->responded, a->failed);
if (a == fc->ac.alist)
pr_notice("FC: - current\n");
}
}
}
pr_notice("AC: t=%lx ax=%u ac=%d er=%d r=%u ni=%u\n",
fc->ac.tried, fc->ac.index, fc->ac.abort_code, fc->ac.error,
fc->ac.responded, fc->ac.nr_iterations);
rcu_read_unlock();
}
/*
* Tidy up a filesystem cursor and unlock the vnode.
*/
int afs_end_vnode_operation(struct afs_fs_cursor *fc)
{
struct afs_net *net = afs_v2net(fc->vnode);
if (fc->error == -EDESTADDRREQ ||
fc->error == -ENETUNREACH ||
fc->error == -EHOSTUNREACH)
afs_dump_edestaddrreq(fc);
mutex_unlock(&fc->vnode->io_lock);
afs_end_cursor(&fc->ac);
afs_put_cb_interest(net, fc->cbi);
afs_put_serverlist(net, fc->server_list);
if (fc->error == -ECONNABORTED)
fc->error = afs_abort_to_error(fc->ac.abort_code);
return fc->error;
}