linux/fs/afs/rotate.c
David Howells 16280a15be afs: Rearrange afs_select_fileserver() a little
Rearrange afs_select_fileserver() a little to put the use_server chunk
before the next_server chunk so that with the removal of a couple of gotos
the main path through the function is all one sequence.

Signed-off-by: David Howells <dhowells@redhat.com>
2018-02-06 14:43:37 +00:00

517 lines
13 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"
/*
* Initialise a filesystem server cursor for iterating over FS servers.
*/
void afs_init_fs_cursor(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
{
memset(fc, 0, sizeof(*fc));
}
/*
* 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)
{
afs_init_fs_cursor(fc, vnode);
fc->vnode = vnode;
fc->key = key;
fc->ac.error = SHRT_MAX;
if (mutex_lock_interruptible(&vnode->io_lock) < 0) {
fc->ac.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);
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->start = 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->ac.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;
} else {
fc->start = READ_ONCE(fc->server_list->index);
}
found_interest:
fc->index = fc->start;
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 %u '%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->ac.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;
_enter("%u/%u,%u/%u,%d,%d",
fc->index, fc->start,
fc->ac.index, fc->ac.start,
fc->ac.error, fc->ac.abort_code);
if (fc->flags & AFS_FS_CURSOR_STOP) {
_leave(" = f [stopped]");
return false;
}
/* Evaluate the result of the previous operation, if there was one. */
switch (fc->ac.error) {
case SHRT_MAX:
goto start;
case 0:
default:
/* Success or local failure. Stop. */
fc->flags |= AFS_FS_CURSOR_STOP;
_leave(" = f [okay/local %d]", fc->ac.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->ac.error = -EREMOTEIO;
goto failed;
}
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);
fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
if (fc->ac.error < 0)
goto failed;
if (test_bit(AFS_VOLUME_DELETED, &vnode->volume->flags)) {
fc->ac.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->ac.error = -EREMOTEIO;
goto failed;
}
/* 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->ac.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->ac.error = -EADV;
goto failed;
}
if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
fc->ac.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->ac.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->ac.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);
fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
if (fc->ac.error < 0)
goto failed;
/* 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->ac.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->ac.error = afs_abort_to_error(fc->ac.abort_code);
goto failed;
}
case -ENETUNREACH:
case -EHOSTUNREACH:
case -ECONNREFUSED:
case -ETIMEDOUT:
case -ETIME:
_debug("no conn");
goto iterate_address;
}
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.
*/
fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
if (fc->ac.error < 0)
goto failed;
if (!afs_start_fs_iteration(fc, vnode))
goto failed;
use_server:
_debug("use");
/* 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.
*/
fc->ac.error = afs_register_server_cb_interest(
vnode, &fc->server_list->servers[fc->index]);
if (fc->ac.error < 0)
goto failed;
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));
/* Probe the current fileserver if we haven't done so yet. */
if (!test_bit(AFS_SERVER_FL_PROBED, &server->flags)) {
fc->ac.alist = afs_get_addrlist(alist);
if (!afs_probe_fileserver(fc))
goto failed;
}
if (!fc->ac.alist)
fc->ac.alist = alist;
else
afs_put_addrlist(alist);
fc->ac.start = READ_ONCE(alist->index);
fc->ac.index = fc->ac.start;
iterate_address:
ASSERT(fc->ac.alist);
_debug("iterate %d/%d", fc->ac.index, fc->ac.alist->nr_addrs);
/* 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;
_leave(" = t");
return true;
next_server:
_debug("next");
afs_end_cursor(&fc->ac);
afs_put_cb_interest(afs_v2net(vnode), fc->cbi);
fc->cbi = NULL;
fc->index++;
if (fc->index >= fc->server_list->nr_servers)
fc->index = 0;
if (fc->index != fc->start)
goto use_server;
/* 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;
fc->ac.error = -EDESTADDRREQ;
goto failed;
failed:
fc->flags |= AFS_FS_CURSOR_STOP;
afs_end_cursor(&fc->ac);
_leave(" = f [failed %d]", fc->ac.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;
_enter("");
switch (fc->ac.error) {
case SHRT_MAX:
if (!cbi) {
fc->ac.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->ac.error = -ESTALE;
fc->flags |= AFS_FS_CURSOR_STOP;
return false;
}
memset(&fc->ac, 0, sizeof(fc->ac));
fc->ac.alist = alist;
fc->ac.start = READ_ONCE(alist->index);
fc->ac.index = fc->ac.start;
goto iterate_address;
case 0:
default:
/* Success or local failure. Stop. */
fc->flags |= AFS_FS_CURSOR_STOP;
_leave(" = f [okay/local %d]", fc->ac.error);
return false;
case -ECONNABORTED:
fc->flags |= AFS_FS_CURSOR_STOP;
_leave(" = f [abort]");
return false;
case -ENETUNREACH:
case -EHOSTUNREACH:
case -ECONNREFUSED:
case -ETIMEDOUT:
case -ETIME:
_debug("no conn");
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;
}
/*
* 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);
int ret;
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);
ret = fc->ac.error;
if (ret == -ECONNABORTED)
afs_abort_to_error(fc->ac.abort_code);
return fc->ac.error;
}