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/* 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 "internal.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));
}
/*
* Set a filesystem server cursor for using a specific FS server.
*/
int afs_set_fs_cursor(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
{
afs_init_fs_cursor(fc, vnode);
read_seqlock_excl(&vnode->cb_lock);
if (vnode->cb_interest) {
if (vnode->cb_interest->server->fs_state == 0)
fc->server = afs_get_server(vnode->cb_interest->server);
else
fc->ac.error = vnode->cb_interest->server->fs_state;
} else {
fc->ac.error = -ESTALE;
}
read_sequnlock_excl(&vnode->cb_lock);
return fc->ac.error;
}
/*
* pick a server to use to try accessing this volume
* - returns with an elevated usage count on the server chosen
*/
bool afs_volume_pick_fileserver(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
{
struct afs_volume *volume = vnode->volume;
struct afs_server *server;
int ret, state, loop;
_enter("%s", volume->vlocation->vldb.name);
/* stick with the server we're already using if we can */
if (vnode->cb_interest && vnode->cb_interest->server->fs_state == 0) {
fc->server = afs_get_server(vnode->cb_interest->server);
goto set_server;
}
down_read(&volume->server_sem);
/* handle the no-server case */
if (volume->nservers == 0) {
fc->ac.error = volume->rjservers ? -ENOMEDIUM : -ESTALE;
up_read(&volume->server_sem);
_leave(" = f [no servers %d]", fc->ac.error);
return false;
}
/* basically, just search the list for the first live server and use
* that */
ret = 0;
for (loop = 0; loop < volume->nservers; loop++) {
server = volume->servers[loop];
state = server->fs_state;
_debug("consider %d [%d]", loop, state);
switch (state) {
case 0:
goto picked_server;
case -ENETUNREACH:
if (ret == 0)
ret = state;
break;
case -EHOSTUNREACH:
if (ret == 0 ||
ret == -ENETUNREACH)
ret = state;
break;
case -ECONNREFUSED:
if (ret == 0 ||
ret == -ENETUNREACH ||
ret == -EHOSTUNREACH)
ret = state;
break;
default:
case -EREMOTEIO:
if (ret == 0 ||
ret == -ENETUNREACH ||
ret == -EHOSTUNREACH ||
ret == -ECONNREFUSED)
ret = state;
break;
}
}
error:
fc->ac.error = ret;
/* no available servers
* - TODO: handle the no active servers case better
*/
up_read(&volume->server_sem);
_leave(" = f [%d]", fc->ac.error);
return false;
picked_server:
/* Found an apparently healthy server. We need to register an interest
* in receiving callbacks before we talk to it.
*/
ret = afs_register_server_cb_interest(vnode,
&volume->cb_interests[loop], server);
if (ret < 0)
goto error;
fc->server = afs_get_server(server);
up_read(&volume->server_sem);
set_server:
fc->ac.alist = afs_get_addrlist(fc->server->addrs);
fc->ac.addr = &fc->ac.alist->addrs[0];
_debug("USING SERVER: %pIS\n", &fc->ac.addr->transport);
_leave(" = t (picked %pIS)", &fc->ac.addr->transport);
return true;
}
/*
* release a server after use
* - releases the ref on the server struct that was acquired by picking
* - records result of using a particular server to access a volume
* - return true to try again, false if okay or to issue error
* - the caller must release the server struct if result was false
*/
bool afs_iterate_fs_cursor(struct afs_fs_cursor *fc,
struct afs_vnode *vnode)
{
struct afs_volume *volume = vnode->volume;
struct afs_server *server = fc->server;
unsigned loop;
_enter("%s,%pIS,%d",
volume->vlocation->vldb.name, &fc->ac.addr->transport,
fc->ac.error);
switch (fc->ac.error) {
/* success */
case 0:
server->fs_state = 0;
_leave(" = f");
return false;
/* the fileserver denied all knowledge of the volume */
case -ENOMEDIUM:
down_write(&volume->server_sem);
/* firstly, find where the server is in the active list (if it
* is) */
for (loop = 0; loop < volume->nservers; loop++)
if (volume->servers[loop] == server)
goto present;
/* no longer there - may have been discarded by another op */
goto try_next_server_upw;
present:
volume->nservers--;
memmove(&volume->servers[loop],
&volume->servers[loop + 1],
sizeof(volume->servers[loop]) *
(volume->nservers - loop));
volume->servers[volume->nservers] = NULL;
afs_put_server(afs_v2net(vnode), server);
volume->rjservers++;
if (volume->nservers > 0)
/* another server might acknowledge its existence */
goto try_next_server_upw;
/* handle the case where all the fileservers have rejected the
* volume
* - TODO: try asking the fileservers for volume information
* - TODO: contact the VL server again to see if the volume is
* no longer registered
*/
up_write(&volume->server_sem);
afs_put_server(afs_v2net(vnode), server);
fc->server = NULL;
_leave(" = f [completely rejected]");
return false;
/* problem reaching the server */
case -ENETUNREACH:
case -EHOSTUNREACH:
case -ECONNREFUSED:
case -ETIME:
case -ETIMEDOUT:
case -EREMOTEIO:
/* mark the server as dead
* TODO: vary dead timeout depending on error
*/
spin_lock(&server->fs_lock);
if (!server->fs_state) {
server->fs_state = fc->ac.error;
printk("kAFS: SERVER DEAD state=%d\n", fc->ac.error);
}
spin_unlock(&server->fs_lock);
goto try_next_server;
/* miscellaneous error */
default:
case -ENOMEM:
case -ENONET:
/* tell the caller to accept the result */
afs_put_server(afs_v2net(vnode), server);
fc->server = NULL;
_leave(" = f [local failure]");
return false;
}
/* tell the caller to loop around and try the next server */
try_next_server_upw:
up_write(&volume->server_sem);
try_next_server:
afs_put_server(afs_v2net(vnode), server);
_leave(" = t [try next server]");
return true;
}
/*
* Clean up a fileserver cursor.
*/
int afs_end_fs_cursor(struct afs_fs_cursor *fc, struct afs_net *net)
{
afs_end_cursor(&fc->ac);
afs_put_server(net, fc->server);
return fc->ac.error;
}
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