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>
This commit is contained in:
David Howells
270
fs/afs/fs_probe.c
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270
fs/afs/fs_probe.c
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/* AFS fileserver probing
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*
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* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include "afs_fs.h"
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#include "internal.h"
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#include "protocol_yfs.h"
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static bool afs_fs_probe_done(struct afs_server *server)
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{
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if (!atomic_dec_and_test(&server->probe_outstanding))
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return false;
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wake_up_var(&server->probe_outstanding);
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clear_bit_unlock(AFS_SERVER_FL_PROBING, &server->flags);
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wake_up_bit(&server->flags, AFS_SERVER_FL_PROBING);
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return true;
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}
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/*
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* Process the result of probing a fileserver. This is called after successful
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* or failed delivery of an FS.GetCapabilities operation.
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*/
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void afs_fileserver_probe_result(struct afs_call *call)
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{
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struct afs_addr_list *alist = call->alist;
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struct afs_server *server = call->reply[0];
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unsigned int server_index = (long)call->reply[1];
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unsigned int index = call->addr_ix;
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unsigned int rtt = UINT_MAX;
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bool have_result = false;
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u64 _rtt;
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int ret = call->error;
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_enter("%pU,%u", &server->uuid, index);
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spin_lock(&server->probe_lock);
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switch (ret) {
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case 0:
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server->probe.error = 0;
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goto responded;
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case -ECONNABORTED:
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if (!server->probe.responded) {
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server->probe.abort_code = call->abort_code;
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server->probe.error = ret;
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}
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goto responded;
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case -ENOMEM:
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case -ENONET:
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server->probe.local_failure = true;
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afs_io_error(call, afs_io_error_fs_probe_fail);
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goto out;
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case -ECONNRESET: /* Responded, but call expired. */
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case -ENETUNREACH:
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case -EHOSTUNREACH:
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case -ECONNREFUSED:
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case -ETIMEDOUT:
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case -ETIME:
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default:
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clear_bit(index, &alist->responded);
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set_bit(index, &alist->failed);
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if (!server->probe.responded &&
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(server->probe.error == 0 ||
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server->probe.error == -ETIMEDOUT ||
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server->probe.error == -ETIME))
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server->probe.error = ret;
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afs_io_error(call, afs_io_error_fs_probe_fail);
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goto out;
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}
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responded:
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set_bit(index, &alist->responded);
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clear_bit(index, &alist->failed);
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if (call->service_id == YFS_FS_SERVICE) {
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server->probe.is_yfs = true;
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set_bit(AFS_SERVER_FL_IS_YFS, &server->flags);
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alist->addrs[index].srx_service = call->service_id;
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} else {
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server->probe.not_yfs = true;
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if (!server->probe.is_yfs) {
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clear_bit(AFS_SERVER_FL_IS_YFS, &server->flags);
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alist->addrs[index].srx_service = call->service_id;
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}
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}
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/* Get the RTT and scale it to fit into a 32-bit value that represents
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* over a minute of time so that we can access it with one instruction
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* on a 32-bit system.
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*/
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_rtt = rxrpc_kernel_get_rtt(call->net->socket, call->rxcall);
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_rtt /= 64;
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rtt = (_rtt > UINT_MAX) ? UINT_MAX : _rtt;
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if (rtt < server->probe.rtt) {
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server->probe.rtt = rtt;
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alist->preferred = index;
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have_result = true;
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}
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smp_wmb(); /* Set rtt before responded. */
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server->probe.responded = true;
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set_bit(AFS_SERVER_FL_PROBED, &server->flags);
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out:
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spin_unlock(&server->probe_lock);
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_debug("probe [%u][%u] %pISpc rtt=%u ret=%d",
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server_index, index, &alist->addrs[index].transport,
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(unsigned int)rtt, ret);
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have_result |= afs_fs_probe_done(server);
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if (have_result) {
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server->probe.have_result = true;
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wake_up_var(&server->probe.have_result);
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wake_up_all(&server->probe_wq);
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}
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}
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/*
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* Probe all of a fileserver's addresses to find out the best route and to
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* query its capabilities.
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*/
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static int afs_do_probe_fileserver(struct afs_net *net,
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struct afs_server *server,
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struct key *key,
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unsigned int server_index)
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{
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struct afs_addr_cursor ac = {
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.index = 0,
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};
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int ret;
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_enter("%pU", &server->uuid);
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read_lock(&server->fs_lock);
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ac.alist = rcu_dereference_protected(server->addresses,
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lockdep_is_held(&server->fs_lock));
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read_unlock(&server->fs_lock);
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atomic_set(&server->probe_outstanding, ac.alist->nr_addrs);
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memset(&server->probe, 0, sizeof(server->probe));
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server->probe.rtt = UINT_MAX;
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for (ac.index = 0; ac.index < ac.alist->nr_addrs; ac.index++) {
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ret = afs_fs_get_capabilities(net, server, &ac, key, server_index,
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true);
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if (ret != -EINPROGRESS) {
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afs_fs_probe_done(server);
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return ret;
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}
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}
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return 0;
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}
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/*
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* Send off probes to all unprobed servers.
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*/
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int afs_probe_fileservers(struct afs_net *net, struct key *key,
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struct afs_server_list *list)
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{
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struct afs_server *server;
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int i, ret;
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for (i = 0; i < list->nr_servers; i++) {
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server = list->servers[i].server;
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if (test_bit(AFS_SERVER_FL_PROBED, &server->flags))
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continue;
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if (!test_and_set_bit_lock(AFS_SERVER_FL_PROBING, &server->flags)) {
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ret = afs_do_probe_fileserver(net, server, key, i);
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if (ret)
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return ret;
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}
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}
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return 0;
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}
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/*
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* Wait for the first as-yet untried fileserver to respond.
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*/
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int afs_wait_for_fs_probes(struct afs_server_list *slist, unsigned long untried)
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{
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struct wait_queue_entry *waits;
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struct afs_server *server;
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unsigned int rtt = UINT_MAX;
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bool have_responders = false;
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int pref = -1, i;
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_enter("%u,%lx", slist->nr_servers, untried);
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/* Only wait for servers that have a probe outstanding. */
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for (i = 0; i < slist->nr_servers; i++) {
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if (test_bit(i, &untried)) {
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server = slist->servers[i].server;
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if (!test_bit(AFS_SERVER_FL_PROBING, &server->flags))
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__clear_bit(i, &untried);
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if (server->probe.responded)
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have_responders = true;
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}
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}
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if (have_responders || !untried)
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return 0;
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waits = kmalloc(array_size(slist->nr_servers, sizeof(*waits)), GFP_KERNEL);
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if (!waits)
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return -ENOMEM;
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for (i = 0; i < slist->nr_servers; i++) {
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if (test_bit(i, &untried)) {
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server = slist->servers[i].server;
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init_waitqueue_entry(&waits[i], current);
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add_wait_queue(&server->probe_wq, &waits[i]);
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}
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}
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for (;;) {
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bool still_probing = false;
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set_current_state(TASK_INTERRUPTIBLE);
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for (i = 0; i < slist->nr_servers; i++) {
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if (test_bit(i, &untried)) {
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server = slist->servers[i].server;
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if (server->probe.responded)
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goto stop;
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if (test_bit(AFS_SERVER_FL_PROBING, &server->flags))
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still_probing = true;
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}
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}
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if (!still_probing || unlikely(signal_pending(current)))
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goto stop;
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schedule();
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}
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stop:
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set_current_state(TASK_RUNNING);
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for (i = 0; i < slist->nr_servers; i++) {
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if (test_bit(i, &untried)) {
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server = slist->servers[i].server;
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if (server->probe.responded &&
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server->probe.rtt < rtt) {
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pref = i;
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rtt = server->probe.rtt;
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}
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remove_wait_queue(&server->probe_wq, &waits[i]);
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}
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}
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kfree(waits);
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if (pref == -1 && signal_pending(current))
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return -ERESTARTSYS;
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if (pref >= 0)
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slist->preferred = pref;
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return 0;
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}
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