From 3bf0fb6f33dd545693da5e65f5b1b9b9f0bfc35e Mon Sep 17 00:00:00 2001 From: David Howells Date: Sat, 20 Oct 2018 00:57:59 +0100 Subject: 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 --- fs/afs/fs_probe.c | 270 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 270 insertions(+) create mode 100644 fs/afs/fs_probe.c (limited to 'fs/afs/fs_probe.c') diff --git a/fs/afs/fs_probe.c b/fs/afs/fs_probe.c new file mode 100644 index 000000000000..d049cb459742 --- /dev/null +++ b/fs/afs/fs_probe.c @@ -0,0 +1,270 @@ +/* AFS fileserver probing + * + * Copyright (C) 2018 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 +#include +#include "afs_fs.h" +#include "internal.h" +#include "protocol_yfs.h" + +static bool afs_fs_probe_done(struct afs_server *server) +{ + if (!atomic_dec_and_test(&server->probe_outstanding)) + return false; + + wake_up_var(&server->probe_outstanding); + clear_bit_unlock(AFS_SERVER_FL_PROBING, &server->flags); + wake_up_bit(&server->flags, AFS_SERVER_FL_PROBING); + return true; +} + +/* + * Process the result of probing a fileserver. This is called after successful + * or failed delivery of an FS.GetCapabilities operation. + */ +void afs_fileserver_probe_result(struct afs_call *call) +{ + struct afs_addr_list *alist = call->alist; + struct afs_server *server = call->reply[0]; + unsigned int server_index = (long)call->reply[1]; + unsigned int index = call->addr_ix; + unsigned int rtt = UINT_MAX; + bool have_result = false; + u64 _rtt; + int ret = call->error; + + _enter("%pU,%u", &server->uuid, index); + + spin_lock(&server->probe_lock); + + switch (ret) { + case 0: + server->probe.error = 0; + goto responded; + case -ECONNABORTED: + if (!server->probe.responded) { + server->probe.abort_code = call->abort_code; + server->probe.error = ret; + } + goto responded; + case -ENOMEM: + case -ENONET: + server->probe.local_failure = true; + afs_io_error(call, afs_io_error_fs_probe_fail); + goto out; + case -ECONNRESET: /* Responded, but call expired. */ + case -ENETUNREACH: + case -EHOSTUNREACH: + case -ECONNREFUSED: + case -ETIMEDOUT: + case -ETIME: + default: + clear_bit(index, &alist->responded); + set_bit(index, &alist->failed); + if (!server->probe.responded && + (server->probe.error == 0 || + server->probe.error == -ETIMEDOUT || + server->probe.error == -ETIME)) + server->probe.error = ret; + afs_io_error(call, afs_io_error_fs_probe_fail); + goto out; + } + +responded: + set_bit(index, &alist->responded); + clear_bit(index, &alist->failed); + + if (call->service_id == YFS_FS_SERVICE) { + server->probe.is_yfs = true; + set_bit(AFS_SERVER_FL_IS_YFS, &server->flags); + alist->addrs[index].srx_service = call->service_id; + } else { + server->probe.not_yfs = true; + if (!server->probe.is_yfs) { + clear_bit(AFS_SERVER_FL_IS_YFS, &server->flags); + alist->addrs[index].srx_service = call->service_id; + } + } + + /* Get the RTT and scale it to fit into a 32-bit value that represents + * over a minute of time so that we can access it with one instruction + * on a 32-bit system. + */ + _rtt = rxrpc_kernel_get_rtt(call->net->socket, call->rxcall); + _rtt /= 64; + rtt = (_rtt > UINT_MAX) ? UINT_MAX : _rtt; + if (rtt < server->probe.rtt) { + server->probe.rtt = rtt; + alist->preferred = index; + have_result = true; + } + + smp_wmb(); /* Set rtt before responded. */ + server->probe.responded = true; + set_bit(AFS_SERVER_FL_PROBED, &server->flags); +out: + spin_unlock(&server->probe_lock); + + _debug("probe [%u][%u] %pISpc rtt=%u ret=%d", + server_index, index, &alist->addrs[index].transport, + (unsigned int)rtt, ret); + + have_result |= afs_fs_probe_done(server); + if (have_result) { + server->probe.have_result = true; + wake_up_var(&server->probe.have_result); + wake_up_all(&server->probe_wq); + } +} + +/* + * Probe all of a fileserver's addresses to find out the best route and to + * query its capabilities. + */ +static int afs_do_probe_fileserver(struct afs_net *net, + struct afs_server *server, + struct key *key, + unsigned int server_index) +{ + struct afs_addr_cursor ac = { + .index = 0, + }; + int ret; + + _enter("%pU", &server->uuid); + + read_lock(&server->fs_lock); + ac.alist = rcu_dereference_protected(server->addresses, + lockdep_is_held(&server->fs_lock)); + read_unlock(&server->fs_lock); + + atomic_set(&server->probe_outstanding, ac.alist->nr_addrs); + memset(&server->probe, 0, sizeof(server->probe)); + server->probe.rtt = UINT_MAX; + + for (ac.index = 0; ac.index < ac.alist->nr_addrs; ac.index++) { + ret = afs_fs_get_capabilities(net, server, &ac, key, server_index, + true); + if (ret != -EINPROGRESS) { + afs_fs_probe_done(server); + return ret; + } + } + + return 0; +} + +/* + * Send off probes to all unprobed servers. + */ +int afs_probe_fileservers(struct afs_net *net, struct key *key, + struct afs_server_list *list) +{ + struct afs_server *server; + int i, ret; + + for (i = 0; i < list->nr_servers; i++) { + server = list->servers[i].server; + if (test_bit(AFS_SERVER_FL_PROBED, &server->flags)) + continue; + + if (!test_and_set_bit_lock(AFS_SERVER_FL_PROBING, &server->flags)) { + ret = afs_do_probe_fileserver(net, server, key, i); + if (ret) + return ret; + } + } + + return 0; +} + +/* + * Wait for the first as-yet untried fileserver to respond. + */ +int afs_wait_for_fs_probes(struct afs_server_list *slist, unsigned long untried) +{ + struct wait_queue_entry *waits; + struct afs_server *server; + unsigned int rtt = UINT_MAX; + bool have_responders = false; + int pref = -1, i; + + _enter("%u,%lx", slist->nr_servers, untried); + + /* Only wait for servers that have a probe outstanding. */ + for (i = 0; i < slist->nr_servers; i++) { + if (test_bit(i, &untried)) { + server = slist->servers[i].server; + if (!test_bit(AFS_SERVER_FL_PROBING, &server->flags)) + __clear_bit(i, &untried); + if (server->probe.responded) + have_responders = true; + } + } + if (have_responders || !untried) + return 0; + + waits = kmalloc(array_size(slist->nr_servers, sizeof(*waits)), GFP_KERNEL); + if (!waits) + return -ENOMEM; + + for (i = 0; i < slist->nr_servers; i++) { + if (test_bit(i, &untried)) { + server = slist->servers[i].server; + init_waitqueue_entry(&waits[i], current); + add_wait_queue(&server->probe_wq, &waits[i]); + } + } + + for (;;) { + bool still_probing = false; + + set_current_state(TASK_INTERRUPTIBLE); + for (i = 0; i < slist->nr_servers; i++) { + if (test_bit(i, &untried)) { + server = slist->servers[i].server; + if (server->probe.responded) + goto stop; + if (test_bit(AFS_SERVER_FL_PROBING, &server->flags)) + still_probing = true; + } + } + + if (!still_probing || unlikely(signal_pending(current))) + goto stop; + schedule(); + } + +stop: + set_current_state(TASK_RUNNING); + + for (i = 0; i < slist->nr_servers; i++) { + if (test_bit(i, &untried)) { + server = slist->servers[i].server; + if (server->probe.responded && + server->probe.rtt < rtt) { + pref = i; + rtt = server->probe.rtt; + } + + remove_wait_queue(&server->probe_wq, &waits[i]); + } + } + + kfree(waits); + + if (pref == -1 && signal_pending(current)) + return -ERESTARTSYS; + + if (pref >= 0) + slist->preferred = pref; + return 0; +} -- cgit v1.2.3