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authorDavid Howells <dhowells@redhat.com>2018-10-20 00:57:59 +0100
committerDavid Howells <dhowells@redhat.com>2018-10-24 00:41:09 +0100
commit3bf0fb6f33dd545693da5e65f5b1b9b9f0bfc35e (patch)
treedf215e6a6ad11b6ac8158461144667e168591d28 /fs/afs/fs_probe.c
parent18ac61853cc4e44eb30e125fc8344a3b25c7b6fe (diff)
downloadlinux-3bf0fb6f33dd545693da5e65f5b1b9b9f0bfc35e.tar.bz2
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>
Diffstat (limited to 'fs/afs/fs_probe.c')
-rw-r--r--fs/afs/fs_probe.c270
1 files changed, 270 insertions, 0 deletions
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 <linux/sched.h>
+#include <linux/slab.h>
+#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;
+}