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Message-ID: <159078978453.679399.3917802075646491673.stgit@warthog.procyon.org.uk>
Date: Fri, 29 May 2020 23:03:04 +0100
From: David Howells <dhowells@...hat.com>
To: linux-afs@...ts.infradead.org
Cc: dhowells@...hat.com, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 25/27] afs: Don't use probe running state to make decisions
outside probe code
Don't use the running state for fileserver probes to make decisions about
which server to use as the state is cleared at the start of a probe and
also intermediate values might be misleading.
Instead, add a separate 'latest known' rtt in the afs_server struct and a
flag to indicate if the server is known to be responding and update these
as and when we know what to change them to.
Signed-off-by: David Howells <dhowells@...hat.com>
---
fs/afs/fs_probe.c | 18 ++++++++++++------
fs/afs/internal.h | 4 +++-
fs/afs/rotate.c | 3 ++-
fs/afs/server.c | 1 +
4 files changed, 18 insertions(+), 8 deletions(-)
diff --git a/fs/afs/fs_probe.c b/fs/afs/fs_probe.c
index 442b5e7944ff..c41cf3b2ab89 100644
--- a/fs/afs/fs_probe.c
+++ b/fs/afs/fs_probe.c
@@ -42,10 +42,13 @@ static void afs_finished_fs_probe(struct afs_net *net, struct afs_server *server
bool responded = server->probe.responded;
write_seqlock(&net->fs_lock);
- if (responded)
+ if (responded) {
list_add_tail(&server->probe_link, &net->fs_probe_slow);
- else
+ } else {
+ server->rtt = UINT_MAX;
+ clear_bit(AFS_SERVER_FL_RESPONDING, &server->flags);
list_add_tail(&server->probe_link, &net->fs_probe_fast);
+ }
write_sequnlock(&net->fs_lock);
afs_schedule_fs_probe(net, server, !responded);
@@ -161,12 +164,14 @@ void afs_fileserver_probe_result(struct afs_call *call)
rtt_us = rxrpc_kernel_get_srtt(call->net->socket, call->rxcall);
if (rtt_us < server->probe.rtt) {
server->probe.rtt = rtt_us;
+ server->rtt = rtt_us;
alist->preferred = index;
}
smp_wmb(); /* Set rtt before responded. */
server->probe.responded = true;
set_bit(index, &alist->responded);
+ set_bit(AFS_SERVER_FL_RESPONDING, &server->flags);
out:
spin_unlock(&server->probe_lock);
@@ -224,7 +229,7 @@ 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;
+ unsigned int rtt = UINT_MAX, rtt_s;
bool have_responders = false;
int pref = -1, i;
@@ -280,10 +285,11 @@ int afs_wait_for_fs_probes(struct afs_server_list *slist, unsigned long untried)
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) {
+ rtt_s = READ_ONCE(server->rtt);
+ if (test_bit(AFS_SERVER_FL_RESPONDING, &server->flags) &&
+ rtt_s < rtt) {
pref = i;
- rtt = server->probe.rtt;
+ rtt = rtt_s;
}
remove_wait_queue(&server->probe_wq, &waits[i]);
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index e0dc14d4d8b9..a4fe5d1a8b53 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -496,6 +496,7 @@ struct afs_server {
struct afs_server *gc_next; /* Next server in manager's list */
time64_t unuse_time; /* Time at which last unused */
unsigned long flags;
+#define AFS_SERVER_FL_RESPONDING 0 /* The server is responding */
#define AFS_SERVER_FL_NOT_READY 1 /* The record is not ready for use */
#define AFS_SERVER_FL_NOT_FOUND 2 /* VL server says no such server */
#define AFS_SERVER_FL_VL_FAIL 3 /* Failed to access VL server */
@@ -508,6 +509,7 @@ struct afs_server {
atomic_t ref; /* Object refcount */
atomic_t active; /* Active user count */
u32 addr_version; /* Address list version */
+ unsigned int rtt; /* Server's current RTT in uS */
unsigned int debug_id; /* Debugging ID for traces */
/* file service access */
@@ -522,7 +524,7 @@ struct afs_server {
atomic_t probe_outstanding;
spinlock_t probe_lock;
struct {
- unsigned int rtt; /* RTT as ktime/64 */
+ unsigned int rtt; /* RTT in uS */
u32 abort_code;
short error;
bool responded:1;
diff --git a/fs/afs/rotate.c b/fs/afs/rotate.c
index 979979e33a77..d1590fb382b6 100644
--- a/fs/afs/rotate.c
+++ b/fs/afs/rotate.c
@@ -339,7 +339,8 @@ bool afs_select_fileserver(struct afs_operation *op)
for (i = 0; i < op->server_list->nr_servers; i++) {
struct afs_server *s = op->server_list->servers[i].server;
- if (!test_bit(i, &op->untried) || !s->probe.responded)
+ if (!test_bit(i, &op->untried) ||
+ !test_bit(AFS_SERVER_FL_RESPONDING, &s->flags))
continue;
if (s->probe.rtt < rtt) {
op->index = i;
diff --git a/fs/afs/server.c b/fs/afs/server.c
index 88593ffcb54e..039e3488511c 100644
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -239,6 +239,7 @@ static struct afs_server *afs_alloc_server(struct afs_cell *cell,
INIT_LIST_HEAD(&server->probe_link);
spin_lock_init(&server->probe_lock);
server->cell = cell;
+ server->rtt = UINT_MAX;
afs_inc_servers_outstanding(net);
trace_afs_server(server, 1, 1, afs_server_trace_alloc);
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