[LU-11951] sanity: test_231a failure, idle disconnect & import generation disagreement

Duplicate — Tue, 19 Dec 2023 14:28:51 +0000

These observations are drawn from this test failure/logs (master + a few unrelated patches):

https://testing.whamcloud.com/test_sets/7ed37e66-2b3a-11e9-90fb-52540065bddc

sanity 231a.

dd fails for no particular reason in the middle of a pretty innocuous test.

A disconnect/idle request is sent:

00000100:00100000:0.0:1549584426.013412:0:3658:0:(client.c:1631:ptlrpc_send_new_req()) Sending RPC pname:cluuid:pid:xid:nid:opc ptlrpcd_rcv:6a3d5a57-20e1-3c31-d0be-69db5e11ff93:3658:1624855787560768:10.9.5.221@tcp:9

It has not completed yet.

A lock request is made:

 00010000:00010000:1.0:1549584426.079672:0:25756:0:(ldlm_request.c:1019:ldlm_cli_enqueue()) ### sending request ns: lustre-OST0006-osc-ffff8853e612d000 lock: ffff8853c1acd200/0x600e7a448b87755c lrc: 3/0,1 mode: -/PW res: [0x75c0:0x0:0x0].0x0 rrc: 2 type: EXT [0->4194303] (req 0>4194303) flags: 0x0 nid: local remote: 0x0 expref: -99 pid: 25756 timeout: 0 lvb_type: 1
00000100:00080000:1.0:1549584426.079679:0:25756:0:(client.c:1575:ptlrpc_send_new_req()) @@@ req waiting for recovery: (FULL != CONNECTING)  req@ffff8853e63e3a80

The disconnect comes back:

 00000100:00080000:0.0:1549584426.491344:0:3658:0:(import.c:1677:ptlrpc_disconnect_idle_interpret()) @@@ inflight=2, refcount=6: rc = 0
  req@ffff8853e63e2400 x1624855787560768/t0(0) o9->lustre-OST0006-osc-ffff8853e612d000@10.9.5.221@tcp:28/4 lens 224/192 e 0 to 0 dl 1549584432 ref 1 fl Interpret:RN/0/0 rc 0/0

It notices a request has happened and reconnects immediately:

 00000100:00080000:0.0:1549584426.491350:0:3658:0:(import.c:1693:ptlrpc_disconnect_idle_interpret()) ffff8853fbff1800 lustre-OST0006_UUID: changing import state from IDLE to NEW
00000100:00080000:0.0:1549584426.491361:0:3658:0:(import.c:683:ptlrpc_connect_import()) ffff8853fbff1800 lustre-OST0006_UUID: changing import state from NEW to CONNECTING

The delayed lock request is rejected for import generation difference:

 00000100:00080000:0.0:1549584426.491919:0:3658:0:(recover.c:223:ptlrpc_wake_delayed()) @@@ waking (set ffff88538df3fc80):  req@ffff8853e63e3a80 x1624855787560912/t0(0) o101->lustre-OST0006-osc-ffff8853e612d000@10.9.5.221@tcp:28/4 lens 328/400 e 0 to 0 dl 0 ref 2 fl Rpc:W/0/ffffffff rc 0/-1
00000100:00100000:0.0:1549584426.491929:0:3658:0:(client.c:2061:ptlrpc_check_set()) Completed RPC pname:cluuid:pid:xid:nid:opc ptlrpcd_rcv:6a3d5a57-20e1-3c31-d0be-69db5e11ff93:3658:1624855787560928:10.9.5.221@tcp:8
00000100:00020000:1.0:1549584426.491944:0:25756:0:(client.c:1193:ptlrpc_import_delay_req()) @@@ req wrong generation:  req@ffff8853e63e3a80 x1624855787560912/t0(0) o101->lustre-OST0006-osc-ffff8853e612d000@10.9.5.221@tcp:28/4 lens 328/400 e 0 to 0 dl 0 ref 2 fl Rpc:W/0/ffffffff rc 0/-1
00000100:00100000:1.0:1549584426.496060:0:25756:0:(client.c:2061:ptlrpc_check_set()) Completed RPC pname:cluuid:pid:xid:nid:opc dd:6a3d5a57-20e1-3c31-d0be-69db5e11ff93:25756:1624855787560912:10.9.5.221@tcp:101
00010000:00010000:1.0:1549584426.496066:0:25756:0:(ldlm_request.c:592:ldlm_cli_enqueue_fini()) ### client-side enqueue END (FAILED) ns: lustre-OST0006-osc-ffff8853e612d000 lock: ffff8853c1acd200/0x600e7a448b87755c lrc: 4/0,1 mode: -/PW res: [0x75c0:0x0:0x0].0x0 rrc: 2 type: EXT [0->4194303] (req 0>4194303) flags: 0x0 nid: local remote: 0x0 expref: -99 pid: 25756 timeout: 0 lvb_type: 1

Here's the problem.

ptlrpc_request_alloc_internal uses IMP_IDLE as a way to tell if it should start a new connection:

      if (unlikely(imp->imp_state == LUSTRE_IMP_IDLE)) {

And increment the generation number as part of that:

                 if (imp->imp_state == LUSTRE_IMP_IDLE) {
                        imp->imp_generation++;
                        imp->imp_initiated_at = imp->imp_generation;
                        imp->imp_state =  LUSTRE_IMP_NEW;
                        connect = 1;

After this, the request generation in the request is set to match that of the import. So if this doesn't happen, the existing import generation is stored in the request.

However, the idle code (ptlrpc_disconnect_prep_req) sets the import state to connecting:

IMPORT_SET_STATE(imp, LUSTRE_IMP_CONNECTING);

Then sends the request. And only sets IMP_IDLE only once the import is fully idle, in

ptlrpc_disconnect_idle_interpret:

 /* DISCONNECT reply can be late and another connection can just
         * be initiated. so we have to abort disconnection. */
        if (req->rq_import_generation == imp->imp_generation &&
            imp->imp_state != LUSTRE_IMP_CLOSED) {
                LASSERTF(imp->imp_state == LUSTRE_IMP_CONNECTING,
                         "%s\n", ptlrpc_import_state_name(imp->imp_state));
                imp->imp_state = LUSTRE_IMP_IDLE;

So the request_alloc_internal doesn't notice the import is in the process of disconnecting, so it does not start the reconnect early, as intended.

But we increment the generation in disconnect_idle_interpret:

                             if (atomic_read(&imp->imp_inflight) > 1) {
                                                imp->imp_generation++;
                                                imp->imp_initiated_at = imp->imp_generation;
                                                IMPORT_SET_STATE_NOLOCK(imp, LUSTRE_IMP_NEW);
                                                connect = 1;"

I am not really sure of the correct handling of import generation overall. My first instinct is that we should not increment it in this case, as we connect immediately...

But perhaps that's incorrect as well. I'm hoping that Alex will take a look at this.

Whamcloud Community JIRA

[LU-11951] sanity: test_231a failure, idle disconnect & import generation disagreement