drivers/block/drbd/drbd_req.c

   1 /*
   2    drbd_req.c
   3
   4    This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
   5
   6    Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
   7    Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
   8    Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
   9
  10    drbd is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 2, or (at your option)
  13    any later version.
  14
  15    drbd is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with drbd; see the file COPYING.  If not, write to
  22    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  23
  24  */
  25
  26 #include <linux/module.h>
  27
  28 #include <linux/slab.h>
  29 #include <linux/drbd.h>
  30 #include "drbd_int.h"
  31 #include "drbd_req.h"
  32
  33
  34 static bool drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int size);
  35
  36 /* Update disk stats at start of I/O request */
  37 static void _drbd_start_io_acct(struct drbd_conf *mdev, struct drbd_request *req, struct bio *bio)
  38 {
  39         const int rw = bio_data_dir(bio);
  40         int cpu;
  41         cpu = part_stat_lock();
  42         part_round_stats(cpu, &mdev->vdisk->part0);
  43         part_stat_inc(cpu, &mdev->vdisk->part0, ios[rw]);
  44         part_stat_add(cpu, &mdev->vdisk->part0, sectors[rw], bio_sectors(bio));
  45         (void) cpu; /* The macro invocations above want the cpu argument, I do not like
  46                        the compiler warning about cpu only assigned but never used... */
  47         part_inc_in_flight(&mdev->vdisk->part0, rw);
  48         part_stat_unlock();
  49 }
  50
  51 /* Update disk stats when completing request upwards */
  52 static void _drbd_end_io_acct(struct drbd_conf *mdev, struct drbd_request *req)
  53 {
  54         int rw = bio_data_dir(req->master_bio);
  55         unsigned long duration = jiffies - req->start_time;
  56         int cpu;
  57         cpu = part_stat_lock();
  58         part_stat_add(cpu, &mdev->vdisk->part0, ticks[rw], duration);
  59         part_round_stats(cpu, &mdev->vdisk->part0);
  60         part_dec_in_flight(&mdev->vdisk->part0, rw);
  61         part_stat_unlock();
  62 }
  63
  64 static struct drbd_request *drbd_req_new(struct drbd_conf *mdev,
  65                                                struct bio *bio_src)
  66 {
  67         struct drbd_request *req;
  68
  69         req = mempool_alloc(drbd_request_mempool, GFP_NOIO);
  70         if (!req)
  71                 return NULL;
  72
  73         drbd_req_make_private_bio(req, bio_src);
  74         req->rq_state    = bio_data_dir(bio_src) == WRITE ? RQ_WRITE : 0;
  75         req->w.mdev      = mdev;
  76         req->master_bio  = bio_src;
  77         req->epoch       = 0;
  78
  79         drbd_clear_interval(&req->i);
  80         req->i.sector     = bio_src->bi_sector;
  81         req->i.size      = bio_src->bi_size;
  82         req->i.local = true;
  83         req->i.waiting = false;
  84
  85         INIT_LIST_HEAD(&req->tl_requests);
  86         INIT_LIST_HEAD(&req->w.list);
  87
  88         return req;
  89 }
  90
  91 static void drbd_req_free(struct drbd_request *req)
  92 {
  93         mempool_free(req, drbd_request_mempool);
  94 }
  95
  96 /* rw is bio_data_dir(), only READ or WRITE */
  97 static void _req_is_done(struct drbd_conf *mdev, struct drbd_request *req, const int rw)
  98 {
  99         const unsigned long s = req->rq_state;
 100
 101         /* remove it from the transfer log.
 102          * well, only if it had been there in the first
 103          * place... if it had not (local only or conflicting
 104          * and never sent), it should still be "empty" as
 105          * initialized in drbd_req_new(), so we can list_del() it
 106          * here unconditionally */
 107         list_del(&req->tl_requests);
 108
 109         /* if it was a write, we may have to set the corresponding
 110          * bit(s) out-of-sync first. If it had a local part, we need to
 111          * release the reference to the activity log. */
 112         if (rw == WRITE) {
 113                 /* Set out-of-sync unless both OK flags are set
 114                  * (local only or remote failed).
 115                  * Other places where we set out-of-sync:
 116                  * READ with local io-error */
 117                 if (!(s & RQ_NET_OK) || !(s & RQ_LOCAL_OK))
 118                         drbd_set_out_of_sync(mdev, req->i.sector, req->i.size);
 119
 120                 if ((s & RQ_NET_OK) && (s & RQ_LOCAL_OK) && (s & RQ_NET_SIS))
 121                         drbd_set_in_sync(mdev, req->i.sector, req->i.size);
 122
 123                 /* one might be tempted to move the drbd_al_complete_io
 124                  * to the local io completion callback drbd_request_endio.
 125                  * but, if this was a mirror write, we may only
 126                  * drbd_al_complete_io after this is RQ_NET_DONE,
 127                  * otherwise the extent could be dropped from the al
 128                  * before it has actually been written on the peer.
 129                  * if we crash before our peer knows about the request,
 130                  * but after the extent has been dropped from the al,
 131                  * we would forget to resync the corresponding extent.
 132                  */
 133                 if (s & RQ_LOCAL_MASK) {
 134                         if (get_ldev_if_state(mdev, D_FAILED)) {
 135                                 if (s & RQ_IN_ACT_LOG)
 136                                         drbd_al_complete_io(mdev, &req->i);
 137                                 put_ldev(mdev);
 138                         } else if (__ratelimit(&drbd_ratelimit_state)) {
 139                                 dev_warn(DEV, "Should have called drbd_al_complete_io(, %llu, %u), "
 140                                          "but my Disk seems to have failed :(\n",
 141                                          (unsigned long long) req->i.sector, req->i.size);
 142                         }
 143                 }
 144         }
 145
 146         drbd_req_free(req);
 147 }
 148
 149 static void queue_barrier(struct drbd_conf *mdev)
 150 {
 151         struct drbd_tl_epoch *b;
 152         struct drbd_tconn *tconn = mdev->tconn;
 153
 154         /* We are within the req_lock. Once we queued the barrier for sending,
 155          * we set the CREATE_BARRIER bit. It is cleared as soon as a new
 156          * barrier/epoch object is added. This is the only place this bit is
 157          * set. It indicates that the barrier for this epoch is already queued,
 158          * and no new epoch has been created yet. */
 159         if (test_bit(CREATE_BARRIER, &tconn->flags))
 160                 return;
 161
 162         b = tconn->newest_tle;
 163         b->w.cb = w_send_barrier;
 164         b->w.mdev = mdev;
 165         /* inc_ap_pending done here, so we won't
 166          * get imbalanced on connection loss.
 167          * dec_ap_pending will be done in got_BarrierAck
 168          * or (on connection loss) in tl_clear.  */
 169         inc_ap_pending(mdev);
 170         drbd_queue_work(&tconn->data.work, &b->w);
 171         set_bit(CREATE_BARRIER, &tconn->flags);
 172 }
 173
 174 static void _about_to_complete_local_write(struct drbd_conf *mdev,
 175         struct drbd_request *req)
 176 {
 177         const unsigned long s = req->rq_state;
 178
 179         /* Before we can signal completion to the upper layers,
 180          * we may need to close the current epoch.
 181          * We can skip this, if this request has not even been sent, because we
 182          * did not have a fully established connection yet/anymore, during
 183          * bitmap exchange, or while we are C_AHEAD due to congestion policy.
 184          */
 185         if (mdev->state.conn >= C_CONNECTED &&
 186             (s & RQ_NET_SENT) != 0 &&
 187             req->epoch == mdev->tconn->newest_tle->br_number)
 188                 queue_barrier(mdev);
 189 }
 190
 191 void complete_master_bio(struct drbd_conf *mdev,
 192                 struct bio_and_error *m)
 193 {
 194         bio_endio(m->bio, m->error);
 195         dec_ap_bio(mdev);
 196 }
 197
 198
 199 static void drbd_remove_request_interval(struct rb_root *root,
 200                                          struct drbd_request *req)
 201 {
 202         struct drbd_conf *mdev = req->w.mdev;
 203         struct drbd_interval *i = &req->i;
 204
 205         drbd_remove_interval(root, i);
 206
 207         /* Wake up any processes waiting for this request to complete.  */
 208         if (i->waiting)
 209                 wake_up(&mdev->misc_wait);
 210 }
 211
 212 /* Helper for __req_mod().
 213  * Set m->bio to the master bio, if it is fit to be completed,
 214  * or leave it alone (it is initialized to NULL in __req_mod),
 215  * if it has already been completed, or cannot be completed yet.
 216  * If m->bio is set, the error status to be returned is placed in m->error.
 217  */
 218 void _req_may_be_done(struct drbd_request *req, struct bio_and_error *m)
 219 {
 220         const unsigned long s = req->rq_state;
 221         struct drbd_conf *mdev = req->w.mdev;
 222         int rw = req->rq_state & RQ_WRITE ? WRITE : READ;
 223
 224         /* we must not complete the master bio, while it is
 225          *      still being processed by _drbd_send_zc_bio (drbd_send_dblock)
 226          *      not yet acknowledged by the peer
 227          *      not yet completed by the local io subsystem
 228          * these flags may get cleared in any order by
 229          *      the worker,
 230          *      the receiver,
 231          *      the bio_endio completion callbacks.
 232          */
 233         if (s & RQ_LOCAL_PENDING && !(s & RQ_LOCAL_ABORTED))
 234                 return;
 235         if (req->i.waiting) {
 236                 /* Retry all conflicting peer requests.  */
 237                 wake_up(&mdev->misc_wait);
 238         }
 239         if (s & RQ_NET_QUEUED)
 240                 return;
 241         if (s & RQ_NET_PENDING)
 242                 return;
 243
 244         if (req->master_bio) {
 245                 /* this is DATA_RECEIVED (remote read)
 246                  * or protocol C P_WRITE_ACK
 247                  * or protocol B P_RECV_ACK
 248                  * or protocol A "HANDED_OVER_TO_NETWORK" (SendAck)
 249                  * or canceled or failed,
 250                  * or killed from the transfer log due to connection loss.
 251                  */
 252
 253                 /*
 254                  * figure out whether to report success or failure.
 255                  *
 256                  * report success when at least one of the operations succeeded.
 257                  * or, to put the other way,
 258                  * only report failure, when both operations failed.
 259                  *
 260                  * what to do about the failures is handled elsewhere.
 261                  * what we need to do here is just: complete the master_bio.
 262                  *
 263                  * local completion error, if any, has been stored as ERR_PTR
 264                  * in private_bio within drbd_request_endio.
 265                  */
 266                 int ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
 267                 int error = PTR_ERR(req->private_bio);
 268
 269                 /* remove the request from the conflict detection
 270                  * respective block_id verification hash */
 271                 if (!drbd_interval_empty(&req->i)) {
 272                         struct rb_root *root;
 273
 274                         if (rw == WRITE)
 275                                 root = &mdev->write_requests;
 276                         else
 277                                 root = &mdev->read_requests;
 278                         drbd_remove_request_interval(root, req);
 279                 } else if (!(s & RQ_POSTPONED))
 280                         D_ASSERT((s & (RQ_NET_MASK & ~RQ_NET_DONE)) == 0);
 281
 282                 /* for writes we need to do some extra housekeeping */
 283                 if (rw == WRITE)
 284                         _about_to_complete_local_write(mdev, req);
 285
 286                 /* Update disk stats */
 287                 _drbd_end_io_acct(mdev, req);
 288
 289                 if (!(s & RQ_POSTPONED)) {
 290                         m->error = ok ? 0 : (error ?: -EIO);
 291                         m->bio = req->master_bio;
 292                 }
 293                 req->master_bio = NULL;
 294         }
 295
 296         if (s & RQ_LOCAL_PENDING)
 297                 return;
 298
 299         if ((s & RQ_NET_MASK) == 0 || (s & RQ_NET_DONE)) {
 300                 /* this is disconnected (local only) operation,
 301                  * or protocol A, B, or C P_BARRIER_ACK,
 302                  * or killed from the transfer log due to connection loss. */
 303                 _req_is_done(mdev, req, rw);
 304         }
 305         /* else: network part and not DONE yet. that is
 306          * protocol A, B, or C, barrier ack still pending... */
 307 }
 308
 309 static void _req_may_be_done_not_susp(struct drbd_request *req, struct bio_and_error *m)
 310 {
 311         struct drbd_conf *mdev = req->w.mdev;
 312
 313         if (!drbd_suspended(mdev))
 314                 _req_may_be_done(req, m);
 315 }
 316
 317 /* obviously this could be coded as many single functions
 318  * instead of one huge switch,
 319  * or by putting the code directly in the respective locations
 320  * (as it has been before).
 321  *
 322  * but having it this way
 323  *  enforces that it is all in this one place, where it is easier to audit,
 324  *  it makes it obvious that whatever "event" "happens" to a request should
 325  *  happen "atomically" within the req_lock,
 326  *  and it enforces that we have to think in a very structured manner
 327  *  about the "events" that may happen to a request during its life time ...
 328  */
 329 int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 330                 struct bio_and_error *m)
 331 {
 332         struct drbd_conf *mdev = req->w.mdev;
 333         struct net_conf *nc;
 334         int p, rv = 0;
 335
 336         if (m)
 337                 m->bio = NULL;
 338
 339         switch (what) {
 340         default:
 341                 dev_err(DEV, "LOGIC BUG in %s:%u\n", __FILE__ , __LINE__);
 342                 break;
 343
 344         /* does not happen...
 345          * initialization done in drbd_req_new
 346         case CREATED:
 347                 break;
 348                 */
 349
 350         case TO_BE_SENT: /* via network */
 351                 /* reached via __drbd_make_request
 352                  * and from w_read_retry_remote */
 353                 D_ASSERT(!(req->rq_state & RQ_NET_MASK));
 354                 req->rq_state |= RQ_NET_PENDING;
 355                 rcu_read_lock();
 356                 nc = rcu_dereference(mdev->tconn->net_conf);
 357                 p = nc->wire_protocol;
 358                 rcu_read_unlock();
 359                 req->rq_state |=
 360                         p == DRBD_PROT_C ? RQ_EXP_WRITE_ACK :
 361                         p == DRBD_PROT_B ? RQ_EXP_RECEIVE_ACK : 0;
 362                 inc_ap_pending(mdev);
 363                 break;
 364
 365         case TO_BE_SUBMITTED: /* locally */
 366                 /* reached via __drbd_make_request */
 367                 D_ASSERT(!(req->rq_state & RQ_LOCAL_MASK));
 368                 req->rq_state |= RQ_LOCAL_PENDING;
 369                 break;
 370
 371         case COMPLETED_OK:
 372                 if (req->rq_state & RQ_WRITE)
 373                         mdev->writ_cnt += req->i.size >> 9;
 374                 else
 375                         mdev->read_cnt += req->i.size >> 9;
 376
 377                 req->rq_state |= (RQ_LOCAL_COMPLETED|RQ_LOCAL_OK);
 378                 req->rq_state &= ~RQ_LOCAL_PENDING;
 379
 380                 _req_may_be_done_not_susp(req, m);
 381                 put_ldev(mdev);
 382                 break;
 383
 384         case ABORT_DISK_IO:
 385                 req->rq_state |= RQ_LOCAL_ABORTED;
 386                 if (req->rq_state & RQ_WRITE)
 387                         _req_may_be_done_not_susp(req, m);
 388                 else
 389                         goto goto_queue_for_net_read;
 390                 break;
 391
 392         case WRITE_COMPLETED_WITH_ERROR:
 393                 req->rq_state |= RQ_LOCAL_COMPLETED;
 394                 req->rq_state &= ~RQ_LOCAL_PENDING;
 395
 396                 __drbd_chk_io_error(mdev, false);
 397                 _req_may_be_done_not_susp(req, m);
 398                 put_ldev(mdev);
 399                 break;
 400
 401         case READ_AHEAD_COMPLETED_WITH_ERROR:
 402                 /* it is legal to fail READA */
 403                 req->rq_state |= RQ_LOCAL_COMPLETED;
 404                 req->rq_state &= ~RQ_LOCAL_PENDING;
 405                 _req_may_be_done_not_susp(req, m);
 406                 put_ldev(mdev);
 407                 break;
 408
 409         case READ_COMPLETED_WITH_ERROR:
 410                 drbd_set_out_of_sync(mdev, req->i.sector, req->i.size);
 411
 412                 req->rq_state |= RQ_LOCAL_COMPLETED;
 413                 req->rq_state &= ~RQ_LOCAL_PENDING;
 414
 415                 D_ASSERT(!(req->rq_state & RQ_NET_MASK));
 416
 417                 __drbd_chk_io_error(mdev, false);
 418                 put_ldev(mdev);
 419
 420         goto_queue_for_net_read:
 421
 422                 /* no point in retrying if there is no good remote data,
 423                  * or we have no connection. */
 424                 if (mdev->state.pdsk != D_UP_TO_DATE) {
 425                         _req_may_be_done_not_susp(req, m);
 426                         break;
 427                 }
 428
 429                 /* _req_mod(req,TO_BE_SENT); oops, recursion... */
 430                 req->rq_state |= RQ_NET_PENDING;
 431                 inc_ap_pending(mdev);
 432                 /* fall through: _req_mod(req,QUEUE_FOR_NET_READ); */
 433
 434         case QUEUE_FOR_NET_READ:
 435                 /* READ or READA, and
 436                  * no local disk,
 437                  * or target area marked as invalid,
 438                  * or just got an io-error. */
 439                 /* from __drbd_make_request
 440                  * or from bio_endio during read io-error recovery */
 441
 442                 /* so we can verify the handle in the answer packet
 443                  * corresponding hlist_del is in _req_may_be_done() */
 444                 D_ASSERT(drbd_interval_empty(&req->i));
 445                 drbd_insert_interval(&mdev->read_requests, &req->i);
 446
 447                 set_bit(UNPLUG_REMOTE, &mdev->flags);
 448
 449                 D_ASSERT(req->rq_state & RQ_NET_PENDING);
 450                 req->rq_state |= RQ_NET_QUEUED;
 451                 req->w.cb = (req->rq_state & RQ_LOCAL_MASK)
 452                         ? w_read_retry_remote
 453                         : w_send_read_req;
 454                 drbd_queue_work(&mdev->tconn->data.work, &req->w);
 455                 break;
 456
 457         case QUEUE_FOR_NET_WRITE:
 458                 /* assert something? */
 459                 /* from __drbd_make_request only */
 460
 461                 /* corresponding hlist_del is in _req_may_be_done() */
 462                 D_ASSERT(drbd_interval_empty(&req->i));
 463                 drbd_insert_interval(&mdev->write_requests, &req->i);
 464
 465                 /* NOTE
 466                  * In case the req ended up on the transfer log before being
 467                  * queued on the worker, it could lead to this request being
 468                  * missed during cleanup after connection loss.
 469                  * So we have to do both operations here,
 470                  * within the same lock that protects the transfer log.
 471                  *
 472                  * _req_add_to_epoch(req); this has to be after the
 473                  * _maybe_start_new_epoch(req); which happened in
 474                  * __drbd_make_request, because we now may set the bit
 475                  * again ourselves to close the current epoch.
 476                  *
 477                  * Add req to the (now) current epoch (barrier). */
 478
 479                 /* otherwise we may lose an unplug, which may cause some remote
 480                  * io-scheduler timeout to expire, increasing maximum latency,
 481                  * hurting performance. */
 482                 set_bit(UNPLUG_REMOTE, &mdev->flags);
 483
 484                 /* see __drbd_make_request,
 485                  * just after it grabs the req_lock */
 486                 D_ASSERT(test_bit(CREATE_BARRIER, &mdev->tconn->flags) == 0);
 487
 488                 req->epoch = mdev->tconn->newest_tle->br_number;
 489
 490                 /* increment size of current epoch */
 491                 mdev->tconn->newest_tle->n_writes++;
 492
 493                 /* queue work item to send data */
 494                 D_ASSERT(req->rq_state & RQ_NET_PENDING);
 495                 req->rq_state |= RQ_NET_QUEUED;
 496                 req->w.cb =  w_send_dblock;
 497                 drbd_queue_work(&mdev->tconn->data.work, &req->w);
 498
 499                 /* close the epoch, in case it outgrew the limit */
 500                 rcu_read_lock();
 501                 nc = rcu_dereference(mdev->tconn->net_conf);
 502                 p = nc->max_epoch_size;
 503                 rcu_read_unlock();
 504                 if (mdev->tconn->newest_tle->n_writes >= p)
 505                         queue_barrier(mdev);
 506
 507                 break;
 508
 509         case QUEUE_FOR_SEND_OOS:
 510                 req->rq_state |= RQ_NET_QUEUED;
 511                 req->w.cb =  w_send_out_of_sync;
 512                 drbd_queue_work(&mdev->tconn->data.work, &req->w);
 513                 break;
 514
 515         case OOS_HANDED_TO_NETWORK:
 516                 /* actually the same */
 517         case SEND_CANCELED:
 518                 /* treat it the same */
 519         case SEND_FAILED:
 520                 /* real cleanup will be done from tl_clear.  just update flags
 521                  * so it is no longer marked as on the worker queue */
 522                 req->rq_state &= ~RQ_NET_QUEUED;
 523                 /* if we did it right, tl_clear should be scheduled only after
 524                  * this, so this should not be necessary! */
 525                 _req_may_be_done_not_susp(req, m);
 526                 break;
 527
 528         case HANDED_OVER_TO_NETWORK:
 529                 /* assert something? */
 530                 if (bio_data_dir(req->master_bio) == WRITE)
 531                         atomic_add(req->i.size >> 9, &mdev->ap_in_flight);
 532
 533                 if (bio_data_dir(req->master_bio) == WRITE &&
 534                     !(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK))) {
 535                         /* this is what is dangerous about protocol A:
 536                          * pretend it was successfully written on the peer. */
 537                         if (req->rq_state & RQ_NET_PENDING) {
 538                                 dec_ap_pending(mdev);
 539                                 req->rq_state &= ~RQ_NET_PENDING;
 540                                 req->rq_state |= RQ_NET_OK;
 541                         } /* else: neg-ack was faster... */
 542                         /* it is still not yet RQ_NET_DONE until the
 543                          * corresponding epoch barrier got acked as well,
 544                          * so we know what to dirty on connection loss */
 545                 }
 546                 req->rq_state &= ~RQ_NET_QUEUED;
 547                 req->rq_state |= RQ_NET_SENT;
 548                 /* because _drbd_send_zc_bio could sleep, and may want to
 549                  * dereference the bio even after the "WRITE_ACKED_BY_PEER" and
 550                  * "COMPLETED_OK" events came in, once we return from
 551                  * _drbd_send_zc_bio (drbd_send_dblock), we have to check
 552                  * whether it is done already, and end it.  */
 553                 _req_may_be_done_not_susp(req, m);
 554                 break;
 555
 556         case READ_RETRY_REMOTE_CANCELED:
 557                 req->rq_state &= ~RQ_NET_QUEUED;
 558                 /* fall through, in case we raced with drbd_disconnect */
 559         case CONNECTION_LOST_WHILE_PENDING:
 560                 /* transfer log cleanup after connection loss */
 561                 /* assert something? */
 562                 if (req->rq_state & RQ_NET_PENDING)
 563                         dec_ap_pending(mdev);
 564
 565                 p = !(req->rq_state & RQ_WRITE) && req->rq_state & RQ_NET_PENDING;
 566
 567                 req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
 568                 req->rq_state |= RQ_NET_DONE;
 569                 if (req->rq_state & RQ_NET_SENT && req->rq_state & RQ_WRITE)
 570                         atomic_sub(req->i.size >> 9, &mdev->ap_in_flight);
 571
 572                 /* if it is still queued, we may not complete it here.
 573                  * it will be canceled soon. */
 574                 if (!(req->rq_state & RQ_NET_QUEUED)) {
 575                         if (p)
 576                                 goto goto_read_retry_local;
 577                         _req_may_be_done(req, m); /* Allowed while state.susp */
 578                 }
 579                 break;
 580
 581         case WRITE_ACKED_BY_PEER_AND_SIS:
 582                 req->rq_state |= RQ_NET_SIS;
 583         case DISCARD_WRITE:
 584                 /* for discarded conflicting writes of multiple primaries,
 585                  * there is no need to keep anything in the tl, potential
 586                  * node crashes are covered by the activity log. */
 587                 req->rq_state |= RQ_NET_DONE;
 588                 /* fall through */
 589         case WRITE_ACKED_BY_PEER:
 590                 D_ASSERT(req->rq_state & RQ_EXP_WRITE_ACK);
 591                 /* protocol C; successfully written on peer.
 592                  * Nothing to do here.
 593                  * We want to keep the tl in place for all protocols, to cater
 594                  * for volatile write-back caches on lower level devices.
 595                  *
 596                  * A barrier request is expected to have forced all prior
 597                  * requests onto stable storage, so completion of a barrier
 598                  * request could set NET_DONE right here, and not wait for the
 599                  * P_BARRIER_ACK, but that is an unnecessary optimization. */
 600
 601                 goto ack_common;
 602                 /* this makes it effectively the same as for: */
 603         case RECV_ACKED_BY_PEER:
 604                 D_ASSERT(req->rq_state & RQ_EXP_RECEIVE_ACK);
 605                 /* protocol B; pretends to be successfully written on peer.
 606                  * see also notes above in HANDED_OVER_TO_NETWORK about
 607                  * protocol != C */
 608         ack_common:
 609                 req->rq_state |= RQ_NET_OK;
 610                 D_ASSERT(req->rq_state & RQ_NET_PENDING);
 611                 dec_ap_pending(mdev);
 612                 atomic_sub(req->i.size >> 9, &mdev->ap_in_flight);
 613                 req->rq_state &= ~RQ_NET_PENDING;
 614                 _req_may_be_done_not_susp(req, m);
 615                 break;
 616
 617         case POSTPONE_WRITE:
 618                 D_ASSERT(req->rq_state & RQ_EXP_WRITE_ACK);
 619                 /* If this node has already detected the write conflict, the
 620                  * worker will be waiting on misc_wait.  Wake it up once this
 621                  * request has completed locally.
 622                  */
 623                 D_ASSERT(req->rq_state & RQ_NET_PENDING);
 624                 req->rq_state |= RQ_POSTPONED;
 625                 _req_may_be_done_not_susp(req, m);
 626                 break;
 627
 628         case NEG_ACKED:
 629                 /* assert something? */
 630                 if (req->rq_state & RQ_NET_PENDING) {
 631                         dec_ap_pending(mdev);
 632                         if (req->rq_state & RQ_WRITE)
 633                                 atomic_sub(req->i.size >> 9, &mdev->ap_in_flight);
 634                 }
 635                 req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
 636
 637                 req->rq_state |= RQ_NET_DONE;
 638
 639                 if (!(req->rq_state & RQ_WRITE))
 640                         goto goto_read_retry_local;
 641
 642                 _req_may_be_done_not_susp(req, m);
 643                 /* else: done by HANDED_OVER_TO_NETWORK */
 644                 break;
 645
 646         goto_read_retry_local:
 647                 if (!drbd_may_do_local_read(mdev, req->i.sector, req->i.size)) {
 648                         _req_may_be_done_not_susp(req, m);
 649                         break;
 650                 }
 651                 D_ASSERT(!(req->rq_state & RQ_LOCAL_PENDING));
 652                 req->rq_state |= RQ_LOCAL_PENDING;
 653
 654                 get_ldev(mdev);
 655                 req->w.cb = w_restart_disk_io;
 656                 drbd_queue_work(&mdev->tconn->data.work, &req->w);
 657                 break;
 658
 659         case FAIL_FROZEN_DISK_IO:
 660                 if (!(req->rq_state & RQ_LOCAL_COMPLETED))
 661                         break;
 662
 663                 _req_may_be_done(req, m); /* Allowed while state.susp */
 664                 break;
 665
 666         case RESTART_FROZEN_DISK_IO:
 667                 if (!(req->rq_state & RQ_LOCAL_COMPLETED))
 668                         break;
 669
 670                 req->rq_state &= ~RQ_LOCAL_COMPLETED;
 671
 672                 rv = MR_READ;
 673                 if (bio_data_dir(req->master_bio) == WRITE)
 674                         rv = MR_WRITE;
 675
 676                 get_ldev(mdev);
 677                 req->w.cb = w_restart_disk_io;
 678                 drbd_queue_work(&mdev->tconn->data.work, &req->w);
 679                 break;
 680
 681         case RESEND:
 682                 /* If RQ_NET_OK is already set, we got a P_WRITE_ACK or P_RECV_ACK
 683                    before the connection loss (B&C only); only P_BARRIER_ACK was missing.
 684                    Trowing them out of the TL here by pretending we got a BARRIER_ACK
 685                    We ensure that the peer was not rebooted */
 686                 if (!(req->rq_state & RQ_NET_OK)) {
 687                         if (req->w.cb) {
 688                                 drbd_queue_work(&mdev->tconn->data.work, &req->w);
 689                                 rv = req->rq_state & RQ_WRITE ? MR_WRITE : MR_READ;
 690                         }
 691                         break;
 692                 }
 693                 /* else, fall through to BARRIER_ACKED */
 694
 695         case BARRIER_ACKED:
 696                 if (!(req->rq_state & RQ_WRITE))
 697                         break;
 698
 699                 if (req->rq_state & RQ_NET_PENDING) {
 700                         /* barrier came in before all requests were acked.
 701                          * this is bad, because if the connection is lost now,
 702                          * we won't be able to clean them up... */
 703                         dev_err(DEV, "FIXME (BARRIER_ACKED but pending)\n");
 704                         list_move(&req->tl_requests, &mdev->tconn->out_of_sequence_requests);
 705                 }
 706                 if ((req->rq_state & RQ_NET_MASK) != 0) {
 707                         req->rq_state |= RQ_NET_DONE;
 708                         if (!(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK)))
 709                                 atomic_sub(req->i.size>>9, &mdev->ap_in_flight);
 710                 }
 711                 _req_may_be_done(req, m); /* Allowed while state.susp */
 712                 break;
 713
 714         case DATA_RECEIVED:
 715                 D_ASSERT(req->rq_state & RQ_NET_PENDING);
 716                 dec_ap_pending(mdev);
 717                 req->rq_state &= ~RQ_NET_PENDING;
 718                 req->rq_state |= (RQ_NET_OK|RQ_NET_DONE);
 719                 _req_may_be_done_not_susp(req, m);
 720                 break;
 721         };
 722
 723         return rv;
 724 }
 725
 726 /* we may do a local read if:
 727  * - we are consistent (of course),
 728  * - or we are generally inconsistent,
 729  *   BUT we are still/already IN SYNC for this area.
 730  *   since size may be bigger than BM_BLOCK_SIZE,
 731  *   we may need to check several bits.
 732  */
 733 static bool drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int size)
 734 {
 735         unsigned long sbnr, ebnr;
 736         sector_t esector, nr_sectors;
 737
 738         if (mdev->state.disk == D_UP_TO_DATE)
 739                 return true;
 740         if (mdev->state.disk != D_INCONSISTENT)
 741                 return false;
 742         esector = sector + (size >> 9) - 1;
 743         nr_sectors = drbd_get_capacity(mdev->this_bdev);
 744         D_ASSERT(sector  < nr_sectors);
 745         D_ASSERT(esector < nr_sectors);
 746
 747         sbnr = BM_SECT_TO_BIT(sector);
 748         ebnr = BM_SECT_TO_BIT(esector);
 749
 750         return drbd_bm_count_bits(mdev, sbnr, ebnr) == 0;
 751 }
 752
 753 static bool remote_due_to_read_balancing(struct drbd_conf *mdev, sector_t sector)
 754 {
 755         enum drbd_read_balancing rbm;
 756         struct backing_dev_info *bdi;
 757         int stripe_shift;
 758
 759         if (mdev->state.pdsk < D_UP_TO_DATE)
 760                 return false;
 761
 762         rcu_read_lock();
 763         rbm = rcu_dereference(mdev->ldev->disk_conf)->read_balancing;
 764         rcu_read_unlock();
 765
 766         switch (rbm) {
 767         case RB_CONGESTED_REMOTE:
 768                 bdi = &mdev->ldev->backing_bdev->bd_disk->queue->backing_dev_info;
 769                 return bdi_read_congested(bdi);
 770         case RB_LEAST_PENDING:
 771                 return atomic_read(&mdev->local_cnt) >
 772                         atomic_read(&mdev->ap_pending_cnt) + atomic_read(&mdev->rs_pending_cnt);
 773         case RB_32K_STRIPING:  /* stripe_shift = 15 */
 774         case RB_64K_STRIPING:
 775         case RB_128K_STRIPING:
 776         case RB_256K_STRIPING:
 777         case RB_512K_STRIPING:
 778         case RB_1M_STRIPING:   /* stripe_shift = 20 */
 779                 stripe_shift = (rbm - RB_32K_STRIPING + 15);
 780                 return (sector >> (stripe_shift - 9)) & 1;
 781         case RB_ROUND_ROBIN:
 782                 return test_and_change_bit(READ_BALANCE_RR, &mdev->flags);
 783         case RB_PREFER_REMOTE:
 784                 return true;
 785         case RB_PREFER_LOCAL:
 786         default:
 787                 return false;
 788         }
 789 }
 790
 791 /*
 792  * complete_conflicting_writes  -  wait for any conflicting write requests
 793  *
 794  * The write_requests tree contains all active write requests which we
 795  * currently know about.  Wait for any requests to complete which conflict with
 796  * the new one.
 797  */
 798 static int complete_conflicting_writes(struct drbd_conf *mdev,
 799                                        sector_t sector, int size)
 800 {
 801         for(;;) {
 802                 struct drbd_interval *i;
 803                 int err;
 804
 805                 i = drbd_find_overlap(&mdev->write_requests, sector, size);
 806                 if (!i)
 807                         return 0;
 808                 err = drbd_wait_misc(mdev, i);
 809                 if (err)
 810                         return err;
 811         }
 812 }
 813
 814 int __drbd_make_request(struct drbd_conf *mdev, struct bio *bio, unsigned long start_time)
 815 {
 816         const int rw = bio_rw(bio);
 817         const int size = bio->bi_size;
 818         const sector_t sector = bio->bi_sector;
 819         struct drbd_tl_epoch *b = NULL;
 820         struct drbd_request *req;
 821         struct net_conf *nc;
 822         int local, remote, send_oos = 0;
 823         int err;
 824         int ret = 0;
 825         union drbd_dev_state s;
 826
 827         /* allocate outside of all locks; */
 828         req = drbd_req_new(mdev, bio);
 829         if (!req) {
 830                 dec_ap_bio(mdev);
 831                 /* only pass the error to the upper layers.
 832                  * if user cannot handle io errors, that's not our business. */
 833                 dev_err(DEV, "could not kmalloc() req\n");
 834                 bio_endio(bio, -ENOMEM);
 835                 return 0;
 836         }
 837         req->start_time = start_time;
 838
 839         local = get_ldev(mdev);
 840         if (!local) {
 841                 bio_put(req->private_bio); /* or we get a bio leak */
 842                 req->private_bio = NULL;
 843         }
 844         if (rw == WRITE) {
 845                 remote = 1;
 846         } else {
 847                 /* READ || READA */
 848                 if (local) {
 849                         if (!drbd_may_do_local_read(mdev, sector, size) ||
 850                             remote_due_to_read_balancing(mdev, sector)) {
 851                                 /* we could kick the syncer to
 852                                  * sync this extent asap, wait for
 853                                  * it, then continue locally.
 854                                  * Or just issue the request remotely.
 855                                  */
 856                                 local = 0;
 857                                 bio_put(req->private_bio);
 858                                 req->private_bio = NULL;
 859                                 put_ldev(mdev);
 860                         }
 861                 }
 862                 remote = !local && mdev->state.pdsk >= D_UP_TO_DATE;
 863         }
 864
 865         /* If we have a disk, but a READA request is mapped to remote,
 866          * we are R_PRIMARY, D_INCONSISTENT, SyncTarget.
 867          * Just fail that READA request right here.
 868          *
 869          * THINK: maybe fail all READA when not local?
 870          *        or make this configurable...
 871          *        if network is slow, READA won't do any good.
 872          */
 873         if (rw == READA && mdev->state.disk >= D_INCONSISTENT && !local) {
 874                 err = -EWOULDBLOCK;
 875                 goto fail_and_free_req;
 876         }
 877
 878         /* For WRITES going to the local disk, grab a reference on the target
 879          * extent.  This waits for any resync activity in the corresponding
 880          * resync extent to finish, and, if necessary, pulls in the target
 881          * extent into the activity log, which involves further disk io because
 882          * of transactional on-disk meta data updates. */
 883         if (rw == WRITE && local && !test_bit(AL_SUSPENDED, &mdev->flags)) {
 884                 req->rq_state |= RQ_IN_ACT_LOG;
 885                 drbd_al_begin_io(mdev, &req->i);
 886         }
 887
 888         s = mdev->state;
 889         remote = remote && drbd_should_do_remote(s);
 890         send_oos = rw == WRITE && drbd_should_send_out_of_sync(s);
 891         D_ASSERT(!(remote && send_oos));
 892
 893         if (!(local || remote) && !drbd_suspended(mdev)) {
 894                 if (__ratelimit(&drbd_ratelimit_state))
 895                         dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
 896                 err = -EIO;
 897                 goto fail_free_complete;
 898         }
 899
 900         /* For WRITE request, we have to make sure that we have an
 901          * unused_spare_tle, in case we need to start a new epoch.
 902          * I try to be smart and avoid to pre-allocate always "just in case",
 903          * but there is a race between testing the bit and pointer outside the
 904          * spinlock, and grabbing the spinlock.
 905          * if we lost that race, we retry.  */
 906         if (rw == WRITE && (remote || send_oos) &&
 907             mdev->tconn->unused_spare_tle == NULL &&
 908             test_bit(CREATE_BARRIER, &mdev->tconn->flags)) {
 909 allocate_barrier:
 910                 b = kmalloc(sizeof(struct drbd_tl_epoch), GFP_NOIO);
 911                 if (!b) {
 912                         dev_err(DEV, "Failed to alloc barrier.\n");
 913                         err = -ENOMEM;
 914                         goto fail_free_complete;
 915                 }
 916         }
 917
 918         /* GOOD, everything prepared, grab the spin_lock */
 919         spin_lock_irq(&mdev->tconn->req_lock);
 920
 921         if (rw == WRITE) {
 922                 err = complete_conflicting_writes(mdev, sector, size);
 923                 if (err) {
 924                         if (err != -ERESTARTSYS)
 925                                 _conn_request_state(mdev->tconn,
 926                                                     NS(conn, C_TIMEOUT),
 927                                                     CS_HARD);
 928                         spin_unlock_irq(&mdev->tconn->req_lock);
 929                         err = -EIO;
 930                         goto fail_free_complete;
 931                 }
 932         }
 933
 934         if (drbd_suspended(mdev)) {
 935                 /* If we got suspended, use the retry mechanism in
 936                    drbd_make_request() to restart processing of this
 937                    bio. In the next call to drbd_make_request
 938                    we sleep in inc_ap_bio() */
 939                 ret = 1;
 940                 spin_unlock_irq(&mdev->tconn->req_lock);
 941                 goto fail_free_complete;
 942         }
 943
 944         if (remote || send_oos) {
 945                 remote = drbd_should_do_remote(mdev->state);
 946                 send_oos = rw == WRITE && drbd_should_send_out_of_sync(mdev->state);
 947                 D_ASSERT(!(remote && send_oos));
 948
 949                 if (!(remote || send_oos))
 950                         dev_warn(DEV, "lost connection while grabbing the req_lock!\n");
 951                 if (!(local || remote)) {
 952                         dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
 953                         spin_unlock_irq(&mdev->tconn->req_lock);
 954                         err = -EIO;
 955                         goto fail_free_complete;
 956                 }
 957         }
 958
 959         if (b && mdev->tconn->unused_spare_tle == NULL) {
 960                 mdev->tconn->unused_spare_tle = b;
 961                 b = NULL;
 962         }
 963         if (rw == WRITE && (remote || send_oos) &&
 964             mdev->tconn->unused_spare_tle == NULL &&
 965             test_bit(CREATE_BARRIER, &mdev->tconn->flags)) {
 966                 /* someone closed the current epoch
 967                  * while we were grabbing the spinlock */
 968                 spin_unlock_irq(&mdev->tconn->req_lock);
 969                 goto allocate_barrier;
 970         }
 971
 972
 973         /* Update disk stats */
 974         _drbd_start_io_acct(mdev, req, bio);
 975
 976         /* _maybe_start_new_epoch(mdev);
 977          * If we need to generate a write barrier packet, we have to add the
 978          * new epoch (barrier) object, and queue the barrier packet for sending,
 979          * and queue the req's data after it _within the same lock_, otherwise
 980          * we have race conditions were the reorder domains could be mixed up.
 981          *
 982          * Even read requests may start a new epoch and queue the corresponding
 983          * barrier packet.  To get the write ordering right, we only have to
 984          * make sure that, if this is a write request and it triggered a
 985          * barrier packet, this request is queued within the same spinlock. */
 986         if ((remote || send_oos) && mdev->tconn->unused_spare_tle &&
 987             test_and_clear_bit(CREATE_BARRIER, &mdev->tconn->flags)) {
 988                 _tl_add_barrier(mdev->tconn, mdev->tconn->unused_spare_tle);
 989                 mdev->tconn->unused_spare_tle = NULL;
 990         } else {
 991                 D_ASSERT(!(remote && rw == WRITE &&
 992                            test_bit(CREATE_BARRIER, &mdev->tconn->flags)));
 993         }
 994
 995         /* NOTE
 996          * Actually, 'local' may be wrong here already, since we may have failed
 997          * to write to the meta data, and may become wrong anytime because of
 998          * local io-error for some other request, which would lead to us
 999          * "detaching" the local disk.
1000          *
1001          * 'remote' may become wrong any time because the network could fail.
1002          *
1003          * This is a harmless race condition, though, since it is handled
1004          * correctly at the appropriate places; so it just defers the failure
1005          * of the respective operation.
1006          */
1007
1008         /* mark them early for readability.
1009          * this just sets some state flags. */
1010         if (remote)
1011                 _req_mod(req, TO_BE_SENT);
1012         if (local)
1013                 _req_mod(req, TO_BE_SUBMITTED);
1014
1015         list_add_tail(&req->tl_requests, &mdev->tconn->newest_tle->requests);
1016
1017         /* NOTE remote first: to get the concurrent write detection right,
1018          * we must register the request before start of local IO.  */
1019         if (remote) {
1020                 /* either WRITE and C_CONNECTED,
1021                  * or READ, and no local disk,
1022                  * or READ, but not in sync.
1023                  */
1024                 _req_mod(req, (rw == WRITE)
1025                                 ? QUEUE_FOR_NET_WRITE
1026                                 : QUEUE_FOR_NET_READ);
1027         }
1028         if (send_oos && drbd_set_out_of_sync(mdev, sector, size))
1029                 _req_mod(req, QUEUE_FOR_SEND_OOS);
1030
1031         rcu_read_lock();
1032         nc = rcu_dereference(mdev->tconn->net_conf);
1033         if (remote &&
1034             nc->on_congestion != OC_BLOCK && mdev->tconn->agreed_pro_version >= 96) {
1035                 int congested = 0;
1036
1037                 if (nc->cong_fill &&
1038                     atomic_read(&mdev->ap_in_flight) >= nc->cong_fill) {
1039                         dev_info(DEV, "Congestion-fill threshold reached\n");
1040                         congested = 1;
1041                 }
1042
1043                 if (mdev->act_log->used >= nc->cong_extents) {
1044                         dev_info(DEV, "Congestion-extents threshold reached\n");
1045                         congested = 1;
1046                 }
1047
1048                 if (congested) {
1049                         queue_barrier(mdev); /* last barrier, after mirrored writes */
1050
1051                         if (nc->on_congestion == OC_PULL_AHEAD)
1052                                 _drbd_set_state(_NS(mdev, conn, C_AHEAD), 0, NULL);
1053                         else  /*nc->on_congestion == OC_DISCONNECT */
1054                                 _drbd_set_state(_NS(mdev, conn, C_DISCONNECTING), 0, NULL);
1055                 }
1056         }
1057         rcu_read_unlock();
1058
1059         spin_unlock_irq(&mdev->tconn->req_lock);
1060         kfree(b); /* if someone else has beaten us to it... */
1061
1062         if (local) {
1063                 req->private_bio->bi_bdev = mdev->ldev->backing_bdev;
1064
1065                 /* State may have changed since we grabbed our reference on the
1066                  * mdev->ldev member. Double check, and short-circuit to endio.
1067                  * In case the last activity log transaction failed to get on
1068                  * stable storage, and this is a WRITE, we may not even submit
1069                  * this bio. */
1070                 if (get_ldev(mdev)) {
1071                         if (drbd_insert_fault(mdev,   rw == WRITE ? DRBD_FAULT_DT_WR
1072                                                     : rw == READ  ? DRBD_FAULT_DT_RD
1073                                                     :               DRBD_FAULT_DT_RA))
1074                                 bio_endio(req->private_bio, -EIO);
1075                         else
1076                                 generic_make_request(req->private_bio);
1077                         put_ldev(mdev);
1078                 } else
1079                         bio_endio(req->private_bio, -EIO);
1080         }
1081
1082         return 0;
1083
1084 fail_free_complete:
1085         if (req->rq_state & RQ_IN_ACT_LOG)
1086                 drbd_al_complete_io(mdev, &req->i);
1087 fail_and_free_req:
1088         if (local) {
1089                 bio_put(req->private_bio);
1090                 req->private_bio = NULL;
1091                 put_ldev(mdev);
1092         }
1093         if (!ret)
1094                 bio_endio(bio, err);
1095
1096         drbd_req_free(req);
1097         dec_ap_bio(mdev);
1098         kfree(b);
1099
1100         return ret;
1101 }
1102
1103 int drbd_make_request(struct request_queue *q, struct bio *bio)
1104 {
1105         struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
1106         unsigned long start_time;
1107
1108         start_time = jiffies;
1109
1110         /*
1111          * what we "blindly" assume:
1112          */
1113         D_ASSERT(bio->bi_size > 0);
1114         D_ASSERT(IS_ALIGNED(bio->bi_size, 512));
1115
1116         do {
1117                 inc_ap_bio(mdev);
1118         } while (__drbd_make_request(mdev, bio, start_time));
1119
1120         return 0;
1121 }
1122
1123 /* This is called by bio_add_page().
1124  *
1125  * q->max_hw_sectors and other global limits are already enforced there.
1126  *
1127  * We need to call down to our lower level device,
1128  * in case it has special restrictions.
1129  *
1130  * We also may need to enforce configured max-bio-bvecs limits.
1131  *
1132  * As long as the BIO is empty we have to allow at least one bvec,
1133  * regardless of size and offset, so no need to ask lower levels.
1134  */
1135 int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec)
1136 {
1137         struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
1138         unsigned int bio_size = bvm->bi_size;
1139         int limit = DRBD_MAX_BIO_SIZE;
1140         int backing_limit;
1141
1142         if (bio_size && get_ldev(mdev)) {
1143                 struct request_queue * const b =
1144                         mdev->ldev->backing_bdev->bd_disk->queue;
1145                 if (b->merge_bvec_fn) {
1146                         backing_limit = b->merge_bvec_fn(b, bvm, bvec);
1147                         limit = min(limit, backing_limit);
1148                 }
1149                 put_ldev(mdev);
1150         }
1151         return limit;
1152 }
1153
1154 void request_timer_fn(unsigned long data)
1155 {
1156         struct drbd_conf *mdev = (struct drbd_conf *) data;
1157         struct drbd_tconn *tconn = mdev->tconn;
1158         struct drbd_request *req; /* oldest request */
1159         struct list_head *le;
1160         struct net_conf *nc;
1161         unsigned long ent = 0, dt = 0, et, nt; /* effective timeout = ko_count * timeout */
1162
1163         rcu_read_lock();
1164         nc = rcu_dereference(tconn->net_conf);
1165         ent = nc ? nc->timeout * HZ/10 * nc->ko_count : 0;
1166
1167         if (get_ldev(mdev)) {
1168                 dt = rcu_dereference(mdev->ldev->disk_conf)->disk_timeout * HZ / 10;
1169                 put_ldev(mdev);
1170         }
1171         rcu_read_unlock();
1172
1173         et = min_not_zero(dt, ent);
1174
1175         if (!et || (mdev->state.conn < C_WF_REPORT_PARAMS && mdev->state.disk <= D_FAILED))
1176                 return; /* Recurring timer stopped */
1177
1178         spin_lock_irq(&tconn->req_lock);
1179         le = &tconn->oldest_tle->requests;
1180         if (list_empty(le)) {
1181                 spin_unlock_irq(&tconn->req_lock);
1182                 mod_timer(&mdev->request_timer, jiffies + et);
1183                 return;
1184         }
1185
1186         le = le->prev;
1187         req = list_entry(le, struct drbd_request, tl_requests);
1188         if (ent && req->rq_state & RQ_NET_PENDING) {
1189                 if (time_is_before_eq_jiffies(req->start_time + ent)) {
1190                         dev_warn(DEV, "Remote failed to finish a request within ko-count * timeout\n");
1191                         _drbd_set_state(_NS(mdev, conn, C_TIMEOUT), CS_VERBOSE | CS_HARD, NULL);
1192                 }
1193         }
1194         if (dt && req->rq_state & RQ_LOCAL_PENDING && req->w.mdev == mdev) {
1195                 if (time_is_before_eq_jiffies(req->start_time + dt)) {
1196                         dev_warn(DEV, "Local backing device failed to meet the disk-timeout\n");
1197                         __drbd_chk_io_error(mdev, 1);
1198                 }
1199         }
1200         nt = (time_is_before_eq_jiffies(req->start_time + et) ? jiffies : req->start_time) + et;
1201         spin_unlock_irq(&tconn->req_lock);
1202         mod_timer(&mdev->request_timer, nt);
1203 }