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