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                         if (req->rq_state & RQ_WRITE)
 632                                 atomic_sub(req->i.size >> 9, &mdev->ap_in_flight);
 633                 }
 634                 req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
 635
 636                 req->rq_state |= RQ_NET_DONE;
 637
 638                 if (!(req->rq_state & RQ_WRITE))
 639                         goto goto_read_retry_local;
 640
 641                 _req_may_be_done_not_susp(req, m);
 642                 /* else: done by HANDED_OVER_TO_NETWORK */
 643                 break;
 644
 645         goto_read_retry_local:
 646                 if (!drbd_may_do_local_read(mdev, req->i.sector, req->i.size)) {
 647                         _req_may_be_done_not_susp(req, m);
 648                         break;
 649                 }
 650                 D_ASSERT(!(req->rq_state & RQ_LOCAL_PENDING));
 651                 req->rq_state |= RQ_LOCAL_PENDING;
 652
 653                 get_ldev(mdev);
 654                 req->w.cb = w_restart_disk_io;
 655                 drbd_queue_work(&mdev->tconn->data.work, &req->w);
 656                 break;
 657
 658         case FAIL_FROZEN_DISK_IO:
 659                 if (!(req->rq_state & RQ_LOCAL_COMPLETED))
 660                         break;
 661
 662                 _req_may_be_done(req, m); /* Allowed while state.susp */
 663                 break;
 664
 665         case RESTART_FROZEN_DISK_IO:
 666                 if (!(req->rq_state & RQ_LOCAL_COMPLETED))
 667                         break;
 668
 669                 req->rq_state &= ~RQ_LOCAL_COMPLETED;
 670
 671                 rv = MR_READ;
 672                 if (bio_data_dir(req->master_bio) == WRITE)
 673                         rv = MR_WRITE;
 674
 675                 get_ldev(mdev);
 676                 req->w.cb = w_restart_disk_io;
 677                 drbd_queue_work(&mdev->tconn->data.work, &req->w);
 678                 break;
 679
 680         case RESEND:
 681                 /* If RQ_NET_OK is already set, we got a P_WRITE_ACK or P_RECV_ACK
 682                    before the connection loss (B&C only); only P_BARRIER_ACK was missing.
 683                    Trowing them out of the TL here by pretending we got a BARRIER_ACK
 684                    We ensure that the peer was not rebooted */
 685                 if (!(req->rq_state & RQ_NET_OK)) {
 686                         if (req->w.cb) {
 687                                 drbd_queue_work(&mdev->tconn->data.work, &req->w);
 688                                 rv = req->rq_state & RQ_WRITE ? MR_WRITE : MR_READ;
 689                         }
 690                         break;
 691                 }
 692                 /* else, fall through to BARRIER_ACKED */
 693
 694         case BARRIER_ACKED:
 695                 if (!(req->rq_state & RQ_WRITE))
 696                         break;
 697
 698                 if (req->rq_state & RQ_NET_PENDING) {
 699                         /* barrier came in before all requests were acked.
 700                          * this is bad, because if the connection is lost now,
 701                          * we won't be able to clean them up... */
 702                         dev_err(DEV, "FIXME (BARRIER_ACKED but pending)\n");
 703                         list_move(&req->tl_requests, &mdev->tconn->out_of_sequence_requests);
 704                 }
 705                 if ((req->rq_state & RQ_NET_MASK) != 0) {
 706                         req->rq_state |= RQ_NET_DONE;
 707                         if (!(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK)))
 708                                 atomic_sub(req->i.size>>9, &mdev->ap_in_flight);
 709                 }
 710                 _req_may_be_done(req, m); /* Allowed while state.susp */
 711                 break;
 712
 713         case DATA_RECEIVED:
 714                 D_ASSERT(req->rq_state & RQ_NET_PENDING);
 715                 dec_ap_pending(mdev);
 716                 req->rq_state &= ~RQ_NET_PENDING;
 717                 req->rq_state |= (RQ_NET_OK|RQ_NET_DONE);
 718                 _req_may_be_done_not_susp(req, m);
 719                 break;
 720         };
 721
 722         return rv;
 723 }
 724
 725 /* we may do a local read if:
 726  * - we are consistent (of course),
 727  * - or we are generally inconsistent,
 728  *   BUT we are still/already IN SYNC for this area.
 729  *   since size may be bigger than BM_BLOCK_SIZE,
 730  *   we may need to check several bits.
 731  */
 732 static bool drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int size)
 733 {
 734         unsigned long sbnr, ebnr;
 735         sector_t esector, nr_sectors;
 736
 737         if (mdev->state.disk == D_UP_TO_DATE)
 738                 return true;
 739         if (mdev->state.disk != D_INCONSISTENT)
 740                 return false;
 741         esector = sector + (size >> 9) - 1;
 742         nr_sectors = drbd_get_capacity(mdev->this_bdev);
 743         D_ASSERT(sector  < nr_sectors);
 744         D_ASSERT(esector < nr_sectors);
 745
 746         sbnr = BM_SECT_TO_BIT(sector);
 747         ebnr = BM_SECT_TO_BIT(esector);
 748
 749         return drbd_bm_count_bits(mdev, sbnr, ebnr) == 0;
 750 }
 751
 752 static bool remote_due_to_read_balancing(struct drbd_conf *mdev, sector_t sector)
 753 {
 754         enum drbd_read_balancing rbm;
 755         struct backing_dev_info *bdi;
 756         int stripe_shift;
 757
 758         if (mdev->state.pdsk < D_UP_TO_DATE)
 759                 return false;
 760
 761         rcu_read_lock();
 762         rbm = rcu_dereference(mdev->ldev->disk_conf)->read_balancing;
 763         rcu_read_unlock();
 764
 765         switch (rbm) {
 766         case RB_CONGESTED_REMOTE:
 767                 bdi = &mdev->ldev->backing_bdev->bd_disk->queue->backing_dev_info;
 768                 return bdi_read_congested(bdi);
 769         case RB_LEAST_PENDING:
 770                 return atomic_read(&mdev->local_cnt) >
 771                         atomic_read(&mdev->ap_pending_cnt) + atomic_read(&mdev->rs_pending_cnt);
 772         case RB_32K_STRIPING:  /* stripe_shift = 15 */
 773         case RB_64K_STRIPING:
 774         case RB_128K_STRIPING:
 775         case RB_256K_STRIPING:
 776         case RB_512K_STRIPING:
 777         case RB_1M_STRIPING:   /* stripe_shift = 20 */
 778                 stripe_shift = (rbm - RB_32K_STRIPING + 15);
 779                 return (sector >> (stripe_shift - 9)) & 1;
 780         case RB_ROUND_ROBIN:
 781                 return test_and_change_bit(READ_BALANCE_RR, &mdev->flags);
 782         case RB_PREFER_REMOTE:
 783                 return true;
 784         case RB_PREFER_LOCAL:
 785         default:
 786                 return false;
 787         }
 788 }
 789
 790 /*
 791  * complete_conflicting_writes  -  wait for any conflicting write requests
 792  *
 793  * The write_requests tree contains all active write requests which we
 794  * currently know about.  Wait for any requests to complete which conflict with
 795  * the new one.
 796  */
 797 static int complete_conflicting_writes(struct drbd_conf *mdev,
 798                                        sector_t sector, int size)
 799 {
 800         for(;;) {
 801                 struct drbd_interval *i;
 802                 int err;
 803
 804                 i = drbd_find_overlap(&mdev->write_requests, sector, size);
 805                 if (!i)
 806                         return 0;
 807                 err = drbd_wait_misc(mdev, i);
 808                 if (err)
 809                         return err;
 810         }
 811 }
 812
 813 int __drbd_make_request(struct drbd_conf *mdev, struct bio *bio, unsigned long start_time)
 814 {
 815         const int rw = bio_rw(bio);
 816         const int size = bio->bi_size;
 817         const sector_t sector = bio->bi_sector;
 818         struct drbd_tl_epoch *b = NULL;
 819         struct drbd_request *req;
 820         struct net_conf *nc;
 821         int local, remote, send_oos = 0;
 822         int err;
 823         int ret = 0;
 824
 825         /* allocate outside of all locks; */
 826         req = drbd_req_new(mdev, bio);
 827         if (!req) {
 828                 dec_ap_bio(mdev);
 829                 /* only pass the error to the upper layers.
 830                  * if user cannot handle io errors, that's not our business. */
 831                 dev_err(DEV, "could not kmalloc() req\n");
 832                 bio_endio(bio, -ENOMEM);
 833                 return 0;
 834         }
 835         req->start_time = start_time;
 836
 837         local = get_ldev(mdev);
 838         if (!local) {
 839                 bio_put(req->private_bio); /* or we get a bio leak */
 840                 req->private_bio = NULL;
 841         }
 842         if (rw == WRITE) {
 843                 remote = 1;
 844         } else {
 845                 /* READ || READA */
 846                 if (local) {
 847                         if (!drbd_may_do_local_read(mdev, sector, size) ||
 848                             remote_due_to_read_balancing(mdev, sector)) {
 849                                 /* we could kick the syncer to
 850                                  * sync this extent asap, wait for
 851                                  * it, then continue locally.
 852                                  * Or just issue the request remotely.
 853                                  */
 854                                 local = 0;
 855                                 bio_put(req->private_bio);
 856                                 req->private_bio = NULL;
 857                                 put_ldev(mdev);
 858                         }
 859                 }
 860                 remote = !local && mdev->state.pdsk >= D_UP_TO_DATE;
 861         }
 862
 863         /* If we have a disk, but a READA request is mapped to remote,
 864          * we are R_PRIMARY, D_INCONSISTENT, SyncTarget.
 865          * Just fail that READA request right here.
 866          *
 867          * THINK: maybe fail all READA when not local?
 868          *        or make this configurable...
 869          *        if network is slow, READA won't do any good.
 870          */
 871         if (rw == READA && mdev->state.disk >= D_INCONSISTENT && !local) {
 872                 err = -EWOULDBLOCK;
 873                 goto fail_and_free_req;
 874         }
 875
 876         /* For WRITES going to the local disk, grab a reference on the target
 877          * extent.  This waits for any resync activity in the corresponding
 878          * resync extent to finish, and, if necessary, pulls in the target
 879          * extent into the activity log, which involves further disk io because
 880          * of transactional on-disk meta data updates. */
 881         if (rw == WRITE && local && !test_bit(AL_SUSPENDED, &mdev->flags)) {
 882                 req->rq_state |= RQ_IN_ACT_LOG;
 883                 drbd_al_begin_io(mdev, &req->i);
 884         }
 885
 886         remote = remote && drbd_should_do_remote(mdev->state);
 887         send_oos = rw == WRITE && drbd_should_send_out_of_sync(mdev->state);
 888         D_ASSERT(!(remote && send_oos));
 889
 890         if (!(local || remote) && !drbd_suspended(mdev)) {
 891                 if (__ratelimit(&drbd_ratelimit_state))
 892                         dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
 893                 err = -EIO;
 894                 goto fail_free_complete;
 895         }
 896
 897         /* For WRITE request, we have to make sure that we have an
 898          * unused_spare_tle, in case we need to start a new epoch.
 899          * I try to be smart and avoid to pre-allocate always "just in case",
 900          * but there is a race between testing the bit and pointer outside the
 901          * spinlock, and grabbing the spinlock.
 902          * if we lost that race, we retry.  */
 903         if (rw == WRITE && (remote || send_oos) &&
 904             mdev->tconn->unused_spare_tle == NULL &&
 905             test_bit(CREATE_BARRIER, &mdev->tconn->flags)) {
 906 allocate_barrier:
 907                 b = kmalloc(sizeof(struct drbd_tl_epoch), GFP_NOIO);
 908                 if (!b) {
 909                         dev_err(DEV, "Failed to alloc barrier.\n");
 910                         err = -ENOMEM;
 911                         goto fail_free_complete;
 912                 }
 913         }
 914
 915         /* GOOD, everything prepared, grab the spin_lock */
 916         spin_lock_irq(&mdev->tconn->req_lock);
 917
 918         if (rw == WRITE) {
 919                 err = complete_conflicting_writes(mdev, sector, size);
 920                 if (err) {
 921                         if (err != -ERESTARTSYS)
 922                                 _conn_request_state(mdev->tconn,
 923                                                     NS(conn, C_TIMEOUT),
 924                                                     CS_HARD);
 925                         spin_unlock_irq(&mdev->tconn->req_lock);
 926                         err = -EIO;
 927                         goto fail_free_complete;
 928                 }
 929         }
 930
 931         if (drbd_suspended(mdev)) {
 932                 /* If we got suspended, use the retry mechanism of
 933                    generic_make_request() to restart processing of this
 934                    bio. In the next call to drbd_make_request
 935                    we sleep in inc_ap_bio() */
 936                 ret = 1;
 937                 spin_unlock_irq(&mdev->tconn->req_lock);
 938                 goto fail_free_complete;
 939         }
 940
 941         if (remote || send_oos) {
 942                 remote = drbd_should_do_remote(mdev->state);
 943                 send_oos = rw == WRITE && drbd_should_send_out_of_sync(mdev->state);
 944                 D_ASSERT(!(remote && send_oos));
 945
 946                 if (!(remote || send_oos))
 947                         dev_warn(DEV, "lost connection while grabbing the req_lock!\n");
 948                 if (!(local || remote)) {
 949                         dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
 950                         spin_unlock_irq(&mdev->tconn->req_lock);
 951                         err = -EIO;
 952                         goto fail_free_complete;
 953                 }
 954         }
 955
 956         if (b && mdev->tconn->unused_spare_tle == NULL) {
 957                 mdev->tconn->unused_spare_tle = b;
 958                 b = NULL;
 959         }
 960         if (rw == WRITE && (remote || send_oos) &&
 961             mdev->tconn->unused_spare_tle == NULL &&
 962             test_bit(CREATE_BARRIER, &mdev->tconn->flags)) {
 963                 /* someone closed the current epoch
 964                  * while we were grabbing the spinlock */
 965                 spin_unlock_irq(&mdev->tconn->req_lock);
 966                 goto allocate_barrier;
 967         }
 968
 969
 970         /* Update disk stats */
 971         _drbd_start_io_acct(mdev, req, bio);
 972
 973         /* _maybe_start_new_epoch(mdev);
 974          * If we need to generate a write barrier packet, we have to add the
 975          * new epoch (barrier) object, and queue the barrier packet for sending,
 976          * and queue the req's data after it _within the same lock_, otherwise
 977          * we have race conditions were the reorder domains could be mixed up.
 978          *
 979          * Even read requests may start a new epoch and queue the corresponding
 980          * barrier packet.  To get the write ordering right, we only have to
 981          * make sure that, if this is a write request and it triggered a
 982          * barrier packet, this request is queued within the same spinlock. */
 983         if ((remote || send_oos) && mdev->tconn->unused_spare_tle &&
 984             test_and_clear_bit(CREATE_BARRIER, &mdev->tconn->flags)) {
 985                 _tl_add_barrier(mdev->tconn, mdev->tconn->unused_spare_tle);
 986                 mdev->tconn->unused_spare_tle = NULL;
 987         } else {
 988                 D_ASSERT(!(remote && rw == WRITE &&
 989                            test_bit(CREATE_BARRIER, &mdev->tconn->flags)));
 990         }
 991
 992         /* NOTE
 993          * Actually, 'local' may be wrong here already, since we may have failed
 994          * to write to the meta data, and may become wrong anytime because of
 995          * local io-error for some other request, which would lead to us
 996          * "detaching" the local disk.
 997          *
 998          * 'remote' may become wrong any time because the network could fail.
 999          *
1000          * This is a harmless race condition, though, since it is handled
1001          * correctly at the appropriate places; so it just defers the failure
1002          * of the respective operation.
1003          */
1004
1005         /* mark them early for readability.
1006          * this just sets some state flags. */
1007         if (remote)
1008                 _req_mod(req, TO_BE_SENT);
1009         if (local)
1010                 _req_mod(req, TO_BE_SUBMITTED);
1011
1012         list_add_tail(&req->tl_requests, &mdev->tconn->newest_tle->requests);
1013
1014         /* NOTE remote first: to get the concurrent write detection right,
1015          * we must register the request before start of local IO.  */
1016         if (remote) {
1017                 /* either WRITE and C_CONNECTED,
1018                  * or READ, and no local disk,
1019                  * or READ, but not in sync.
1020                  */
1021                 _req_mod(req, (rw == WRITE)
1022                                 ? QUEUE_FOR_NET_WRITE
1023                                 : QUEUE_FOR_NET_READ);
1024         }
1025         if (send_oos && drbd_set_out_of_sync(mdev, sector, size))
1026                 _req_mod(req, QUEUE_FOR_SEND_OOS);
1027
1028         rcu_read_lock();
1029         nc = rcu_dereference(mdev->tconn->net_conf);
1030         if (remote &&
1031             nc->on_congestion != OC_BLOCK && mdev->tconn->agreed_pro_version >= 96) {
1032                 int congested = 0;
1033
1034                 if (nc->cong_fill &&
1035                     atomic_read(&mdev->ap_in_flight) >= nc->cong_fill) {
1036                         dev_info(DEV, "Congestion-fill threshold reached\n");
1037                         congested = 1;
1038                 }
1039
1040                 if (mdev->act_log->used >= nc->cong_extents) {
1041                         dev_info(DEV, "Congestion-extents threshold reached\n");
1042                         congested = 1;
1043                 }
1044
1045                 if (congested) {
1046                         queue_barrier(mdev); /* last barrier, after mirrored writes */
1047
1048                         if (nc->on_congestion == OC_PULL_AHEAD)
1049                                 _drbd_set_state(_NS(mdev, conn, C_AHEAD), 0, NULL);
1050                         else  /*nc->on_congestion == OC_DISCONNECT */
1051                                 _drbd_set_state(_NS(mdev, conn, C_DISCONNECTING), 0, NULL);
1052                 }
1053         }
1054         rcu_read_unlock();
1055
1056         spin_unlock_irq(&mdev->tconn->req_lock);
1057         kfree(b); /* if someone else has beaten us to it... */
1058
1059         if (local) {
1060                 req->private_bio->bi_bdev = mdev->ldev->backing_bdev;
1061
1062                 /* State may have changed since we grabbed our reference on the
1063                  * mdev->ldev member. Double check, and short-circuit to endio.
1064                  * In case the last activity log transaction failed to get on
1065                  * stable storage, and this is a WRITE, we may not even submit
1066                  * this bio. */
1067                 if (get_ldev(mdev)) {
1068                         if (drbd_insert_fault(mdev,   rw == WRITE ? DRBD_FAULT_DT_WR
1069                                                     : rw == READ  ? DRBD_FAULT_DT_RD
1070                                                     :               DRBD_FAULT_DT_RA))
1071                                 bio_endio(req->private_bio, -EIO);
1072                         else
1073                                 generic_make_request(req->private_bio);
1074                         put_ldev(mdev);
1075                 } else
1076                         bio_endio(req->private_bio, -EIO);
1077         }
1078
1079         return 0;
1080
1081 fail_free_complete:
1082         if (req->rq_state & RQ_IN_ACT_LOG)
1083                 drbd_al_complete_io(mdev, &req->i);
1084 fail_and_free_req:
1085         if (local) {
1086                 bio_put(req->private_bio);
1087                 req->private_bio = NULL;
1088                 put_ldev(mdev);
1089         }
1090         if (!ret)
1091                 bio_endio(bio, err);
1092
1093         drbd_req_free(req);
1094         dec_ap_bio(mdev);
1095         kfree(b);
1096
1097         return ret;
1098 }
1099
1100 int drbd_make_request(struct request_queue *q, struct bio *bio)
1101 {
1102         struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
1103         unsigned long start_time;
1104
1105         start_time = jiffies;
1106
1107         /*
1108          * what we "blindly" assume:
1109          */
1110         D_ASSERT(bio->bi_size > 0);
1111         D_ASSERT(IS_ALIGNED(bio->bi_size, 512));
1112
1113         inc_ap_bio(mdev);
1114         return __drbd_make_request(mdev, bio, start_time);
1115 }
1116
1117 /* This is called by bio_add_page().
1118  *
1119  * q->max_hw_sectors and other global limits are already enforced there.
1120  *
1121  * We need to call down to our lower level device,
1122  * in case it has special restrictions.
1123  *
1124  * We also may need to enforce configured max-bio-bvecs limits.
1125  *
1126  * As long as the BIO is empty we have to allow at least one bvec,
1127  * regardless of size and offset, so no need to ask lower levels.
1128  */
1129 int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec)
1130 {
1131         struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
1132         unsigned int bio_size = bvm->bi_size;
1133         int limit = DRBD_MAX_BIO_SIZE;
1134         int backing_limit;
1135
1136         if (bio_size && get_ldev(mdev)) {
1137                 struct request_queue * const b =
1138                         mdev->ldev->backing_bdev->bd_disk->queue;
1139                 if (b->merge_bvec_fn) {
1140                         backing_limit = b->merge_bvec_fn(b, bvm, bvec);
1141                         limit = min(limit, backing_limit);
1142                 }
1143                 put_ldev(mdev);
1144         }
1145         return limit;
1146 }
1147
1148 void request_timer_fn(unsigned long data)
1149 {
1150         struct drbd_conf *mdev = (struct drbd_conf *) data;
1151         struct drbd_tconn *tconn = mdev->tconn;
1152         struct drbd_request *req; /* oldest request */
1153         struct list_head *le;
1154         struct net_conf *nc;
1155         unsigned long ent = 0, dt = 0, et, nt; /* effective timeout = ko_count * timeout */
1156
1157         rcu_read_lock();
1158         nc = rcu_dereference(tconn->net_conf);
1159         ent = nc ? nc->timeout * HZ/10 * nc->ko_count : 0;
1160
1161         if (get_ldev(mdev)) {
1162                 dt = rcu_dereference(mdev->ldev->disk_conf)->disk_timeout * HZ / 10;
1163                 put_ldev(mdev);
1164         }
1165         rcu_read_unlock();
1166
1167         et = min_not_zero(dt, ent);
1168
1169         if (!et || (mdev->state.conn < C_WF_REPORT_PARAMS && mdev->state.disk <= D_FAILED))
1170                 return; /* Recurring timer stopped */
1171
1172         spin_lock_irq(&tconn->req_lock);
1173         le = &tconn->oldest_tle->requests;
1174         if (list_empty(le)) {
1175                 spin_unlock_irq(&tconn->req_lock);
1176                 mod_timer(&mdev->request_timer, jiffies + et);
1177                 return;
1178         }
1179
1180         le = le->prev;
1181         req = list_entry(le, struct drbd_request, tl_requests);
1182         if (ent && req->rq_state & RQ_NET_PENDING) {
1183                 if (time_is_before_eq_jiffies(req->start_time + ent)) {
1184                         dev_warn(DEV, "Remote failed to finish a request within ko-count * timeout\n");
1185                         _drbd_set_state(_NS(mdev, conn, C_TIMEOUT), CS_VERBOSE | CS_HARD, NULL);
1186                 }
1187         }
1188         if (dt && req->rq_state & RQ_LOCAL_PENDING) {
1189                 if (time_is_before_eq_jiffies(req->start_time + dt)) {
1190                         dev_warn(DEV, "Local backing device failed to meet the disk-timeout\n");
1191                         __drbd_chk_io_error(mdev, 1);
1192                 }
1193         }
1194         nt = (time_is_before_eq_jiffies(req->start_time + et) ? jiffies : req->start_time) + et;
1195         spin_unlock_irq(&tconn->req_lock);
1196         mod_timer(&mdev->request_timer, nt);
1197 }