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_device *device, 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_device *device, struct drbd_request *req)
  38 {
  39         const int rw = bio_data_dir(req->master_bio);
  40         int cpu;
  41         cpu = part_stat_lock();
  42         part_round_stats(cpu, &device->vdisk->part0);
  43         part_stat_inc(cpu, &device->vdisk->part0, ios[rw]);
  44         part_stat_add(cpu, &device->vdisk->part0, sectors[rw], req->i.size >> 9);
  45         (void) cpu; /* The macro invocations above want the cpu argument, I do not like
  46                        the compiler warning about cpu only assigned but never used... */
  47         part_inc_in_flight(&device->vdisk->part0, rw);
  48         part_stat_unlock();
  49 }
  50
  51 /* Update disk stats when completing request upwards */
  52 static void _drbd_end_io_acct(struct drbd_device *device, struct drbd_request *req)
  53 {
  54         int rw = bio_data_dir(req->master_bio);
  55         unsigned long duration = jiffies - req->start_time;
  56         int cpu;
  57         cpu = part_stat_lock();
  58         part_stat_add(cpu, &device->vdisk->part0, ticks[rw], duration);
  59         part_round_stats(cpu, &device->vdisk->part0);
  60         part_dec_in_flight(&device->vdisk->part0, rw);
  61         part_stat_unlock();
  62 }
  63
  64 static struct drbd_request *drbd_req_new(struct drbd_device *device,
  65                                                struct bio *bio_src)
  66 {
  67         struct drbd_request *req;
  68
  69         req = mempool_alloc(drbd_request_mempool, GFP_NOIO);
  70         if (!req)
  71                 return NULL;
  72
  73         drbd_req_make_private_bio(req, bio_src);
  74         req->rq_state    = bio_data_dir(bio_src) == WRITE ? RQ_WRITE : 0;
  75         req->device   = device;
  76         req->master_bio  = bio_src;
  77         req->epoch       = 0;
  78
  79         drbd_clear_interval(&req->i);
  80         req->i.sector     = bio_src->bi_iter.bi_sector;
  81         req->i.size      = bio_src->bi_iter.bi_size;
  82         req->i.local = true;
  83         req->i.waiting = false;
  84
  85         INIT_LIST_HEAD(&req->tl_requests);
  86         INIT_LIST_HEAD(&req->w.list);
  87
  88         /* one reference to be put by __drbd_make_request */
  89         atomic_set(&req->completion_ref, 1);
  90         /* one kref as long as completion_ref > 0 */
  91         kref_init(&req->kref);
  92         return req;
  93 }
  94
  95 void drbd_req_destroy(struct kref *kref)
  96 {
  97         struct drbd_request *req = container_of(kref, struct drbd_request, kref);
  98         struct drbd_device *device = req->device;
  99         const unsigned s = req->rq_state;
 100
 101         if ((req->master_bio && !(s & RQ_POSTPONED)) ||
 102                 atomic_read(&req->completion_ref) ||
 103                 (s & RQ_LOCAL_PENDING) ||
 104                 ((s & RQ_NET_MASK) && !(s & RQ_NET_DONE))) {
 105                 drbd_err(device, "drbd_req_destroy: Logic BUG rq_state = 0x%x, completion_ref = %d\n",
 106                                 s, atomic_read(&req->completion_ref));
 107                 return;
 108         }
 109
 110         /* remove it from the transfer log.
 111          * well, only if it had been there in the first
 112          * place... if it had not (local only or conflicting
 113          * and never sent), it should still be "empty" as
 114          * initialized in drbd_req_new(), so we can list_del() it
 115          * here unconditionally */
 116         list_del_init(&req->tl_requests);
 117
 118         /* if it was a write, we may have to set the corresponding
 119          * bit(s) out-of-sync first. If it had a local part, we need to
 120          * release the reference to the activity log. */
 121         if (s & RQ_WRITE) {
 122                 /* Set out-of-sync unless both OK flags are set
 123                  * (local only or remote failed).
 124                  * Other places where we set out-of-sync:
 125                  * READ with local io-error */
 126
 127                 /* There is a special case:
 128                  * we may notice late that IO was suspended,
 129                  * and postpone, or schedule for retry, a write,
 130                  * before it even was submitted or sent.
 131                  * In that case we do not want to touch the bitmap at all.
 132                  */
 133                 if ((s & (RQ_POSTPONED|RQ_LOCAL_MASK|RQ_NET_MASK)) != RQ_POSTPONED) {
 134                         if (!(s & RQ_NET_OK) || !(s & RQ_LOCAL_OK))
 135                                 drbd_set_out_of_sync(device, req->i.sector, req->i.size);
 136
 137                         if ((s & RQ_NET_OK) && (s & RQ_LOCAL_OK) && (s & RQ_NET_SIS))
 138                                 drbd_set_in_sync(device, req->i.sector, req->i.size);
 139                 }
 140
 141                 /* one might be tempted to move the drbd_al_complete_io
 142                  * to the local io completion callback drbd_request_endio.
 143                  * but, if this was a mirror write, we may only
 144                  * drbd_al_complete_io after this is RQ_NET_DONE,
 145                  * otherwise the extent could be dropped from the al
 146                  * before it has actually been written on the peer.
 147                  * if we crash before our peer knows about the request,
 148                  * but after the extent has been dropped from the al,
 149                  * we would forget to resync the corresponding extent.
 150                  */
 151                 if (s & RQ_IN_ACT_LOG) {
 152                         if (get_ldev_if_state(device, D_FAILED)) {
 153                                 drbd_al_complete_io(device, &req->i);
 154                                 put_ldev(device);
 155                         } else if (__ratelimit(&drbd_ratelimit_state)) {
 156                                 drbd_warn(device, "Should have called drbd_al_complete_io(, %llu, %u), "
 157                                          "but my Disk seems to have failed :(\n",
 158                                          (unsigned long long) req->i.sector, req->i.size);
 159                         }
 160                 }
 161         }
 162
 163         mempool_free(req, drbd_request_mempool);
 164 }
 165
 166 static void wake_all_senders(struct drbd_connection *connection)
 167 {
 168         wake_up(&connection->sender_work.q_wait);
 169 }
 170
 171 /* must hold resource->req_lock */
 172 void start_new_tl_epoch(struct drbd_connection *connection)
 173 {
 174         /* no point closing an epoch, if it is empty, anyways. */
 175         if (connection->current_tle_writes == 0)
 176                 return;
 177
 178         connection->current_tle_writes = 0;
 179         atomic_inc(&connection->current_tle_nr);
 180         wake_all_senders(connection);
 181 }
 182
 183 void complete_master_bio(struct drbd_device *device,
 184                 struct bio_and_error *m)
 185 {
 186         bio_endio(m->bio, m->error);
 187         dec_ap_bio(device);
 188 }
 189
 190
 191 static void drbd_remove_request_interval(struct rb_root *root,
 192                                          struct drbd_request *req)
 193 {
 194         struct drbd_device *device = req->device;
 195         struct drbd_interval *i = &req->i;
 196
 197         drbd_remove_interval(root, i);
 198
 199         /* Wake up any processes waiting for this request to complete.  */
 200         if (i->waiting)
 201                 wake_up(&device->misc_wait);
 202 }
 203
 204 /* Helper for __req_mod().
 205  * Set m->bio to the master bio, if it is fit to be completed,
 206  * or leave it alone (it is initialized to NULL in __req_mod),
 207  * if it has already been completed, or cannot be completed yet.
 208  * If m->bio is set, the error status to be returned is placed in m->error.
 209  */
 210 static
 211 void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
 212 {
 213         const unsigned s = req->rq_state;
 214         struct drbd_device *device = req->device;
 215         int rw;
 216         int error, ok;
 217
 218         /* we must not complete the master bio, while it is
 219          *      still being processed by _drbd_send_zc_bio (drbd_send_dblock)
 220          *      not yet acknowledged by the peer
 221          *      not yet completed by the local io subsystem
 222          * these flags may get cleared in any order by
 223          *      the worker,
 224          *      the receiver,
 225          *      the bio_endio completion callbacks.
 226          */
 227         if ((s & RQ_LOCAL_PENDING && !(s & RQ_LOCAL_ABORTED)) ||
 228             (s & RQ_NET_QUEUED) || (s & RQ_NET_PENDING) ||
 229             (s & RQ_COMPLETION_SUSP)) {
 230                 drbd_err(device, "drbd_req_complete: Logic BUG rq_state = 0x%x\n", s);
 231                 return;
 232         }
 233
 234         if (!req->master_bio) {
 235                 drbd_err(device, "drbd_req_complete: Logic BUG, master_bio == NULL!\n");
 236                 return;
 237         }
 238
 239         rw = bio_rw(req->master_bio);
 240
 241         /*
 242          * figure out whether to report success or failure.
 243          *
 244          * report success when at least one of the operations succeeded.
 245          * or, to put the other way,
 246          * only report failure, when both operations failed.
 247          *
 248          * what to do about the failures is handled elsewhere.
 249          * what we need to do here is just: complete the master_bio.
 250          *
 251          * local completion error, if any, has been stored as ERR_PTR
 252          * in private_bio within drbd_request_endio.
 253          */
 254         ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
 255         error = PTR_ERR(req->private_bio);
 256
 257         /* remove the request from the conflict detection
 258          * respective block_id verification hash */
 259         if (!drbd_interval_empty(&req->i)) {
 260                 struct rb_root *root;
 261
 262                 if (rw == WRITE)
 263                         root = &device->write_requests;
 264                 else
 265                         root = &device->read_requests;
 266                 drbd_remove_request_interval(root, req);
 267         }
 268
 269         /* Before we can signal completion to the upper layers,
 270          * we may need to close the current transfer log epoch.
 271          * We are within the request lock, so we can simply compare
 272          * the request epoch number with the current transfer log
 273          * epoch number.  If they match, increase the current_tle_nr,
 274          * and reset the transfer log epoch write_cnt.
 275          */
 276         if (rw == WRITE &&
 277             req->epoch == atomic_read(&first_peer_device(device)->connection->current_tle_nr))
 278                 start_new_tl_epoch(first_peer_device(device)->connection);
 279
 280         /* Update disk stats */
 281         _drbd_end_io_acct(device, req);
 282
 283         /* If READ failed,
 284          * have it be pushed back to the retry work queue,
 285          * so it will re-enter __drbd_make_request(),
 286          * and be re-assigned to a suitable local or remote path,
 287          * or failed if we do not have access to good data anymore.
 288          *
 289          * Unless it was failed early by __drbd_make_request(),
 290          * because no path was available, in which case
 291          * it was not even added to the transfer_log.
 292          *
 293          * READA may fail, and will not be retried.
 294          *
 295          * WRITE should have used all available paths already.
 296          */
 297         if (!ok && rw == READ && !list_empty(&req->tl_requests))
 298                 req->rq_state |= RQ_POSTPONED;
 299
 300         if (!(req->rq_state & RQ_POSTPONED)) {
 301                 m->error = ok ? 0 : (error ?: -EIO);
 302                 m->bio = req->master_bio;
 303                 req->master_bio = NULL;
 304         }
 305 }
 306
 307 static int drbd_req_put_completion_ref(struct drbd_request *req, struct bio_and_error *m, int put)
 308 {
 309         struct drbd_device *device = req->device;
 310         D_ASSERT(device, m || (req->rq_state & RQ_POSTPONED));
 311
 312         if (!atomic_sub_and_test(put, &req->completion_ref))
 313                 return 0;
 314
 315         drbd_req_complete(req, m);
 316
 317         if (req->rq_state & RQ_POSTPONED) {
 318                 /* don't destroy the req object just yet,
 319                  * but queue it for retry */
 320                 drbd_restart_request(req);
 321                 return 0;
 322         }
 323
 324         return 1;
 325 }
 326
 327 /* I'd like this to be the only place that manipulates
 328  * req->completion_ref and req->kref. */
 329 static void mod_rq_state(struct drbd_request *req, struct bio_and_error *m,
 330                 int clear, int set)
 331 {
 332         struct drbd_device *device = req->device;
 333         unsigned s = req->rq_state;
 334         int c_put = 0;
 335         int k_put = 0;
 336
 337         if (drbd_suspended(device) && !((s | clear) & RQ_COMPLETION_SUSP))
 338                 set |= RQ_COMPLETION_SUSP;
 339
 340         /* apply */
 341
 342         req->rq_state &= ~clear;
 343         req->rq_state |= set;
 344
 345         /* no change? */
 346         if (req->rq_state == s)
 347                 return;
 348
 349         /* intent: get references */
 350
 351         if (!(s & RQ_LOCAL_PENDING) && (set & RQ_LOCAL_PENDING))
 352                 atomic_inc(&req->completion_ref);
 353
 354         if (!(s & RQ_NET_PENDING) && (set & RQ_NET_PENDING)) {
 355                 inc_ap_pending(device);
 356                 atomic_inc(&req->completion_ref);
 357         }
 358
 359         if (!(s & RQ_NET_QUEUED) && (set & RQ_NET_QUEUED))
 360                 atomic_inc(&req->completion_ref);
 361
 362         if (!(s & RQ_EXP_BARR_ACK) && (set & RQ_EXP_BARR_ACK))
 363                 kref_get(&req->kref); /* wait for the DONE */
 364
 365         if (!(s & RQ_NET_SENT) && (set & RQ_NET_SENT))
 366                 atomic_add(req->i.size >> 9, &device->ap_in_flight);
 367
 368         if (!(s & RQ_COMPLETION_SUSP) && (set & RQ_COMPLETION_SUSP))
 369                 atomic_inc(&req->completion_ref);
 370
 371         /* progress: put references */
 372
 373         if ((s & RQ_COMPLETION_SUSP) && (clear & RQ_COMPLETION_SUSP))
 374                 ++c_put;
 375
 376         if (!(s & RQ_LOCAL_ABORTED) && (set & RQ_LOCAL_ABORTED)) {
 377                 D_ASSERT(device, req->rq_state & RQ_LOCAL_PENDING);
 378                 /* local completion may still come in later,
 379                  * we need to keep the req object around. */
 380                 kref_get(&req->kref);
 381                 ++c_put;
 382         }
 383
 384         if ((s & RQ_LOCAL_PENDING) && (clear & RQ_LOCAL_PENDING)) {
 385                 if (req->rq_state & RQ_LOCAL_ABORTED)
 386                         ++k_put;
 387                 else
 388                         ++c_put;
 389         }
 390
 391         if ((s & RQ_NET_PENDING) && (clear & RQ_NET_PENDING)) {
 392                 dec_ap_pending(device);
 393                 ++c_put;
 394         }
 395
 396         if ((s & RQ_NET_QUEUED) && (clear & RQ_NET_QUEUED))
 397                 ++c_put;
 398
 399         if ((s & RQ_EXP_BARR_ACK) && !(s & RQ_NET_DONE) && (set & RQ_NET_DONE)) {
 400                 if (req->rq_state & RQ_NET_SENT)
 401                         atomic_sub(req->i.size >> 9, &device->ap_in_flight);
 402                 ++k_put;
 403         }
 404
 405         /* potentially complete and destroy */
 406
 407         if (k_put || c_put) {
 408                 /* Completion does it's own kref_put.  If we are going to
 409                  * kref_sub below, we need req to be still around then. */
 410                 int at_least = k_put + !!c_put;
 411                 int refcount = atomic_read(&req->kref.refcount);
 412                 if (refcount < at_least)
 413                         drbd_err(device,
 414                                 "mod_rq_state: Logic BUG: %x -> %x: refcount = %d, should be >= %d\n",
 415                                 s, req->rq_state, refcount, at_least);
 416         }
 417
 418         /* If we made progress, retry conflicting peer requests, if any. */
 419         if (req->i.waiting)
 420                 wake_up(&device->misc_wait);
 421
 422         if (c_put)
 423                 k_put += drbd_req_put_completion_ref(req, m, c_put);
 424         if (k_put)
 425                 kref_sub(&req->kref, k_put, drbd_req_destroy);
 426 }
 427
 428 static void drbd_report_io_error(struct drbd_device *device, struct drbd_request *req)
 429 {
 430         char b[BDEVNAME_SIZE];
 431
 432         if (!__ratelimit(&drbd_ratelimit_state))
 433                 return;
 434
 435         drbd_warn(device, "local %s IO error sector %llu+%u on %s\n",
 436                         (req->rq_state & RQ_WRITE) ? "WRITE" : "READ",
 437                         (unsigned long long)req->i.sector,
 438                         req->i.size >> 9,
 439                         bdevname(device->ldev->backing_bdev, b));
 440 }
 441
 442 /* obviously this could be coded as many single functions
 443  * instead of one huge switch,
 444  * or by putting the code directly in the respective locations
 445  * (as it has been before).
 446  *
 447  * but having it this way
 448  *  enforces that it is all in this one place, where it is easier to audit,
 449  *  it makes it obvious that whatever "event" "happens" to a request should
 450  *  happen "atomically" within the req_lock,
 451  *  and it enforces that we have to think in a very structured manner
 452  *  about the "events" that may happen to a request during its life time ...
 453  */
 454 int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 455                 struct bio_and_error *m)
 456 {
 457         struct drbd_device *device = req->device;
 458         struct net_conf *nc;
 459         int p, rv = 0;
 460
 461         if (m)
 462                 m->bio = NULL;
 463
 464         switch (what) {
 465         default:
 466                 drbd_err(device, "LOGIC BUG in %s:%u\n", __FILE__ , __LINE__);
 467                 break;
 468
 469         /* does not happen...
 470          * initialization done in drbd_req_new
 471         case CREATED:
 472                 break;
 473                 */
 474
 475         case TO_BE_SENT: /* via network */
 476                 /* reached via __drbd_make_request
 477                  * and from w_read_retry_remote */
 478                 D_ASSERT(device, !(req->rq_state & RQ_NET_MASK));
 479                 rcu_read_lock();
 480                 nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
 481                 p = nc->wire_protocol;
 482                 rcu_read_unlock();
 483                 req->rq_state |=
 484                         p == DRBD_PROT_C ? RQ_EXP_WRITE_ACK :
 485                         p == DRBD_PROT_B ? RQ_EXP_RECEIVE_ACK : 0;
 486                 mod_rq_state(req, m, 0, RQ_NET_PENDING);
 487                 break;
 488
 489         case TO_BE_SUBMITTED: /* locally */
 490                 /* reached via __drbd_make_request */
 491                 D_ASSERT(device, !(req->rq_state & RQ_LOCAL_MASK));
 492                 mod_rq_state(req, m, 0, RQ_LOCAL_PENDING);
 493                 break;
 494
 495         case COMPLETED_OK:
 496                 if (req->rq_state & RQ_WRITE)
 497                         device->writ_cnt += req->i.size >> 9;
 498                 else
 499                         device->read_cnt += req->i.size >> 9;
 500
 501                 mod_rq_state(req, m, RQ_LOCAL_PENDING,
 502                                 RQ_LOCAL_COMPLETED|RQ_LOCAL_OK);
 503                 break;
 504
 505         case ABORT_DISK_IO:
 506                 mod_rq_state(req, m, 0, RQ_LOCAL_ABORTED);
 507                 break;
 508
 509         case WRITE_COMPLETED_WITH_ERROR:
 510                 drbd_report_io_error(device, req);
 511                 __drbd_chk_io_error(device, DRBD_WRITE_ERROR);
 512                 mod_rq_state(req, m, RQ_LOCAL_PENDING, RQ_LOCAL_COMPLETED);
 513                 break;
 514
 515         case READ_COMPLETED_WITH_ERROR:
 516                 drbd_set_out_of_sync(device, req->i.sector, req->i.size);
 517                 drbd_report_io_error(device, req);
 518                 __drbd_chk_io_error(device, DRBD_READ_ERROR);
 519                 /* fall through. */
 520         case READ_AHEAD_COMPLETED_WITH_ERROR:
 521                 /* it is legal to fail READA, no __drbd_chk_io_error in that case. */
 522                 mod_rq_state(req, m, RQ_LOCAL_PENDING, RQ_LOCAL_COMPLETED);
 523                 break;
 524
 525         case DISCARD_COMPLETED_NOTSUPP:
 526         case DISCARD_COMPLETED_WITH_ERROR:
 527                 /* I'd rather not detach from local disk just because it
 528                  * failed a REQ_DISCARD. */
 529                 mod_rq_state(req, m, RQ_LOCAL_PENDING, RQ_LOCAL_COMPLETED);
 530                 break;
 531
 532         case QUEUE_FOR_NET_READ:
 533                 /* READ or READA, and
 534                  * no local disk,
 535                  * or target area marked as invalid,
 536                  * or just got an io-error. */
 537                 /* from __drbd_make_request
 538                  * or from bio_endio during read io-error recovery */
 539
 540                 /* So we can verify the handle in the answer packet.
 541                  * Corresponding drbd_remove_request_interval is in
 542                  * drbd_req_complete() */
 543                 D_ASSERT(device, drbd_interval_empty(&req->i));
 544                 drbd_insert_interval(&device->read_requests, &req->i);
 545
 546                 set_bit(UNPLUG_REMOTE, &device->flags);
 547
 548                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 549                 D_ASSERT(device, (req->rq_state & RQ_LOCAL_MASK) == 0);
 550                 mod_rq_state(req, m, 0, RQ_NET_QUEUED);
 551                 req->w.cb = w_send_read_req;
 552                 drbd_queue_work(&first_peer_device(device)->connection->sender_work,
 553                                 &req->w);
 554                 break;
 555
 556         case QUEUE_FOR_NET_WRITE:
 557                 /* assert something? */
 558                 /* from __drbd_make_request only */
 559
 560                 /* Corresponding drbd_remove_request_interval is in
 561                  * drbd_req_complete() */
 562                 D_ASSERT(device, drbd_interval_empty(&req->i));
 563                 drbd_insert_interval(&device->write_requests, &req->i);
 564
 565                 /* NOTE
 566                  * In case the req ended up on the transfer log before being
 567                  * queued on the worker, it could lead to this request being
 568                  * missed during cleanup after connection loss.
 569                  * So we have to do both operations here,
 570                  * within the same lock that protects the transfer log.
 571                  *
 572                  * _req_add_to_epoch(req); this has to be after the
 573                  * _maybe_start_new_epoch(req); which happened in
 574                  * __drbd_make_request, because we now may set the bit
 575                  * again ourselves to close the current epoch.
 576                  *
 577                  * Add req to the (now) current epoch (barrier). */
 578
 579                 /* otherwise we may lose an unplug, which may cause some remote
 580                  * io-scheduler timeout to expire, increasing maximum latency,
 581                  * hurting performance. */
 582                 set_bit(UNPLUG_REMOTE, &device->flags);
 583
 584                 /* queue work item to send data */
 585                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 586                 mod_rq_state(req, m, 0, RQ_NET_QUEUED|RQ_EXP_BARR_ACK);
 587                 req->w.cb =  w_send_dblock;
 588                 drbd_queue_work(&first_peer_device(device)->connection->sender_work,
 589                                 &req->w);
 590
 591                 /* close the epoch, in case it outgrew the limit */
 592                 rcu_read_lock();
 593                 nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
 594                 p = nc->max_epoch_size;
 595                 rcu_read_unlock();
 596                 if (first_peer_device(device)->connection->current_tle_writes >= p)
 597                         start_new_tl_epoch(first_peer_device(device)->connection);
 598
 599                 break;
 600
 601         case QUEUE_FOR_SEND_OOS:
 602                 mod_rq_state(req, m, 0, RQ_NET_QUEUED);
 603                 req->w.cb =  w_send_out_of_sync;
 604                 drbd_queue_work(&first_peer_device(device)->connection->sender_work,
 605                                 &req->w);
 606                 break;
 607
 608         case READ_RETRY_REMOTE_CANCELED:
 609         case SEND_CANCELED:
 610         case SEND_FAILED:
 611                 /* real cleanup will be done from tl_clear.  just update flags
 612                  * so it is no longer marked as on the worker queue */
 613                 mod_rq_state(req, m, RQ_NET_QUEUED, 0);
 614                 break;
 615
 616         case HANDED_OVER_TO_NETWORK:
 617                 /* assert something? */
 618                 if (bio_data_dir(req->master_bio) == WRITE &&
 619                     !(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK))) {
 620                         /* this is what is dangerous about protocol A:
 621                          * pretend it was successfully written on the peer. */
 622                         if (req->rq_state & RQ_NET_PENDING)
 623                                 mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK);
 624                         /* else: neg-ack was faster... */
 625                         /* it is still not yet RQ_NET_DONE until the
 626                          * corresponding epoch barrier got acked as well,
 627                          * so we know what to dirty on connection loss */
 628                 }
 629                 mod_rq_state(req, m, RQ_NET_QUEUED, RQ_NET_SENT);
 630                 break;
 631
 632         case OOS_HANDED_TO_NETWORK:
 633                 /* Was not set PENDING, no longer QUEUED, so is now DONE
 634                  * as far as this connection is concerned. */
 635                 mod_rq_state(req, m, RQ_NET_QUEUED, RQ_NET_DONE);
 636                 break;
 637
 638         case CONNECTION_LOST_WHILE_PENDING:
 639                 /* transfer log cleanup after connection loss */
 640                 mod_rq_state(req, m,
 641                                 RQ_NET_OK|RQ_NET_PENDING|RQ_COMPLETION_SUSP,
 642                                 RQ_NET_DONE);
 643                 break;
 644
 645         case CONFLICT_RESOLVED:
 646                 /* for superseded conflicting writes of multiple primaries,
 647                  * there is no need to keep anything in the tl, potential
 648                  * node crashes are covered by the activity log.
 649                  *
 650                  * If this request had been marked as RQ_POSTPONED before,
 651                  * it will actually not be completed, but "restarted",
 652                  * resubmitted from the retry worker context. */
 653                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 654                 D_ASSERT(device, req->rq_state & RQ_EXP_WRITE_ACK);
 655                 mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_DONE|RQ_NET_OK);
 656                 break;
 657
 658         case WRITE_ACKED_BY_PEER_AND_SIS:
 659                 req->rq_state |= RQ_NET_SIS;
 660         case WRITE_ACKED_BY_PEER:
 661                 D_ASSERT(device, req->rq_state & RQ_EXP_WRITE_ACK);
 662                 /* protocol C; successfully written on peer.
 663                  * Nothing more to do here.
 664                  * We want to keep the tl in place for all protocols, to cater
 665                  * for volatile write-back caches on lower level devices. */
 666
 667                 goto ack_common;
 668         case RECV_ACKED_BY_PEER:
 669                 D_ASSERT(device, req->rq_state & RQ_EXP_RECEIVE_ACK);
 670                 /* protocol B; pretends to be successfully written on peer.
 671                  * see also notes above in HANDED_OVER_TO_NETWORK about
 672                  * protocol != C */
 673         ack_common:
 674                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 675                 mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK);
 676                 break;
 677
 678         case POSTPONE_WRITE:
 679                 D_ASSERT(device, req->rq_state & RQ_EXP_WRITE_ACK);
 680                 /* If this node has already detected the write conflict, the
 681                  * worker will be waiting on misc_wait.  Wake it up once this
 682                  * request has completed locally.
 683                  */
 684                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 685                 req->rq_state |= RQ_POSTPONED;
 686                 if (req->i.waiting)
 687                         wake_up(&device->misc_wait);
 688                 /* Do not clear RQ_NET_PENDING. This request will make further
 689                  * progress via restart_conflicting_writes() or
 690                  * fail_postponed_requests(). Hopefully. */
 691                 break;
 692
 693         case NEG_ACKED:
 694                 mod_rq_state(req, m, RQ_NET_OK|RQ_NET_PENDING, 0);
 695                 break;
 696
 697         case FAIL_FROZEN_DISK_IO:
 698                 if (!(req->rq_state & RQ_LOCAL_COMPLETED))
 699                         break;
 700                 mod_rq_state(req, m, RQ_COMPLETION_SUSP, 0);
 701                 break;
 702
 703         case RESTART_FROZEN_DISK_IO:
 704                 if (!(req->rq_state & RQ_LOCAL_COMPLETED))
 705                         break;
 706
 707                 mod_rq_state(req, m,
 708                                 RQ_COMPLETION_SUSP|RQ_LOCAL_COMPLETED,
 709                                 RQ_LOCAL_PENDING);
 710
 711                 rv = MR_READ;
 712                 if (bio_data_dir(req->master_bio) == WRITE)
 713                         rv = MR_WRITE;
 714
 715                 get_ldev(device); /* always succeeds in this call path */
 716                 req->w.cb = w_restart_disk_io;
 717                 drbd_queue_work(&first_peer_device(device)->connection->sender_work,
 718                                 &req->w);
 719                 break;
 720
 721         case RESEND:
 722                 /* Simply complete (local only) READs. */
 723                 if (!(req->rq_state & RQ_WRITE) && !req->w.cb) {
 724                         mod_rq_state(req, m, RQ_COMPLETION_SUSP, 0);
 725                         break;
 726                 }
 727
 728                 /* If RQ_NET_OK is already set, we got a P_WRITE_ACK or P_RECV_ACK
 729                    before the connection loss (B&C only); only P_BARRIER_ACK
 730                    (or the local completion?) was missing when we suspended.
 731                    Throwing them out of the TL here by pretending we got a BARRIER_ACK.
 732                    During connection handshake, we ensure that the peer was not rebooted. */
 733                 if (!(req->rq_state & RQ_NET_OK)) {
 734                         /* FIXME could this possibly be a req->dw.cb == w_send_out_of_sync?
 735                          * in that case we must not set RQ_NET_PENDING. */
 736
 737                         mod_rq_state(req, m, RQ_COMPLETION_SUSP, RQ_NET_QUEUED|RQ_NET_PENDING);
 738                         if (req->w.cb) {
 739                                 drbd_queue_work(&first_peer_device(device)->connection->sender_work,
 740                                                 &req->w);
 741                                 rv = req->rq_state & RQ_WRITE ? MR_WRITE : MR_READ;
 742                         } /* else: FIXME can this happen? */
 743                         break;
 744                 }
 745                 /* else, fall through to BARRIER_ACKED */
 746
 747         case BARRIER_ACKED:
 748                 /* barrier ack for READ requests does not make sense */
 749                 if (!(req->rq_state & RQ_WRITE))
 750                         break;
 751
 752                 if (req->rq_state & RQ_NET_PENDING) {
 753                         /* barrier came in before all requests were acked.
 754                          * this is bad, because if the connection is lost now,
 755                          * we won't be able to clean them up... */
 756                         drbd_err(device, "FIXME (BARRIER_ACKED but pending)\n");
 757                 }
 758                 /* Allowed to complete requests, even while suspended.
 759                  * As this is called for all requests within a matching epoch,
 760                  * we need to filter, and only set RQ_NET_DONE for those that
 761                  * have actually been on the wire. */
 762                 mod_rq_state(req, m, RQ_COMPLETION_SUSP,
 763                                 (req->rq_state & RQ_NET_MASK) ? RQ_NET_DONE : 0);
 764                 break;
 765
 766         case DATA_RECEIVED:
 767                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 768                 mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK|RQ_NET_DONE);
 769                 break;
 770
 771         case QUEUE_AS_DRBD_BARRIER:
 772                 start_new_tl_epoch(first_peer_device(device)->connection);
 773                 mod_rq_state(req, m, 0, RQ_NET_OK|RQ_NET_DONE);
 774                 break;
 775         };
 776
 777         return rv;
 778 }
 779
 780 /* we may do a local read if:
 781  * - we are consistent (of course),
 782  * - or we are generally inconsistent,
 783  *   BUT we are still/already IN SYNC for this area.
 784  *   since size may be bigger than BM_BLOCK_SIZE,
 785  *   we may need to check several bits.
 786  */
 787 static bool drbd_may_do_local_read(struct drbd_device *device, sector_t sector, int size)
 788 {
 789         unsigned long sbnr, ebnr;
 790         sector_t esector, nr_sectors;
 791
 792         if (device->state.disk == D_UP_TO_DATE)
 793                 return true;
 794         if (device->state.disk != D_INCONSISTENT)
 795                 return false;
 796         esector = sector + (size >> 9) - 1;
 797         nr_sectors = drbd_get_capacity(device->this_bdev);
 798         D_ASSERT(device, sector  < nr_sectors);
 799         D_ASSERT(device, esector < nr_sectors);
 800
 801         sbnr = BM_SECT_TO_BIT(sector);
 802         ebnr = BM_SECT_TO_BIT(esector);
 803
 804         return drbd_bm_count_bits(device, sbnr, ebnr) == 0;
 805 }
 806
 807 static bool remote_due_to_read_balancing(struct drbd_device *device, sector_t sector,
 808                 enum drbd_read_balancing rbm)
 809 {
 810         struct backing_dev_info *bdi;
 811         int stripe_shift;
 812
 813         switch (rbm) {
 814         case RB_CONGESTED_REMOTE:
 815                 bdi = &device->ldev->backing_bdev->bd_disk->queue->backing_dev_info;
 816                 return bdi_read_congested(bdi);
 817         case RB_LEAST_PENDING:
 818                 return atomic_read(&device->local_cnt) >
 819                         atomic_read(&device->ap_pending_cnt) + atomic_read(&device->rs_pending_cnt);
 820         case RB_32K_STRIPING:  /* stripe_shift = 15 */
 821         case RB_64K_STRIPING:
 822         case RB_128K_STRIPING:
 823         case RB_256K_STRIPING:
 824         case RB_512K_STRIPING:
 825         case RB_1M_STRIPING:   /* stripe_shift = 20 */
 826                 stripe_shift = (rbm - RB_32K_STRIPING + 15);
 827                 return (sector >> (stripe_shift - 9)) & 1;
 828         case RB_ROUND_ROBIN:
 829                 return test_and_change_bit(READ_BALANCE_RR, &device->flags);
 830         case RB_PREFER_REMOTE:
 831                 return true;
 832         case RB_PREFER_LOCAL:
 833         default:
 834                 return false;
 835         }
 836 }
 837
 838 /*
 839  * complete_conflicting_writes  -  wait for any conflicting write requests
 840  *
 841  * The write_requests tree contains all active write requests which we
 842  * currently know about.  Wait for any requests to complete which conflict with
 843  * the new one.
 844  *
 845  * Only way out: remove the conflicting intervals from the tree.
 846  */
 847 static void complete_conflicting_writes(struct drbd_request *req)
 848 {
 849         DEFINE_WAIT(wait);
 850         struct drbd_device *device = req->device;
 851         struct drbd_interval *i;
 852         sector_t sector = req->i.sector;
 853         int size = req->i.size;
 854
 855         i = drbd_find_overlap(&device->write_requests, sector, size);
 856         if (!i)
 857                 return;
 858
 859         for (;;) {
 860                 prepare_to_wait(&device->misc_wait, &wait, TASK_UNINTERRUPTIBLE);
 861                 i = drbd_find_overlap(&device->write_requests, sector, size);
 862                 if (!i)
 863                         break;
 864                 /* Indicate to wake up device->misc_wait on progress.  */
 865                 i->waiting = true;
 866                 spin_unlock_irq(&device->resource->req_lock);
 867                 schedule();
 868                 spin_lock_irq(&device->resource->req_lock);
 869         }
 870         finish_wait(&device->misc_wait, &wait);
 871 }
 872
 873 /* called within req_lock and rcu_read_lock() */
 874 static void maybe_pull_ahead(struct drbd_device *device)
 875 {
 876         struct drbd_connection *connection = first_peer_device(device)->connection;
 877         struct net_conf *nc;
 878         bool congested = false;
 879         enum drbd_on_congestion on_congestion;
 880
 881         rcu_read_lock();
 882         nc = rcu_dereference(connection->net_conf);
 883         on_congestion = nc ? nc->on_congestion : OC_BLOCK;
 884         rcu_read_unlock();
 885         if (on_congestion == OC_BLOCK ||
 886             connection->agreed_pro_version < 96)
 887                 return;
 888
 889         /* If I don't even have good local storage, we can not reasonably try
 890          * to pull ahead of the peer. We also need the local reference to make
 891          * sure device->act_log is there.
 892          */
 893         if (!get_ldev_if_state(device, D_UP_TO_DATE))
 894                 return;
 895
 896         if (nc->cong_fill &&
 897             atomic_read(&device->ap_in_flight) >= nc->cong_fill) {
 898                 drbd_info(device, "Congestion-fill threshold reached\n");
 899                 congested = true;
 900         }
 901
 902         if (device->act_log->used >= nc->cong_extents) {
 903                 drbd_info(device, "Congestion-extents threshold reached\n");
 904                 congested = true;
 905         }
 906
 907         if (congested) {
 908                 /* start a new epoch for non-mirrored writes */
 909                 start_new_tl_epoch(first_peer_device(device)->connection);
 910
 911                 if (on_congestion == OC_PULL_AHEAD)
 912                         _drbd_set_state(_NS(device, conn, C_AHEAD), 0, NULL);
 913                 else  /*nc->on_congestion == OC_DISCONNECT */
 914                         _drbd_set_state(_NS(device, conn, C_DISCONNECTING), 0, NULL);
 915         }
 916         put_ldev(device);
 917 }
 918
 919 /* If this returns false, and req->private_bio is still set,
 920  * this should be submitted locally.
 921  *
 922  * If it returns false, but req->private_bio is not set,
 923  * we do not have access to good data :(
 924  *
 925  * Otherwise, this destroys req->private_bio, if any,
 926  * and returns true.
 927  */
 928 static bool do_remote_read(struct drbd_request *req)
 929 {
 930         struct drbd_device *device = req->device;
 931         enum drbd_read_balancing rbm;
 932
 933         if (req->private_bio) {
 934                 if (!drbd_may_do_local_read(device,
 935                                         req->i.sector, req->i.size)) {
 936                         bio_put(req->private_bio);
 937                         req->private_bio = NULL;
 938                         put_ldev(device);
 939                 }
 940         }
 941
 942         if (device->state.pdsk != D_UP_TO_DATE)
 943                 return false;
 944
 945         if (req->private_bio == NULL)
 946                 return true;
 947
 948         /* TODO: improve read balancing decisions, take into account drbd
 949          * protocol, pending requests etc. */
 950
 951         rcu_read_lock();
 952         rbm = rcu_dereference(device->ldev->disk_conf)->read_balancing;
 953         rcu_read_unlock();
 954
 955         if (rbm == RB_PREFER_LOCAL && req->private_bio)
 956                 return false; /* submit locally */
 957
 958         if (remote_due_to_read_balancing(device, req->i.sector, rbm)) {
 959                 if (req->private_bio) {
 960                         bio_put(req->private_bio);
 961                         req->private_bio = NULL;
 962                         put_ldev(device);
 963                 }
 964                 return true;
 965         }
 966
 967         return false;
 968 }
 969
 970 /* returns number of connections (== 1, for drbd 8.4)
 971  * expected to actually write this data,
 972  * which does NOT include those that we are L_AHEAD for. */
 973 static int drbd_process_write_request(struct drbd_request *req)
 974 {
 975         struct drbd_device *device = req->device;
 976         int remote, send_oos;
 977
 978         remote = drbd_should_do_remote(device->state);
 979         send_oos = drbd_should_send_out_of_sync(device->state);
 980
 981         /* Need to replicate writes.  Unless it is an empty flush,
 982          * which is better mapped to a DRBD P_BARRIER packet,
 983          * also for drbd wire protocol compatibility reasons.
 984          * If this was a flush, just start a new epoch.
 985          * Unless the current epoch was empty anyways, or we are not currently
 986          * replicating, in which case there is no point. */
 987         if (unlikely(req->i.size == 0)) {
 988                 /* The only size==0 bios we expect are empty flushes. */
 989                 D_ASSERT(device, req->master_bio->bi_rw & REQ_FLUSH);
 990                 if (remote)
 991                         _req_mod(req, QUEUE_AS_DRBD_BARRIER);
 992                 return remote;
 993         }
 994
 995         if (!remote && !send_oos)
 996                 return 0;
 997
 998         D_ASSERT(device, !(remote && send_oos));
 999
1000         if (remote) {
1001                 _req_mod(req, TO_BE_SENT);
1002                 _req_mod(req, QUEUE_FOR_NET_WRITE);
1003         } else if (drbd_set_out_of_sync(device, req->i.sector, req->i.size))
1004                 _req_mod(req, QUEUE_FOR_SEND_OOS);
1005
1006         return remote;
1007 }
1008
1009 static void
1010 drbd_submit_req_private_bio(struct drbd_request *req)
1011 {
1012         struct drbd_device *device = req->device;
1013         struct bio *bio = req->private_bio;
1014         const int rw = bio_rw(bio);
1015
1016         bio->bi_bdev = device->ldev->backing_bdev;
1017
1018         /* State may have changed since we grabbed our reference on the
1019          * ->ldev member. Double check, and short-circuit to endio.
1020          * In case the last activity log transaction failed to get on
1021          * stable storage, and this is a WRITE, we may not even submit
1022          * this bio. */
1023         if (get_ldev(device)) {
1024                 if (drbd_insert_fault(device,
1025                                       rw == WRITE ? DRBD_FAULT_DT_WR
1026                                     : rw == READ  ? DRBD_FAULT_DT_RD
1027                                     :               DRBD_FAULT_DT_RA))
1028                         bio_endio(bio, -EIO);
1029                 else
1030                         generic_make_request(bio);
1031                 put_ldev(device);
1032         } else
1033                 bio_endio(bio, -EIO);
1034 }
1035
1036 static void drbd_queue_write(struct drbd_device *device, struct drbd_request *req)
1037 {
1038         spin_lock(&device->submit.lock);
1039         list_add_tail(&req->tl_requests, &device->submit.writes);
1040         spin_unlock(&device->submit.lock);
1041         queue_work(device->submit.wq, &device->submit.worker);
1042 }
1043
1044 /* returns the new drbd_request pointer, if the caller is expected to
1045  * drbd_send_and_submit() it (to save latency), or NULL if we queued the
1046  * request on the submitter thread.
1047  * Returns ERR_PTR(-ENOMEM) if we cannot allocate a drbd_request.
1048  */
1049 static struct drbd_request *
1050 drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long start_time)
1051 {
1052         const int rw = bio_data_dir(bio);
1053         struct drbd_request *req;
1054
1055         /* allocate outside of all locks; */
1056         req = drbd_req_new(device, bio);
1057         if (!req) {
1058                 dec_ap_bio(device);
1059                 /* only pass the error to the upper layers.
1060                  * if user cannot handle io errors, that's not our business. */
1061                 drbd_err(device, "could not kmalloc() req\n");
1062                 bio_endio(bio, -ENOMEM);
1063                 return ERR_PTR(-ENOMEM);
1064         }
1065         req->start_time = start_time;
1066
1067         if (!get_ldev(device)) {
1068                 bio_put(req->private_bio);
1069                 req->private_bio = NULL;
1070         }
1071
1072         /* Update disk stats */
1073         _drbd_start_io_acct(device, req);
1074
1075         if (rw == WRITE && req->private_bio && req->i.size
1076         && !test_bit(AL_SUSPENDED, &device->flags)) {
1077                 if (!drbd_al_begin_io_fastpath(device, &req->i)) {
1078                         drbd_queue_write(device, req);
1079                         return NULL;
1080                 }
1081                 req->rq_state |= RQ_IN_ACT_LOG;
1082         }
1083
1084         return req;
1085 }
1086
1087 static void drbd_send_and_submit(struct drbd_device *device, struct drbd_request *req)
1088 {
1089         const int rw = bio_rw(req->master_bio);
1090         struct bio_and_error m = { NULL, };
1091         bool no_remote = false;
1092
1093         spin_lock_irq(&device->resource->req_lock);
1094         if (rw == WRITE) {
1095                 /* This may temporarily give up the req_lock,
1096                  * but will re-aquire it before it returns here.
1097                  * Needs to be before the check on drbd_suspended() */
1098                 complete_conflicting_writes(req);
1099                 /* no more giving up req_lock from now on! */
1100
1101                 /* check for congestion, and potentially stop sending
1102                  * full data updates, but start sending "dirty bits" only. */
1103                 maybe_pull_ahead(device);
1104         }
1105
1106
1107         if (drbd_suspended(device)) {
1108                 /* push back and retry: */
1109                 req->rq_state |= RQ_POSTPONED;
1110                 if (req->private_bio) {
1111                         bio_put(req->private_bio);
1112                         req->private_bio = NULL;
1113                         put_ldev(device);
1114                 }
1115                 goto out;
1116         }
1117
1118         /* We fail READ/READA early, if we can not serve it.
1119          * We must do this before req is registered on any lists.
1120          * Otherwise, drbd_req_complete() will queue failed READ for retry. */
1121         if (rw != WRITE) {
1122                 if (!do_remote_read(req) && !req->private_bio)
1123                         goto nodata;
1124         }
1125
1126         /* which transfer log epoch does this belong to? */
1127         req->epoch = atomic_read(&first_peer_device(device)->connection->current_tle_nr);
1128
1129         /* no point in adding empty flushes to the transfer log,
1130          * they are mapped to drbd barriers already. */
1131         if (likely(req->i.size!=0)) {
1132                 if (rw == WRITE)
1133                         first_peer_device(device)->connection->current_tle_writes++;
1134
1135                 list_add_tail(&req->tl_requests, &first_peer_device(device)->connection->transfer_log);
1136         }
1137
1138         if (rw == WRITE) {
1139                 if (!drbd_process_write_request(req))
1140                         no_remote = true;
1141         } else {
1142                 /* We either have a private_bio, or we can read from remote.
1143                  * Otherwise we had done the goto nodata above. */
1144                 if (req->private_bio == NULL) {
1145                         _req_mod(req, TO_BE_SENT);
1146                         _req_mod(req, QUEUE_FOR_NET_READ);
1147                 } else
1148                         no_remote = true;
1149         }
1150
1151         if (req->private_bio) {
1152                 /* needs to be marked within the same spinlock */
1153                 _req_mod(req, TO_BE_SUBMITTED);
1154                 /* but we need to give up the spinlock to submit */
1155                 spin_unlock_irq(&device->resource->req_lock);
1156                 drbd_submit_req_private_bio(req);
1157                 spin_lock_irq(&device->resource->req_lock);
1158         } else if (no_remote) {
1159 nodata:
1160                 if (__ratelimit(&drbd_ratelimit_state))
1161                         drbd_err(device, "IO ERROR: neither local nor remote data, sector %llu+%u\n",
1162                                         (unsigned long long)req->i.sector, req->i.size >> 9);
1163                 /* A write may have been queued for send_oos, however.
1164                  * So we can not simply free it, we must go through drbd_req_put_completion_ref() */
1165         }
1166
1167 out:
1168         if (drbd_req_put_completion_ref(req, &m, 1))
1169                 kref_put(&req->kref, drbd_req_destroy);
1170         spin_unlock_irq(&device->resource->req_lock);
1171
1172         if (m.bio)
1173                 complete_master_bio(device, &m);
1174 }
1175
1176 void __drbd_make_request(struct drbd_device *device, struct bio *bio, unsigned long start_time)
1177 {
1178         struct drbd_request *req = drbd_request_prepare(device, bio, start_time);
1179         if (IS_ERR_OR_NULL(req))
1180                 return;
1181         drbd_send_and_submit(device, req);
1182 }
1183
1184 static void submit_fast_path(struct drbd_device *device, struct list_head *incoming)
1185 {
1186         struct drbd_request *req, *tmp;
1187         list_for_each_entry_safe(req, tmp, incoming, tl_requests) {
1188                 const int rw = bio_data_dir(req->master_bio);
1189
1190                 if (rw == WRITE /* rw != WRITE should not even end up here! */
1191                 && req->private_bio && req->i.size
1192                 && !test_bit(AL_SUSPENDED, &device->flags)) {
1193                         if (!drbd_al_begin_io_fastpath(device, &req->i))
1194                                 continue;
1195
1196                         req->rq_state |= RQ_IN_ACT_LOG;
1197                 }
1198
1199                 list_del_init(&req->tl_requests);
1200                 drbd_send_and_submit(device, req);
1201         }
1202 }
1203
1204 static bool prepare_al_transaction_nonblock(struct drbd_device *device,
1205                                             struct list_head *incoming,
1206                                             struct list_head *pending)
1207 {
1208         struct drbd_request *req, *tmp;
1209         int wake = 0;
1210         int err;
1211
1212         spin_lock_irq(&device->al_lock);
1213         list_for_each_entry_safe(req, tmp, incoming, tl_requests) {
1214                 err = drbd_al_begin_io_nonblock(device, &req->i);
1215                 if (err == -EBUSY)
1216                         wake = 1;
1217                 if (err)
1218                         continue;
1219                 req->rq_state |= RQ_IN_ACT_LOG;
1220                 list_move_tail(&req->tl_requests, pending);
1221         }
1222         spin_unlock_irq(&device->al_lock);
1223         if (wake)
1224                 wake_up(&device->al_wait);
1225
1226         return !list_empty(pending);
1227 }
1228
1229 void do_submit(struct work_struct *ws)
1230 {
1231         struct drbd_device *device = container_of(ws, struct drbd_device, submit.worker);
1232         LIST_HEAD(incoming);
1233         LIST_HEAD(pending);
1234         struct drbd_request *req, *tmp;
1235
1236         for (;;) {
1237                 spin_lock(&device->submit.lock);
1238                 list_splice_tail_init(&device->submit.writes, &incoming);
1239                 spin_unlock(&device->submit.lock);
1240
1241                 submit_fast_path(device, &incoming);
1242                 if (list_empty(&incoming))
1243                         break;
1244
1245 skip_fast_path:
1246                 wait_event(device->al_wait, prepare_al_transaction_nonblock(device, &incoming, &pending));
1247                 /* Maybe more was queued, while we prepared the transaction?
1248                  * Try to stuff them into this transaction as well.
1249                  * Be strictly non-blocking here, no wait_event, we already
1250                  * have something to commit.
1251                  * Stop if we don't make any more progres.
1252                  */
1253                 for (;;) {
1254                         LIST_HEAD(more_pending);
1255                         LIST_HEAD(more_incoming);
1256                         bool made_progress;
1257
1258                         /* It is ok to look outside the lock,
1259                          * it's only an optimization anyways */
1260                         if (list_empty(&device->submit.writes))
1261                                 break;
1262
1263                         spin_lock(&device->submit.lock);
1264                         list_splice_tail_init(&device->submit.writes, &more_incoming);
1265                         spin_unlock(&device->submit.lock);
1266
1267                         if (list_empty(&more_incoming))
1268                                 break;
1269
1270                         made_progress = prepare_al_transaction_nonblock(device, &more_incoming, &more_pending);
1271
1272                         list_splice_tail_init(&more_pending, &pending);
1273                         list_splice_tail_init(&more_incoming, &incoming);
1274
1275                         if (!made_progress)
1276                                 break;
1277                 }
1278                 drbd_al_begin_io_commit(device, false);
1279
1280                 list_for_each_entry_safe(req, tmp, &pending, tl_requests) {
1281                         list_del_init(&req->tl_requests);
1282                         drbd_send_and_submit(device, req);
1283                 }
1284
1285                 /* If all currently hot activity log extents are kept busy by
1286                  * incoming requests, we still must not totally starve new
1287                  * requests to cold extents. In that case, prepare one request
1288                  * in blocking mode. */
1289                 list_for_each_entry_safe(req, tmp, &incoming, tl_requests) {
1290                         list_del_init(&req->tl_requests);
1291                         req->rq_state |= RQ_IN_ACT_LOG;
1292                         if (!drbd_al_begin_io_prepare(device, &req->i)) {
1293                                 /* Corresponding extent was hot after all? */
1294                                 drbd_send_and_submit(device, req);
1295                         } else {
1296                                 /* Found a request to a cold extent.
1297                                  * Put on "pending" list,
1298                                  * and try to cumulate with more. */
1299                                 list_add(&req->tl_requests, &pending);
1300                                 goto skip_fast_path;
1301                         }
1302                 }
1303         }
1304 }
1305
1306 void drbd_make_request(struct request_queue *q, struct bio *bio)
1307 {
1308         struct drbd_device *device = (struct drbd_device *) q->queuedata;
1309         unsigned long start_time;
1310
1311         start_time = jiffies;
1312
1313         /*
1314          * what we "blindly" assume:
1315          */
1316         D_ASSERT(device, IS_ALIGNED(bio->bi_iter.bi_size, 512));
1317
1318         inc_ap_bio(device);
1319         __drbd_make_request(device, bio, start_time);
1320 }
1321
1322 /* This is called by bio_add_page().
1323  *
1324  * q->max_hw_sectors and other global limits are already enforced there.
1325  *
1326  * We need to call down to our lower level device,
1327  * in case it has special restrictions.
1328  *
1329  * We also may need to enforce configured max-bio-bvecs limits.
1330  *
1331  * As long as the BIO is empty we have to allow at least one bvec,
1332  * regardless of size and offset, so no need to ask lower levels.
1333  */
1334 int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec)
1335 {
1336         struct drbd_device *device = (struct drbd_device *) q->queuedata;
1337         unsigned int bio_size = bvm->bi_size;
1338         int limit = DRBD_MAX_BIO_SIZE;
1339         int backing_limit;
1340
1341         if (bio_size && get_ldev(device)) {
1342                 unsigned int max_hw_sectors = queue_max_hw_sectors(q);
1343                 struct request_queue * const b =
1344                         device->ldev->backing_bdev->bd_disk->queue;
1345                 if (b->merge_bvec_fn) {
1346                         backing_limit = b->merge_bvec_fn(b, bvm, bvec);
1347                         limit = min(limit, backing_limit);
1348                 }
1349                 put_ldev(device);
1350                 if ((limit >> 9) > max_hw_sectors)
1351                         limit = max_hw_sectors << 9;
1352         }
1353         return limit;
1354 }
1355
1356 static void find_oldest_requests(
1357                 struct drbd_connection *connection,
1358                 struct drbd_device *device,
1359                 struct drbd_request **oldest_req_waiting_for_peer,
1360                 struct drbd_request **oldest_req_waiting_for_disk)
1361 {
1362         struct drbd_request *r;
1363         *oldest_req_waiting_for_peer = NULL;
1364         *oldest_req_waiting_for_disk = NULL;
1365         list_for_each_entry(r, &connection->transfer_log, tl_requests) {
1366                 const unsigned s = r->rq_state;
1367                 if (!*oldest_req_waiting_for_peer
1368                 && ((s & RQ_NET_MASK) && !(s & RQ_NET_DONE)))
1369                         *oldest_req_waiting_for_peer = r;
1370
1371                 if (!*oldest_req_waiting_for_disk
1372                 && (s & RQ_LOCAL_PENDING) && r->device == device)
1373                         *oldest_req_waiting_for_disk = r;
1374
1375                 if (*oldest_req_waiting_for_peer && *oldest_req_waiting_for_disk)
1376                         break;
1377         }
1378 }
1379
1380 void request_timer_fn(unsigned long data)
1381 {
1382         struct drbd_device *device = (struct drbd_device *) data;
1383         struct drbd_connection *connection = first_peer_device(device)->connection;
1384         struct drbd_request *req_disk, *req_peer; /* oldest request */
1385         struct net_conf *nc;
1386         unsigned long ent = 0, dt = 0, et, nt; /* effective timeout = ko_count * timeout */
1387         unsigned long now;
1388
1389         rcu_read_lock();
1390         nc = rcu_dereference(connection->net_conf);
1391         if (nc && device->state.conn >= C_WF_REPORT_PARAMS)
1392                 ent = nc->timeout * HZ/10 * nc->ko_count;
1393
1394         if (get_ldev(device)) { /* implicit state.disk >= D_INCONSISTENT */
1395                 dt = rcu_dereference(device->ldev->disk_conf)->disk_timeout * HZ / 10;
1396                 put_ldev(device);
1397         }
1398         rcu_read_unlock();
1399
1400         et = min_not_zero(dt, ent);
1401
1402         if (!et)
1403                 return; /* Recurring timer stopped */
1404
1405         now = jiffies;
1406
1407         spin_lock_irq(&device->resource->req_lock);
1408         find_oldest_requests(connection, device, &req_peer, &req_disk);
1409         if (req_peer == NULL && req_disk == NULL) {
1410                 spin_unlock_irq(&device->resource->req_lock);
1411                 mod_timer(&device->request_timer, now + et);
1412                 return;
1413         }
1414
1415         /* The request is considered timed out, if
1416          * - we have some effective timeout from the configuration,
1417          *   with above state restrictions applied,
1418          * - the oldest request is waiting for a response from the network
1419          *   resp. the local disk,
1420          * - the oldest request is in fact older than the effective timeout,
1421          * - the connection was established (resp. disk was attached)
1422          *   for longer than the timeout already.
1423          * Note that for 32bit jiffies and very stable connections/disks,
1424          * we may have a wrap around, which is catched by
1425          *   !time_in_range(now, last_..._jif, last_..._jif + timeout).
1426          *
1427          * Side effect: once per 32bit wrap-around interval, which means every
1428          * ~198 days with 250 HZ, we have a window where the timeout would need
1429          * to expire twice (worst case) to become effective. Good enough.
1430          */
1431         if (ent && req_peer &&
1432                  time_after(now, req_peer->start_time + ent) &&
1433                 !time_in_range(now, connection->last_reconnect_jif, connection->last_reconnect_jif + ent)) {
1434                 drbd_warn(device, "Remote failed to finish a request within ko-count * timeout\n");
1435                 _drbd_set_state(_NS(device, conn, C_TIMEOUT), CS_VERBOSE | CS_HARD, NULL);
1436         }
1437         if (dt && req_disk &&
1438                  time_after(now, req_disk->start_time + dt) &&
1439                 !time_in_range(now, device->last_reattach_jif, device->last_reattach_jif + dt)) {
1440                 drbd_warn(device, "Local backing device failed to meet the disk-timeout\n");
1441                 __drbd_chk_io_error(device, DRBD_FORCE_DETACH);
1442         }
1443
1444         /* Reschedule timer for the nearest not already expired timeout.
1445          * Fallback to now + min(effective network timeout, disk timeout). */
1446         ent = (ent && req_peer && time_before(now, req_peer->start_time + ent))
1447                 ? req_peer->start_time + ent : now + et;
1448         dt = (dt && req_disk && time_before(now, req_disk->start_time + dt))
1449                 ? req_disk->start_time + dt : now + et;
1450         nt = time_before(ent, dt) ? ent : dt;
1451         spin_unlock_irq(&connection->resource->req_lock);
1452         mod_timer(&device->request_timer, nt);
1453 }