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         struct request_queue *q = device->rq_queue;
  40
  41         generic_start_io_acct(q, bio_data_dir(req->master_bio),
  42                                 req->i.size >> 9, &device->vdisk->part0);
  43 }
  44
  45 /* Update disk stats when completing request upwards */
  46 static void _drbd_end_io_acct(struct drbd_device *device, struct drbd_request *req)
  47 {
  48         struct request_queue *q = device->rq_queue;
  49
  50         generic_end_io_acct(q, bio_data_dir(req->master_bio),
  51                             &device->vdisk->part0, req->start_jif);
  52 }
  53
  54 static struct drbd_request *drbd_req_new(struct drbd_device *device, struct bio *bio_src)
  55 {
  56         struct drbd_request *req;
  57
  58         req = mempool_alloc(drbd_request_mempool, GFP_NOIO);
  59         if (!req)
  60                 return NULL;
  61         memset(req, 0, sizeof(*req));
  62
  63         drbd_req_make_private_bio(req, bio_src);
  64         req->rq_state = (bio_data_dir(bio_src) == WRITE ? RQ_WRITE : 0)
  65                       | (bio_op(bio_src) == REQ_OP_WRITE_SAME ? RQ_WSAME : 0)
  66                       | (bio_op(bio_src) == REQ_OP_WRITE_ZEROES ? RQ_UNMAP : 0)
  67                       | (bio_op(bio_src) == REQ_OP_DISCARD ? RQ_UNMAP : 0);
  68         req->device = device;
  69         req->master_bio = bio_src;
  70         req->epoch = 0;
  71
  72         drbd_clear_interval(&req->i);
  73         req->i.sector     = bio_src->bi_iter.bi_sector;
  74         req->i.size      = bio_src->bi_iter.bi_size;
  75         req->i.local = true;
  76         req->i.waiting = false;
  77
  78         INIT_LIST_HEAD(&req->tl_requests);
  79         INIT_LIST_HEAD(&req->w.list);
  80         INIT_LIST_HEAD(&req->req_pending_master_completion);
  81         INIT_LIST_HEAD(&req->req_pending_local);
  82
  83         /* one reference to be put by __drbd_make_request */
  84         atomic_set(&req->completion_ref, 1);
  85         /* one kref as long as completion_ref > 0 */
  86         kref_init(&req->kref);
  87         return req;
  88 }
  89
  90 static void drbd_remove_request_interval(struct rb_root *root,
  91                                          struct drbd_request *req)
  92 {
  93         struct drbd_device *device = req->device;
  94         struct drbd_interval *i = &req->i;
  95
  96         drbd_remove_interval(root, i);
  97
  98         /* Wake up any processes waiting for this request to complete.  */
  99         if (i->waiting)
 100                 wake_up(&device->misc_wait);
 101 }
 102
 103 void drbd_req_destroy(struct kref *kref)
 104 {
 105         struct drbd_request *req = container_of(kref, struct drbd_request, kref);
 106         struct drbd_device *device = req->device;
 107         const unsigned s = req->rq_state;
 108
 109         if ((req->master_bio && !(s & RQ_POSTPONED)) ||
 110                 atomic_read(&req->completion_ref) ||
 111                 (s & RQ_LOCAL_PENDING) ||
 112                 ((s & RQ_NET_MASK) && !(s & RQ_NET_DONE))) {
 113                 drbd_err(device, "drbd_req_destroy: Logic BUG rq_state = 0x%x, completion_ref = %d\n",
 114                                 s, atomic_read(&req->completion_ref));
 115                 return;
 116         }
 117
 118         /* If called from mod_rq_state (expected normal case) or
 119          * drbd_send_and_submit (the less likely normal path), this holds the
 120          * req_lock, and req->tl_requests will typicaly be on ->transfer_log,
 121          * though it may be still empty (never added to the transfer log).
 122          *
 123          * If called from do_retry(), we do NOT hold the req_lock, but we are
 124          * still allowed to unconditionally list_del(&req->tl_requests),
 125          * because it will be on a local on-stack list only. */
 126         list_del_init(&req->tl_requests);
 127
 128         /* finally remove the request from the conflict detection
 129          * respective block_id verification interval tree. */
 130         if (!drbd_interval_empty(&req->i)) {
 131                 struct rb_root *root;
 132
 133                 if (s & RQ_WRITE)
 134                         root = &device->write_requests;
 135                 else
 136                         root = &device->read_requests;
 137                 drbd_remove_request_interval(root, req);
 138         } else if (s & (RQ_NET_MASK & ~RQ_NET_DONE) && req->i.size != 0)
 139                 drbd_err(device, "drbd_req_destroy: Logic BUG: interval empty, but: rq_state=0x%x, sect=%llu, size=%u\n",
 140                         s, (unsigned long long)req->i.sector, req->i.size);
 141
 142         /* if it was a write, we may have to set the corresponding
 143          * bit(s) out-of-sync first. If it had a local part, we need to
 144          * release the reference to the activity log. */
 145         if (s & RQ_WRITE) {
 146                 /* Set out-of-sync unless both OK flags are set
 147                  * (local only or remote failed).
 148                  * Other places where we set out-of-sync:
 149                  * READ with local io-error */
 150
 151                 /* There is a special case:
 152                  * we may notice late that IO was suspended,
 153                  * and postpone, or schedule for retry, a write,
 154                  * before it even was submitted or sent.
 155                  * In that case we do not want to touch the bitmap at all.
 156                  */
 157                 if ((s & (RQ_POSTPONED|RQ_LOCAL_MASK|RQ_NET_MASK)) != RQ_POSTPONED) {
 158                         if (!(s & RQ_NET_OK) || !(s & RQ_LOCAL_OK))
 159                                 drbd_set_out_of_sync(device, req->i.sector, req->i.size);
 160
 161                         if ((s & RQ_NET_OK) && (s & RQ_LOCAL_OK) && (s & RQ_NET_SIS))
 162                                 drbd_set_in_sync(device, req->i.sector, req->i.size);
 163                 }
 164
 165                 /* one might be tempted to move the drbd_al_complete_io
 166                  * to the local io completion callback drbd_request_endio.
 167                  * but, if this was a mirror write, we may only
 168                  * drbd_al_complete_io after this is RQ_NET_DONE,
 169                  * otherwise the extent could be dropped from the al
 170                  * before it has actually been written on the peer.
 171                  * if we crash before our peer knows about the request,
 172                  * but after the extent has been dropped from the al,
 173                  * we would forget to resync the corresponding extent.
 174                  */
 175                 if (s & RQ_IN_ACT_LOG) {
 176                         if (get_ldev_if_state(device, D_FAILED)) {
 177                                 drbd_al_complete_io(device, &req->i);
 178                                 put_ldev(device);
 179                         } else if (__ratelimit(&drbd_ratelimit_state)) {
 180                                 drbd_warn(device, "Should have called drbd_al_complete_io(, %llu, %u), "
 181                                          "but my Disk seems to have failed :(\n",
 182                                          (unsigned long long) req->i.sector, req->i.size);
 183                         }
 184                 }
 185         }
 186
 187         mempool_free(req, drbd_request_mempool);
 188 }
 189
 190 static void wake_all_senders(struct drbd_connection *connection)
 191 {
 192         wake_up(&connection->sender_work.q_wait);
 193 }
 194
 195 /* must hold resource->req_lock */
 196 void start_new_tl_epoch(struct drbd_connection *connection)
 197 {
 198         /* no point closing an epoch, if it is empty, anyways. */
 199         if (connection->current_tle_writes == 0)
 200                 return;
 201
 202         connection->current_tle_writes = 0;
 203         atomic_inc(&connection->current_tle_nr);
 204         wake_all_senders(connection);
 205 }
 206
 207 void complete_master_bio(struct drbd_device *device,
 208                 struct bio_and_error *m)
 209 {
 210         if (unlikely(m->error))
 211                 m->bio->bi_status = errno_to_blk_status(m->error);
 212         bio_endio(m->bio);
 213         dec_ap_bio(device);
 214 }
 215
 216
 217 /* Helper for __req_mod().
 218  * Set m->bio to the master bio, if it is fit to be completed,
 219  * or leave it alone (it is initialized to NULL in __req_mod),
 220  * if it has already been completed, or cannot be completed yet.
 221  * If m->bio is set, the error status to be returned is placed in m->error.
 222  */
 223 static
 224 void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
 225 {
 226         const unsigned s = req->rq_state;
 227         struct drbd_device *device = req->device;
 228         int error, ok;
 229
 230         /* we must not complete the master bio, while it is
 231          *      still being processed by _drbd_send_zc_bio (drbd_send_dblock)
 232          *      not yet acknowledged by the peer
 233          *      not yet completed by the local io subsystem
 234          * these flags may get cleared in any order by
 235          *      the worker,
 236          *      the receiver,
 237          *      the bio_endio completion callbacks.
 238          */
 239         if ((s & RQ_LOCAL_PENDING && !(s & RQ_LOCAL_ABORTED)) ||
 240             (s & RQ_NET_QUEUED) || (s & RQ_NET_PENDING) ||
 241             (s & RQ_COMPLETION_SUSP)) {
 242                 drbd_err(device, "drbd_req_complete: Logic BUG rq_state = 0x%x\n", s);
 243                 return;
 244         }
 245
 246         if (!req->master_bio) {
 247                 drbd_err(device, "drbd_req_complete: Logic BUG, master_bio == NULL!\n");
 248                 return;
 249         }
 250
 251         /*
 252          * figure out whether to report success or failure.
 253          *
 254          * report success when at least one of the operations succeeded.
 255          * or, to put the other way,
 256          * only report failure, when both operations failed.
 257          *
 258          * what to do about the failures is handled elsewhere.
 259          * what we need to do here is just: complete the master_bio.
 260          *
 261          * local completion error, if any, has been stored as ERR_PTR
 262          * in private_bio within drbd_request_endio.
 263          */
 264         ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
 265         error = PTR_ERR(req->private_bio);
 266
 267         /* Before we can signal completion to the upper layers,
 268          * we may need to close the current transfer log epoch.
 269          * We are within the request lock, so we can simply compare
 270          * the request epoch number with the current transfer log
 271          * epoch number.  If they match, increase the current_tle_nr,
 272          * and reset the transfer log epoch write_cnt.
 273          */
 274         if (op_is_write(bio_op(req->master_bio)) &&
 275             req->epoch == atomic_read(&first_peer_device(device)->connection->current_tle_nr))
 276                 start_new_tl_epoch(first_peer_device(device)->connection);
 277
 278         /* Update disk stats */
 279         _drbd_end_io_acct(device, req);
 280
 281         /* If READ failed,
 282          * have it be pushed back to the retry work queue,
 283          * so it will re-enter __drbd_make_request(),
 284          * and be re-assigned to a suitable local or remote path,
 285          * or failed if we do not have access to good data anymore.
 286          *
 287          * Unless it was failed early by __drbd_make_request(),
 288          * because no path was available, in which case
 289          * it was not even added to the transfer_log.
 290          *
 291          * read-ahead may fail, and will not be retried.
 292          *
 293          * WRITE should have used all available paths already.
 294          */
 295         if (!ok &&
 296             bio_op(req->master_bio) == REQ_OP_READ &&
 297             !(req->master_bio->bi_opf & REQ_RAHEAD) &&
 298             !list_empty(&req->tl_requests))
 299                 req->rq_state |= RQ_POSTPONED;
 300
 301         if (!(req->rq_state & RQ_POSTPONED)) {
 302                 m->error = ok ? 0 : (error ?: -EIO);
 303                 m->bio = req->master_bio;
 304                 req->master_bio = NULL;
 305                 /* We leave it in the tree, to be able to verify later
 306                  * write-acks in protocol != C during resync.
 307                  * But we mark it as "complete", so it won't be counted as
 308                  * conflict in a multi-primary setup. */
 309                 req->i.completed = true;
 310         }
 311
 312         if (req->i.waiting)
 313                 wake_up(&device->misc_wait);
 314
 315         /* Either we are about to complete to upper layers,
 316          * or we will restart this request.
 317          * In either case, the request object will be destroyed soon,
 318          * so better remove it from all lists. */
 319         list_del_init(&req->req_pending_master_completion);
 320 }
 321
 322 /* still holds resource->req_lock */
 323 static void drbd_req_put_completion_ref(struct drbd_request *req, struct bio_and_error *m, int put)
 324 {
 325         struct drbd_device *device = req->device;
 326         D_ASSERT(device, m || (req->rq_state & RQ_POSTPONED));
 327
 328         if (!put)
 329                 return;
 330
 331         if (!atomic_sub_and_test(put, &req->completion_ref))
 332                 return;
 333
 334         drbd_req_complete(req, m);
 335
 336         /* local completion may still come in later,
 337          * we need to keep the req object around. */
 338         if (req->rq_state & RQ_LOCAL_ABORTED)
 339                 return;
 340
 341         if (req->rq_state & RQ_POSTPONED) {
 342                 /* don't destroy the req object just yet,
 343                  * but queue it for retry */
 344                 drbd_restart_request(req);
 345                 return;
 346         }
 347
 348         kref_put(&req->kref, drbd_req_destroy);
 349 }
 350
 351 static void set_if_null_req_next(struct drbd_peer_device *peer_device, struct drbd_request *req)
 352 {
 353         struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
 354         if (!connection)
 355                 return;
 356         if (connection->req_next == NULL)
 357                 connection->req_next = req;
 358 }
 359
 360 static void advance_conn_req_next(struct drbd_peer_device *peer_device, struct drbd_request *req)
 361 {
 362         struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
 363         if (!connection)
 364                 return;
 365         if (connection->req_next != req)
 366                 return;
 367         list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) {
 368                 const unsigned s = req->rq_state;
 369                 if (s & RQ_NET_QUEUED)
 370                         break;
 371         }
 372         if (&req->tl_requests == &connection->transfer_log)
 373                 req = NULL;
 374         connection->req_next = req;
 375 }
 376
 377 static void set_if_null_req_ack_pending(struct drbd_peer_device *peer_device, struct drbd_request *req)
 378 {
 379         struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
 380         if (!connection)
 381                 return;
 382         if (connection->req_ack_pending == NULL)
 383                 connection->req_ack_pending = req;
 384 }
 385
 386 static void advance_conn_req_ack_pending(struct drbd_peer_device *peer_device, struct drbd_request *req)
 387 {
 388         struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
 389         if (!connection)
 390                 return;
 391         if (connection->req_ack_pending != req)
 392                 return;
 393         list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) {
 394                 const unsigned s = req->rq_state;
 395                 if ((s & RQ_NET_SENT) && (s & RQ_NET_PENDING))
 396                         break;
 397         }
 398         if (&req->tl_requests == &connection->transfer_log)
 399                 req = NULL;
 400         connection->req_ack_pending = req;
 401 }
 402
 403 static void set_if_null_req_not_net_done(struct drbd_peer_device *peer_device, struct drbd_request *req)
 404 {
 405         struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
 406         if (!connection)
 407                 return;
 408         if (connection->req_not_net_done == NULL)
 409                 connection->req_not_net_done = req;
 410 }
 411
 412 static void advance_conn_req_not_net_done(struct drbd_peer_device *peer_device, struct drbd_request *req)
 413 {
 414         struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
 415         if (!connection)
 416                 return;
 417         if (connection->req_not_net_done != req)
 418                 return;
 419         list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) {
 420                 const unsigned s = req->rq_state;
 421                 if ((s & RQ_NET_SENT) && !(s & RQ_NET_DONE))
 422                         break;
 423         }
 424         if (&req->tl_requests == &connection->transfer_log)
 425                 req = NULL;
 426         connection->req_not_net_done = req;
 427 }
 428
 429 /* I'd like this to be the only place that manipulates
 430  * req->completion_ref and req->kref. */
 431 static void mod_rq_state(struct drbd_request *req, struct bio_and_error *m,
 432                 int clear, int set)
 433 {
 434         struct drbd_device *device = req->device;
 435         struct drbd_peer_device *peer_device = first_peer_device(device);
 436         unsigned s = req->rq_state;
 437         int c_put = 0;
 438
 439         if (drbd_suspended(device) && !((s | clear) & RQ_COMPLETION_SUSP))
 440                 set |= RQ_COMPLETION_SUSP;
 441
 442         /* apply */
 443
 444         req->rq_state &= ~clear;
 445         req->rq_state |= set;
 446
 447         /* no change? */
 448         if (req->rq_state == s)
 449                 return;
 450
 451         /* intent: get references */
 452
 453         kref_get(&req->kref);
 454
 455         if (!(s & RQ_LOCAL_PENDING) && (set & RQ_LOCAL_PENDING))
 456                 atomic_inc(&req->completion_ref);
 457
 458         if (!(s & RQ_NET_PENDING) && (set & RQ_NET_PENDING)) {
 459                 inc_ap_pending(device);
 460                 atomic_inc(&req->completion_ref);
 461         }
 462
 463         if (!(s & RQ_NET_QUEUED) && (set & RQ_NET_QUEUED)) {
 464                 atomic_inc(&req->completion_ref);
 465                 set_if_null_req_next(peer_device, req);
 466         }
 467
 468         if (!(s & RQ_EXP_BARR_ACK) && (set & RQ_EXP_BARR_ACK))
 469                 kref_get(&req->kref); /* wait for the DONE */
 470
 471         if (!(s & RQ_NET_SENT) && (set & RQ_NET_SENT)) {
 472                 /* potentially already completed in the ack_receiver thread */
 473                 if (!(s & RQ_NET_DONE)) {
 474                         atomic_add(req->i.size >> 9, &device->ap_in_flight);
 475                         set_if_null_req_not_net_done(peer_device, req);
 476                 }
 477                 if (req->rq_state & RQ_NET_PENDING)
 478                         set_if_null_req_ack_pending(peer_device, req);
 479         }
 480
 481         if (!(s & RQ_COMPLETION_SUSP) && (set & RQ_COMPLETION_SUSP))
 482                 atomic_inc(&req->completion_ref);
 483
 484         /* progress: put references */
 485
 486         if ((s & RQ_COMPLETION_SUSP) && (clear & RQ_COMPLETION_SUSP))
 487                 ++c_put;
 488
 489         if (!(s & RQ_LOCAL_ABORTED) && (set & RQ_LOCAL_ABORTED)) {
 490                 D_ASSERT(device, req->rq_state & RQ_LOCAL_PENDING);
 491                 ++c_put;
 492         }
 493
 494         if ((s & RQ_LOCAL_PENDING) && (clear & RQ_LOCAL_PENDING)) {
 495                 if (req->rq_state & RQ_LOCAL_ABORTED)
 496                         kref_put(&req->kref, drbd_req_destroy);
 497                 else
 498                         ++c_put;
 499                 list_del_init(&req->req_pending_local);
 500         }
 501
 502         if ((s & RQ_NET_PENDING) && (clear & RQ_NET_PENDING)) {
 503                 dec_ap_pending(device);
 504                 ++c_put;
 505                 req->acked_jif = jiffies;
 506                 advance_conn_req_ack_pending(peer_device, req);
 507         }
 508
 509         if ((s & RQ_NET_QUEUED) && (clear & RQ_NET_QUEUED)) {
 510                 ++c_put;
 511                 advance_conn_req_next(peer_device, req);
 512         }
 513
 514         if (!(s & RQ_NET_DONE) && (set & RQ_NET_DONE)) {
 515                 if (s & RQ_NET_SENT)
 516                         atomic_sub(req->i.size >> 9, &device->ap_in_flight);
 517                 if (s & RQ_EXP_BARR_ACK)
 518                         kref_put(&req->kref, drbd_req_destroy);
 519                 req->net_done_jif = jiffies;
 520
 521                 /* in ahead/behind mode, or just in case,
 522                  * before we finally destroy this request,
 523                  * the caching pointers must not reference it anymore */
 524                 advance_conn_req_next(peer_device, req);
 525                 advance_conn_req_ack_pending(peer_device, req);
 526                 advance_conn_req_not_net_done(peer_device, req);
 527         }
 528
 529         /* potentially complete and destroy */
 530
 531         /* If we made progress, retry conflicting peer requests, if any. */
 532         if (req->i.waiting)
 533                 wake_up(&device->misc_wait);
 534
 535         drbd_req_put_completion_ref(req, m, c_put);
 536         kref_put(&req->kref, drbd_req_destroy);
 537 }
 538
 539 static void drbd_report_io_error(struct drbd_device *device, struct drbd_request *req)
 540 {
 541         char b[BDEVNAME_SIZE];
 542
 543         if (!__ratelimit(&drbd_ratelimit_state))
 544                 return;
 545
 546         drbd_warn(device, "local %s IO error sector %llu+%u on %s\n",
 547                         (req->rq_state & RQ_WRITE) ? "WRITE" : "READ",
 548                         (unsigned long long)req->i.sector,
 549                         req->i.size >> 9,
 550                         bdevname(device->ldev->backing_bdev, b));
 551 }
 552
 553 /* Helper for HANDED_OVER_TO_NETWORK.
 554  * Is this a protocol A write (neither WRITE_ACK nor RECEIVE_ACK expected)?
 555  * Is it also still "PENDING"?
 556  * --> If so, clear PENDING and set NET_OK below.
 557  * If it is a protocol A write, but not RQ_PENDING anymore, neg-ack was faster
 558  * (and we must not set RQ_NET_OK) */
 559 static inline bool is_pending_write_protocol_A(struct drbd_request *req)
 560 {
 561         return (req->rq_state &
 562                    (RQ_WRITE|RQ_NET_PENDING|RQ_EXP_WRITE_ACK|RQ_EXP_RECEIVE_ACK))
 563                 == (RQ_WRITE|RQ_NET_PENDING);
 564 }
 565
 566 /* obviously this could be coded as many single functions
 567  * instead of one huge switch,
 568  * or by putting the code directly in the respective locations
 569  * (as it has been before).
 570  *
 571  * but having it this way
 572  *  enforces that it is all in this one place, where it is easier to audit,
 573  *  it makes it obvious that whatever "event" "happens" to a request should
 574  *  happen "atomically" within the req_lock,
 575  *  and it enforces that we have to think in a very structured manner
 576  *  about the "events" that may happen to a request during its life time ...
 577  */
 578 int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 579                 struct bio_and_error *m)
 580 {
 581         struct drbd_device *const device = req->device;
 582         struct drbd_peer_device *const peer_device = first_peer_device(device);
 583         struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
 584         struct net_conf *nc;
 585         int p, rv = 0;
 586
 587         if (m)
 588                 m->bio = NULL;
 589
 590         switch (what) {
 591         default:
 592                 drbd_err(device, "LOGIC BUG in %s:%u\n", __FILE__ , __LINE__);
 593                 break;
 594
 595         /* does not happen...
 596          * initialization done in drbd_req_new
 597         case CREATED:
 598                 break;
 599                 */
 600
 601         case TO_BE_SENT: /* via network */
 602                 /* reached via __drbd_make_request
 603                  * and from w_read_retry_remote */
 604                 D_ASSERT(device, !(req->rq_state & RQ_NET_MASK));
 605                 rcu_read_lock();
 606                 nc = rcu_dereference(connection->net_conf);
 607                 p = nc->wire_protocol;
 608                 rcu_read_unlock();
 609                 req->rq_state |=
 610                         p == DRBD_PROT_C ? RQ_EXP_WRITE_ACK :
 611                         p == DRBD_PROT_B ? RQ_EXP_RECEIVE_ACK : 0;
 612                 mod_rq_state(req, m, 0, RQ_NET_PENDING);
 613                 break;
 614
 615         case TO_BE_SUBMITTED: /* locally */
 616                 /* reached via __drbd_make_request */
 617                 D_ASSERT(device, !(req->rq_state & RQ_LOCAL_MASK));
 618                 mod_rq_state(req, m, 0, RQ_LOCAL_PENDING);
 619                 break;
 620
 621         case COMPLETED_OK:
 622                 if (req->rq_state & RQ_WRITE)
 623                         device->writ_cnt += req->i.size >> 9;
 624                 else
 625                         device->read_cnt += req->i.size >> 9;
 626
 627                 mod_rq_state(req, m, RQ_LOCAL_PENDING,
 628                                 RQ_LOCAL_COMPLETED|RQ_LOCAL_OK);
 629                 break;
 630
 631         case ABORT_DISK_IO:
 632                 mod_rq_state(req, m, 0, RQ_LOCAL_ABORTED);
 633                 break;
 634
 635         case WRITE_COMPLETED_WITH_ERROR:
 636                 drbd_report_io_error(device, req);
 637                 __drbd_chk_io_error(device, DRBD_WRITE_ERROR);
 638                 mod_rq_state(req, m, RQ_LOCAL_PENDING, RQ_LOCAL_COMPLETED);
 639                 break;
 640
 641         case READ_COMPLETED_WITH_ERROR:
 642                 drbd_set_out_of_sync(device, req->i.sector, req->i.size);
 643                 drbd_report_io_error(device, req);
 644                 __drbd_chk_io_error(device, DRBD_READ_ERROR);
 645                 /* fall through. */
 646         case READ_AHEAD_COMPLETED_WITH_ERROR:
 647                 /* it is legal to fail read-ahead, no __drbd_chk_io_error in that case. */
 648                 mod_rq_state(req, m, RQ_LOCAL_PENDING, RQ_LOCAL_COMPLETED);
 649                 break;
 650
 651         case DISCARD_COMPLETED_NOTSUPP:
 652         case DISCARD_COMPLETED_WITH_ERROR:
 653                 /* I'd rather not detach from local disk just because it
 654                  * failed a REQ_DISCARD. */
 655                 mod_rq_state(req, m, RQ_LOCAL_PENDING, RQ_LOCAL_COMPLETED);
 656                 break;
 657
 658         case QUEUE_FOR_NET_READ:
 659                 /* READ, and
 660                  * no local disk,
 661                  * or target area marked as invalid,
 662                  * or just got an io-error. */
 663                 /* from __drbd_make_request
 664                  * or from bio_endio during read io-error recovery */
 665
 666                 /* So we can verify the handle in the answer packet.
 667                  * Corresponding drbd_remove_request_interval is in
 668                  * drbd_req_complete() */
 669                 D_ASSERT(device, drbd_interval_empty(&req->i));
 670                 drbd_insert_interval(&device->read_requests, &req->i);
 671
 672                 set_bit(UNPLUG_REMOTE, &device->flags);
 673
 674                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 675                 D_ASSERT(device, (req->rq_state & RQ_LOCAL_MASK) == 0);
 676                 mod_rq_state(req, m, 0, RQ_NET_QUEUED);
 677                 req->w.cb = w_send_read_req;
 678                 drbd_queue_work(&connection->sender_work,
 679                                 &req->w);
 680                 break;
 681
 682         case QUEUE_FOR_NET_WRITE:
 683                 /* assert something? */
 684                 /* from __drbd_make_request only */
 685
 686                 /* Corresponding drbd_remove_request_interval is in
 687                  * drbd_req_complete() */
 688                 D_ASSERT(device, drbd_interval_empty(&req->i));
 689                 drbd_insert_interval(&device->write_requests, &req->i);
 690
 691                 /* NOTE
 692                  * In case the req ended up on the transfer log before being
 693                  * queued on the worker, it could lead to this request being
 694                  * missed during cleanup after connection loss.
 695                  * So we have to do both operations here,
 696                  * within the same lock that protects the transfer log.
 697                  *
 698                  * _req_add_to_epoch(req); this has to be after the
 699                  * _maybe_start_new_epoch(req); which happened in
 700                  * __drbd_make_request, because we now may set the bit
 701                  * again ourselves to close the current epoch.
 702                  *
 703                  * Add req to the (now) current epoch (barrier). */
 704
 705                 /* otherwise we may lose an unplug, which may cause some remote
 706                  * io-scheduler timeout to expire, increasing maximum latency,
 707                  * hurting performance. */
 708                 set_bit(UNPLUG_REMOTE, &device->flags);
 709
 710                 /* queue work item to send data */
 711                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 712                 mod_rq_state(req, m, 0, RQ_NET_QUEUED|RQ_EXP_BARR_ACK);
 713                 req->w.cb =  w_send_dblock;
 714                 drbd_queue_work(&connection->sender_work,
 715                                 &req->w);
 716
 717                 /* close the epoch, in case it outgrew the limit */
 718                 rcu_read_lock();
 719                 nc = rcu_dereference(connection->net_conf);
 720                 p = nc->max_epoch_size;
 721                 rcu_read_unlock();
 722                 if (connection->current_tle_writes >= p)
 723                         start_new_tl_epoch(connection);
 724
 725                 break;
 726
 727         case QUEUE_FOR_SEND_OOS:
 728                 mod_rq_state(req, m, 0, RQ_NET_QUEUED);
 729                 req->w.cb =  w_send_out_of_sync;
 730                 drbd_queue_work(&connection->sender_work,
 731                                 &req->w);
 732                 break;
 733
 734         case READ_RETRY_REMOTE_CANCELED:
 735         case SEND_CANCELED:
 736         case SEND_FAILED:
 737                 /* real cleanup will be done from tl_clear.  just update flags
 738                  * so it is no longer marked as on the worker queue */
 739                 mod_rq_state(req, m, RQ_NET_QUEUED, 0);
 740                 break;
 741
 742         case HANDED_OVER_TO_NETWORK:
 743                 /* assert something? */
 744                 if (is_pending_write_protocol_A(req))
 745                         /* this is what is dangerous about protocol A:
 746                          * pretend it was successfully written on the peer. */
 747                         mod_rq_state(req, m, RQ_NET_QUEUED|RQ_NET_PENDING,
 748                                                 RQ_NET_SENT|RQ_NET_OK);
 749                 else
 750                         mod_rq_state(req, m, RQ_NET_QUEUED, RQ_NET_SENT);
 751                 /* It is still not yet RQ_NET_DONE until the
 752                  * corresponding epoch barrier got acked as well,
 753                  * so we know what to dirty on connection loss. */
 754                 break;
 755
 756         case OOS_HANDED_TO_NETWORK:
 757                 /* Was not set PENDING, no longer QUEUED, so is now DONE
 758                  * as far as this connection is concerned. */
 759                 mod_rq_state(req, m, RQ_NET_QUEUED, RQ_NET_DONE);
 760                 break;
 761
 762         case CONNECTION_LOST_WHILE_PENDING:
 763                 /* transfer log cleanup after connection loss */
 764                 mod_rq_state(req, m,
 765                                 RQ_NET_OK|RQ_NET_PENDING|RQ_COMPLETION_SUSP,
 766                                 RQ_NET_DONE);
 767                 break;
 768
 769         case CONFLICT_RESOLVED:
 770                 /* for superseded conflicting writes of multiple primaries,
 771                  * there is no need to keep anything in the tl, potential
 772                  * node crashes are covered by the activity log.
 773                  *
 774                  * If this request had been marked as RQ_POSTPONED before,
 775                  * it will actually not be completed, but "restarted",
 776                  * resubmitted from the retry worker context. */
 777                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 778                 D_ASSERT(device, req->rq_state & RQ_EXP_WRITE_ACK);
 779                 mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_DONE|RQ_NET_OK);
 780                 break;
 781
 782         case WRITE_ACKED_BY_PEER_AND_SIS:
 783                 req->rq_state |= RQ_NET_SIS;
 784         case WRITE_ACKED_BY_PEER:
 785                 /* Normal operation protocol C: successfully written on peer.
 786                  * During resync, even in protocol != C,
 787                  * we requested an explicit write ack anyways.
 788                  * Which means we cannot even assert anything here.
 789                  * Nothing more to do here.
 790                  * We want to keep the tl in place for all protocols, to cater
 791                  * for volatile write-back caches on lower level devices. */
 792                 goto ack_common;
 793         case RECV_ACKED_BY_PEER:
 794                 D_ASSERT(device, req->rq_state & RQ_EXP_RECEIVE_ACK);
 795                 /* protocol B; pretends to be successfully written on peer.
 796                  * see also notes above in HANDED_OVER_TO_NETWORK about
 797                  * protocol != C */
 798         ack_common:
 799                 mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK);
 800                 break;
 801
 802         case POSTPONE_WRITE:
 803                 D_ASSERT(device, req->rq_state & RQ_EXP_WRITE_ACK);
 804                 /* If this node has already detected the write conflict, the
 805                  * worker will be waiting on misc_wait.  Wake it up once this
 806                  * request has completed locally.
 807                  */
 808                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 809                 req->rq_state |= RQ_POSTPONED;
 810                 if (req->i.waiting)
 811                         wake_up(&device->misc_wait);
 812                 /* Do not clear RQ_NET_PENDING. This request will make further
 813                  * progress via restart_conflicting_writes() or
 814                  * fail_postponed_requests(). Hopefully. */
 815                 break;
 816
 817         case NEG_ACKED:
 818                 mod_rq_state(req, m, RQ_NET_OK|RQ_NET_PENDING, 0);
 819                 break;
 820
 821         case FAIL_FROZEN_DISK_IO:
 822                 if (!(req->rq_state & RQ_LOCAL_COMPLETED))
 823                         break;
 824                 mod_rq_state(req, m, RQ_COMPLETION_SUSP, 0);
 825                 break;
 826
 827         case RESTART_FROZEN_DISK_IO:
 828                 if (!(req->rq_state & RQ_LOCAL_COMPLETED))
 829                         break;
 830
 831                 mod_rq_state(req, m,
 832                                 RQ_COMPLETION_SUSP|RQ_LOCAL_COMPLETED,
 833                                 RQ_LOCAL_PENDING);
 834
 835                 rv = MR_READ;
 836                 if (bio_data_dir(req->master_bio) == WRITE)
 837                         rv = MR_WRITE;
 838
 839                 get_ldev(device); /* always succeeds in this call path */
 840                 req->w.cb = w_restart_disk_io;
 841                 drbd_queue_work(&connection->sender_work,
 842                                 &req->w);
 843                 break;
 844
 845         case RESEND:
 846                 /* Simply complete (local only) READs. */
 847                 if (!(req->rq_state & RQ_WRITE) && !req->w.cb) {
 848                         mod_rq_state(req, m, RQ_COMPLETION_SUSP, 0);
 849                         break;
 850                 }
 851
 852                 /* If RQ_NET_OK is already set, we got a P_WRITE_ACK or P_RECV_ACK
 853                    before the connection loss (B&C only); only P_BARRIER_ACK
 854                    (or the local completion?) was missing when we suspended.
 855                    Throwing them out of the TL here by pretending we got a BARRIER_ACK.
 856                    During connection handshake, we ensure that the peer was not rebooted. */
 857                 if (!(req->rq_state & RQ_NET_OK)) {
 858                         /* FIXME could this possibly be a req->dw.cb == w_send_out_of_sync?
 859                          * in that case we must not set RQ_NET_PENDING. */
 860
 861                         mod_rq_state(req, m, RQ_COMPLETION_SUSP, RQ_NET_QUEUED|RQ_NET_PENDING);
 862                         if (req->w.cb) {
 863                                 /* w.cb expected to be w_send_dblock, or w_send_read_req */
 864                                 drbd_queue_work(&connection->sender_work,
 865                                                 &req->w);
 866                                 rv = req->rq_state & RQ_WRITE ? MR_WRITE : MR_READ;
 867                         } /* else: FIXME can this happen? */
 868                         break;
 869                 }
 870                 /* else, fall through to BARRIER_ACKED */
 871
 872         case BARRIER_ACKED:
 873                 /* barrier ack for READ requests does not make sense */
 874                 if (!(req->rq_state & RQ_WRITE))
 875                         break;
 876
 877                 if (req->rq_state & RQ_NET_PENDING) {
 878                         /* barrier came in before all requests were acked.
 879                          * this is bad, because if the connection is lost now,
 880                          * we won't be able to clean them up... */
 881                         drbd_err(device, "FIXME (BARRIER_ACKED but pending)\n");
 882                 }
 883                 /* Allowed to complete requests, even while suspended.
 884                  * As this is called for all requests within a matching epoch,
 885                  * we need to filter, and only set RQ_NET_DONE for those that
 886                  * have actually been on the wire. */
 887                 mod_rq_state(req, m, RQ_COMPLETION_SUSP,
 888                                 (req->rq_state & RQ_NET_MASK) ? RQ_NET_DONE : 0);
 889                 break;
 890
 891         case DATA_RECEIVED:
 892                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 893                 mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK|RQ_NET_DONE);
 894                 break;
 895
 896         case QUEUE_AS_DRBD_BARRIER:
 897                 start_new_tl_epoch(connection);
 898                 mod_rq_state(req, m, 0, RQ_NET_OK|RQ_NET_DONE);
 899                 break;
 900         };
 901
 902         return rv;
 903 }
 904
 905 /* we may do a local read if:
 906  * - we are consistent (of course),
 907  * - or we are generally inconsistent,
 908  *   BUT we are still/already IN SYNC for this area.
 909  *   since size may be bigger than BM_BLOCK_SIZE,
 910  *   we may need to check several bits.
 911  */
 912 static bool drbd_may_do_local_read(struct drbd_device *device, sector_t sector, int size)
 913 {
 914         unsigned long sbnr, ebnr;
 915         sector_t esector, nr_sectors;
 916
 917         if (device->state.disk == D_UP_TO_DATE)
 918                 return true;
 919         if (device->state.disk != D_INCONSISTENT)
 920                 return false;
 921         esector = sector + (size >> 9) - 1;
 922         nr_sectors = drbd_get_capacity(device->this_bdev);
 923         D_ASSERT(device, sector  < nr_sectors);
 924         D_ASSERT(device, esector < nr_sectors);
 925
 926         sbnr = BM_SECT_TO_BIT(sector);
 927         ebnr = BM_SECT_TO_BIT(esector);
 928
 929         return drbd_bm_count_bits(device, sbnr, ebnr) == 0;
 930 }
 931
 932 static bool remote_due_to_read_balancing(struct drbd_device *device, sector_t sector,
 933                 enum drbd_read_balancing rbm)
 934 {
 935         struct backing_dev_info *bdi;
 936         int stripe_shift;
 937
 938         switch (rbm) {
 939         case RB_CONGESTED_REMOTE:
 940                 bdi = device->ldev->backing_bdev->bd_disk->queue->backing_dev_info;
 941                 return bdi_read_congested(bdi);
 942         case RB_LEAST_PENDING:
 943                 return atomic_read(&device->local_cnt) >
 944                         atomic_read(&device->ap_pending_cnt) + atomic_read(&device->rs_pending_cnt);
 945         case RB_32K_STRIPING:  /* stripe_shift = 15 */
 946         case RB_64K_STRIPING:
 947         case RB_128K_STRIPING:
 948         case RB_256K_STRIPING:
 949         case RB_512K_STRIPING:
 950         case RB_1M_STRIPING:   /* stripe_shift = 20 */
 951                 stripe_shift = (rbm - RB_32K_STRIPING + 15);
 952                 return (sector >> (stripe_shift - 9)) & 1;
 953         case RB_ROUND_ROBIN:
 954                 return test_and_change_bit(READ_BALANCE_RR, &device->flags);
 955         case RB_PREFER_REMOTE:
 956                 return true;
 957         case RB_PREFER_LOCAL:
 958         default:
 959                 return false;
 960         }
 961 }
 962
 963 /*
 964  * complete_conflicting_writes  -  wait for any conflicting write requests
 965  *
 966  * The write_requests tree contains all active write requests which we
 967  * currently know about.  Wait for any requests to complete which conflict with
 968  * the new one.
 969  *
 970  * Only way out: remove the conflicting intervals from the tree.
 971  */
 972 static void complete_conflicting_writes(struct drbd_request *req)
 973 {
 974         DEFINE_WAIT(wait);
 975         struct drbd_device *device = req->device;
 976         struct drbd_interval *i;
 977         sector_t sector = req->i.sector;
 978         int size = req->i.size;
 979
 980         for (;;) {
 981                 drbd_for_each_overlap(i, &device->write_requests, sector, size) {
 982                         /* Ignore, if already completed to upper layers. */
 983                         if (i->completed)
 984                                 continue;
 985                         /* Handle the first found overlap.  After the schedule
 986                          * we have to restart the tree walk. */
 987                         break;
 988                 }
 989                 if (!i) /* if any */
 990                         break;
 991
 992                 /* Indicate to wake up device->misc_wait on progress.  */
 993                 prepare_to_wait(&device->misc_wait, &wait, TASK_UNINTERRUPTIBLE);
 994                 i->waiting = true;
 995                 spin_unlock_irq(&device->resource->req_lock);
 996                 schedule();
 997                 spin_lock_irq(&device->resource->req_lock);
 998         }
 999         finish_wait(&device->misc_wait, &wait);
1000 }
1001
1002 /* called within req_lock */
1003 static void maybe_pull_ahead(struct drbd_device *device)
1004 {
1005         struct drbd_connection *connection = first_peer_device(device)->connection;
1006         struct net_conf *nc;
1007         bool congested = false;
1008         enum drbd_on_congestion on_congestion;
1009
1010         rcu_read_lock();
1011         nc = rcu_dereference(connection->net_conf);
1012         on_congestion = nc ? nc->on_congestion : OC_BLOCK;
1013         rcu_read_unlock();
1014         if (on_congestion == OC_BLOCK ||
1015             connection->agreed_pro_version < 96)
1016                 return;
1017
1018         if (on_congestion == OC_PULL_AHEAD && device->state.conn == C_AHEAD)
1019                 return; /* nothing to do ... */
1020
1021         /* If I don't even have good local storage, we can not reasonably try
1022          * to pull ahead of the peer. We also need the local reference to make
1023          * sure device->act_log is there.
1024          */
1025         if (!get_ldev_if_state(device, D_UP_TO_DATE))
1026                 return;
1027
1028         if (nc->cong_fill &&
1029             atomic_read(&device->ap_in_flight) >= nc->cong_fill) {
1030                 drbd_info(device, "Congestion-fill threshold reached\n");
1031                 congested = true;
1032         }
1033
1034         if (device->act_log->used >= nc->cong_extents) {
1035                 drbd_info(device, "Congestion-extents threshold reached\n");
1036                 congested = true;
1037         }
1038
1039         if (congested) {
1040                 /* start a new epoch for non-mirrored writes */
1041                 start_new_tl_epoch(first_peer_device(device)->connection);
1042
1043                 if (on_congestion == OC_PULL_AHEAD)
1044                         _drbd_set_state(_NS(device, conn, C_AHEAD), 0, NULL);
1045                 else  /*nc->on_congestion == OC_DISCONNECT */
1046                         _drbd_set_state(_NS(device, conn, C_DISCONNECTING), 0, NULL);
1047         }
1048         put_ldev(device);
1049 }
1050
1051 /* If this returns false, and req->private_bio is still set,
1052  * this should be submitted locally.
1053  *
1054  * If it returns false, but req->private_bio is not set,
1055  * we do not have access to good data :(
1056  *
1057  * Otherwise, this destroys req->private_bio, if any,
1058  * and returns true.
1059  */
1060 static bool do_remote_read(struct drbd_request *req)
1061 {
1062         struct drbd_device *device = req->device;
1063         enum drbd_read_balancing rbm;
1064
1065         if (req->private_bio) {
1066                 if (!drbd_may_do_local_read(device,
1067                                         req->i.sector, req->i.size)) {
1068                         bio_put(req->private_bio);
1069                         req->private_bio = NULL;
1070                         put_ldev(device);
1071                 }
1072         }
1073
1074         if (device->state.pdsk != D_UP_TO_DATE)
1075                 return false;
1076
1077         if (req->private_bio == NULL)
1078                 return true;
1079
1080         /* TODO: improve read balancing decisions, take into account drbd
1081          * protocol, pending requests etc. */
1082
1083         rcu_read_lock();
1084         rbm = rcu_dereference(device->ldev->disk_conf)->read_balancing;
1085         rcu_read_unlock();
1086
1087         if (rbm == RB_PREFER_LOCAL && req->private_bio)
1088                 return false; /* submit locally */
1089
1090         if (remote_due_to_read_balancing(device, req->i.sector, rbm)) {
1091                 if (req->private_bio) {
1092                         bio_put(req->private_bio);
1093                         req->private_bio = NULL;
1094                         put_ldev(device);
1095                 }
1096                 return true;
1097         }
1098
1099         return false;
1100 }
1101
1102 bool drbd_should_do_remote(union drbd_dev_state s)
1103 {
1104         return s.pdsk == D_UP_TO_DATE ||
1105                 (s.pdsk >= D_INCONSISTENT &&
1106                  s.conn >= C_WF_BITMAP_T &&
1107                  s.conn < C_AHEAD);
1108         /* Before proto 96 that was >= CONNECTED instead of >= C_WF_BITMAP_T.
1109            That is equivalent since before 96 IO was frozen in the C_WF_BITMAP*
1110            states. */
1111 }
1112
1113 static bool drbd_should_send_out_of_sync(union drbd_dev_state s)
1114 {
1115         return s.conn == C_AHEAD || s.conn == C_WF_BITMAP_S;
1116         /* pdsk = D_INCONSISTENT as a consequence. Protocol 96 check not necessary
1117            since we enter state C_AHEAD only if proto >= 96 */
1118 }
1119
1120 /* returns number of connections (== 1, for drbd 8.4)
1121  * expected to actually write this data,
1122  * which does NOT include those that we are L_AHEAD for. */
1123 static int drbd_process_write_request(struct drbd_request *req)
1124 {
1125         struct drbd_device *device = req->device;
1126         int remote, send_oos;
1127
1128         remote = drbd_should_do_remote(device->state);
1129         send_oos = drbd_should_send_out_of_sync(device->state);
1130
1131         /* Need to replicate writes.  Unless it is an empty flush,
1132          * which is better mapped to a DRBD P_BARRIER packet,
1133          * also for drbd wire protocol compatibility reasons.
1134          * If this was a flush, just start a new epoch.
1135          * Unless the current epoch was empty anyways, or we are not currently
1136          * replicating, in which case there is no point. */
1137         if (unlikely(req->i.size == 0)) {
1138                 /* The only size==0 bios we expect are empty flushes. */
1139                 D_ASSERT(device, req->master_bio->bi_opf & REQ_PREFLUSH);
1140                 if (remote)
1141                         _req_mod(req, QUEUE_AS_DRBD_BARRIER);
1142                 return remote;
1143         }
1144
1145         if (!remote && !send_oos)
1146                 return 0;
1147
1148         D_ASSERT(device, !(remote && send_oos));
1149
1150         if (remote) {
1151                 _req_mod(req, TO_BE_SENT);
1152                 _req_mod(req, QUEUE_FOR_NET_WRITE);
1153         } else if (drbd_set_out_of_sync(device, req->i.sector, req->i.size))
1154                 _req_mod(req, QUEUE_FOR_SEND_OOS);
1155
1156         return remote;
1157 }
1158
1159 static void drbd_process_discard_req(struct drbd_request *req)
1160 {
1161         struct block_device *bdev = req->device->ldev->backing_bdev;
1162
1163         if (blkdev_issue_zeroout(bdev, req->i.sector, req->i.size >> 9,
1164                         GFP_NOIO, 0))
1165                 req->private_bio->bi_status = BLK_STS_IOERR;
1166         bio_endio(req->private_bio);
1167 }
1168
1169 static void
1170 drbd_submit_req_private_bio(struct drbd_request *req)
1171 {
1172         struct drbd_device *device = req->device;
1173         struct bio *bio = req->private_bio;
1174         unsigned int type;
1175
1176         if (bio_op(bio) != REQ_OP_READ)
1177                 type = DRBD_FAULT_DT_WR;
1178         else if (bio->bi_opf & REQ_RAHEAD)
1179                 type = DRBD_FAULT_DT_RA;
1180         else
1181                 type = DRBD_FAULT_DT_RD;
1182
1183         bio_set_dev(bio, device->ldev->backing_bdev);
1184
1185         /* State may have changed since we grabbed our reference on the
1186          * ->ldev member. Double check, and short-circuit to endio.
1187          * In case the last activity log transaction failed to get on
1188          * stable storage, and this is a WRITE, we may not even submit
1189          * this bio. */
1190         if (get_ldev(device)) {
1191                 if (drbd_insert_fault(device, type))
1192                         bio_io_error(bio);
1193                 else if (bio_op(bio) == REQ_OP_WRITE_ZEROES ||
1194                          bio_op(bio) == REQ_OP_DISCARD)
1195                         drbd_process_discard_req(req);
1196                 else
1197                         generic_make_request(bio);
1198                 put_ldev(device);
1199         } else
1200                 bio_io_error(bio);
1201 }
1202
1203 static void drbd_queue_write(struct drbd_device *device, struct drbd_request *req)
1204 {
1205         spin_lock_irq(&device->resource->req_lock);
1206         list_add_tail(&req->tl_requests, &device->submit.writes);
1207         list_add_tail(&req->req_pending_master_completion,
1208                         &device->pending_master_completion[1 /* WRITE */]);
1209         spin_unlock_irq(&device->resource->req_lock);
1210         queue_work(device->submit.wq, &device->submit.worker);
1211         /* do_submit() may sleep internally on al_wait, too */
1212         wake_up(&device->al_wait);
1213 }
1214
1215 /* returns the new drbd_request pointer, if the caller is expected to
1216  * drbd_send_and_submit() it (to save latency), or NULL if we queued the
1217  * request on the submitter thread.
1218  * Returns ERR_PTR(-ENOMEM) if we cannot allocate a drbd_request.
1219  */
1220 static struct drbd_request *
1221 drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long start_jif)
1222 {
1223         const int rw = bio_data_dir(bio);
1224         struct drbd_request *req;
1225
1226         /* allocate outside of all locks; */
1227         req = drbd_req_new(device, bio);
1228         if (!req) {
1229                 dec_ap_bio(device);
1230                 /* only pass the error to the upper layers.
1231                  * if user cannot handle io errors, that's not our business. */
1232                 drbd_err(device, "could not kmalloc() req\n");
1233                 bio->bi_status = BLK_STS_RESOURCE;
1234                 bio_endio(bio);
1235                 return ERR_PTR(-ENOMEM);
1236         }
1237         req->start_jif = start_jif;
1238
1239         if (!get_ldev(device)) {
1240                 bio_put(req->private_bio);
1241                 req->private_bio = NULL;
1242         }
1243
1244         /* Update disk stats */
1245         _drbd_start_io_acct(device, req);
1246
1247         /* process discards always from our submitter thread */
1248         if (bio_op(bio) == REQ_OP_WRITE_ZEROES ||
1249             bio_op(bio) == REQ_OP_DISCARD)
1250                 goto queue_for_submitter_thread;
1251
1252         if (rw == WRITE && req->private_bio && req->i.size
1253         && !test_bit(AL_SUSPENDED, &device->flags)) {
1254                 if (!drbd_al_begin_io_fastpath(device, &req->i))
1255                         goto queue_for_submitter_thread;
1256                 req->rq_state |= RQ_IN_ACT_LOG;
1257                 req->in_actlog_jif = jiffies;
1258         }
1259         return req;
1260
1261  queue_for_submitter_thread:
1262         atomic_inc(&device->ap_actlog_cnt);
1263         drbd_queue_write(device, req);
1264         return NULL;
1265 }
1266
1267 /* Require at least one path to current data.
1268  * We don't want to allow writes on C_STANDALONE D_INCONSISTENT:
1269  * We would not allow to read what was written,
1270  * we would not have bumped the data generation uuids,
1271  * we would cause data divergence for all the wrong reasons.
1272  *
1273  * If we don't see at least one D_UP_TO_DATE, we will fail this request,
1274  * which either returns EIO, or, if OND_SUSPEND_IO is set, suspends IO,
1275  * and queues for retry later.
1276  */
1277 static bool may_do_writes(struct drbd_device *device)
1278 {
1279         const union drbd_dev_state s = device->state;
1280         return s.disk == D_UP_TO_DATE || s.pdsk == D_UP_TO_DATE;
1281 }
1282
1283 struct drbd_plug_cb {
1284         struct blk_plug_cb cb;
1285         struct drbd_request *most_recent_req;
1286         /* do we need more? */
1287 };
1288
1289 static void drbd_unplug(struct blk_plug_cb *cb, bool from_schedule)
1290 {
1291         struct drbd_plug_cb *plug = container_of(cb, struct drbd_plug_cb, cb);
1292         struct drbd_resource *resource = plug->cb.data;
1293         struct drbd_request *req = plug->most_recent_req;
1294
1295         kfree(cb);
1296         if (!req)
1297                 return;
1298
1299         spin_lock_irq(&resource->req_lock);
1300         /* In case the sender did not process it yet, raise the flag to
1301          * have it followed with P_UNPLUG_REMOTE just after. */
1302         req->rq_state |= RQ_UNPLUG;
1303         /* but also queue a generic unplug */
1304         drbd_queue_unplug(req->device);
1305         kref_put(&req->kref, drbd_req_destroy);
1306         spin_unlock_irq(&resource->req_lock);
1307 }
1308
1309 static struct drbd_plug_cb* drbd_check_plugged(struct drbd_resource *resource)
1310 {
1311         /* A lot of text to say
1312          * return (struct drbd_plug_cb*)blk_check_plugged(); */
1313         struct drbd_plug_cb *plug;
1314         struct blk_plug_cb *cb = blk_check_plugged(drbd_unplug, resource, sizeof(*plug));
1315
1316         if (cb)
1317                 plug = container_of(cb, struct drbd_plug_cb, cb);
1318         else
1319                 plug = NULL;
1320         return plug;
1321 }
1322
1323 static void drbd_update_plug(struct drbd_plug_cb *plug, struct drbd_request *req)
1324 {
1325         struct drbd_request *tmp = plug->most_recent_req;
1326         /* Will be sent to some peer.
1327          * Remember to tag it with UNPLUG_REMOTE on unplug */
1328         kref_get(&req->kref);
1329         plug->most_recent_req = req;
1330         if (tmp)
1331                 kref_put(&tmp->kref, drbd_req_destroy);
1332 }
1333
1334 static void drbd_send_and_submit(struct drbd_device *device, struct drbd_request *req)
1335 {
1336         struct drbd_resource *resource = device->resource;
1337         const int rw = bio_data_dir(req->master_bio);
1338         struct bio_and_error m = { NULL, };
1339         bool no_remote = false;
1340         bool submit_private_bio = false;
1341
1342         spin_lock_irq(&resource->req_lock);
1343         if (rw == WRITE) {
1344                 /* This may temporarily give up the req_lock,
1345                  * but will re-aquire it before it returns here.
1346                  * Needs to be before the check on drbd_suspended() */
1347                 complete_conflicting_writes(req);
1348                 /* no more giving up req_lock from now on! */
1349
1350                 /* check for congestion, and potentially stop sending
1351                  * full data updates, but start sending "dirty bits" only. */
1352                 maybe_pull_ahead(device);
1353         }
1354
1355
1356         if (drbd_suspended(device)) {
1357                 /* push back and retry: */
1358                 req->rq_state |= RQ_POSTPONED;
1359                 if (req->private_bio) {
1360                         bio_put(req->private_bio);
1361                         req->private_bio = NULL;
1362                         put_ldev(device);
1363                 }
1364                 goto out;
1365         }
1366
1367         /* We fail READ early, if we can not serve it.
1368          * We must do this before req is registered on any lists.
1369          * Otherwise, drbd_req_complete() will queue failed READ for retry. */
1370         if (rw != WRITE) {
1371                 if (!do_remote_read(req) && !req->private_bio)
1372                         goto nodata;
1373         }
1374
1375         /* which transfer log epoch does this belong to? */
1376         req->epoch = atomic_read(&first_peer_device(device)->connection->current_tle_nr);
1377
1378         /* no point in adding empty flushes to the transfer log,
1379          * they are mapped to drbd barriers already. */
1380         if (likely(req->i.size!=0)) {
1381                 if (rw == WRITE)
1382                         first_peer_device(device)->connection->current_tle_writes++;
1383
1384                 list_add_tail(&req->tl_requests, &first_peer_device(device)->connection->transfer_log);
1385         }
1386
1387         if (rw == WRITE) {
1388                 if (req->private_bio && !may_do_writes(device)) {
1389                         bio_put(req->private_bio);
1390                         req->private_bio = NULL;
1391                         put_ldev(device);
1392                         goto nodata;
1393                 }
1394                 if (!drbd_process_write_request(req))
1395                         no_remote = true;
1396         } else {
1397                 /* We either have a private_bio, or we can read from remote.
1398                  * Otherwise we had done the goto nodata above. */
1399                 if (req->private_bio == NULL) {
1400                         _req_mod(req, TO_BE_SENT);
1401                         _req_mod(req, QUEUE_FOR_NET_READ);
1402                 } else
1403                         no_remote = true;
1404         }
1405
1406         if (no_remote == false) {
1407                 struct drbd_plug_cb *plug = drbd_check_plugged(resource);
1408                 if (plug)
1409                         drbd_update_plug(plug, req);
1410         }
1411
1412         /* If it took the fast path in drbd_request_prepare, add it here.
1413          * The slow path has added it already. */
1414         if (list_empty(&req->req_pending_master_completion))
1415                 list_add_tail(&req->req_pending_master_completion,
1416                         &device->pending_master_completion[rw == WRITE]);
1417         if (req->private_bio) {
1418                 /* needs to be marked within the same spinlock */
1419                 req->pre_submit_jif = jiffies;
1420                 list_add_tail(&req->req_pending_local,
1421                         &device->pending_completion[rw == WRITE]);
1422                 _req_mod(req, TO_BE_SUBMITTED);
1423                 /* but we need to give up the spinlock to submit */
1424                 submit_private_bio = true;
1425         } else if (no_remote) {
1426 nodata:
1427                 if (__ratelimit(&drbd_ratelimit_state))
1428                         drbd_err(device, "IO ERROR: neither local nor remote data, sector %llu+%u\n",
1429                                         (unsigned long long)req->i.sector, req->i.size >> 9);
1430                 /* A write may have been queued for send_oos, however.
1431                  * So we can not simply free it, we must go through drbd_req_put_completion_ref() */
1432         }
1433
1434 out:
1435         drbd_req_put_completion_ref(req, &m, 1);
1436         spin_unlock_irq(&resource->req_lock);
1437
1438         /* Even though above is a kref_put(), this is safe.
1439          * As long as we still need to submit our private bio,
1440          * we hold a completion ref, and the request cannot disappear.
1441          * If however this request did not even have a private bio to submit
1442          * (e.g. remote read), req may already be invalid now.
1443          * That's why we cannot check on req->private_bio. */
1444         if (submit_private_bio)
1445                 drbd_submit_req_private_bio(req);
1446         if (m.bio)
1447                 complete_master_bio(device, &m);
1448 }
1449
1450 void __drbd_make_request(struct drbd_device *device, struct bio *bio, unsigned long start_jif)
1451 {
1452         struct drbd_request *req = drbd_request_prepare(device, bio, start_jif);
1453         if (IS_ERR_OR_NULL(req))
1454                 return;
1455         drbd_send_and_submit(device, req);
1456 }
1457
1458 static void submit_fast_path(struct drbd_device *device, struct list_head *incoming)
1459 {
1460         struct blk_plug plug;
1461         struct drbd_request *req, *tmp;
1462
1463         blk_start_plug(&plug);
1464         list_for_each_entry_safe(req, tmp, incoming, tl_requests) {
1465                 const int rw = bio_data_dir(req->master_bio);
1466
1467                 if (rw == WRITE /* rw != WRITE should not even end up here! */
1468                 && req->private_bio && req->i.size
1469                 && !test_bit(AL_SUSPENDED, &device->flags)) {
1470                         if (!drbd_al_begin_io_fastpath(device, &req->i))
1471                                 continue;
1472
1473                         req->rq_state |= RQ_IN_ACT_LOG;
1474                         req->in_actlog_jif = jiffies;
1475                         atomic_dec(&device->ap_actlog_cnt);
1476                 }
1477
1478                 list_del_init(&req->tl_requests);
1479                 drbd_send_and_submit(device, req);
1480         }
1481         blk_finish_plug(&plug);
1482 }
1483
1484 static bool prepare_al_transaction_nonblock(struct drbd_device *device,
1485                                             struct list_head *incoming,
1486                                             struct list_head *pending,
1487                                             struct list_head *later)
1488 {
1489         struct drbd_request *req;
1490         int wake = 0;
1491         int err;
1492
1493         spin_lock_irq(&device->al_lock);
1494         while ((req = list_first_entry_or_null(incoming, struct drbd_request, tl_requests))) {
1495                 err = drbd_al_begin_io_nonblock(device, &req->i);
1496                 if (err == -ENOBUFS)
1497                         break;
1498                 if (err == -EBUSY)
1499                         wake = 1;
1500                 if (err)
1501                         list_move_tail(&req->tl_requests, later);
1502                 else
1503                         list_move_tail(&req->tl_requests, pending);
1504         }
1505         spin_unlock_irq(&device->al_lock);
1506         if (wake)
1507                 wake_up(&device->al_wait);
1508         return !list_empty(pending);
1509 }
1510
1511 static void send_and_submit_pending(struct drbd_device *device, struct list_head *pending)
1512 {
1513         struct blk_plug plug;
1514         struct drbd_request *req;
1515
1516         blk_start_plug(&plug);
1517         while ((req = list_first_entry_or_null(pending, struct drbd_request, tl_requests))) {
1518                 req->rq_state |= RQ_IN_ACT_LOG;
1519                 req->in_actlog_jif = jiffies;
1520                 atomic_dec(&device->ap_actlog_cnt);
1521                 list_del_init(&req->tl_requests);
1522                 drbd_send_and_submit(device, req);
1523         }
1524         blk_finish_plug(&plug);
1525 }
1526
1527 void do_submit(struct work_struct *ws)
1528 {
1529         struct drbd_device *device = container_of(ws, struct drbd_device, submit.worker);
1530         LIST_HEAD(incoming);    /* from drbd_make_request() */
1531         LIST_HEAD(pending);     /* to be submitted after next AL-transaction commit */
1532         LIST_HEAD(busy);        /* blocked by resync requests */
1533
1534         /* grab new incoming requests */
1535         spin_lock_irq(&device->resource->req_lock);
1536         list_splice_tail_init(&device->submit.writes, &incoming);
1537         spin_unlock_irq(&device->resource->req_lock);
1538
1539         for (;;) {
1540                 DEFINE_WAIT(wait);
1541
1542                 /* move used-to-be-busy back to front of incoming */
1543                 list_splice_init(&busy, &incoming);
1544                 submit_fast_path(device, &incoming);
1545                 if (list_empty(&incoming))
1546                         break;
1547
1548                 for (;;) {
1549                         prepare_to_wait(&device->al_wait, &wait, TASK_UNINTERRUPTIBLE);
1550
1551                         list_splice_init(&busy, &incoming);
1552                         prepare_al_transaction_nonblock(device, &incoming, &pending, &busy);
1553                         if (!list_empty(&pending))
1554                                 break;
1555
1556                         schedule();
1557
1558                         /* If all currently "hot" activity log extents are kept busy by
1559                          * incoming requests, we still must not totally starve new
1560                          * requests to "cold" extents.
1561                          * Something left on &incoming means there had not been
1562                          * enough update slots available, and the activity log
1563                          * has been marked as "starving".
1564                          *
1565                          * Try again now, without looking for new requests,
1566                          * effectively blocking all new requests until we made
1567                          * at least _some_ progress with what we currently have.
1568                          */
1569                         if (!list_empty(&incoming))
1570                                 continue;
1571
1572                         /* Nothing moved to pending, but nothing left
1573                          * on incoming: all moved to busy!
1574                          * Grab new and iterate. */
1575                         spin_lock_irq(&device->resource->req_lock);
1576                         list_splice_tail_init(&device->submit.writes, &incoming);
1577                         spin_unlock_irq(&device->resource->req_lock);
1578                 }
1579                 finish_wait(&device->al_wait, &wait);
1580
1581                 /* If the transaction was full, before all incoming requests
1582                  * had been processed, skip ahead to commit, and iterate
1583                  * without splicing in more incoming requests from upper layers.
1584                  *
1585                  * Else, if all incoming have been processed,
1586                  * they have become either "pending" (to be submitted after
1587                  * next transaction commit) or "busy" (blocked by resync).
1588                  *
1589                  * Maybe more was queued, while we prepared the transaction?
1590                  * Try to stuff those into this transaction as well.
1591                  * Be strictly non-blocking here,
1592                  * we already have something to commit.
1593                  *
1594                  * Commit if we don't make any more progres.
1595                  */
1596
1597                 while (list_empty(&incoming)) {
1598                         LIST_HEAD(more_pending);
1599                         LIST_HEAD(more_incoming);
1600                         bool made_progress;
1601
1602                         /* It is ok to look outside the lock,
1603                          * it's only an optimization anyways */
1604                         if (list_empty(&device->submit.writes))
1605                                 break;
1606
1607                         spin_lock_irq(&device->resource->req_lock);
1608                         list_splice_tail_init(&device->submit.writes, &more_incoming);
1609                         spin_unlock_irq(&device->resource->req_lock);
1610
1611                         if (list_empty(&more_incoming))
1612                                 break;
1613
1614                         made_progress = prepare_al_transaction_nonblock(device, &more_incoming, &more_pending, &busy);
1615
1616                         list_splice_tail_init(&more_pending, &pending);
1617                         list_splice_tail_init(&more_incoming, &incoming);
1618                         if (!made_progress)
1619                                 break;
1620                 }
1621
1622                 drbd_al_begin_io_commit(device);
1623                 send_and_submit_pending(device, &pending);
1624         }
1625 }
1626
1627 blk_qc_t drbd_make_request(struct request_queue *q, struct bio *bio)
1628 {
1629         struct drbd_device *device = (struct drbd_device *) q->queuedata;
1630         unsigned long start_jif;
1631
1632         blk_queue_split(q, &bio);
1633
1634         start_jif = jiffies;
1635
1636         /*
1637          * what we "blindly" assume:
1638          */
1639         D_ASSERT(device, IS_ALIGNED(bio->bi_iter.bi_size, 512));
1640
1641         inc_ap_bio(device);
1642         __drbd_make_request(device, bio, start_jif);
1643         return BLK_QC_T_NONE;
1644 }
1645
1646 static bool net_timeout_reached(struct drbd_request *net_req,
1647                 struct drbd_connection *connection,
1648                 unsigned long now, unsigned long ent,
1649                 unsigned int ko_count, unsigned int timeout)
1650 {
1651         struct drbd_device *device = net_req->device;
1652
1653         if (!time_after(now, net_req->pre_send_jif + ent))
1654                 return false;
1655
1656         if (time_in_range(now, connection->last_reconnect_jif, connection->last_reconnect_jif + ent))
1657                 return false;
1658
1659         if (net_req->rq_state & RQ_NET_PENDING) {
1660                 drbd_warn(device, "Remote failed to finish a request within %ums > ko-count (%u) * timeout (%u * 0.1s)\n",
1661                         jiffies_to_msecs(now - net_req->pre_send_jif), ko_count, timeout);
1662                 return true;
1663         }
1664
1665         /* We received an ACK already (or are using protocol A),
1666          * but are waiting for the epoch closing barrier ack.
1667          * Check if we sent the barrier already.  We should not blame the peer
1668          * for being unresponsive, if we did not even ask it yet. */
1669         if (net_req->epoch == connection->send.current_epoch_nr) {
1670                 drbd_warn(device,
1671                         "We did not send a P_BARRIER for %ums > ko-count (%u) * timeout (%u * 0.1s); drbd kernel thread blocked?\n",
1672                         jiffies_to_msecs(now - net_req->pre_send_jif), ko_count, timeout);
1673                 return false;
1674         }
1675
1676         /* Worst case: we may have been blocked for whatever reason, then
1677          * suddenly are able to send a lot of requests (and epoch separating
1678          * barriers) in quick succession.
1679          * The timestamp of the net_req may be much too old and not correspond
1680          * to the sending time of the relevant unack'ed barrier packet, so
1681          * would trigger a spurious timeout.  The latest barrier packet may
1682          * have a too recent timestamp to trigger the timeout, potentially miss
1683          * a timeout.  Right now we don't have a place to conveniently store
1684          * these timestamps.
1685          * But in this particular situation, the application requests are still
1686          * completed to upper layers, DRBD should still "feel" responsive.
1687          * No need yet to kill this connection, it may still recover.
1688          * If not, eventually we will have queued enough into the network for
1689          * us to block. From that point of view, the timestamp of the last sent
1690          * barrier packet is relevant enough.
1691          */
1692         if (time_after(now, connection->send.last_sent_barrier_jif + ent)) {
1693                 drbd_warn(device, "Remote failed to answer a P_BARRIER (sent at %lu jif; now=%lu jif) within %ums > ko-count (%u) * timeout (%u * 0.1s)\n",
1694                         connection->send.last_sent_barrier_jif, now,
1695                         jiffies_to_msecs(now - connection->send.last_sent_barrier_jif), ko_count, timeout);
1696                 return true;
1697         }
1698         return false;
1699 }
1700
1701 /* A request is considered timed out, if
1702  * - we have some effective timeout from the configuration,
1703  *   with some state restrictions applied,
1704  * - the oldest request is waiting for a response from the network
1705  *   resp. the local disk,
1706  * - the oldest request is in fact older than the effective timeout,
1707  * - the connection was established (resp. disk was attached)
1708  *   for longer than the timeout already.
1709  * Note that for 32bit jiffies and very stable connections/disks,
1710  * we may have a wrap around, which is catched by
1711  *   !time_in_range(now, last_..._jif, last_..._jif + timeout).
1712  *
1713  * Side effect: once per 32bit wrap-around interval, which means every
1714  * ~198 days with 250 HZ, we have a window where the timeout would need
1715  * to expire twice (worst case) to become effective. Good enough.
1716  */
1717
1718 void request_timer_fn(unsigned long data)
1719 {
1720         struct drbd_device *device = (struct drbd_device *) data;
1721         struct drbd_connection *connection = first_peer_device(device)->connection;
1722         struct drbd_request *req_read, *req_write, *req_peer; /* oldest request */
1723         struct net_conf *nc;
1724         unsigned long oldest_submit_jif;
1725         unsigned long ent = 0, dt = 0, et, nt; /* effective timeout = ko_count * timeout */
1726         unsigned long now;
1727         unsigned int ko_count = 0, timeout = 0;
1728
1729         rcu_read_lock();
1730         nc = rcu_dereference(connection->net_conf);
1731         if (nc && device->state.conn >= C_WF_REPORT_PARAMS) {
1732                 ko_count = nc->ko_count;
1733                 timeout = nc->timeout;
1734         }
1735
1736         if (get_ldev(device)) { /* implicit state.disk >= D_INCONSISTENT */
1737                 dt = rcu_dereference(device->ldev->disk_conf)->disk_timeout * HZ / 10;
1738                 put_ldev(device);
1739         }
1740         rcu_read_unlock();
1741
1742
1743         ent = timeout * HZ/10 * ko_count;
1744         et = min_not_zero(dt, ent);
1745
1746         if (!et)
1747                 return; /* Recurring timer stopped */
1748
1749         now = jiffies;
1750         nt = now + et;
1751
1752         spin_lock_irq(&device->resource->req_lock);
1753         req_read = list_first_entry_or_null(&device->pending_completion[0], struct drbd_request, req_pending_local);
1754         req_write = list_first_entry_or_null(&device->pending_completion[1], struct drbd_request, req_pending_local);
1755
1756         /* maybe the oldest request waiting for the peer is in fact still
1757          * blocking in tcp sendmsg.  That's ok, though, that's handled via the
1758          * socket send timeout, requesting a ping, and bumping ko-count in
1759          * we_should_drop_the_connection().
1760          */
1761
1762         /* check the oldest request we did successfully sent,
1763          * but which is still waiting for an ACK. */
1764         req_peer = connection->req_ack_pending;
1765
1766         /* if we don't have such request (e.g. protocoll A)
1767          * check the oldest requests which is still waiting on its epoch
1768          * closing barrier ack. */
1769         if (!req_peer)
1770                 req_peer = connection->req_not_net_done;
1771
1772         /* evaluate the oldest peer request only in one timer! */
1773         if (req_peer && req_peer->device != device)
1774                 req_peer = NULL;
1775
1776         /* do we have something to evaluate? */
1777         if (req_peer == NULL && req_write == NULL && req_read == NULL)
1778                 goto out;
1779
1780         oldest_submit_jif =
1781                 (req_write && req_read)
1782                 ? ( time_before(req_write->pre_submit_jif, req_read->pre_submit_jif)
1783                   ? req_write->pre_submit_jif : req_read->pre_submit_jif )
1784                 : req_write ? req_write->pre_submit_jif
1785                 : req_read ? req_read->pre_submit_jif : now;
1786
1787         if (ent && req_peer && net_timeout_reached(req_peer, connection, now, ent, ko_count, timeout))
1788                 _conn_request_state(connection, NS(conn, C_TIMEOUT), CS_VERBOSE | CS_HARD);
1789
1790         if (dt && oldest_submit_jif != now &&
1791                  time_after(now, oldest_submit_jif + dt) &&
1792                 !time_in_range(now, device->last_reattach_jif, device->last_reattach_jif + dt)) {
1793                 drbd_warn(device, "Local backing device failed to meet the disk-timeout\n");
1794                 __drbd_chk_io_error(device, DRBD_FORCE_DETACH);
1795         }
1796
1797         /* Reschedule timer for the nearest not already expired timeout.
1798          * Fallback to now + min(effective network timeout, disk timeout). */
1799         ent = (ent && req_peer && time_before(now, req_peer->pre_send_jif + ent))
1800                 ? req_peer->pre_send_jif + ent : now + et;
1801         dt = (dt && oldest_submit_jif != now && time_before(now, oldest_submit_jif + dt))
1802                 ? oldest_submit_jif + dt : now + et;
1803         nt = time_before(ent, dt) ? ent : dt;
1804 out:
1805         spin_unlock_irq(&device->resource->req_lock);
1806         mod_timer(&device->request_timer, nt);
1807 }