fs/bcachefs/move.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include "bcachefs.h"
   4 #include "alloc_background.h"
   5 #include "alloc_foreground.h"
   6 #include "backpointers.h"
   7 #include "bkey_buf.h"
   8 #include "btree_gc.h"
   9 #include "btree_io.h"
  10 #include "btree_update.h"
  11 #include "btree_update_interior.h"
  12 #include "btree_write_buffer.h"
  13 #include "compress.h"
  14 #include "disk_groups.h"
  15 #include "ec.h"
  16 #include "errcode.h"
  17 #include "error.h"
  18 #include "inode.h"
  19 #include "io_read.h"
  20 #include "io_write.h"
  21 #include "journal_reclaim.h"
  22 #include "keylist.h"
  23 #include "move.h"
  24 #include "rebalance.h"
  25 #include "reflink.h"
  26 #include "replicas.h"
  27 #include "snapshot.h"
  28 #include "super-io.h"
  29 #include "trace.h"
  30
  31 #include <linux/ioprio.h>
  32 #include <linux/kthread.h>
  33
  34 const char * const bch2_data_ops_strs[] = {
  35 #define x(t, n, ...) [n] = #t,
  36         BCH_DATA_OPS()
  37 #undef x
  38         NULL
  39 };
  40
  41 static void trace_move_extent2(struct bch_fs *c, struct bkey_s_c k,
  42                                struct bch_io_opts *io_opts,
  43                                struct data_update_opts *data_opts)
  44 {
  45         if (trace_move_extent_enabled()) {
  46                 struct printbuf buf = PRINTBUF;
  47
  48                 bch2_bkey_val_to_text(&buf, c, k);
  49                 prt_newline(&buf);
  50                 bch2_data_update_opts_to_text(&buf, c, io_opts, data_opts);
  51                 trace_move_extent(c, buf.buf);
  52                 printbuf_exit(&buf);
  53         }
  54 }
  55
  56 static void trace_move_extent_read2(struct bch_fs *c, struct bkey_s_c k)
  57 {
  58         if (trace_move_extent_read_enabled()) {
  59                 struct printbuf buf = PRINTBUF;
  60
  61                 bch2_bkey_val_to_text(&buf, c, k);
  62                 trace_move_extent_read(c, buf.buf);
  63                 printbuf_exit(&buf);
  64         }
  65 }
  66
  67 struct moving_io {
  68         struct list_head                read_list;
  69         struct list_head                io_list;
  70         struct move_bucket_in_flight    *b;
  71         struct closure                  cl;
  72         bool                            read_completed;
  73
  74         unsigned                        read_sectors;
  75         unsigned                        write_sectors;
  76
  77         struct bch_read_bio             rbio;
  78
  79         struct data_update              write;
  80         /* Must be last since it is variable size */
  81         struct bio_vec                  bi_inline_vecs[];
  82 };
  83
  84 static void move_free(struct moving_io *io)
  85 {
  86         struct moving_context *ctxt = io->write.ctxt;
  87
  88         if (io->b)
  89                 atomic_dec(&io->b->count);
  90
  91         bch2_data_update_exit(&io->write);
  92
  93         mutex_lock(&ctxt->lock);
  94         list_del(&io->io_list);
  95         wake_up(&ctxt->wait);
  96         mutex_unlock(&ctxt->lock);
  97
  98         kfree(io);
  99 }
 100
 101 static void move_write_done(struct bch_write_op *op)
 102 {
 103         struct moving_io *io = container_of(op, struct moving_io, write.op);
 104         struct moving_context *ctxt = io->write.ctxt;
 105
 106         if (io->write.op.error)
 107                 ctxt->write_error = true;
 108
 109         atomic_sub(io->write_sectors, &io->write.ctxt->write_sectors);
 110         atomic_dec(&io->write.ctxt->write_ios);
 111         move_free(io);
 112         closure_put(&ctxt->cl);
 113 }
 114
 115 static void move_write(struct moving_io *io)
 116 {
 117         if (unlikely(io->rbio.bio.bi_status || io->rbio.hole)) {
 118                 move_free(io);
 119                 return;
 120         }
 121
 122         if (trace_move_extent_write_enabled()) {
 123                 struct bch_fs *c = io->write.op.c;
 124                 struct printbuf buf = PRINTBUF;
 125
 126                 bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(io->write.k.k));
 127                 trace_move_extent_write(c, buf.buf);
 128                 printbuf_exit(&buf);
 129         }
 130
 131         closure_get(&io->write.ctxt->cl);
 132         atomic_add(io->write_sectors, &io->write.ctxt->write_sectors);
 133         atomic_inc(&io->write.ctxt->write_ios);
 134
 135         bch2_data_update_read_done(&io->write, io->rbio.pick.crc);
 136 }
 137
 138 struct moving_io *bch2_moving_ctxt_next_pending_write(struct moving_context *ctxt)
 139 {
 140         struct moving_io *io =
 141                 list_first_entry_or_null(&ctxt->reads, struct moving_io, read_list);
 142
 143         return io && io->read_completed ? io : NULL;
 144 }
 145
 146 static void move_read_endio(struct bio *bio)
 147 {
 148         struct moving_io *io = container_of(bio, struct moving_io, rbio.bio);
 149         struct moving_context *ctxt = io->write.ctxt;
 150
 151         atomic_sub(io->read_sectors, &ctxt->read_sectors);
 152         atomic_dec(&ctxt->read_ios);
 153         io->read_completed = true;
 154
 155         wake_up(&ctxt->wait);
 156         closure_put(&ctxt->cl);
 157 }
 158
 159 void bch2_moving_ctxt_do_pending_writes(struct moving_context *ctxt)
 160 {
 161         struct moving_io *io;
 162
 163         while ((io = bch2_moving_ctxt_next_pending_write(ctxt))) {
 164                 bch2_trans_unlock_long(ctxt->trans);
 165                 list_del(&io->read_list);
 166                 move_write(io);
 167         }
 168 }
 169
 170 void bch2_move_ctxt_wait_for_io(struct moving_context *ctxt)
 171 {
 172         unsigned sectors_pending = atomic_read(&ctxt->write_sectors);
 173
 174         move_ctxt_wait_event(ctxt,
 175                 !atomic_read(&ctxt->write_sectors) ||
 176                 atomic_read(&ctxt->write_sectors) != sectors_pending);
 177 }
 178
 179 void bch2_moving_ctxt_flush_all(struct moving_context *ctxt)
 180 {
 181         move_ctxt_wait_event(ctxt, list_empty(&ctxt->reads));
 182         bch2_trans_unlock_long(ctxt->trans);
 183         closure_sync(&ctxt->cl);
 184 }
 185
 186 void bch2_moving_ctxt_exit(struct moving_context *ctxt)
 187 {
 188         struct bch_fs *c = ctxt->trans->c;
 189
 190         bch2_moving_ctxt_flush_all(ctxt);
 191
 192         EBUG_ON(atomic_read(&ctxt->write_sectors));
 193         EBUG_ON(atomic_read(&ctxt->write_ios));
 194         EBUG_ON(atomic_read(&ctxt->read_sectors));
 195         EBUG_ON(atomic_read(&ctxt->read_ios));
 196
 197         mutex_lock(&c->moving_context_lock);
 198         list_del(&ctxt->list);
 199         mutex_unlock(&c->moving_context_lock);
 200
 201         /*
 202          * Generally, releasing a transaction within a transaction restart means
 203          * an unhandled transaction restart: but this can happen legitimately
 204          * within the move code, e.g. when bch2_move_ratelimit() tells us to
 205          * exit before we've retried
 206          */
 207         bch2_trans_begin(ctxt->trans);
 208         bch2_trans_put(ctxt->trans);
 209         memset(ctxt, 0, sizeof(*ctxt));
 210 }
 211
 212 void bch2_moving_ctxt_init(struct moving_context *ctxt,
 213                            struct bch_fs *c,
 214                            struct bch_ratelimit *rate,
 215                            struct bch_move_stats *stats,
 216                            struct write_point_specifier wp,
 217                            bool wait_on_copygc)
 218 {
 219         memset(ctxt, 0, sizeof(*ctxt));
 220
 221         ctxt->trans     = bch2_trans_get(c);
 222         ctxt->fn        = (void *) _RET_IP_;
 223         ctxt->rate      = rate;
 224         ctxt->stats     = stats;
 225         ctxt->wp        = wp;
 226         ctxt->wait_on_copygc = wait_on_copygc;
 227
 228         closure_init_stack(&ctxt->cl);
 229
 230         mutex_init(&ctxt->lock);
 231         INIT_LIST_HEAD(&ctxt->reads);
 232         INIT_LIST_HEAD(&ctxt->ios);
 233         init_waitqueue_head(&ctxt->wait);
 234
 235         mutex_lock(&c->moving_context_lock);
 236         list_add(&ctxt->list, &c->moving_context_list);
 237         mutex_unlock(&c->moving_context_lock);
 238 }
 239
 240 void bch2_move_stats_exit(struct bch_move_stats *stats, struct bch_fs *c)
 241 {
 242         trace_move_data(c, stats);
 243 }
 244
 245 void bch2_move_stats_init(struct bch_move_stats *stats, const char *name)
 246 {
 247         memset(stats, 0, sizeof(*stats));
 248         stats->data_type = BCH_DATA_user;
 249         scnprintf(stats->name, sizeof(stats->name), "%s", name);
 250 }
 251
 252 int bch2_move_extent(struct moving_context *ctxt,
 253                      struct move_bucket_in_flight *bucket_in_flight,
 254                      struct btree_iter *iter,
 255                      struct bkey_s_c k,
 256                      struct bch_io_opts io_opts,
 257                      struct data_update_opts data_opts)
 258 {
 259         struct btree_trans *trans = ctxt->trans;
 260         struct bch_fs *c = trans->c;
 261         struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
 262         struct moving_io *io;
 263         const union bch_extent_entry *entry;
 264         struct extent_ptr_decoded p;
 265         unsigned sectors = k.k->size, pages;
 266         int ret = -ENOMEM;
 267
 268         trace_move_extent2(c, k, &io_opts, &data_opts);
 269
 270         if (ctxt->stats)
 271                 ctxt->stats->pos = BBPOS(iter->btree_id, iter->pos);
 272
 273         bch2_data_update_opts_normalize(k, &data_opts);
 274
 275         if (!data_opts.rewrite_ptrs &&
 276             !data_opts.extra_replicas) {
 277                 if (data_opts.kill_ptrs)
 278                         return bch2_extent_drop_ptrs(trans, iter, k, &io_opts, &data_opts);
 279                 return 0;
 280         }
 281
 282         /*
 283          * Before memory allocations & taking nocow locks in
 284          * bch2_data_update_init():
 285          */
 286         bch2_trans_unlock(trans);
 287
 288         /* write path might have to decompress data: */
 289         bkey_for_each_ptr_decode(k.k, ptrs, p, entry)
 290                 sectors = max_t(unsigned, sectors, p.crc.uncompressed_size);
 291
 292         pages = DIV_ROUND_UP(sectors, PAGE_SECTORS);
 293         io = kzalloc(sizeof(struct moving_io) +
 294                      sizeof(struct bio_vec) * pages, GFP_KERNEL);
 295         if (!io)
 296                 goto err;
 297
 298         INIT_LIST_HEAD(&io->io_list);
 299         io->write.ctxt          = ctxt;
 300         io->read_sectors        = k.k->size;
 301         io->write_sectors       = k.k->size;
 302
 303         bio_init(&io->write.op.wbio.bio, NULL, io->bi_inline_vecs, pages, 0);
 304         io->write.op.wbio.bio.bi_ioprio =
 305                      IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0);
 306
 307         if (bch2_bio_alloc_pages(&io->write.op.wbio.bio, sectors << 9,
 308                                  GFP_KERNEL))
 309                 goto err_free;
 310
 311         io->rbio.c              = c;
 312         io->rbio.opts           = io_opts;
 313         bio_init(&io->rbio.bio, NULL, io->bi_inline_vecs, pages, 0);
 314         io->rbio.bio.bi_vcnt = pages;
 315         io->rbio.bio.bi_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0);
 316         io->rbio.bio.bi_iter.bi_size = sectors << 9;
 317
 318         io->rbio.bio.bi_opf             = REQ_OP_READ;
 319         io->rbio.bio.bi_iter.bi_sector  = bkey_start_offset(k.k);
 320         io->rbio.bio.bi_end_io          = move_read_endio;
 321
 322         ret = bch2_data_update_init(trans, iter, ctxt, &io->write, ctxt->wp,
 323                                     io_opts, data_opts, iter->btree_id, k);
 324         if (ret)
 325                 goto err_free_pages;
 326
 327         io->write.op.end_io = move_write_done;
 328
 329         if (ctxt->rate)
 330                 bch2_ratelimit_increment(ctxt->rate, k.k->size);
 331
 332         if (ctxt->stats) {
 333                 atomic64_inc(&ctxt->stats->keys_moved);
 334                 atomic64_add(k.k->size, &ctxt->stats->sectors_moved);
 335         }
 336
 337         if (bucket_in_flight) {
 338                 io->b = bucket_in_flight;
 339                 atomic_inc(&io->b->count);
 340         }
 341
 342         this_cpu_add(c->counters[BCH_COUNTER_io_move], k.k->size);
 343         this_cpu_add(c->counters[BCH_COUNTER_move_extent_read], k.k->size);
 344         trace_move_extent_read2(c, k);
 345
 346         mutex_lock(&ctxt->lock);
 347         atomic_add(io->read_sectors, &ctxt->read_sectors);
 348         atomic_inc(&ctxt->read_ios);
 349
 350         list_add_tail(&io->read_list, &ctxt->reads);
 351         list_add_tail(&io->io_list, &ctxt->ios);
 352         mutex_unlock(&ctxt->lock);
 353
 354         /*
 355          * dropped by move_read_endio() - guards against use after free of
 356          * ctxt when doing wakeup
 357          */
 358         closure_get(&ctxt->cl);
 359         bch2_read_extent(trans, &io->rbio,
 360                          bkey_start_pos(k.k),
 361                          iter->btree_id, k, 0,
 362                          BCH_READ_NODECODE|
 363                          BCH_READ_LAST_FRAGMENT);
 364         return 0;
 365 err_free_pages:
 366         bio_free_pages(&io->write.op.wbio.bio);
 367 err_free:
 368         kfree(io);
 369 err:
 370         if (ret == -BCH_ERR_data_update_done)
 371                 return 0;
 372
 373         if (bch2_err_matches(ret, EROFS) ||
 374             bch2_err_matches(ret, BCH_ERR_transaction_restart))
 375                 return ret;
 376
 377         count_event(c, move_extent_start_fail);
 378
 379         if (trace_move_extent_start_fail_enabled()) {
 380                 struct printbuf buf = PRINTBUF;
 381
 382                 bch2_bkey_val_to_text(&buf, c, k);
 383                 prt_str(&buf, ": ");
 384                 prt_str(&buf, bch2_err_str(ret));
 385                 trace_move_extent_start_fail(c, buf.buf);
 386                 printbuf_exit(&buf);
 387         }
 388         return ret;
 389 }
 390
 391 static struct bch_io_opts *bch2_move_get_io_opts(struct btree_trans *trans,
 392                           struct per_snapshot_io_opts *io_opts,
 393                           struct bpos extent_pos, /* extent_iter, extent_k may be in reflink btree */
 394                           struct btree_iter *extent_iter,
 395                           struct bkey_s_c extent_k)
 396 {
 397         struct bch_fs *c = trans->c;
 398         u32 restart_count = trans->restart_count;
 399         struct bch_io_opts *opts_ret = &io_opts->fs_io_opts;
 400         int ret = 0;
 401
 402         if (extent_k.k->type == KEY_TYPE_reflink_v)
 403                 goto out;
 404
 405         if (io_opts->cur_inum != extent_pos.inode) {
 406                 io_opts->d.nr = 0;
 407
 408                 ret = for_each_btree_key(trans, iter, BTREE_ID_inodes, POS(0, extent_pos.inode),
 409                                          BTREE_ITER_all_snapshots, k, ({
 410                         if (k.k->p.offset != extent_pos.inode)
 411                                 break;
 412
 413                         if (!bkey_is_inode(k.k))
 414                                 continue;
 415
 416                         struct bch_inode_unpacked inode;
 417                         _ret3 = bch2_inode_unpack(k, &inode);
 418                         if (_ret3)
 419                                 break;
 420
 421                         struct snapshot_io_opts_entry e = { .snapshot = k.k->p.snapshot };
 422                         bch2_inode_opts_get(&e.io_opts, trans->c, &inode);
 423
 424                         darray_push(&io_opts->d, e);
 425                 }));
 426                 io_opts->cur_inum = extent_pos.inode;
 427         }
 428
 429         ret = ret ?: trans_was_restarted(trans, restart_count);
 430         if (ret)
 431                 return ERR_PTR(ret);
 432
 433         if (extent_k.k->p.snapshot)
 434                 darray_for_each(io_opts->d, i)
 435                         if (bch2_snapshot_is_ancestor(c, extent_k.k->p.snapshot, i->snapshot)) {
 436                                 opts_ret = &i->io_opts;
 437                                 break;
 438                         }
 439 out:
 440         ret = bch2_get_update_rebalance_opts(trans, opts_ret, extent_iter, extent_k);
 441         if (ret)
 442                 return ERR_PTR(ret);
 443         return opts_ret;
 444 }
 445
 446 int bch2_move_get_io_opts_one(struct btree_trans *trans,
 447                               struct bch_io_opts *io_opts,
 448                               struct btree_iter *extent_iter,
 449                               struct bkey_s_c extent_k)
 450 {
 451         struct bch_fs *c = trans->c;
 452
 453         *io_opts = bch2_opts_to_inode_opts(c->opts);
 454
 455         /* reflink btree? */
 456         if (!extent_k.k->p.inode)
 457                 goto out;
 458
 459         struct btree_iter inode_iter;
 460         struct bkey_s_c inode_k = bch2_bkey_get_iter(trans, &inode_iter, BTREE_ID_inodes,
 461                                SPOS(0, extent_k.k->p.inode, extent_k.k->p.snapshot),
 462                                BTREE_ITER_cached);
 463         int ret = bkey_err(inode_k);
 464         if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 465                 return ret;
 466
 467         if (!ret && bkey_is_inode(inode_k.k)) {
 468                 struct bch_inode_unpacked inode;
 469                 bch2_inode_unpack(inode_k, &inode);
 470                 bch2_inode_opts_get(io_opts, c, &inode);
 471         }
 472         bch2_trans_iter_exit(trans, &inode_iter);
 473 out:
 474         return bch2_get_update_rebalance_opts(trans, io_opts, extent_iter, extent_k);
 475 }
 476
 477 int bch2_move_ratelimit(struct moving_context *ctxt)
 478 {
 479         struct bch_fs *c = ctxt->trans->c;
 480         bool is_kthread = current->flags & PF_KTHREAD;
 481         u64 delay;
 482
 483         if (ctxt->wait_on_copygc && c->copygc_running) {
 484                 bch2_moving_ctxt_flush_all(ctxt);
 485                 wait_event_killable(c->copygc_running_wq,
 486                                     !c->copygc_running ||
 487                                     (is_kthread && kthread_should_stop()));
 488         }
 489
 490         do {
 491                 delay = ctxt->rate ? bch2_ratelimit_delay(ctxt->rate) : 0;
 492
 493                 if (is_kthread && kthread_should_stop())
 494                         return 1;
 495
 496                 if (delay)
 497                         move_ctxt_wait_event_timeout(ctxt,
 498                                         freezing(current) ||
 499                                         (is_kthread && kthread_should_stop()),
 500                                         delay);
 501
 502                 if (unlikely(freezing(current))) {
 503                         bch2_moving_ctxt_flush_all(ctxt);
 504                         try_to_freeze();
 505                 }
 506         } while (delay);
 507
 508         /*
 509          * XXX: these limits really ought to be per device, SSDs and hard drives
 510          * will want different limits
 511          */
 512         move_ctxt_wait_event(ctxt,
 513                 atomic_read(&ctxt->write_sectors) < c->opts.move_bytes_in_flight >> 9 &&
 514                 atomic_read(&ctxt->read_sectors) < c->opts.move_bytes_in_flight >> 9 &&
 515                 atomic_read(&ctxt->write_ios) < c->opts.move_ios_in_flight &&
 516                 atomic_read(&ctxt->read_ios) < c->opts.move_ios_in_flight);
 517
 518         return 0;
 519 }
 520
 521 static int bch2_move_data_btree(struct moving_context *ctxt,
 522                                 struct bpos start,
 523                                 struct bpos end,
 524                                 move_pred_fn pred, void *arg,
 525                                 enum btree_id btree_id)
 526 {
 527         struct btree_trans *trans = ctxt->trans;
 528         struct bch_fs *c = trans->c;
 529         struct per_snapshot_io_opts snapshot_io_opts;
 530         struct bch_io_opts *io_opts;
 531         struct bkey_buf sk;
 532         struct btree_iter iter, reflink_iter = {};
 533         struct bkey_s_c k;
 534         struct data_update_opts data_opts;
 535         /*
 536          * If we're moving a single file, also process reflinked data it points
 537          * to (this includes propagating changed io_opts from the inode to the
 538          * extent):
 539          */
 540         bool walk_indirect = start.inode == end.inode;
 541         int ret = 0, ret2;
 542
 543         per_snapshot_io_opts_init(&snapshot_io_opts, c);
 544         bch2_bkey_buf_init(&sk);
 545
 546         if (ctxt->stats) {
 547                 ctxt->stats->data_type  = BCH_DATA_user;
 548                 ctxt->stats->pos        = BBPOS(btree_id, start);
 549         }
 550
 551         bch2_trans_begin(trans);
 552         bch2_trans_iter_init(trans, &iter, btree_id, start,
 553                              BTREE_ITER_prefetch|
 554                              BTREE_ITER_all_snapshots);
 555
 556         if (ctxt->rate)
 557                 bch2_ratelimit_reset(ctxt->rate);
 558
 559         while (!bch2_move_ratelimit(ctxt)) {
 560                 struct btree_iter *extent_iter = &iter;
 561
 562                 bch2_trans_begin(trans);
 563
 564                 k = bch2_btree_iter_peek(&iter);
 565                 if (!k.k)
 566                         break;
 567
 568                 ret = bkey_err(k);
 569                 if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 570                         continue;
 571                 if (ret)
 572                         break;
 573
 574                 if (bkey_ge(bkey_start_pos(k.k), end))
 575                         break;
 576
 577                 if (ctxt->stats)
 578                         ctxt->stats->pos = BBPOS(iter.btree_id, iter.pos);
 579
 580                 if (walk_indirect &&
 581                     k.k->type == KEY_TYPE_reflink_p &&
 582                     REFLINK_P_MAY_UPDATE_OPTIONS(bkey_s_c_to_reflink_p(k).v)) {
 583                         struct bkey_s_c_reflink_p p = bkey_s_c_to_reflink_p(k);
 584                         s64 offset_into_extent  = iter.pos.offset - bkey_start_offset(k.k);
 585
 586                         bch2_trans_iter_exit(trans, &reflink_iter);
 587                         k = bch2_lookup_indirect_extent(trans, &reflink_iter, &offset_into_extent, p, true, 0);
 588                         ret = bkey_err(k);
 589                         if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 590                                 continue;
 591                         if (ret)
 592                                 break;
 593
 594                         if (bkey_deleted(k.k))
 595                                 goto next_nondata;
 596
 597                         /*
 598                          * XXX: reflink pointers may point to multiple indirect
 599                          * extents, so don't advance past the entire reflink
 600                          * pointer - need to fixup iter->k
 601                          */
 602                         extent_iter = &reflink_iter;
 603                 }
 604
 605                 if (!bkey_extent_is_direct_data(k.k))
 606                         goto next_nondata;
 607
 608                 io_opts = bch2_move_get_io_opts(trans, &snapshot_io_opts,
 609                                                 iter.pos, extent_iter, k);
 610                 ret = PTR_ERR_OR_ZERO(io_opts);
 611                 if (ret)
 612                         continue;
 613
 614                 memset(&data_opts, 0, sizeof(data_opts));
 615                 if (!pred(c, arg, k, io_opts, &data_opts))
 616                         goto next;
 617
 618                 /*
 619                  * The iterator gets unlocked by __bch2_read_extent - need to
 620                  * save a copy of @k elsewhere:
 621                  */
 622                 bch2_bkey_buf_reassemble(&sk, c, k);
 623                 k = bkey_i_to_s_c(sk.k);
 624
 625                 ret2 = bch2_move_extent(ctxt, NULL, extent_iter, k, *io_opts, data_opts);
 626                 if (ret2) {
 627                         if (bch2_err_matches(ret2, BCH_ERR_transaction_restart))
 628                                 continue;
 629
 630                         if (ret2 == -ENOMEM) {
 631                                 /* memory allocation failure, wait for some IO to finish */
 632                                 bch2_move_ctxt_wait_for_io(ctxt);
 633                                 continue;
 634                         }
 635
 636                         /* XXX signal failure */
 637                         goto next;
 638                 }
 639 next:
 640                 if (ctxt->stats)
 641                         atomic64_add(k.k->size, &ctxt->stats->sectors_seen);
 642 next_nondata:
 643                 bch2_btree_iter_advance(&iter);
 644         }
 645
 646         bch2_trans_iter_exit(trans, &reflink_iter);
 647         bch2_trans_iter_exit(trans, &iter);
 648         bch2_bkey_buf_exit(&sk, c);
 649         per_snapshot_io_opts_exit(&snapshot_io_opts);
 650
 651         return ret;
 652 }
 653
 654 int __bch2_move_data(struct moving_context *ctxt,
 655                      struct bbpos start,
 656                      struct bbpos end,
 657                      move_pred_fn pred, void *arg)
 658 {
 659         struct bch_fs *c = ctxt->trans->c;
 660         enum btree_id id;
 661         int ret = 0;
 662
 663         for (id = start.btree;
 664              id <= min_t(unsigned, end.btree, btree_id_nr_alive(c) - 1);
 665              id++) {
 666                 ctxt->stats->pos = BBPOS(id, POS_MIN);
 667
 668                 if (!btree_type_has_ptrs(id) ||
 669                     !bch2_btree_id_root(c, id)->b)
 670                         continue;
 671
 672                 ret = bch2_move_data_btree(ctxt,
 673                                        id == start.btree ? start.pos : POS_MIN,
 674                                        id == end.btree   ? end.pos   : POS_MAX,
 675                                        pred, arg, id);
 676                 if (ret)
 677                         break;
 678         }
 679
 680         return ret;
 681 }
 682
 683 int bch2_move_data(struct bch_fs *c,
 684                    struct bbpos start,
 685                    struct bbpos end,
 686                    struct bch_ratelimit *rate,
 687                    struct bch_move_stats *stats,
 688                    struct write_point_specifier wp,
 689                    bool wait_on_copygc,
 690                    move_pred_fn pred, void *arg)
 691 {
 692
 693         struct moving_context ctxt;
 694         int ret;
 695
 696         bch2_moving_ctxt_init(&ctxt, c, rate, stats, wp, wait_on_copygc);
 697         ret = __bch2_move_data(&ctxt, start, end, pred, arg);
 698         bch2_moving_ctxt_exit(&ctxt);
 699
 700         return ret;
 701 }
 702
 703 int bch2_evacuate_bucket(struct moving_context *ctxt,
 704                            struct move_bucket_in_flight *bucket_in_flight,
 705                            struct bpos bucket, int gen,
 706                            struct data_update_opts _data_opts)
 707 {
 708         struct btree_trans *trans = ctxt->trans;
 709         struct bch_fs *c = trans->c;
 710         bool is_kthread = current->flags & PF_KTHREAD;
 711         struct bch_io_opts io_opts = bch2_opts_to_inode_opts(c->opts);
 712         struct btree_iter iter = {}, bp_iter = {};
 713         struct bkey_buf sk;
 714         struct bkey_s_c k;
 715         struct data_update_opts data_opts;
 716         unsigned sectors_moved = 0;
 717         struct bkey_buf last_flushed;
 718         int ret = 0;
 719
 720         struct bch_dev *ca = bch2_dev_tryget(c, bucket.inode);
 721         if (!ca)
 722                 return 0;
 723
 724         trace_bucket_evacuate(c, &bucket);
 725
 726         bch2_bkey_buf_init(&last_flushed);
 727         bkey_init(&last_flushed.k->k);
 728         bch2_bkey_buf_init(&sk);
 729
 730         /*
 731          * We're not run in a context that handles transaction restarts:
 732          */
 733         bch2_trans_begin(trans);
 734
 735         bch2_trans_iter_init(trans, &bp_iter, BTREE_ID_backpointers,
 736                              bucket_pos_to_bp_start(ca, bucket), 0);
 737
 738         bch_err_msg(c, ret, "looking up alloc key");
 739         if (ret)
 740                 goto err;
 741
 742         ret = bch2_btree_write_buffer_tryflush(trans);
 743         bch_err_msg(c, ret, "flushing btree write buffer");
 744         if (ret)
 745                 goto err;
 746
 747         while (!(ret = bch2_move_ratelimit(ctxt))) {
 748                 if (is_kthread && kthread_should_stop())
 749                         break;
 750
 751                 bch2_trans_begin(trans);
 752
 753                 k = bch2_btree_iter_peek(&bp_iter);
 754                 ret = bkey_err(k);
 755                 if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 756                         continue;
 757                 if (ret)
 758                         goto err;
 759
 760                 if (!k.k || bkey_gt(k.k->p, bucket_pos_to_bp_end(ca, bucket)))
 761                         break;
 762
 763                 if (k.k->type != KEY_TYPE_backpointer)
 764                         goto next;
 765
 766                 struct bkey_s_c_backpointer bp = bkey_s_c_to_backpointer(k);
 767
 768                 if (!bp.v->level) {
 769                         k = bch2_backpointer_get_key(trans, bp, &iter, 0, &last_flushed);
 770                         ret = bkey_err(k);
 771                         if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 772                                 continue;
 773                         if (ret)
 774                                 goto err;
 775                         if (!k.k)
 776                                 goto next;
 777
 778                         bch2_bkey_buf_reassemble(&sk, c, k);
 779                         k = bkey_i_to_s_c(sk.k);
 780
 781                         ret = bch2_move_get_io_opts_one(trans, &io_opts, &iter, k);
 782                         if (ret) {
 783                                 bch2_trans_iter_exit(trans, &iter);
 784                                 continue;
 785                         }
 786
 787                         data_opts = _data_opts;
 788                         data_opts.target        = io_opts.background_target;
 789                         data_opts.rewrite_ptrs = 0;
 790
 791                         unsigned sectors = bp.v->bucket_len; /* move_extent will drop locks */
 792                         unsigned i = 0;
 793                         const union bch_extent_entry *entry;
 794                         struct extent_ptr_decoded p;
 795                         bkey_for_each_ptr_decode(k.k, bch2_bkey_ptrs_c(k), p, entry) {
 796                                 if (p.ptr.dev == bucket.inode) {
 797                                         if (p.ptr.cached) {
 798                                                 bch2_trans_iter_exit(trans, &iter);
 799                                                 goto next;
 800                                         }
 801                                         data_opts.rewrite_ptrs |= 1U << i;
 802                                         break;
 803                                 }
 804                                 i++;
 805                         }
 806
 807                         ret = bch2_move_extent(ctxt, bucket_in_flight,
 808                                                &iter, k, io_opts, data_opts);
 809                         bch2_trans_iter_exit(trans, &iter);
 810
 811                         if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 812                                 continue;
 813                         if (ret == -ENOMEM) {
 814                                 /* memory allocation failure, wait for some IO to finish */
 815                                 bch2_move_ctxt_wait_for_io(ctxt);
 816                                 continue;
 817                         }
 818                         if (ret)
 819                                 goto err;
 820
 821                         if (ctxt->stats)
 822                                 atomic64_add(sectors, &ctxt->stats->sectors_seen);
 823                         sectors_moved += sectors;
 824                 } else {
 825                         struct btree *b;
 826
 827                         b = bch2_backpointer_get_node(trans, bp, &iter, &last_flushed);
 828                         ret = PTR_ERR_OR_ZERO(b);
 829                         if (ret == -BCH_ERR_backpointer_to_overwritten_btree_node)
 830                                 goto next;
 831                         if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 832                                 continue;
 833                         if (ret)
 834                                 goto err;
 835                         if (!b)
 836                                 goto next;
 837
 838                         unsigned sectors = btree_ptr_sectors_written(bkey_i_to_s_c(&b->key));
 839
 840                         ret = bch2_btree_node_rewrite(trans, &iter, b, 0);
 841                         bch2_trans_iter_exit(trans, &iter);
 842
 843                         if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 844                                 continue;
 845                         if (ret)
 846                                 goto err;
 847
 848                         if (ctxt->rate)
 849                                 bch2_ratelimit_increment(ctxt->rate, sectors);
 850                         if (ctxt->stats) {
 851                                 atomic64_add(sectors, &ctxt->stats->sectors_seen);
 852                                 atomic64_add(sectors, &ctxt->stats->sectors_moved);
 853                         }
 854                         sectors_moved += btree_sectors(c);
 855                 }
 856 next:
 857                 bch2_btree_iter_advance(&bp_iter);
 858         }
 859
 860         trace_evacuate_bucket(c, &bucket, sectors_moved, ca->mi.bucket_size, ret);
 861 err:
 862         bch2_trans_iter_exit(trans, &bp_iter);
 863         bch2_dev_put(ca);
 864         bch2_bkey_buf_exit(&sk, c);
 865         bch2_bkey_buf_exit(&last_flushed, c);
 866         return ret;
 867 }
 868
 869 typedef bool (*move_btree_pred)(struct bch_fs *, void *,
 870                                 struct btree *, struct bch_io_opts *,
 871                                 struct data_update_opts *);
 872
 873 static int bch2_move_btree(struct bch_fs *c,
 874                            struct bbpos start,
 875                            struct bbpos end,
 876                            move_btree_pred pred, void *arg,
 877                            struct bch_move_stats *stats)
 878 {
 879         bool kthread = (current->flags & PF_KTHREAD) != 0;
 880         struct bch_io_opts io_opts = bch2_opts_to_inode_opts(c->opts);
 881         struct moving_context ctxt;
 882         struct btree_trans *trans;
 883         struct btree_iter iter;
 884         struct btree *b;
 885         enum btree_id btree;
 886         struct data_update_opts data_opts;
 887         int ret = 0;
 888
 889         bch2_moving_ctxt_init(&ctxt, c, NULL, stats,
 890                               writepoint_ptr(&c->btree_write_point),
 891                               true);
 892         trans = ctxt.trans;
 893
 894         stats->data_type = BCH_DATA_btree;
 895
 896         for (btree = start.btree;
 897              btree <= min_t(unsigned, end.btree, btree_id_nr_alive(c) - 1);
 898              btree ++) {
 899                 stats->pos = BBPOS(btree, POS_MIN);
 900
 901                 if (!bch2_btree_id_root(c, btree)->b)
 902                         continue;
 903
 904                 bch2_trans_node_iter_init(trans, &iter, btree, POS_MIN, 0, 0,
 905                                           BTREE_ITER_prefetch);
 906 retry:
 907                 ret = 0;
 908                 while (bch2_trans_begin(trans),
 909                        (b = bch2_btree_iter_peek_node(&iter)) &&
 910                        !(ret = PTR_ERR_OR_ZERO(b))) {
 911                         if (kthread && kthread_should_stop())
 912                                 break;
 913
 914                         if ((cmp_int(btree, end.btree) ?:
 915                              bpos_cmp(b->key.k.p, end.pos)) > 0)
 916                                 break;
 917
 918                         stats->pos = BBPOS(iter.btree_id, iter.pos);
 919
 920                         if (!pred(c, arg, b, &io_opts, &data_opts))
 921                                 goto next;
 922
 923                         ret = bch2_btree_node_rewrite(trans, &iter, b, 0) ?: ret;
 924                         if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 925                                 continue;
 926                         if (ret)
 927                                 break;
 928 next:
 929                         bch2_btree_iter_next_node(&iter);
 930                 }
 931                 if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 932                         goto retry;
 933
 934                 bch2_trans_iter_exit(trans, &iter);
 935
 936                 if (kthread && kthread_should_stop())
 937                         break;
 938         }
 939
 940         bch_err_fn(c, ret);
 941         bch2_moving_ctxt_exit(&ctxt);
 942         bch2_btree_interior_updates_flush(c);
 943
 944         return ret;
 945 }
 946
 947 static bool rereplicate_pred(struct bch_fs *c, void *arg,
 948                              struct bkey_s_c k,
 949                              struct bch_io_opts *io_opts,
 950                              struct data_update_opts *data_opts)
 951 {
 952         unsigned nr_good = bch2_bkey_durability(c, k);
 953         unsigned replicas = bkey_is_btree_ptr(k.k)
 954                 ? c->opts.metadata_replicas
 955                 : io_opts->data_replicas;
 956
 957         rcu_read_lock();
 958         struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
 959         unsigned i = 0;
 960         bkey_for_each_ptr(ptrs, ptr) {
 961                 struct bch_dev *ca = bch2_dev_rcu(c, ptr->dev);
 962                 if (!ptr->cached &&
 963                     (!ca || !ca->mi.durability))
 964                         data_opts->kill_ptrs |= BIT(i);
 965                 i++;
 966         }
 967         rcu_read_unlock();
 968
 969         if (!data_opts->kill_ptrs &&
 970             (!nr_good || nr_good >= replicas))
 971                 return false;
 972
 973         data_opts->target               = 0;
 974         data_opts->extra_replicas       = replicas - nr_good;
 975         data_opts->btree_insert_flags   = 0;
 976         return true;
 977 }
 978
 979 static bool migrate_pred(struct bch_fs *c, void *arg,
 980                          struct bkey_s_c k,
 981                          struct bch_io_opts *io_opts,
 982                          struct data_update_opts *data_opts)
 983 {
 984         struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
 985         struct bch_ioctl_data *op = arg;
 986         unsigned i = 0;
 987
 988         data_opts->rewrite_ptrs         = 0;
 989         data_opts->target               = 0;
 990         data_opts->extra_replicas       = 0;
 991         data_opts->btree_insert_flags   = 0;
 992
 993         bkey_for_each_ptr(ptrs, ptr) {
 994                 if (ptr->dev == op->migrate.dev)
 995                         data_opts->rewrite_ptrs |= 1U << i;
 996                 i++;
 997         }
 998
 999         return data_opts->rewrite_ptrs != 0;
1000 }
1001
1002 static bool rereplicate_btree_pred(struct bch_fs *c, void *arg,
1003                                    struct btree *b,
1004                                    struct bch_io_opts *io_opts,
1005                                    struct data_update_opts *data_opts)
1006 {
1007         return rereplicate_pred(c, arg, bkey_i_to_s_c(&b->key), io_opts, data_opts);
1008 }
1009
1010 static bool migrate_btree_pred(struct bch_fs *c, void *arg,
1011                                struct btree *b,
1012                                struct bch_io_opts *io_opts,
1013                                struct data_update_opts *data_opts)
1014 {
1015         return migrate_pred(c, arg, bkey_i_to_s_c(&b->key), io_opts, data_opts);
1016 }
1017
1018 /*
1019  * Ancient versions of bcachefs produced packed formats which could represent
1020  * keys that the in memory format cannot represent; this checks for those
1021  * formats so we can get rid of them.
1022  */
1023 static bool bformat_needs_redo(struct bkey_format *f)
1024 {
1025         for (unsigned i = 0; i < f->nr_fields; i++)
1026                 if (bch2_bkey_format_field_overflows(f, i))
1027                         return true;
1028
1029         return false;
1030 }
1031
1032 static bool rewrite_old_nodes_pred(struct bch_fs *c, void *arg,
1033                                    struct btree *b,
1034                                    struct bch_io_opts *io_opts,
1035                                    struct data_update_opts *data_opts)
1036 {
1037         if (b->version_ondisk != c->sb.version ||
1038             btree_node_need_rewrite(b) ||
1039             bformat_needs_redo(&b->format)) {
1040                 data_opts->target               = 0;
1041                 data_opts->extra_replicas       = 0;
1042                 data_opts->btree_insert_flags   = 0;
1043                 return true;
1044         }
1045
1046         return false;
1047 }
1048
1049 int bch2_scan_old_btree_nodes(struct bch_fs *c, struct bch_move_stats *stats)
1050 {
1051         int ret;
1052
1053         ret = bch2_move_btree(c,
1054                               BBPOS_MIN,
1055                               BBPOS_MAX,
1056                               rewrite_old_nodes_pred, c, stats);
1057         if (!ret) {
1058                 mutex_lock(&c->sb_lock);
1059                 c->disk_sb.sb->compat[0] |= cpu_to_le64(1ULL << BCH_COMPAT_extents_above_btree_updates_done);
1060                 c->disk_sb.sb->compat[0] |= cpu_to_le64(1ULL << BCH_COMPAT_bformat_overflow_done);
1061                 c->disk_sb.sb->version_min = c->disk_sb.sb->version;
1062                 bch2_write_super(c);
1063                 mutex_unlock(&c->sb_lock);
1064         }
1065
1066         bch_err_fn(c, ret);
1067         return ret;
1068 }
1069
1070 static bool drop_extra_replicas_pred(struct bch_fs *c, void *arg,
1071                              struct bkey_s_c k,
1072                              struct bch_io_opts *io_opts,
1073                              struct data_update_opts *data_opts)
1074 {
1075         unsigned durability = bch2_bkey_durability(c, k);
1076         unsigned replicas = bkey_is_btree_ptr(k.k)
1077                 ? c->opts.metadata_replicas
1078                 : io_opts->data_replicas;
1079         const union bch_extent_entry *entry;
1080         struct extent_ptr_decoded p;
1081         unsigned i = 0;
1082
1083         rcu_read_lock();
1084         bkey_for_each_ptr_decode(k.k, bch2_bkey_ptrs_c(k), p, entry) {
1085                 unsigned d = bch2_extent_ptr_durability(c, &p);
1086
1087                 if (d && durability - d >= replicas) {
1088                         data_opts->kill_ptrs |= BIT(i);
1089                         durability -= d;
1090                 }
1091
1092                 i++;
1093         }
1094         rcu_read_unlock();
1095
1096         return data_opts->kill_ptrs != 0;
1097 }
1098
1099 static bool drop_extra_replicas_btree_pred(struct bch_fs *c, void *arg,
1100                                    struct btree *b,
1101                                    struct bch_io_opts *io_opts,
1102                                    struct data_update_opts *data_opts)
1103 {
1104         return drop_extra_replicas_pred(c, arg, bkey_i_to_s_c(&b->key), io_opts, data_opts);
1105 }
1106
1107 int bch2_data_job(struct bch_fs *c,
1108                   struct bch_move_stats *stats,
1109                   struct bch_ioctl_data op)
1110 {
1111         struct bbpos start      = BBPOS(op.start_btree, op.start_pos);
1112         struct bbpos end        = BBPOS(op.end_btree, op.end_pos);
1113         int ret = 0;
1114
1115         if (op.op >= BCH_DATA_OP_NR)
1116                 return -EINVAL;
1117
1118         bch2_move_stats_init(stats, bch2_data_ops_strs[op.op]);
1119
1120         switch (op.op) {
1121         case BCH_DATA_OP_rereplicate:
1122                 stats->data_type = BCH_DATA_journal;
1123                 ret = bch2_journal_flush_device_pins(&c->journal, -1);
1124                 ret = bch2_move_btree(c, start, end,
1125                                       rereplicate_btree_pred, c, stats) ?: ret;
1126                 ret = bch2_move_data(c, start, end,
1127                                      NULL,
1128                                      stats,
1129                                      writepoint_hashed((unsigned long) current),
1130                                      true,
1131                                      rereplicate_pred, c) ?: ret;
1132                 ret = bch2_replicas_gc2(c) ?: ret;
1133                 break;
1134         case BCH_DATA_OP_migrate:
1135                 if (op.migrate.dev >= c->sb.nr_devices)
1136                         return -EINVAL;
1137
1138                 stats->data_type = BCH_DATA_journal;
1139                 ret = bch2_journal_flush_device_pins(&c->journal, op.migrate.dev);
1140                 ret = bch2_move_btree(c, start, end,
1141                                       migrate_btree_pred, &op, stats) ?: ret;
1142                 ret = bch2_move_data(c, start, end,
1143                                      NULL,
1144                                      stats,
1145                                      writepoint_hashed((unsigned long) current),
1146                                      true,
1147                                      migrate_pred, &op) ?: ret;
1148                 ret = bch2_replicas_gc2(c) ?: ret;
1149                 break;
1150         case BCH_DATA_OP_rewrite_old_nodes:
1151                 ret = bch2_scan_old_btree_nodes(c, stats);
1152                 break;
1153         case BCH_DATA_OP_drop_extra_replicas:
1154                 ret = bch2_move_btree(c, start, end,
1155                                 drop_extra_replicas_btree_pred, c, stats) ?: ret;
1156                 ret = bch2_move_data(c, start, end, NULL, stats,
1157                                 writepoint_hashed((unsigned long) current),
1158                                 true,
1159                                 drop_extra_replicas_pred, c) ?: ret;
1160                 ret = bch2_replicas_gc2(c) ?: ret;
1161                 break;
1162         default:
1163                 ret = -EINVAL;
1164         }
1165
1166         bch2_move_stats_exit(stats, c);
1167         return ret;
1168 }
1169
1170 void bch2_move_stats_to_text(struct printbuf *out, struct bch_move_stats *stats)
1171 {
1172         prt_printf(out, "%s: data type==", stats->name);
1173         bch2_prt_data_type(out, stats->data_type);
1174         prt_str(out, " pos=");
1175         bch2_bbpos_to_text(out, stats->pos);
1176         prt_newline(out);
1177         printbuf_indent_add(out, 2);
1178
1179         prt_printf(out, "keys moved:  %llu\n",  atomic64_read(&stats->keys_moved));
1180         prt_printf(out, "keys raced:  %llu\n",  atomic64_read(&stats->keys_raced));
1181         prt_printf(out, "bytes seen:  ");
1182         prt_human_readable_u64(out, atomic64_read(&stats->sectors_seen) << 9);
1183         prt_newline(out);
1184
1185         prt_printf(out, "bytes moved: ");
1186         prt_human_readable_u64(out, atomic64_read(&stats->sectors_moved) << 9);
1187         prt_newline(out);
1188
1189         prt_printf(out, "bytes raced: ");
1190         prt_human_readable_u64(out, atomic64_read(&stats->sectors_raced) << 9);
1191         prt_newline(out);
1192
1193         printbuf_indent_sub(out, 2);
1194 }
1195
1196 static void bch2_moving_ctxt_to_text(struct printbuf *out, struct bch_fs *c, struct moving_context *ctxt)
1197 {
1198         struct moving_io *io;
1199
1200         bch2_move_stats_to_text(out, ctxt->stats);
1201         printbuf_indent_add(out, 2);
1202
1203         prt_printf(out, "reads: ios %u/%u sectors %u/%u\n",
1204                    atomic_read(&ctxt->read_ios),
1205                    c->opts.move_ios_in_flight,
1206                    atomic_read(&ctxt->read_sectors),
1207                    c->opts.move_bytes_in_flight >> 9);
1208
1209         prt_printf(out, "writes: ios %u/%u sectors %u/%u\n",
1210                    atomic_read(&ctxt->write_ios),
1211                    c->opts.move_ios_in_flight,
1212                    atomic_read(&ctxt->write_sectors),
1213                    c->opts.move_bytes_in_flight >> 9);
1214
1215         printbuf_indent_add(out, 2);
1216
1217         mutex_lock(&ctxt->lock);
1218         list_for_each_entry(io, &ctxt->ios, io_list)
1219                 bch2_write_op_to_text(out, &io->write.op);
1220         mutex_unlock(&ctxt->lock);
1221
1222         printbuf_indent_sub(out, 4);
1223 }
1224
1225 void bch2_fs_moving_ctxts_to_text(struct printbuf *out, struct bch_fs *c)
1226 {
1227         struct moving_context *ctxt;
1228
1229         mutex_lock(&c->moving_context_lock);
1230         list_for_each_entry(ctxt, &c->moving_context_list, list)
1231                 bch2_moving_ctxt_to_text(out, c, ctxt);
1232         mutex_unlock(&c->moving_context_lock);
1233 }
1234
1235 void bch2_fs_move_init(struct bch_fs *c)
1236 {
1237         INIT_LIST_HEAD(&c->moving_context_list);
1238         mutex_init(&c->moving_context_lock);
1239 }