Pileus Git - ~andy/linux/blob - drivers/md/bcache/writeback.c

   1 /*
   2  * background writeback - scan btree for dirty data and write it to the backing
   3  * device
   4  *
   5  * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
   6  * Copyright 2012 Google, Inc.
   7  */
   8
   9 #include "bcache.h"
  10 #include "btree.h"
  11 #include "debug.h"
  12 #include "writeback.h"
  13
  14 #include <linux/delay.h>
  15 #include <linux/freezer.h>
  16 #include <linux/kthread.h>
  17 #include <trace/events/bcache.h>
  18
  19 /* Rate limiting */
  20
  21 static void __update_writeback_rate(struct cached_dev *dc)
  22 {
  23         struct cache_set *c = dc->disk.c;
  24         uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size;
  25         uint64_t cache_dirty_target =
  26                 div_u64(cache_sectors * dc->writeback_percent, 100);
  27
  28         int64_t target = div64_u64(cache_dirty_target * bdev_sectors(dc->bdev),
  29                                    c->cached_dev_sectors);
  30
  31         /* PD controller */
  32
  33         int change = 0;
  34         int64_t error;
  35         int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);
  36         int64_t derivative = dirty - dc->disk.sectors_dirty_last;
  37
  38         dc->disk.sectors_dirty_last = dirty;
  39
  40         derivative *= dc->writeback_rate_d_term;
  41         derivative = clamp(derivative, -dirty, dirty);
  42
  43         derivative = ewma_add(dc->disk.sectors_dirty_derivative, derivative,
  44                               dc->writeback_rate_d_smooth, 0);
  45
  46         /* Avoid divide by zero */
  47         if (!target)
  48                 goto out;
  49
  50         error = div64_s64((dirty + derivative - target) << 8, target);
  51
  52         change = div_s64((dc->writeback_rate.rate * error) >> 8,
  53                          dc->writeback_rate_p_term_inverse);
  54
  55         /* Don't increase writeback rate if the device isn't keeping up */
  56         if (change > 0 &&
  57             time_after64(local_clock(),
  58                          dc->writeback_rate.next + 10 * NSEC_PER_MSEC))
  59                 change = 0;
  60
  61         dc->writeback_rate.rate =
  62                 clamp_t(int64_t, dc->writeback_rate.rate + change,
  63                         1, NSEC_PER_MSEC);
  64 out:
  65         dc->writeback_rate_derivative = derivative;
  66         dc->writeback_rate_change = change;
  67         dc->writeback_rate_target = target;
  68 }
  69
  70 static void update_writeback_rate(struct work_struct *work)
  71 {
  72         struct cached_dev *dc = container_of(to_delayed_work(work),
  73                                              struct cached_dev,
  74                                              writeback_rate_update);
  75
  76         down_read(&dc->writeback_lock);
  77
  78         if (atomic_read(&dc->has_dirty) &&
  79             dc->writeback_percent)
  80                 __update_writeback_rate(dc);
  81
  82         up_read(&dc->writeback_lock);
  83
  84         schedule_delayed_work(&dc->writeback_rate_update,
  85                               dc->writeback_rate_update_seconds * HZ);
  86 }
  87
  88 static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors)
  89 {
  90         uint64_t ret;
  91
  92         if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
  93             !dc->writeback_percent)
  94                 return 0;
  95
  96         ret = bch_next_delay(&dc->writeback_rate, sectors * 10000000ULL);
  97
  98         return min_t(uint64_t, ret, HZ);
  99 }
 100
 101 struct dirty_io {
 102         struct closure          cl;
 103         struct cached_dev       *dc;
 104         struct bio              bio;
 105 };
 106
 107 static void dirty_init(struct keybuf_key *w)
 108 {
 109         struct dirty_io *io = w->private;
 110         struct bio *bio = &io->bio;
 111
 112         bio_init(bio);
 113         if (!io->dc->writeback_percent)
 114                 bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
 115
 116         bio->bi_size            = KEY_SIZE(&w->key) << 9;
 117         bio->bi_max_vecs        = DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS);
 118         bio->bi_private         = w;
 119         bio->bi_io_vec          = bio->bi_inline_vecs;
 120         bch_bio_map(bio, NULL);
 121 }
 122
 123 static void dirty_io_destructor(struct closure *cl)
 124 {
 125         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 126         kfree(io);
 127 }
 128
 129 static void write_dirty_finish(struct closure *cl)
 130 {
 131         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 132         struct keybuf_key *w = io->bio.bi_private;
 133         struct cached_dev *dc = io->dc;
 134         struct bio_vec *bv;
 135         int i;
 136
 137         bio_for_each_segment_all(bv, &io->bio, i)
 138                 __free_page(bv->bv_page);
 139
 140         /* This is kind of a dumb way of signalling errors. */
 141         if (KEY_DIRTY(&w->key)) {
 142                 int ret;
 143                 unsigned i;
 144                 struct keylist keys;
 145
 146                 bch_keylist_init(&keys);
 147
 148                 bkey_copy(keys.top, &w->key);
 149                 SET_KEY_DIRTY(keys.top, false);
 150                 bch_keylist_push(&keys);
 151
 152                 for (i = 0; i < KEY_PTRS(&w->key); i++)
 153                         atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
 154
 155                 ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);
 156
 157                 if (ret)
 158                         trace_bcache_writeback_collision(&w->key);
 159
 160                 atomic_long_inc(ret
 161                                 ? &dc->disk.c->writeback_keys_failed
 162                                 : &dc->disk.c->writeback_keys_done);
 163         }
 164
 165         bch_keybuf_del(&dc->writeback_keys, w);
 166         up(&dc->in_flight);
 167
 168         closure_return_with_destructor(cl, dirty_io_destructor);
 169 }
 170
 171 static void dirty_endio(struct bio *bio, int error)
 172 {
 173         struct keybuf_key *w = bio->bi_private;
 174         struct dirty_io *io = w->private;
 175
 176         if (error)
 177                 SET_KEY_DIRTY(&w->key, false);
 178
 179         closure_put(&io->cl);
 180 }
 181
 182 static void write_dirty(struct closure *cl)
 183 {
 184         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 185         struct keybuf_key *w = io->bio.bi_private;
 186
 187         dirty_init(w);
 188         io->bio.bi_rw           = WRITE;
 189         io->bio.bi_sector       = KEY_START(&w->key);
 190         io->bio.bi_bdev         = io->dc->bdev;
 191         io->bio.bi_end_io       = dirty_endio;
 192
 193         closure_bio_submit(&io->bio, cl, &io->dc->disk);
 194
 195         continue_at(cl, write_dirty_finish, system_wq);
 196 }
 197
 198 static void read_dirty_endio(struct bio *bio, int error)
 199 {
 200         struct keybuf_key *w = bio->bi_private;
 201         struct dirty_io *io = w->private;
 202
 203         bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0),
 204                             error, "reading dirty data from cache");
 205
 206         dirty_endio(bio, error);
 207 }
 208
 209 static void read_dirty_submit(struct closure *cl)
 210 {
 211         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 212
 213         closure_bio_submit(&io->bio, cl, &io->dc->disk);
 214
 215         continue_at(cl, write_dirty, system_wq);
 216 }
 217
 218 static void read_dirty(struct cached_dev *dc)
 219 {
 220         unsigned delay = 0;
 221         struct keybuf_key *w;
 222         struct dirty_io *io;
 223         struct closure cl;
 224
 225         closure_init_stack(&cl);
 226
 227         /*
 228          * XXX: if we error, background writeback just spins. Should use some
 229          * mempools.
 230          */
 231
 232         while (!kthread_should_stop()) {
 233                 try_to_freeze();
 234
 235                 w = bch_keybuf_next(&dc->writeback_keys);
 236                 if (!w)
 237                         break;
 238
 239                 BUG_ON(ptr_stale(dc->disk.c, &w->key, 0));
 240
 241                 if (KEY_START(&w->key) != dc->last_read ||
 242                     jiffies_to_msecs(delay) > 50)
 243                         while (!kthread_should_stop() && delay)
 244                                 delay = schedule_timeout_interruptible(delay);
 245
 246                 dc->last_read   = KEY_OFFSET(&w->key);
 247
 248                 io = kzalloc(sizeof(struct dirty_io) + sizeof(struct bio_vec)
 249                              * DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),
 250                              GFP_KERNEL);
 251                 if (!io)
 252                         goto err;
 253
 254                 w->private      = io;
 255                 io->dc          = dc;
 256
 257                 dirty_init(w);
 258                 io->bio.bi_sector       = PTR_OFFSET(&w->key, 0);
 259                 io->bio.bi_bdev         = PTR_CACHE(dc->disk.c,
 260                                                     &w->key, 0)->bdev;
 261                 io->bio.bi_rw           = READ;
 262                 io->bio.bi_end_io       = read_dirty_endio;
 263
 264                 if (bio_alloc_pages(&io->bio, GFP_KERNEL))
 265                         goto err_free;
 266
 267                 trace_bcache_writeback(&w->key);
 268
 269                 down(&dc->in_flight);
 270                 closure_call(&io->cl, read_dirty_submit, NULL, &cl);
 271
 272                 delay = writeback_delay(dc, KEY_SIZE(&w->key));
 273         }
 274
 275         if (0) {
 276 err_free:
 277                 kfree(w->private);
 278 err:
 279                 bch_keybuf_del(&dc->writeback_keys, w);
 280         }
 281
 282         /*
 283          * Wait for outstanding writeback IOs to finish (and keybuf slots to be
 284          * freed) before refilling again
 285          */
 286         closure_sync(&cl);
 287 }
 288
 289 /* Scan for dirty data */
 290
 291 void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode,
 292                                   uint64_t offset, int nr_sectors)
 293 {
 294         struct bcache_device *d = c->devices[inode];
 295         unsigned stripe_offset, stripe, sectors_dirty;
 296
 297         if (!d)
 298                 return;
 299
 300         stripe = offset_to_stripe(d, offset);
 301         stripe_offset = offset & (d->stripe_size - 1);
 302
 303         while (nr_sectors) {
 304                 int s = min_t(unsigned, abs(nr_sectors),
 305                               d->stripe_size - stripe_offset);
 306
 307                 if (nr_sectors < 0)
 308                         s = -s;
 309
 310                 if (stripe >= d->nr_stripes)
 311                         return;
 312
 313                 sectors_dirty = atomic_add_return(s,
 314                                         d->stripe_sectors_dirty + stripe);
 315                 if (sectors_dirty == d->stripe_size)
 316                         set_bit(stripe, d->full_dirty_stripes);
 317                 else
 318                         clear_bit(stripe, d->full_dirty_stripes);
 319
 320                 nr_sectors -= s;
 321                 stripe_offset = 0;
 322                 stripe++;
 323         }
 324 }
 325
 326 static bool dirty_pred(struct keybuf *buf, struct bkey *k)
 327 {
 328         return KEY_DIRTY(k);
 329 }
 330
 331 static void refill_full_stripes(struct cached_dev *dc)
 332 {
 333         struct keybuf *buf = &dc->writeback_keys;
 334         unsigned start_stripe, stripe, next_stripe;
 335         bool wrapped = false;
 336
 337         stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));
 338
 339         if (stripe >= dc->disk.nr_stripes)
 340                 stripe = 0;
 341
 342         start_stripe = stripe;
 343
 344         while (1) {
 345                 stripe = find_next_bit(dc->disk.full_dirty_stripes,
 346                                        dc->disk.nr_stripes, stripe);
 347
 348                 if (stripe == dc->disk.nr_stripes)
 349                         goto next;
 350
 351                 next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes,
 352                                                  dc->disk.nr_stripes, stripe);
 353
 354                 buf->last_scanned = KEY(dc->disk.id,
 355                                         stripe * dc->disk.stripe_size, 0);
 356
 357                 bch_refill_keybuf(dc->disk.c, buf,
 358                                   &KEY(dc->disk.id,
 359                                        next_stripe * dc->disk.stripe_size, 0),
 360                                   dirty_pred);
 361
 362                 if (array_freelist_empty(&buf->freelist))
 363                         return;
 364
 365                 stripe = next_stripe;
 366 next:
 367                 if (wrapped && stripe > start_stripe)
 368                         return;
 369
 370                 if (stripe == dc->disk.nr_stripes) {
 371                         stripe = 0;
 372                         wrapped = true;
 373                 }
 374         }
 375 }
 376
 377 static bool refill_dirty(struct cached_dev *dc)
 378 {
 379         struct keybuf *buf = &dc->writeback_keys;
 380         struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
 381         bool searched_from_start = false;
 382
 383         if (dc->partial_stripes_expensive) {
 384                 refill_full_stripes(dc);
 385                 if (array_freelist_empty(&buf->freelist))
 386                         return false;
 387         }
 388
 389         if (bkey_cmp(&buf->last_scanned, &end) >= 0) {
 390                 buf->last_scanned = KEY(dc->disk.id, 0, 0);
 391                 searched_from_start = true;
 392         }
 393
 394         bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
 395
 396         return bkey_cmp(&buf->last_scanned, &end) >= 0 && searched_from_start;
 397 }
 398
 399 static int bch_writeback_thread(void *arg)
 400 {
 401         struct cached_dev *dc = arg;
 402         bool searched_full_index;
 403
 404         while (!kthread_should_stop()) {
 405                 down_write(&dc->writeback_lock);
 406                 if (!atomic_read(&dc->has_dirty) ||
 407                     (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
 408                      !dc->writeback_running)) {
 409                         up_write(&dc->writeback_lock);
 410                         set_current_state(TASK_INTERRUPTIBLE);
 411
 412                         if (kthread_should_stop())
 413                                 return 0;
 414
 415                         try_to_freeze();
 416                         schedule();
 417                         continue;
 418                 }
 419
 420                 searched_full_index = refill_dirty(dc);
 421
 422                 if (searched_full_index &&
 423                     RB_EMPTY_ROOT(&dc->writeback_keys.keys)) {
 424                         atomic_set(&dc->has_dirty, 0);
 425                         cached_dev_put(dc);
 426                         SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
 427                         bch_write_bdev_super(dc, NULL);
 428                 }
 429
 430                 up_write(&dc->writeback_lock);
 431
 432                 bch_ratelimit_reset(&dc->writeback_rate);
 433                 read_dirty(dc);
 434
 435                 if (searched_full_index) {
 436                         unsigned delay = dc->writeback_delay * HZ;
 437
 438                         while (delay &&
 439                                !kthread_should_stop() &&
 440                                !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
 441                                 delay = schedule_timeout_interruptible(delay);
 442                 }
 443         }
 444
 445         return 0;
 446 }
 447
 448 /* Init */
 449
 450 struct sectors_dirty_init {
 451         struct btree_op op;
 452         unsigned        inode;
 453 };
 454
 455 static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
 456                                  struct bkey *k)
 457 {
 458         struct sectors_dirty_init *op = container_of(_op,
 459                                                 struct sectors_dirty_init, op);
 460         if (KEY_INODE(k) > op->inode)
 461                 return MAP_DONE;
 462
 463         if (KEY_DIRTY(k))
 464                 bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
 465                                              KEY_START(k), KEY_SIZE(k));
 466
 467         return MAP_CONTINUE;
 468 }
 469
 470 void bch_sectors_dirty_init(struct cached_dev *dc)
 471 {
 472         struct sectors_dirty_init op;
 473
 474         bch_btree_op_init(&op.op, -1);
 475         op.inode = dc->disk.id;
 476
 477         bch_btree_map_keys(&op.op, dc->disk.c, &KEY(op.inode, 0, 0),
 478                            sectors_dirty_init_fn, 0);
 479 }
 480
 481 int bch_cached_dev_writeback_init(struct cached_dev *dc)
 482 {
 483         sema_init(&dc->in_flight, 64);
 484         init_rwsem(&dc->writeback_lock);
 485         bch_keybuf_init(&dc->writeback_keys);
 486
 487         dc->writeback_metadata          = true;
 488         dc->writeback_running           = true;
 489         dc->writeback_percent           = 10;
 490         dc->writeback_delay             = 30;
 491         dc->writeback_rate.rate         = 1024;
 492
 493         dc->writeback_rate_update_seconds = 30;
 494         dc->writeback_rate_d_term       = 16;
 495         dc->writeback_rate_p_term_inverse = 64;
 496         dc->writeback_rate_d_smooth     = 8;
 497
 498         dc->writeback_thread = kthread_create(bch_writeback_thread, dc,
 499                                               "bcache_writeback");
 500         if (IS_ERR(dc->writeback_thread))
 501                 return PTR_ERR(dc->writeback_thread);
 502
 503         set_task_state(dc->writeback_thread, TASK_INTERRUPTIBLE);
 504
 505         INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
 506         schedule_delayed_work(&dc->writeback_rate_update,
 507                               dc->writeback_rate_update_seconds * HZ);
 508
 509         return 0;
 510 }