kernel/fs/btrfs/reada.c

   1 /*
   2  * Copyright (C) 2011 STRATO.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/sched.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/writeback.h>
  22 #include <linux/blkdev.h>
  23 #include <linux/rbtree.h>
  24 #include <linux/slab.h>
  25 #include <linux/workqueue.h>
  26 #include "ctree.h"
  27 #include "volumes.h"
  28 #include "disk-io.h"
  29 #include "transaction.h"
  30 #include "dev-replace.h"
  31
  32 #undef DEBUG
  33
  34 /*
  35  * This is the implementation for the generic read ahead framework.
  36  *
  37  * To trigger a readahead, btrfs_reada_add must be called. It will start
  38  * a read ahead for the given range [start, end) on tree root. The returned
  39  * handle can either be used to wait on the readahead to finish
  40  * (btrfs_reada_wait), or to send it to the background (btrfs_reada_detach).
  41  *
  42  * The read ahead works as follows:
  43  * On btrfs_reada_add, the root of the tree is inserted into a radix_tree.
  44  * reada_start_machine will then search for extents to prefetch and trigger
  45  * some reads. When a read finishes for a node, all contained node/leaf
  46  * pointers that lie in the given range will also be enqueued. The reads will
  47  * be triggered in sequential order, thus giving a big win over a naive
  48  * enumeration. It will also make use of multi-device layouts. Each disk
  49  * will have its on read pointer and all disks will by utilized in parallel.
  50  * Also will no two disks read both sides of a mirror simultaneously, as this
  51  * would waste seeking capacity. Instead both disks will read different parts
  52  * of the filesystem.
  53  * Any number of readaheads can be started in parallel. The read order will be
  54  * determined globally, i.e. 2 parallel readaheads will normally finish faster
  55  * than the 2 started one after another.
  56  */
  57
  58 #define MAX_IN_FLIGHT 6
  59
  60 struct reada_extctl {
  61         struct list_head        list;
  62         struct reada_control    *rc;
  63         u64                     generation;
  64 };
  65
  66 struct reada_extent {
  67         u64                     logical;
  68         struct btrfs_key        top;
  69         int                     err;
  70         struct list_head        extctl;
  71         int                     refcnt;
  72         spinlock_t              lock;
  73         struct reada_zone       *zones[BTRFS_MAX_MIRRORS];
  74         int                     nzones;
  75         struct btrfs_device     *scheduled_for;
  76 };
  77
  78 struct reada_zone {
  79         u64                     start;
  80         u64                     end;
  81         u64                     elems;
  82         struct list_head        list;
  83         spinlock_t              lock;
  84         int                     locked;
  85         struct btrfs_device     *device;
  86         struct btrfs_device     *devs[BTRFS_MAX_MIRRORS]; /* full list, incl
  87                                                            * self */
  88         int                     ndevs;
  89         struct kref             refcnt;
  90 };
  91
  92 struct reada_machine_work {
  93         struct btrfs_work       work;
  94         struct btrfs_fs_info    *fs_info;
  95 };
  96
  97 static void reada_extent_put(struct btrfs_fs_info *, struct reada_extent *);
  98 static void reada_control_release(struct kref *kref);
  99 static void reada_zone_release(struct kref *kref);
 100 static void reada_start_machine(struct btrfs_fs_info *fs_info);
 101 static void __reada_start_machine(struct btrfs_fs_info *fs_info);
 102
 103 static int reada_add_block(struct reada_control *rc, u64 logical,
 104                            struct btrfs_key *top, int level, u64 generation);
 105
 106 /* recurses */
 107 /* in case of err, eb might be NULL */
 108 static int __readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
 109                             u64 start, int err)
 110 {
 111         int level = 0;
 112         int nritems;
 113         int i;
 114         u64 bytenr;
 115         u64 generation;
 116         struct reada_extent *re;
 117         struct btrfs_fs_info *fs_info = root->fs_info;
 118         struct list_head list;
 119         unsigned long index = start >> PAGE_CACHE_SHIFT;
 120         struct btrfs_device *for_dev;
 121
 122         if (eb)
 123                 level = btrfs_header_level(eb);
 124
 125         /* find extent */
 126         spin_lock(&fs_info->reada_lock);
 127         re = radix_tree_lookup(&fs_info->reada_tree, index);
 128         if (re)
 129                 re->refcnt++;
 130         spin_unlock(&fs_info->reada_lock);
 131
 132         if (!re)
 133                 return -1;
 134
 135         spin_lock(&re->lock);
 136         /*
 137          * just take the full list from the extent. afterwards we
 138          * don't need the lock anymore
 139          */
 140         list_replace_init(&re->extctl, &list);
 141         for_dev = re->scheduled_for;
 142         re->scheduled_for = NULL;
 143         spin_unlock(&re->lock);
 144
 145         if (err == 0) {
 146                 nritems = level ? btrfs_header_nritems(eb) : 0;
 147                 generation = btrfs_header_generation(eb);
 148                 /*
 149                  * FIXME: currently we just set nritems to 0 if this is a leaf,
 150                  * effectively ignoring the content. In a next step we could
 151                  * trigger more readahead depending from the content, e.g.
 152                  * fetch the checksums for the extents in the leaf.
 153                  */
 154         } else {
 155                 /*
 156                  * this is the error case, the extent buffer has not been
 157                  * read correctly. We won't access anything from it and
 158                  * just cleanup our data structures. Effectively this will
 159                  * cut the branch below this node from read ahead.
 160                  */
 161                 nritems = 0;
 162                 generation = 0;
 163         }
 164
 165         for (i = 0; i < nritems; i++) {
 166                 struct reada_extctl *rec;
 167                 u64 n_gen;
 168                 struct btrfs_key key;
 169                 struct btrfs_key next_key;
 170
 171                 btrfs_node_key_to_cpu(eb, &key, i);
 172                 if (i + 1 < nritems)
 173                         btrfs_node_key_to_cpu(eb, &next_key, i + 1);
 174                 else
 175                         next_key = re->top;
 176                 bytenr = btrfs_node_blockptr(eb, i);
 177                 n_gen = btrfs_node_ptr_generation(eb, i);
 178
 179                 list_for_each_entry(rec, &list, list) {
 180                         struct reada_control *rc = rec->rc;
 181
 182                         /*
 183                          * if the generation doesn't match, just ignore this
 184                          * extctl. This will probably cut off a branch from
 185                          * prefetch. Alternatively one could start a new (sub-)
 186                          * prefetch for this branch, starting again from root.
 187                          * FIXME: move the generation check out of this loop
 188                          */
 189 #ifdef DEBUG
 190                         if (rec->generation != generation) {
 191                                 btrfs_debug(root->fs_info,
 192                                            "generation mismatch for (%llu,%d,%llu) %llu != %llu",
 193                                        key.objectid, key.type, key.offset,
 194                                        rec->generation, generation);
 195                         }
 196 #endif
 197                         if (rec->generation == generation &&
 198                             btrfs_comp_cpu_keys(&key, &rc->key_end) < 0 &&
 199                             btrfs_comp_cpu_keys(&next_key, &rc->key_start) > 0)
 200                                 reada_add_block(rc, bytenr, &next_key,
 201                                                 level - 1, n_gen);
 202                 }
 203         }
 204         /*
 205          * free extctl records
 206          */
 207         while (!list_empty(&list)) {
 208                 struct reada_control *rc;
 209                 struct reada_extctl *rec;
 210
 211                 rec = list_first_entry(&list, struct reada_extctl, list);
 212                 list_del(&rec->list);
 213                 rc = rec->rc;
 214                 kfree(rec);
 215
 216                 kref_get(&rc->refcnt);
 217                 if (atomic_dec_and_test(&rc->elems)) {
 218                         kref_put(&rc->refcnt, reada_control_release);
 219                         wake_up(&rc->wait);
 220                 }
 221                 kref_put(&rc->refcnt, reada_control_release);
 222
 223                 reada_extent_put(fs_info, re);  /* one ref for each entry */
 224         }
 225         reada_extent_put(fs_info, re);  /* our ref */
 226         if (for_dev)
 227                 atomic_dec(&for_dev->reada_in_flight);
 228
 229         return 0;
 230 }
 231
 232 /*
 233  * start is passed separately in case eb in NULL, which may be the case with
 234  * failed I/O
 235  */
 236 int btree_readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
 237                          u64 start, int err)
 238 {
 239         int ret;
 240
 241         ret = __readahead_hook(root, eb, start, err);
 242
 243         reada_start_machine(root->fs_info);
 244
 245         return ret;
 246 }
 247
 248 static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
 249                                           struct btrfs_device *dev, u64 logical,
 250                                           struct btrfs_bio *bbio)
 251 {
 252         int ret;
 253         struct reada_zone *zone;
 254         struct btrfs_block_group_cache *cache = NULL;
 255         u64 start;
 256         u64 end;
 257         int i;
 258
 259         zone = NULL;
 260         spin_lock(&fs_info->reada_lock);
 261         ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
 262                                      logical >> PAGE_CACHE_SHIFT, 1);
 263         if (ret == 1)
 264                 kref_get(&zone->refcnt);
 265         spin_unlock(&fs_info->reada_lock);
 266
 267         if (ret == 1) {
 268                 if (logical >= zone->start && logical < zone->end)
 269                         return zone;
 270                 spin_lock(&fs_info->reada_lock);
 271                 kref_put(&zone->refcnt, reada_zone_release);
 272                 spin_unlock(&fs_info->reada_lock);
 273         }
 274
 275         cache = btrfs_lookup_block_group(fs_info, logical);
 276         if (!cache)
 277                 return NULL;
 278
 279         start = cache->key.objectid;
 280         end = start + cache->key.offset - 1;
 281         btrfs_put_block_group(cache);
 282
 283         zone = kzalloc(sizeof(*zone), GFP_NOFS);
 284         if (!zone)
 285                 return NULL;
 286
 287         zone->start = start;
 288         zone->end = end;
 289         INIT_LIST_HEAD(&zone->list);
 290         spin_lock_init(&zone->lock);
 291         zone->locked = 0;
 292         kref_init(&zone->refcnt);
 293         zone->elems = 0;
 294         zone->device = dev; /* our device always sits at index 0 */
 295         for (i = 0; i < bbio->num_stripes; ++i) {
 296                 /* bounds have already been checked */
 297                 zone->devs[i] = bbio->stripes[i].dev;
 298         }
 299         zone->ndevs = bbio->num_stripes;
 300
 301         spin_lock(&fs_info->reada_lock);
 302         ret = radix_tree_insert(&dev->reada_zones,
 303                                 (unsigned long)(zone->end >> PAGE_CACHE_SHIFT),
 304                                 zone);
 305
 306         if (ret == -EEXIST) {
 307                 kfree(zone);
 308                 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
 309                                              logical >> PAGE_CACHE_SHIFT, 1);
 310                 if (ret == 1)
 311                         kref_get(&zone->refcnt);
 312         }
 313         spin_unlock(&fs_info->reada_lock);
 314
 315         return zone;
 316 }
 317
 318 static struct reada_extent *reada_find_extent(struct btrfs_root *root,
 319                                               u64 logical,
 320                                               struct btrfs_key *top, int level)
 321 {
 322         int ret;
 323         struct reada_extent *re = NULL;
 324         struct reada_extent *re_exist = NULL;
 325         struct btrfs_fs_info *fs_info = root->fs_info;
 326         struct btrfs_bio *bbio = NULL;
 327         struct btrfs_device *dev;
 328         struct btrfs_device *prev_dev;
 329         u32 blocksize;
 330         u64 length;
 331         int nzones = 0;
 332         int i;
 333         unsigned long index = logical >> PAGE_CACHE_SHIFT;
 334         int dev_replace_is_ongoing;
 335
 336         spin_lock(&fs_info->reada_lock);
 337         re = radix_tree_lookup(&fs_info->reada_tree, index);
 338         if (re)
 339                 re->refcnt++;
 340         spin_unlock(&fs_info->reada_lock);
 341
 342         if (re)
 343                 return re;
 344
 345         re = kzalloc(sizeof(*re), GFP_NOFS);
 346         if (!re)
 347                 return NULL;
 348
 349         blocksize = root->nodesize;
 350         re->logical = logical;
 351         re->top = *top;
 352         INIT_LIST_HEAD(&re->extctl);
 353         spin_lock_init(&re->lock);
 354         re->refcnt = 1;
 355
 356         /*
 357          * map block
 358          */
 359         length = blocksize;
 360         ret = btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS, logical, &length,
 361                               &bbio, 0);
 362         if (ret || !bbio || length < blocksize)
 363                 goto error;
 364
 365         if (bbio->num_stripes > BTRFS_MAX_MIRRORS) {
 366                 btrfs_err(root->fs_info,
 367                            "readahead: more than %d copies not supported",
 368                            BTRFS_MAX_MIRRORS);
 369                 goto error;
 370         }
 371
 372         for (nzones = 0; nzones < bbio->num_stripes; ++nzones) {
 373                 struct reada_zone *zone;
 374
 375                 dev = bbio->stripes[nzones].dev;
 376                 zone = reada_find_zone(fs_info, dev, logical, bbio);
 377                 if (!zone)
 378                         break;
 379
 380                 re->zones[nzones] = zone;
 381                 spin_lock(&zone->lock);
 382                 if (!zone->elems)
 383                         kref_get(&zone->refcnt);
 384                 ++zone->elems;
 385                 spin_unlock(&zone->lock);
 386                 spin_lock(&fs_info->reada_lock);
 387                 kref_put(&zone->refcnt, reada_zone_release);
 388                 spin_unlock(&fs_info->reada_lock);
 389         }
 390         re->nzones = nzones;
 391         if (nzones == 0) {
 392                 /* not a single zone found, error and out */
 393                 goto error;
 394         }
 395
 396         /* insert extent in reada_tree + all per-device trees, all or nothing */
 397         btrfs_dev_replace_lock(&fs_info->dev_replace);
 398         spin_lock(&fs_info->reada_lock);
 399         ret = radix_tree_insert(&fs_info->reada_tree, index, re);
 400         if (ret == -EEXIST) {
 401                 re_exist = radix_tree_lookup(&fs_info->reada_tree, index);
 402                 BUG_ON(!re_exist);
 403                 re_exist->refcnt++;
 404                 spin_unlock(&fs_info->reada_lock);
 405                 btrfs_dev_replace_unlock(&fs_info->dev_replace);
 406                 goto error;
 407         }
 408         if (ret) {
 409                 spin_unlock(&fs_info->reada_lock);
 410                 btrfs_dev_replace_unlock(&fs_info->dev_replace);
 411                 goto error;
 412         }
 413         prev_dev = NULL;
 414         dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(
 415                         &fs_info->dev_replace);
 416         for (i = 0; i < nzones; ++i) {
 417                 dev = bbio->stripes[i].dev;
 418                 if (dev == prev_dev) {
 419                         /*
 420                          * in case of DUP, just add the first zone. As both
 421                          * are on the same device, there's nothing to gain
 422                          * from adding both.
 423                          * Also, it wouldn't work, as the tree is per device
 424                          * and adding would fail with EEXIST
 425                          */
 426                         continue;
 427                 }
 428                 if (!dev->bdev) {
 429                         /*
 430                          * cannot read ahead on missing device, but for RAID5/6,
 431                          * REQ_GET_READ_MIRRORS return 1. So don't skip missing
 432                          * device for such case.
 433                          */
 434                         if (nzones > 1)
 435                                 continue;
 436                 }
 437                 if (dev_replace_is_ongoing &&
 438                     dev == fs_info->dev_replace.tgtdev) {
 439                         /*
 440                          * as this device is selected for reading only as
 441                          * a last resort, skip it for read ahead.
 442                          */
 443                         continue;
 444                 }
 445                 prev_dev = dev;
 446                 ret = radix_tree_insert(&dev->reada_extents, index, re);
 447                 if (ret) {
 448                         while (--i >= 0) {
 449                                 dev = bbio->stripes[i].dev;
 450                                 BUG_ON(dev == NULL);
 451                                 /* ignore whether the entry was inserted */
 452                                 radix_tree_delete(&dev->reada_extents, index);
 453                         }
 454                         BUG_ON(fs_info == NULL);
 455                         radix_tree_delete(&fs_info->reada_tree, index);
 456                         spin_unlock(&fs_info->reada_lock);
 457                         btrfs_dev_replace_unlock(&fs_info->dev_replace);
 458                         goto error;
 459                 }
 460         }
 461         spin_unlock(&fs_info->reada_lock);
 462         btrfs_dev_replace_unlock(&fs_info->dev_replace);
 463
 464         btrfs_put_bbio(bbio);
 465         return re;
 466
 467 error:
 468         while (nzones) {
 469                 struct reada_zone *zone;
 470
 471                 --nzones;
 472                 zone = re->zones[nzones];
 473                 kref_get(&zone->refcnt);
 474                 spin_lock(&zone->lock);
 475                 --zone->elems;
 476                 if (zone->elems == 0) {
 477                         /*
 478                          * no fs_info->reada_lock needed, as this can't be
 479                          * the last ref
 480                          */
 481                         kref_put(&zone->refcnt, reada_zone_release);
 482                 }
 483                 spin_unlock(&zone->lock);
 484
 485                 spin_lock(&fs_info->reada_lock);
 486                 kref_put(&zone->refcnt, reada_zone_release);
 487                 spin_unlock(&fs_info->reada_lock);
 488         }
 489         btrfs_put_bbio(bbio);
 490         kfree(re);
 491         return re_exist;
 492 }
 493
 494 static void reada_extent_put(struct btrfs_fs_info *fs_info,
 495                              struct reada_extent *re)
 496 {
 497         int i;
 498         unsigned long index = re->logical >> PAGE_CACHE_SHIFT;
 499
 500         spin_lock(&fs_info->reada_lock);
 501         if (--re->refcnt) {
 502                 spin_unlock(&fs_info->reada_lock);
 503                 return;
 504         }
 505
 506         radix_tree_delete(&fs_info->reada_tree, index);
 507         for (i = 0; i < re->nzones; ++i) {
 508                 struct reada_zone *zone = re->zones[i];
 509
 510                 radix_tree_delete(&zone->device->reada_extents, index);
 511         }
 512
 513         spin_unlock(&fs_info->reada_lock);
 514
 515         for (i = 0; i < re->nzones; ++i) {
 516                 struct reada_zone *zone = re->zones[i];
 517
 518                 kref_get(&zone->refcnt);
 519                 spin_lock(&zone->lock);
 520                 --zone->elems;
 521                 if (zone->elems == 0) {
 522                         /* no fs_info->reada_lock needed, as this can't be
 523                          * the last ref */
 524                         kref_put(&zone->refcnt, reada_zone_release);
 525                 }
 526                 spin_unlock(&zone->lock);
 527
 528                 spin_lock(&fs_info->reada_lock);
 529                 kref_put(&zone->refcnt, reada_zone_release);
 530                 spin_unlock(&fs_info->reada_lock);
 531         }
 532         if (re->scheduled_for)
 533                 atomic_dec(&re->scheduled_for->reada_in_flight);
 534
 535         kfree(re);
 536 }
 537
 538 static void reada_zone_release(struct kref *kref)
 539 {
 540         struct reada_zone *zone = container_of(kref, struct reada_zone, refcnt);
 541
 542         radix_tree_delete(&zone->device->reada_zones,
 543                           zone->end >> PAGE_CACHE_SHIFT);
 544
 545         kfree(zone);
 546 }
 547
 548 static void reada_control_release(struct kref *kref)
 549 {
 550         struct reada_control *rc = container_of(kref, struct reada_control,
 551                                                 refcnt);
 552
 553         kfree(rc);
 554 }
 555
 556 static int reada_add_block(struct reada_control *rc, u64 logical,
 557                            struct btrfs_key *top, int level, u64 generation)
 558 {
 559         struct btrfs_root *root = rc->root;
 560         struct reada_extent *re;
 561         struct reada_extctl *rec;
 562
 563         re = reada_find_extent(root, logical, top, level); /* takes one ref */
 564         if (!re)
 565                 return -1;
 566
 567         rec = kzalloc(sizeof(*rec), GFP_NOFS);
 568         if (!rec) {
 569                 reada_extent_put(root->fs_info, re);
 570                 return -1;
 571         }
 572
 573         rec->rc = rc;
 574         rec->generation = generation;
 575         atomic_inc(&rc->elems);
 576
 577         spin_lock(&re->lock);
 578         list_add_tail(&rec->list, &re->extctl);
 579         spin_unlock(&re->lock);
 580
 581         /* leave the ref on the extent */
 582
 583         return 0;
 584 }
 585
 586 /*
 587  * called with fs_info->reada_lock held
 588  */
 589 static void reada_peer_zones_set_lock(struct reada_zone *zone, int lock)
 590 {
 591         int i;
 592         unsigned long index = zone->end >> PAGE_CACHE_SHIFT;
 593
 594         for (i = 0; i < zone->ndevs; ++i) {
 595                 struct reada_zone *peer;
 596                 peer = radix_tree_lookup(&zone->devs[i]->reada_zones, index);
 597                 if (peer && peer->device != zone->device)
 598                         peer->locked = lock;
 599         }
 600 }
 601
 602 /*
 603  * called with fs_info->reada_lock held
 604  */
 605 static int reada_pick_zone(struct btrfs_device *dev)
 606 {
 607         struct reada_zone *top_zone = NULL;
 608         struct reada_zone *top_locked_zone = NULL;
 609         u64 top_elems = 0;
 610         u64 top_locked_elems = 0;
 611         unsigned long index = 0;
 612         int ret;
 613
 614         if (dev->reada_curr_zone) {
 615                 reada_peer_zones_set_lock(dev->reada_curr_zone, 0);
 616                 kref_put(&dev->reada_curr_zone->refcnt, reada_zone_release);
 617                 dev->reada_curr_zone = NULL;
 618         }
 619         /* pick the zone with the most elements */
 620         while (1) {
 621                 struct reada_zone *zone;
 622
 623                 ret = radix_tree_gang_lookup(&dev->reada_zones,
 624                                              (void **)&zone, index, 1);
 625                 if (ret == 0)
 626                         break;
 627                 index = (zone->end >> PAGE_CACHE_SHIFT) + 1;
 628                 if (zone->locked) {
 629                         if (zone->elems > top_locked_elems) {
 630                                 top_locked_elems = zone->elems;
 631                                 top_locked_zone = zone;
 632                         }
 633                 } else {
 634                         if (zone->elems > top_elems) {
 635                                 top_elems = zone->elems;
 636                                 top_zone = zone;
 637                         }
 638                 }
 639         }
 640         if (top_zone)
 641                 dev->reada_curr_zone = top_zone;
 642         else if (top_locked_zone)
 643                 dev->reada_curr_zone = top_locked_zone;
 644         else
 645                 return 0;
 646
 647         dev->reada_next = dev->reada_curr_zone->start;
 648         kref_get(&dev->reada_curr_zone->refcnt);
 649         reada_peer_zones_set_lock(dev->reada_curr_zone, 1);
 650
 651         return 1;
 652 }
 653
 654 static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
 655                                    struct btrfs_device *dev)
 656 {
 657         struct reada_extent *re = NULL;
 658         int mirror_num = 0;
 659         struct extent_buffer *eb = NULL;
 660         u64 logical;
 661         int ret;
 662         int i;
 663         int need_kick = 0;
 664
 665         spin_lock(&fs_info->reada_lock);
 666         if (dev->reada_curr_zone == NULL) {
 667                 ret = reada_pick_zone(dev);
 668                 if (!ret) {
 669                         spin_unlock(&fs_info->reada_lock);
 670                         return 0;
 671                 }
 672         }
 673         /*
 674          * FIXME currently we issue the reads one extent at a time. If we have
 675          * a contiguous block of extents, we could also coagulate them or use
 676          * plugging to speed things up
 677          */
 678         ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
 679                                      dev->reada_next >> PAGE_CACHE_SHIFT, 1);
 680         if (ret == 0 || re->logical >= dev->reada_curr_zone->end) {
 681                 ret = reada_pick_zone(dev);
 682                 if (!ret) {
 683                         spin_unlock(&fs_info->reada_lock);
 684                         return 0;
 685                 }
 686                 re = NULL;
 687                 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
 688                                         dev->reada_next >> PAGE_CACHE_SHIFT, 1);
 689         }
 690         if (ret == 0) {
 691                 spin_unlock(&fs_info->reada_lock);
 692                 return 0;
 693         }
 694         dev->reada_next = re->logical + fs_info->tree_root->nodesize;
 695         re->refcnt++;
 696
 697         spin_unlock(&fs_info->reada_lock);
 698
 699         /*
 700          * find mirror num
 701          */
 702         for (i = 0; i < re->nzones; ++i) {
 703                 if (re->zones[i]->device == dev) {
 704                         mirror_num = i + 1;
 705                         break;
 706                 }
 707         }
 708         logical = re->logical;
 709
 710         spin_lock(&re->lock);
 711         if (re->scheduled_for == NULL) {
 712                 re->scheduled_for = dev;
 713                 need_kick = 1;
 714         }
 715         spin_unlock(&re->lock);
 716
 717         reada_extent_put(fs_info, re);
 718
 719         if (!need_kick)
 720                 return 0;
 721
 722         atomic_inc(&dev->reada_in_flight);
 723         ret = reada_tree_block_flagged(fs_info->extent_root, logical,
 724                         mirror_num, &eb);
 725         if (ret)
 726                 __readahead_hook(fs_info->extent_root, NULL, logical, ret);
 727         else if (eb)
 728                 __readahead_hook(fs_info->extent_root, eb, eb->start, ret);
 729
 730         if (eb)
 731                 free_extent_buffer(eb);
 732
 733         return 1;
 734
 735 }
 736
 737 static void reada_start_machine_worker(struct btrfs_work *work)
 738 {
 739         struct reada_machine_work *rmw;
 740         struct btrfs_fs_info *fs_info;
 741         int old_ioprio;
 742
 743         rmw = container_of(work, struct reada_machine_work, work);
 744         fs_info = rmw->fs_info;
 745
 746         kfree(rmw);
 747
 748         old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current),
 749                                        task_nice_ioprio(current));
 750         set_task_ioprio(current, BTRFS_IOPRIO_READA);
 751         __reada_start_machine(fs_info);
 752         set_task_ioprio(current, old_ioprio);
 753 }
 754
 755 static void __reada_start_machine(struct btrfs_fs_info *fs_info)
 756 {
 757         struct btrfs_device *device;
 758         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 759         u64 enqueued;
 760         u64 total = 0;
 761         int i;
 762
 763         do {
 764                 enqueued = 0;
 765                 list_for_each_entry(device, &fs_devices->devices, dev_list) {
 766                         if (atomic_read(&device->reada_in_flight) <
 767                             MAX_IN_FLIGHT)
 768                                 enqueued += reada_start_machine_dev(fs_info,
 769                                                                     device);
 770                 }
 771                 total += enqueued;
 772         } while (enqueued && total < 10000);
 773
 774         if (enqueued == 0)
 775                 return;
 776
 777         /*
 778          * If everything is already in the cache, this is effectively single
 779          * threaded. To a) not hold the caller for too long and b) to utilize
 780          * more cores, we broke the loop above after 10000 iterations and now
 781          * enqueue to workers to finish it. This will distribute the load to
 782          * the cores.
 783          */
 784         for (i = 0; i < 2; ++i)
 785                 reada_start_machine(fs_info);
 786 }
 787
 788 static void reada_start_machine(struct btrfs_fs_info *fs_info)
 789 {
 790         struct reada_machine_work *rmw;
 791
 792         rmw = kzalloc(sizeof(*rmw), GFP_NOFS);
 793         if (!rmw) {
 794                 /* FIXME we cannot handle this properly right now */
 795                 BUG();
 796         }
 797         btrfs_init_work(&rmw->work, btrfs_readahead_helper,
 798                         reada_start_machine_worker, NULL, NULL);
 799         rmw->fs_info = fs_info;
 800
 801         btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
 802 }
 803
 804 #ifdef DEBUG
 805 static void dump_devs(struct btrfs_fs_info *fs_info, int all)
 806 {
 807         struct btrfs_device *device;
 808         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 809         unsigned long index;
 810         int ret;
 811         int i;
 812         int j;
 813         int cnt;
 814
 815         spin_lock(&fs_info->reada_lock);
 816         list_for_each_entry(device, &fs_devices->devices, dev_list) {
 817                 printk(KERN_DEBUG "dev %lld has %d in flight\n", device->devid,
 818                         atomic_read(&device->reada_in_flight));
 819                 index = 0;
 820                 while (1) {
 821                         struct reada_zone *zone;
 822                         ret = radix_tree_gang_lookup(&device->reada_zones,
 823                                                      (void **)&zone, index, 1);
 824                         if (ret == 0)
 825                                 break;
 826                         printk(KERN_DEBUG "  zone %llu-%llu elems %llu locked "
 827                                 "%d devs", zone->start, zone->end, zone->elems,
 828                                 zone->locked);
 829                         for (j = 0; j < zone->ndevs; ++j) {
 830                                 printk(KERN_CONT " %lld",
 831                                         zone->devs[j]->devid);
 832                         }
 833                         if (device->reada_curr_zone == zone)
 834                                 printk(KERN_CONT " curr off %llu",
 835                                         device->reada_next - zone->start);
 836                         printk(KERN_CONT "\n");
 837                         index = (zone->end >> PAGE_CACHE_SHIFT) + 1;
 838                 }
 839                 cnt = 0;
 840                 index = 0;
 841                 while (all) {
 842                         struct reada_extent *re = NULL;
 843
 844                         ret = radix_tree_gang_lookup(&device->reada_extents,
 845                                                      (void **)&re, index, 1);
 846                         if (ret == 0)
 847                                 break;
 848                         printk(KERN_DEBUG
 849                                 "  re: logical %llu size %u empty %d for %lld",
 850                                 re->logical, fs_info->tree_root->nodesize,
 851                                 list_empty(&re->extctl), re->scheduled_for ?
 852                                 re->scheduled_for->devid : -1);
 853
 854                         for (i = 0; i < re->nzones; ++i) {
 855                                 printk(KERN_CONT " zone %llu-%llu devs",
 856                                         re->zones[i]->start,
 857                                         re->zones[i]->end);
 858                                 for (j = 0; j < re->zones[i]->ndevs; ++j) {
 859                                         printk(KERN_CONT " %lld",
 860                                                 re->zones[i]->devs[j]->devid);
 861                                 }
 862                         }
 863                         printk(KERN_CONT "\n");
 864                         index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
 865                         if (++cnt > 15)
 866                                 break;
 867                 }
 868         }
 869
 870         index = 0;
 871         cnt = 0;
 872         while (all) {
 873                 struct reada_extent *re = NULL;
 874
 875                 ret = radix_tree_gang_lookup(&fs_info->reada_tree, (void **)&re,
 876                                              index, 1);
 877                 if (ret == 0)
 878                         break;
 879                 if (!re->scheduled_for) {
 880                         index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
 881                         continue;
 882                 }
 883                 printk(KERN_DEBUG
 884                         "re: logical %llu size %u list empty %d for %lld",
 885                         re->logical, fs_info->tree_root->nodesize,
 886                         list_empty(&re->extctl),
 887                         re->scheduled_for ? re->scheduled_for->devid : -1);
 888                 for (i = 0; i < re->nzones; ++i) {
 889                         printk(KERN_CONT " zone %llu-%llu devs",
 890                                 re->zones[i]->start,
 891                                 re->zones[i]->end);
 892                         for (i = 0; i < re->nzones; ++i) {
 893                                 printk(KERN_CONT " zone %llu-%llu devs",
 894                                         re->zones[i]->start,
 895                                         re->zones[i]->end);
 896                                 for (j = 0; j < re->zones[i]->ndevs; ++j) {
 897                                         printk(KERN_CONT " %lld",
 898                                                 re->zones[i]->devs[j]->devid);
 899                                 }
 900                         }
 901                 }
 902                 printk(KERN_CONT "\n");
 903                 index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
 904         }
 905         spin_unlock(&fs_info->reada_lock);
 906 }
 907 #endif
 908
 909 /*
 910  * interface
 911  */
 912 struct reada_control *btrfs_reada_add(struct btrfs_root *root,
 913                         struct btrfs_key *key_start, struct btrfs_key *key_end)
 914 {
 915         struct reada_control *rc;
 916         u64 start;
 917         u64 generation;
 918         int level;
 919         struct extent_buffer *node;
 920         static struct btrfs_key max_key = {
 921                 .objectid = (u64)-1,
 922                 .type = (u8)-1,
 923                 .offset = (u64)-1
 924         };
 925
 926         rc = kzalloc(sizeof(*rc), GFP_NOFS);
 927         if (!rc)
 928                 return ERR_PTR(-ENOMEM);
 929
 930         rc->root = root;
 931         rc->key_start = *key_start;
 932         rc->key_end = *key_end;
 933         atomic_set(&rc->elems, 0);
 934         init_waitqueue_head(&rc->wait);
 935         kref_init(&rc->refcnt);
 936         kref_get(&rc->refcnt); /* one ref for having elements */
 937
 938         node = btrfs_root_node(root);
 939         start = node->start;
 940         level = btrfs_header_level(node);
 941         generation = btrfs_header_generation(node);
 942         free_extent_buffer(node);
 943
 944         if (reada_add_block(rc, start, &max_key, level, generation)) {
 945                 kfree(rc);
 946                 return ERR_PTR(-ENOMEM);
 947         }
 948
 949         reada_start_machine(root->fs_info);
 950
 951         return rc;
 952 }
 953
 954 #ifdef DEBUG
 955 int btrfs_reada_wait(void *handle)
 956 {
 957         struct reada_control *rc = handle;
 958
 959         while (atomic_read(&rc->elems)) {
 960                 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
 961                                    5 * HZ);
 962                 dump_devs(rc->root->fs_info,
 963                           atomic_read(&rc->elems) < 10 ? 1 : 0);
 964         }
 965
 966         dump_devs(rc->root->fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
 967
 968         kref_put(&rc->refcnt, reada_control_release);
 969
 970         return 0;
 971 }
 972 #else
 973 int btrfs_reada_wait(void *handle)
 974 {
 975         struct reada_control *rc = handle;
 976
 977         while (atomic_read(&rc->elems)) {
 978                 wait_event(rc->wait, atomic_read(&rc->elems) == 0);
 979         }
 980
 981         kref_put(&rc->refcnt, reada_control_release);
 982
 983         return 0;
 984 }
 985 #endif
 986
 987 void btrfs_reada_detach(void *handle)
 988 {
 989         struct reada_control *rc = handle;
 990
 991         kref_put(&rc->refcnt, reada_control_release);
 992 }