sys/vfs/hammer2/hammer2_freemap.c

   1 /*
   2  * Copyright (c) 2011-2014 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@dragonflybsd.org>
   6  * by Venkatesh Srinivas <vsrinivas@dragonflybsd.org>
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  *
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in
  16  *    the documentation and/or other materials provided with the
  17  *    distribution.
  18  * 3. Neither the name of The DragonFly Project nor the names of its
  19  *    contributors may be used to endorse or promote products derived
  20  *    from this software without specific, prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  23  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  24  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  25  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  26  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  27  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  28  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  29  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  30  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  31  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  32  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35 #include <sys/param.h>
  36 #include <sys/systm.h>
  37 #include <sys/kernel.h>
  38 #include <sys/fcntl.h>
  39 #include <sys/buf.h>
  40 #include <sys/proc.h>
  41 #include <sys/namei.h>
  42 #include <sys/mount.h>
  43 #include <sys/vnode.h>
  44 #include <sys/mountctl.h>
  45
  46 #include "hammer2.h"
  47
  48 #define FREEMAP_DEBUG   0
  49
  50 struct hammer2_fiterate {
  51         hammer2_off_t   bpref;
  52         hammer2_off_t   bnext;
  53         int             loops;
  54 };
  55
  56 typedef struct hammer2_fiterate hammer2_fiterate_t;
  57
  58 static int hammer2_freemap_try_alloc(hammer2_trans_t *trans,
  59                         hammer2_chain_t **parentp, hammer2_blockref_t *bref,
  60                         int radix, hammer2_fiterate_t *iter);
  61 static void hammer2_freemap_init(hammer2_trans_t *trans, hammer2_dev_t *hmp,
  62                         hammer2_key_t key, hammer2_chain_t *chain);
  63 static int hammer2_bmap_alloc(hammer2_trans_t *trans, hammer2_dev_t *hmp,
  64                         hammer2_bmap_data_t *bmap, uint16_t class,
  65                         int n, int radix, hammer2_key_t *basep);
  66 static int hammer2_freemap_iterate(hammer2_trans_t *trans,
  67                         hammer2_chain_t **parentp, hammer2_chain_t **chainp,
  68                         hammer2_fiterate_t *iter);
  69
  70 static __inline
  71 int
  72 hammer2_freemapradix(int radix)
  73 {
  74         return(radix);
  75 }
  76
  77 /*
  78  * Calculate the device offset for the specified FREEMAP_NODE or FREEMAP_LEAF
  79  * bref.  Return a combined media offset and physical size radix.  Freemap
  80  * chains use fixed storage offsets in the 4MB reserved area at the
  81  * beginning of each 2GB zone
  82  *
  83  * Rotate between four possibilities.  Theoretically this means we have three
  84  * good freemaps in case of a crash which we can use as a base for the fixup
  85  * scan at mount-time.
  86  */
  87 #define H2FMBASE(key, radix)    ((key) & ~(((hammer2_off_t)1 << (radix)) - 1))
  88 #define H2FMSHIFT(radix)        ((hammer2_off_t)1 << (radix))
  89
  90 static
  91 int
  92 hammer2_freemap_reserve(hammer2_trans_t *trans, hammer2_chain_t *chain,
  93                         int radix)
  94 {
  95         hammer2_blockref_t *bref = &chain->bref;
  96         hammer2_off_t off;
  97         int index;
  98         int index_inc;
  99         size_t bytes;
 100
 101         /*
 102          * Physical allocation size.
 103          */
 104         bytes = (size_t)1 << radix;
 105
 106         /*
 107          * Calculate block selection index 0..7 of current block.  If this
 108          * is the first allocation of the block (verses a modification of an
 109          * existing block), we use index 0, otherwise we use the next rotating
 110          * index.
 111          */
 112         if ((bref->data_off & ~HAMMER2_OFF_MASK_RADIX) == 0) {
 113                 index = 0;
 114         } else {
 115                 off = bref->data_off & ~HAMMER2_OFF_MASK_RADIX &
 116                       (((hammer2_off_t)1 <<
 117                         HAMMER2_FREEMAP_LEVEL1_RADIX) - 1);
 118                 off = off / HAMMER2_PBUFSIZE;
 119                 KKASSERT(off >= HAMMER2_ZONE_FREEMAP_00 &&
 120                          off < HAMMER2_ZONE_FREEMAP_END);
 121                 index = (int)(off - HAMMER2_ZONE_FREEMAP_00) /
 122                         HAMMER2_ZONE_FREEMAP_INC;
 123                 KKASSERT(index >= 0 && index < HAMMER2_NFREEMAPS);
 124                 if (++index == HAMMER2_NFREEMAPS)
 125                         index = 0;
 126         }
 127
 128         /*
 129          * Calculate the block offset of the reserved block.  This will
 130          * point into the 4MB reserved area at the base of the appropriate
 131          * 2GB zone, once added to the FREEMAP_x selection above.
 132          */
 133         index_inc = index * HAMMER2_ZONE_FREEMAP_INC;
 134
 135         switch(bref->keybits) {
 136         /* case HAMMER2_FREEMAP_LEVEL6_RADIX: not applicable */
 137         case HAMMER2_FREEMAP_LEVEL5_RADIX:      /* 2EB */
 138                 KKASSERT(bref->type == HAMMER2_BREF_TYPE_FREEMAP_NODE);
 139                 KKASSERT(bytes == HAMMER2_FREEMAP_LEVELN_PSIZE);
 140                 off = H2FMBASE(bref->key, HAMMER2_FREEMAP_LEVEL5_RADIX) +
 141                       (index_inc + HAMMER2_ZONE_FREEMAP_00 +
 142                        HAMMER2_ZONEFM_LEVEL5) * HAMMER2_PBUFSIZE;
 143                 break;
 144         case HAMMER2_FREEMAP_LEVEL4_RADIX:      /* 2EB */
 145                 KKASSERT(bref->type == HAMMER2_BREF_TYPE_FREEMAP_NODE);
 146                 KKASSERT(bytes == HAMMER2_FREEMAP_LEVELN_PSIZE);
 147                 off = H2FMBASE(bref->key, HAMMER2_FREEMAP_LEVEL4_RADIX) +
 148                       (index_inc + HAMMER2_ZONE_FREEMAP_00 +
 149                        HAMMER2_ZONEFM_LEVEL4) * HAMMER2_PBUFSIZE;
 150                 break;
 151         case HAMMER2_FREEMAP_LEVEL3_RADIX:      /* 2PB */
 152                 KKASSERT(bref->type == HAMMER2_BREF_TYPE_FREEMAP_NODE);
 153                 KKASSERT(bytes == HAMMER2_FREEMAP_LEVELN_PSIZE);
 154                 off = H2FMBASE(bref->key, HAMMER2_FREEMAP_LEVEL3_RADIX) +
 155                       (index_inc + HAMMER2_ZONE_FREEMAP_00 +
 156                        HAMMER2_ZONEFM_LEVEL3) * HAMMER2_PBUFSIZE;
 157                 break;
 158         case HAMMER2_FREEMAP_LEVEL2_RADIX:      /* 2TB */
 159                 KKASSERT(bref->type == HAMMER2_BREF_TYPE_FREEMAP_NODE);
 160                 KKASSERT(bytes == HAMMER2_FREEMAP_LEVELN_PSIZE);
 161                 off = H2FMBASE(bref->key, HAMMER2_FREEMAP_LEVEL2_RADIX) +
 162                       (index_inc + HAMMER2_ZONE_FREEMAP_00 +
 163                        HAMMER2_ZONEFM_LEVEL2) * HAMMER2_PBUFSIZE;
 164                 break;
 165         case HAMMER2_FREEMAP_LEVEL1_RADIX:      /* 2GB */
 166                 KKASSERT(bref->type == HAMMER2_BREF_TYPE_FREEMAP_LEAF);
 167                 KKASSERT(bytes == HAMMER2_FREEMAP_LEVELN_PSIZE);
 168                 off = H2FMBASE(bref->key, HAMMER2_FREEMAP_LEVEL1_RADIX) +
 169                       (index_inc + HAMMER2_ZONE_FREEMAP_00 +
 170                        HAMMER2_ZONEFM_LEVEL1) * HAMMER2_PBUFSIZE;
 171                 break;
 172         default:
 173                 panic("freemap: bad radix(2) %p %d\n", bref, bref->keybits);
 174                 /* NOT REACHED */
 175                 off = (hammer2_off_t)-1;
 176                 break;
 177         }
 178         bref->data_off = off | radix;
 179 #if FREEMAP_DEBUG
 180         kprintf("FREEMAP BLOCK TYPE %d %016jx/%d DATA_OFF=%016jx\n",
 181                 bref->type, bref->key, bref->keybits, bref->data_off);
 182 #endif
 183         return (0);
 184 }
 185
 186 /*
 187  * Normal freemap allocator
 188  *
 189  * Use available hints to allocate space using the freemap.  Create missing
 190  * freemap infrastructure on-the-fly as needed (including marking initial
 191  * allocations using the iterator as allocated, instantiating new 2GB zones,
 192  * and dealing with the end-of-media edge case).
 193  *
 194  * ip and bpref are only used as a heuristic to determine locality of
 195  * reference.  bref->key may also be used heuristically.
 196  */
 197 int
 198 hammer2_freemap_alloc(hammer2_trans_t *trans, hammer2_chain_t *chain,
 199                       size_t bytes)
 200 {
 201         hammer2_dev_t *hmp = chain->hmp;
 202         hammer2_blockref_t *bref = &chain->bref;
 203         hammer2_chain_t *parent;
 204         int radix;
 205         int error;
 206         unsigned int hindex;
 207         hammer2_fiterate_t iter;
 208
 209         /*
 210          * Validate the allocation size.  It must be a power of 2.
 211          *
 212          * For now require that the caller be aware of the minimum
 213          * allocation (1K).
 214          */
 215         radix = hammer2_getradix(bytes);
 216         KKASSERT((size_t)1 << radix == bytes);
 217
 218         if (bref->type == HAMMER2_BREF_TYPE_FREEMAP_NODE ||
 219             bref->type == HAMMER2_BREF_TYPE_FREEMAP_LEAF) {
 220                 /*
 221                  * Freemap blocks themselves are assigned from the reserve
 222                  * area, not allocated from the freemap.
 223                  */
 224                 error = hammer2_freemap_reserve(trans, chain, radix);
 225                 return error;
 226         }
 227
 228         KKASSERT(bytes >= HAMMER2_ALLOC_MIN && bytes <= HAMMER2_ALLOC_MAX);
 229
 230         if (trans->flags & (HAMMER2_TRANS_ISFLUSH | HAMMER2_TRANS_PREFLUSH))
 231                 ++trans->sync_xid;
 232
 233         /*
 234          * Calculate the starting point for our allocation search.
 235          *
 236          * Each freemap leaf is dedicated to a specific freemap_radix.
 237          * The freemap_radix can be more fine-grained than the device buffer
 238          * radix which results in inodes being grouped together in their
 239          * own segment, terminal-data (16K or less) and initial indirect
 240          * block being grouped together, and then full-indirect and full-data
 241          * blocks (64K) being grouped together.
 242          *
 243          * The single most important aspect of this is the inode grouping
 244          * because that is what allows 'find' and 'ls' and other filesystem
 245          * topology operations to run fast.
 246          */
 247 #if 0
 248         if (bref->data_off & ~HAMMER2_OFF_MASK_RADIX)
 249                 bpref = bref->data_off & ~HAMMER2_OFF_MASK_RADIX;
 250         else if (trans->tmp_bpref)
 251                 bpref = trans->tmp_bpref;
 252         else if (trans->tmp_ip)
 253                 bpref = trans->tmp_ip->chain->bref.data_off;
 254         else
 255 #endif
 256         /*
 257          * Heuristic tracking index.  We would like one for each distinct
 258          * bref type if possible.  heur_freemap[] has room for two classes
 259          * for each type.  At a minimum we have to break-up our heuristic
 260          * by device block sizes.
 261          */
 262         hindex = hammer2_devblkradix(radix) - HAMMER2_MINIORADIX;
 263         KKASSERT(hindex < HAMMER2_FREEMAP_HEUR_NRADIX);
 264         hindex += bref->type * HAMMER2_FREEMAP_HEUR_NRADIX;
 265         hindex &= HAMMER2_FREEMAP_HEUR_TYPES * HAMMER2_FREEMAP_HEUR_NRADIX - 1;
 266         KKASSERT(hindex < HAMMER2_FREEMAP_HEUR);
 267
 268         iter.bpref = hmp->heur_freemap[hindex];
 269
 270         /*
 271          * Make sure bpref is in-bounds.  It's ok if bpref covers a zone's
 272          * reserved area, the try code will iterate past it.
 273          */
 274         if (iter.bpref > hmp->voldata.volu_size)
 275                 iter.bpref = hmp->voldata.volu_size - 1;
 276
 277         /*
 278          * Iterate the freemap looking for free space before and after.
 279          */
 280         parent = &hmp->fchain;
 281         hammer2_chain_ref(parent);
 282         hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS);
 283         error = EAGAIN;
 284         iter.bnext = iter.bpref;
 285         iter.loops = 0;
 286
 287         while (error == EAGAIN) {
 288                 error = hammer2_freemap_try_alloc(trans, &parent, bref,
 289                                                   radix, &iter);
 290         }
 291         hmp->heur_freemap[hindex] = iter.bnext;
 292         hammer2_chain_unlock(parent);
 293         hammer2_chain_drop(parent);
 294
 295         if (trans->flags & (HAMMER2_TRANS_ISFLUSH | HAMMER2_TRANS_PREFLUSH))
 296                 --trans->sync_xid;
 297
 298         return (error);
 299 }
 300
 301 static int
 302 hammer2_freemap_try_alloc(hammer2_trans_t *trans, hammer2_chain_t **parentp,
 303                           hammer2_blockref_t *bref, int radix,
 304                           hammer2_fiterate_t *iter)
 305 {
 306         hammer2_dev_t *hmp = (*parentp)->hmp;
 307         hammer2_off_t l0size;
 308         hammer2_off_t l1size;
 309         hammer2_off_t l1mask;
 310         hammer2_key_t key_dummy;
 311         hammer2_chain_t *chain;
 312         hammer2_off_t key;
 313         size_t bytes;
 314         uint16_t class;
 315         int error = 0;
 316         int cache_index = -1;
 317
 318         /*
 319          * Calculate the number of bytes being allocated, the number
 320          * of contiguous bits of bitmap being allocated, and the bitmap
 321          * mask.
 322          *
 323          * WARNING! cpu hardware may mask bits == 64 -> 0 and blow up the
 324          *          mask calculation.
 325          */
 326         bytes = (size_t)1 << radix;
 327         class = (bref->type << 8) | hammer2_devblkradix(radix);
 328
 329         /*
 330          * Lookup the level1 freemap chain, creating and initializing one
 331          * if necessary.  Intermediate levels will be created automatically
 332          * when necessary by hammer2_chain_create().
 333          */
 334         key = H2FMBASE(iter->bnext, HAMMER2_FREEMAP_LEVEL1_RADIX);
 335         l0size = H2FMSHIFT(HAMMER2_FREEMAP_LEVEL0_RADIX);
 336         l1size = H2FMSHIFT(HAMMER2_FREEMAP_LEVEL1_RADIX);
 337         l1mask = l1size - 1;
 338
 339         chain = hammer2_chain_lookup(parentp, &key_dummy, key, key + l1mask,
 340                                      &cache_index,
 341                                      HAMMER2_LOOKUP_ALWAYS |
 342                                      HAMMER2_LOOKUP_MATCHIND);
 343
 344         if (chain == NULL) {
 345                 /*
 346                  * Create the missing leaf, be sure to initialize
 347                  * the auxillary freemap tracking information in
 348                  * the bref.check.freemap structure.
 349                  */
 350 #if 0
 351                 kprintf("freemap create L1 @ %016jx bpref %016jx\n",
 352                         key, iter->bpref);
 353 #endif
 354                 error = hammer2_chain_create(trans, parentp, &chain, hmp->spmp,
 355                                      key, HAMMER2_FREEMAP_LEVEL1_RADIX,
 356                                      HAMMER2_BREF_TYPE_FREEMAP_LEAF,
 357                                      HAMMER2_FREEMAP_LEVELN_PSIZE,
 358                                      0);
 359                 KKASSERT(error == 0);
 360                 if (error == 0) {
 361                         hammer2_chain_modify(trans, chain, 0);
 362                         bzero(&chain->data->bmdata[0],
 363                               HAMMER2_FREEMAP_LEVELN_PSIZE);
 364                         chain->bref.check.freemap.bigmask = (uint32_t)-1;
 365                         chain->bref.check.freemap.avail = l1size;
 366                         /* bref.methods should already be inherited */
 367
 368                         hammer2_freemap_init(trans, hmp, key, chain);
 369                 }
 370         } else if (chain->error) {
 371                 /*
 372                  * Error during lookup.
 373                  */
 374                 kprintf("hammer2_freemap_try_alloc: %016jx: error %s\n",
 375                         (intmax_t)bref->data_off,
 376                         hammer2_error_str(chain->error));
 377                 error = EIO;
 378         } else if ((chain->bref.check.freemap.bigmask &
 379                    ((size_t)1 << radix)) == 0) {
 380                 /*
 381                  * Already flagged as not having enough space
 382                  */
 383                 error = ENOSPC;
 384         } else {
 385                 /*
 386                  * Modify existing chain to setup for adjustment.
 387                  */
 388                 hammer2_chain_modify(trans, chain, 0);
 389         }
 390
 391         /*
 392          * Scan 2MB entries.
 393          */
 394         if (error == 0) {
 395                 hammer2_bmap_data_t *bmap;
 396                 hammer2_key_t base_key;
 397                 int count;
 398                 int start;
 399                 int n;
 400
 401                 KKASSERT(chain->bref.type == HAMMER2_BREF_TYPE_FREEMAP_LEAF);
 402                 start = (int)((iter->bnext - key) >>
 403                               HAMMER2_FREEMAP_LEVEL0_RADIX);
 404                 KKASSERT(start >= 0 && start < HAMMER2_FREEMAP_COUNT);
 405                 hammer2_chain_modify(trans, chain, 0);
 406
 407                 error = ENOSPC;
 408                 for (count = 0; count < HAMMER2_FREEMAP_COUNT; ++count) {
 409                         int availchk;
 410
 411                         if (start + count >= HAMMER2_FREEMAP_COUNT &&
 412                             start - count < 0) {
 413                                 break;
 414                         }
 415
 416                         /*
 417                          * Calculate bmap pointer
 418                          *
 419                          * NOTE: bmap pointer is invalid if n >= FREEMAP_COUNT.
 420                          */
 421                         n = start + count;
 422                         bmap = &chain->data->bmdata[n];
 423
 424                         if (n >= HAMMER2_FREEMAP_COUNT) {
 425                                 availchk = 0;
 426                         } else if (bmap->avail) {
 427                                 availchk = 1;
 428                         } else if (radix < HAMMER2_FREEMAP_BLOCK_RADIX &&
 429                                   (bmap->linear & HAMMER2_FREEMAP_BLOCK_MASK)) {
 430                                 availchk = 1;
 431                         } else {
 432                                 availchk = 0;
 433                         }
 434
 435                         if (availchk &&
 436                             (bmap->class == 0 || bmap->class == class)) {
 437                                 base_key = key + n * l0size;
 438                                 error = hammer2_bmap_alloc(trans, hmp, bmap,
 439                                                            class, n, radix,
 440                                                            &base_key);
 441                                 if (error != ENOSPC) {
 442                                         key = base_key;
 443                                         break;
 444                                 }
 445                         }
 446
 447                         /*
 448                          * Must recalculate after potentially having called
 449                          * hammer2_bmap_alloc() above in case chain was
 450                          * reallocated.
 451                          *
 452                          * NOTE: bmap pointer is invalid if n < 0.
 453                          */
 454                         n = start - count;
 455                         bmap = &chain->data->bmdata[n];
 456                         if (n < 0) {
 457                                 availchk = 0;
 458                         } else if (bmap->avail) {
 459                                 availchk = 1;
 460                         } else if (radix < HAMMER2_FREEMAP_BLOCK_RADIX &&
 461                                   (bmap->linear & HAMMER2_FREEMAP_BLOCK_MASK)) {
 462                                 availchk = 1;
 463                         } else {
 464                                 availchk = 0;
 465                         }
 466
 467                         if (availchk &&
 468                             (bmap->class == 0 || bmap->class == class)) {
 469                                 base_key = key + n * l0size;
 470                                 error = hammer2_bmap_alloc(trans, hmp, bmap,
 471                                                            class, n, radix,
 472                                                            &base_key);
 473                                 if (error != ENOSPC) {
 474                                         key = base_key;
 475                                         break;
 476                                 }
 477                         }
 478                 }
 479                 if (error == ENOSPC) {
 480                         chain->bref.check.freemap.bigmask &=
 481                                 (uint32_t)~((size_t)1 << radix);
 482                 }
 483                 /* XXX also scan down from original count */
 484         }
 485
 486         if (error == 0) {
 487                 /*
 488                  * Assert validity.  Must be beyond the static allocator used
 489                  * by newfs_hammer2 (and thus also beyond the aux area),
 490                  * not go past the volume size, and must not be in the
 491                  * reserved segment area for a zone.
 492                  */
 493                 KKASSERT(key >= hmp->voldata.allocator_beg &&
 494                          key + bytes <= hmp->voldata.volu_size);
 495                 KKASSERT((key & HAMMER2_ZONE_MASK64) >= HAMMER2_ZONE_SEG);
 496                 bref->data_off = key | radix;
 497
 498 #if 0
 499                 kprintf("alloc cp=%p %016jx %016jx using %016jx\n",
 500                         chain,
 501                         bref->key, bref->data_off, chain->bref.data_off);
 502 #endif
 503         } else if (error == ENOSPC) {
 504                 /*
 505                  * Return EAGAIN with next iteration in iter->bnext, or
 506                  * return ENOSPC if the allocation map has been exhausted.
 507                  */
 508                 error = hammer2_freemap_iterate(trans, parentp, &chain, iter);
 509         }
 510
 511         /*
 512          * Cleanup
 513          */
 514         if (chain) {
 515                 hammer2_chain_unlock(chain);
 516                 hammer2_chain_drop(chain);
 517         }
 518         return (error);
 519 }
 520
 521 /*
 522  * Allocate (1<<radix) bytes from the bmap whos base data offset is (*basep).
 523  *
 524  * If the linear iterator is mid-block we use it directly (the bitmap should
 525  * already be marked allocated), otherwise we search for a block in the bitmap
 526  * that fits the allocation request.
 527  *
 528  * A partial bitmap allocation sets the minimum bitmap granularity (16KB)
 529  * to fully allocated and adjusts the linear allocator to allow the
 530  * remaining space to be allocated.
 531  */
 532 static
 533 int
 534 hammer2_bmap_alloc(hammer2_trans_t *trans, hammer2_dev_t *hmp,
 535                    hammer2_bmap_data_t *bmap,
 536                    uint16_t class, int n, int radix, hammer2_key_t *basep)
 537 {
 538         hammer2_io_t *dio;
 539         size_t size;
 540         size_t bgsize;
 541         int bmradix;
 542         hammer2_bitmap_t bmmask;
 543         int offset;
 544         int error;
 545         int i;
 546         int j;
 547
 548         /*
 549          * Take into account 2-bits per block when calculating bmradix.
 550          */
 551         size = (size_t)1 << radix;
 552
 553         if (radix <= HAMMER2_FREEMAP_BLOCK_RADIX) {
 554                 bmradix = 2;
 555                 /* (16K) 2 bits per allocation block */
 556         } else {
 557                 bmradix = (hammer2_bitmap_t)2 <<
 558                           (radix - HAMMER2_FREEMAP_BLOCK_RADIX);
 559                 /* (32K-256K) 4, 8, 16, 32 bits per allocation block */
 560         }
 561
 562         /*
 563          * Use the linear iterator to pack small allocations, otherwise
 564          * fall-back to finding a free 16KB chunk.  The linear iterator
 565          * is only valid when *NOT* on a freemap chunking boundary (16KB).
 566          * If it is the bitmap must be scanned.  It can become invalid
 567          * once we pack to the boundary.  We adjust it after a bitmap
 568          * allocation only for sub-16KB allocations (so the perfectly good
 569          * previous value can still be used for fragments when 16KB+
 570          * allocations are made).
 571          *
 572          * Beware of hardware artifacts when bmradix == 64 (intermediate
 573          * result can wind up being '1' instead of '0' if hardware masks
 574          * bit-count & 31).
 575          *
 576          * NOTE: j needs to be even in the j= calculation.  As an artifact
 577          *       of the /2 division, our bitmask has to clear bit 0.
 578          *
 579          * NOTE: TODO this can leave little unallocatable fragments lying
 580          *       around.
 581          */
 582         if (((uint32_t)bmap->linear & HAMMER2_FREEMAP_BLOCK_MASK) + size <=
 583             HAMMER2_FREEMAP_BLOCK_SIZE &&
 584             (bmap->linear & HAMMER2_FREEMAP_BLOCK_MASK) &&
 585             bmap->linear < HAMMER2_SEGSIZE) {
 586                 KKASSERT(bmap->linear >= 0 &&
 587                          bmap->linear + size <= HAMMER2_SEGSIZE &&
 588                          (bmap->linear & (HAMMER2_ALLOC_MIN - 1)) == 0);
 589                 offset = bmap->linear;
 590                 i = offset / (HAMMER2_SEGSIZE / 8);
 591                 j = (offset / (HAMMER2_FREEMAP_BLOCK_SIZE / 2)) & 30;
 592                 bmmask = (bmradix == HAMMER2_BMAP_BITS_PER_ELEMENT) ?
 593                          HAMMER2_BMAP_ALLONES :
 594                          ((hammer2_bitmap_t)1 << bmradix) - 1;
 595                 bmmask <<= j;
 596                 bmap->linear = offset + size;
 597         } else {
 598                 for (i = 0; i < HAMMER2_BMAP_ELEMENTS; ++i) {
 599                         bmmask = (bmradix == HAMMER2_BMAP_BITS_PER_ELEMENT) ?
 600                                  HAMMER2_BMAP_ALLONES :
 601                                  ((hammer2_bitmap_t)1 << bmradix) - 1;
 602                         for (j = 0;
 603                              j < HAMMER2_BMAP_BITS_PER_ELEMENT;
 604                              j += bmradix) {
 605                                 if ((bmap->bitmapq[i] & bmmask) == 0)
 606                                         goto success;
 607                                 bmmask <<= bmradix;
 608                         }
 609                 }
 610                 /*fragments might remain*/
 611                 /*KKASSERT(bmap->avail == 0);*/
 612                 return (ENOSPC);
 613 success:
 614                 offset = i * (HAMMER2_SEGSIZE / HAMMER2_BMAP_ELEMENTS) +
 615                          (j * (HAMMER2_FREEMAP_BLOCK_SIZE / 2));
 616                 if (size & HAMMER2_FREEMAP_BLOCK_MASK)
 617                         bmap->linear = offset + size;
 618         }
 619
 620         /* 8 x (64/2) -> 256 x 16K -> 4MB */
 621         KKASSERT(i >= 0 && i < HAMMER2_BMAP_ELEMENTS);
 622
 623         /*
 624          * Optimize the buffer cache to avoid unnecessary read-before-write
 625          * operations.
 626          *
 627          * The device block size could be larger than the allocation size
 628          * so the actual bitmap test is somewhat more involved.  We have
 629          * to use a compatible buffer size for this operation.
 630          */
 631         if ((bmap->bitmapq[i] & bmmask) == 0 &&
 632             hammer2_devblksize(size) != size) {
 633                 size_t psize = hammer2_devblksize(size);
 634                 hammer2_off_t pmask = (hammer2_off_t)psize - 1;
 635                 int pbmradix = (hammer2_bitmap_t)2 <<
 636                                         (hammer2_devblkradix(radix) -
 637                                HAMMER2_FREEMAP_BLOCK_RADIX);
 638                 hammer2_bitmap_t pbmmask;
 639                 int pradix = hammer2_getradix(psize);
 640
 641                 pbmmask = (pbmradix == HAMMER2_BMAP_BITS_PER_ELEMENT) ?
 642                         HAMMER2_BMAP_ALLONES :
 643                         ((hammer2_bitmap_t)1 << pbmradix) - 1;
 644                 while ((pbmmask & bmmask) == 0)
 645                         pbmmask <<= pbmradix;
 646
 647 #if 0
 648                 kprintf("%016jx mask %016jx %016jx %016jx (%zd/%zd)\n",
 649                         *basep + offset, bmap->bitmapq[i],
 650                         pbmmask, bmmask, size, psize);
 651 #endif
 652
 653                 if ((bmap->bitmapq[i] & pbmmask) == 0) {
 654                         error = hammer2_io_newq(hmp,
 655                                                 (*basep + (offset & ~pmask)) |
 656                                                  pradix,
 657                                                 psize, &dio);
 658                         hammer2_io_bqrelse(&dio);
 659                 }
 660         }
 661
 662 #if 0
 663         /*
 664          * When initializing a new inode segment also attempt to initialize
 665          * an adjacent segment.  Be careful not to index beyond the array
 666          * bounds.
 667          *
 668          * We do this to try to localize inode accesses to improve
 669          * directory scan rates.  XXX doesn't improve scan rates.
 670          */
 671         if (size == HAMMER2_INODE_BYTES) {
 672                 if (n & 1) {
 673                         if (bmap[-1].radix == 0 && bmap[-1].avail)
 674                                 bmap[-1].radix = radix;
 675                 } else {
 676                         if (bmap[1].radix == 0 && bmap[1].avail)
 677                                 bmap[1].radix = radix;
 678                 }
 679         }
 680 #endif
 681         /*
 682          * Calculate the bitmap-granular change in bgsize for the volume
 683          * header.  We cannot use the fine-grained change here because
 684          * the bulkfree code can't undo it.  If the bitmap element is already
 685          * marked allocated it has already been accounted for.
 686          */
 687         if (radix < HAMMER2_FREEMAP_BLOCK_RADIX) {
 688                 if (bmap->bitmapq[i] & bmmask)
 689                         bgsize = 0;
 690                 else
 691                         bgsize = HAMMER2_FREEMAP_BLOCK_SIZE;
 692         } else {
 693                 bgsize = size;
 694         }
 695
 696         /*
 697          * Adjust the bitmap, set the class (it might have been 0),
 698          * and available bytes, update the allocation offset (*basep)
 699          * from the L0 base to the actual offset.
 700          *
 701          * avail must reflect the bitmap-granular availability.  The allocator
 702          * tests will also check the linear iterator.
 703          */
 704         bmap->bitmapq[i] |= bmmask;
 705         bmap->class = class;
 706         bmap->avail -= bgsize;
 707         *basep += offset;
 708
 709         /*
 710          * Adjust the volume header's allocator_free parameter.  This
 711          * parameter has to be fixed up by bulkfree which has no way to
 712          * figure out sub-16K chunking, so it must be adjusted by the
 713          * bitmap-granular size.
 714          */
 715         if (bgsize) {
 716                 hammer2_voldata_lock(hmp);
 717                 hammer2_voldata_modify(hmp);
 718                 hmp->voldata.allocator_free -= bgsize;
 719                 hammer2_voldata_unlock(hmp);
 720         }
 721
 722         return(0);
 723 }
 724
 725 static
 726 void
 727 hammer2_freemap_init(hammer2_trans_t *trans, hammer2_dev_t *hmp,
 728                      hammer2_key_t key, hammer2_chain_t *chain)
 729 {
 730         hammer2_off_t l1size;
 731         hammer2_off_t lokey;
 732         hammer2_off_t hikey;
 733         hammer2_bmap_data_t *bmap;
 734         int count;
 735
 736         l1size = H2FMSHIFT(HAMMER2_FREEMAP_LEVEL1_RADIX);
 737
 738         /*
 739          * Calculate the portion of the 2GB map that should be initialized
 740          * as free.  Portions below or after will be initialized as allocated.
 741          * SEGMASK-align the areas so we don't have to worry about sub-scans
 742          * or endianess when using memset.
 743          *
 744          * (1) Ensure that all statically allocated space from newfs_hammer2
 745          *     is marked allocated.
 746          *
 747          * (2) Ensure that the reserved area is marked allocated (typically
 748          *     the first 4MB of the 2GB area being represented).
 749          *
 750          * (3) Ensure that any trailing space at the end-of-volume is marked
 751          *     allocated.
 752          *
 753          * WARNING! It is possible for lokey to be larger than hikey if the
 754          *          entire 2GB segment is within the static allocation.
 755          */
 756         lokey = (hmp->voldata.allocator_beg + HAMMER2_SEGMASK64) &
 757                 ~HAMMER2_SEGMASK64;
 758
 759         if (lokey < H2FMBASE(key, HAMMER2_FREEMAP_LEVEL1_RADIX) +
 760                   HAMMER2_ZONE_SEG64) {
 761                 lokey = H2FMBASE(key, HAMMER2_FREEMAP_LEVEL1_RADIX) +
 762                         HAMMER2_ZONE_SEG64;
 763         }
 764
 765         hikey = key + H2FMSHIFT(HAMMER2_FREEMAP_LEVEL1_RADIX);
 766         if (hikey > hmp->voldata.volu_size) {
 767                 hikey = hmp->voldata.volu_size & ~HAMMER2_SEGMASK64;
 768         }
 769
 770         chain->bref.check.freemap.avail =
 771                 H2FMSHIFT(HAMMER2_FREEMAP_LEVEL1_RADIX);
 772         bmap = &chain->data->bmdata[0];
 773
 774         for (count = 0; count < HAMMER2_FREEMAP_COUNT; ++count) {
 775                 if (key < lokey || key >= hikey) {
 776                         memset(bmap->bitmapq, -1,
 777                                sizeof(bmap->bitmapq));
 778                         bmap->avail = 0;
 779                         bmap->linear = HAMMER2_SEGSIZE;
 780                         chain->bref.check.freemap.avail -=
 781                                 H2FMSHIFT(HAMMER2_FREEMAP_LEVEL0_RADIX);
 782                 } else {
 783                         bmap->avail = H2FMSHIFT(HAMMER2_FREEMAP_LEVEL0_RADIX);
 784                 }
 785                 key += H2FMSHIFT(HAMMER2_FREEMAP_LEVEL0_RADIX);
 786                 ++bmap;
 787         }
 788 }
 789
 790 /*
 791  * The current Level 1 freemap has been exhausted, iterate to the next
 792  * one, return ENOSPC if no freemaps remain.
 793  *
 794  * XXX this should rotate back to the beginning to handle freed-up space
 795  * XXX or use intermediate entries to locate free space. TODO
 796  */
 797 static int
 798 hammer2_freemap_iterate(hammer2_trans_t *trans, hammer2_chain_t **parentp,
 799                         hammer2_chain_t **chainp, hammer2_fiterate_t *iter)
 800 {
 801         hammer2_dev_t *hmp = (*parentp)->hmp;
 802
 803         iter->bnext &= ~(H2FMSHIFT(HAMMER2_FREEMAP_LEVEL1_RADIX) - 1);
 804         iter->bnext += H2FMSHIFT(HAMMER2_FREEMAP_LEVEL1_RADIX);
 805         if (iter->bnext >= hmp->voldata.volu_size) {
 806                 iter->bnext = 0;
 807                 if (++iter->loops == 2)
 808                         return (ENOSPC);
 809         }
 810         return(EAGAIN);
 811 }
 812
 813 /*
 814  * Adjust the bit-pattern for data in the freemap bitmap according to
 815  * (how).  This code is called from on-mount recovery to fixup (mark
 816  * as allocated) blocks whos freemap upates might not have been committed
 817  * in the last crash and is used by the bulk freemap scan to stage frees.
 818  *
 819  * XXX currently disabled when how == 0 (the normal real-time case).  At
 820  * the moment we depend on the bulk freescan to actually free blocks.  It
 821  * will still call this routine with a non-zero how to stage possible frees
 822  * and to do the actual free.
 823  */
 824 void
 825 hammer2_freemap_adjust(hammer2_trans_t *trans, hammer2_dev_t *hmp,
 826                        hammer2_blockref_t *bref, int how)
 827 {
 828         hammer2_off_t data_off = bref->data_off;
 829         hammer2_chain_t *chain;
 830         hammer2_chain_t *parent;
 831         hammer2_bmap_data_t *bmap;
 832         hammer2_key_t key;
 833         hammer2_key_t key_dummy;
 834         hammer2_off_t l0size;
 835         hammer2_off_t l1size;
 836         hammer2_off_t l1mask;
 837         hammer2_bitmap_t *bitmap;
 838         const hammer2_bitmap_t bmmask00 = 0;
 839         hammer2_bitmap_t bmmask01;
 840         hammer2_bitmap_t bmmask10;
 841         hammer2_bitmap_t bmmask11;
 842         size_t bytes;
 843         uint16_t class;
 844         int radix;
 845         int start;
 846         int count;
 847         int modified = 0;
 848         int cache_index = -1;
 849         int error;
 850
 851         KKASSERT(how == HAMMER2_FREEMAP_DORECOVER);
 852
 853         radix = (int)data_off & HAMMER2_OFF_MASK_RADIX;
 854         data_off &= ~HAMMER2_OFF_MASK_RADIX;
 855         KKASSERT(radix <= HAMMER2_RADIX_MAX);
 856
 857         bytes = (size_t)1 << radix;
 858         class = (bref->type << 8) | hammer2_devblkradix(radix);
 859
 860         /*
 861          * We can't adjust thre freemap for data allocations made by
 862          * newfs_hammer2.
 863          */
 864         if (data_off < hmp->voldata.allocator_beg)
 865                 return;
 866
 867         KKASSERT((data_off & HAMMER2_ZONE_MASK64) >= HAMMER2_ZONE_SEG);
 868
 869         /*
 870          * Lookup the level1 freemap chain.  The chain must exist.
 871          */
 872         key = H2FMBASE(data_off, HAMMER2_FREEMAP_LEVEL1_RADIX);
 873         l0size = H2FMSHIFT(HAMMER2_FREEMAP_LEVEL0_RADIX);
 874         l1size = H2FMSHIFT(HAMMER2_FREEMAP_LEVEL1_RADIX);
 875         l1mask = l1size - 1;
 876
 877         parent = &hmp->fchain;
 878         hammer2_chain_ref(parent);
 879         hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS);
 880
 881         chain = hammer2_chain_lookup(&parent, &key_dummy, key, key + l1mask,
 882                                      &cache_index,
 883                                      HAMMER2_LOOKUP_ALWAYS |
 884                                      HAMMER2_LOOKUP_MATCHIND);
 885
 886         /*
 887          * Stop early if we are trying to free something but no leaf exists.
 888          */
 889         if (chain == NULL && how != HAMMER2_FREEMAP_DORECOVER) {
 890                 kprintf("hammer2_freemap_adjust: %016jx: no chain\n",
 891                         (intmax_t)bref->data_off);
 892                 goto done;
 893         }
 894         if (chain->error) {
 895                 kprintf("hammer2_freemap_adjust: %016jx: error %s\n",
 896                         (intmax_t)bref->data_off,
 897                         hammer2_error_str(chain->error));
 898                 hammer2_chain_unlock(chain);
 899                 hammer2_chain_drop(chain);
 900                 chain = NULL;
 901                 goto done;
 902         }
 903
 904         /*
 905          * Create any missing leaf(s) if we are doing a recovery (marking
 906          * the block(s) as being allocated instead of being freed).  Be sure
 907          * to initialize the auxillary freemap tracking info in the
 908          * bref.check.freemap structure.
 909          */
 910         if (chain == NULL && how == HAMMER2_FREEMAP_DORECOVER) {
 911                 error = hammer2_chain_create(trans, &parent, &chain, hmp->spmp,
 912                                      key, HAMMER2_FREEMAP_LEVEL1_RADIX,
 913                                      HAMMER2_BREF_TYPE_FREEMAP_LEAF,
 914                                      HAMMER2_FREEMAP_LEVELN_PSIZE,
 915                                      0);
 916
 917                 if (hammer2_debug & 0x0040) {
 918                         kprintf("fixup create chain %p %016jx:%d\n",
 919                                 chain, chain->bref.key, chain->bref.keybits);
 920                 }
 921
 922                 if (error == 0) {
 923                         hammer2_chain_modify(trans, chain, 0);
 924                         bzero(&chain->data->bmdata[0],
 925                               HAMMER2_FREEMAP_LEVELN_PSIZE);
 926                         chain->bref.check.freemap.bigmask = (uint32_t)-1;
 927                         chain->bref.check.freemap.avail = l1size;
 928                         /* bref.methods should already be inherited */
 929
 930                         hammer2_freemap_init(trans, hmp, key, chain);
 931                 }
 932                 /* XXX handle error */
 933         }
 934
 935 #if FREEMAP_DEBUG
 936         kprintf("FREEMAP ADJUST TYPE %d %016jx/%d DATA_OFF=%016jx\n",
 937                 chain->bref.type, chain->bref.key,
 938                 chain->bref.keybits, chain->bref.data_off);
 939 #endif
 940
 941         /*
 942          * Calculate the bitmask (runs in 2-bit pairs).
 943          */
 944         start = ((int)(data_off >> HAMMER2_FREEMAP_BLOCK_RADIX) & 15) * 2;
 945         bmmask01 = (hammer2_bitmap_t)1 << start;
 946         bmmask10 = (hammer2_bitmap_t)2 << start;
 947         bmmask11 = (hammer2_bitmap_t)3 << start;
 948
 949         /*
 950          * Fixup the bitmap.  Partial blocks cannot be fully freed unless
 951          * a bulk scan is able to roll them up.
 952          */
 953         if (radix < HAMMER2_FREEMAP_BLOCK_RADIX) {
 954                 count = 1;
 955                 if (how == HAMMER2_FREEMAP_DOREALFREE)
 956                         how = HAMMER2_FREEMAP_DOMAYFREE;
 957         } else {
 958                 count = 1 << (radix - HAMMER2_FREEMAP_BLOCK_RADIX);
 959         }
 960
 961         /*
 962          * [re]load the bmap and bitmap pointers.  Each bmap entry covers
 963          * a 2MB swath.  The bmap itself (LEVEL1) covers 2GB.
 964          *
 965          * Be sure to reset the linear iterator to ensure that the adjustment
 966          * is not ignored.
 967          */
 968 again:
 969         bmap = &chain->data->bmdata[(int)(data_off >> HAMMER2_SEGRADIX) &
 970                                     (HAMMER2_FREEMAP_COUNT - 1)];
 971         bitmap = &bmap->bitmapq[(int)(data_off >> (HAMMER2_SEGRADIX - 3)) & 7];
 972
 973         if (modified)
 974                 bmap->linear = 0;
 975
 976         while (count) {
 977                 KKASSERT(bmmask11);
 978                 if (how == HAMMER2_FREEMAP_DORECOVER) {
 979                         /*
 980                          * Recovery request, mark as allocated.
 981                          */
 982                         if ((*bitmap & bmmask11) != bmmask11) {
 983                                 if (modified == 0) {
 984                                         hammer2_chain_modify(trans, chain, 0);
 985                                         modified = 1;
 986                                         goto again;
 987                                 }
 988                                 if ((*bitmap & bmmask11) == bmmask00) {
 989                                         bmap->avail -=
 990                                                 HAMMER2_FREEMAP_BLOCK_SIZE;
 991                                 }
 992                                 if (bmap->class == 0)
 993                                         bmap->class = class;
 994                                 *bitmap |= bmmask11;
 995                                 if (hammer2_debug & 0x0040) {
 996                                         kprintf("hammer2_freemap_recover: "
 997                                                 "fixup type=%02x "
 998                                                 "block=%016jx/%zd\n",
 999                                                 bref->type, data_off, bytes);
1000                                 }
1001                         } else {
1002                                 /*
1003                                 kprintf("hammer2_freemap_recover:  good "
1004                                         "type=%02x block=%016jx/%zd\n",
1005                                         bref->type, data_off, bytes);
1006                                 */
1007                         }
1008                 }
1009 #if 0
1010                 /*
1011                  * XXX this stuff doesn't work, avail is miscalculated and
1012                  * code 10 means something else now.
1013                  */
1014                 else if ((*bitmap & bmmask11) == bmmask11) {
1015                         /*
1016                          * Mayfree/Realfree request and bitmap is currently
1017                          * marked as being fully allocated.
1018                          */
1019                         if (!modified) {
1020                                 hammer2_chain_modify(trans, chain, 0);
1021                                 modified = 1;
1022                                 goto again;
1023                         }
1024                         if (how == HAMMER2_FREEMAP_DOREALFREE)
1025                                 *bitmap &= ~bmmask11;
1026                         else
1027                                 *bitmap = (*bitmap & ~bmmask11) | bmmask10;
1028                 } else if ((*bitmap & bmmask11) == bmmask10) {
1029                         /*
1030                          * Mayfree/Realfree request and bitmap is currently
1031                          * marked as being possibly freeable.
1032                          */
1033                         if (how == HAMMER2_FREEMAP_DOREALFREE) {
1034                                 if (!modified) {
1035                                         hammer2_chain_modify(trans, chain, 0);
1036                                         modified = 1;
1037                                         goto again;
1038                                 }
1039                                 *bitmap &= ~bmmask11;
1040                         }
1041                 } else {
1042                         /*
1043                          * 01 - Not implemented, currently illegal state
1044                          * 00 - Not allocated at all, illegal free.
1045                          */
1046                         panic("hammer2_freemap_adjust: "
1047                               "Illegal state %08x(%08x)",
1048                               *bitmap, *bitmap & bmmask11);
1049                 }
1050 #endif
1051                 --count;
1052                 bmmask01 <<= 2;
1053                 bmmask10 <<= 2;
1054                 bmmask11 <<= 2;
1055         }
1056 #if HAMMER2_BMAP_ELEMENTS != 8
1057 #error "hammer2_freemap.c: HAMMER2_BMAP_ELEMENTS expected to be 8"
1058 #endif
1059         if (how == HAMMER2_FREEMAP_DOREALFREE && modified) {
1060                 bmap->avail += 1 << radix;
1061                 KKASSERT(bmap->avail <= HAMMER2_SEGSIZE);
1062                 if (bmap->avail == HAMMER2_SEGSIZE &&
1063                     bmap->bitmapq[0] == 0 &&
1064                     bmap->bitmapq[1] == 0 &&
1065                     bmap->bitmapq[2] == 0 &&
1066                     bmap->bitmapq[3] == 0 &&
1067                     bmap->bitmapq[4] == 0 &&
1068                     bmap->bitmapq[5] == 0 &&
1069                     bmap->bitmapq[6] == 0 &&
1070                     bmap->bitmapq[7] == 0) {
1071                         key = H2FMBASE(data_off, HAMMER2_FREEMAP_LEVEL0_RADIX);
1072                         kprintf("Freeseg %016jx\n", (intmax_t)key);
1073                         bmap->class = 0;
1074                 }
1075         }
1076
1077         /*
1078          * chain->bref.check.freemap.bigmask (XXX)
1079          *
1080          * Setting bigmask is a hint to the allocation code that there might
1081          * be something allocatable.  We also set this in recovery... it
1082          * doesn't hurt and we might want to use the hint for other validation
1083          * operations later on.
1084          */
1085         if (modified)
1086                 chain->bref.check.freemap.bigmask |= 1 << radix;
1087
1088         hammer2_chain_unlock(chain);
1089         hammer2_chain_drop(chain);
1090 done:
1091         hammer2_chain_unlock(parent);
1092         hammer2_chain_drop(parent);
1093 }
1094
1095 /*
1096  * Validate the freemap, in three stages.
1097  *
1098  * stage-1      ALLOCATED     -> POSSIBLY FREE
1099  *              POSSIBLY FREE -> POSSIBLY FREE (type corrected)
1100  *
1101  *      This transitions bitmap entries from ALLOCATED to POSSIBLY FREE.
1102  *      The POSSIBLY FREE state does not mean that a block is actually free
1103  *      and may be transitioned back to ALLOCATED in stage-2.
1104  *
1105  *      This is typically done during normal filesystem operations when
1106  *      something is deleted or a block is replaced.
1107  *
1108  *      This is done by bulkfree in-bulk after a memory-bounded meta-data
1109  *      scan to try to determine what might be freeable.
1110  *
1111  *      This can be done unconditionally through a freemap scan when the
1112  *      intention is to brute-force recover the proper state of the freemap.
1113  *
1114  * stage-2      POSSIBLY FREE -> ALLOCATED      (scan metadata topology)
1115  *
1116  *      This is done by bulkfree during a meta-data scan to ensure that
1117  *      all blocks still actually allocated by the filesystem are marked
1118  *      as such.
1119  *
1120  *      NOTE! Live filesystem transitions to POSSIBLY FREE can occur while
1121  *            the bulkfree stage-2 and stage-3 is running.  The live filesystem
1122  *            will use the alternative POSSIBLY FREE type (2) to prevent
1123  *            stage-3 from improperly transitioning unvetted possibly-free
1124  *            blocks to FREE.
1125  *
1126  * stage-3      POSSIBLY FREE (type 1) -> FREE  (scan freemap)
1127  *
1128  *      This is done by bulkfree to finalize POSSIBLY FREE states.
1129  *
1130  */