fs/xfs/libxfs/xfs_refcount.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright (C) 2016 Oracle.  All Rights Reserved.
   4  * Author: Darrick J. Wong <darrick.wong@oracle.com>
   5  */
   6 #include "xfs.h"
   7 #include "xfs_fs.h"
   8 #include "xfs_shared.h"
   9 #include "xfs_format.h"
  10 #include "xfs_log_format.h"
  11 #include "xfs_trans_resv.h"
  12 #include "xfs_mount.h"
  13 #include "xfs_defer.h"
  14 #include "xfs_btree.h"
  15 #include "xfs_bmap.h"
  16 #include "xfs_refcount_btree.h"
  17 #include "xfs_alloc.h"
  18 #include "xfs_errortag.h"
  19 #include "xfs_error.h"
  20 #include "xfs_trace.h"
  21 #include "xfs_trans.h"
  22 #include "xfs_bit.h"
  23 #include "xfs_refcount.h"
  24 #include "xfs_rmap.h"
  25 #include "xfs_ag.h"
  26
  27 /* Allowable refcount adjustment amounts. */
  28 enum xfs_refc_adjust_op {
  29         XFS_REFCOUNT_ADJUST_INCREASE    = 1,
  30         XFS_REFCOUNT_ADJUST_DECREASE    = -1,
  31         XFS_REFCOUNT_ADJUST_COW_ALLOC   = 0,
  32         XFS_REFCOUNT_ADJUST_COW_FREE    = -1,
  33 };
  34
  35 STATIC int __xfs_refcount_cow_alloc(struct xfs_btree_cur *rcur,
  36                 xfs_agblock_t agbno, xfs_extlen_t aglen);
  37 STATIC int __xfs_refcount_cow_free(struct xfs_btree_cur *rcur,
  38                 xfs_agblock_t agbno, xfs_extlen_t aglen);
  39
  40 /*
  41  * Look up the first record less than or equal to [bno, len] in the btree
  42  * given by cur.
  43  */
  44 int
  45 xfs_refcount_lookup_le(
  46         struct xfs_btree_cur    *cur,
  47         xfs_agblock_t           bno,
  48         int                     *stat)
  49 {
  50         trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_ag.pag->pag_agno, bno,
  51                         XFS_LOOKUP_LE);
  52         cur->bc_rec.rc.rc_startblock = bno;
  53         cur->bc_rec.rc.rc_blockcount = 0;
  54         return xfs_btree_lookup(cur, XFS_LOOKUP_LE, stat);
  55 }
  56
  57 /*
  58  * Look up the first record greater than or equal to [bno, len] in the btree
  59  * given by cur.
  60  */
  61 int
  62 xfs_refcount_lookup_ge(
  63         struct xfs_btree_cur    *cur,
  64         xfs_agblock_t           bno,
  65         int                     *stat)
  66 {
  67         trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_ag.pag->pag_agno, bno,
  68                         XFS_LOOKUP_GE);
  69         cur->bc_rec.rc.rc_startblock = bno;
  70         cur->bc_rec.rc.rc_blockcount = 0;
  71         return xfs_btree_lookup(cur, XFS_LOOKUP_GE, stat);
  72 }
  73
  74 /*
  75  * Look up the first record equal to [bno, len] in the btree
  76  * given by cur.
  77  */
  78 int
  79 xfs_refcount_lookup_eq(
  80         struct xfs_btree_cur    *cur,
  81         xfs_agblock_t           bno,
  82         int                     *stat)
  83 {
  84         trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_ag.pag->pag_agno, bno,
  85                         XFS_LOOKUP_LE);
  86         cur->bc_rec.rc.rc_startblock = bno;
  87         cur->bc_rec.rc.rc_blockcount = 0;
  88         return xfs_btree_lookup(cur, XFS_LOOKUP_EQ, stat);
  89 }
  90
  91 /* Convert on-disk record to in-core format. */
  92 void
  93 xfs_refcount_btrec_to_irec(
  94         union xfs_btree_rec             *rec,
  95         struct xfs_refcount_irec        *irec)
  96 {
  97         irec->rc_startblock = be32_to_cpu(rec->refc.rc_startblock);
  98         irec->rc_blockcount = be32_to_cpu(rec->refc.rc_blockcount);
  99         irec->rc_refcount = be32_to_cpu(rec->refc.rc_refcount);
 100 }
 101
 102 /*
 103  * Get the data from the pointed-to record.
 104  */
 105 int
 106 xfs_refcount_get_rec(
 107         struct xfs_btree_cur            *cur,
 108         struct xfs_refcount_irec        *irec,
 109         int                             *stat)
 110 {
 111         struct xfs_mount                *mp = cur->bc_mp;
 112         xfs_agnumber_t                  agno = cur->bc_ag.pag->pag_agno;
 113         union xfs_btree_rec             *rec;
 114         int                             error;
 115         xfs_agblock_t                   realstart;
 116
 117         error = xfs_btree_get_rec(cur, &rec, stat);
 118         if (error || !*stat)
 119                 return error;
 120
 121         xfs_refcount_btrec_to_irec(rec, irec);
 122
 123         agno = cur->bc_ag.pag->pag_agno;
 124         if (irec->rc_blockcount == 0 || irec->rc_blockcount > MAXREFCEXTLEN)
 125                 goto out_bad_rec;
 126
 127         /* handle special COW-staging state */
 128         realstart = irec->rc_startblock;
 129         if (realstart & XFS_REFC_COW_START) {
 130                 if (irec->rc_refcount != 1)
 131                         goto out_bad_rec;
 132                 realstart &= ~XFS_REFC_COW_START;
 133         } else if (irec->rc_refcount < 2) {
 134                 goto out_bad_rec;
 135         }
 136
 137         /* check for valid extent range, including overflow */
 138         if (!xfs_verify_agbno(mp, agno, realstart))
 139                 goto out_bad_rec;
 140         if (realstart > realstart + irec->rc_blockcount)
 141                 goto out_bad_rec;
 142         if (!xfs_verify_agbno(mp, agno, realstart + irec->rc_blockcount - 1))
 143                 goto out_bad_rec;
 144
 145         if (irec->rc_refcount == 0 || irec->rc_refcount > MAXREFCOUNT)
 146                 goto out_bad_rec;
 147
 148         trace_xfs_refcount_get(cur->bc_mp, cur->bc_ag.pag->pag_agno, irec);
 149         return 0;
 150
 151 out_bad_rec:
 152         xfs_warn(mp,
 153                 "Refcount BTree record corruption in AG %d detected!", agno);
 154         xfs_warn(mp,
 155                 "Start block 0x%x, block count 0x%x, references 0x%x",
 156                 irec->rc_startblock, irec->rc_blockcount, irec->rc_refcount);
 157         return -EFSCORRUPTED;
 158 }
 159
 160 /*
 161  * Update the record referred to by cur to the value given
 162  * by [bno, len, refcount].
 163  * This either works (return 0) or gets an EFSCORRUPTED error.
 164  */
 165 STATIC int
 166 xfs_refcount_update(
 167         struct xfs_btree_cur            *cur,
 168         struct xfs_refcount_irec        *irec)
 169 {
 170         union xfs_btree_rec     rec;
 171         int                     error;
 172
 173         trace_xfs_refcount_update(cur->bc_mp, cur->bc_ag.pag->pag_agno, irec);
 174         rec.refc.rc_startblock = cpu_to_be32(irec->rc_startblock);
 175         rec.refc.rc_blockcount = cpu_to_be32(irec->rc_blockcount);
 176         rec.refc.rc_refcount = cpu_to_be32(irec->rc_refcount);
 177         error = xfs_btree_update(cur, &rec);
 178         if (error)
 179                 trace_xfs_refcount_update_error(cur->bc_mp,
 180                                 cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 181         return error;
 182 }
 183
 184 /*
 185  * Insert the record referred to by cur to the value given
 186  * by [bno, len, refcount].
 187  * This either works (return 0) or gets an EFSCORRUPTED error.
 188  */
 189 int
 190 xfs_refcount_insert(
 191         struct xfs_btree_cur            *cur,
 192         struct xfs_refcount_irec        *irec,
 193         int                             *i)
 194 {
 195         int                             error;
 196
 197         trace_xfs_refcount_insert(cur->bc_mp, cur->bc_ag.pag->pag_agno, irec);
 198         cur->bc_rec.rc.rc_startblock = irec->rc_startblock;
 199         cur->bc_rec.rc.rc_blockcount = irec->rc_blockcount;
 200         cur->bc_rec.rc.rc_refcount = irec->rc_refcount;
 201         error = xfs_btree_insert(cur, i);
 202         if (error)
 203                 goto out_error;
 204         if (XFS_IS_CORRUPT(cur->bc_mp, *i != 1)) {
 205                 error = -EFSCORRUPTED;
 206                 goto out_error;
 207         }
 208
 209 out_error:
 210         if (error)
 211                 trace_xfs_refcount_insert_error(cur->bc_mp,
 212                                 cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 213         return error;
 214 }
 215
 216 /*
 217  * Remove the record referred to by cur, then set the pointer to the spot
 218  * where the record could be re-inserted, in case we want to increment or
 219  * decrement the cursor.
 220  * This either works (return 0) or gets an EFSCORRUPTED error.
 221  */
 222 STATIC int
 223 xfs_refcount_delete(
 224         struct xfs_btree_cur    *cur,
 225         int                     *i)
 226 {
 227         struct xfs_refcount_irec        irec;
 228         int                     found_rec;
 229         int                     error;
 230
 231         error = xfs_refcount_get_rec(cur, &irec, &found_rec);
 232         if (error)
 233                 goto out_error;
 234         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 235                 error = -EFSCORRUPTED;
 236                 goto out_error;
 237         }
 238         trace_xfs_refcount_delete(cur->bc_mp, cur->bc_ag.pag->pag_agno, &irec);
 239         error = xfs_btree_delete(cur, i);
 240         if (XFS_IS_CORRUPT(cur->bc_mp, *i != 1)) {
 241                 error = -EFSCORRUPTED;
 242                 goto out_error;
 243         }
 244         if (error)
 245                 goto out_error;
 246         error = xfs_refcount_lookup_ge(cur, irec.rc_startblock, &found_rec);
 247 out_error:
 248         if (error)
 249                 trace_xfs_refcount_delete_error(cur->bc_mp,
 250                                 cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 251         return error;
 252 }
 253
 254 /*
 255  * Adjusting the Reference Count
 256  *
 257  * As stated elsewhere, the reference count btree (refcbt) stores
 258  * >1 reference counts for extents of physical blocks.  In this
 259  * operation, we're either raising or lowering the reference count of
 260  * some subrange stored in the tree:
 261  *
 262  *      <------ adjustment range ------>
 263  * ----+   +---+-----+ +--+--------+---------
 264  *  2  |   | 3 |  4  | |17|   55   |   10
 265  * ----+   +---+-----+ +--+--------+---------
 266  * X axis is physical blocks number;
 267  * reference counts are the numbers inside the rectangles
 268  *
 269  * The first thing we need to do is to ensure that there are no
 270  * refcount extents crossing either boundary of the range to be
 271  * adjusted.  For any extent that does cross a boundary, split it into
 272  * two extents so that we can increment the refcount of one of the
 273  * pieces later:
 274  *
 275  *      <------ adjustment range ------>
 276  * ----+   +---+-----+ +--+--------+----+----
 277  *  2  |   | 3 |  2  | |17|   55   | 10 | 10
 278  * ----+   +---+-----+ +--+--------+----+----
 279  *
 280  * For this next step, let's assume that all the physical blocks in
 281  * the adjustment range are mapped to a file and are therefore in use
 282  * at least once.  Therefore, we can infer that any gap in the
 283  * refcount tree within the adjustment range represents a physical
 284  * extent with refcount == 1:
 285  *
 286  *      <------ adjustment range ------>
 287  * ----+---+---+-----+-+--+--------+----+----
 288  *  2  |"1"| 3 |  2  |1|17|   55   | 10 | 10
 289  * ----+---+---+-----+-+--+--------+----+----
 290  *      ^
 291  *
 292  * For each extent that falls within the interval range, figure out
 293  * which extent is to the left or the right of that extent.  Now we
 294  * have a left, current, and right extent.  If the new reference count
 295  * of the center extent enables us to merge left, center, and right
 296  * into one record covering all three, do so.  If the center extent is
 297  * at the left end of the range, abuts the left extent, and its new
 298  * reference count matches the left extent's record, then merge them.
 299  * If the center extent is at the right end of the range, abuts the
 300  * right extent, and the reference counts match, merge those.  In the
 301  * example, we can left merge (assuming an increment operation):
 302  *
 303  *      <------ adjustment range ------>
 304  * --------+---+-----+-+--+--------+----+----
 305  *    2    | 3 |  2  |1|17|   55   | 10 | 10
 306  * --------+---+-----+-+--+--------+----+----
 307  *          ^
 308  *
 309  * For all other extents within the range, adjust the reference count
 310  * or delete it if the refcount falls below 2.  If we were
 311  * incrementing, the end result looks like this:
 312  *
 313  *      <------ adjustment range ------>
 314  * --------+---+-----+-+--+--------+----+----
 315  *    2    | 4 |  3  |2|18|   56   | 11 | 10
 316  * --------+---+-----+-+--+--------+----+----
 317  *
 318  * The result of a decrement operation looks as such:
 319  *
 320  *      <------ adjustment range ------>
 321  * ----+   +---+       +--+--------+----+----
 322  *  2  |   | 2 |       |16|   54   |  9 | 10
 323  * ----+   +---+       +--+--------+----+----
 324  *      DDDD    111111DD
 325  *
 326  * The blocks marked "D" are freed; the blocks marked "1" are only
 327  * referenced once and therefore the record is removed from the
 328  * refcount btree.
 329  */
 330
 331 /* Next block after this extent. */
 332 static inline xfs_agblock_t
 333 xfs_refc_next(
 334         struct xfs_refcount_irec        *rc)
 335 {
 336         return rc->rc_startblock + rc->rc_blockcount;
 337 }
 338
 339 /*
 340  * Split a refcount extent that crosses agbno.
 341  */
 342 STATIC int
 343 xfs_refcount_split_extent(
 344         struct xfs_btree_cur            *cur,
 345         xfs_agblock_t                   agbno,
 346         bool                            *shape_changed)
 347 {
 348         struct xfs_refcount_irec        rcext, tmp;
 349         int                             found_rec;
 350         int                             error;
 351
 352         *shape_changed = false;
 353         error = xfs_refcount_lookup_le(cur, agbno, &found_rec);
 354         if (error)
 355                 goto out_error;
 356         if (!found_rec)
 357                 return 0;
 358
 359         error = xfs_refcount_get_rec(cur, &rcext, &found_rec);
 360         if (error)
 361                 goto out_error;
 362         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 363                 error = -EFSCORRUPTED;
 364                 goto out_error;
 365         }
 366         if (rcext.rc_startblock == agbno || xfs_refc_next(&rcext) <= agbno)
 367                 return 0;
 368
 369         *shape_changed = true;
 370         trace_xfs_refcount_split_extent(cur->bc_mp, cur->bc_ag.pag->pag_agno,
 371                         &rcext, agbno);
 372
 373         /* Establish the right extent. */
 374         tmp = rcext;
 375         tmp.rc_startblock = agbno;
 376         tmp.rc_blockcount -= (agbno - rcext.rc_startblock);
 377         error = xfs_refcount_update(cur, &tmp);
 378         if (error)
 379                 goto out_error;
 380
 381         /* Insert the left extent. */
 382         tmp = rcext;
 383         tmp.rc_blockcount = agbno - rcext.rc_startblock;
 384         error = xfs_refcount_insert(cur, &tmp, &found_rec);
 385         if (error)
 386                 goto out_error;
 387         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 388                 error = -EFSCORRUPTED;
 389                 goto out_error;
 390         }
 391         return error;
 392
 393 out_error:
 394         trace_xfs_refcount_split_extent_error(cur->bc_mp,
 395                         cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 396         return error;
 397 }
 398
 399 /*
 400  * Merge the left, center, and right extents.
 401  */
 402 STATIC int
 403 xfs_refcount_merge_center_extents(
 404         struct xfs_btree_cur            *cur,
 405         struct xfs_refcount_irec        *left,
 406         struct xfs_refcount_irec        *center,
 407         struct xfs_refcount_irec        *right,
 408         unsigned long long              extlen,
 409         xfs_extlen_t                    *aglen)
 410 {
 411         int                             error;
 412         int                             found_rec;
 413
 414         trace_xfs_refcount_merge_center_extents(cur->bc_mp,
 415                         cur->bc_ag.pag->pag_agno, left, center, right);
 416
 417         /*
 418          * Make sure the center and right extents are not in the btree.
 419          * If the center extent was synthesized, the first delete call
 420          * removes the right extent and we skip the second deletion.
 421          * If center and right were in the btree, then the first delete
 422          * call removes the center and the second one removes the right
 423          * extent.
 424          */
 425         error = xfs_refcount_lookup_ge(cur, center->rc_startblock,
 426                         &found_rec);
 427         if (error)
 428                 goto out_error;
 429         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 430                 error = -EFSCORRUPTED;
 431                 goto out_error;
 432         }
 433
 434         error = xfs_refcount_delete(cur, &found_rec);
 435         if (error)
 436                 goto out_error;
 437         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 438                 error = -EFSCORRUPTED;
 439                 goto out_error;
 440         }
 441
 442         if (center->rc_refcount > 1) {
 443                 error = xfs_refcount_delete(cur, &found_rec);
 444                 if (error)
 445                         goto out_error;
 446                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 447                         error = -EFSCORRUPTED;
 448                         goto out_error;
 449                 }
 450         }
 451
 452         /* Enlarge the left extent. */
 453         error = xfs_refcount_lookup_le(cur, left->rc_startblock,
 454                         &found_rec);
 455         if (error)
 456                 goto out_error;
 457         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 458                 error = -EFSCORRUPTED;
 459                 goto out_error;
 460         }
 461
 462         left->rc_blockcount = extlen;
 463         error = xfs_refcount_update(cur, left);
 464         if (error)
 465                 goto out_error;
 466
 467         *aglen = 0;
 468         return error;
 469
 470 out_error:
 471         trace_xfs_refcount_merge_center_extents_error(cur->bc_mp,
 472                         cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 473         return error;
 474 }
 475
 476 /*
 477  * Merge with the left extent.
 478  */
 479 STATIC int
 480 xfs_refcount_merge_left_extent(
 481         struct xfs_btree_cur            *cur,
 482         struct xfs_refcount_irec        *left,
 483         struct xfs_refcount_irec        *cleft,
 484         xfs_agblock_t                   *agbno,
 485         xfs_extlen_t                    *aglen)
 486 {
 487         int                             error;
 488         int                             found_rec;
 489
 490         trace_xfs_refcount_merge_left_extent(cur->bc_mp,
 491                         cur->bc_ag.pag->pag_agno, left, cleft);
 492
 493         /* If the extent at agbno (cleft) wasn't synthesized, remove it. */
 494         if (cleft->rc_refcount > 1) {
 495                 error = xfs_refcount_lookup_le(cur, cleft->rc_startblock,
 496                                 &found_rec);
 497                 if (error)
 498                         goto out_error;
 499                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 500                         error = -EFSCORRUPTED;
 501                         goto out_error;
 502                 }
 503
 504                 error = xfs_refcount_delete(cur, &found_rec);
 505                 if (error)
 506                         goto out_error;
 507                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 508                         error = -EFSCORRUPTED;
 509                         goto out_error;
 510                 }
 511         }
 512
 513         /* Enlarge the left extent. */
 514         error = xfs_refcount_lookup_le(cur, left->rc_startblock,
 515                         &found_rec);
 516         if (error)
 517                 goto out_error;
 518         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 519                 error = -EFSCORRUPTED;
 520                 goto out_error;
 521         }
 522
 523         left->rc_blockcount += cleft->rc_blockcount;
 524         error = xfs_refcount_update(cur, left);
 525         if (error)
 526                 goto out_error;
 527
 528         *agbno += cleft->rc_blockcount;
 529         *aglen -= cleft->rc_blockcount;
 530         return error;
 531
 532 out_error:
 533         trace_xfs_refcount_merge_left_extent_error(cur->bc_mp,
 534                         cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 535         return error;
 536 }
 537
 538 /*
 539  * Merge with the right extent.
 540  */
 541 STATIC int
 542 xfs_refcount_merge_right_extent(
 543         struct xfs_btree_cur            *cur,
 544         struct xfs_refcount_irec        *right,
 545         struct xfs_refcount_irec        *cright,
 546         xfs_extlen_t                    *aglen)
 547 {
 548         int                             error;
 549         int                             found_rec;
 550
 551         trace_xfs_refcount_merge_right_extent(cur->bc_mp,
 552                         cur->bc_ag.pag->pag_agno, cright, right);
 553
 554         /*
 555          * If the extent ending at agbno+aglen (cright) wasn't synthesized,
 556          * remove it.
 557          */
 558         if (cright->rc_refcount > 1) {
 559                 error = xfs_refcount_lookup_le(cur, cright->rc_startblock,
 560                         &found_rec);
 561                 if (error)
 562                         goto out_error;
 563                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 564                         error = -EFSCORRUPTED;
 565                         goto out_error;
 566                 }
 567
 568                 error = xfs_refcount_delete(cur, &found_rec);
 569                 if (error)
 570                         goto out_error;
 571                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 572                         error = -EFSCORRUPTED;
 573                         goto out_error;
 574                 }
 575         }
 576
 577         /* Enlarge the right extent. */
 578         error = xfs_refcount_lookup_le(cur, right->rc_startblock,
 579                         &found_rec);
 580         if (error)
 581                 goto out_error;
 582         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 583                 error = -EFSCORRUPTED;
 584                 goto out_error;
 585         }
 586
 587         right->rc_startblock -= cright->rc_blockcount;
 588         right->rc_blockcount += cright->rc_blockcount;
 589         error = xfs_refcount_update(cur, right);
 590         if (error)
 591                 goto out_error;
 592
 593         *aglen -= cright->rc_blockcount;
 594         return error;
 595
 596 out_error:
 597         trace_xfs_refcount_merge_right_extent_error(cur->bc_mp,
 598                         cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 599         return error;
 600 }
 601
 602 #define XFS_FIND_RCEXT_SHARED   1
 603 #define XFS_FIND_RCEXT_COW      2
 604 /*
 605  * Find the left extent and the one after it (cleft).  This function assumes
 606  * that we've already split any extent crossing agbno.
 607  */
 608 STATIC int
 609 xfs_refcount_find_left_extents(
 610         struct xfs_btree_cur            *cur,
 611         struct xfs_refcount_irec        *left,
 612         struct xfs_refcount_irec        *cleft,
 613         xfs_agblock_t                   agbno,
 614         xfs_extlen_t                    aglen,
 615         int                             flags)
 616 {
 617         struct xfs_refcount_irec        tmp;
 618         int                             error;
 619         int                             found_rec;
 620
 621         left->rc_startblock = cleft->rc_startblock = NULLAGBLOCK;
 622         error = xfs_refcount_lookup_le(cur, agbno - 1, &found_rec);
 623         if (error)
 624                 goto out_error;
 625         if (!found_rec)
 626                 return 0;
 627
 628         error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 629         if (error)
 630                 goto out_error;
 631         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 632                 error = -EFSCORRUPTED;
 633                 goto out_error;
 634         }
 635
 636         if (xfs_refc_next(&tmp) != agbno)
 637                 return 0;
 638         if ((flags & XFS_FIND_RCEXT_SHARED) && tmp.rc_refcount < 2)
 639                 return 0;
 640         if ((flags & XFS_FIND_RCEXT_COW) && tmp.rc_refcount > 1)
 641                 return 0;
 642         /* We have a left extent; retrieve (or invent) the next right one */
 643         *left = tmp;
 644
 645         error = xfs_btree_increment(cur, 0, &found_rec);
 646         if (error)
 647                 goto out_error;
 648         if (found_rec) {
 649                 error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 650                 if (error)
 651                         goto out_error;
 652                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 653                         error = -EFSCORRUPTED;
 654                         goto out_error;
 655                 }
 656
 657                 /* if tmp starts at the end of our range, just use that */
 658                 if (tmp.rc_startblock == agbno)
 659                         *cleft = tmp;
 660                 else {
 661                         /*
 662                          * There's a gap in the refcntbt at the start of the
 663                          * range we're interested in (refcount == 1) so
 664                          * synthesize the implied extent and pass it back.
 665                          * We assume here that the agbno/aglen range was
 666                          * passed in from a data fork extent mapping and
 667                          * therefore is allocated to exactly one owner.
 668                          */
 669                         cleft->rc_startblock = agbno;
 670                         cleft->rc_blockcount = min(aglen,
 671                                         tmp.rc_startblock - agbno);
 672                         cleft->rc_refcount = 1;
 673                 }
 674         } else {
 675                 /*
 676                  * No extents, so pretend that there's one covering the whole
 677                  * range.
 678                  */
 679                 cleft->rc_startblock = agbno;
 680                 cleft->rc_blockcount = aglen;
 681                 cleft->rc_refcount = 1;
 682         }
 683         trace_xfs_refcount_find_left_extent(cur->bc_mp, cur->bc_ag.pag->pag_agno,
 684                         left, cleft, agbno);
 685         return error;
 686
 687 out_error:
 688         trace_xfs_refcount_find_left_extent_error(cur->bc_mp,
 689                         cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 690         return error;
 691 }
 692
 693 /*
 694  * Find the right extent and the one before it (cright).  This function
 695  * assumes that we've already split any extents crossing agbno + aglen.
 696  */
 697 STATIC int
 698 xfs_refcount_find_right_extents(
 699         struct xfs_btree_cur            *cur,
 700         struct xfs_refcount_irec        *right,
 701         struct xfs_refcount_irec        *cright,
 702         xfs_agblock_t                   agbno,
 703         xfs_extlen_t                    aglen,
 704         int                             flags)
 705 {
 706         struct xfs_refcount_irec        tmp;
 707         int                             error;
 708         int                             found_rec;
 709
 710         right->rc_startblock = cright->rc_startblock = NULLAGBLOCK;
 711         error = xfs_refcount_lookup_ge(cur, agbno + aglen, &found_rec);
 712         if (error)
 713                 goto out_error;
 714         if (!found_rec)
 715                 return 0;
 716
 717         error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 718         if (error)
 719                 goto out_error;
 720         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 721                 error = -EFSCORRUPTED;
 722                 goto out_error;
 723         }
 724
 725         if (tmp.rc_startblock != agbno + aglen)
 726                 return 0;
 727         if ((flags & XFS_FIND_RCEXT_SHARED) && tmp.rc_refcount < 2)
 728                 return 0;
 729         if ((flags & XFS_FIND_RCEXT_COW) && tmp.rc_refcount > 1)
 730                 return 0;
 731         /* We have a right extent; retrieve (or invent) the next left one */
 732         *right = tmp;
 733
 734         error = xfs_btree_decrement(cur, 0, &found_rec);
 735         if (error)
 736                 goto out_error;
 737         if (found_rec) {
 738                 error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 739                 if (error)
 740                         goto out_error;
 741                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 742                         error = -EFSCORRUPTED;
 743                         goto out_error;
 744                 }
 745
 746                 /* if tmp ends at the end of our range, just use that */
 747                 if (xfs_refc_next(&tmp) == agbno + aglen)
 748                         *cright = tmp;
 749                 else {
 750                         /*
 751                          * There's a gap in the refcntbt at the end of the
 752                          * range we're interested in (refcount == 1) so
 753                          * create the implied extent and pass it back.
 754                          * We assume here that the agbno/aglen range was
 755                          * passed in from a data fork extent mapping and
 756                          * therefore is allocated to exactly one owner.
 757                          */
 758                         cright->rc_startblock = max(agbno, xfs_refc_next(&tmp));
 759                         cright->rc_blockcount = right->rc_startblock -
 760                                         cright->rc_startblock;
 761                         cright->rc_refcount = 1;
 762                 }
 763         } else {
 764                 /*
 765                  * No extents, so pretend that there's one covering the whole
 766                  * range.
 767                  */
 768                 cright->rc_startblock = agbno;
 769                 cright->rc_blockcount = aglen;
 770                 cright->rc_refcount = 1;
 771         }
 772         trace_xfs_refcount_find_right_extent(cur->bc_mp, cur->bc_ag.pag->pag_agno,
 773                         cright, right, agbno + aglen);
 774         return error;
 775
 776 out_error:
 777         trace_xfs_refcount_find_right_extent_error(cur->bc_mp,
 778                         cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 779         return error;
 780 }
 781
 782 /* Is this extent valid? */
 783 static inline bool
 784 xfs_refc_valid(
 785         struct xfs_refcount_irec        *rc)
 786 {
 787         return rc->rc_startblock != NULLAGBLOCK;
 788 }
 789
 790 /*
 791  * Try to merge with any extents on the boundaries of the adjustment range.
 792  */
 793 STATIC int
 794 xfs_refcount_merge_extents(
 795         struct xfs_btree_cur    *cur,
 796         xfs_agblock_t           *agbno,
 797         xfs_extlen_t            *aglen,
 798         enum xfs_refc_adjust_op adjust,
 799         int                     flags,
 800         bool                    *shape_changed)
 801 {
 802         struct xfs_refcount_irec        left = {0}, cleft = {0};
 803         struct xfs_refcount_irec        cright = {0}, right = {0};
 804         int                             error;
 805         unsigned long long              ulen;
 806         bool                            cequal;
 807
 808         *shape_changed = false;
 809         /*
 810          * Find the extent just below agbno [left], just above agbno [cleft],
 811          * just below (agbno + aglen) [cright], and just above (agbno + aglen)
 812          * [right].
 813          */
 814         error = xfs_refcount_find_left_extents(cur, &left, &cleft, *agbno,
 815                         *aglen, flags);
 816         if (error)
 817                 return error;
 818         error = xfs_refcount_find_right_extents(cur, &right, &cright, *agbno,
 819                         *aglen, flags);
 820         if (error)
 821                 return error;
 822
 823         /* No left or right extent to merge; exit. */
 824         if (!xfs_refc_valid(&left) && !xfs_refc_valid(&right))
 825                 return 0;
 826
 827         cequal = (cleft.rc_startblock == cright.rc_startblock) &&
 828                  (cleft.rc_blockcount == cright.rc_blockcount);
 829
 830         /* Try to merge left, cleft, and right.  cleft must == cright. */
 831         ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount +
 832                         right.rc_blockcount;
 833         if (xfs_refc_valid(&left) && xfs_refc_valid(&right) &&
 834             xfs_refc_valid(&cleft) && xfs_refc_valid(&cright) && cequal &&
 835             left.rc_refcount == cleft.rc_refcount + adjust &&
 836             right.rc_refcount == cleft.rc_refcount + adjust &&
 837             ulen < MAXREFCEXTLEN) {
 838                 *shape_changed = true;
 839                 return xfs_refcount_merge_center_extents(cur, &left, &cleft,
 840                                 &right, ulen, aglen);
 841         }
 842
 843         /* Try to merge left and cleft. */
 844         ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount;
 845         if (xfs_refc_valid(&left) && xfs_refc_valid(&cleft) &&
 846             left.rc_refcount == cleft.rc_refcount + adjust &&
 847             ulen < MAXREFCEXTLEN) {
 848                 *shape_changed = true;
 849                 error = xfs_refcount_merge_left_extent(cur, &left, &cleft,
 850                                 agbno, aglen);
 851                 if (error)
 852                         return error;
 853
 854                 /*
 855                  * If we just merged left + cleft and cleft == cright,
 856                  * we no longer have a cright to merge with right.  We're done.
 857                  */
 858                 if (cequal)
 859                         return 0;
 860         }
 861
 862         /* Try to merge cright and right. */
 863         ulen = (unsigned long long)right.rc_blockcount + cright.rc_blockcount;
 864         if (xfs_refc_valid(&right) && xfs_refc_valid(&cright) &&
 865             right.rc_refcount == cright.rc_refcount + adjust &&
 866             ulen < MAXREFCEXTLEN) {
 867                 *shape_changed = true;
 868                 return xfs_refcount_merge_right_extent(cur, &right, &cright,
 869                                 aglen);
 870         }
 871
 872         return error;
 873 }
 874
 875 /*
 876  * XXX: This is a pretty hand-wavy estimate.  The penalty for guessing
 877  * true incorrectly is a shutdown FS; the penalty for guessing false
 878  * incorrectly is more transaction rolls than might be necessary.
 879  * Be conservative here.
 880  */
 881 static bool
 882 xfs_refcount_still_have_space(
 883         struct xfs_btree_cur            *cur)
 884 {
 885         unsigned long                   overhead;
 886
 887         overhead = cur->bc_ag.refc.shape_changes *
 888                         xfs_allocfree_log_count(cur->bc_mp, 1);
 889         overhead *= cur->bc_mp->m_sb.sb_blocksize;
 890
 891         /*
 892          * Only allow 2 refcount extent updates per transaction if the
 893          * refcount continue update "error" has been injected.
 894          */
 895         if (cur->bc_ag.refc.nr_ops > 2 &&
 896             XFS_TEST_ERROR(false, cur->bc_mp,
 897                         XFS_ERRTAG_REFCOUNT_CONTINUE_UPDATE))
 898                 return false;
 899
 900         if (cur->bc_ag.refc.nr_ops == 0)
 901                 return true;
 902         else if (overhead > cur->bc_tp->t_log_res)
 903                 return false;
 904         return  cur->bc_tp->t_log_res - overhead >
 905                 cur->bc_ag.refc.nr_ops * XFS_REFCOUNT_ITEM_OVERHEAD;
 906 }
 907
 908 /*
 909  * Adjust the refcounts of middle extents.  At this point we should have
 910  * split extents that crossed the adjustment range; merged with adjacent
 911  * extents; and updated agbno/aglen to reflect the merges.  Therefore,
 912  * all we have to do is update the extents inside [agbno, agbno + aglen].
 913  */
 914 STATIC int
 915 xfs_refcount_adjust_extents(
 916         struct xfs_btree_cur    *cur,
 917         xfs_agblock_t           *agbno,
 918         xfs_extlen_t            *aglen,
 919         enum xfs_refc_adjust_op adj,
 920         struct xfs_owner_info   *oinfo)
 921 {
 922         struct xfs_refcount_irec        ext, tmp;
 923         int                             error;
 924         int                             found_rec, found_tmp;
 925         xfs_fsblock_t                   fsbno;
 926
 927         /* Merging did all the work already. */
 928         if (*aglen == 0)
 929                 return 0;
 930
 931         error = xfs_refcount_lookup_ge(cur, *agbno, &found_rec);
 932         if (error)
 933                 goto out_error;
 934
 935         while (*aglen > 0 && xfs_refcount_still_have_space(cur)) {
 936                 error = xfs_refcount_get_rec(cur, &ext, &found_rec);
 937                 if (error)
 938                         goto out_error;
 939                 if (!found_rec) {
 940                         ext.rc_startblock = cur->bc_mp->m_sb.sb_agblocks;
 941                         ext.rc_blockcount = 0;
 942                         ext.rc_refcount = 0;
 943                 }
 944
 945                 /*
 946                  * Deal with a hole in the refcount tree; if a file maps to
 947                  * these blocks and there's no refcountbt record, pretend that
 948                  * there is one with refcount == 1.
 949                  */
 950                 if (ext.rc_startblock != *agbno) {
 951                         tmp.rc_startblock = *agbno;
 952                         tmp.rc_blockcount = min(*aglen,
 953                                         ext.rc_startblock - *agbno);
 954                         tmp.rc_refcount = 1 + adj;
 955                         trace_xfs_refcount_modify_extent(cur->bc_mp,
 956                                         cur->bc_ag.pag->pag_agno, &tmp);
 957
 958                         /*
 959                          * Either cover the hole (increment) or
 960                          * delete the range (decrement).
 961                          */
 962                         if (tmp.rc_refcount) {
 963                                 error = xfs_refcount_insert(cur, &tmp,
 964                                                 &found_tmp);
 965                                 if (error)
 966                                         goto out_error;
 967                                 if (XFS_IS_CORRUPT(cur->bc_mp,
 968                                                    found_tmp != 1)) {
 969                                         error = -EFSCORRUPTED;
 970                                         goto out_error;
 971                                 }
 972                                 cur->bc_ag.refc.nr_ops++;
 973                         } else {
 974                                 fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
 975                                                 cur->bc_ag.pag->pag_agno,
 976                                                 tmp.rc_startblock);
 977                                 xfs_bmap_add_free(cur->bc_tp, fsbno,
 978                                                   tmp.rc_blockcount, oinfo);
 979                         }
 980
 981                         (*agbno) += tmp.rc_blockcount;
 982                         (*aglen) -= tmp.rc_blockcount;
 983
 984                         error = xfs_refcount_lookup_ge(cur, *agbno,
 985                                         &found_rec);
 986                         if (error)
 987                                 goto out_error;
 988                 }
 989
 990                 /* Stop if there's nothing left to modify */
 991                 if (*aglen == 0 || !xfs_refcount_still_have_space(cur))
 992                         break;
 993
 994                 /*
 995                  * Adjust the reference count and either update the tree
 996                  * (incr) or free the blocks (decr).
 997                  */
 998                 if (ext.rc_refcount == MAXREFCOUNT)
 999                         goto skip;
1000                 ext.rc_refcount += adj;
1001                 trace_xfs_refcount_modify_extent(cur->bc_mp,
1002                                 cur->bc_ag.pag->pag_agno, &ext);
1003                 if (ext.rc_refcount > 1) {
1004                         error = xfs_refcount_update(cur, &ext);
1005                         if (error)
1006                                 goto out_error;
1007                         cur->bc_ag.refc.nr_ops++;
1008                 } else if (ext.rc_refcount == 1) {
1009                         error = xfs_refcount_delete(cur, &found_rec);
1010                         if (error)
1011                                 goto out_error;
1012                         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
1013                                 error = -EFSCORRUPTED;
1014                                 goto out_error;
1015                         }
1016                         cur->bc_ag.refc.nr_ops++;
1017                         goto advloop;
1018                 } else {
1019                         fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
1020                                         cur->bc_ag.pag->pag_agno,
1021                                         ext.rc_startblock);
1022                         xfs_bmap_add_free(cur->bc_tp, fsbno, ext.rc_blockcount,
1023                                           oinfo);
1024                 }
1025
1026 skip:
1027                 error = xfs_btree_increment(cur, 0, &found_rec);
1028                 if (error)
1029                         goto out_error;
1030
1031 advloop:
1032                 (*agbno) += ext.rc_blockcount;
1033                 (*aglen) -= ext.rc_blockcount;
1034         }
1035
1036         return error;
1037 out_error:
1038         trace_xfs_refcount_modify_extent_error(cur->bc_mp,
1039                         cur->bc_ag.pag->pag_agno, error, _RET_IP_);
1040         return error;
1041 }
1042
1043 /* Adjust the reference count of a range of AG blocks. */
1044 STATIC int
1045 xfs_refcount_adjust(
1046         struct xfs_btree_cur    *cur,
1047         xfs_agblock_t           agbno,
1048         xfs_extlen_t            aglen,
1049         xfs_agblock_t           *new_agbno,
1050         xfs_extlen_t            *new_aglen,
1051         enum xfs_refc_adjust_op adj,
1052         struct xfs_owner_info   *oinfo)
1053 {
1054         bool                    shape_changed;
1055         int                     shape_changes = 0;
1056         int                     error;
1057
1058         *new_agbno = agbno;
1059         *new_aglen = aglen;
1060         if (adj == XFS_REFCOUNT_ADJUST_INCREASE)
1061                 trace_xfs_refcount_increase(cur->bc_mp, cur->bc_ag.pag->pag_agno,
1062                                 agbno, aglen);
1063         else
1064                 trace_xfs_refcount_decrease(cur->bc_mp, cur->bc_ag.pag->pag_agno,
1065                                 agbno, aglen);
1066
1067         /*
1068          * Ensure that no rcextents cross the boundary of the adjustment range.
1069          */
1070         error = xfs_refcount_split_extent(cur, agbno, &shape_changed);
1071         if (error)
1072                 goto out_error;
1073         if (shape_changed)
1074                 shape_changes++;
1075
1076         error = xfs_refcount_split_extent(cur, agbno + aglen, &shape_changed);
1077         if (error)
1078                 goto out_error;
1079         if (shape_changed)
1080                 shape_changes++;
1081
1082         /*
1083          * Try to merge with the left or right extents of the range.
1084          */
1085         error = xfs_refcount_merge_extents(cur, new_agbno, new_aglen, adj,
1086                         XFS_FIND_RCEXT_SHARED, &shape_changed);
1087         if (error)
1088                 goto out_error;
1089         if (shape_changed)
1090                 shape_changes++;
1091         if (shape_changes)
1092                 cur->bc_ag.refc.shape_changes++;
1093
1094         /* Now that we've taken care of the ends, adjust the middle extents */
1095         error = xfs_refcount_adjust_extents(cur, new_agbno, new_aglen,
1096                         adj, oinfo);
1097         if (error)
1098                 goto out_error;
1099
1100         return 0;
1101
1102 out_error:
1103         trace_xfs_refcount_adjust_error(cur->bc_mp, cur->bc_ag.pag->pag_agno,
1104                         error, _RET_IP_);
1105         return error;
1106 }
1107
1108 /* Clean up after calling xfs_refcount_finish_one. */
1109 void
1110 xfs_refcount_finish_one_cleanup(
1111         struct xfs_trans        *tp,
1112         struct xfs_btree_cur    *rcur,
1113         int                     error)
1114 {
1115         struct xfs_buf          *agbp;
1116
1117         if (rcur == NULL)
1118                 return;
1119         agbp = rcur->bc_ag.agbp;
1120         xfs_btree_del_cursor(rcur, error);
1121         if (error)
1122                 xfs_trans_brelse(tp, agbp);
1123 }
1124
1125 /*
1126  * Process one of the deferred refcount operations.  We pass back the
1127  * btree cursor to maintain our lock on the btree between calls.
1128  * This saves time and eliminates a buffer deadlock between the
1129  * superblock and the AGF because we'll always grab them in the same
1130  * order.
1131  */
1132 int
1133 xfs_refcount_finish_one(
1134         struct xfs_trans                *tp,
1135         enum xfs_refcount_intent_type   type,
1136         xfs_fsblock_t                   startblock,
1137         xfs_extlen_t                    blockcount,
1138         xfs_fsblock_t                   *new_fsb,
1139         xfs_extlen_t                    *new_len,
1140         struct xfs_btree_cur            **pcur)
1141 {
1142         struct xfs_mount                *mp = tp->t_mountp;
1143         struct xfs_btree_cur            *rcur;
1144         struct xfs_buf                  *agbp = NULL;
1145         int                             error = 0;
1146         xfs_agblock_t                   bno;
1147         xfs_agblock_t                   new_agbno;
1148         unsigned long                   nr_ops = 0;
1149         int                             shape_changes = 0;
1150         struct xfs_perag                *pag;
1151
1152         pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, startblock));
1153         bno = XFS_FSB_TO_AGBNO(mp, startblock);
1154
1155         trace_xfs_refcount_deferred(mp, XFS_FSB_TO_AGNO(mp, startblock),
1156                         type, XFS_FSB_TO_AGBNO(mp, startblock),
1157                         blockcount);
1158
1159         if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_REFCOUNT_FINISH_ONE)) {
1160                 error = -EIO;
1161                 goto out_drop;
1162         }
1163
1164         /*
1165          * If we haven't gotten a cursor or the cursor AG doesn't match
1166          * the startblock, get one now.
1167          */
1168         rcur = *pcur;
1169         if (rcur != NULL && rcur->bc_ag.pag != pag) {
1170                 nr_ops = rcur->bc_ag.refc.nr_ops;
1171                 shape_changes = rcur->bc_ag.refc.shape_changes;
1172                 xfs_refcount_finish_one_cleanup(tp, rcur, 0);
1173                 rcur = NULL;
1174                 *pcur = NULL;
1175         }
1176         if (rcur == NULL) {
1177                 error = xfs_alloc_read_agf(tp->t_mountp, tp, pag->pag_agno,
1178                                 XFS_ALLOC_FLAG_FREEING, &agbp);
1179                 if (error)
1180                         goto out_drop;
1181
1182                 rcur = xfs_refcountbt_init_cursor(mp, tp, agbp, pag);
1183                 rcur->bc_ag.refc.nr_ops = nr_ops;
1184                 rcur->bc_ag.refc.shape_changes = shape_changes;
1185         }
1186         *pcur = rcur;
1187
1188         switch (type) {
1189         case XFS_REFCOUNT_INCREASE:
1190                 error = xfs_refcount_adjust(rcur, bno, blockcount, &new_agbno,
1191                         new_len, XFS_REFCOUNT_ADJUST_INCREASE, NULL);
1192                 *new_fsb = XFS_AGB_TO_FSB(mp, pag->pag_agno, new_agbno);
1193                 break;
1194         case XFS_REFCOUNT_DECREASE:
1195                 error = xfs_refcount_adjust(rcur, bno, blockcount, &new_agbno,
1196                         new_len, XFS_REFCOUNT_ADJUST_DECREASE, NULL);
1197                 *new_fsb = XFS_AGB_TO_FSB(mp, pag->pag_agno, new_agbno);
1198                 break;
1199         case XFS_REFCOUNT_ALLOC_COW:
1200                 *new_fsb = startblock + blockcount;
1201                 *new_len = 0;
1202                 error = __xfs_refcount_cow_alloc(rcur, bno, blockcount);
1203                 break;
1204         case XFS_REFCOUNT_FREE_COW:
1205                 *new_fsb = startblock + blockcount;
1206                 *new_len = 0;
1207                 error = __xfs_refcount_cow_free(rcur, bno, blockcount);
1208                 break;
1209         default:
1210                 ASSERT(0);
1211                 error = -EFSCORRUPTED;
1212         }
1213         if (!error && *new_len > 0)
1214                 trace_xfs_refcount_finish_one_leftover(mp, pag->pag_agno, type,
1215                                 bno, blockcount, new_agbno, *new_len);
1216 out_drop:
1217         xfs_perag_put(pag);
1218         return error;
1219 }
1220
1221 /*
1222  * Record a refcount intent for later processing.
1223  */
1224 static void
1225 __xfs_refcount_add(
1226         struct xfs_trans                *tp,
1227         enum xfs_refcount_intent_type   type,
1228         xfs_fsblock_t                   startblock,
1229         xfs_extlen_t                    blockcount)
1230 {
1231         struct xfs_refcount_intent      *ri;
1232
1233         trace_xfs_refcount_defer(tp->t_mountp,
1234                         XFS_FSB_TO_AGNO(tp->t_mountp, startblock),
1235                         type, XFS_FSB_TO_AGBNO(tp->t_mountp, startblock),
1236                         blockcount);
1237
1238         ri = kmem_alloc(sizeof(struct xfs_refcount_intent),
1239                         KM_NOFS);
1240         INIT_LIST_HEAD(&ri->ri_list);
1241         ri->ri_type = type;
1242         ri->ri_startblock = startblock;
1243         ri->ri_blockcount = blockcount;
1244
1245         xfs_defer_add(tp, XFS_DEFER_OPS_TYPE_REFCOUNT, &ri->ri_list);
1246 }
1247
1248 /*
1249  * Increase the reference count of the blocks backing a file's extent.
1250  */
1251 void
1252 xfs_refcount_increase_extent(
1253         struct xfs_trans                *tp,
1254         struct xfs_bmbt_irec            *PREV)
1255 {
1256         if (!xfs_sb_version_hasreflink(&tp->t_mountp->m_sb))
1257                 return;
1258
1259         __xfs_refcount_add(tp, XFS_REFCOUNT_INCREASE, PREV->br_startblock,
1260                         PREV->br_blockcount);
1261 }
1262
1263 /*
1264  * Decrease the reference count of the blocks backing a file's extent.
1265  */
1266 void
1267 xfs_refcount_decrease_extent(
1268         struct xfs_trans                *tp,
1269         struct xfs_bmbt_irec            *PREV)
1270 {
1271         if (!xfs_sb_version_hasreflink(&tp->t_mountp->m_sb))
1272                 return;
1273
1274         __xfs_refcount_add(tp, XFS_REFCOUNT_DECREASE, PREV->br_startblock,
1275                         PREV->br_blockcount);
1276 }
1277
1278 /*
1279  * Given an AG extent, find the lowest-numbered run of shared blocks
1280  * within that range and return the range in fbno/flen.  If
1281  * find_end_of_shared is set, return the longest contiguous extent of
1282  * shared blocks; if not, just return the first extent we find.  If no
1283  * shared blocks are found, fbno and flen will be set to NULLAGBLOCK
1284  * and 0, respectively.
1285  */
1286 int
1287 xfs_refcount_find_shared(
1288         struct xfs_btree_cur            *cur,
1289         xfs_agblock_t                   agbno,
1290         xfs_extlen_t                    aglen,
1291         xfs_agblock_t                   *fbno,
1292         xfs_extlen_t                    *flen,
1293         bool                            find_end_of_shared)
1294 {
1295         struct xfs_refcount_irec        tmp;
1296         int                             i;
1297         int                             have;
1298         int                             error;
1299
1300         trace_xfs_refcount_find_shared(cur->bc_mp, cur->bc_ag.pag->pag_agno,
1301                         agbno, aglen);
1302
1303         /* By default, skip the whole range */
1304         *fbno = NULLAGBLOCK;
1305         *flen = 0;
1306
1307         /* Try to find a refcount extent that crosses the start */
1308         error = xfs_refcount_lookup_le(cur, agbno, &have);
1309         if (error)
1310                 goto out_error;
1311         if (!have) {
1312                 /* No left extent, look at the next one */
1313                 error = xfs_btree_increment(cur, 0, &have);
1314                 if (error)
1315                         goto out_error;
1316                 if (!have)
1317                         goto done;
1318         }
1319         error = xfs_refcount_get_rec(cur, &tmp, &i);
1320         if (error)
1321                 goto out_error;
1322         if (XFS_IS_CORRUPT(cur->bc_mp, i != 1)) {
1323                 error = -EFSCORRUPTED;
1324                 goto out_error;
1325         }
1326
1327         /* If the extent ends before the start, look at the next one */
1328         if (tmp.rc_startblock + tmp.rc_blockcount <= agbno) {
1329                 error = xfs_btree_increment(cur, 0, &have);
1330                 if (error)
1331                         goto out_error;
1332                 if (!have)
1333                         goto done;
1334                 error = xfs_refcount_get_rec(cur, &tmp, &i);
1335                 if (error)
1336                         goto out_error;
1337                 if (XFS_IS_CORRUPT(cur->bc_mp, i != 1)) {
1338                         error = -EFSCORRUPTED;
1339                         goto out_error;
1340                 }
1341         }
1342
1343         /* If the extent starts after the range we want, bail out */
1344         if (tmp.rc_startblock >= agbno + aglen)
1345                 goto done;
1346
1347         /* We found the start of a shared extent! */
1348         if (tmp.rc_startblock < agbno) {
1349                 tmp.rc_blockcount -= (agbno - tmp.rc_startblock);
1350                 tmp.rc_startblock = agbno;
1351         }
1352
1353         *fbno = tmp.rc_startblock;
1354         *flen = min(tmp.rc_blockcount, agbno + aglen - *fbno);
1355         if (!find_end_of_shared)
1356                 goto done;
1357
1358         /* Otherwise, find the end of this shared extent */
1359         while (*fbno + *flen < agbno + aglen) {
1360                 error = xfs_btree_increment(cur, 0, &have);
1361                 if (error)
1362                         goto out_error;
1363                 if (!have)
1364                         break;
1365                 error = xfs_refcount_get_rec(cur, &tmp, &i);
1366                 if (error)
1367                         goto out_error;
1368                 if (XFS_IS_CORRUPT(cur->bc_mp, i != 1)) {
1369                         error = -EFSCORRUPTED;
1370                         goto out_error;
1371                 }
1372                 if (tmp.rc_startblock >= agbno + aglen ||
1373                     tmp.rc_startblock != *fbno + *flen)
1374                         break;
1375                 *flen = min(*flen + tmp.rc_blockcount, agbno + aglen - *fbno);
1376         }
1377
1378 done:
1379         trace_xfs_refcount_find_shared_result(cur->bc_mp,
1380                         cur->bc_ag.pag->pag_agno, *fbno, *flen);
1381
1382 out_error:
1383         if (error)
1384                 trace_xfs_refcount_find_shared_error(cur->bc_mp,
1385                                 cur->bc_ag.pag->pag_agno, error, _RET_IP_);
1386         return error;
1387 }
1388
1389 /*
1390  * Recovering CoW Blocks After a Crash
1391  *
1392  * Due to the way that the copy on write mechanism works, there's a window of
1393  * opportunity in which we can lose track of allocated blocks during a crash.
1394  * Because CoW uses delayed allocation in the in-core CoW fork, writeback
1395  * causes blocks to be allocated and stored in the CoW fork.  The blocks are
1396  * no longer in the free space btree but are not otherwise recorded anywhere
1397  * until the write completes and the blocks are mapped into the file.  A crash
1398  * in between allocation and remapping results in the replacement blocks being
1399  * lost.  This situation is exacerbated by the CoW extent size hint because
1400  * allocations can hang around for long time.
1401  *
1402  * However, there is a place where we can record these allocations before they
1403  * become mappings -- the reference count btree.  The btree does not record
1404  * extents with refcount == 1, so we can record allocations with a refcount of
1405  * 1.  Blocks being used for CoW writeout cannot be shared, so there should be
1406  * no conflict with shared block records.  These mappings should be created
1407  * when we allocate blocks to the CoW fork and deleted when they're removed
1408  * from the CoW fork.
1409  *
1410  * Minor nit: records for in-progress CoW allocations and records for shared
1411  * extents must never be merged, to preserve the property that (except for CoW
1412  * allocations) there are no refcount btree entries with refcount == 1.  The
1413  * only time this could potentially happen is when unsharing a block that's
1414  * adjacent to CoW allocations, so we must be careful to avoid this.
1415  *
1416  * At mount time we recover lost CoW allocations by searching the refcount
1417  * btree for these refcount == 1 mappings.  These represent CoW allocations
1418  * that were in progress at the time the filesystem went down, so we can free
1419  * them to get the space back.
1420  *
1421  * This mechanism is superior to creating EFIs for unmapped CoW extents for
1422  * several reasons -- first, EFIs pin the tail of the log and would have to be
1423  * periodically relogged to avoid filling up the log.  Second, CoW completions
1424  * will have to file an EFD and create new EFIs for whatever remains in the
1425  * CoW fork; this partially takes care of (1) but extent-size reservations
1426  * will have to periodically relog even if there's no writeout in progress.
1427  * This can happen if the CoW extent size hint is set, which you really want.
1428  * Third, EFIs cannot currently be automatically relogged into newer
1429  * transactions to advance the log tail.  Fourth, stuffing the log full of
1430  * EFIs places an upper bound on the number of CoW allocations that can be
1431  * held filesystem-wide at any given time.  Recording them in the refcount
1432  * btree doesn't require us to maintain any state in memory and doesn't pin
1433  * the log.
1434  */
1435 /*
1436  * Adjust the refcounts of CoW allocations.  These allocations are "magic"
1437  * in that they're not referenced anywhere else in the filesystem, so we
1438  * stash them in the refcount btree with a refcount of 1 until either file
1439  * remapping (or CoW cancellation) happens.
1440  */
1441 STATIC int
1442 xfs_refcount_adjust_cow_extents(
1443         struct xfs_btree_cur    *cur,
1444         xfs_agblock_t           agbno,
1445         xfs_extlen_t            aglen,
1446         enum xfs_refc_adjust_op adj)
1447 {
1448         struct xfs_refcount_irec        ext, tmp;
1449         int                             error;
1450         int                             found_rec, found_tmp;
1451
1452         if (aglen == 0)
1453                 return 0;
1454
1455         /* Find any overlapping refcount records */
1456         error = xfs_refcount_lookup_ge(cur, agbno, &found_rec);
1457         if (error)
1458                 goto out_error;
1459         error = xfs_refcount_get_rec(cur, &ext, &found_rec);
1460         if (error)
1461                 goto out_error;
1462         if (!found_rec) {
1463                 ext.rc_startblock = cur->bc_mp->m_sb.sb_agblocks +
1464                                 XFS_REFC_COW_START;
1465                 ext.rc_blockcount = 0;
1466                 ext.rc_refcount = 0;
1467         }
1468
1469         switch (adj) {
1470         case XFS_REFCOUNT_ADJUST_COW_ALLOC:
1471                 /* Adding a CoW reservation, there should be nothing here. */
1472                 if (XFS_IS_CORRUPT(cur->bc_mp,
1473                                    agbno + aglen > ext.rc_startblock)) {
1474                         error = -EFSCORRUPTED;
1475                         goto out_error;
1476                 }
1477
1478                 tmp.rc_startblock = agbno;
1479                 tmp.rc_blockcount = aglen;
1480                 tmp.rc_refcount = 1;
1481                 trace_xfs_refcount_modify_extent(cur->bc_mp,
1482                                 cur->bc_ag.pag->pag_agno, &tmp);
1483
1484                 error = xfs_refcount_insert(cur, &tmp,
1485                                 &found_tmp);
1486                 if (error)
1487                         goto out_error;
1488                 if (XFS_IS_CORRUPT(cur->bc_mp, found_tmp != 1)) {
1489                         error = -EFSCORRUPTED;
1490                         goto out_error;
1491                 }
1492                 break;
1493         case XFS_REFCOUNT_ADJUST_COW_FREE:
1494                 /* Removing a CoW reservation, there should be one extent. */
1495                 if (XFS_IS_CORRUPT(cur->bc_mp, ext.rc_startblock != agbno)) {
1496                         error = -EFSCORRUPTED;
1497                         goto out_error;
1498                 }
1499                 if (XFS_IS_CORRUPT(cur->bc_mp, ext.rc_blockcount != aglen)) {
1500                         error = -EFSCORRUPTED;
1501                         goto out_error;
1502                 }
1503                 if (XFS_IS_CORRUPT(cur->bc_mp, ext.rc_refcount != 1)) {
1504                         error = -EFSCORRUPTED;
1505                         goto out_error;
1506                 }
1507
1508                 ext.rc_refcount = 0;
1509                 trace_xfs_refcount_modify_extent(cur->bc_mp,
1510                                 cur->bc_ag.pag->pag_agno, &ext);
1511                 error = xfs_refcount_delete(cur, &found_rec);
1512                 if (error)
1513                         goto out_error;
1514                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
1515                         error = -EFSCORRUPTED;
1516                         goto out_error;
1517                 }
1518                 break;
1519         default:
1520                 ASSERT(0);
1521         }
1522
1523         return error;
1524 out_error:
1525         trace_xfs_refcount_modify_extent_error(cur->bc_mp,
1526                         cur->bc_ag.pag->pag_agno, error, _RET_IP_);
1527         return error;
1528 }
1529
1530 /*
1531  * Add or remove refcount btree entries for CoW reservations.
1532  */
1533 STATIC int
1534 xfs_refcount_adjust_cow(
1535         struct xfs_btree_cur    *cur,
1536         xfs_agblock_t           agbno,
1537         xfs_extlen_t            aglen,
1538         enum xfs_refc_adjust_op adj)
1539 {
1540         bool                    shape_changed;
1541         int                     error;
1542
1543         agbno += XFS_REFC_COW_START;
1544
1545         /*
1546          * Ensure that no rcextents cross the boundary of the adjustment range.
1547          */
1548         error = xfs_refcount_split_extent(cur, agbno, &shape_changed);
1549         if (error)
1550                 goto out_error;
1551
1552         error = xfs_refcount_split_extent(cur, agbno + aglen, &shape_changed);
1553         if (error)
1554                 goto out_error;
1555
1556         /*
1557          * Try to merge with the left or right extents of the range.
1558          */
1559         error = xfs_refcount_merge_extents(cur, &agbno, &aglen, adj,
1560                         XFS_FIND_RCEXT_COW, &shape_changed);
1561         if (error)
1562                 goto out_error;
1563
1564         /* Now that we've taken care of the ends, adjust the middle extents */
1565         error = xfs_refcount_adjust_cow_extents(cur, agbno, aglen, adj);
1566         if (error)
1567                 goto out_error;
1568
1569         return 0;
1570
1571 out_error:
1572         trace_xfs_refcount_adjust_cow_error(cur->bc_mp, cur->bc_ag.pag->pag_agno,
1573                         error, _RET_IP_);
1574         return error;
1575 }
1576
1577 /*
1578  * Record a CoW allocation in the refcount btree.
1579  */
1580 STATIC int
1581 __xfs_refcount_cow_alloc(
1582         struct xfs_btree_cur    *rcur,
1583         xfs_agblock_t           agbno,
1584         xfs_extlen_t            aglen)
1585 {
1586         trace_xfs_refcount_cow_increase(rcur->bc_mp, rcur->bc_ag.pag->pag_agno,
1587                         agbno, aglen);
1588
1589         /* Add refcount btree reservation */
1590         return xfs_refcount_adjust_cow(rcur, agbno, aglen,
1591                         XFS_REFCOUNT_ADJUST_COW_ALLOC);
1592 }
1593
1594 /*
1595  * Remove a CoW allocation from the refcount btree.
1596  */
1597 STATIC int
1598 __xfs_refcount_cow_free(
1599         struct xfs_btree_cur    *rcur,
1600         xfs_agblock_t           agbno,
1601         xfs_extlen_t            aglen)
1602 {
1603         trace_xfs_refcount_cow_decrease(rcur->bc_mp, rcur->bc_ag.pag->pag_agno,
1604                         agbno, aglen);
1605
1606         /* Remove refcount btree reservation */
1607         return xfs_refcount_adjust_cow(rcur, agbno, aglen,
1608                         XFS_REFCOUNT_ADJUST_COW_FREE);
1609 }
1610
1611 /* Record a CoW staging extent in the refcount btree. */
1612 void
1613 xfs_refcount_alloc_cow_extent(
1614         struct xfs_trans                *tp,
1615         xfs_fsblock_t                   fsb,
1616         xfs_extlen_t                    len)
1617 {
1618         struct xfs_mount                *mp = tp->t_mountp;
1619
1620         if (!xfs_sb_version_hasreflink(&mp->m_sb))
1621                 return;
1622
1623         __xfs_refcount_add(tp, XFS_REFCOUNT_ALLOC_COW, fsb, len);
1624
1625         /* Add rmap entry */
1626         xfs_rmap_alloc_extent(tp, XFS_FSB_TO_AGNO(mp, fsb),
1627                         XFS_FSB_TO_AGBNO(mp, fsb), len, XFS_RMAP_OWN_COW);
1628 }
1629
1630 /* Forget a CoW staging event in the refcount btree. */
1631 void
1632 xfs_refcount_free_cow_extent(
1633         struct xfs_trans                *tp,
1634         xfs_fsblock_t                   fsb,
1635         xfs_extlen_t                    len)
1636 {
1637         struct xfs_mount                *mp = tp->t_mountp;
1638
1639         if (!xfs_sb_version_hasreflink(&mp->m_sb))
1640                 return;
1641
1642         /* Remove rmap entry */
1643         xfs_rmap_free_extent(tp, XFS_FSB_TO_AGNO(mp, fsb),
1644                         XFS_FSB_TO_AGBNO(mp, fsb), len, XFS_RMAP_OWN_COW);
1645         __xfs_refcount_add(tp, XFS_REFCOUNT_FREE_COW, fsb, len);
1646 }
1647
1648 struct xfs_refcount_recovery {
1649         struct list_head                rr_list;
1650         struct xfs_refcount_irec        rr_rrec;
1651 };
1652
1653 /* Stuff an extent on the recovery list. */
1654 STATIC int
1655 xfs_refcount_recover_extent(
1656         struct xfs_btree_cur            *cur,
1657         union xfs_btree_rec             *rec,
1658         void                            *priv)
1659 {
1660         struct list_head                *debris = priv;
1661         struct xfs_refcount_recovery    *rr;
1662
1663         if (XFS_IS_CORRUPT(cur->bc_mp,
1664                            be32_to_cpu(rec->refc.rc_refcount) != 1))
1665                 return -EFSCORRUPTED;
1666
1667         rr = kmem_alloc(sizeof(struct xfs_refcount_recovery), 0);
1668         xfs_refcount_btrec_to_irec(rec, &rr->rr_rrec);
1669         list_add_tail(&rr->rr_list, debris);
1670
1671         return 0;
1672 }
1673
1674 /* Find and remove leftover CoW reservations. */
1675 int
1676 xfs_refcount_recover_cow_leftovers(
1677         struct xfs_mount                *mp,
1678         struct xfs_perag                *pag)
1679 {
1680         struct xfs_trans                *tp;
1681         struct xfs_btree_cur            *cur;
1682         struct xfs_buf                  *agbp;
1683         struct xfs_refcount_recovery    *rr, *n;
1684         struct list_head                debris;
1685         union xfs_btree_irec            low;
1686         union xfs_btree_irec            high;
1687         xfs_fsblock_t                   fsb;
1688         xfs_agblock_t                   agbno;
1689         int                             error;
1690
1691         if (mp->m_sb.sb_agblocks >= XFS_REFC_COW_START)
1692                 return -EOPNOTSUPP;
1693
1694         INIT_LIST_HEAD(&debris);
1695
1696         /*
1697          * In this first part, we use an empty transaction to gather up
1698          * all the leftover CoW extents so that we can subsequently
1699          * delete them.  The empty transaction is used to avoid
1700          * a buffer lock deadlock if there happens to be a loop in the
1701          * refcountbt because we're allowed to re-grab a buffer that is
1702          * already attached to our transaction.  When we're done
1703          * recording the CoW debris we cancel the (empty) transaction
1704          * and everything goes away cleanly.
1705          */
1706         error = xfs_trans_alloc_empty(mp, &tp);
1707         if (error)
1708                 return error;
1709
1710         error = xfs_alloc_read_agf(mp, tp, pag->pag_agno, 0, &agbp);
1711         if (error)
1712                 goto out_trans;
1713         cur = xfs_refcountbt_init_cursor(mp, tp, agbp, pag);
1714
1715         /* Find all the leftover CoW staging extents. */
1716         memset(&low, 0, sizeof(low));
1717         memset(&high, 0, sizeof(high));
1718         low.rc.rc_startblock = XFS_REFC_COW_START;
1719         high.rc.rc_startblock = -1U;
1720         error = xfs_btree_query_range(cur, &low, &high,
1721                         xfs_refcount_recover_extent, &debris);
1722         xfs_btree_del_cursor(cur, error);
1723         xfs_trans_brelse(tp, agbp);
1724         xfs_trans_cancel(tp);
1725         if (error)
1726                 goto out_free;
1727
1728         /* Now iterate the list to free the leftovers */
1729         list_for_each_entry_safe(rr, n, &debris, rr_list) {
1730                 /* Set up transaction. */
1731                 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1732                 if (error)
1733                         goto out_free;
1734
1735                 trace_xfs_refcount_recover_extent(mp, pag->pag_agno,
1736                                 &rr->rr_rrec);
1737
1738                 /* Free the orphan record */
1739                 agbno = rr->rr_rrec.rc_startblock - XFS_REFC_COW_START;
1740                 fsb = XFS_AGB_TO_FSB(mp, pag->pag_agno, agbno);
1741                 xfs_refcount_free_cow_extent(tp, fsb,
1742                                 rr->rr_rrec.rc_blockcount);
1743
1744                 /* Free the block. */
1745                 xfs_bmap_add_free(tp, fsb, rr->rr_rrec.rc_blockcount, NULL);
1746
1747                 error = xfs_trans_commit(tp);
1748                 if (error)
1749                         goto out_free;
1750
1751                 list_del(&rr->rr_list);
1752                 kmem_free(rr);
1753         }
1754
1755         return error;
1756 out_trans:
1757         xfs_trans_cancel(tp);
1758 out_free:
1759         /* Free the leftover list */
1760         list_for_each_entry_safe(rr, n, &debris, rr_list) {
1761                 list_del(&rr->rr_list);
1762                 kmem_free(rr);
1763         }
1764         return error;
1765 }
1766
1767 /* Is there a record covering a given extent? */
1768 int
1769 xfs_refcount_has_record(
1770         struct xfs_btree_cur    *cur,
1771         xfs_agblock_t           bno,
1772         xfs_extlen_t            len,
1773         bool                    *exists)
1774 {
1775         union xfs_btree_irec    low;
1776         union xfs_btree_irec    high;
1777
1778         memset(&low, 0, sizeof(low));
1779         low.rc.rc_startblock = bno;
1780         memset(&high, 0xFF, sizeof(high));
1781         high.rc.rc_startblock = bno + len - 1;
1782
1783         return xfs_btree_has_record(cur, &low, &high, exists);
1784 }