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
  26 /* Allowable refcount adjustment amounts. */
  27 enum xfs_refc_adjust_op {
  28         XFS_REFCOUNT_ADJUST_INCREASE    = 1,
  29         XFS_REFCOUNT_ADJUST_DECREASE    = -1,
  30         XFS_REFCOUNT_ADJUST_COW_ALLOC   = 0,
  31         XFS_REFCOUNT_ADJUST_COW_FREE    = -1,
  32 };
  33
  34 STATIC int __xfs_refcount_cow_alloc(struct xfs_btree_cur *rcur,
  35                 xfs_agblock_t agbno, xfs_extlen_t aglen);
  36 STATIC int __xfs_refcount_cow_free(struct xfs_btree_cur *rcur,
  37                 xfs_agblock_t agbno, xfs_extlen_t aglen);
  38
  39 /*
  40  * Look up the first record less than or equal to [bno, len] in the btree
  41  * given by cur.
  42  */
  43 int
  44 xfs_refcount_lookup_le(
  45         struct xfs_btree_cur    *cur,
  46         xfs_agblock_t           bno,
  47         int                     *stat)
  48 {
  49         trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_ag.agno, bno,
  50                         XFS_LOOKUP_LE);
  51         cur->bc_rec.rc.rc_startblock = bno;
  52         cur->bc_rec.rc.rc_blockcount = 0;
  53         return xfs_btree_lookup(cur, XFS_LOOKUP_LE, stat);
  54 }
  55
  56 /*
  57  * Look up the first record greater than or equal to [bno, len] in the btree
  58  * given by cur.
  59  */
  60 int
  61 xfs_refcount_lookup_ge(
  62         struct xfs_btree_cur    *cur,
  63         xfs_agblock_t           bno,
  64         int                     *stat)
  65 {
  66         trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_ag.agno, bno,
  67                         XFS_LOOKUP_GE);
  68         cur->bc_rec.rc.rc_startblock = bno;
  69         cur->bc_rec.rc.rc_blockcount = 0;
  70         return xfs_btree_lookup(cur, XFS_LOOKUP_GE, stat);
  71 }
  72
  73 /*
  74  * Look up the first record equal to [bno, len] in the btree
  75  * given by cur.
  76  */
  77 int
  78 xfs_refcount_lookup_eq(
  79         struct xfs_btree_cur    *cur,
  80         xfs_agblock_t           bno,
  81         int                     *stat)
  82 {
  83         trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_ag.agno, bno,
  84                         XFS_LOOKUP_LE);
  85         cur->bc_rec.rc.rc_startblock = bno;
  86         cur->bc_rec.rc.rc_blockcount = 0;
  87         return xfs_btree_lookup(cur, XFS_LOOKUP_EQ, stat);
  88 }
  89
  90 /* Convert on-disk record to in-core format. */
  91 void
  92 xfs_refcount_btrec_to_irec(
  93         union xfs_btree_rec             *rec,
  94         struct xfs_refcount_irec        *irec)
  95 {
  96         irec->rc_startblock = be32_to_cpu(rec->refc.rc_startblock);
  97         irec->rc_blockcount = be32_to_cpu(rec->refc.rc_blockcount);
  98         irec->rc_refcount = be32_to_cpu(rec->refc.rc_refcount);
  99 }
 100
 101 /*
 102  * Get the data from the pointed-to record.
 103  */
 104 int
 105 xfs_refcount_get_rec(
 106         struct xfs_btree_cur            *cur,
 107         struct xfs_refcount_irec        *irec,
 108         int                             *stat)
 109 {
 110         struct xfs_mount                *mp = cur->bc_mp;
 111         xfs_agnumber_t                  agno = cur->bc_ag.agno;
 112         union xfs_btree_rec             *rec;
 113         int                             error;
 114         xfs_agblock_t                   realstart;
 115
 116         error = xfs_btree_get_rec(cur, &rec, stat);
 117         if (error || !*stat)
 118                 return error;
 119
 120         xfs_refcount_btrec_to_irec(rec, irec);
 121
 122         agno = cur->bc_ag.agno;
 123         if (irec->rc_blockcount == 0 || irec->rc_blockcount > MAXREFCEXTLEN)
 124                 goto out_bad_rec;
 125
 126         /* handle special COW-staging state */
 127         realstart = irec->rc_startblock;
 128         if (realstart & XFS_REFC_COW_START) {
 129                 if (irec->rc_refcount != 1)
 130                         goto out_bad_rec;
 131                 realstart &= ~XFS_REFC_COW_START;
 132         } else if (irec->rc_refcount < 2) {
 133                 goto out_bad_rec;
 134         }
 135
 136         /* check for valid extent range, including overflow */
 137         if (!xfs_verify_agbno(mp, agno, realstart))
 138                 goto out_bad_rec;
 139         if (realstart > realstart + irec->rc_blockcount)
 140                 goto out_bad_rec;
 141         if (!xfs_verify_agbno(mp, agno, realstart + irec->rc_blockcount - 1))
 142                 goto out_bad_rec;
 143
 144         if (irec->rc_refcount == 0 || irec->rc_refcount > MAXREFCOUNT)
 145                 goto out_bad_rec;
 146
 147         trace_xfs_refcount_get(cur->bc_mp, cur->bc_ag.agno, irec);
 148         return 0;
 149
 150 out_bad_rec:
 151         xfs_warn(mp,
 152                 "Refcount BTree record corruption in AG %d detected!", agno);
 153         xfs_warn(mp,
 154                 "Start block 0x%x, block count 0x%x, references 0x%x",
 155                 irec->rc_startblock, irec->rc_blockcount, irec->rc_refcount);
 156         return -EFSCORRUPTED;
 157 }
 158
 159 /*
 160  * Update the record referred to by cur to the value given
 161  * by [bno, len, refcount].
 162  * This either works (return 0) or gets an EFSCORRUPTED error.
 163  */
 164 STATIC int
 165 xfs_refcount_update(
 166         struct xfs_btree_cur            *cur,
 167         struct xfs_refcount_irec        *irec)
 168 {
 169         union xfs_btree_rec     rec;
 170         int                     error;
 171
 172         trace_xfs_refcount_update(cur->bc_mp, cur->bc_ag.agno, irec);
 173         rec.refc.rc_startblock = cpu_to_be32(irec->rc_startblock);
 174         rec.refc.rc_blockcount = cpu_to_be32(irec->rc_blockcount);
 175         rec.refc.rc_refcount = cpu_to_be32(irec->rc_refcount);
 176         error = xfs_btree_update(cur, &rec);
 177         if (error)
 178                 trace_xfs_refcount_update_error(cur->bc_mp,
 179                                 cur->bc_ag.agno, error, _RET_IP_);
 180         return error;
 181 }
 182
 183 /*
 184  * Insert the record referred to by cur to the value given
 185  * by [bno, len, refcount].
 186  * This either works (return 0) or gets an EFSCORRUPTED error.
 187  */
 188 int
 189 xfs_refcount_insert(
 190         struct xfs_btree_cur            *cur,
 191         struct xfs_refcount_irec        *irec,
 192         int                             *i)
 193 {
 194         int                             error;
 195
 196         trace_xfs_refcount_insert(cur->bc_mp, cur->bc_ag.agno, irec);
 197         cur->bc_rec.rc.rc_startblock = irec->rc_startblock;
 198         cur->bc_rec.rc.rc_blockcount = irec->rc_blockcount;
 199         cur->bc_rec.rc.rc_refcount = irec->rc_refcount;
 200         error = xfs_btree_insert(cur, i);
 201         if (error)
 202                 goto out_error;
 203         if (XFS_IS_CORRUPT(cur->bc_mp, *i != 1)) {
 204                 error = -EFSCORRUPTED;
 205                 goto out_error;
 206         }
 207
 208 out_error:
 209         if (error)
 210                 trace_xfs_refcount_insert_error(cur->bc_mp,
 211                                 cur->bc_ag.agno, error, _RET_IP_);
 212         return error;
 213 }
 214
 215 /*
 216  * Remove the record referred to by cur, then set the pointer to the spot
 217  * where the record could be re-inserted, in case we want to increment or
 218  * decrement the cursor.
 219  * This either works (return 0) or gets an EFSCORRUPTED error.
 220  */
 221 STATIC int
 222 xfs_refcount_delete(
 223         struct xfs_btree_cur    *cur,
 224         int                     *i)
 225 {
 226         struct xfs_refcount_irec        irec;
 227         int                     found_rec;
 228         int                     error;
 229
 230         error = xfs_refcount_get_rec(cur, &irec, &found_rec);
 231         if (error)
 232                 goto out_error;
 233         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 234                 error = -EFSCORRUPTED;
 235                 goto out_error;
 236         }
 237         trace_xfs_refcount_delete(cur->bc_mp, cur->bc_ag.agno, &irec);
 238         error = xfs_btree_delete(cur, i);
 239         if (XFS_IS_CORRUPT(cur->bc_mp, *i != 1)) {
 240                 error = -EFSCORRUPTED;
 241                 goto out_error;
 242         }
 243         if (error)
 244                 goto out_error;
 245         error = xfs_refcount_lookup_ge(cur, irec.rc_startblock, &found_rec);
 246 out_error:
 247         if (error)
 248                 trace_xfs_refcount_delete_error(cur->bc_mp,
 249                                 cur->bc_ag.agno, error, _RET_IP_);
 250         return error;
 251 }
 252
 253 /*
 254  * Adjusting the Reference Count
 255  *
 256  * As stated elsewhere, the reference count btree (refcbt) stores
 257  * >1 reference counts for extents of physical blocks.  In this
 258  * operation, we're either raising or lowering the reference count of
 259  * some subrange stored in the tree:
 260  *
 261  *      <------ adjustment range ------>
 262  * ----+   +---+-----+ +--+--------+---------
 263  *  2  |   | 3 |  4  | |17|   55   |   10
 264  * ----+   +---+-----+ +--+--------+---------
 265  * X axis is physical blocks number;
 266  * reference counts are the numbers inside the rectangles
 267  *
 268  * The first thing we need to do is to ensure that there are no
 269  * refcount extents crossing either boundary of the range to be
 270  * adjusted.  For any extent that does cross a boundary, split it into
 271  * two extents so that we can increment the refcount of one of the
 272  * pieces later:
 273  *
 274  *      <------ adjustment range ------>
 275  * ----+   +---+-----+ +--+--------+----+----
 276  *  2  |   | 3 |  2  | |17|   55   | 10 | 10
 277  * ----+   +---+-----+ +--+--------+----+----
 278  *
 279  * For this next step, let's assume that all the physical blocks in
 280  * the adjustment range are mapped to a file and are therefore in use
 281  * at least once.  Therefore, we can infer that any gap in the
 282  * refcount tree within the adjustment range represents a physical
 283  * extent with refcount == 1:
 284  *
 285  *      <------ adjustment range ------>
 286  * ----+---+---+-----+-+--+--------+----+----
 287  *  2  |"1"| 3 |  2  |1|17|   55   | 10 | 10
 288  * ----+---+---+-----+-+--+--------+----+----
 289  *      ^
 290  *
 291  * For each extent that falls within the interval range, figure out
 292  * which extent is to the left or the right of that extent.  Now we
 293  * have a left, current, and right extent.  If the new reference count
 294  * of the center extent enables us to merge left, center, and right
 295  * into one record covering all three, do so.  If the center extent is
 296  * at the left end of the range, abuts the left extent, and its new
 297  * reference count matches the left extent's record, then merge them.
 298  * If the center extent is at the right end of the range, abuts the
 299  * right extent, and the reference counts match, merge those.  In the
 300  * example, we can left merge (assuming an increment operation):
 301  *
 302  *      <------ adjustment range ------>
 303  * --------+---+-----+-+--+--------+----+----
 304  *    2    | 3 |  2  |1|17|   55   | 10 | 10
 305  * --------+---+-----+-+--+--------+----+----
 306  *          ^
 307  *
 308  * For all other extents within the range, adjust the reference count
 309  * or delete it if the refcount falls below 2.  If we were
 310  * incrementing, the end result looks like this:
 311  *
 312  *      <------ adjustment range ------>
 313  * --------+---+-----+-+--+--------+----+----
 314  *    2    | 4 |  3  |2|18|   56   | 11 | 10
 315  * --------+---+-----+-+--+--------+----+----
 316  *
 317  * The result of a decrement operation looks as such:
 318  *
 319  *      <------ adjustment range ------>
 320  * ----+   +---+       +--+--------+----+----
 321  *  2  |   | 2 |       |16|   54   |  9 | 10
 322  * ----+   +---+       +--+--------+----+----
 323  *      DDDD    111111DD
 324  *
 325  * The blocks marked "D" are freed; the blocks marked "1" are only
 326  * referenced once and therefore the record is removed from the
 327  * refcount btree.
 328  */
 329
 330 /* Next block after this extent. */
 331 static inline xfs_agblock_t
 332 xfs_refc_next(
 333         struct xfs_refcount_irec        *rc)
 334 {
 335         return rc->rc_startblock + rc->rc_blockcount;
 336 }
 337
 338 /*
 339  * Split a refcount extent that crosses agbno.
 340  */
 341 STATIC int
 342 xfs_refcount_split_extent(
 343         struct xfs_btree_cur            *cur,
 344         xfs_agblock_t                   agbno,
 345         bool                            *shape_changed)
 346 {
 347         struct xfs_refcount_irec        rcext, tmp;
 348         int                             found_rec;
 349         int                             error;
 350
 351         *shape_changed = false;
 352         error = xfs_refcount_lookup_le(cur, agbno, &found_rec);
 353         if (error)
 354                 goto out_error;
 355         if (!found_rec)
 356                 return 0;
 357
 358         error = xfs_refcount_get_rec(cur, &rcext, &found_rec);
 359         if (error)
 360                 goto out_error;
 361         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 362                 error = -EFSCORRUPTED;
 363                 goto out_error;
 364         }
 365         if (rcext.rc_startblock == agbno || xfs_refc_next(&rcext) <= agbno)
 366                 return 0;
 367
 368         *shape_changed = true;
 369         trace_xfs_refcount_split_extent(cur->bc_mp, cur->bc_ag.agno,
 370                         &rcext, agbno);
 371
 372         /* Establish the right extent. */
 373         tmp = rcext;
 374         tmp.rc_startblock = agbno;
 375         tmp.rc_blockcount -= (agbno - rcext.rc_startblock);
 376         error = xfs_refcount_update(cur, &tmp);
 377         if (error)
 378                 goto out_error;
 379
 380         /* Insert the left extent. */
 381         tmp = rcext;
 382         tmp.rc_blockcount = agbno - rcext.rc_startblock;
 383         error = xfs_refcount_insert(cur, &tmp, &found_rec);
 384         if (error)
 385                 goto out_error;
 386         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 387                 error = -EFSCORRUPTED;
 388                 goto out_error;
 389         }
 390         return error;
 391
 392 out_error:
 393         trace_xfs_refcount_split_extent_error(cur->bc_mp,
 394                         cur->bc_ag.agno, error, _RET_IP_);
 395         return error;
 396 }
 397
 398 /*
 399  * Merge the left, center, and right extents.
 400  */
 401 STATIC int
 402 xfs_refcount_merge_center_extents(
 403         struct xfs_btree_cur            *cur,
 404         struct xfs_refcount_irec        *left,
 405         struct xfs_refcount_irec        *center,
 406         struct xfs_refcount_irec        *right,
 407         unsigned long long              extlen,
 408         xfs_extlen_t                    *aglen)
 409 {
 410         int                             error;
 411         int                             found_rec;
 412
 413         trace_xfs_refcount_merge_center_extents(cur->bc_mp,
 414                         cur->bc_ag.agno, left, center, right);
 415
 416         /*
 417          * Make sure the center and right extents are not in the btree.
 418          * If the center extent was synthesized, the first delete call
 419          * removes the right extent and we skip the second deletion.
 420          * If center and right were in the btree, then the first delete
 421          * call removes the center and the second one removes the right
 422          * extent.
 423          */
 424         error = xfs_refcount_lookup_ge(cur, center->rc_startblock,
 425                         &found_rec);
 426         if (error)
 427                 goto out_error;
 428         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 429                 error = -EFSCORRUPTED;
 430                 goto out_error;
 431         }
 432
 433         error = xfs_refcount_delete(cur, &found_rec);
 434         if (error)
 435                 goto out_error;
 436         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 437                 error = -EFSCORRUPTED;
 438                 goto out_error;
 439         }
 440
 441         if (center->rc_refcount > 1) {
 442                 error = xfs_refcount_delete(cur, &found_rec);
 443                 if (error)
 444                         goto out_error;
 445                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 446                         error = -EFSCORRUPTED;
 447                         goto out_error;
 448                 }
 449         }
 450
 451         /* Enlarge the left extent. */
 452         error = xfs_refcount_lookup_le(cur, left->rc_startblock,
 453                         &found_rec);
 454         if (error)
 455                 goto out_error;
 456         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 457                 error = -EFSCORRUPTED;
 458                 goto out_error;
 459         }
 460
 461         left->rc_blockcount = extlen;
 462         error = xfs_refcount_update(cur, left);
 463         if (error)
 464                 goto out_error;
 465
 466         *aglen = 0;
 467         return error;
 468
 469 out_error:
 470         trace_xfs_refcount_merge_center_extents_error(cur->bc_mp,
 471                         cur->bc_ag.agno, error, _RET_IP_);
 472         return error;
 473 }
 474
 475 /*
 476  * Merge with the left extent.
 477  */
 478 STATIC int
 479 xfs_refcount_merge_left_extent(
 480         struct xfs_btree_cur            *cur,
 481         struct xfs_refcount_irec        *left,
 482         struct xfs_refcount_irec        *cleft,
 483         xfs_agblock_t                   *agbno,
 484         xfs_extlen_t                    *aglen)
 485 {
 486         int                             error;
 487         int                             found_rec;
 488
 489         trace_xfs_refcount_merge_left_extent(cur->bc_mp,
 490                         cur->bc_ag.agno, left, cleft);
 491
 492         /* If the extent at agbno (cleft) wasn't synthesized, remove it. */
 493         if (cleft->rc_refcount > 1) {
 494                 error = xfs_refcount_lookup_le(cur, cleft->rc_startblock,
 495                                 &found_rec);
 496                 if (error)
 497                         goto out_error;
 498                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 499                         error = -EFSCORRUPTED;
 500                         goto out_error;
 501                 }
 502
 503                 error = xfs_refcount_delete(cur, &found_rec);
 504                 if (error)
 505                         goto out_error;
 506                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 507                         error = -EFSCORRUPTED;
 508                         goto out_error;
 509                 }
 510         }
 511
 512         /* Enlarge the left extent. */
 513         error = xfs_refcount_lookup_le(cur, left->rc_startblock,
 514                         &found_rec);
 515         if (error)
 516                 goto out_error;
 517         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 518                 error = -EFSCORRUPTED;
 519                 goto out_error;
 520         }
 521
 522         left->rc_blockcount += cleft->rc_blockcount;
 523         error = xfs_refcount_update(cur, left);
 524         if (error)
 525                 goto out_error;
 526
 527         *agbno += cleft->rc_blockcount;
 528         *aglen -= cleft->rc_blockcount;
 529         return error;
 530
 531 out_error:
 532         trace_xfs_refcount_merge_left_extent_error(cur->bc_mp,
 533                         cur->bc_ag.agno, error, _RET_IP_);
 534         return error;
 535 }
 536
 537 /*
 538  * Merge with the right extent.
 539  */
 540 STATIC int
 541 xfs_refcount_merge_right_extent(
 542         struct xfs_btree_cur            *cur,
 543         struct xfs_refcount_irec        *right,
 544         struct xfs_refcount_irec        *cright,
 545         xfs_extlen_t                    *aglen)
 546 {
 547         int                             error;
 548         int                             found_rec;
 549
 550         trace_xfs_refcount_merge_right_extent(cur->bc_mp,
 551                         cur->bc_ag.agno, cright, right);
 552
 553         /*
 554          * If the extent ending at agbno+aglen (cright) wasn't synthesized,
 555          * remove it.
 556          */
 557         if (cright->rc_refcount > 1) {
 558                 error = xfs_refcount_lookup_le(cur, cright->rc_startblock,
 559                         &found_rec);
 560                 if (error)
 561                         goto out_error;
 562                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 563                         error = -EFSCORRUPTED;
 564                         goto out_error;
 565                 }
 566
 567                 error = xfs_refcount_delete(cur, &found_rec);
 568                 if (error)
 569                         goto out_error;
 570                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 571                         error = -EFSCORRUPTED;
 572                         goto out_error;
 573                 }
 574         }
 575
 576         /* Enlarge the right extent. */
 577         error = xfs_refcount_lookup_le(cur, right->rc_startblock,
 578                         &found_rec);
 579         if (error)
 580                 goto out_error;
 581         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 582                 error = -EFSCORRUPTED;
 583                 goto out_error;
 584         }
 585
 586         right->rc_startblock -= cright->rc_blockcount;
 587         right->rc_blockcount += cright->rc_blockcount;
 588         error = xfs_refcount_update(cur, right);
 589         if (error)
 590                 goto out_error;
 591
 592         *aglen -= cright->rc_blockcount;
 593         return error;
 594
 595 out_error:
 596         trace_xfs_refcount_merge_right_extent_error(cur->bc_mp,
 597                         cur->bc_ag.agno, error, _RET_IP_);
 598         return error;
 599 }
 600
 601 #define XFS_FIND_RCEXT_SHARED   1
 602 #define XFS_FIND_RCEXT_COW      2
 603 /*
 604  * Find the left extent and the one after it (cleft).  This function assumes
 605  * that we've already split any extent crossing agbno.
 606  */
 607 STATIC int
 608 xfs_refcount_find_left_extents(
 609         struct xfs_btree_cur            *cur,
 610         struct xfs_refcount_irec        *left,
 611         struct xfs_refcount_irec        *cleft,
 612         xfs_agblock_t                   agbno,
 613         xfs_extlen_t                    aglen,
 614         int                             flags)
 615 {
 616         struct xfs_refcount_irec        tmp;
 617         int                             error;
 618         int                             found_rec;
 619
 620         left->rc_startblock = cleft->rc_startblock = NULLAGBLOCK;
 621         error = xfs_refcount_lookup_le(cur, agbno - 1, &found_rec);
 622         if (error)
 623                 goto out_error;
 624         if (!found_rec)
 625                 return 0;
 626
 627         error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 628         if (error)
 629                 goto out_error;
 630         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 631                 error = -EFSCORRUPTED;
 632                 goto out_error;
 633         }
 634
 635         if (xfs_refc_next(&tmp) != agbno)
 636                 return 0;
 637         if ((flags & XFS_FIND_RCEXT_SHARED) && tmp.rc_refcount < 2)
 638                 return 0;
 639         if ((flags & XFS_FIND_RCEXT_COW) && tmp.rc_refcount > 1)
 640                 return 0;
 641         /* We have a left extent; retrieve (or invent) the next right one */
 642         *left = tmp;
 643
 644         error = xfs_btree_increment(cur, 0, &found_rec);
 645         if (error)
 646                 goto out_error;
 647         if (found_rec) {
 648                 error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 649                 if (error)
 650                         goto out_error;
 651                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 652                         error = -EFSCORRUPTED;
 653                         goto out_error;
 654                 }
 655
 656                 /* if tmp starts at the end of our range, just use that */
 657                 if (tmp.rc_startblock == agbno)
 658                         *cleft = tmp;
 659                 else {
 660                         /*
 661                          * There's a gap in the refcntbt at the start of the
 662                          * range we're interested in (refcount == 1) so
 663                          * synthesize the implied extent and pass it back.
 664                          * We assume here that the agbno/aglen range was
 665                          * passed in from a data fork extent mapping and
 666                          * therefore is allocated to exactly one owner.
 667                          */
 668                         cleft->rc_startblock = agbno;
 669                         cleft->rc_blockcount = min(aglen,
 670                                         tmp.rc_startblock - agbno);
 671                         cleft->rc_refcount = 1;
 672                 }
 673         } else {
 674                 /*
 675                  * No extents, so pretend that there's one covering the whole
 676                  * range.
 677                  */
 678                 cleft->rc_startblock = agbno;
 679                 cleft->rc_blockcount = aglen;
 680                 cleft->rc_refcount = 1;
 681         }
 682         trace_xfs_refcount_find_left_extent(cur->bc_mp, cur->bc_ag.agno,
 683                         left, cleft, agbno);
 684         return error;
 685
 686 out_error:
 687         trace_xfs_refcount_find_left_extent_error(cur->bc_mp,
 688                         cur->bc_ag.agno, error, _RET_IP_);
 689         return error;
 690 }
 691
 692 /*
 693  * Find the right extent and the one before it (cright).  This function
 694  * assumes that we've already split any extents crossing agbno + aglen.
 695  */
 696 STATIC int
 697 xfs_refcount_find_right_extents(
 698         struct xfs_btree_cur            *cur,
 699         struct xfs_refcount_irec        *right,
 700         struct xfs_refcount_irec        *cright,
 701         xfs_agblock_t                   agbno,
 702         xfs_extlen_t                    aglen,
 703         int                             flags)
 704 {
 705         struct xfs_refcount_irec        tmp;
 706         int                             error;
 707         int                             found_rec;
 708
 709         right->rc_startblock = cright->rc_startblock = NULLAGBLOCK;
 710         error = xfs_refcount_lookup_ge(cur, agbno + aglen, &found_rec);
 711         if (error)
 712                 goto out_error;
 713         if (!found_rec)
 714                 return 0;
 715
 716         error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 717         if (error)
 718                 goto out_error;
 719         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 720                 error = -EFSCORRUPTED;
 721                 goto out_error;
 722         }
 723
 724         if (tmp.rc_startblock != agbno + aglen)
 725                 return 0;
 726         if ((flags & XFS_FIND_RCEXT_SHARED) && tmp.rc_refcount < 2)
 727                 return 0;
 728         if ((flags & XFS_FIND_RCEXT_COW) && tmp.rc_refcount > 1)
 729                 return 0;
 730         /* We have a right extent; retrieve (or invent) the next left one */
 731         *right = tmp;
 732
 733         error = xfs_btree_decrement(cur, 0, &found_rec);
 734         if (error)
 735                 goto out_error;
 736         if (found_rec) {
 737                 error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 738                 if (error)
 739                         goto out_error;
 740                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 741                         error = -EFSCORRUPTED;
 742                         goto out_error;
 743                 }
 744
 745                 /* if tmp ends at the end of our range, just use that */
 746                 if (xfs_refc_next(&tmp) == agbno + aglen)
 747                         *cright = tmp;
 748                 else {
 749                         /*
 750                          * There's a gap in the refcntbt at the end of the
 751                          * range we're interested in (refcount == 1) so
 752                          * create the implied extent and pass it back.
 753                          * We assume here that the agbno/aglen range was
 754                          * passed in from a data fork extent mapping and
 755                          * therefore is allocated to exactly one owner.
 756                          */
 757                         cright->rc_startblock = max(agbno, xfs_refc_next(&tmp));
 758                         cright->rc_blockcount = right->rc_startblock -
 759                                         cright->rc_startblock;
 760                         cright->rc_refcount = 1;
 761                 }
 762         } else {
 763                 /*
 764                  * No extents, so pretend that there's one covering the whole
 765                  * range.
 766                  */
 767                 cright->rc_startblock = agbno;
 768                 cright->rc_blockcount = aglen;
 769                 cright->rc_refcount = 1;
 770         }
 771         trace_xfs_refcount_find_right_extent(cur->bc_mp, cur->bc_ag.agno,
 772                         cright, right, agbno + aglen);
 773         return error;
 774
 775 out_error:
 776         trace_xfs_refcount_find_right_extent_error(cur->bc_mp,
 777                         cur->bc_ag.agno, error, _RET_IP_);
 778         return error;
 779 }
 780
 781 /* Is this extent valid? */
 782 static inline bool
 783 xfs_refc_valid(
 784         struct xfs_refcount_irec        *rc)
 785 {
 786         return rc->rc_startblock != NULLAGBLOCK;
 787 }
 788
 789 /*
 790  * Try to merge with any extents on the boundaries of the adjustment range.
 791  */
 792 STATIC int
 793 xfs_refcount_merge_extents(
 794         struct xfs_btree_cur    *cur,
 795         xfs_agblock_t           *agbno,
 796         xfs_extlen_t            *aglen,
 797         enum xfs_refc_adjust_op adjust,
 798         int                     flags,
 799         bool                    *shape_changed)
 800 {
 801         struct xfs_refcount_irec        left = {0}, cleft = {0};
 802         struct xfs_refcount_irec        cright = {0}, right = {0};
 803         int                             error;
 804         unsigned long long              ulen;
 805         bool                            cequal;
 806
 807         *shape_changed = false;
 808         /*
 809          * Find the extent just below agbno [left], just above agbno [cleft],
 810          * just below (agbno + aglen) [cright], and just above (agbno + aglen)
 811          * [right].
 812          */
 813         error = xfs_refcount_find_left_extents(cur, &left, &cleft, *agbno,
 814                         *aglen, flags);
 815         if (error)
 816                 return error;
 817         error = xfs_refcount_find_right_extents(cur, &right, &cright, *agbno,
 818                         *aglen, flags);
 819         if (error)
 820                 return error;
 821
 822         /* No left or right extent to merge; exit. */
 823         if (!xfs_refc_valid(&left) && !xfs_refc_valid(&right))
 824                 return 0;
 825
 826         cequal = (cleft.rc_startblock == cright.rc_startblock) &&
 827                  (cleft.rc_blockcount == cright.rc_blockcount);
 828
 829         /* Try to merge left, cleft, and right.  cleft must == cright. */
 830         ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount +
 831                         right.rc_blockcount;
 832         if (xfs_refc_valid(&left) && xfs_refc_valid(&right) &&
 833             xfs_refc_valid(&cleft) && xfs_refc_valid(&cright) && cequal &&
 834             left.rc_refcount == cleft.rc_refcount + adjust &&
 835             right.rc_refcount == cleft.rc_refcount + adjust &&
 836             ulen < MAXREFCEXTLEN) {
 837                 *shape_changed = true;
 838                 return xfs_refcount_merge_center_extents(cur, &left, &cleft,
 839                                 &right, ulen, aglen);
 840         }
 841
 842         /* Try to merge left and cleft. */
 843         ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount;
 844         if (xfs_refc_valid(&left) && xfs_refc_valid(&cleft) &&
 845             left.rc_refcount == cleft.rc_refcount + adjust &&
 846             ulen < MAXREFCEXTLEN) {
 847                 *shape_changed = true;
 848                 error = xfs_refcount_merge_left_extent(cur, &left, &cleft,
 849                                 agbno, aglen);
 850                 if (error)
 851                         return error;
 852
 853                 /*
 854                  * If we just merged left + cleft and cleft == cright,
 855                  * we no longer have a cright to merge with right.  We're done.
 856                  */
 857                 if (cequal)
 858                         return 0;
 859         }
 860
 861         /* Try to merge cright and right. */
 862         ulen = (unsigned long long)right.rc_blockcount + cright.rc_blockcount;
 863         if (xfs_refc_valid(&right) && xfs_refc_valid(&cright) &&
 864             right.rc_refcount == cright.rc_refcount + adjust &&
 865             ulen < MAXREFCEXTLEN) {
 866                 *shape_changed = true;
 867                 return xfs_refcount_merge_right_extent(cur, &right, &cright,
 868                                 aglen);
 869         }
 870
 871         return error;
 872 }
 873
 874 /*
 875  * XXX: This is a pretty hand-wavy estimate.  The penalty for guessing
 876  * true incorrectly is a shutdown FS; the penalty for guessing false
 877  * incorrectly is more transaction rolls than might be necessary.
 878  * Be conservative here.
 879  */
 880 static bool
 881 xfs_refcount_still_have_space(
 882         struct xfs_btree_cur            *cur)
 883 {
 884         unsigned long                   overhead;
 885
 886         overhead = cur->bc_ag.refc.shape_changes *
 887                         xfs_allocfree_log_count(cur->bc_mp, 1);
 888         overhead *= cur->bc_mp->m_sb.sb_blocksize;
 889
 890         /*
 891          * Only allow 2 refcount extent updates per transaction if the
 892          * refcount continue update "error" has been injected.
 893          */
 894         if (cur->bc_ag.refc.nr_ops > 2 &&
 895             XFS_TEST_ERROR(false, cur->bc_mp,
 896                         XFS_ERRTAG_REFCOUNT_CONTINUE_UPDATE))
 897                 return false;
 898
 899         if (cur->bc_ag.refc.nr_ops == 0)
 900                 return true;
 901         else if (overhead > cur->bc_tp->t_log_res)
 902                 return false;
 903         return  cur->bc_tp->t_log_res - overhead >
 904                 cur->bc_ag.refc.nr_ops * XFS_REFCOUNT_ITEM_OVERHEAD;
 905 }
 906
 907 /*
 908  * Adjust the refcounts of middle extents.  At this point we should have
 909  * split extents that crossed the adjustment range; merged with adjacent
 910  * extents; and updated agbno/aglen to reflect the merges.  Therefore,
 911  * all we have to do is update the extents inside [agbno, agbno + aglen].
 912  */
 913 STATIC int
 914 xfs_refcount_adjust_extents(
 915         struct xfs_btree_cur    *cur,
 916         xfs_agblock_t           *agbno,
 917         xfs_extlen_t            *aglen,
 918         enum xfs_refc_adjust_op adj,
 919         struct xfs_owner_info   *oinfo)
 920 {
 921         struct xfs_refcount_irec        ext, tmp;
 922         int                             error;
 923         int                             found_rec, found_tmp;
 924         xfs_fsblock_t                   fsbno;
 925
 926         /* Merging did all the work already. */
 927         if (*aglen == 0)
 928                 return 0;
 929
 930         error = xfs_refcount_lookup_ge(cur, *agbno, &found_rec);
 931         if (error)
 932                 goto out_error;
 933
 934         while (*aglen > 0 && xfs_refcount_still_have_space(cur)) {
 935                 error = xfs_refcount_get_rec(cur, &ext, &found_rec);
 936                 if (error)
 937                         goto out_error;
 938                 if (!found_rec) {
 939                         ext.rc_startblock = cur->bc_mp->m_sb.sb_agblocks;
 940                         ext.rc_blockcount = 0;
 941                         ext.rc_refcount = 0;
 942                 }
 943
 944                 /*
 945                  * Deal with a hole in the refcount tree; if a file maps to
 946                  * these blocks and there's no refcountbt record, pretend that
 947                  * there is one with refcount == 1.
 948                  */
 949                 if (ext.rc_startblock != *agbno) {
 950                         tmp.rc_startblock = *agbno;
 951                         tmp.rc_blockcount = min(*aglen,
 952                                         ext.rc_startblock - *agbno);
 953                         tmp.rc_refcount = 1 + adj;
 954                         trace_xfs_refcount_modify_extent(cur->bc_mp,
 955                                         cur->bc_ag.agno, &tmp);
 956
 957                         /*
 958                          * Either cover the hole (increment) or
 959                          * delete the range (decrement).
 960                          */
 961                         if (tmp.rc_refcount) {
 962                                 error = xfs_refcount_insert(cur, &tmp,
 963                                                 &found_tmp);
 964                                 if (error)
 965                                         goto out_error;
 966                                 if (XFS_IS_CORRUPT(cur->bc_mp,
 967                                                    found_tmp != 1)) {
 968                                         error = -EFSCORRUPTED;
 969                                         goto out_error;
 970                                 }
 971                                 cur->bc_ag.refc.nr_ops++;
 972                         } else {
 973                                 fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
 974                                                 cur->bc_ag.agno,
 975                                                 tmp.rc_startblock);
 976                                 xfs_bmap_add_free(cur->bc_tp, fsbno,
 977                                                   tmp.rc_blockcount, oinfo);
 978                         }
 979
 980                         (*agbno) += tmp.rc_blockcount;
 981                         (*aglen) -= tmp.rc_blockcount;
 982
 983                         error = xfs_refcount_lookup_ge(cur, *agbno,
 984                                         &found_rec);
 985                         if (error)
 986                                 goto out_error;
 987                 }
 988
 989                 /* Stop if there's nothing left to modify */
 990                 if (*aglen == 0 || !xfs_refcount_still_have_space(cur))
 991                         break;
 992
 993                 /*
 994                  * Adjust the reference count and either update the tree
 995                  * (incr) or free the blocks (decr).
 996                  */
 997                 if (ext.rc_refcount == MAXREFCOUNT)
 998                         goto skip;
 999                 ext.rc_refcount += adj;
1000                 trace_xfs_refcount_modify_extent(cur->bc_mp,
1001                                 cur->bc_ag.agno, &ext);
1002                 if (ext.rc_refcount > 1) {
1003                         error = xfs_refcount_update(cur, &ext);
1004                         if (error)
1005                                 goto out_error;
1006                         cur->bc_ag.refc.nr_ops++;
1007                 } else if (ext.rc_refcount == 1) {
1008                         error = xfs_refcount_delete(cur, &found_rec);
1009                         if (error)
1010                                 goto out_error;
1011                         if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
1012                                 error = -EFSCORRUPTED;
1013                                 goto out_error;
1014                         }
1015                         cur->bc_ag.refc.nr_ops++;
1016                         goto advloop;
1017                 } else {
1018                         fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
1019                                         cur->bc_ag.agno,
1020                                         ext.rc_startblock);
1021                         xfs_bmap_add_free(cur->bc_tp, fsbno, ext.rc_blockcount,
1022                                           oinfo);
1023                 }
1024
1025 skip:
1026                 error = xfs_btree_increment(cur, 0, &found_rec);
1027                 if (error)
1028                         goto out_error;
1029
1030 advloop:
1031                 (*agbno) += ext.rc_blockcount;
1032                 (*aglen) -= ext.rc_blockcount;
1033         }
1034
1035         return error;
1036 out_error:
1037         trace_xfs_refcount_modify_extent_error(cur->bc_mp,
1038                         cur->bc_ag.agno, error, _RET_IP_);
1039         return error;
1040 }
1041
1042 /* Adjust the reference count of a range of AG blocks. */
1043 STATIC int
1044 xfs_refcount_adjust(
1045         struct xfs_btree_cur    *cur,
1046         xfs_agblock_t           agbno,
1047         xfs_extlen_t            aglen,
1048         xfs_agblock_t           *new_agbno,
1049         xfs_extlen_t            *new_aglen,
1050         enum xfs_refc_adjust_op adj,
1051         struct xfs_owner_info   *oinfo)
1052 {
1053         bool                    shape_changed;
1054         int                     shape_changes = 0;
1055         int                     error;
1056
1057         *new_agbno = agbno;
1058         *new_aglen = aglen;
1059         if (adj == XFS_REFCOUNT_ADJUST_INCREASE)
1060                 trace_xfs_refcount_increase(cur->bc_mp, cur->bc_ag.agno,
1061                                 agbno, aglen);
1062         else
1063                 trace_xfs_refcount_decrease(cur->bc_mp, cur->bc_ag.agno,
1064                                 agbno, aglen);
1065
1066         /*
1067          * Ensure that no rcextents cross the boundary of the adjustment range.
1068          */
1069         error = xfs_refcount_split_extent(cur, agbno, &shape_changed);
1070         if (error)
1071                 goto out_error;
1072         if (shape_changed)
1073                 shape_changes++;
1074
1075         error = xfs_refcount_split_extent(cur, agbno + aglen, &shape_changed);
1076         if (error)
1077                 goto out_error;
1078         if (shape_changed)
1079                 shape_changes++;
1080
1081         /*
1082          * Try to merge with the left or right extents of the range.
1083          */
1084         error = xfs_refcount_merge_extents(cur, new_agbno, new_aglen, adj,
1085                         XFS_FIND_RCEXT_SHARED, &shape_changed);
1086         if (error)
1087                 goto out_error;
1088         if (shape_changed)
1089                 shape_changes++;
1090         if (shape_changes)
1091                 cur->bc_ag.refc.shape_changes++;
1092
1093         /* Now that we've taken care of the ends, adjust the middle extents */
1094         error = xfs_refcount_adjust_extents(cur, new_agbno, new_aglen,
1095                         adj, oinfo);
1096         if (error)
1097                 goto out_error;
1098
1099         return 0;
1100
1101 out_error:
1102         trace_xfs_refcount_adjust_error(cur->bc_mp, cur->bc_ag.agno,
1103                         error, _RET_IP_);
1104         return error;
1105 }
1106
1107 /* Clean up after calling xfs_refcount_finish_one. */
1108 void
1109 xfs_refcount_finish_one_cleanup(
1110         struct xfs_trans        *tp,
1111         struct xfs_btree_cur    *rcur,
1112         int                     error)
1113 {
1114         struct xfs_buf          *agbp;
1115
1116         if (rcur == NULL)
1117                 return;
1118         agbp = rcur->bc_ag.agbp;
1119         xfs_btree_del_cursor(rcur, error);
1120         if (error)
1121                 xfs_trans_brelse(tp, agbp);
1122 }
1123
1124 /*
1125  * Process one of the deferred refcount operations.  We pass back the
1126  * btree cursor to maintain our lock on the btree between calls.
1127  * This saves time and eliminates a buffer deadlock between the
1128  * superblock and the AGF because we'll always grab them in the same
1129  * order.
1130  */
1131 int
1132 xfs_refcount_finish_one(
1133         struct xfs_trans                *tp,
1134         enum xfs_refcount_intent_type   type,
1135         xfs_fsblock_t                   startblock,
1136         xfs_extlen_t                    blockcount,
1137         xfs_fsblock_t                   *new_fsb,
1138         xfs_extlen_t                    *new_len,
1139         struct xfs_btree_cur            **pcur)
1140 {
1141         struct xfs_mount                *mp = tp->t_mountp;
1142         struct xfs_btree_cur            *rcur;
1143         struct xfs_buf                  *agbp = NULL;
1144         int                             error = 0;
1145         xfs_agnumber_t                  agno;
1146         xfs_agblock_t                   bno;
1147         xfs_agblock_t                   new_agbno;
1148         unsigned long                   nr_ops = 0;
1149         int                             shape_changes = 0;
1150
1151         agno = XFS_FSB_TO_AGNO(mp, startblock);
1152         ASSERT(agno != NULLAGNUMBER);
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,
1160                         XFS_ERRTAG_REFCOUNT_FINISH_ONE))
1161                 return -EIO;
1162
1163         /*
1164          * If we haven't gotten a cursor or the cursor AG doesn't match
1165          * the startblock, get one now.
1166          */
1167         rcur = *pcur;
1168         if (rcur != NULL && rcur->bc_ag.agno != agno) {
1169                 nr_ops = rcur->bc_ag.refc.nr_ops;
1170                 shape_changes = rcur->bc_ag.refc.shape_changes;
1171                 xfs_refcount_finish_one_cleanup(tp, rcur, 0);
1172                 rcur = NULL;
1173                 *pcur = NULL;
1174         }
1175         if (rcur == NULL) {
1176                 error = xfs_alloc_read_agf(tp->t_mountp, tp, agno,
1177                                 XFS_ALLOC_FLAG_FREEING, &agbp);
1178                 if (error)
1179                         return error;
1180
1181                 rcur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno);
1182                 if (!rcur) {
1183                         error = -ENOMEM;
1184                         goto out_cur;
1185                 }
1186                 rcur->bc_ag.refc.nr_ops = nr_ops;
1187                 rcur->bc_ag.refc.shape_changes = shape_changes;
1188         }
1189         *pcur = rcur;
1190
1191         switch (type) {
1192         case XFS_REFCOUNT_INCREASE:
1193                 error = xfs_refcount_adjust(rcur, bno, blockcount, &new_agbno,
1194                         new_len, XFS_REFCOUNT_ADJUST_INCREASE, NULL);
1195                 *new_fsb = XFS_AGB_TO_FSB(mp, agno, new_agbno);
1196                 break;
1197         case XFS_REFCOUNT_DECREASE:
1198                 error = xfs_refcount_adjust(rcur, bno, blockcount, &new_agbno,
1199                         new_len, XFS_REFCOUNT_ADJUST_DECREASE, NULL);
1200                 *new_fsb = XFS_AGB_TO_FSB(mp, agno, new_agbno);
1201                 break;
1202         case XFS_REFCOUNT_ALLOC_COW:
1203                 *new_fsb = startblock + blockcount;
1204                 *new_len = 0;
1205                 error = __xfs_refcount_cow_alloc(rcur, bno, blockcount);
1206                 break;
1207         case XFS_REFCOUNT_FREE_COW:
1208                 *new_fsb = startblock + blockcount;
1209                 *new_len = 0;
1210                 error = __xfs_refcount_cow_free(rcur, bno, blockcount);
1211                 break;
1212         default:
1213                 ASSERT(0);
1214                 error = -EFSCORRUPTED;
1215         }
1216         if (!error && *new_len > 0)
1217                 trace_xfs_refcount_finish_one_leftover(mp, agno, type,
1218                                 bno, blockcount, new_agbno, *new_len);
1219         return error;
1220
1221 out_cur:
1222         xfs_trans_brelse(tp, agbp);
1223
1224         return error;
1225 }
1226
1227 /*
1228  * Record a refcount intent for later processing.
1229  */
1230 static void
1231 __xfs_refcount_add(
1232         struct xfs_trans                *tp,
1233         enum xfs_refcount_intent_type   type,
1234         xfs_fsblock_t                   startblock,
1235         xfs_extlen_t                    blockcount)
1236 {
1237         struct xfs_refcount_intent      *ri;
1238
1239         trace_xfs_refcount_defer(tp->t_mountp,
1240                         XFS_FSB_TO_AGNO(tp->t_mountp, startblock),
1241                         type, XFS_FSB_TO_AGBNO(tp->t_mountp, startblock),
1242                         blockcount);
1243
1244         ri = kmem_alloc(sizeof(struct xfs_refcount_intent),
1245                         KM_NOFS);
1246         INIT_LIST_HEAD(&ri->ri_list);
1247         ri->ri_type = type;
1248         ri->ri_startblock = startblock;
1249         ri->ri_blockcount = blockcount;
1250
1251         xfs_defer_add(tp, XFS_DEFER_OPS_TYPE_REFCOUNT, &ri->ri_list);
1252 }
1253
1254 /*
1255  * Increase the reference count of the blocks backing a file's extent.
1256  */
1257 void
1258 xfs_refcount_increase_extent(
1259         struct xfs_trans                *tp,
1260         struct xfs_bmbt_irec            *PREV)
1261 {
1262         if (!xfs_sb_version_hasreflink(&tp->t_mountp->m_sb))
1263                 return;
1264
1265         __xfs_refcount_add(tp, XFS_REFCOUNT_INCREASE, PREV->br_startblock,
1266                         PREV->br_blockcount);
1267 }
1268
1269 /*
1270  * Decrease the reference count of the blocks backing a file's extent.
1271  */
1272 void
1273 xfs_refcount_decrease_extent(
1274         struct xfs_trans                *tp,
1275         struct xfs_bmbt_irec            *PREV)
1276 {
1277         if (!xfs_sb_version_hasreflink(&tp->t_mountp->m_sb))
1278                 return;
1279
1280         __xfs_refcount_add(tp, XFS_REFCOUNT_DECREASE, PREV->br_startblock,
1281                         PREV->br_blockcount);
1282 }
1283
1284 /*
1285  * Given an AG extent, find the lowest-numbered run of shared blocks
1286  * within that range and return the range in fbno/flen.  If
1287  * find_end_of_shared is set, return the longest contiguous extent of
1288  * shared blocks; if not, just return the first extent we find.  If no
1289  * shared blocks are found, fbno and flen will be set to NULLAGBLOCK
1290  * and 0, respectively.
1291  */
1292 int
1293 xfs_refcount_find_shared(
1294         struct xfs_btree_cur            *cur,
1295         xfs_agblock_t                   agbno,
1296         xfs_extlen_t                    aglen,
1297         xfs_agblock_t                   *fbno,
1298         xfs_extlen_t                    *flen,
1299         bool                            find_end_of_shared)
1300 {
1301         struct xfs_refcount_irec        tmp;
1302         int                             i;
1303         int                             have;
1304         int                             error;
1305
1306         trace_xfs_refcount_find_shared(cur->bc_mp, cur->bc_ag.agno,
1307                         agbno, aglen);
1308
1309         /* By default, skip the whole range */
1310         *fbno = NULLAGBLOCK;
1311         *flen = 0;
1312
1313         /* Try to find a refcount extent that crosses the start */
1314         error = xfs_refcount_lookup_le(cur, agbno, &have);
1315         if (error)
1316                 goto out_error;
1317         if (!have) {
1318                 /* No left extent, look at the next one */
1319                 error = xfs_btree_increment(cur, 0, &have);
1320                 if (error)
1321                         goto out_error;
1322                 if (!have)
1323                         goto done;
1324         }
1325         error = xfs_refcount_get_rec(cur, &tmp, &i);
1326         if (error)
1327                 goto out_error;
1328         if (XFS_IS_CORRUPT(cur->bc_mp, i != 1)) {
1329                 error = -EFSCORRUPTED;
1330                 goto out_error;
1331         }
1332
1333         /* If the extent ends before the start, look at the next one */
1334         if (tmp.rc_startblock + tmp.rc_blockcount <= agbno) {
1335                 error = xfs_btree_increment(cur, 0, &have);
1336                 if (error)
1337                         goto out_error;
1338                 if (!have)
1339                         goto done;
1340                 error = xfs_refcount_get_rec(cur, &tmp, &i);
1341                 if (error)
1342                         goto out_error;
1343                 if (XFS_IS_CORRUPT(cur->bc_mp, i != 1)) {
1344                         error = -EFSCORRUPTED;
1345                         goto out_error;
1346                 }
1347         }
1348
1349         /* If the extent starts after the range we want, bail out */
1350         if (tmp.rc_startblock >= agbno + aglen)
1351                 goto done;
1352
1353         /* We found the start of a shared extent! */
1354         if (tmp.rc_startblock < agbno) {
1355                 tmp.rc_blockcount -= (agbno - tmp.rc_startblock);
1356                 tmp.rc_startblock = agbno;
1357         }
1358
1359         *fbno = tmp.rc_startblock;
1360         *flen = min(tmp.rc_blockcount, agbno + aglen - *fbno);
1361         if (!find_end_of_shared)
1362                 goto done;
1363
1364         /* Otherwise, find the end of this shared extent */
1365         while (*fbno + *flen < agbno + aglen) {
1366                 error = xfs_btree_increment(cur, 0, &have);
1367                 if (error)
1368                         goto out_error;
1369                 if (!have)
1370                         break;
1371                 error = xfs_refcount_get_rec(cur, &tmp, &i);
1372                 if (error)
1373                         goto out_error;
1374                 if (XFS_IS_CORRUPT(cur->bc_mp, i != 1)) {
1375                         error = -EFSCORRUPTED;
1376                         goto out_error;
1377                 }
1378                 if (tmp.rc_startblock >= agbno + aglen ||
1379                     tmp.rc_startblock != *fbno + *flen)
1380                         break;
1381                 *flen = min(*flen + tmp.rc_blockcount, agbno + aglen - *fbno);
1382         }
1383
1384 done:
1385         trace_xfs_refcount_find_shared_result(cur->bc_mp,
1386                         cur->bc_ag.agno, *fbno, *flen);
1387
1388 out_error:
1389         if (error)
1390                 trace_xfs_refcount_find_shared_error(cur->bc_mp,
1391                                 cur->bc_ag.agno, error, _RET_IP_);
1392         return error;
1393 }
1394
1395 /*
1396  * Recovering CoW Blocks After a Crash
1397  *
1398  * Due to the way that the copy on write mechanism works, there's a window of
1399  * opportunity in which we can lose track of allocated blocks during a crash.
1400  * Because CoW uses delayed allocation in the in-core CoW fork, writeback
1401  * causes blocks to be allocated and stored in the CoW fork.  The blocks are
1402  * no longer in the free space btree but are not otherwise recorded anywhere
1403  * until the write completes and the blocks are mapped into the file.  A crash
1404  * in between allocation and remapping results in the replacement blocks being
1405  * lost.  This situation is exacerbated by the CoW extent size hint because
1406  * allocations can hang around for long time.
1407  *
1408  * However, there is a place where we can record these allocations before they
1409  * become mappings -- the reference count btree.  The btree does not record
1410  * extents with refcount == 1, so we can record allocations with a refcount of
1411  * 1.  Blocks being used for CoW writeout cannot be shared, so there should be
1412  * no conflict with shared block records.  These mappings should be created
1413  * when we allocate blocks to the CoW fork and deleted when they're removed
1414  * from the CoW fork.
1415  *
1416  * Minor nit: records for in-progress CoW allocations and records for shared
1417  * extents must never be merged, to preserve the property that (except for CoW
1418  * allocations) there are no refcount btree entries with refcount == 1.  The
1419  * only time this could potentially happen is when unsharing a block that's
1420  * adjacent to CoW allocations, so we must be careful to avoid this.
1421  *
1422  * At mount time we recover lost CoW allocations by searching the refcount
1423  * btree for these refcount == 1 mappings.  These represent CoW allocations
1424  * that were in progress at the time the filesystem went down, so we can free
1425  * them to get the space back.
1426  *
1427  * This mechanism is superior to creating EFIs for unmapped CoW extents for
1428  * several reasons -- first, EFIs pin the tail of the log and would have to be
1429  * periodically relogged to avoid filling up the log.  Second, CoW completions
1430  * will have to file an EFD and create new EFIs for whatever remains in the
1431  * CoW fork; this partially takes care of (1) but extent-size reservations
1432  * will have to periodically relog even if there's no writeout in progress.
1433  * This can happen if the CoW extent size hint is set, which you really want.
1434  * Third, EFIs cannot currently be automatically relogged into newer
1435  * transactions to advance the log tail.  Fourth, stuffing the log full of
1436  * EFIs places an upper bound on the number of CoW allocations that can be
1437  * held filesystem-wide at any given time.  Recording them in the refcount
1438  * btree doesn't require us to maintain any state in memory and doesn't pin
1439  * the log.
1440  */
1441 /*
1442  * Adjust the refcounts of CoW allocations.  These allocations are "magic"
1443  * in that they're not referenced anywhere else in the filesystem, so we
1444  * stash them in the refcount btree with a refcount of 1 until either file
1445  * remapping (or CoW cancellation) happens.
1446  */
1447 STATIC int
1448 xfs_refcount_adjust_cow_extents(
1449         struct xfs_btree_cur    *cur,
1450         xfs_agblock_t           agbno,
1451         xfs_extlen_t            aglen,
1452         enum xfs_refc_adjust_op adj)
1453 {
1454         struct xfs_refcount_irec        ext, tmp;
1455         int                             error;
1456         int                             found_rec, found_tmp;
1457
1458         if (aglen == 0)
1459                 return 0;
1460
1461         /* Find any overlapping refcount records */
1462         error = xfs_refcount_lookup_ge(cur, agbno, &found_rec);
1463         if (error)
1464                 goto out_error;
1465         error = xfs_refcount_get_rec(cur, &ext, &found_rec);
1466         if (error)
1467                 goto out_error;
1468         if (!found_rec) {
1469                 ext.rc_startblock = cur->bc_mp->m_sb.sb_agblocks +
1470                                 XFS_REFC_COW_START;
1471                 ext.rc_blockcount = 0;
1472                 ext.rc_refcount = 0;
1473         }
1474
1475         switch (adj) {
1476         case XFS_REFCOUNT_ADJUST_COW_ALLOC:
1477                 /* Adding a CoW reservation, there should be nothing here. */
1478                 if (XFS_IS_CORRUPT(cur->bc_mp,
1479                                    agbno + aglen > ext.rc_startblock)) {
1480                         error = -EFSCORRUPTED;
1481                         goto out_error;
1482                 }
1483
1484                 tmp.rc_startblock = agbno;
1485                 tmp.rc_blockcount = aglen;
1486                 tmp.rc_refcount = 1;
1487                 trace_xfs_refcount_modify_extent(cur->bc_mp,
1488                                 cur->bc_ag.agno, &tmp);
1489
1490                 error = xfs_refcount_insert(cur, &tmp,
1491                                 &found_tmp);
1492                 if (error)
1493                         goto out_error;
1494                 if (XFS_IS_CORRUPT(cur->bc_mp, found_tmp != 1)) {
1495                         error = -EFSCORRUPTED;
1496                         goto out_error;
1497                 }
1498                 break;
1499         case XFS_REFCOUNT_ADJUST_COW_FREE:
1500                 /* Removing a CoW reservation, there should be one extent. */
1501                 if (XFS_IS_CORRUPT(cur->bc_mp, ext.rc_startblock != agbno)) {
1502                         error = -EFSCORRUPTED;
1503                         goto out_error;
1504                 }
1505                 if (XFS_IS_CORRUPT(cur->bc_mp, ext.rc_blockcount != aglen)) {
1506                         error = -EFSCORRUPTED;
1507                         goto out_error;
1508                 }
1509                 if (XFS_IS_CORRUPT(cur->bc_mp, ext.rc_refcount != 1)) {
1510                         error = -EFSCORRUPTED;
1511                         goto out_error;
1512                 }
1513
1514                 ext.rc_refcount = 0;
1515                 trace_xfs_refcount_modify_extent(cur->bc_mp,
1516                                 cur->bc_ag.agno, &ext);
1517                 error = xfs_refcount_delete(cur, &found_rec);
1518                 if (error)
1519                         goto out_error;
1520                 if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
1521                         error = -EFSCORRUPTED;
1522                         goto out_error;
1523                 }
1524                 break;
1525         default:
1526                 ASSERT(0);
1527         }
1528
1529         return error;
1530 out_error:
1531         trace_xfs_refcount_modify_extent_error(cur->bc_mp,
1532                         cur->bc_ag.agno, error, _RET_IP_);
1533         return error;
1534 }
1535
1536 /*
1537  * Add or remove refcount btree entries for CoW reservations.
1538  */
1539 STATIC int
1540 xfs_refcount_adjust_cow(
1541         struct xfs_btree_cur    *cur,
1542         xfs_agblock_t           agbno,
1543         xfs_extlen_t            aglen,
1544         enum xfs_refc_adjust_op adj)
1545 {
1546         bool                    shape_changed;
1547         int                     error;
1548
1549         agbno += XFS_REFC_COW_START;
1550
1551         /*
1552          * Ensure that no rcextents cross the boundary of the adjustment range.
1553          */
1554         error = xfs_refcount_split_extent(cur, agbno, &shape_changed);
1555         if (error)
1556                 goto out_error;
1557
1558         error = xfs_refcount_split_extent(cur, agbno + aglen, &shape_changed);
1559         if (error)
1560                 goto out_error;
1561
1562         /*
1563          * Try to merge with the left or right extents of the range.
1564          */
1565         error = xfs_refcount_merge_extents(cur, &agbno, &aglen, adj,
1566                         XFS_FIND_RCEXT_COW, &shape_changed);
1567         if (error)
1568                 goto out_error;
1569
1570         /* Now that we've taken care of the ends, adjust the middle extents */
1571         error = xfs_refcount_adjust_cow_extents(cur, agbno, aglen, adj);
1572         if (error)
1573                 goto out_error;
1574
1575         return 0;
1576
1577 out_error:
1578         trace_xfs_refcount_adjust_cow_error(cur->bc_mp, cur->bc_ag.agno,
1579                         error, _RET_IP_);
1580         return error;
1581 }
1582
1583 /*
1584  * Record a CoW allocation in the refcount btree.
1585  */
1586 STATIC int
1587 __xfs_refcount_cow_alloc(
1588         struct xfs_btree_cur    *rcur,
1589         xfs_agblock_t           agbno,
1590         xfs_extlen_t            aglen)
1591 {
1592         trace_xfs_refcount_cow_increase(rcur->bc_mp, rcur->bc_ag.agno,
1593                         agbno, aglen);
1594
1595         /* Add refcount btree reservation */
1596         return xfs_refcount_adjust_cow(rcur, agbno, aglen,
1597                         XFS_REFCOUNT_ADJUST_COW_ALLOC);
1598 }
1599
1600 /*
1601  * Remove a CoW allocation from the refcount btree.
1602  */
1603 STATIC int
1604 __xfs_refcount_cow_free(
1605         struct xfs_btree_cur    *rcur,
1606         xfs_agblock_t           agbno,
1607         xfs_extlen_t            aglen)
1608 {
1609         trace_xfs_refcount_cow_decrease(rcur->bc_mp, rcur->bc_ag.agno,
1610                         agbno, aglen);
1611
1612         /* Remove refcount btree reservation */
1613         return xfs_refcount_adjust_cow(rcur, agbno, aglen,
1614                         XFS_REFCOUNT_ADJUST_COW_FREE);
1615 }
1616
1617 /* Record a CoW staging extent in the refcount btree. */
1618 void
1619 xfs_refcount_alloc_cow_extent(
1620         struct xfs_trans                *tp,
1621         xfs_fsblock_t                   fsb,
1622         xfs_extlen_t                    len)
1623 {
1624         struct xfs_mount                *mp = tp->t_mountp;
1625
1626         if (!xfs_sb_version_hasreflink(&mp->m_sb))
1627                 return;
1628
1629         __xfs_refcount_add(tp, XFS_REFCOUNT_ALLOC_COW, fsb, len);
1630
1631         /* Add rmap entry */
1632         xfs_rmap_alloc_extent(tp, XFS_FSB_TO_AGNO(mp, fsb),
1633                         XFS_FSB_TO_AGBNO(mp, fsb), len, XFS_RMAP_OWN_COW);
1634 }
1635
1636 /* Forget a CoW staging event in the refcount btree. */
1637 void
1638 xfs_refcount_free_cow_extent(
1639         struct xfs_trans                *tp,
1640         xfs_fsblock_t                   fsb,
1641         xfs_extlen_t                    len)
1642 {
1643         struct xfs_mount                *mp = tp->t_mountp;
1644
1645         if (!xfs_sb_version_hasreflink(&mp->m_sb))
1646                 return;
1647
1648         /* Remove rmap entry */
1649         xfs_rmap_free_extent(tp, XFS_FSB_TO_AGNO(mp, fsb),
1650                         XFS_FSB_TO_AGBNO(mp, fsb), len, XFS_RMAP_OWN_COW);
1651         __xfs_refcount_add(tp, XFS_REFCOUNT_FREE_COW, fsb, len);
1652 }
1653
1654 struct xfs_refcount_recovery {
1655         struct list_head                rr_list;
1656         struct xfs_refcount_irec        rr_rrec;
1657 };
1658
1659 /* Stuff an extent on the recovery list. */
1660 STATIC int
1661 xfs_refcount_recover_extent(
1662         struct xfs_btree_cur            *cur,
1663         union xfs_btree_rec             *rec,
1664         void                            *priv)
1665 {
1666         struct list_head                *debris = priv;
1667         struct xfs_refcount_recovery    *rr;
1668
1669         if (XFS_IS_CORRUPT(cur->bc_mp,
1670                            be32_to_cpu(rec->refc.rc_refcount) != 1))
1671                 return -EFSCORRUPTED;
1672
1673         rr = kmem_alloc(sizeof(struct xfs_refcount_recovery), 0);
1674         xfs_refcount_btrec_to_irec(rec, &rr->rr_rrec);
1675         list_add_tail(&rr->rr_list, debris);
1676
1677         return 0;
1678 }
1679
1680 /* Find and remove leftover CoW reservations. */
1681 int
1682 xfs_refcount_recover_cow_leftovers(
1683         struct xfs_mount                *mp,
1684         xfs_agnumber_t                  agno)
1685 {
1686         struct xfs_trans                *tp;
1687         struct xfs_btree_cur            *cur;
1688         struct xfs_buf                  *agbp;
1689         struct xfs_refcount_recovery    *rr, *n;
1690         struct list_head                debris;
1691         union xfs_btree_irec            low;
1692         union xfs_btree_irec            high;
1693         xfs_fsblock_t                   fsb;
1694         xfs_agblock_t                   agbno;
1695         int                             error;
1696
1697         if (mp->m_sb.sb_agblocks >= XFS_REFC_COW_START)
1698                 return -EOPNOTSUPP;
1699
1700         INIT_LIST_HEAD(&debris);
1701
1702         /*
1703          * In this first part, we use an empty transaction to gather up
1704          * all the leftover CoW extents so that we can subsequently
1705          * delete them.  The empty transaction is used to avoid
1706          * a buffer lock deadlock if there happens to be a loop in the
1707          * refcountbt because we're allowed to re-grab a buffer that is
1708          * already attached to our transaction.  When we're done
1709          * recording the CoW debris we cancel the (empty) transaction
1710          * and everything goes away cleanly.
1711          */
1712         error = xfs_trans_alloc_empty(mp, &tp);
1713         if (error)
1714                 return error;
1715
1716         error = xfs_alloc_read_agf(mp, tp, agno, 0, &agbp);
1717         if (error)
1718                 goto out_trans;
1719         cur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno);
1720
1721         /* Find all the leftover CoW staging extents. */
1722         memset(&low, 0, sizeof(low));
1723         memset(&high, 0, sizeof(high));
1724         low.rc.rc_startblock = XFS_REFC_COW_START;
1725         high.rc.rc_startblock = -1U;
1726         error = xfs_btree_query_range(cur, &low, &high,
1727                         xfs_refcount_recover_extent, &debris);
1728         xfs_btree_del_cursor(cur, error);
1729         xfs_trans_brelse(tp, agbp);
1730         xfs_trans_cancel(tp);
1731         if (error)
1732                 goto out_free;
1733
1734         /* Now iterate the list to free the leftovers */
1735         list_for_each_entry_safe(rr, n, &debris, rr_list) {
1736                 /* Set up transaction. */
1737                 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1738                 if (error)
1739                         goto out_free;
1740
1741                 trace_xfs_refcount_recover_extent(mp, agno, &rr->rr_rrec);
1742
1743                 /* Free the orphan record */
1744                 agbno = rr->rr_rrec.rc_startblock - XFS_REFC_COW_START;
1745                 fsb = XFS_AGB_TO_FSB(mp, agno, agbno);
1746                 xfs_refcount_free_cow_extent(tp, fsb,
1747                                 rr->rr_rrec.rc_blockcount);
1748
1749                 /* Free the block. */
1750                 xfs_bmap_add_free(tp, fsb, rr->rr_rrec.rc_blockcount, NULL);
1751
1752                 error = xfs_trans_commit(tp);
1753                 if (error)
1754                         goto out_free;
1755
1756                 list_del(&rr->rr_list);
1757                 kmem_free(rr);
1758         }
1759
1760         return error;
1761 out_trans:
1762         xfs_trans_cancel(tp);
1763 out_free:
1764         /* Free the leftover list */
1765         list_for_each_entry_safe(rr, n, &debris, rr_list) {
1766                 list_del(&rr->rr_list);
1767                 kmem_free(rr);
1768         }
1769         return error;
1770 }
1771
1772 /* Is there a record covering a given extent? */
1773 int
1774 xfs_refcount_has_record(
1775         struct xfs_btree_cur    *cur,
1776         xfs_agblock_t           bno,
1777         xfs_extlen_t            len,
1778         bool                    *exists)
1779 {
1780         union xfs_btree_irec    low;
1781         union xfs_btree_irec    high;
1782
1783         memset(&low, 0, sizeof(low));
1784         low.rc.rc_startblock = bno;
1785         memset(&high, 0xFF, sizeof(high));
1786         high.rc.rc_startblock = bno + len - 1;
1787
1788         return xfs_btree_has_record(cur, &low, &high, exists);
1789 }