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