linux/fs/xfs/libxfs/xfs_refcount.c
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   1// SPDX-License-Identifier: GPL-2.0+
   2/*
   3 * Copyright (C) 2016 Oracle.  All Rights Reserved.
   4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
   5 */
   6#include "xfs.h"
   7#include "xfs_fs.h"
   8#include "xfs_shared.h"
   9#include "xfs_format.h"
  10#include "xfs_log_format.h"
  11#include "xfs_trans_resv.h"
  12#include "xfs_mount.h"
  13#include "xfs_defer.h"
  14#include "xfs_btree.h"
  15#include "xfs_bmap.h"
  16#include "xfs_refcount_btree.h"
  17#include "xfs_alloc.h"
  18#include "xfs_errortag.h"
  19#include "xfs_error.h"
  20#include "xfs_trace.h"
  21#include "xfs_trans.h"
  22#include "xfs_bit.h"
  23#include "xfs_refcount.h"
  24#include "xfs_rmap.h"
  25#include "xfs_ag.h"
  26
  27/* Allowable refcount adjustment amounts. */
  28enum xfs_refc_adjust_op {
  29        XFS_REFCOUNT_ADJUST_INCREASE    = 1,
  30        XFS_REFCOUNT_ADJUST_DECREASE    = -1,
  31        XFS_REFCOUNT_ADJUST_COW_ALLOC   = 0,
  32        XFS_REFCOUNT_ADJUST_COW_FREE    = -1,
  33};
  34
  35STATIC int __xfs_refcount_cow_alloc(struct xfs_btree_cur *rcur,
  36                xfs_agblock_t agbno, xfs_extlen_t aglen);
  37STATIC int __xfs_refcount_cow_free(struct xfs_btree_cur *rcur,
  38                xfs_agblock_t agbno, xfs_extlen_t aglen);
  39
  40/*
  41 * Look up the first record less than or equal to [bno, len] in the btree
  42 * given by cur.
  43 */
  44int
  45xfs_refcount_lookup_le(
  46        struct xfs_btree_cur    *cur,
  47        xfs_agblock_t           bno,
  48        int                     *stat)
  49{
  50        trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_ag.pag->pag_agno, bno,
  51                        XFS_LOOKUP_LE);
  52        cur->bc_rec.rc.rc_startblock = bno;
  53        cur->bc_rec.rc.rc_blockcount = 0;
  54        return xfs_btree_lookup(cur, XFS_LOOKUP_LE, stat);
  55}
  56
  57/*
  58 * Look up the first record greater than or equal to [bno, len] in the btree
  59 * given by cur.
  60 */
  61int
  62xfs_refcount_lookup_ge(
  63        struct xfs_btree_cur    *cur,
  64        xfs_agblock_t           bno,
  65        int                     *stat)
  66{
  67        trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_ag.pag->pag_agno, bno,
  68                        XFS_LOOKUP_GE);
  69        cur->bc_rec.rc.rc_startblock = bno;
  70        cur->bc_rec.rc.rc_blockcount = 0;
  71        return xfs_btree_lookup(cur, XFS_LOOKUP_GE, stat);
  72}
  73
  74/*
  75 * Look up the first record equal to [bno, len] in the btree
  76 * given by cur.
  77 */
  78int
  79xfs_refcount_lookup_eq(
  80        struct xfs_btree_cur    *cur,
  81        xfs_agblock_t           bno,
  82        int                     *stat)
  83{
  84        trace_xfs_refcount_lookup(cur->bc_mp, cur->bc_ag.pag->pag_agno, bno,
  85                        XFS_LOOKUP_LE);
  86        cur->bc_rec.rc.rc_startblock = bno;
  87        cur->bc_rec.rc.rc_blockcount = 0;
  88        return xfs_btree_lookup(cur, XFS_LOOKUP_EQ, stat);
  89}
  90
  91/* Convert on-disk record to in-core format. */
  92void
  93xfs_refcount_btrec_to_irec(
  94        union xfs_btree_rec             *rec,
  95        struct xfs_refcount_irec        *irec)
  96{
  97        irec->rc_startblock = be32_to_cpu(rec->refc.rc_startblock);
  98        irec->rc_blockcount = be32_to_cpu(rec->refc.rc_blockcount);
  99        irec->rc_refcount = be32_to_cpu(rec->refc.rc_refcount);
 100}
 101
 102/*
 103 * Get the data from the pointed-to record.
 104 */
 105int
 106xfs_refcount_get_rec(
 107        struct xfs_btree_cur            *cur,
 108        struct xfs_refcount_irec        *irec,
 109        int                             *stat)
 110{
 111        struct xfs_mount                *mp = cur->bc_mp;
 112        xfs_agnumber_t                  agno = cur->bc_ag.pag->pag_agno;
 113        union xfs_btree_rec             *rec;
 114        int                             error;
 115        xfs_agblock_t                   realstart;
 116
 117        error = xfs_btree_get_rec(cur, &rec, stat);
 118        if (error || !*stat)
 119                return error;
 120
 121        xfs_refcount_btrec_to_irec(rec, irec);
 122
 123        agno = cur->bc_ag.pag->pag_agno;
 124        if (irec->rc_blockcount == 0 || irec->rc_blockcount > MAXREFCEXTLEN)
 125                goto out_bad_rec;
 126
 127        /* handle special COW-staging state */
 128        realstart = irec->rc_startblock;
 129        if (realstart & XFS_REFC_COW_START) {
 130                if (irec->rc_refcount != 1)
 131                        goto out_bad_rec;
 132                realstart &= ~XFS_REFC_COW_START;
 133        } else if (irec->rc_refcount < 2) {
 134                goto out_bad_rec;
 135        }
 136
 137        /* check for valid extent range, including overflow */
 138        if (!xfs_verify_agbno(mp, agno, realstart))
 139                goto out_bad_rec;
 140        if (realstart > realstart + irec->rc_blockcount)
 141                goto out_bad_rec;
 142        if (!xfs_verify_agbno(mp, agno, realstart + irec->rc_blockcount - 1))
 143                goto out_bad_rec;
 144
 145        if (irec->rc_refcount == 0 || irec->rc_refcount > MAXREFCOUNT)
 146                goto out_bad_rec;
 147
 148        trace_xfs_refcount_get(cur->bc_mp, cur->bc_ag.pag->pag_agno, irec);
 149        return 0;
 150
 151out_bad_rec:
 152        xfs_warn(mp,
 153                "Refcount BTree record corruption in AG %d detected!", agno);
 154        xfs_warn(mp,
 155                "Start block 0x%x, block count 0x%x, references 0x%x",
 156                irec->rc_startblock, irec->rc_blockcount, irec->rc_refcount);
 157        return -EFSCORRUPTED;
 158}
 159
 160/*
 161 * Update the record referred to by cur to the value given
 162 * by [bno, len, refcount].
 163 * This either works (return 0) or gets an EFSCORRUPTED error.
 164 */
 165STATIC int
 166xfs_refcount_update(
 167        struct xfs_btree_cur            *cur,
 168        struct xfs_refcount_irec        *irec)
 169{
 170        union xfs_btree_rec     rec;
 171        int                     error;
 172
 173        trace_xfs_refcount_update(cur->bc_mp, cur->bc_ag.pag->pag_agno, irec);
 174        rec.refc.rc_startblock = cpu_to_be32(irec->rc_startblock);
 175        rec.refc.rc_blockcount = cpu_to_be32(irec->rc_blockcount);
 176        rec.refc.rc_refcount = cpu_to_be32(irec->rc_refcount);
 177        error = xfs_btree_update(cur, &rec);
 178        if (error)
 179                trace_xfs_refcount_update_error(cur->bc_mp,
 180                                cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 181        return error;
 182}
 183
 184/*
 185 * Insert the record referred to by cur to the value given
 186 * by [bno, len, refcount].
 187 * This either works (return 0) or gets an EFSCORRUPTED error.
 188 */
 189int
 190xfs_refcount_insert(
 191        struct xfs_btree_cur            *cur,
 192        struct xfs_refcount_irec        *irec,
 193        int                             *i)
 194{
 195        int                             error;
 196
 197        trace_xfs_refcount_insert(cur->bc_mp, cur->bc_ag.pag->pag_agno, irec);
 198        cur->bc_rec.rc.rc_startblock = irec->rc_startblock;
 199        cur->bc_rec.rc.rc_blockcount = irec->rc_blockcount;
 200        cur->bc_rec.rc.rc_refcount = irec->rc_refcount;
 201        error = xfs_btree_insert(cur, i);
 202        if (error)
 203                goto out_error;
 204        if (XFS_IS_CORRUPT(cur->bc_mp, *i != 1)) {
 205                error = -EFSCORRUPTED;
 206                goto out_error;
 207        }
 208
 209out_error:
 210        if (error)
 211                trace_xfs_refcount_insert_error(cur->bc_mp,
 212                                cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 213        return error;
 214}
 215
 216/*
 217 * Remove the record referred to by cur, then set the pointer to the spot
 218 * where the record could be re-inserted, in case we want to increment or
 219 * decrement the cursor.
 220 * This either works (return 0) or gets an EFSCORRUPTED error.
 221 */
 222STATIC int
 223xfs_refcount_delete(
 224        struct xfs_btree_cur    *cur,
 225        int                     *i)
 226{
 227        struct xfs_refcount_irec        irec;
 228        int                     found_rec;
 229        int                     error;
 230
 231        error = xfs_refcount_get_rec(cur, &irec, &found_rec);
 232        if (error)
 233                goto out_error;
 234        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 235                error = -EFSCORRUPTED;
 236                goto out_error;
 237        }
 238        trace_xfs_refcount_delete(cur->bc_mp, cur->bc_ag.pag->pag_agno, &irec);
 239        error = xfs_btree_delete(cur, i);
 240        if (XFS_IS_CORRUPT(cur->bc_mp, *i != 1)) {
 241                error = -EFSCORRUPTED;
 242                goto out_error;
 243        }
 244        if (error)
 245                goto out_error;
 246        error = xfs_refcount_lookup_ge(cur, irec.rc_startblock, &found_rec);
 247out_error:
 248        if (error)
 249                trace_xfs_refcount_delete_error(cur->bc_mp,
 250                                cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 251        return error;
 252}
 253
 254/*
 255 * Adjusting the Reference Count
 256 *
 257 * As stated elsewhere, the reference count btree (refcbt) stores
 258 * >1 reference counts for extents of physical blocks.  In this
 259 * operation, we're either raising or lowering the reference count of
 260 * some subrange stored in the tree:
 261 *
 262 *      <------ adjustment range ------>
 263 * ----+   +---+-----+ +--+--------+---------
 264 *  2  |   | 3 |  4  | |17|   55   |   10
 265 * ----+   +---+-----+ +--+--------+---------
 266 * X axis is physical blocks number;
 267 * reference counts are the numbers inside the rectangles
 268 *
 269 * The first thing we need to do is to ensure that there are no
 270 * refcount extents crossing either boundary of the range to be
 271 * adjusted.  For any extent that does cross a boundary, split it into
 272 * two extents so that we can increment the refcount of one of the
 273 * pieces later:
 274 *
 275 *      <------ adjustment range ------>
 276 * ----+   +---+-----+ +--+--------+----+----
 277 *  2  |   | 3 |  2  | |17|   55   | 10 | 10
 278 * ----+   +---+-----+ +--+--------+----+----
 279 *
 280 * For this next step, let's assume that all the physical blocks in
 281 * the adjustment range are mapped to a file and are therefore in use
 282 * at least once.  Therefore, we can infer that any gap in the
 283 * refcount tree within the adjustment range represents a physical
 284 * extent with refcount == 1:
 285 *
 286 *      <------ adjustment range ------>
 287 * ----+---+---+-----+-+--+--------+----+----
 288 *  2  |"1"| 3 |  2  |1|17|   55   | 10 | 10
 289 * ----+---+---+-----+-+--+--------+----+----
 290 *      ^
 291 *
 292 * For each extent that falls within the interval range, figure out
 293 * which extent is to the left or the right of that extent.  Now we
 294 * have a left, current, and right extent.  If the new reference count
 295 * of the center extent enables us to merge left, center, and right
 296 * into one record covering all three, do so.  If the center extent is
 297 * at the left end of the range, abuts the left extent, and its new
 298 * reference count matches the left extent's record, then merge them.
 299 * If the center extent is at the right end of the range, abuts the
 300 * right extent, and the reference counts match, merge those.  In the
 301 * example, we can left merge (assuming an increment operation):
 302 *
 303 *      <------ adjustment range ------>
 304 * --------+---+-----+-+--+--------+----+----
 305 *    2    | 3 |  2  |1|17|   55   | 10 | 10
 306 * --------+---+-----+-+--+--------+----+----
 307 *          ^
 308 *
 309 * For all other extents within the range, adjust the reference count
 310 * or delete it if the refcount falls below 2.  If we were
 311 * incrementing, the end result looks like this:
 312 *
 313 *      <------ adjustment range ------>
 314 * --------+---+-----+-+--+--------+----+----
 315 *    2    | 4 |  3  |2|18|   56   | 11 | 10
 316 * --------+---+-----+-+--+--------+----+----
 317 *
 318 * The result of a decrement operation looks as such:
 319 *
 320 *      <------ adjustment range ------>
 321 * ----+   +---+       +--+--------+----+----
 322 *  2  |   | 2 |       |16|   54   |  9 | 10
 323 * ----+   +---+       +--+--------+----+----
 324 *      DDDD    111111DD
 325 *
 326 * The blocks marked "D" are freed; the blocks marked "1" are only
 327 * referenced once and therefore the record is removed from the
 328 * refcount btree.
 329 */
 330
 331/* Next block after this extent. */
 332static inline xfs_agblock_t
 333xfs_refc_next(
 334        struct xfs_refcount_irec        *rc)
 335{
 336        return rc->rc_startblock + rc->rc_blockcount;
 337}
 338
 339/*
 340 * Split a refcount extent that crosses agbno.
 341 */
 342STATIC int
 343xfs_refcount_split_extent(
 344        struct xfs_btree_cur            *cur,
 345        xfs_agblock_t                   agbno,
 346        bool                            *shape_changed)
 347{
 348        struct xfs_refcount_irec        rcext, tmp;
 349        int                             found_rec;
 350        int                             error;
 351
 352        *shape_changed = false;
 353        error = xfs_refcount_lookup_le(cur, agbno, &found_rec);
 354        if (error)
 355                goto out_error;
 356        if (!found_rec)
 357                return 0;
 358
 359        error = xfs_refcount_get_rec(cur, &rcext, &found_rec);
 360        if (error)
 361                goto out_error;
 362        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 363                error = -EFSCORRUPTED;
 364                goto out_error;
 365        }
 366        if (rcext.rc_startblock == agbno || xfs_refc_next(&rcext) <= agbno)
 367                return 0;
 368
 369        *shape_changed = true;
 370        trace_xfs_refcount_split_extent(cur->bc_mp, cur->bc_ag.pag->pag_agno,
 371                        &rcext, agbno);
 372
 373        /* Establish the right extent. */
 374        tmp = rcext;
 375        tmp.rc_startblock = agbno;
 376        tmp.rc_blockcount -= (agbno - rcext.rc_startblock);
 377        error = xfs_refcount_update(cur, &tmp);
 378        if (error)
 379                goto out_error;
 380
 381        /* Insert the left extent. */
 382        tmp = rcext;
 383        tmp.rc_blockcount = agbno - rcext.rc_startblock;
 384        error = xfs_refcount_insert(cur, &tmp, &found_rec);
 385        if (error)
 386                goto out_error;
 387        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 388                error = -EFSCORRUPTED;
 389                goto out_error;
 390        }
 391        return error;
 392
 393out_error:
 394        trace_xfs_refcount_split_extent_error(cur->bc_mp,
 395                        cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 396        return error;
 397}
 398
 399/*
 400 * Merge the left, center, and right extents.
 401 */
 402STATIC int
 403xfs_refcount_merge_center_extents(
 404        struct xfs_btree_cur            *cur,
 405        struct xfs_refcount_irec        *left,
 406        struct xfs_refcount_irec        *center,
 407        struct xfs_refcount_irec        *right,
 408        unsigned long long              extlen,
 409        xfs_extlen_t                    *aglen)
 410{
 411        int                             error;
 412        int                             found_rec;
 413
 414        trace_xfs_refcount_merge_center_extents(cur->bc_mp,
 415                        cur->bc_ag.pag->pag_agno, left, center, right);
 416
 417        /*
 418         * Make sure the center and right extents are not in the btree.
 419         * If the center extent was synthesized, the first delete call
 420         * removes the right extent and we skip the second deletion.
 421         * If center and right were in the btree, then the first delete
 422         * call removes the center and the second one removes the right
 423         * extent.
 424         */
 425        error = xfs_refcount_lookup_ge(cur, center->rc_startblock,
 426                        &found_rec);
 427        if (error)
 428                goto out_error;
 429        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 430                error = -EFSCORRUPTED;
 431                goto out_error;
 432        }
 433
 434        error = xfs_refcount_delete(cur, &found_rec);
 435        if (error)
 436                goto out_error;
 437        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 438                error = -EFSCORRUPTED;
 439                goto out_error;
 440        }
 441
 442        if (center->rc_refcount > 1) {
 443                error = xfs_refcount_delete(cur, &found_rec);
 444                if (error)
 445                        goto out_error;
 446                if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 447                        error = -EFSCORRUPTED;
 448                        goto out_error;
 449                }
 450        }
 451
 452        /* Enlarge the left extent. */
 453        error = xfs_refcount_lookup_le(cur, left->rc_startblock,
 454                        &found_rec);
 455        if (error)
 456                goto out_error;
 457        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 458                error = -EFSCORRUPTED;
 459                goto out_error;
 460        }
 461
 462        left->rc_blockcount = extlen;
 463        error = xfs_refcount_update(cur, left);
 464        if (error)
 465                goto out_error;
 466
 467        *aglen = 0;
 468        return error;
 469
 470out_error:
 471        trace_xfs_refcount_merge_center_extents_error(cur->bc_mp,
 472                        cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 473        return error;
 474}
 475
 476/*
 477 * Merge with the left extent.
 478 */
 479STATIC int
 480xfs_refcount_merge_left_extent(
 481        struct xfs_btree_cur            *cur,
 482        struct xfs_refcount_irec        *left,
 483        struct xfs_refcount_irec        *cleft,
 484        xfs_agblock_t                   *agbno,
 485        xfs_extlen_t                    *aglen)
 486{
 487        int                             error;
 488        int                             found_rec;
 489
 490        trace_xfs_refcount_merge_left_extent(cur->bc_mp,
 491                        cur->bc_ag.pag->pag_agno, left, cleft);
 492
 493        /* If the extent at agbno (cleft) wasn't synthesized, remove it. */
 494        if (cleft->rc_refcount > 1) {
 495                error = xfs_refcount_lookup_le(cur, cleft->rc_startblock,
 496                                &found_rec);
 497                if (error)
 498                        goto out_error;
 499                if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 500                        error = -EFSCORRUPTED;
 501                        goto out_error;
 502                }
 503
 504                error = xfs_refcount_delete(cur, &found_rec);
 505                if (error)
 506                        goto out_error;
 507                if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 508                        error = -EFSCORRUPTED;
 509                        goto out_error;
 510                }
 511        }
 512
 513        /* Enlarge the left extent. */
 514        error = xfs_refcount_lookup_le(cur, left->rc_startblock,
 515                        &found_rec);
 516        if (error)
 517                goto out_error;
 518        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 519                error = -EFSCORRUPTED;
 520                goto out_error;
 521        }
 522
 523        left->rc_blockcount += cleft->rc_blockcount;
 524        error = xfs_refcount_update(cur, left);
 525        if (error)
 526                goto out_error;
 527
 528        *agbno += cleft->rc_blockcount;
 529        *aglen -= cleft->rc_blockcount;
 530        return error;
 531
 532out_error:
 533        trace_xfs_refcount_merge_left_extent_error(cur->bc_mp,
 534                        cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 535        return error;
 536}
 537
 538/*
 539 * Merge with the right extent.
 540 */
 541STATIC int
 542xfs_refcount_merge_right_extent(
 543        struct xfs_btree_cur            *cur,
 544        struct xfs_refcount_irec        *right,
 545        struct xfs_refcount_irec        *cright,
 546        xfs_extlen_t                    *aglen)
 547{
 548        int                             error;
 549        int                             found_rec;
 550
 551        trace_xfs_refcount_merge_right_extent(cur->bc_mp,
 552                        cur->bc_ag.pag->pag_agno, cright, right);
 553
 554        /*
 555         * If the extent ending at agbno+aglen (cright) wasn't synthesized,
 556         * remove it.
 557         */
 558        if (cright->rc_refcount > 1) {
 559                error = xfs_refcount_lookup_le(cur, cright->rc_startblock,
 560                        &found_rec);
 561                if (error)
 562                        goto out_error;
 563                if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 564                        error = -EFSCORRUPTED;
 565                        goto out_error;
 566                }
 567
 568                error = xfs_refcount_delete(cur, &found_rec);
 569                if (error)
 570                        goto out_error;
 571                if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 572                        error = -EFSCORRUPTED;
 573                        goto out_error;
 574                }
 575        }
 576
 577        /* Enlarge the right extent. */
 578        error = xfs_refcount_lookup_le(cur, right->rc_startblock,
 579                        &found_rec);
 580        if (error)
 581                goto out_error;
 582        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 583                error = -EFSCORRUPTED;
 584                goto out_error;
 585        }
 586
 587        right->rc_startblock -= cright->rc_blockcount;
 588        right->rc_blockcount += cright->rc_blockcount;
 589        error = xfs_refcount_update(cur, right);
 590        if (error)
 591                goto out_error;
 592
 593        *aglen -= cright->rc_blockcount;
 594        return error;
 595
 596out_error:
 597        trace_xfs_refcount_merge_right_extent_error(cur->bc_mp,
 598                        cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 599        return error;
 600}
 601
 602#define XFS_FIND_RCEXT_SHARED   1
 603#define XFS_FIND_RCEXT_COW      2
 604/*
 605 * Find the left extent and the one after it (cleft).  This function assumes
 606 * that we've already split any extent crossing agbno.
 607 */
 608STATIC int
 609xfs_refcount_find_left_extents(
 610        struct xfs_btree_cur            *cur,
 611        struct xfs_refcount_irec        *left,
 612        struct xfs_refcount_irec        *cleft,
 613        xfs_agblock_t                   agbno,
 614        xfs_extlen_t                    aglen,
 615        int                             flags)
 616{
 617        struct xfs_refcount_irec        tmp;
 618        int                             error;
 619        int                             found_rec;
 620
 621        left->rc_startblock = cleft->rc_startblock = NULLAGBLOCK;
 622        error = xfs_refcount_lookup_le(cur, agbno - 1, &found_rec);
 623        if (error)
 624                goto out_error;
 625        if (!found_rec)
 626                return 0;
 627
 628        error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 629        if (error)
 630                goto out_error;
 631        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 632                error = -EFSCORRUPTED;
 633                goto out_error;
 634        }
 635
 636        if (xfs_refc_next(&tmp) != agbno)
 637                return 0;
 638        if ((flags & XFS_FIND_RCEXT_SHARED) && tmp.rc_refcount < 2)
 639                return 0;
 640        if ((flags & XFS_FIND_RCEXT_COW) && tmp.rc_refcount > 1)
 641                return 0;
 642        /* We have a left extent; retrieve (or invent) the next right one */
 643        *left = tmp;
 644
 645        error = xfs_btree_increment(cur, 0, &found_rec);
 646        if (error)
 647                goto out_error;
 648        if (found_rec) {
 649                error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 650                if (error)
 651                        goto out_error;
 652                if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 653                        error = -EFSCORRUPTED;
 654                        goto out_error;
 655                }
 656
 657                /* if tmp starts at the end of our range, just use that */
 658                if (tmp.rc_startblock == agbno)
 659                        *cleft = tmp;
 660                else {
 661                        /*
 662                         * There's a gap in the refcntbt at the start of the
 663                         * range we're interested in (refcount == 1) so
 664                         * synthesize the implied extent and pass it back.
 665                         * We assume here that the agbno/aglen range was
 666                         * passed in from a data fork extent mapping and
 667                         * therefore is allocated to exactly one owner.
 668                         */
 669                        cleft->rc_startblock = agbno;
 670                        cleft->rc_blockcount = min(aglen,
 671                                        tmp.rc_startblock - agbno);
 672                        cleft->rc_refcount = 1;
 673                }
 674        } else {
 675                /*
 676                 * No extents, so pretend that there's one covering the whole
 677                 * range.
 678                 */
 679                cleft->rc_startblock = agbno;
 680                cleft->rc_blockcount = aglen;
 681                cleft->rc_refcount = 1;
 682        }
 683        trace_xfs_refcount_find_left_extent(cur->bc_mp, cur->bc_ag.pag->pag_agno,
 684                        left, cleft, agbno);
 685        return error;
 686
 687out_error:
 688        trace_xfs_refcount_find_left_extent_error(cur->bc_mp,
 689                        cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 690        return error;
 691}
 692
 693/*
 694 * Find the right extent and the one before it (cright).  This function
 695 * assumes that we've already split any extents crossing agbno + aglen.
 696 */
 697STATIC int
 698xfs_refcount_find_right_extents(
 699        struct xfs_btree_cur            *cur,
 700        struct xfs_refcount_irec        *right,
 701        struct xfs_refcount_irec        *cright,
 702        xfs_agblock_t                   agbno,
 703        xfs_extlen_t                    aglen,
 704        int                             flags)
 705{
 706        struct xfs_refcount_irec        tmp;
 707        int                             error;
 708        int                             found_rec;
 709
 710        right->rc_startblock = cright->rc_startblock = NULLAGBLOCK;
 711        error = xfs_refcount_lookup_ge(cur, agbno + aglen, &found_rec);
 712        if (error)
 713                goto out_error;
 714        if (!found_rec)
 715                return 0;
 716
 717        error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 718        if (error)
 719                goto out_error;
 720        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 721                error = -EFSCORRUPTED;
 722                goto out_error;
 723        }
 724
 725        if (tmp.rc_startblock != agbno + aglen)
 726                return 0;
 727        if ((flags & XFS_FIND_RCEXT_SHARED) && tmp.rc_refcount < 2)
 728                return 0;
 729        if ((flags & XFS_FIND_RCEXT_COW) && tmp.rc_refcount > 1)
 730                return 0;
 731        /* We have a right extent; retrieve (or invent) the next left one */
 732        *right = tmp;
 733
 734        error = xfs_btree_decrement(cur, 0, &found_rec);
 735        if (error)
 736                goto out_error;
 737        if (found_rec) {
 738                error = xfs_refcount_get_rec(cur, &tmp, &found_rec);
 739                if (error)
 740                        goto out_error;
 741                if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
 742                        error = -EFSCORRUPTED;
 743                        goto out_error;
 744                }
 745
 746                /* if tmp ends at the end of our range, just use that */
 747                if (xfs_refc_next(&tmp) == agbno + aglen)
 748                        *cright = tmp;
 749                else {
 750                        /*
 751                         * There's a gap in the refcntbt at the end of the
 752                         * range we're interested in (refcount == 1) so
 753                         * create the implied extent and pass it back.
 754                         * We assume here that the agbno/aglen range was
 755                         * passed in from a data fork extent mapping and
 756                         * therefore is allocated to exactly one owner.
 757                         */
 758                        cright->rc_startblock = max(agbno, xfs_refc_next(&tmp));
 759                        cright->rc_blockcount = right->rc_startblock -
 760                                        cright->rc_startblock;
 761                        cright->rc_refcount = 1;
 762                }
 763        } else {
 764                /*
 765                 * No extents, so pretend that there's one covering the whole
 766                 * range.
 767                 */
 768                cright->rc_startblock = agbno;
 769                cright->rc_blockcount = aglen;
 770                cright->rc_refcount = 1;
 771        }
 772        trace_xfs_refcount_find_right_extent(cur->bc_mp, cur->bc_ag.pag->pag_agno,
 773                        cright, right, agbno + aglen);
 774        return error;
 775
 776out_error:
 777        trace_xfs_refcount_find_right_extent_error(cur->bc_mp,
 778                        cur->bc_ag.pag->pag_agno, error, _RET_IP_);
 779        return error;
 780}
 781
 782/* Is this extent valid? */
 783static inline bool
 784xfs_refc_valid(
 785        struct xfs_refcount_irec        *rc)
 786{
 787        return rc->rc_startblock != NULLAGBLOCK;
 788}
 789
 790/*
 791 * Try to merge with any extents on the boundaries of the adjustment range.
 792 */
 793STATIC int
 794xfs_refcount_merge_extents(
 795        struct xfs_btree_cur    *cur,
 796        xfs_agblock_t           *agbno,
 797        xfs_extlen_t            *aglen,
 798        enum xfs_refc_adjust_op adjust,
 799        int                     flags,
 800        bool                    *shape_changed)
 801{
 802        struct xfs_refcount_irec        left = {0}, cleft = {0};
 803        struct xfs_refcount_irec        cright = {0}, right = {0};
 804        int                             error;
 805        unsigned long long              ulen;
 806        bool                            cequal;
 807
 808        *shape_changed = false;
 809        /*
 810         * Find the extent just below agbno [left], just above agbno [cleft],
 811         * just below (agbno + aglen) [cright], and just above (agbno + aglen)
 812         * [right].
 813         */
 814        error = xfs_refcount_find_left_extents(cur, &left, &cleft, *agbno,
 815                        *aglen, flags);
 816        if (error)
 817                return error;
 818        error = xfs_refcount_find_right_extents(cur, &right, &cright, *agbno,
 819                        *aglen, flags);
 820        if (error)
 821                return error;
 822
 823        /* No left or right extent to merge; exit. */
 824        if (!xfs_refc_valid(&left) && !xfs_refc_valid(&right))
 825                return 0;
 826
 827        cequal = (cleft.rc_startblock == cright.rc_startblock) &&
 828                 (cleft.rc_blockcount == cright.rc_blockcount);
 829
 830        /* Try to merge left, cleft, and right.  cleft must == cright. */
 831        ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount +
 832                        right.rc_blockcount;
 833        if (xfs_refc_valid(&left) && xfs_refc_valid(&right) &&
 834            xfs_refc_valid(&cleft) && xfs_refc_valid(&cright) && cequal &&
 835            left.rc_refcount == cleft.rc_refcount + adjust &&
 836            right.rc_refcount == cleft.rc_refcount + adjust &&
 837            ulen < MAXREFCEXTLEN) {
 838                *shape_changed = true;
 839                return xfs_refcount_merge_center_extents(cur, &left, &cleft,
 840                                &right, ulen, aglen);
 841        }
 842
 843        /* Try to merge left and cleft. */
 844        ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount;
 845        if (xfs_refc_valid(&left) && xfs_refc_valid(&cleft) &&
 846            left.rc_refcount == cleft.rc_refcount + adjust &&
 847            ulen < MAXREFCEXTLEN) {
 848                *shape_changed = true;
 849                error = xfs_refcount_merge_left_extent(cur, &left, &cleft,
 850                                agbno, aglen);
 851                if (error)
 852                        return error;
 853
 854                /*
 855                 * If we just merged left + cleft and cleft == cright,
 856                 * we no longer have a cright to merge with right.  We're done.
 857                 */
 858                if (cequal)
 859                        return 0;
 860        }
 861
 862        /* Try to merge cright and right. */
 863        ulen = (unsigned long long)right.rc_blockcount + cright.rc_blockcount;
 864        if (xfs_refc_valid(&right) && xfs_refc_valid(&cright) &&
 865            right.rc_refcount == cright.rc_refcount + adjust &&
 866            ulen < MAXREFCEXTLEN) {
 867                *shape_changed = true;
 868                return xfs_refcount_merge_right_extent(cur, &right, &cright,
 869                                aglen);
 870        }
 871
 872        return error;
 873}
 874
 875/*
 876 * XXX: This is a pretty hand-wavy estimate.  The penalty for guessing
 877 * true incorrectly is a shutdown FS; the penalty for guessing false
 878 * incorrectly is more transaction rolls than might be necessary.
 879 * Be conservative here.
 880 */
 881static bool
 882xfs_refcount_still_have_space(
 883        struct xfs_btree_cur            *cur)
 884{
 885        unsigned long                   overhead;
 886
 887        overhead = cur->bc_ag.refc.shape_changes *
 888                        xfs_allocfree_log_count(cur->bc_mp, 1);
 889        overhead *= cur->bc_mp->m_sb.sb_blocksize;
 890
 891        /*
 892         * Only allow 2 refcount extent updates per transaction if the
 893         * refcount continue update "error" has been injected.
 894         */
 895        if (cur->bc_ag.refc.nr_ops > 2 &&
 896            XFS_TEST_ERROR(false, cur->bc_mp,
 897                        XFS_ERRTAG_REFCOUNT_CONTINUE_UPDATE))
 898                return false;
 899
 900        if (cur->bc_ag.refc.nr_ops == 0)
 901                return true;
 902        else if (overhead > cur->bc_tp->t_log_res)
 903                return false;
 904        return  cur->bc_tp->t_log_res - overhead >
 905                cur->bc_ag.refc.nr_ops * XFS_REFCOUNT_ITEM_OVERHEAD;
 906}
 907
 908/*
 909 * Adjust the refcounts of middle extents.  At this point we should have
 910 * split extents that crossed the adjustment range; merged with adjacent
 911 * extents; and updated agbno/aglen to reflect the merges.  Therefore,
 912 * all we have to do is update the extents inside [agbno, agbno + aglen].
 913 */
 914STATIC int
 915xfs_refcount_adjust_extents(
 916        struct xfs_btree_cur    *cur,
 917        xfs_agblock_t           *agbno,
 918        xfs_extlen_t            *aglen,
 919        enum xfs_refc_adjust_op adj,
 920        struct xfs_owner_info   *oinfo)
 921{
 922        struct xfs_refcount_irec        ext, tmp;
 923        int                             error;
 924        int                             found_rec, found_tmp;
 925        xfs_fsblock_t                   fsbno;
 926
 927        /* Merging did all the work already. */
 928        if (*aglen == 0)
 929                return 0;
 930
 931        error = xfs_refcount_lookup_ge(cur, *agbno, &found_rec);
 932        if (error)
 933                goto out_error;
 934
 935        while (*aglen > 0 && xfs_refcount_still_have_space(cur)) {
 936                error = xfs_refcount_get_rec(cur, &ext, &found_rec);
 937                if (error)
 938                        goto out_error;
 939                if (!found_rec) {
 940                        ext.rc_startblock = cur->bc_mp->m_sb.sb_agblocks;
 941                        ext.rc_blockcount = 0;
 942                        ext.rc_refcount = 0;
 943                }
 944
 945                /*
 946                 * Deal with a hole in the refcount tree; if a file maps to
 947                 * these blocks and there's no refcountbt record, pretend that
 948                 * there is one with refcount == 1.
 949                 */
 950                if (ext.rc_startblock != *agbno) {
 951                        tmp.rc_startblock = *agbno;
 952                        tmp.rc_blockcount = min(*aglen,
 953                                        ext.rc_startblock - *agbno);
 954                        tmp.rc_refcount = 1 + adj;
 955                        trace_xfs_refcount_modify_extent(cur->bc_mp,
 956                                        cur->bc_ag.pag->pag_agno, &tmp);
 957
 958                        /*
 959                         * Either cover the hole (increment) or
 960                         * delete the range (decrement).
 961                         */
 962                        if (tmp.rc_refcount) {
 963                                error = xfs_refcount_insert(cur, &tmp,
 964                                                &found_tmp);
 965                                if (error)
 966                                        goto out_error;
 967                                if (XFS_IS_CORRUPT(cur->bc_mp,
 968                                                   found_tmp != 1)) {
 969                                        error = -EFSCORRUPTED;
 970                                        goto out_error;
 971                                }
 972                                cur->bc_ag.refc.nr_ops++;
 973                        } else {
 974                                fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
 975                                                cur->bc_ag.pag->pag_agno,
 976                                                tmp.rc_startblock);
 977                                xfs_bmap_add_free(cur->bc_tp, fsbno,
 978                                                  tmp.rc_blockcount, oinfo);
 979                        }
 980
 981                        (*agbno) += tmp.rc_blockcount;
 982                        (*aglen) -= tmp.rc_blockcount;
 983
 984                        error = xfs_refcount_lookup_ge(cur, *agbno,
 985                                        &found_rec);
 986                        if (error)
 987                                goto out_error;
 988                }
 989
 990                /* Stop if there's nothing left to modify */
 991                if (*aglen == 0 || !xfs_refcount_still_have_space(cur))
 992                        break;
 993
 994                /*
 995                 * Adjust the reference count and either update the tree
 996                 * (incr) or free the blocks (decr).
 997                 */
 998                if (ext.rc_refcount == MAXREFCOUNT)
 999                        goto skip;
1000                ext.rc_refcount += adj;
1001                trace_xfs_refcount_modify_extent(cur->bc_mp,
1002                                cur->bc_ag.pag->pag_agno, &ext);
1003                if (ext.rc_refcount > 1) {
1004                        error = xfs_refcount_update(cur, &ext);
1005                        if (error)
1006                                goto out_error;
1007                        cur->bc_ag.refc.nr_ops++;
1008                } else if (ext.rc_refcount == 1) {
1009                        error = xfs_refcount_delete(cur, &found_rec);
1010                        if (error)
1011                                goto out_error;
1012                        if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
1013                                error = -EFSCORRUPTED;
1014                                goto out_error;
1015                        }
1016                        cur->bc_ag.refc.nr_ops++;
1017                        goto advloop;
1018                } else {
1019                        fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
1020                                        cur->bc_ag.pag->pag_agno,
1021                                        ext.rc_startblock);
1022                        xfs_bmap_add_free(cur->bc_tp, fsbno, ext.rc_blockcount,
1023                                          oinfo);
1024                }
1025
1026skip:
1027                error = xfs_btree_increment(cur, 0, &found_rec);
1028                if (error)
1029                        goto out_error;
1030
1031advloop:
1032                (*agbno) += ext.rc_blockcount;
1033                (*aglen) -= ext.rc_blockcount;
1034        }
1035
1036        return error;
1037out_error:
1038        trace_xfs_refcount_modify_extent_error(cur->bc_mp,
1039                        cur->bc_ag.pag->pag_agno, error, _RET_IP_);
1040        return error;
1041}
1042
1043/* Adjust the reference count of a range of AG blocks. */
1044STATIC int
1045xfs_refcount_adjust(
1046        struct xfs_btree_cur    *cur,
1047        xfs_agblock_t           agbno,
1048        xfs_extlen_t            aglen,
1049        xfs_agblock_t           *new_agbno,
1050        xfs_extlen_t            *new_aglen,
1051        enum xfs_refc_adjust_op adj,
1052        struct xfs_owner_info   *oinfo)
1053{
1054        bool                    shape_changed;
1055        int                     shape_changes = 0;
1056        int                     error;
1057
1058        *new_agbno = agbno;
1059        *new_aglen = aglen;
1060        if (adj == XFS_REFCOUNT_ADJUST_INCREASE)
1061                trace_xfs_refcount_increase(cur->bc_mp, cur->bc_ag.pag->pag_agno,
1062                                agbno, aglen);
1063        else
1064                trace_xfs_refcount_decrease(cur->bc_mp, cur->bc_ag.pag->pag_agno,
1065                                agbno, aglen);
1066
1067        /*
1068         * Ensure that no rcextents cross the boundary of the adjustment range.
1069         */
1070        error = xfs_refcount_split_extent(cur, agbno, &shape_changed);
1071        if (error)
1072                goto out_error;
1073        if (shape_changed)
1074                shape_changes++;
1075
1076        error = xfs_refcount_split_extent(cur, agbno + aglen, &shape_changed);
1077        if (error)
1078                goto out_error;
1079        if (shape_changed)
1080                shape_changes++;
1081
1082        /*
1083         * Try to merge with the left or right extents of the range.
1084         */
1085        error = xfs_refcount_merge_extents(cur, new_agbno, new_aglen, adj,
1086                        XFS_FIND_RCEXT_SHARED, &shape_changed);
1087        if (error)
1088                goto out_error;
1089        if (shape_changed)
1090                shape_changes++;
1091        if (shape_changes)
1092                cur->bc_ag.refc.shape_changes++;
1093
1094        /* Now that we've taken care of the ends, adjust the middle extents */
1095        error = xfs_refcount_adjust_extents(cur, new_agbno, new_aglen,
1096                        adj, oinfo);
1097        if (error)
1098                goto out_error;
1099
1100        return 0;
1101
1102out_error:
1103        trace_xfs_refcount_adjust_error(cur->bc_mp, cur->bc_ag.pag->pag_agno,
1104                        error, _RET_IP_);
1105        return error;
1106}
1107
1108/* Clean up after calling xfs_refcount_finish_one. */
1109void
1110xfs_refcount_finish_one_cleanup(
1111        struct xfs_trans        *tp,
1112        struct xfs_btree_cur    *rcur,
1113        int                     error)
1114{
1115        struct xfs_buf          *agbp;
1116
1117        if (rcur == NULL)
1118                return;
1119        agbp = rcur->bc_ag.agbp;
1120        xfs_btree_del_cursor(rcur, error);
1121        if (error)
1122                xfs_trans_brelse(tp, agbp);
1123}
1124
1125/*
1126 * Process one of the deferred refcount operations.  We pass back the
1127 * btree cursor to maintain our lock on the btree between calls.
1128 * This saves time and eliminates a buffer deadlock between the
1129 * superblock and the AGF because we'll always grab them in the same
1130 * order.
1131 */
1132int
1133xfs_refcount_finish_one(
1134        struct xfs_trans                *tp,
1135        enum xfs_refcount_intent_type   type,
1136        xfs_fsblock_t                   startblock,
1137        xfs_extlen_t                    blockcount,
1138        xfs_fsblock_t                   *new_fsb,
1139        xfs_extlen_t                    *new_len,
1140        struct xfs_btree_cur            **pcur)
1141{
1142        struct xfs_mount                *mp = tp->t_mountp;
1143        struct xfs_btree_cur            *rcur;
1144        struct xfs_buf                  *agbp = NULL;
1145        int                             error = 0;
1146        xfs_agblock_t                   bno;
1147        xfs_agblock_t                   new_agbno;
1148        unsigned long                   nr_ops = 0;
1149        int                             shape_changes = 0;
1150        struct xfs_perag                *pag;
1151
1152        pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, startblock));
1153        bno = XFS_FSB_TO_AGBNO(mp, startblock);
1154
1155        trace_xfs_refcount_deferred(mp, XFS_FSB_TO_AGNO(mp, startblock),
1156                        type, XFS_FSB_TO_AGBNO(mp, startblock),
1157                        blockcount);
1158
1159        if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_REFCOUNT_FINISH_ONE)) {
1160                error = -EIO;
1161                goto out_drop;
1162        }
1163
1164        /*
1165         * If we haven't gotten a cursor or the cursor AG doesn't match
1166         * the startblock, get one now.
1167         */
1168        rcur = *pcur;
1169        if (rcur != NULL && rcur->bc_ag.pag != pag) {
1170                nr_ops = rcur->bc_ag.refc.nr_ops;
1171                shape_changes = rcur->bc_ag.refc.shape_changes;
1172                xfs_refcount_finish_one_cleanup(tp, rcur, 0);
1173                rcur = NULL;
1174                *pcur = NULL;
1175        }
1176        if (rcur == NULL) {
1177                error = xfs_alloc_read_agf(tp->t_mountp, tp, pag->pag_agno,
1178                                XFS_ALLOC_FLAG_FREEING, &agbp);
1179                if (error)
1180                        goto out_drop;
1181
1182                rcur = xfs_refcountbt_init_cursor(mp, tp, agbp, pag);
1183                rcur->bc_ag.refc.nr_ops = nr_ops;
1184                rcur->bc_ag.refc.shape_changes = shape_changes;
1185        }
1186        *pcur = rcur;
1187
1188        switch (type) {
1189        case XFS_REFCOUNT_INCREASE:
1190                error = xfs_refcount_adjust(rcur, bno, blockcount, &new_agbno,
1191                        new_len, XFS_REFCOUNT_ADJUST_INCREASE, NULL);
1192                *new_fsb = XFS_AGB_TO_FSB(mp, pag->pag_agno, new_agbno);
1193                break;
1194        case XFS_REFCOUNT_DECREASE:
1195                error = xfs_refcount_adjust(rcur, bno, blockcount, &new_agbno,
1196                        new_len, XFS_REFCOUNT_ADJUST_DECREASE, NULL);
1197                *new_fsb = XFS_AGB_TO_FSB(mp, pag->pag_agno, new_agbno);
1198                break;
1199        case XFS_REFCOUNT_ALLOC_COW:
1200                *new_fsb = startblock + blockcount;
1201                *new_len = 0;
1202                error = __xfs_refcount_cow_alloc(rcur, bno, blockcount);
1203                break;
1204        case XFS_REFCOUNT_FREE_COW:
1205                *new_fsb = startblock + blockcount;
1206                *new_len = 0;
1207                error = __xfs_refcount_cow_free(rcur, bno, blockcount);
1208                break;
1209        default:
1210                ASSERT(0);
1211                error = -EFSCORRUPTED;
1212        }
1213        if (!error && *new_len > 0)
1214                trace_xfs_refcount_finish_one_leftover(mp, pag->pag_agno, type,
1215                                bno, blockcount, new_agbno, *new_len);
1216out_drop:
1217        xfs_perag_put(pag);
1218        return error;
1219}
1220
1221/*
1222 * Record a refcount intent for later processing.
1223 */
1224static void
1225__xfs_refcount_add(
1226        struct xfs_trans                *tp,
1227        enum xfs_refcount_intent_type   type,
1228        xfs_fsblock_t                   startblock,
1229        xfs_extlen_t                    blockcount)
1230{
1231        struct xfs_refcount_intent      *ri;
1232
1233        trace_xfs_refcount_defer(tp->t_mountp,
1234                        XFS_FSB_TO_AGNO(tp->t_mountp, startblock),
1235                        type, XFS_FSB_TO_AGBNO(tp->t_mountp, startblock),
1236                        blockcount);
1237
1238        ri = kmem_alloc(sizeof(struct xfs_refcount_intent),
1239                        KM_NOFS);
1240        INIT_LIST_HEAD(&ri->ri_list);
1241        ri->ri_type = type;
1242        ri->ri_startblock = startblock;
1243        ri->ri_blockcount = blockcount;
1244
1245        xfs_defer_add(tp, XFS_DEFER_OPS_TYPE_REFCOUNT, &ri->ri_list);
1246}
1247
1248/*
1249 * Increase the reference count of the blocks backing a file's extent.
1250 */
1251void
1252xfs_refcount_increase_extent(
1253        struct xfs_trans                *tp,
1254        struct xfs_bmbt_irec            *PREV)
1255{
1256        if (!xfs_sb_version_hasreflink(&tp->t_mountp->m_sb))
1257                return;
1258
1259        __xfs_refcount_add(tp, XFS_REFCOUNT_INCREASE, PREV->br_startblock,
1260                        PREV->br_blockcount);
1261}
1262
1263/*
1264 * Decrease the reference count of the blocks backing a file's extent.
1265 */
1266void
1267xfs_refcount_decrease_extent(
1268        struct xfs_trans                *tp,
1269        struct xfs_bmbt_irec            *PREV)
1270{
1271        if (!xfs_sb_version_hasreflink(&tp->t_mountp->m_sb))
1272                return;
1273
1274        __xfs_refcount_add(tp, XFS_REFCOUNT_DECREASE, PREV->br_startblock,
1275                        PREV->br_blockcount);
1276}
1277
1278/*
1279 * Given an AG extent, find the lowest-numbered run of shared blocks
1280 * within that range and return the range in fbno/flen.  If
1281 * find_end_of_shared is set, return the longest contiguous extent of
1282 * shared blocks; if not, just return the first extent we find.  If no
1283 * shared blocks are found, fbno and flen will be set to NULLAGBLOCK
1284 * and 0, respectively.
1285 */
1286int
1287xfs_refcount_find_shared(
1288        struct xfs_btree_cur            *cur,
1289        xfs_agblock_t                   agbno,
1290        xfs_extlen_t                    aglen,
1291        xfs_agblock_t                   *fbno,
1292        xfs_extlen_t                    *flen,
1293        bool                            find_end_of_shared)
1294{
1295        struct xfs_refcount_irec        tmp;
1296        int                             i;
1297        int                             have;
1298        int                             error;
1299
1300        trace_xfs_refcount_find_shared(cur->bc_mp, cur->bc_ag.pag->pag_agno,
1301                        agbno, aglen);
1302
1303        /* By default, skip the whole range */
1304        *fbno = NULLAGBLOCK;
1305        *flen = 0;
1306
1307        /* Try to find a refcount extent that crosses the start */
1308        error = xfs_refcount_lookup_le(cur, agbno, &have);
1309        if (error)
1310                goto out_error;
1311        if (!have) {
1312                /* No left extent, look at the next one */
1313                error = xfs_btree_increment(cur, 0, &have);
1314                if (error)
1315                        goto out_error;
1316                if (!have)
1317                        goto done;
1318        }
1319        error = xfs_refcount_get_rec(cur, &tmp, &i);
1320        if (error)
1321                goto out_error;
1322        if (XFS_IS_CORRUPT(cur->bc_mp, i != 1)) {
1323                error = -EFSCORRUPTED;
1324                goto out_error;
1325        }
1326
1327        /* If the extent ends before the start, look at the next one */
1328        if (tmp.rc_startblock + tmp.rc_blockcount <= agbno) {
1329                error = xfs_btree_increment(cur, 0, &have);
1330                if (error)
1331                        goto out_error;
1332                if (!have)
1333                        goto done;
1334                error = xfs_refcount_get_rec(cur, &tmp, &i);
1335                if (error)
1336                        goto out_error;
1337                if (XFS_IS_CORRUPT(cur->bc_mp, i != 1)) {
1338                        error = -EFSCORRUPTED;
1339                        goto out_error;
1340                }
1341        }
1342
1343        /* If the extent starts after the range we want, bail out */
1344        if (tmp.rc_startblock >= agbno + aglen)
1345                goto done;
1346
1347        /* We found the start of a shared extent! */
1348        if (tmp.rc_startblock < agbno) {
1349                tmp.rc_blockcount -= (agbno - tmp.rc_startblock);
1350                tmp.rc_startblock = agbno;
1351        }
1352
1353        *fbno = tmp.rc_startblock;
1354        *flen = min(tmp.rc_blockcount, agbno + aglen - *fbno);
1355        if (!find_end_of_shared)
1356                goto done;
1357
1358        /* Otherwise, find the end of this shared extent */
1359        while (*fbno + *flen < agbno + aglen) {
1360                error = xfs_btree_increment(cur, 0, &have);
1361                if (error)
1362                        goto out_error;
1363                if (!have)
1364                        break;
1365                error = xfs_refcount_get_rec(cur, &tmp, &i);
1366                if (error)
1367                        goto out_error;
1368                if (XFS_IS_CORRUPT(cur->bc_mp, i != 1)) {
1369                        error = -EFSCORRUPTED;
1370                        goto out_error;
1371                }
1372                if (tmp.rc_startblock >= agbno + aglen ||
1373                    tmp.rc_startblock != *fbno + *flen)
1374                        break;
1375                *flen = min(*flen + tmp.rc_blockcount, agbno + aglen - *fbno);
1376        }
1377
1378done:
1379        trace_xfs_refcount_find_shared_result(cur->bc_mp,
1380                        cur->bc_ag.pag->pag_agno, *fbno, *flen);
1381
1382out_error:
1383        if (error)
1384                trace_xfs_refcount_find_shared_error(cur->bc_mp,
1385                                cur->bc_ag.pag->pag_agno, error, _RET_IP_);
1386        return error;
1387}
1388
1389/*
1390 * Recovering CoW Blocks After a Crash
1391 *
1392 * Due to the way that the copy on write mechanism works, there's a window of
1393 * opportunity in which we can lose track of allocated blocks during a crash.
1394 * Because CoW uses delayed allocation in the in-core CoW fork, writeback
1395 * causes blocks to be allocated and stored in the CoW fork.  The blocks are
1396 * no longer in the free space btree but are not otherwise recorded anywhere
1397 * until the write completes and the blocks are mapped into the file.  A crash
1398 * in between allocation and remapping results in the replacement blocks being
1399 * lost.  This situation is exacerbated by the CoW extent size hint because
1400 * allocations can hang around for long time.
1401 *
1402 * However, there is a place where we can record these allocations before they
1403 * become mappings -- the reference count btree.  The btree does not record
1404 * extents with refcount == 1, so we can record allocations with a refcount of
1405 * 1.  Blocks being used for CoW writeout cannot be shared, so there should be
1406 * no conflict with shared block records.  These mappings should be created
1407 * when we allocate blocks to the CoW fork and deleted when they're removed
1408 * from the CoW fork.
1409 *
1410 * Minor nit: records for in-progress CoW allocations and records for shared
1411 * extents must never be merged, to preserve the property that (except for CoW
1412 * allocations) there are no refcount btree entries with refcount == 1.  The
1413 * only time this could potentially happen is when unsharing a block that's
1414 * adjacent to CoW allocations, so we must be careful to avoid this.
1415 *
1416 * At mount time we recover lost CoW allocations by searching the refcount
1417 * btree for these refcount == 1 mappings.  These represent CoW allocations
1418 * that were in progress at the time the filesystem went down, so we can free
1419 * them to get the space back.
1420 *
1421 * This mechanism is superior to creating EFIs for unmapped CoW extents for
1422 * several reasons -- first, EFIs pin the tail of the log and would have to be
1423 * periodically relogged to avoid filling up the log.  Second, CoW completions
1424 * will have to file an EFD and create new EFIs for whatever remains in the
1425 * CoW fork; this partially takes care of (1) but extent-size reservations
1426 * will have to periodically relog even if there's no writeout in progress.
1427 * This can happen if the CoW extent size hint is set, which you really want.
1428 * Third, EFIs cannot currently be automatically relogged into newer
1429 * transactions to advance the log tail.  Fourth, stuffing the log full of
1430 * EFIs places an upper bound on the number of CoW allocations that can be
1431 * held filesystem-wide at any given time.  Recording them in the refcount
1432 * btree doesn't require us to maintain any state in memory and doesn't pin
1433 * the log.
1434 */
1435/*
1436 * Adjust the refcounts of CoW allocations.  These allocations are "magic"
1437 * in that they're not referenced anywhere else in the filesystem, so we
1438 * stash them in the refcount btree with a refcount of 1 until either file
1439 * remapping (or CoW cancellation) happens.
1440 */
1441STATIC int
1442xfs_refcount_adjust_cow_extents(
1443        struct xfs_btree_cur    *cur,
1444        xfs_agblock_t           agbno,
1445        xfs_extlen_t            aglen,
1446        enum xfs_refc_adjust_op adj)
1447{
1448        struct xfs_refcount_irec        ext, tmp;
1449        int                             error;
1450        int                             found_rec, found_tmp;
1451
1452        if (aglen == 0)
1453                return 0;
1454
1455        /* Find any overlapping refcount records */
1456        error = xfs_refcount_lookup_ge(cur, agbno, &found_rec);
1457        if (error)
1458                goto out_error;
1459        error = xfs_refcount_get_rec(cur, &ext, &found_rec);
1460        if (error)
1461                goto out_error;
1462        if (!found_rec) {
1463                ext.rc_startblock = cur->bc_mp->m_sb.sb_agblocks +
1464                                XFS_REFC_COW_START;
1465                ext.rc_blockcount = 0;
1466                ext.rc_refcount = 0;
1467        }
1468
1469        switch (adj) {
1470        case XFS_REFCOUNT_ADJUST_COW_ALLOC:
1471                /* Adding a CoW reservation, there should be nothing here. */
1472                if (XFS_IS_CORRUPT(cur->bc_mp,
1473                                   agbno + aglen > ext.rc_startblock)) {
1474                        error = -EFSCORRUPTED;
1475                        goto out_error;
1476                }
1477
1478                tmp.rc_startblock = agbno;
1479                tmp.rc_blockcount = aglen;
1480                tmp.rc_refcount = 1;
1481                trace_xfs_refcount_modify_extent(cur->bc_mp,
1482                                cur->bc_ag.pag->pag_agno, &tmp);
1483
1484                error = xfs_refcount_insert(cur, &tmp,
1485                                &found_tmp);
1486                if (error)
1487                        goto out_error;
1488                if (XFS_IS_CORRUPT(cur->bc_mp, found_tmp != 1)) {
1489                        error = -EFSCORRUPTED;
1490                        goto out_error;
1491                }
1492                break;
1493        case XFS_REFCOUNT_ADJUST_COW_FREE:
1494                /* Removing a CoW reservation, there should be one extent. */
1495                if (XFS_IS_CORRUPT(cur->bc_mp, ext.rc_startblock != agbno)) {
1496                        error = -EFSCORRUPTED;
1497                        goto out_error;
1498                }
1499                if (XFS_IS_CORRUPT(cur->bc_mp, ext.rc_blockcount != aglen)) {
1500                        error = -EFSCORRUPTED;
1501                        goto out_error;
1502                }
1503                if (XFS_IS_CORRUPT(cur->bc_mp, ext.rc_refcount != 1)) {
1504                        error = -EFSCORRUPTED;
1505                        goto out_error;
1506                }
1507
1508                ext.rc_refcount = 0;
1509                trace_xfs_refcount_modify_extent(cur->bc_mp,
1510                                cur->bc_ag.pag->pag_agno, &ext);
1511                error = xfs_refcount_delete(cur, &found_rec);
1512                if (error)
1513                        goto out_error;
1514                if (XFS_IS_CORRUPT(cur->bc_mp, found_rec != 1)) {
1515                        error = -EFSCORRUPTED;
1516                        goto out_error;
1517                }
1518                break;
1519        default:
1520                ASSERT(0);
1521        }
1522
1523        return error;
1524out_error:
1525        trace_xfs_refcount_modify_extent_error(cur->bc_mp,
1526                        cur->bc_ag.pag->pag_agno, error, _RET_IP_);
1527        return error;
1528}
1529
1530/*
1531 * Add or remove refcount btree entries for CoW reservations.
1532 */
1533STATIC int
1534xfs_refcount_adjust_cow(
1535        struct xfs_btree_cur    *cur,
1536        xfs_agblock_t           agbno,
1537        xfs_extlen_t            aglen,
1538        enum xfs_refc_adjust_op adj)
1539{
1540        bool                    shape_changed;
1541        int                     error;
1542
1543        agbno += XFS_REFC_COW_START;
1544
1545        /*
1546         * Ensure that no rcextents cross the boundary of the adjustment range.
1547         */
1548        error = xfs_refcount_split_extent(cur, agbno, &shape_changed);
1549        if (error)
1550                goto out_error;
1551
1552        error = xfs_refcount_split_extent(cur, agbno + aglen, &shape_changed);
1553        if (error)
1554                goto out_error;
1555
1556        /*
1557         * Try to merge with the left or right extents of the range.
1558         */
1559        error = xfs_refcount_merge_extents(cur, &agbno, &aglen, adj,
1560                        XFS_FIND_RCEXT_COW, &shape_changed);
1561        if (error)
1562                goto out_error;
1563
1564        /* Now that we've taken care of the ends, adjust the middle extents */
1565        error = xfs_refcount_adjust_cow_extents(cur, agbno, aglen, adj);
1566        if (error)
1567                goto out_error;
1568
1569        return 0;
1570
1571out_error:
1572        trace_xfs_refcount_adjust_cow_error(cur->bc_mp, cur->bc_ag.pag->pag_agno,
1573                        error, _RET_IP_);
1574        return error;
1575}
1576
1577/*
1578 * Record a CoW allocation in the refcount btree.
1579 */
1580STATIC int
1581__xfs_refcount_cow_alloc(
1582        struct xfs_btree_cur    *rcur,
1583        xfs_agblock_t           agbno,
1584        xfs_extlen_t            aglen)
1585{
1586        trace_xfs_refcount_cow_increase(rcur->bc_mp, rcur->bc_ag.pag->pag_agno,
1587                        agbno, aglen);
1588
1589        /* Add refcount btree reservation */
1590        return xfs_refcount_adjust_cow(rcur, agbno, aglen,
1591                        XFS_REFCOUNT_ADJUST_COW_ALLOC);
1592}
1593
1594/*
1595 * Remove a CoW allocation from the refcount btree.
1596 */
1597STATIC int
1598__xfs_refcount_cow_free(
1599        struct xfs_btree_cur    *rcur,
1600        xfs_agblock_t           agbno,
1601        xfs_extlen_t            aglen)
1602{
1603        trace_xfs_refcount_cow_decrease(rcur->bc_mp, rcur->bc_ag.pag->pag_agno,
1604                        agbno, aglen);
1605
1606        /* Remove refcount btree reservation */
1607        return xfs_refcount_adjust_cow(rcur, agbno, aglen,
1608                        XFS_REFCOUNT_ADJUST_COW_FREE);
1609}
1610
1611/* Record a CoW staging extent in the refcount btree. */
1612void
1613xfs_refcount_alloc_cow_extent(
1614        struct xfs_trans                *tp,
1615        xfs_fsblock_t                   fsb,
1616        xfs_extlen_t                    len)
1617{
1618        struct xfs_mount                *mp = tp->t_mountp;
1619
1620        if (!xfs_sb_version_hasreflink(&mp->m_sb))
1621                return;
1622
1623        __xfs_refcount_add(tp, XFS_REFCOUNT_ALLOC_COW, fsb, len);
1624
1625        /* Add rmap entry */
1626        xfs_rmap_alloc_extent(tp, XFS_FSB_TO_AGNO(mp, fsb),
1627                        XFS_FSB_TO_AGBNO(mp, fsb), len, XFS_RMAP_OWN_COW);
1628}
1629
1630/* Forget a CoW staging event in the refcount btree. */
1631void
1632xfs_refcount_free_cow_extent(
1633        struct xfs_trans                *tp,
1634        xfs_fsblock_t                   fsb,
1635        xfs_extlen_t                    len)
1636{
1637        struct xfs_mount                *mp = tp->t_mountp;
1638
1639        if (!xfs_sb_version_hasreflink(&mp->m_sb))
1640                return;
1641
1642        /* Remove rmap entry */
1643        xfs_rmap_free_extent(tp, XFS_FSB_TO_AGNO(mp, fsb),
1644                        XFS_FSB_TO_AGBNO(mp, fsb), len, XFS_RMAP_OWN_COW);
1645        __xfs_refcount_add(tp, XFS_REFCOUNT_FREE_COW, fsb, len);
1646}
1647
1648struct xfs_refcount_recovery {
1649        struct list_head                rr_list;
1650        struct xfs_refcount_irec        rr_rrec;
1651};
1652
1653/* Stuff an extent on the recovery list. */
1654STATIC int
1655xfs_refcount_recover_extent(
1656        struct xfs_btree_cur            *cur,
1657        union xfs_btree_rec             *rec,
1658        void                            *priv)
1659{
1660        struct list_head                *debris = priv;
1661        struct xfs_refcount_recovery    *rr;
1662
1663        if (XFS_IS_CORRUPT(cur->bc_mp,
1664                           be32_to_cpu(rec->refc.rc_refcount) != 1))
1665                return -EFSCORRUPTED;
1666
1667        rr = kmem_alloc(sizeof(struct xfs_refcount_recovery), 0);
1668        xfs_refcount_btrec_to_irec(rec, &rr->rr_rrec);
1669        list_add_tail(&rr->rr_list, debris);
1670
1671        return 0;
1672}
1673
1674/* Find and remove leftover CoW reservations. */
1675int
1676xfs_refcount_recover_cow_leftovers(
1677        struct xfs_mount                *mp,
1678        struct xfs_perag                *pag)
1679{
1680        struct xfs_trans                *tp;
1681        struct xfs_btree_cur            *cur;
1682        struct xfs_buf                  *agbp;
1683        struct xfs_refcount_recovery    *rr, *n;
1684        struct list_head                debris;
1685        union xfs_btree_irec            low;
1686        union xfs_btree_irec            high;
1687        xfs_fsblock_t                   fsb;
1688        xfs_agblock_t                   agbno;
1689        int                             error;
1690
1691        if (mp->m_sb.sb_agblocks >= XFS_REFC_COW_START)
1692                return -EOPNOTSUPP;
1693
1694        INIT_LIST_HEAD(&debris);
1695
1696        /*
1697         * In this first part, we use an empty transaction to gather up
1698         * all the leftover CoW extents so that we can subsequently
1699         * delete them.  The empty transaction is used to avoid
1700         * a buffer lock deadlock if there happens to be a loop in the
1701         * refcountbt because we're allowed to re-grab a buffer that is
1702         * already attached to our transaction.  When we're done
1703         * recording the CoW debris we cancel the (empty) transaction
1704         * and everything goes away cleanly.
1705         */
1706        error = xfs_trans_alloc_empty(mp, &tp);
1707        if (error)
1708                return error;
1709
1710        error = xfs_alloc_read_agf(mp, tp, pag->pag_agno, 0, &agbp);
1711        if (error)
1712                goto out_trans;
1713        cur = xfs_refcountbt_init_cursor(mp, tp, agbp, pag);
1714
1715        /* Find all the leftover CoW staging extents. */
1716        memset(&low, 0, sizeof(low));
1717        memset(&high, 0, sizeof(high));
1718        low.rc.rc_startblock = XFS_REFC_COW_START;
1719        high.rc.rc_startblock = -1U;
1720        error = xfs_btree_query_range(cur, &low, &high,
1721                        xfs_refcount_recover_extent, &debris);
1722        xfs_btree_del_cursor(cur, error);
1723        xfs_trans_brelse(tp, agbp);
1724        xfs_trans_cancel(tp);
1725        if (error)
1726                goto out_free;
1727
1728        /* Now iterate the list to free the leftovers */
1729        list_for_each_entry_safe(rr, n, &debris, rr_list) {
1730                /* Set up transaction. */
1731                error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1732                if (error)
1733                        goto out_free;
1734
1735                trace_xfs_refcount_recover_extent(mp, pag->pag_agno,
1736                                &rr->rr_rrec);
1737
1738                /* Free the orphan record */
1739                agbno = rr->rr_rrec.rc_startblock - XFS_REFC_COW_START;
1740                fsb = XFS_AGB_TO_FSB(mp, pag->pag_agno, agbno);
1741                xfs_refcount_free_cow_extent(tp, fsb,
1742                                rr->rr_rrec.rc_blockcount);
1743
1744                /* Free the block. */
1745                xfs_bmap_add_free(tp, fsb, rr->rr_rrec.rc_blockcount, NULL);
1746
1747                error = xfs_trans_commit(tp);
1748                if (error)
1749                        goto out_free;
1750
1751                list_del(&rr->rr_list);
1752                kmem_free(rr);
1753        }
1754
1755        return error;
1756out_trans:
1757        xfs_trans_cancel(tp);
1758out_free:
1759        /* Free the leftover list */
1760        list_for_each_entry_safe(rr, n, &debris, rr_list) {
1761                list_del(&rr->rr_list);
1762                kmem_free(rr);
1763        }
1764        return error;
1765}
1766
1767/* Is there a record covering a given extent? */
1768int
1769xfs_refcount_has_record(
1770        struct xfs_btree_cur    *cur,
1771        xfs_agblock_t           bno,
1772        xfs_extlen_t            len,
1773        bool                    *exists)
1774{
1775        union xfs_btree_irec    low;
1776        union xfs_btree_irec    high;
1777
1778        memset(&low, 0, sizeof(low));
1779        low.rc.rc_startblock = bno;
1780        memset(&high, 0xFF, sizeof(high));
1781        high.rc.rc_startblock = bno + len - 1;
1782
1783        return xfs_btree_has_record(cur, &low, &high, exists);
1784}
1785