linux/fs/ntfs/runlist.c
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   1/**
   2 * runlist.c - NTFS runlist handling code.  Part of the Linux-NTFS project.
   3 *
   4 * Copyright (c) 2001-2007 Anton Altaparmakov
   5 * Copyright (c) 2002-2005 Richard Russon
   6 *
   7 * This program/include file is free software; you can redistribute it and/or
   8 * modify it under the terms of the GNU General Public License as published
   9 * by the Free Software Foundation; either version 2 of the License, or
  10 * (at your option) any later version.
  11 *
  12 * This program/include file is distributed in the hope that it will be
  13 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  14 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 * GNU General Public License for more details.
  16 *
  17 * You should have received a copy of the GNU General Public License
  18 * along with this program (in the main directory of the Linux-NTFS
  19 * distribution in the file COPYING); if not, write to the Free Software
  20 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21 */
  22
  23#include "debug.h"
  24#include "dir.h"
  25#include "endian.h"
  26#include "malloc.h"
  27#include "ntfs.h"
  28
  29/**
  30 * ntfs_rl_mm - runlist memmove
  31 *
  32 * It is up to the caller to serialize access to the runlist @base.
  33 */
  34static inline void ntfs_rl_mm(runlist_element *base, int dst, int src,
  35                int size)
  36{
  37        if (likely((dst != src) && (size > 0)))
  38                memmove(base + dst, base + src, size * sizeof(*base));
  39}
  40
  41/**
  42 * ntfs_rl_mc - runlist memory copy
  43 *
  44 * It is up to the caller to serialize access to the runlists @dstbase and
  45 * @srcbase.
  46 */
  47static inline void ntfs_rl_mc(runlist_element *dstbase, int dst,
  48                runlist_element *srcbase, int src, int size)
  49{
  50        if (likely(size > 0))
  51                memcpy(dstbase + dst, srcbase + src, size * sizeof(*dstbase));
  52}
  53
  54/**
  55 * ntfs_rl_realloc - Reallocate memory for runlists
  56 * @rl:         original runlist
  57 * @old_size:   number of runlist elements in the original runlist @rl
  58 * @new_size:   number of runlist elements we need space for
  59 *
  60 * As the runlists grow, more memory will be required.  To prevent the
  61 * kernel having to allocate and reallocate large numbers of small bits of
  62 * memory, this function returns an entire page of memory.
  63 *
  64 * It is up to the caller to serialize access to the runlist @rl.
  65 *
  66 * N.B.  If the new allocation doesn't require a different number of pages in
  67 *       memory, the function will return the original pointer.
  68 *
  69 * On success, return a pointer to the newly allocated, or recycled, memory.
  70 * On error, return -errno. The following error codes are defined:
  71 *      -ENOMEM - Not enough memory to allocate runlist array.
  72 *      -EINVAL - Invalid parameters were passed in.
  73 */
  74static inline runlist_element *ntfs_rl_realloc(runlist_element *rl,
  75                int old_size, int new_size)
  76{
  77        runlist_element *new_rl;
  78
  79        old_size = PAGE_ALIGN(old_size * sizeof(*rl));
  80        new_size = PAGE_ALIGN(new_size * sizeof(*rl));
  81        if (old_size == new_size)
  82                return rl;
  83
  84        new_rl = ntfs_malloc_nofs(new_size);
  85        if (unlikely(!new_rl))
  86                return ERR_PTR(-ENOMEM);
  87
  88        if (likely(rl != NULL)) {
  89                if (unlikely(old_size > new_size))
  90                        old_size = new_size;
  91                memcpy(new_rl, rl, old_size);
  92                ntfs_free(rl);
  93        }
  94        return new_rl;
  95}
  96
  97/**
  98 * ntfs_rl_realloc_nofail - Reallocate memory for runlists
  99 * @rl:         original runlist
 100 * @old_size:   number of runlist elements in the original runlist @rl
 101 * @new_size:   number of runlist elements we need space for
 102 *
 103 * As the runlists grow, more memory will be required.  To prevent the
 104 * kernel having to allocate and reallocate large numbers of small bits of
 105 * memory, this function returns an entire page of memory.
 106 *
 107 * This function guarantees that the allocation will succeed.  It will sleep
 108 * for as long as it takes to complete the allocation.
 109 *
 110 * It is up to the caller to serialize access to the runlist @rl.
 111 *
 112 * N.B.  If the new allocation doesn't require a different number of pages in
 113 *       memory, the function will return the original pointer.
 114 *
 115 * On success, return a pointer to the newly allocated, or recycled, memory.
 116 * On error, return -errno. The following error codes are defined:
 117 *      -ENOMEM - Not enough memory to allocate runlist array.
 118 *      -EINVAL - Invalid parameters were passed in.
 119 */
 120static inline runlist_element *ntfs_rl_realloc_nofail(runlist_element *rl,
 121                int old_size, int new_size)
 122{
 123        runlist_element *new_rl;
 124
 125        old_size = PAGE_ALIGN(old_size * sizeof(*rl));
 126        new_size = PAGE_ALIGN(new_size * sizeof(*rl));
 127        if (old_size == new_size)
 128                return rl;
 129
 130        new_rl = ntfs_malloc_nofs_nofail(new_size);
 131        BUG_ON(!new_rl);
 132
 133        if (likely(rl != NULL)) {
 134                if (unlikely(old_size > new_size))
 135                        old_size = new_size;
 136                memcpy(new_rl, rl, old_size);
 137                ntfs_free(rl);
 138        }
 139        return new_rl;
 140}
 141
 142/**
 143 * ntfs_are_rl_mergeable - test if two runlists can be joined together
 144 * @dst:        original runlist
 145 * @src:        new runlist to test for mergeability with @dst
 146 *
 147 * Test if two runlists can be joined together. For this, their VCNs and LCNs
 148 * must be adjacent.
 149 *
 150 * It is up to the caller to serialize access to the runlists @dst and @src.
 151 *
 152 * Return: true   Success, the runlists can be merged.
 153 *         false  Failure, the runlists cannot be merged.
 154 */
 155static inline bool ntfs_are_rl_mergeable(runlist_element *dst,
 156                runlist_element *src)
 157{
 158        BUG_ON(!dst);
 159        BUG_ON(!src);
 160
 161        /* We can merge unmapped regions even if they are misaligned. */
 162        if ((dst->lcn == LCN_RL_NOT_MAPPED) && (src->lcn == LCN_RL_NOT_MAPPED))
 163                return true;
 164        /* If the runs are misaligned, we cannot merge them. */
 165        if ((dst->vcn + dst->length) != src->vcn)
 166                return false;
 167        /* If both runs are non-sparse and contiguous, we can merge them. */
 168        if ((dst->lcn >= 0) && (src->lcn >= 0) &&
 169                        ((dst->lcn + dst->length) == src->lcn))
 170                return true;
 171        /* If we are merging two holes, we can merge them. */
 172        if ((dst->lcn == LCN_HOLE) && (src->lcn == LCN_HOLE))
 173                return true;
 174        /* Cannot merge. */
 175        return false;
 176}
 177
 178/**
 179 * __ntfs_rl_merge - merge two runlists without testing if they can be merged
 180 * @dst:        original, destination runlist
 181 * @src:        new runlist to merge with @dst
 182 *
 183 * Merge the two runlists, writing into the destination runlist @dst. The
 184 * caller must make sure the runlists can be merged or this will corrupt the
 185 * destination runlist.
 186 *
 187 * It is up to the caller to serialize access to the runlists @dst and @src.
 188 */
 189static inline void __ntfs_rl_merge(runlist_element *dst, runlist_element *src)
 190{
 191        dst->length += src->length;
 192}
 193
 194/**
 195 * ntfs_rl_append - append a runlist after a given element
 196 * @dst:        original runlist to be worked on
 197 * @dsize:      number of elements in @dst (including end marker)
 198 * @src:        runlist to be inserted into @dst
 199 * @ssize:      number of elements in @src (excluding end marker)
 200 * @loc:        append the new runlist @src after this element in @dst
 201 *
 202 * Append the runlist @src after element @loc in @dst.  Merge the right end of
 203 * the new runlist, if necessary. Adjust the size of the hole before the
 204 * appended runlist.
 205 *
 206 * It is up to the caller to serialize access to the runlists @dst and @src.
 207 *
 208 * On success, return a pointer to the new, combined, runlist. Note, both
 209 * runlists @dst and @src are deallocated before returning so you cannot use
 210 * the pointers for anything any more. (Strictly speaking the returned runlist
 211 * may be the same as @dst but this is irrelevant.)
 212 *
 213 * On error, return -errno. Both runlists are left unmodified. The following
 214 * error codes are defined:
 215 *      -ENOMEM - Not enough memory to allocate runlist array.
 216 *      -EINVAL - Invalid parameters were passed in.
 217 */
 218static inline runlist_element *ntfs_rl_append(runlist_element *dst,
 219                int dsize, runlist_element *src, int ssize, int loc)
 220{
 221        bool right = false;     /* Right end of @src needs merging. */
 222        int marker;             /* End of the inserted runs. */
 223
 224        BUG_ON(!dst);
 225        BUG_ON(!src);
 226
 227        /* First, check if the right hand end needs merging. */
 228        if ((loc + 1) < dsize)
 229                right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
 230
 231        /* Space required: @dst size + @src size, less one if we merged. */
 232        dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - right);
 233        if (IS_ERR(dst))
 234                return dst;
 235        /*
 236         * We are guaranteed to succeed from here so can start modifying the
 237         * original runlists.
 238         */
 239
 240        /* First, merge the right hand end, if necessary. */
 241        if (right)
 242                __ntfs_rl_merge(src + ssize - 1, dst + loc + 1);
 243
 244        /* First run after the @src runs that have been inserted. */
 245        marker = loc + ssize + 1;
 246
 247        /* Move the tail of @dst out of the way, then copy in @src. */
 248        ntfs_rl_mm(dst, marker, loc + 1 + right, dsize - (loc + 1 + right));
 249        ntfs_rl_mc(dst, loc + 1, src, 0, ssize);
 250
 251        /* Adjust the size of the preceding hole. */
 252        dst[loc].length = dst[loc + 1].vcn - dst[loc].vcn;
 253
 254        /* We may have changed the length of the file, so fix the end marker */
 255        if (dst[marker].lcn == LCN_ENOENT)
 256                dst[marker].vcn = dst[marker - 1].vcn + dst[marker - 1].length;
 257
 258        return dst;
 259}
 260
 261/**
 262 * ntfs_rl_insert - insert a runlist into another
 263 * @dst:        original runlist to be worked on
 264 * @dsize:      number of elements in @dst (including end marker)
 265 * @src:        new runlist to be inserted
 266 * @ssize:      number of elements in @src (excluding end marker)
 267 * @loc:        insert the new runlist @src before this element in @dst
 268 *
 269 * Insert the runlist @src before element @loc in the runlist @dst. Merge the
 270 * left end of the new runlist, if necessary. Adjust the size of the hole
 271 * after the inserted runlist.
 272 *
 273 * It is up to the caller to serialize access to the runlists @dst and @src.
 274 *
 275 * On success, return a pointer to the new, combined, runlist. Note, both
 276 * runlists @dst and @src are deallocated before returning so you cannot use
 277 * the pointers for anything any more. (Strictly speaking the returned runlist
 278 * may be the same as @dst but this is irrelevant.)
 279 *
 280 * On error, return -errno. Both runlists are left unmodified. The following
 281 * error codes are defined:
 282 *      -ENOMEM - Not enough memory to allocate runlist array.
 283 *      -EINVAL - Invalid parameters were passed in.
 284 */
 285static inline runlist_element *ntfs_rl_insert(runlist_element *dst,
 286                int dsize, runlist_element *src, int ssize, int loc)
 287{
 288        bool left = false;      /* Left end of @src needs merging. */
 289        bool disc = false;      /* Discontinuity between @dst and @src. */
 290        int marker;             /* End of the inserted runs. */
 291
 292        BUG_ON(!dst);
 293        BUG_ON(!src);
 294
 295        /*
 296         * disc => Discontinuity between the end of @dst and the start of @src.
 297         *         This means we might need to insert a "not mapped" run.
 298         */
 299        if (loc == 0)
 300                disc = (src[0].vcn > 0);
 301        else {
 302                s64 merged_length;
 303
 304                left = ntfs_are_rl_mergeable(dst + loc - 1, src);
 305
 306                merged_length = dst[loc - 1].length;
 307                if (left)
 308                        merged_length += src->length;
 309
 310                disc = (src[0].vcn > dst[loc - 1].vcn + merged_length);
 311        }
 312        /*
 313         * Space required: @dst size + @src size, less one if we merged, plus
 314         * one if there was a discontinuity.
 315         */
 316        dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - left + disc);
 317        if (IS_ERR(dst))
 318                return dst;
 319        /*
 320         * We are guaranteed to succeed from here so can start modifying the
 321         * original runlist.
 322         */
 323        if (left)
 324                __ntfs_rl_merge(dst + loc - 1, src);
 325        /*
 326         * First run after the @src runs that have been inserted.
 327         * Nominally,  @marker equals @loc + @ssize, i.e. location + number of
 328         * runs in @src.  However, if @left, then the first run in @src has
 329         * been merged with one in @dst.  And if @disc, then @dst and @src do
 330         * not meet and we need an extra run to fill the gap.
 331         */
 332        marker = loc + ssize - left + disc;
 333
 334        /* Move the tail of @dst out of the way, then copy in @src. */
 335        ntfs_rl_mm(dst, marker, loc, dsize - loc);
 336        ntfs_rl_mc(dst, loc + disc, src, left, ssize - left);
 337
 338        /* Adjust the VCN of the first run after the insertion... */
 339        dst[marker].vcn = dst[marker - 1].vcn + dst[marker - 1].length;
 340        /* ... and the length. */
 341        if (dst[marker].lcn == LCN_HOLE || dst[marker].lcn == LCN_RL_NOT_MAPPED)
 342                dst[marker].length = dst[marker + 1].vcn - dst[marker].vcn;
 343
 344        /* Writing beyond the end of the file and there is a discontinuity. */
 345        if (disc) {
 346                if (loc > 0) {
 347                        dst[loc].vcn = dst[loc - 1].vcn + dst[loc - 1].length;
 348                        dst[loc].length = dst[loc + 1].vcn - dst[loc].vcn;
 349                } else {
 350                        dst[loc].vcn = 0;
 351                        dst[loc].length = dst[loc + 1].vcn;
 352                }
 353                dst[loc].lcn = LCN_RL_NOT_MAPPED;
 354        }
 355        return dst;
 356}
 357
 358/**
 359 * ntfs_rl_replace - overwrite a runlist element with another runlist
 360 * @dst:        original runlist to be worked on
 361 * @dsize:      number of elements in @dst (including end marker)
 362 * @src:        new runlist to be inserted
 363 * @ssize:      number of elements in @src (excluding end marker)
 364 * @loc:        index in runlist @dst to overwrite with @src
 365 *
 366 * Replace the runlist element @dst at @loc with @src. Merge the left and
 367 * right ends of the inserted runlist, if necessary.
 368 *
 369 * It is up to the caller to serialize access to the runlists @dst and @src.
 370 *
 371 * On success, return a pointer to the new, combined, runlist. Note, both
 372 * runlists @dst and @src are deallocated before returning so you cannot use
 373 * the pointers for anything any more. (Strictly speaking the returned runlist
 374 * may be the same as @dst but this is irrelevant.)
 375 *
 376 * On error, return -errno. Both runlists are left unmodified. The following
 377 * error codes are defined:
 378 *      -ENOMEM - Not enough memory to allocate runlist array.
 379 *      -EINVAL - Invalid parameters were passed in.
 380 */
 381static inline runlist_element *ntfs_rl_replace(runlist_element *dst,
 382                int dsize, runlist_element *src, int ssize, int loc)
 383{
 384        signed delta;
 385        bool left = false;      /* Left end of @src needs merging. */
 386        bool right = false;     /* Right end of @src needs merging. */
 387        int tail;               /* Start of tail of @dst. */
 388        int marker;             /* End of the inserted runs. */
 389
 390        BUG_ON(!dst);
 391        BUG_ON(!src);
 392
 393        /* First, see if the left and right ends need merging. */
 394        if ((loc + 1) < dsize)
 395                right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
 396        if (loc > 0)
 397                left = ntfs_are_rl_mergeable(dst + loc - 1, src);
 398        /*
 399         * Allocate some space.  We will need less if the left, right, or both
 400         * ends get merged.  The -1 accounts for the run being replaced.
 401         */
 402        delta = ssize - 1 - left - right;
 403        if (delta > 0) {
 404                dst = ntfs_rl_realloc(dst, dsize, dsize + delta);
 405                if (IS_ERR(dst))
 406                        return dst;
 407        }
 408        /*
 409         * We are guaranteed to succeed from here so can start modifying the
 410         * original runlists.
 411         */
 412
 413        /* First, merge the left and right ends, if necessary. */
 414        if (right)
 415                __ntfs_rl_merge(src + ssize - 1, dst + loc + 1);
 416        if (left)
 417                __ntfs_rl_merge(dst + loc - 1, src);
 418        /*
 419         * Offset of the tail of @dst.  This needs to be moved out of the way
 420         * to make space for the runs to be copied from @src, i.e. the first
 421         * run of the tail of @dst.
 422         * Nominally, @tail equals @loc + 1, i.e. location, skipping the
 423         * replaced run.  However, if @right, then one of @dst's runs is
 424         * already merged into @src.
 425         */
 426        tail = loc + right + 1;
 427        /*
 428         * First run after the @src runs that have been inserted, i.e. where
 429         * the tail of @dst needs to be moved to.
 430         * Nominally, @marker equals @loc + @ssize, i.e. location + number of
 431         * runs in @src.  However, if @left, then the first run in @src has
 432         * been merged with one in @dst.
 433         */
 434        marker = loc + ssize - left;
 435
 436        /* Move the tail of @dst out of the way, then copy in @src. */
 437        ntfs_rl_mm(dst, marker, tail, dsize - tail);
 438        ntfs_rl_mc(dst, loc, src, left, ssize - left);
 439
 440        /* We may have changed the length of the file, so fix the end marker. */
 441        if (dsize - tail > 0 && dst[marker].lcn == LCN_ENOENT)
 442                dst[marker].vcn = dst[marker - 1].vcn + dst[marker - 1].length;
 443        return dst;
 444}
 445
 446/**
 447 * ntfs_rl_split - insert a runlist into the centre of a hole
 448 * @dst:        original runlist to be worked on
 449 * @dsize:      number of elements in @dst (including end marker)
 450 * @src:        new runlist to be inserted
 451 * @ssize:      number of elements in @src (excluding end marker)
 452 * @loc:        index in runlist @dst at which to split and insert @src
 453 *
 454 * Split the runlist @dst at @loc into two and insert @new in between the two
 455 * fragments. No merging of runlists is necessary. Adjust the size of the
 456 * holes either side.
 457 *
 458 * It is up to the caller to serialize access to the runlists @dst and @src.
 459 *
 460 * On success, return a pointer to the new, combined, runlist. Note, both
 461 * runlists @dst and @src are deallocated before returning so you cannot use
 462 * the pointers for anything any more. (Strictly speaking the returned runlist
 463 * may be the same as @dst but this is irrelevant.)
 464 *
 465 * On error, return -errno. Both runlists are left unmodified. The following
 466 * error codes are defined:
 467 *      -ENOMEM - Not enough memory to allocate runlist array.
 468 *      -EINVAL - Invalid parameters were passed in.
 469 */
 470static inline runlist_element *ntfs_rl_split(runlist_element *dst, int dsize,
 471                runlist_element *src, int ssize, int loc)
 472{
 473        BUG_ON(!dst);
 474        BUG_ON(!src);
 475
 476        /* Space required: @dst size + @src size + one new hole. */
 477        dst = ntfs_rl_realloc(dst, dsize, dsize + ssize + 1);
 478        if (IS_ERR(dst))
 479                return dst;
 480        /*
 481         * We are guaranteed to succeed from here so can start modifying the
 482         * original runlists.
 483         */
 484
 485        /* Move the tail of @dst out of the way, then copy in @src. */
 486        ntfs_rl_mm(dst, loc + 1 + ssize, loc, dsize - loc);
 487        ntfs_rl_mc(dst, loc + 1, src, 0, ssize);
 488
 489        /* Adjust the size of the holes either size of @src. */
 490        dst[loc].length         = dst[loc+1].vcn       - dst[loc].vcn;
 491        dst[loc+ssize+1].vcn    = dst[loc+ssize].vcn   + dst[loc+ssize].length;
 492        dst[loc+ssize+1].length = dst[loc+ssize+2].vcn - dst[loc+ssize+1].vcn;
 493
 494        return dst;
 495}
 496
 497/**
 498 * ntfs_runlists_merge - merge two runlists into one
 499 * @drl:        original runlist to be worked on
 500 * @srl:        new runlist to be merged into @drl
 501 *
 502 * First we sanity check the two runlists @srl and @drl to make sure that they
 503 * are sensible and can be merged. The runlist @srl must be either after the
 504 * runlist @drl or completely within a hole (or unmapped region) in @drl.
 505 *
 506 * It is up to the caller to serialize access to the runlists @drl and @srl.
 507 *
 508 * Merging of runlists is necessary in two cases:
 509 *   1. When attribute lists are used and a further extent is being mapped.
 510 *   2. When new clusters are allocated to fill a hole or extend a file.
 511 *
 512 * There are four possible ways @srl can be merged. It can:
 513 *      - be inserted at the beginning of a hole,
 514 *      - split the hole in two and be inserted between the two fragments,
 515 *      - be appended at the end of a hole, or it can
 516 *      - replace the whole hole.
 517 * It can also be appended to the end of the runlist, which is just a variant
 518 * of the insert case.
 519 *
 520 * On success, return a pointer to the new, combined, runlist. Note, both
 521 * runlists @drl and @srl are deallocated before returning so you cannot use
 522 * the pointers for anything any more. (Strictly speaking the returned runlist
 523 * may be the same as @dst but this is irrelevant.)
 524 *
 525 * On error, return -errno. Both runlists are left unmodified. The following
 526 * error codes are defined:
 527 *      -ENOMEM - Not enough memory to allocate runlist array.
 528 *      -EINVAL - Invalid parameters were passed in.
 529 *      -ERANGE - The runlists overlap and cannot be merged.
 530 */
 531runlist_element *ntfs_runlists_merge(runlist_element *drl,
 532                runlist_element *srl)
 533{
 534        int di, si;             /* Current index into @[ds]rl. */
 535        int sstart;             /* First index with lcn > LCN_RL_NOT_MAPPED. */
 536        int dins;               /* Index into @drl at which to insert @srl. */
 537        int dend, send;         /* Last index into @[ds]rl. */
 538        int dfinal, sfinal;     /* The last index into @[ds]rl with
 539                                   lcn >= LCN_HOLE. */
 540        int marker = 0;
 541        VCN marker_vcn = 0;
 542
 543#ifdef DEBUG
 544        ntfs_debug("dst:");
 545        ntfs_debug_dump_runlist(drl);
 546        ntfs_debug("src:");
 547        ntfs_debug_dump_runlist(srl);
 548#endif
 549
 550        /* Check for silly calling... */
 551        if (unlikely(!srl))
 552                return drl;
 553        if (IS_ERR(srl) || IS_ERR(drl))
 554                return ERR_PTR(-EINVAL);
 555
 556        /* Check for the case where the first mapping is being done now. */
 557        if (unlikely(!drl)) {
 558                drl = srl;
 559                /* Complete the source runlist if necessary. */
 560                if (unlikely(drl[0].vcn)) {
 561                        /* Scan to the end of the source runlist. */
 562                        for (dend = 0; likely(drl[dend].length); dend++)
 563                                ;
 564                        dend++;
 565                        drl = ntfs_rl_realloc(drl, dend, dend + 1);
 566                        if (IS_ERR(drl))
 567                                return drl;
 568                        /* Insert start element at the front of the runlist. */
 569                        ntfs_rl_mm(drl, 1, 0, dend);
 570                        drl[0].vcn = 0;
 571                        drl[0].lcn = LCN_RL_NOT_MAPPED;
 572                        drl[0].length = drl[1].vcn;
 573                }
 574                goto finished;
 575        }
 576
 577        si = di = 0;
 578
 579        /* Skip any unmapped start element(s) in the source runlist. */
 580        while (srl[si].length && srl[si].lcn < LCN_HOLE)
 581                si++;
 582
 583        /* Can't have an entirely unmapped source runlist. */
 584        BUG_ON(!srl[si].length);
 585
 586        /* Record the starting points. */
 587        sstart = si;
 588
 589        /*
 590         * Skip forward in @drl until we reach the position where @srl needs to
 591         * be inserted. If we reach the end of @drl, @srl just needs to be
 592         * appended to @drl.
 593         */
 594        for (; drl[di].length; di++) {
 595                if (drl[di].vcn + drl[di].length > srl[sstart].vcn)
 596                        break;
 597        }
 598        dins = di;
 599
 600        /* Sanity check for illegal overlaps. */
 601        if ((drl[di].vcn == srl[si].vcn) && (drl[di].lcn >= 0) &&
 602                        (srl[si].lcn >= 0)) {
 603                ntfs_error(NULL, "Run lists overlap. Cannot merge!");
 604                return ERR_PTR(-ERANGE);
 605        }
 606
 607        /* Scan to the end of both runlists in order to know their sizes. */
 608        for (send = si; srl[send].length; send++)
 609                ;
 610        for (dend = di; drl[dend].length; dend++)
 611                ;
 612
 613        if (srl[send].lcn == LCN_ENOENT)
 614                marker_vcn = srl[marker = send].vcn;
 615
 616        /* Scan to the last element with lcn >= LCN_HOLE. */
 617        for (sfinal = send; sfinal >= 0 && srl[sfinal].lcn < LCN_HOLE; sfinal--)
 618                ;
 619        for (dfinal = dend; dfinal >= 0 && drl[dfinal].lcn < LCN_HOLE; dfinal--)
 620                ;
 621
 622        {
 623        bool start;
 624        bool finish;
 625        int ds = dend + 1;              /* Number of elements in drl & srl */
 626        int ss = sfinal - sstart + 1;
 627
 628        start  = ((drl[dins].lcn <  LCN_RL_NOT_MAPPED) ||    /* End of file   */
 629                  (drl[dins].vcn == srl[sstart].vcn));       /* Start of hole */
 630        finish = ((drl[dins].lcn >= LCN_RL_NOT_MAPPED) &&    /* End of file   */
 631                 ((drl[dins].vcn + drl[dins].length) <=      /* End of hole   */
 632                  (srl[send - 1].vcn + srl[send - 1].length)));
 633
 634        /* Or we will lose an end marker. */
 635        if (finish && !drl[dins].length)
 636                ss++;
 637        if (marker && (drl[dins].vcn + drl[dins].length > srl[send - 1].vcn))
 638                finish = false;
 639#if 0
 640        ntfs_debug("dfinal = %i, dend = %i", dfinal, dend);
 641        ntfs_debug("sstart = %i, sfinal = %i, send = %i", sstart, sfinal, send);
 642        ntfs_debug("start = %i, finish = %i", start, finish);
 643        ntfs_debug("ds = %i, ss = %i, dins = %i", ds, ss, dins);
 644#endif
 645        if (start) {
 646                if (finish)
 647                        drl = ntfs_rl_replace(drl, ds, srl + sstart, ss, dins);
 648                else
 649                        drl = ntfs_rl_insert(drl, ds, srl + sstart, ss, dins);
 650        } else {
 651                if (finish)
 652                        drl = ntfs_rl_append(drl, ds, srl + sstart, ss, dins);
 653                else
 654                        drl = ntfs_rl_split(drl, ds, srl + sstart, ss, dins);
 655        }
 656        if (IS_ERR(drl)) {
 657                ntfs_error(NULL, "Merge failed.");
 658                return drl;
 659        }
 660        ntfs_free(srl);
 661        if (marker) {
 662                ntfs_debug("Triggering marker code.");
 663                for (ds = dend; drl[ds].length; ds++)
 664                        ;
 665                /* We only need to care if @srl ended after @drl. */
 666                if (drl[ds].vcn <= marker_vcn) {
 667                        int slots = 0;
 668
 669                        if (drl[ds].vcn == marker_vcn) {
 670                                ntfs_debug("Old marker = 0x%llx, replacing "
 671                                                "with LCN_ENOENT.",
 672                                                (unsigned long long)
 673                                                drl[ds].lcn);
 674                                drl[ds].lcn = LCN_ENOENT;
 675                                goto finished;
 676                        }
 677                        /*
 678                         * We need to create an unmapped runlist element in
 679                         * @drl or extend an existing one before adding the
 680                         * ENOENT terminator.
 681                         */
 682                        if (drl[ds].lcn == LCN_ENOENT) {
 683                                ds--;
 684                                slots = 1;
 685                        }
 686                        if (drl[ds].lcn != LCN_RL_NOT_MAPPED) {
 687                                /* Add an unmapped runlist element. */
 688                                if (!slots) {
 689                                        drl = ntfs_rl_realloc_nofail(drl, ds,
 690                                                        ds + 2);
 691                                        slots = 2;
 692                                }
 693                                ds++;
 694                                /* Need to set vcn if it isn't set already. */
 695                                if (slots != 1)
 696                                        drl[ds].vcn = drl[ds - 1].vcn +
 697                                                        drl[ds - 1].length;
 698                                drl[ds].lcn = LCN_RL_NOT_MAPPED;
 699                                /* We now used up a slot. */
 700                                slots--;
 701                        }
 702                        drl[ds].length = marker_vcn - drl[ds].vcn;
 703                        /* Finally add the ENOENT terminator. */
 704                        ds++;
 705                        if (!slots)
 706                                drl = ntfs_rl_realloc_nofail(drl, ds, ds + 1);
 707                        drl[ds].vcn = marker_vcn;
 708                        drl[ds].lcn = LCN_ENOENT;
 709                        drl[ds].length = (s64)0;
 710                }
 711        }
 712        }
 713
 714finished:
 715        /* The merge was completed successfully. */
 716        ntfs_debug("Merged runlist:");
 717        ntfs_debug_dump_runlist(drl);
 718        return drl;
 719}
 720
 721/**
 722 * ntfs_mapping_pairs_decompress - convert mapping pairs array to runlist
 723 * @vol:        ntfs volume on which the attribute resides
 724 * @attr:       attribute record whose mapping pairs array to decompress
 725 * @old_rl:     optional runlist in which to insert @attr's runlist
 726 *
 727 * It is up to the caller to serialize access to the runlist @old_rl.
 728 *
 729 * Decompress the attribute @attr's mapping pairs array into a runlist. On
 730 * success, return the decompressed runlist.
 731 *
 732 * If @old_rl is not NULL, decompressed runlist is inserted into the
 733 * appropriate place in @old_rl and the resultant, combined runlist is
 734 * returned. The original @old_rl is deallocated.
 735 *
 736 * On error, return -errno. @old_rl is left unmodified in that case.
 737 *
 738 * The following error codes are defined:
 739 *      -ENOMEM - Not enough memory to allocate runlist array.
 740 *      -EIO    - Corrupt runlist.
 741 *      -EINVAL - Invalid parameters were passed in.
 742 *      -ERANGE - The two runlists overlap.
 743 *
 744 * FIXME: For now we take the conceptionally simplest approach of creating the
 745 * new runlist disregarding the already existing one and then splicing the
 746 * two into one, if that is possible (we check for overlap and discard the new
 747 * runlist if overlap present before returning ERR_PTR(-ERANGE)).
 748 */
 749runlist_element *ntfs_mapping_pairs_decompress(const ntfs_volume *vol,
 750                const ATTR_RECORD *attr, runlist_element *old_rl)
 751{
 752        VCN vcn;                /* Current vcn. */
 753        LCN lcn;                /* Current lcn. */
 754        s64 deltaxcn;           /* Change in [vl]cn. */
 755        runlist_element *rl;    /* The output runlist. */
 756        u8 *buf;                /* Current position in mapping pairs array. */
 757        u8 *attr_end;           /* End of attribute. */
 758        int rlsize;             /* Size of runlist buffer. */
 759        u16 rlpos;              /* Current runlist position in units of
 760                                   runlist_elements. */
 761        u8 b;                   /* Current byte offset in buf. */
 762
 763#ifdef DEBUG
 764        /* Make sure attr exists and is non-resident. */
 765        if (!attr || !attr->non_resident || sle64_to_cpu(
 766                        attr->data.non_resident.lowest_vcn) < (VCN)0) {
 767                ntfs_error(vol->sb, "Invalid arguments.");
 768                return ERR_PTR(-EINVAL);
 769        }
 770#endif
 771        /* Start at vcn = lowest_vcn and lcn 0. */
 772        vcn = sle64_to_cpu(attr->data.non_resident.lowest_vcn);
 773        lcn = 0;
 774        /* Get start of the mapping pairs array. */
 775        buf = (u8*)attr + le16_to_cpu(
 776                        attr->data.non_resident.mapping_pairs_offset);
 777        attr_end = (u8*)attr + le32_to_cpu(attr->length);
 778        if (unlikely(buf < (u8*)attr || buf > attr_end)) {
 779                ntfs_error(vol->sb, "Corrupt attribute.");
 780                return ERR_PTR(-EIO);
 781        }
 782        /* If the mapping pairs array is valid but empty, nothing to do. */
 783        if (!vcn && !*buf)
 784                return old_rl;
 785        /* Current position in runlist array. */
 786        rlpos = 0;
 787        /* Allocate first page and set current runlist size to one page. */
 788        rl = ntfs_malloc_nofs(rlsize = PAGE_SIZE);
 789        if (unlikely(!rl))
 790                return ERR_PTR(-ENOMEM);
 791        /* Insert unmapped starting element if necessary. */
 792        if (vcn) {
 793                rl->vcn = 0;
 794                rl->lcn = LCN_RL_NOT_MAPPED;
 795                rl->length = vcn;
 796                rlpos++;
 797        }
 798        while (buf < attr_end && *buf) {
 799                /*
 800                 * Allocate more memory if needed, including space for the
 801                 * not-mapped and terminator elements. ntfs_malloc_nofs()
 802                 * operates on whole pages only.
 803                 */
 804                if (((rlpos + 3) * sizeof(*old_rl)) > rlsize) {
 805                        runlist_element *rl2;
 806
 807                        rl2 = ntfs_malloc_nofs(rlsize + (int)PAGE_SIZE);
 808                        if (unlikely(!rl2)) {
 809                                ntfs_free(rl);
 810                                return ERR_PTR(-ENOMEM);
 811                        }
 812                        memcpy(rl2, rl, rlsize);
 813                        ntfs_free(rl);
 814                        rl = rl2;
 815                        rlsize += PAGE_SIZE;
 816                }
 817                /* Enter the current vcn into the current runlist element. */
 818                rl[rlpos].vcn = vcn;
 819                /*
 820                 * Get the change in vcn, i.e. the run length in clusters.
 821                 * Doing it this way ensures that we signextend negative values.
 822                 * A negative run length doesn't make any sense, but hey, I
 823                 * didn't make up the NTFS specs and Windows NT4 treats the run
 824                 * length as a signed value so that's how it is...
 825                 */
 826                b = *buf & 0xf;
 827                if (b) {
 828                        if (unlikely(buf + b > attr_end))
 829                                goto io_error;
 830                        for (deltaxcn = (s8)buf[b--]; b; b--)
 831                                deltaxcn = (deltaxcn << 8) + buf[b];
 832                } else { /* The length entry is compulsory. */
 833                        ntfs_error(vol->sb, "Missing length entry in mapping "
 834                                        "pairs array.");
 835                        deltaxcn = (s64)-1;
 836                }
 837                /*
 838                 * Assume a negative length to indicate data corruption and
 839                 * hence clean-up and return NULL.
 840                 */
 841                if (unlikely(deltaxcn < 0)) {
 842                        ntfs_error(vol->sb, "Invalid length in mapping pairs "
 843                                        "array.");
 844                        goto err_out;
 845                }
 846                /*
 847                 * Enter the current run length into the current runlist
 848                 * element.
 849                 */
 850                rl[rlpos].length = deltaxcn;
 851                /* Increment the current vcn by the current run length. */
 852                vcn += deltaxcn;
 853                /*
 854                 * There might be no lcn change at all, as is the case for
 855                 * sparse clusters on NTFS 3.0+, in which case we set the lcn
 856                 * to LCN_HOLE.
 857                 */
 858                if (!(*buf & 0xf0))
 859                        rl[rlpos].lcn = LCN_HOLE;
 860                else {
 861                        /* Get the lcn change which really can be negative. */
 862                        u8 b2 = *buf & 0xf;
 863                        b = b2 + ((*buf >> 4) & 0xf);
 864                        if (buf + b > attr_end)
 865                                goto io_error;
 866                        for (deltaxcn = (s8)buf[b--]; b > b2; b--)
 867                                deltaxcn = (deltaxcn << 8) + buf[b];
 868                        /* Change the current lcn to its new value. */
 869                        lcn += deltaxcn;
 870#ifdef DEBUG
 871                        /*
 872                         * On NTFS 1.2-, apparently can have lcn == -1 to
 873                         * indicate a hole. But we haven't verified ourselves
 874                         * whether it is really the lcn or the deltaxcn that is
 875                         * -1. So if either is found give us a message so we
 876                         * can investigate it further!
 877                         */
 878                        if (vol->major_ver < 3) {
 879                                if (unlikely(deltaxcn == (LCN)-1))
 880                                        ntfs_error(vol->sb, "lcn delta == -1");
 881                                if (unlikely(lcn == (LCN)-1))
 882                                        ntfs_error(vol->sb, "lcn == -1");
 883                        }
 884#endif
 885                        /* Check lcn is not below -1. */
 886                        if (unlikely(lcn < (LCN)-1)) {
 887                                ntfs_error(vol->sb, "Invalid LCN < -1 in "
 888                                                "mapping pairs array.");
 889                                goto err_out;
 890                        }
 891                        /* Enter the current lcn into the runlist element. */
 892                        rl[rlpos].lcn = lcn;
 893                }
 894                /* Get to the next runlist element. */
 895                rlpos++;
 896                /* Increment the buffer position to the next mapping pair. */
 897                buf += (*buf & 0xf) + ((*buf >> 4) & 0xf) + 1;
 898        }
 899        if (unlikely(buf >= attr_end))
 900                goto io_error;
 901        /*
 902         * If there is a highest_vcn specified, it must be equal to the final
 903         * vcn in the runlist - 1, or something has gone badly wrong.
 904         */
 905        deltaxcn = sle64_to_cpu(attr->data.non_resident.highest_vcn);
 906        if (unlikely(deltaxcn && vcn - 1 != deltaxcn)) {
 907mpa_err:
 908                ntfs_error(vol->sb, "Corrupt mapping pairs array in "
 909                                "non-resident attribute.");
 910                goto err_out;
 911        }
 912        /* Setup not mapped runlist element if this is the base extent. */
 913        if (!attr->data.non_resident.lowest_vcn) {
 914                VCN max_cluster;
 915
 916                max_cluster = ((sle64_to_cpu(
 917                                attr->data.non_resident.allocated_size) +
 918                                vol->cluster_size - 1) >>
 919                                vol->cluster_size_bits) - 1;
 920                /*
 921                 * A highest_vcn of zero means this is a single extent
 922                 * attribute so simply terminate the runlist with LCN_ENOENT).
 923                 */
 924                if (deltaxcn) {
 925                        /*
 926                         * If there is a difference between the highest_vcn and
 927                         * the highest cluster, the runlist is either corrupt
 928                         * or, more likely, there are more extents following
 929                         * this one.
 930                         */
 931                        if (deltaxcn < max_cluster) {
 932                                ntfs_debug("More extents to follow; deltaxcn "
 933                                                "= 0x%llx, max_cluster = "
 934                                                "0x%llx",
 935                                                (unsigned long long)deltaxcn,
 936                                                (unsigned long long)
 937                                                max_cluster);
 938                                rl[rlpos].vcn = vcn;
 939                                vcn += rl[rlpos].length = max_cluster -
 940                                                deltaxcn;
 941                                rl[rlpos].lcn = LCN_RL_NOT_MAPPED;
 942                                rlpos++;
 943                        } else if (unlikely(deltaxcn > max_cluster)) {
 944                                ntfs_error(vol->sb, "Corrupt attribute.  "
 945                                                "deltaxcn = 0x%llx, "
 946                                                "max_cluster = 0x%llx",
 947                                                (unsigned long long)deltaxcn,
 948                                                (unsigned long long)
 949                                                max_cluster);
 950                                goto mpa_err;
 951                        }
 952                }
 953                rl[rlpos].lcn = LCN_ENOENT;
 954        } else /* Not the base extent. There may be more extents to follow. */
 955                rl[rlpos].lcn = LCN_RL_NOT_MAPPED;
 956
 957        /* Setup terminating runlist element. */
 958        rl[rlpos].vcn = vcn;
 959        rl[rlpos].length = (s64)0;
 960        /* If no existing runlist was specified, we are done. */
 961        if (!old_rl) {
 962                ntfs_debug("Mapping pairs array successfully decompressed:");
 963                ntfs_debug_dump_runlist(rl);
 964                return rl;
 965        }
 966        /* Now combine the new and old runlists checking for overlaps. */
 967        old_rl = ntfs_runlists_merge(old_rl, rl);
 968        if (likely(!IS_ERR(old_rl)))
 969                return old_rl;
 970        ntfs_free(rl);
 971        ntfs_error(vol->sb, "Failed to merge runlists.");
 972        return old_rl;
 973io_error:
 974        ntfs_error(vol->sb, "Corrupt attribute.");
 975err_out:
 976        ntfs_free(rl);
 977        return ERR_PTR(-EIO);
 978}
 979
 980/**
 981 * ntfs_rl_vcn_to_lcn - convert a vcn into a lcn given a runlist
 982 * @rl:         runlist to use for conversion
 983 * @vcn:        vcn to convert
 984 *
 985 * Convert the virtual cluster number @vcn of an attribute into a logical
 986 * cluster number (lcn) of a device using the runlist @rl to map vcns to their
 987 * corresponding lcns.
 988 *
 989 * It is up to the caller to serialize access to the runlist @rl.
 990 *
 991 * Since lcns must be >= 0, we use negative return codes with special meaning:
 992 *
 993 * Return code          Meaning / Description
 994 * ==================================================
 995 *  LCN_HOLE            Hole / not allocated on disk.
 996 *  LCN_RL_NOT_MAPPED   This is part of the runlist which has not been
 997 *                      inserted into the runlist yet.
 998 *  LCN_ENOENT          There is no such vcn in the attribute.
 999 *
1000 * Locking: - The caller must have locked the runlist (for reading or writing).
1001 *          - This function does not touch the lock, nor does it modify the
1002 *            runlist.
1003 */
1004LCN ntfs_rl_vcn_to_lcn(const runlist_element *rl, const VCN vcn)
1005{
1006        int i;
1007
1008        BUG_ON(vcn < 0);
1009        /*
1010         * If rl is NULL, assume that we have found an unmapped runlist. The
1011         * caller can then attempt to map it and fail appropriately if
1012         * necessary.
1013         */
1014        if (unlikely(!rl))
1015                return LCN_RL_NOT_MAPPED;
1016
1017        /* Catch out of lower bounds vcn. */
1018        if (unlikely(vcn < rl[0].vcn))
1019                return LCN_ENOENT;
1020
1021        for (i = 0; likely(rl[i].length); i++) {
1022                if (unlikely(vcn < rl[i+1].vcn)) {
1023                        if (likely(rl[i].lcn >= (LCN)0))
1024                                return rl[i].lcn + (vcn - rl[i].vcn);
1025                        return rl[i].lcn;
1026                }
1027        }
1028        /*
1029         * The terminator element is setup to the correct value, i.e. one of
1030         * LCN_HOLE, LCN_RL_NOT_MAPPED, or LCN_ENOENT.
1031         */
1032        if (likely(rl[i].lcn < (LCN)0))
1033                return rl[i].lcn;
1034        /* Just in case... We could replace this with BUG() some day. */
1035        return LCN_ENOENT;
1036}
1037
1038#ifdef NTFS_RW
1039
1040/**
1041 * ntfs_rl_find_vcn_nolock - find a vcn in a runlist
1042 * @rl:         runlist to search
1043 * @vcn:        vcn to find
1044 *
1045 * Find the virtual cluster number @vcn in the runlist @rl and return the
1046 * address of the runlist element containing the @vcn on success.
1047 *
1048 * Return NULL if @rl is NULL or @vcn is in an unmapped part/out of bounds of
1049 * the runlist.
1050 *
1051 * Locking: The runlist must be locked on entry.
1052 */
1053runlist_element *ntfs_rl_find_vcn_nolock(runlist_element *rl, const VCN vcn)
1054{
1055        BUG_ON(vcn < 0);
1056        if (unlikely(!rl || vcn < rl[0].vcn))
1057                return NULL;
1058        while (likely(rl->length)) {
1059                if (unlikely(vcn < rl[1].vcn)) {
1060                        if (likely(rl->lcn >= LCN_HOLE))
1061                                return rl;
1062                        return NULL;
1063                }
1064                rl++;
1065        }
1066        if (likely(rl->lcn == LCN_ENOENT))
1067                return rl;
1068        return NULL;
1069}
1070
1071/**
1072 * ntfs_get_nr_significant_bytes - get number of bytes needed to store a number
1073 * @n:          number for which to get the number of bytes for
1074 *
1075 * Return the number of bytes required to store @n unambiguously as
1076 * a signed number.
1077 *
1078 * This is used in the context of the mapping pairs array to determine how
1079 * many bytes will be needed in the array to store a given logical cluster
1080 * number (lcn) or a specific run length.
1081 *
1082 * Return the number of bytes written.  This function cannot fail.
1083 */
1084static inline int ntfs_get_nr_significant_bytes(const s64 n)
1085{
1086        s64 l = n;
1087        int i;
1088        s8 j;
1089
1090        i = 0;
1091        do {
1092                l >>= 8;
1093                i++;
1094        } while (l != 0 && l != -1);
1095        j = (n >> 8 * (i - 1)) & 0xff;
1096        /* If the sign bit is wrong, we need an extra byte. */
1097        if ((n < 0 && j >= 0) || (n > 0 && j < 0))
1098                i++;
1099        return i;
1100}
1101
1102/**
1103 * ntfs_get_size_for_mapping_pairs - get bytes needed for mapping pairs array
1104 * @vol:        ntfs volume (needed for the ntfs version)
1105 * @rl:         locked runlist to determine the size of the mapping pairs of
1106 * @first_vcn:  first vcn which to include in the mapping pairs array
1107 * @last_vcn:   last vcn which to include in the mapping pairs array
1108 *
1109 * Walk the locked runlist @rl and calculate the size in bytes of the mapping
1110 * pairs array corresponding to the runlist @rl, starting at vcn @first_vcn and
1111 * finishing with vcn @last_vcn.
1112 *
1113 * A @last_vcn of -1 means end of runlist and in that case the size of the
1114 * mapping pairs array corresponding to the runlist starting at vcn @first_vcn
1115 * and finishing at the end of the runlist is determined.
1116 *
1117 * This for example allows us to allocate a buffer of the right size when
1118 * building the mapping pairs array.
1119 *
1120 * If @rl is NULL, just return 1 (for the single terminator byte).
1121 *
1122 * Return the calculated size in bytes on success.  On error, return -errno.
1123 * The following error codes are defined:
1124 *      -EINVAL - Run list contains unmapped elements.  Make sure to only pass
1125 *                fully mapped runlists to this function.
1126 *      -EIO    - The runlist is corrupt.
1127 *
1128 * Locking: @rl must be locked on entry (either for reading or writing), it
1129 *          remains locked throughout, and is left locked upon return.
1130 */
1131int ntfs_get_size_for_mapping_pairs(const ntfs_volume *vol,
1132                const runlist_element *rl, const VCN first_vcn,
1133                const VCN last_vcn)
1134{
1135        LCN prev_lcn;
1136        int rls;
1137        bool the_end = false;
1138
1139        BUG_ON(first_vcn < 0);
1140        BUG_ON(last_vcn < -1);
1141        BUG_ON(last_vcn >= 0 && first_vcn > last_vcn);
1142        if (!rl) {
1143                BUG_ON(first_vcn);
1144                BUG_ON(last_vcn > 0);
1145                return 1;
1146        }
1147        /* Skip to runlist element containing @first_vcn. */
1148        while (rl->length && first_vcn >= rl[1].vcn)
1149                rl++;
1150        if (unlikely((!rl->length && first_vcn > rl->vcn) ||
1151                        first_vcn < rl->vcn))
1152                return -EINVAL;
1153        prev_lcn = 0;
1154        /* Always need the termining zero byte. */
1155        rls = 1;
1156        /* Do the first partial run if present. */
1157        if (first_vcn > rl->vcn) {
1158                s64 delta, length = rl->length;
1159
1160                /* We know rl->length != 0 already. */
1161                if (unlikely(length < 0 || rl->lcn < LCN_HOLE))
1162                        goto err_out;
1163                /*
1164                 * If @stop_vcn is given and finishes inside this run, cap the
1165                 * run length.
1166                 */
1167                if (unlikely(last_vcn >= 0 && rl[1].vcn > last_vcn)) {
1168                        s64 s1 = last_vcn + 1;
1169                        if (unlikely(rl[1].vcn > s1))
1170                                length = s1 - rl->vcn;
1171                        the_end = true;
1172                }
1173                delta = first_vcn - rl->vcn;
1174                /* Header byte + length. */
1175                rls += 1 + ntfs_get_nr_significant_bytes(length - delta);
1176                /*
1177                 * If the logical cluster number (lcn) denotes a hole and we
1178                 * are on NTFS 3.0+, we don't store it at all, i.e. we need
1179                 * zero space.  On earlier NTFS versions we just store the lcn.
1180                 * Note: this assumes that on NTFS 1.2-, holes are stored with
1181                 * an lcn of -1 and not a delta_lcn of -1 (unless both are -1).
1182                 */
1183                if (likely(rl->lcn >= 0 || vol->major_ver < 3)) {
1184                        prev_lcn = rl->lcn;
1185                        if (likely(rl->lcn >= 0))
1186                                prev_lcn += delta;
1187                        /* Change in lcn. */
1188                        rls += ntfs_get_nr_significant_bytes(prev_lcn);
1189                }
1190                /* Go to next runlist element. */
1191                rl++;
1192        }
1193        /* Do the full runs. */
1194        for (; rl->length && !the_end; rl++) {
1195                s64 length = rl->length;
1196
1197                if (unlikely(length < 0 || rl->lcn < LCN_HOLE))
1198                        goto err_out;
1199                /*
1200                 * If @stop_vcn is given and finishes inside this run, cap the
1201                 * run length.
1202                 */
1203                if (unlikely(last_vcn >= 0 && rl[1].vcn > last_vcn)) {
1204                        s64 s1 = last_vcn + 1;
1205                        if (unlikely(rl[1].vcn > s1))
1206                                length = s1 - rl->vcn;
1207                        the_end = true;
1208                }
1209                /* Header byte + length. */
1210                rls += 1 + ntfs_get_nr_significant_bytes(length);
1211                /*
1212                 * If the logical cluster number (lcn) denotes a hole and we
1213                 * are on NTFS 3.0+, we don't store it at all, i.e. we need
1214                 * zero space.  On earlier NTFS versions we just store the lcn.
1215                 * Note: this assumes that on NTFS 1.2-, holes are stored with
1216                 * an lcn of -1 and not a delta_lcn of -1 (unless both are -1).
1217                 */
1218                if (likely(rl->lcn >= 0 || vol->major_ver < 3)) {
1219                        /* Change in lcn. */
1220                        rls += ntfs_get_nr_significant_bytes(rl->lcn -
1221                                        prev_lcn);
1222                        prev_lcn = rl->lcn;
1223                }
1224        }
1225        return rls;
1226err_out:
1227        if (rl->lcn == LCN_RL_NOT_MAPPED)
1228                rls = -EINVAL;
1229        else
1230                rls = -EIO;
1231        return rls;
1232}
1233
1234/**
1235 * ntfs_write_significant_bytes - write the significant bytes of a number
1236 * @dst:        destination buffer to write to
1237 * @dst_max:    pointer to last byte of destination buffer for bounds checking
1238 * @n:          number whose significant bytes to write
1239 *
1240 * Store in @dst, the minimum bytes of the number @n which are required to
1241 * identify @n unambiguously as a signed number, taking care not to exceed
1242 * @dest_max, the maximum position within @dst to which we are allowed to
1243 * write.
1244 *
1245 * This is used when building the mapping pairs array of a runlist to compress
1246 * a given logical cluster number (lcn) or a specific run length to the minimum
1247 * size possible.
1248 *
1249 * Return the number of bytes written on success.  On error, i.e. the
1250 * destination buffer @dst is too small, return -ENOSPC.
1251 */
1252static inline int ntfs_write_significant_bytes(s8 *dst, const s8 *dst_max,
1253                const s64 n)
1254{
1255        s64 l = n;
1256        int i;
1257        s8 j;
1258
1259        i = 0;
1260        do {
1261                if (unlikely(dst > dst_max))
1262                        goto err_out;
1263                *dst++ = l & 0xffll;
1264                l >>= 8;
1265                i++;
1266        } while (l != 0 && l != -1);
1267        j = (n >> 8 * (i - 1)) & 0xff;
1268        /* If the sign bit is wrong, we need an extra byte. */
1269        if (n < 0 && j >= 0) {
1270                if (unlikely(dst > dst_max))
1271                        goto err_out;
1272                i++;
1273                *dst = (s8)-1;
1274        } else if (n > 0 && j < 0) {
1275                if (unlikely(dst > dst_max))
1276                        goto err_out;
1277                i++;
1278                *dst = (s8)0;
1279        }
1280        return i;
1281err_out:
1282        return -ENOSPC;
1283}
1284
1285/**
1286 * ntfs_mapping_pairs_build - build the mapping pairs array from a runlist
1287 * @vol:        ntfs volume (needed for the ntfs version)
1288 * @dst:        destination buffer to which to write the mapping pairs array
1289 * @dst_len:    size of destination buffer @dst in bytes
1290 * @rl:         locked runlist for which to build the mapping pairs array
1291 * @first_vcn:  first vcn which to include in the mapping pairs array
1292 * @last_vcn:   last vcn which to include in the mapping pairs array
1293 * @stop_vcn:   first vcn outside destination buffer on success or -ENOSPC
1294 *
1295 * Create the mapping pairs array from the locked runlist @rl, starting at vcn
1296 * @first_vcn and finishing with vcn @last_vcn and save the array in @dst.
1297 * @dst_len is the size of @dst in bytes and it should be at least equal to the
1298 * value obtained by calling ntfs_get_size_for_mapping_pairs().
1299 *
1300 * A @last_vcn of -1 means end of runlist and in that case the mapping pairs
1301 * array corresponding to the runlist starting at vcn @first_vcn and finishing
1302 * at the end of the runlist is created.
1303 *
1304 * If @rl is NULL, just write a single terminator byte to @dst.
1305 *
1306 * On success or -ENOSPC error, if @stop_vcn is not NULL, *@stop_vcn is set to
1307 * the first vcn outside the destination buffer.  Note that on error, @dst has
1308 * been filled with all the mapping pairs that will fit, thus it can be treated
1309 * as partial success, in that a new attribute extent needs to be created or
1310 * the next extent has to be used and the mapping pairs build has to be
1311 * continued with @first_vcn set to *@stop_vcn.
1312 *
1313 * Return 0 on success and -errno on error.  The following error codes are
1314 * defined:
1315 *      -EINVAL - Run list contains unmapped elements.  Make sure to only pass
1316 *                fully mapped runlists to this function.
1317 *      -EIO    - The runlist is corrupt.
1318 *      -ENOSPC - The destination buffer is too small.
1319 *
1320 * Locking: @rl must be locked on entry (either for reading or writing), it
1321 *          remains locked throughout, and is left locked upon return.
1322 */
1323int ntfs_mapping_pairs_build(const ntfs_volume *vol, s8 *dst,
1324                const int dst_len, const runlist_element *rl,
1325                const VCN first_vcn, const VCN last_vcn, VCN *const stop_vcn)
1326{
1327        LCN prev_lcn;
1328        s8 *dst_max, *dst_next;
1329        int err = -ENOSPC;
1330        bool the_end = false;
1331        s8 len_len, lcn_len;
1332
1333        BUG_ON(first_vcn < 0);
1334        BUG_ON(last_vcn < -1);
1335        BUG_ON(last_vcn >= 0 && first_vcn > last_vcn);
1336        BUG_ON(dst_len < 1);
1337        if (!rl) {
1338                BUG_ON(first_vcn);
1339                BUG_ON(last_vcn > 0);
1340                if (stop_vcn)
1341                        *stop_vcn = 0;
1342                /* Terminator byte. */
1343                *dst = 0;
1344                return 0;
1345        }
1346        /* Skip to runlist element containing @first_vcn. */
1347        while (rl->length && first_vcn >= rl[1].vcn)
1348                rl++;
1349        if (unlikely((!rl->length && first_vcn > rl->vcn) ||
1350                        first_vcn < rl->vcn))
1351                return -EINVAL;
1352        /*
1353         * @dst_max is used for bounds checking in
1354         * ntfs_write_significant_bytes().
1355         */
1356        dst_max = dst + dst_len - 1;
1357        prev_lcn = 0;
1358        /* Do the first partial run if present. */
1359        if (first_vcn > rl->vcn) {
1360                s64 delta, length = rl->length;
1361
1362                /* We know rl->length != 0 already. */
1363                if (unlikely(length < 0 || rl->lcn < LCN_HOLE))
1364                        goto err_out;
1365                /*
1366                 * If @stop_vcn is given and finishes inside this run, cap the
1367                 * run length.
1368                 */
1369                if (unlikely(last_vcn >= 0 && rl[1].vcn > last_vcn)) {
1370                        s64 s1 = last_vcn + 1;
1371                        if (unlikely(rl[1].vcn > s1))
1372                                length = s1 - rl->vcn;
1373                        the_end = true;
1374                }
1375                delta = first_vcn - rl->vcn;
1376                /* Write length. */
1377                len_len = ntfs_write_significant_bytes(dst + 1, dst_max,
1378                                length - delta);
1379                if (unlikely(len_len < 0))
1380                        goto size_err;
1381                /*
1382                 * If the logical cluster number (lcn) denotes a hole and we
1383                 * are on NTFS 3.0+, we don't store it at all, i.e. we need
1384                 * zero space.  On earlier NTFS versions we just write the lcn
1385                 * change.  FIXME: Do we need to write the lcn change or just
1386                 * the lcn in that case?  Not sure as I have never seen this
1387                 * case on NT4. - We assume that we just need to write the lcn
1388                 * change until someone tells us otherwise... (AIA)
1389                 */
1390                if (likely(rl->lcn >= 0 || vol->major_ver < 3)) {
1391                        prev_lcn = rl->lcn;
1392                        if (likely(rl->lcn >= 0))
1393                                prev_lcn += delta;
1394                        /* Write change in lcn. */
1395                        lcn_len = ntfs_write_significant_bytes(dst + 1 +
1396                                        len_len, dst_max, prev_lcn);
1397                        if (unlikely(lcn_len < 0))
1398                                goto size_err;
1399                } else
1400                        lcn_len = 0;
1401                dst_next = dst + len_len + lcn_len + 1;
1402                if (unlikely(dst_next > dst_max))
1403                        goto size_err;
1404                /* Update header byte. */
1405                *dst = lcn_len << 4 | len_len;
1406                /* Position at next mapping pairs array element. */
1407                dst = dst_next;
1408                /* Go to next runlist element. */
1409                rl++;
1410        }
1411        /* Do the full runs. */
1412        for (; rl->length && !the_end; rl++) {
1413                s64 length = rl->length;
1414
1415                if (unlikely(length < 0 || rl->lcn < LCN_HOLE))
1416                        goto err_out;
1417                /*
1418                 * If @stop_vcn is given and finishes inside this run, cap the
1419                 * run length.
1420                 */
1421                if (unlikely(last_vcn >= 0 && rl[1].vcn > last_vcn)) {
1422                        s64 s1 = last_vcn + 1;
1423                        if (unlikely(rl[1].vcn > s1))
1424                                length = s1 - rl->vcn;
1425                        the_end = true;
1426                }
1427                /* Write length. */
1428                len_len = ntfs_write_significant_bytes(dst + 1, dst_max,
1429                                length);
1430                if (unlikely(len_len < 0))
1431                        goto size_err;
1432                /*
1433                 * If the logical cluster number (lcn) denotes a hole and we
1434                 * are on NTFS 3.0+, we don't store it at all, i.e. we need
1435                 * zero space.  On earlier NTFS versions we just write the lcn
1436                 * change.  FIXME: Do we need to write the lcn change or just
1437                 * the lcn in that case?  Not sure as I have never seen this
1438                 * case on NT4. - We assume that we just need to write the lcn
1439                 * change until someone tells us otherwise... (AIA)
1440                 */
1441                if (likely(rl->lcn >= 0 || vol->major_ver < 3)) {
1442                        /* Write change in lcn. */
1443                        lcn_len = ntfs_write_significant_bytes(dst + 1 +
1444                                        len_len, dst_max, rl->lcn - prev_lcn);
1445                        if (unlikely(lcn_len < 0))
1446                                goto size_err;
1447                        prev_lcn = rl->lcn;
1448                } else
1449                        lcn_len = 0;
1450                dst_next = dst + len_len + lcn_len + 1;
1451                if (unlikely(dst_next > dst_max))
1452                        goto size_err;
1453                /* Update header byte. */
1454                *dst = lcn_len << 4 | len_len;
1455                /* Position at next mapping pairs array element. */
1456                dst = dst_next;
1457        }
1458        /* Success. */
1459        err = 0;
1460size_err:
1461        /* Set stop vcn. */
1462        if (stop_vcn)
1463                *stop_vcn = rl->vcn;
1464        /* Add terminator byte. */
1465        *dst = 0;
1466        return err;
1467err_out:
1468        if (rl->lcn == LCN_RL_NOT_MAPPED)
1469                err = -EINVAL;
1470        else
1471                err = -EIO;
1472        return err;
1473}
1474
1475/**
1476 * ntfs_rl_truncate_nolock - truncate a runlist starting at a specified vcn
1477 * @vol:        ntfs volume (needed for error output)
1478 * @runlist:    runlist to truncate
1479 * @new_length: the new length of the runlist in VCNs
1480 *
1481 * Truncate the runlist described by @runlist as well as the memory buffer
1482 * holding the runlist elements to a length of @new_length VCNs.
1483 *
1484 * If @new_length lies within the runlist, the runlist elements with VCNs of
1485 * @new_length and above are discarded.  As a special case if @new_length is
1486 * zero, the runlist is discarded and set to NULL.
1487 *
1488 * If @new_length lies beyond the runlist, a sparse runlist element is added to
1489 * the end of the runlist @runlist or if the last runlist element is a sparse
1490 * one already, this is extended.
1491 *
1492 * Note, no checking is done for unmapped runlist elements.  It is assumed that
1493 * the caller has mapped any elements that need to be mapped already.
1494 *
1495 * Return 0 on success and -errno on error.
1496 *
1497 * Locking: The caller must hold @runlist->lock for writing.
1498 */
1499int ntfs_rl_truncate_nolock(const ntfs_volume *vol, runlist *const runlist,
1500                const s64 new_length)
1501{
1502        runlist_element *rl;
1503        int old_size;
1504
1505        ntfs_debug("Entering for new_length 0x%llx.", (long long)new_length);
1506        BUG_ON(!runlist);
1507        BUG_ON(new_length < 0);
1508        rl = runlist->rl;
1509        if (!new_length) {
1510                ntfs_debug("Freeing runlist.");
1511                runlist->rl = NULL;
1512                if (rl)
1513                        ntfs_free(rl);
1514                return 0;
1515        }
1516        if (unlikely(!rl)) {
1517                /*
1518                 * Create a runlist consisting of a sparse runlist element of
1519                 * length @new_length followed by a terminator runlist element.
1520                 */
1521                rl = ntfs_malloc_nofs(PAGE_SIZE);
1522                if (unlikely(!rl)) {
1523                        ntfs_error(vol->sb, "Not enough memory to allocate "
1524                                        "runlist element buffer.");
1525                        return -ENOMEM;
1526                }
1527                runlist->rl = rl;
1528                rl[1].length = rl->vcn = 0;
1529                rl->lcn = LCN_HOLE;
1530                rl[1].vcn = rl->length = new_length;
1531                rl[1].lcn = LCN_ENOENT;
1532                return 0;
1533        }
1534        BUG_ON(new_length < rl->vcn);
1535        /* Find @new_length in the runlist. */
1536        while (likely(rl->length && new_length >= rl[1].vcn))
1537                rl++;
1538        /*
1539         * If not at the end of the runlist we need to shrink it.
1540         * If at the end of the runlist we need to expand it.
1541         */
1542        if (rl->length) {
1543                runlist_element *trl;
1544                bool is_end;
1545
1546                ntfs_debug("Shrinking runlist.");
1547                /* Determine the runlist size. */
1548                trl = rl + 1;
1549                while (likely(trl->length))
1550                        trl++;
1551                old_size = trl - runlist->rl + 1;
1552                /* Truncate the run. */
1553                rl->length = new_length - rl->vcn;
1554                /*
1555                 * If a run was partially truncated, make the following runlist
1556                 * element a terminator.
1557                 */
1558                is_end = false;
1559                if (rl->length) {
1560                        rl++;
1561                        if (!rl->length)
1562                                is_end = true;
1563                        rl->vcn = new_length;
1564                        rl->length = 0;
1565                }
1566                rl->lcn = LCN_ENOENT;
1567                /* Reallocate memory if necessary. */
1568                if (!is_end) {
1569                        int new_size = rl - runlist->rl + 1;
1570                        rl = ntfs_rl_realloc(runlist->rl, old_size, new_size);
1571                        if (IS_ERR(rl))
1572                                ntfs_warning(vol->sb, "Failed to shrink "
1573                                                "runlist buffer.  This just "
1574                                                "wastes a bit of memory "
1575                                                "temporarily so we ignore it "
1576                                                "and return success.");
1577                        else
1578                                runlist->rl = rl;
1579                }
1580        } else if (likely(/* !rl->length && */ new_length > rl->vcn)) {
1581                ntfs_debug("Expanding runlist.");
1582                /*
1583                 * If there is a previous runlist element and it is a sparse
1584                 * one, extend it.  Otherwise need to add a new, sparse runlist
1585                 * element.
1586                 */
1587                if ((rl > runlist->rl) && ((rl - 1)->lcn == LCN_HOLE))
1588                        (rl - 1)->length = new_length - (rl - 1)->vcn;
1589                else {
1590                        /* Determine the runlist size. */
1591                        old_size = rl - runlist->rl + 1;
1592                        /* Reallocate memory if necessary. */
1593                        rl = ntfs_rl_realloc(runlist->rl, old_size,
1594                                        old_size + 1);
1595                        if (IS_ERR(rl)) {
1596                                ntfs_error(vol->sb, "Failed to expand runlist "
1597                                                "buffer, aborting.");
1598                                return PTR_ERR(rl);
1599                        }
1600                        runlist->rl = rl;
1601                        /*
1602                         * Set @rl to the same runlist element in the new
1603                         * runlist as before in the old runlist.
1604                         */
1605                        rl += old_size - 1;
1606                        /* Add a new, sparse runlist element. */
1607                        rl->lcn = LCN_HOLE;
1608                        rl->length = new_length - rl->vcn;
1609                        /* Add a new terminator runlist element. */
1610                        rl++;
1611                        rl->length = 0;
1612                }
1613                rl->vcn = new_length;
1614                rl->lcn = LCN_ENOENT;
1615        } else /* if (unlikely(!rl->length && new_length == rl->vcn)) */ {
1616                /* Runlist already has same size as requested. */
1617                rl->lcn = LCN_ENOENT;
1618        }
1619        ntfs_debug("Done.");
1620        return 0;
1621}
1622
1623/**
1624 * ntfs_rl_punch_nolock - punch a hole into a runlist
1625 * @vol:        ntfs volume (needed for error output)
1626 * @runlist:    runlist to punch a hole into
1627 * @start:      starting VCN of the hole to be created
1628 * @length:     size of the hole to be created in units of clusters
1629 *
1630 * Punch a hole into the runlist @runlist starting at VCN @start and of size
1631 * @length clusters.
1632 *
1633 * Return 0 on success and -errno on error, in which case @runlist has not been
1634 * modified.
1635 *
1636 * If @start and/or @start + @length are outside the runlist return error code
1637 * -ENOENT.
1638 *
1639 * If the runlist contains unmapped or error elements between @start and @start
1640 * + @length return error code -EINVAL.
1641 *
1642 * Locking: The caller must hold @runlist->lock for writing.
1643 */
1644int ntfs_rl_punch_nolock(const ntfs_volume *vol, runlist *const runlist,
1645                const VCN start, const s64 length)
1646{
1647        const VCN end = start + length;
1648        s64 delta;
1649        runlist_element *rl, *rl_end, *rl_real_end, *trl;
1650        int old_size;
1651        bool lcn_fixup = false;
1652
1653        ntfs_debug("Entering for start 0x%llx, length 0x%llx.",
1654                        (long long)start, (long long)length);
1655        BUG_ON(!runlist);
1656        BUG_ON(start < 0);
1657        BUG_ON(length < 0);
1658        BUG_ON(end < 0);
1659        rl = runlist->rl;
1660        if (unlikely(!rl)) {
1661                if (likely(!start && !length))
1662                        return 0;
1663                return -ENOENT;
1664        }
1665        /* Find @start in the runlist. */
1666        while (likely(rl->length && start >= rl[1].vcn))
1667                rl++;
1668        rl_end = rl;
1669        /* Find @end in the runlist. */
1670        while (likely(rl_end->length && end >= rl_end[1].vcn)) {
1671                /* Verify there are no unmapped or error elements. */
1672                if (unlikely(rl_end->lcn < LCN_HOLE))
1673                        return -EINVAL;
1674                rl_end++;
1675        }
1676        /* Check the last element. */
1677        if (unlikely(rl_end->length && rl_end->lcn < LCN_HOLE))
1678                return -EINVAL;
1679        /* This covers @start being out of bounds, too. */
1680        if (!rl_end->length && end > rl_end->vcn)
1681                return -ENOENT;
1682        if (!length)
1683                return 0;
1684        if (!rl->length)
1685                return -ENOENT;
1686        rl_real_end = rl_end;
1687        /* Determine the runlist size. */
1688        while (likely(rl_real_end->length))
1689                rl_real_end++;
1690        old_size = rl_real_end - runlist->rl + 1;
1691        /* If @start is in a hole simply extend the hole. */
1692        if (rl->lcn == LCN_HOLE) {
1693                /*
1694                 * If both @start and @end are in the same sparse run, we are
1695                 * done.
1696                 */
1697                if (end <= rl[1].vcn) {
1698                        ntfs_debug("Done (requested hole is already sparse).");
1699                        return 0;
1700                }
1701extend_hole:
1702                /* Extend the hole. */
1703                rl->length = end - rl->vcn;
1704                /* If @end is in a hole, merge it with the current one. */
1705                if (rl_end->lcn == LCN_HOLE) {
1706                        rl_end++;
1707                        rl->length = rl_end->vcn - rl->vcn;
1708                }
1709                /* We have done the hole.  Now deal with the remaining tail. */
1710                rl++;
1711                /* Cut out all runlist elements up to @end. */
1712                if (rl < rl_end)
1713                        memmove(rl, rl_end, (rl_real_end - rl_end + 1) *
1714                                        sizeof(*rl));
1715                /* Adjust the beginning of the tail if necessary. */
1716                if (end > rl->vcn) {
1717                        delta = end - rl->vcn;
1718                        rl->vcn = end;
1719                        rl->length -= delta;
1720                        /* Only adjust the lcn if it is real. */
1721                        if (rl->lcn >= 0)
1722                                rl->lcn += delta;
1723                }
1724shrink_allocation:
1725                /* Reallocate memory if the allocation changed. */
1726                if (rl < rl_end) {
1727                        rl = ntfs_rl_realloc(runlist->rl, old_size,
1728                                        old_size - (rl_end - rl));
1729                        if (IS_ERR(rl))
1730                                ntfs_warning(vol->sb, "Failed to shrink "
1731                                                "runlist buffer.  This just "
1732                                                "wastes a bit of memory "
1733                                                "temporarily so we ignore it "
1734                                                "and return success.");
1735                        else
1736                                runlist->rl = rl;
1737                }
1738                ntfs_debug("Done (extend hole).");
1739                return 0;
1740        }
1741        /*
1742         * If @start is at the beginning of a run things are easier as there is
1743         * no need to split the first run.
1744         */
1745        if (start == rl->vcn) {
1746                /*
1747                 * @start is at the beginning of a run.
1748                 *
1749                 * If the previous run is sparse, extend its hole.
1750                 *
1751                 * If @end is not in the same run, switch the run to be sparse
1752                 * and extend the newly created hole.
1753                 *
1754                 * Thus both of these cases reduce the problem to the above
1755                 * case of "@start is in a hole".
1756                 */
1757                if (rl > runlist->rl && (rl - 1)->lcn == LCN_HOLE) {
1758                        rl--;
1759                        goto extend_hole;
1760                }
1761                if (end >= rl[1].vcn) {
1762                        rl->lcn = LCN_HOLE;
1763                        goto extend_hole;
1764                }
1765                /*
1766                 * The final case is when @end is in the same run as @start.
1767                 * For this need to split the run into two.  One run for the
1768                 * sparse region between the beginning of the old run, i.e.
1769                 * @start, and @end and one for the remaining non-sparse
1770                 * region, i.e. between @end and the end of the old run.
1771                 */
1772                trl = ntfs_rl_realloc(runlist->rl, old_size, old_size + 1);
1773                if (IS_ERR(trl))
1774                        goto enomem_out;
1775                old_size++;
1776                if (runlist->rl != trl) {
1777                        rl = trl + (rl - runlist->rl);
1778                        rl_end = trl + (rl_end - runlist->rl);
1779                        rl_real_end = trl + (rl_real_end - runlist->rl);
1780                        runlist->rl = trl;
1781                }
1782split_end:
1783                /* Shift all the runs up by one. */
1784                memmove(rl + 1, rl, (rl_real_end - rl + 1) * sizeof(*rl));
1785                /* Finally, setup the two split runs. */
1786                rl->lcn = LCN_HOLE;
1787                rl->length = length;
1788                rl++;
1789                rl->vcn += length;
1790                /* Only adjust the lcn if it is real. */
1791                if (rl->lcn >= 0 || lcn_fixup)
1792                        rl->lcn += length;
1793                rl->length -= length;
1794                ntfs_debug("Done (split one).");
1795                return 0;
1796        }
1797        /*
1798         * @start is neither in a hole nor at the beginning of a run.
1799         *
1800         * If @end is in a hole, things are easier as simply truncating the run
1801         * @start is in to end at @start - 1, deleting all runs after that up
1802         * to @end, and finally extending the beginning of the run @end is in
1803         * to be @start is all that is needed.
1804         */
1805        if (rl_end->lcn == LCN_HOLE) {
1806                /* Truncate the run containing @start. */
1807                rl->length = start - rl->vcn;
1808                rl++;
1809                /* Cut out all runlist elements up to @end. */
1810                if (rl < rl_end)
1811                        memmove(rl, rl_end, (rl_real_end - rl_end + 1) *
1812                                        sizeof(*rl));
1813                /* Extend the beginning of the run @end is in to be @start. */
1814                rl->vcn = start;
1815                rl->length = rl[1].vcn - start;
1816                goto shrink_allocation;
1817        }
1818        /* 
1819         * If @end is not in a hole there are still two cases to distinguish.
1820         * Either @end is or is not in the same run as @start.
1821         *
1822         * The second case is easier as it can be reduced to an already solved
1823         * problem by truncating the run @start is in to end at @start - 1.
1824         * Then, if @end is in the next run need to split the run into a sparse
1825         * run followed by a non-sparse run (already covered above) and if @end
1826         * is not in the next run switching it to be sparse, again reduces the
1827         * problem to the already covered case of "@start is in a hole".
1828         */
1829        if (end >= rl[1].vcn) {
1830                /*
1831                 * If @end is not in the next run, reduce the problem to the
1832                 * case of "@start is in a hole".
1833                 */
1834                if (rl[1].length && end >= rl[2].vcn) {
1835                        /* Truncate the run containing @start. */
1836                        rl->length = start - rl->vcn;
1837                        rl++;
1838                        rl->vcn = start;
1839                        rl->lcn = LCN_HOLE;
1840                        goto extend_hole;
1841                }
1842                trl = ntfs_rl_realloc(runlist->rl, old_size, old_size + 1);
1843                if (IS_ERR(trl))
1844                        goto enomem_out;
1845                old_size++;
1846                if (runlist->rl != trl) {
1847                        rl = trl + (rl - runlist->rl);
1848                        rl_end = trl + (rl_end - runlist->rl);
1849                        rl_real_end = trl + (rl_real_end - runlist->rl);
1850                        runlist->rl = trl;
1851                }
1852                /* Truncate the run containing @start. */
1853                rl->length = start - rl->vcn;
1854                rl++;
1855                /*
1856                 * @end is in the next run, reduce the problem to the case
1857                 * where "@start is at the beginning of a run and @end is in
1858                 * the same run as @start".
1859                 */
1860                delta = rl->vcn - start;
1861                rl->vcn = start;
1862                if (rl->lcn >= 0) {
1863                        rl->lcn -= delta;
1864                        /* Need this in case the lcn just became negative. */
1865                        lcn_fixup = true;
1866                }
1867                rl->length += delta;
1868                goto split_end;
1869        }
1870        /*
1871         * The first case from above, i.e. @end is in the same run as @start.
1872         * We need to split the run into three.  One run for the non-sparse
1873         * region between the beginning of the old run and @start, one for the
1874         * sparse region between @start and @end, and one for the remaining
1875         * non-sparse region, i.e. between @end and the end of the old run.
1876         */
1877        trl = ntfs_rl_realloc(runlist->rl, old_size, old_size + 2);
1878        if (IS_ERR(trl))
1879                goto enomem_out;
1880        old_size += 2;
1881        if (runlist->rl != trl) {
1882                rl = trl + (rl - runlist->rl);
1883                rl_end = trl + (rl_end - runlist->rl);
1884                rl_real_end = trl + (rl_real_end - runlist->rl);
1885                runlist->rl = trl;
1886        }
1887        /* Shift all the runs up by two. */
1888        memmove(rl + 2, rl, (rl_real_end - rl + 1) * sizeof(*rl));
1889        /* Finally, setup the three split runs. */
1890        rl->length = start - rl->vcn;
1891        rl++;
1892        rl->vcn = start;
1893        rl->lcn = LCN_HOLE;
1894        rl->length = length;
1895        rl++;
1896        delta = end - rl->vcn;
1897        rl->vcn = end;
1898        rl->lcn += delta;
1899        rl->length -= delta;
1900        ntfs_debug("Done (split both).");
1901        return 0;
1902enomem_out:
1903        ntfs_error(vol->sb, "Not enough memory to extend runlist buffer.");
1904        return -ENOMEM;
1905}
1906
1907#endif /* NTFS_RW */
1908
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