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 */