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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /**
  * runlist.c - NTFS runlist handling code.  Part of the Linux-NTFS project.
  *
  * Copyright (c) 2001-2007 Anton Altaparmakov
  * Copyright (c) 2002-2005 Richard Russon
  */
 
 #include "debug.h"
 #include "dir.h"
 #include "endian.h"
 #include "malloc.h"
 #include "ntfs.h"
 
 /**
  * ntfs_rl_mm - runlist memmove
  *
  * It is up to the caller to serialize access to the runlist @base.
  */
 static inline void ntfs_rl_mm(runlist_element *base, int dst, int src,
         int size)
 {
     if (likely((dst != src) && (size > 0)))
         memmove(base + dst, base + src, size * sizeof(*base));
 }
 
 /**
  * ntfs_rl_mc - runlist memory copy
  *
  * It is up to the caller to serialize access to the runlists @dstbase and
  * @srcbase.
  */
 static inline void ntfs_rl_mc(runlist_element *dstbase, int dst,
         runlist_element *srcbase, int src, int size)
 {
     if (likely(size > 0))
         memcpy(dstbase + dst, srcbase + src, size * sizeof(*dstbase));
 }
 
 /**
  * ntfs_rl_realloc - Reallocate memory for runlists
  * @rl:     original runlist
  * @old_size:   number of runlist elements in the original runlist @rl
  * @new_size:   number of runlist elements we need space for
  *
  * As the runlists grow, more memory will be required.  To prevent the
  * kernel having to allocate and reallocate large numbers of small bits of
  * memory, this function returns an entire page of memory.
  *
  * It is up to the caller to serialize access to the runlist @rl.
  *
  * N.B.  If the new allocation doesn't require a different number of pages in
  *       memory, the function will return the original pointer.
  *
  * On success, return a pointer to the newly allocated, or recycled, memory.
  * On error, return -errno. The following error codes are defined:
  *  -ENOMEM - Not enough memory to allocate runlist array.
  *  -EINVAL - Invalid parameters were passed in.
  */
 static inline runlist_element *ntfs_rl_realloc(runlist_element *rl,
         int old_size, int new_size)
 {
     runlist_element *new_rl;
 
     old_size = PAGE_ALIGN(old_size * sizeof(*rl));
     new_size = PAGE_ALIGN(new_size * sizeof(*rl));
     if (old_size == new_size)
         return rl;
 
     new_rl = ntfs_malloc_nofs(new_size);
     if (unlikely(!new_rl))
         return ERR_PTR(-ENOMEM);
 
     if (likely(rl != NULL)) {
         if (unlikely(old_size > new_size))
             old_size = new_size;
         memcpy(new_rl, rl, old_size);
         ntfs_free(rl);
     }
     return new_rl;
 }
 
 /**
  * ntfs_rl_realloc_nofail - Reallocate memory for runlists
  * @rl:     original runlist
  * @old_size:   number of runlist elements in the original runlist @rl
  * @new_size:   number of runlist elements we need space for
  *
  * As the runlists grow, more memory will be required.  To prevent the
  * kernel having to allocate and reallocate large numbers of small bits of
  * memory, this function returns an entire page of memory.
  *
  * This function guarantees that the allocation will succeed.  It will sleep
  * for as long as it takes to complete the allocation.
  *
  * It is up to the caller to serialize access to the runlist @rl.
  *
  * N.B.  If the new allocation doesn't require a different number of pages in
  *       memory, the function will return the original pointer.
  *
  * On success, return a pointer to the newly allocated, or recycled, memory.
  * On error, return -errno. The following error codes are defined:
  *  -ENOMEM - Not enough memory to allocate runlist array.
  *  -EINVAL - Invalid parameters were passed in.
  */
 static inline runlist_element *ntfs_rl_realloc_nofail(runlist_element *rl,
         int old_size, int new_size)
 {
     runlist_element *new_rl;
 
     old_size = PAGE_ALIGN(old_size * sizeof(*rl));
     new_size = PAGE_ALIGN(new_size * sizeof(*rl));
     if (old_size == new_size)
         return rl;
 
     new_rl = ntfs_malloc_nofs_nofail(new_size);
     BUG_ON(!new_rl);
 
     if (likely(rl != NULL)) {
         if (unlikely(old_size > new_size))
             old_size = new_size;
         memcpy(new_rl, rl, old_size);
         ntfs_free(rl);
     }
     return new_rl;
 }
 
 /**
  * ntfs_are_rl_mergeable - test if two runlists can be joined together
  * @dst:    original runlist
  * @src:    new runlist to test for mergeability with @dst
  *
  * Test if two runlists can be joined together. For this, their VCNs and LCNs
  * must be adjacent.
  *
  * It is up to the caller to serialize access to the runlists @dst and @src.
  *
  * Return: true   Success, the runlists can be merged.
  *     false  Failure, the runlists cannot be merged.
  */
 static inline bool ntfs_are_rl_mergeable(runlist_element *dst,
         runlist_element *src)
 {
     BUG_ON(!dst);
     BUG_ON(!src);
 
     /* We can merge unmapped regions even if they are misaligned. */
     if ((dst->lcn == LCN_RL_NOT_MAPPED) && (src->lcn == LCN_RL_NOT_MAPPED))
         return true;
     /* If the runs are misaligned, we cannot merge them. */
     if ((dst->vcn + dst->length) != src->vcn)
         return false;
     /* If both runs are non-sparse and contiguous, we can merge them. */
     if ((dst->lcn >= 0) && (src->lcn >= 0) &&
             ((dst->lcn + dst->length) == src->lcn))
         return true;
     /* If we are merging two holes, we can merge them. */
     if ((dst->lcn == LCN_HOLE) && (src->lcn == LCN_HOLE))
         return true;
     /* Cannot merge. */
     return false;
 }
 
 /**
  * __ntfs_rl_merge - merge two runlists without testing if they can be merged
  * @dst:    original, destination runlist
  * @src:    new runlist to merge with @dst
  *
  * Merge the two runlists, writing into the destination runlist @dst. The
  * caller must make sure the runlists can be merged or this will corrupt the
  * destination runlist.
  *
  * It is up to the caller to serialize access to the runlists @dst and @src.
  */
 static inline void __ntfs_rl_merge(runlist_element *dst, runlist_element *src)
 {
     dst->length += src->length;
 }
 
 /**
  * ntfs_rl_append - append a runlist after a given element
  * @dst:    original runlist to be worked on
  * @dsize:  number of elements in @dst (including end marker)
  * @src:    runlist to be inserted into @dst
  * @ssize:  number of elements in @src (excluding end marker)
  * @loc:    append the new runlist @src after this element in @dst
  *
  * Append the runlist @src after element @loc in @dst.  Merge the right end of
  * the new runlist, if necessary. Adjust the size of the hole before the
  * appended runlist.
  *
  * It is up to the caller to serialize access to the runlists @dst and @src.
  *
  * On success, return a pointer to the new, combined, runlist. Note, both
  * runlists @dst and @src are deallocated before returning so you cannot use
  * the pointers for anything any more. (Strictly speaking the returned runlist
  * may be the same as @dst but this is irrelevant.)
  *
  * On error, return -errno. Both runlists are left unmodified. The following
  * error codes are defined:
  *  -ENOMEM - Not enough memory to allocate runlist array.
  *  -EINVAL - Invalid parameters were passed in.
  */
 static inline runlist_element *ntfs_rl_append(runlist_element *dst,
         int dsize, runlist_element *src, int ssize, int loc)
 {
     bool right = false; /* Right end of @src needs merging. */
     int marker;     /* End of the inserted runs. */
 
     BUG_ON(!dst);
     BUG_ON(!src);
 
     /* First, check if the right hand end needs merging. */
     if ((loc + 1) < dsize)
         right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
 
     /* Space required: @dst size + @src size, less one if we merged. */
     dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - right);
     if (IS_ERR(dst))
         return dst;
     /*
      * We are guaranteed to succeed from here so can start modifying the
      * original runlists.
      */
 
     /* First, merge the right hand end, if necessary. */
     if (right)
         __ntfs_rl_merge(src + ssize - 1, dst + loc + 1);
 
     /* First run after the @src runs that have been inserted. */
     marker = loc + ssize + 1;
 
     /* Move the tail of @dst out of the way, then copy in @src. */
     ntfs_rl_mm(dst, marker, loc + 1 + right, dsize - (loc + 1 + right));
     ntfs_rl_mc(dst, loc + 1, src, 0, ssize);
 
     /* Adjust the size of the preceding hole. */
     dst[loc].length = dst[loc + 1].vcn - dst[loc].vcn;
 
     /* We may have changed the length of the file, so fix the end marker */
     if (dst[marker].lcn == LCN_ENOENT)
         dst[marker].vcn = dst[marker - 1].vcn + dst[marker - 1].length;
 
     return dst;
 }
 
 /**
  * ntfs_rl_insert - insert a runlist into another
  * @dst:    original runlist to be worked on
  * @dsize:  number of elements in @dst (including end marker)
  * @src:    new runlist to be inserted
  * @ssize:  number of elements in @src (excluding end marker)
  * @loc:    insert the new runlist @src before this element in @dst
  *
  * Insert the runlist @src before element @loc in the runlist @dst. Merge the
  * left end of the new runlist, if necessary. Adjust the size of the hole
  * after the inserted runlist.
  *
  * It is up to the caller to serialize access to the runlists @dst and @src.
  *
  * On success, return a pointer to the new, combined, runlist. Note, both
  * runlists @dst and @src are deallocated before returning so you cannot use
  * the pointers for anything any more. (Strictly speaking the returned runlist
  * may be the same as @dst but this is irrelevant.)
  *
  * On error, return -errno. Both runlists are left unmodified. The following
  * error codes are defined:
  *  -ENOMEM - Not enough memory to allocate runlist array.
  *  -EINVAL - Invalid parameters were passed in.
  */
 static inline runlist_element *ntfs_rl_insert(runlist_element *dst,
         int dsize, runlist_element *src, int ssize, int loc)
 {
     bool left = false;  /* Left end of @src needs merging. */
     bool disc = false;  /* Discontinuity between @dst and @src. */
     int marker;     /* End of the inserted runs. */
 
     BUG_ON(!dst);
     BUG_ON(!src);
 
     /*
      * disc => Discontinuity between the end of @dst and the start of @src.
      *     This means we might need to insert a "not mapped" run.
      */
     if (loc == 0)
         disc = (src[0].vcn > 0);
     else {
         s64 merged_length;
 
         left = ntfs_are_rl_mergeable(dst + loc - 1, src);
 
         merged_length = dst[loc - 1].length;
         if (left)
             merged_length += src->length;
 
         disc = (src[0].vcn > dst[loc - 1].vcn + merged_length);
     }
     /*
      * Space required: @dst size + @src size, less one if we merged, plus
      * one if there was a discontinuity.
      */
     dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - left + disc);
     if (IS_ERR(dst))
         return dst;
     /*
      * We are guaranteed to succeed from here so can start modifying the
      * original runlist.
      */
     if (left)
         __ntfs_rl_merge(dst + loc - 1, src);
     /*
      * First run after the @src runs that have been inserted.
      * Nominally,  @marker equals @loc + @ssize, i.e. location + number of
      * runs in @src.  However, if @left, then the first run in @src has
      * been merged with one in @dst.  And if @disc, then @dst and @src do
      * not meet and we need an extra run to fill the gap.
      */
     marker = loc + ssize - left + disc;
 
     /* Move the tail of @dst out of the way, then copy in @src. */
     ntfs_rl_mm(dst, marker, loc, dsize - loc);
     ntfs_rl_mc(dst, loc + disc, src, left, ssize - left);
 
     /* Adjust the VCN of the first run after the insertion... */
     dst[marker].vcn = dst[marker - 1].vcn + dst[marker - 1].length;
     /* ... and the length. */
     if (dst[marker].lcn == LCN_HOLE || dst[marker].lcn == LCN_RL_NOT_MAPPED)
         dst[marker].length = dst[marker + 1].vcn - dst[marker].vcn;
 
     /* Writing beyond the end of the file and there is a discontinuity. */
     if (disc) {
         if (loc > 0) {
             dst[loc].vcn = dst[loc - 1].vcn + dst[loc - 1].length;
             dst[loc].length = dst[loc + 1].vcn - dst[loc].vcn;
         } else {
             dst[loc].vcn = 0;
             dst[loc].length = dst[loc + 1].vcn;
         }
         dst[loc].lcn = LCN_RL_NOT_MAPPED;
     }
     return dst;
 }
 
 /**
  * ntfs_rl_replace - overwrite a runlist element with another runlist
  * @dst:    original runlist to be worked on
  * @dsize:  number of elements in @dst (including end marker)
  * @src:    new runlist to be inserted
  * @ssize:  number of elements in @src (excluding end marker)
  * @loc:    index in runlist @dst to overwrite with @src
  *
  * Replace the runlist element @dst at @loc with @src. Merge the left and
  * right ends of the inserted runlist, if necessary.
  *
  * It is up to the caller to serialize access to the runlists @dst and @src.
  *
  * On success, return a pointer to the new, combined, runlist. Note, both
  * runlists @dst and @src are deallocated before returning so you cannot use
  * the pointers for anything any more. (Strictly speaking the returned runlist
  * may be the same as @dst but this is irrelevant.)
  *
  * On error, return -errno. Both runlists are left unmodified. The following
  * error codes are defined:
  *  -ENOMEM - Not enough memory to allocate runlist array.
  *  -EINVAL - Invalid parameters were passed in.
  */
 static inline runlist_element *ntfs_rl_replace(runlist_element *dst,
         int dsize, runlist_element *src, int ssize, int loc)
 {
     signed delta;
     bool left = false;  /* Left end of @src needs merging. */
     bool right = false; /* Right end of @src needs merging. */
     int tail;       /* Start of tail of @dst. */
     int marker;     /* End of the inserted runs. */
 
     BUG_ON(!dst);
     BUG_ON(!src);
 
     /* First, see if the left and right ends need merging. */
     if ((loc + 1) < dsize)
         right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
     if (loc > 0)
         left = ntfs_are_rl_mergeable(dst + loc - 1, src);
     /*
      * Allocate some space.  We will need less if the left, right, or both
      * ends get merged.  The -1 accounts for the run being replaced.
      */
     delta = ssize - 1 - left - right;
     if (delta > 0) {
         dst = ntfs_rl_realloc(dst, dsize, dsize + delta);
         if (IS_ERR(dst))
             return dst;
     }
     /*
      * We are guaranteed to succeed from here so can start modifying the
      * original runlists.
      */
 
     /* First, merge the left and right ends, if necessary. */
     if (right)
         __ntfs_rl_merge(src + ssize - 1, dst + loc + 1);
     if (left)
         __ntfs_rl_merge(dst + loc - 1, src);
     /*
      * Offset of the tail of @dst.  This needs to be moved out of the way
      * to make space for the runs to be copied from @src, i.e. the first
      * run of the tail of @dst.
      * Nominally, @tail equals @loc + 1, i.e. location, skipping the
      * replaced run.  However, if @right, then one of @dst's runs is
      * already merged into @src.
      */
     tail = loc + right + 1;
     /*
      * First run after the @src runs that have been inserted, i.e. where
      * the tail of @dst needs to be moved to.
      * Nominally, @marker equals @loc + @ssize, i.e. location + number of
      * runs in @src.  However, if @left, then the first run in @src has
      * been merged with one in @dst.
      */
     marker = loc + ssize - left;
 
     /* Move the tail of @dst out of the way, then copy in @src. */
     ntfs_rl_mm(dst, marker, tail, dsize - tail);
     ntfs_rl_mc(dst, loc, src, left, ssize - left);
 
     /* We may have changed the length of the file, so fix the end marker. */
     if (dsize - tail > 0 && dst[marker].lcn == LCN_ENOENT)
         dst[marker].vcn = dst[marker - 1].vcn + dst[marker - 1].length;
     return dst;
 }
 
 /**
  * ntfs_rl_split - insert a runlist into the centre of a hole
  * @dst:    original runlist to be worked on
  * @dsize:  number of elements in @dst (including end marker)
  * @src:    new runlist to be inserted
  * @ssize:  number of elements in @src (excluding end marker)
  * @loc:    index in runlist @dst at which to split and insert @src
  *
  * Split the runlist @dst at @loc into two and insert @new in between the two
  * fragments. No merging of runlists is necessary. Adjust the size of the
  * holes either side.
  *
  * It is up to the caller to serialize access to the runlists @dst and @src.
  *
  * On success, return a pointer to the new, combined, runlist. Note, both
  * runlists @dst and @src are deallocated before returning so you cannot use
  * the pointers for anything any more. (Strictly speaking the returned runlist
  * may be the same as @dst but this is irrelevant.)
  *
  * On error, return -errno. Both runlists are left unmodified. The following
  * error codes are defined:
  *  -ENOMEM - Not enough memory to allocate runlist array.
  *  -EINVAL - Invalid parameters were passed in.
  */
 static inline runlist_element *ntfs_rl_split(runlist_element *dst, int dsize,
         runlist_element *src, int ssize, int loc)
 {
     BUG_ON(!dst);
     BUG_ON(!src);
 
     /* Space required: @dst size + @src size + one new hole. */
     dst = ntfs_rl_realloc(dst, dsize, dsize + ssize + 1);
     if (IS_ERR(dst))
         return dst;
     /*
      * We are guaranteed to succeed from here so can start modifying the
      * original runlists.
      */
 
     /* Move the tail of @dst out of the way, then copy in @src. */
     ntfs_rl_mm(dst, loc + 1 + ssize, loc, dsize - loc);
     ntfs_rl_mc(dst, loc + 1, src, 0, ssize);
 
     /* Adjust the size of the holes either size of @src. */
     dst[loc].length     = dst[loc+1].vcn       - dst[loc].vcn;
     dst[loc+ssize+1].vcn    = dst[loc+ssize].vcn   + dst[loc+ssize].length;
     dst[loc+ssize+1].length = dst[loc+ssize+2].vcn - dst[loc+ssize+1].vcn;
 
     return dst;
 }
 
 /**
  * ntfs_runlists_merge - merge two runlists into one
  * @drl:    original runlist to be worked on
  * @srl:    new runlist to be merged into @drl
  *
  * First we sanity check the two runlists @srl and @drl to make sure that they
  * are sensible and can be merged. The runlist @srl must be either after the
  * runlist @drl or completely within a hole (or unmapped region) in @drl.
  *
  * It is up to the caller to serialize access to the runlists @drl and @srl.
  *
  * Merging of runlists is necessary in two cases:
  *   1. When attribute lists are used and a further extent is being mapped.
  *   2. When new clusters are allocated to fill a hole or extend a file.
  *
  * There are four possible ways @srl can be merged. It can:
  *  - be inserted at the beginning of a hole,
  *  - split the hole in two and be inserted between the two fragments,
  *  - be appended at the end of a hole, or it can
  *  - replace the whole hole.
  * It can also be appended to the end of the runlist, which is just a variant
  * of the insert case.
  *
  * On success, return a pointer to the new, combined, runlist. Note, both
  * runlists @drl and @srl are deallocated before returning so you cannot use
  * the pointers for anything any more. (Strictly speaking the returned runlist
  * may be the same as @dst but this is irrelevant.)
  *
  * On error, return -errno. Both runlists are left unmodified. The following
  * error codes are defined:
  *  -ENOMEM - Not enough memory to allocate runlist array.
  *  -EINVAL - Invalid parameters were passed in.
  *  -ERANGE - The runlists overlap and cannot be merged.
  */
 runlist_element *ntfs_runlists_merge(runlist_element *drl,
         runlist_element *srl)
 {
     int di, si;     /* Current index into @[ds]rl. */
     int sstart;     /* First index with lcn > LCN_RL_NOT_MAPPED. */
     int dins;       /* Index into @drl at which to insert @srl. */
     int dend, send;     /* Last index into @[ds]rl. */
     int dfinal, sfinal; /* The last index into @[ds]rl with
                    lcn >= LCN_HOLE. */
     int marker = 0;
     VCN marker_vcn = 0;
 
 #ifdef DEBUG
     ntfs_debug("dst:");
     ntfs_debug_dump_runlist(drl);
     ntfs_debug("src:");
     ntfs_debug_dump_runlist(srl);
 #endif
 
     /* Check for silly calling... */
     if (unlikely(!srl))
         return drl;
     if (IS_ERR(srl) || IS_ERR(drl))
         return ERR_PTR(-EINVAL);
 
     /* Check for the case where the first mapping is being done now. */
     if (unlikely(!drl)) {
         drl = srl;
         /* Complete the source runlist if necessary. */
         if (unlikely(drl[0].vcn)) {
             /* Scan to the end of the source runlist. */
             for (dend = 0; likely(drl[dend].length); dend++)
                 ;
             dend++;
             drl = ntfs_rl_realloc(drl, dend, dend + 1);
             if (IS_ERR(drl))
                 return drl;
             /* Insert start element at the front of the runlist. */
             ntfs_rl_mm(drl, 1, 0, dend);
             drl[0].vcn = 0;
             drl[0].lcn = LCN_RL_NOT_MAPPED;
             drl[0].length = drl[1].vcn;
         }
         goto finished;
     }
 
     si = di = 0;
 
     /* Skip any unmapped start element(s) in the source runlist. */
     while (srl[si].length && srl[si].lcn < LCN_HOLE)
         si++;
 
     /* Can't have an entirely unmapped source runlist. */
     BUG_ON(!srl[si].length);
 
     /* Record the starting points. */
     sstart = si;
 
     /*
      * Skip forward in @drl until we reach the position where @srl needs to
      * be inserted. If we reach the end of @drl, @srl just needs to be
      * appended to @drl.
      */
     for (; drl[di].length; di++) {
         if (drl[di].vcn + drl[di].length > srl[sstart].vcn)
             break;
     }
     dins = di;
 
     /* Sanity check for illegal overlaps. */
     if ((drl[di].vcn == srl[si].vcn) && (drl[di].lcn >= 0) &&
             (srl[si].lcn >= 0)) {
         ntfs_error(NULL, "Run lists overlap. Cannot merge!");
         return ERR_PTR(-ERANGE);
     }
 
     /* Scan to the end of both runlists in order to know their sizes. */
     for (send = si; srl[send].length; send++)
         ;
     for (dend = di; drl[dend].length; dend++)
         ;
 
     if (srl[send].lcn == LCN_ENOENT)
         marker_vcn = srl[marker = send].vcn;
 
     /* Scan to the last element with lcn >= LCN_HOLE. */
     for (sfinal = send; sfinal >= 0 && srl[sfinal].lcn < LCN_HOLE; sfinal--)
         ;
     for (dfinal = dend; dfinal >= 0 && drl[dfinal].lcn < LCN_HOLE; dfinal--)
         ;
 
     {
     bool start;
     bool finish;
     int ds = dend + 1;      /* Number of elements in drl & srl */
     int ss = sfinal - sstart + 1;
 
     start  = ((drl[dins].lcn <  LCN_RL_NOT_MAPPED) ||    /* End of file   */
           (drl[dins].vcn == srl[sstart].vcn));       /* Start of hole */
     finish = ((drl[dins].lcn >= LCN_RL_NOT_MAPPED) &&    /* End of file   */
          ((drl[dins].vcn + drl[dins].length) <=      /* End of hole   */
           (srl[send - 1].vcn + srl[send - 1].length)));
 
     /* Or we will lose an end marker. */
     if (finish && !drl[dins].length)
         ss++;
     if (marker && (drl[dins].vcn + drl[dins].length > srl[send - 1].vcn))
         finish = false;
 #if 0
     ntfs_debug("dfinal = %i, dend = %i", dfinal, dend);
     ntfs_debug("sstart = %i, sfinal = %i, send = %i", sstart, sfinal, send);
     ntfs_debug("start = %i, finish = %i", start, finish);
     ntfs_debug("ds = %i, ss = %i, dins = %i", ds, ss, dins);
 #endif
     if (start) {
         if (finish)
             drl = ntfs_rl_replace(drl, ds, srl + sstart, ss, dins);
         else
             drl = ntfs_rl_insert(drl, ds, srl + sstart, ss, dins);
     } else {
         if (finish)
             drl = ntfs_rl_append(drl, ds, srl + sstart, ss, dins);
         else
             drl = ntfs_rl_split(drl, ds, srl + sstart, ss, dins);
     }
     if (IS_ERR(drl)) {
         ntfs_error(NULL, "Merge failed.");
         return drl;
     }
     ntfs_free(srl);
     if (marker) {
         ntfs_debug("Triggering marker code.");
         for (ds = dend; drl[ds].length; ds++)
             ;
         /* We only need to care if @srl ended after @drl. */
         if (drl[ds].vcn <= marker_vcn) {
             int slots = 0;
 
             if (drl[ds].vcn == marker_vcn) {
                 ntfs_debug("Old marker = 0x%llx, replacing "
                         "with LCN_ENOENT.",
                         (unsigned long long)
                         drl[ds].lcn);
                 drl[ds].lcn = LCN_ENOENT;
                 goto finished;
             }
             /*
              * We need to create an unmapped runlist element in
              * @drl or extend an existing one before adding the
              * ENOENT terminator.
              */
             if (drl[ds].lcn == LCN_ENOENT) {
                 ds--;
                 slots = 1;
             }
             if (drl[ds].lcn != LCN_RL_NOT_MAPPED) {
                 /* Add an unmapped runlist element. */
                 if (!slots) {
                     drl = ntfs_rl_realloc_nofail(drl, ds,
                             ds + 2);
                     slots = 2;
                 }
                 ds++;
                 /* Need to set vcn if it isn't set already. */
                 if (slots != 1)
                     drl[ds].vcn = drl[ds - 1].vcn +
                             drl[ds - 1].length;
                 drl[ds].lcn = LCN_RL_NOT_MAPPED;
                 /* We now used up a slot. */
                 slots--;
             }
             drl[ds].length = marker_vcn - drl[ds].vcn;
             /* Finally add the ENOENT terminator. */
             ds++;
             if (!slots)
                 drl = ntfs_rl_realloc_nofail(drl, ds, ds + 1);
             drl[ds].vcn = marker_vcn;
             drl[ds].lcn = LCN_ENOENT;
             drl[ds].length = (s64)0;
         }
     }
     }
 
 finished:
     /* The merge was completed successfully. */
     ntfs_debug("Merged runlist:");
     ntfs_debug_dump_runlist(drl);
     return drl;
 }
 
 /**
  * ntfs_mapping_pairs_decompress - convert mapping pairs array to runlist
  * @vol:    ntfs volume on which the attribute resides
  * @attr:   attribute record whose mapping pairs array to decompress
  * @old_rl: optional runlist in which to insert @attr's runlist
  *
  * It is up to the caller to serialize access to the runlist @old_rl.
  *
  * Decompress the attribute @attr's mapping pairs array into a runlist. On
  * success, return the decompressed runlist.
  *
  * If @old_rl is not NULL, decompressed runlist is inserted into the
  * appropriate place in @old_rl and the resultant, combined runlist is
  * returned. The original @old_rl is deallocated.
  *
  * On error, return -errno. @old_rl is left unmodified in that case.
  *
  * The following error codes are defined:
  *  -ENOMEM - Not enough memory to allocate runlist array.
  *  -EIO    - Corrupt runlist.
  *  -EINVAL - Invalid parameters were passed in.
  *  -ERANGE - The two runlists overlap.
  *
  * FIXME: For now we take the conceptionally simplest approach of creating the
  * new runlist disregarding the already existing one and then splicing the
  * two into one, if that is possible (we check for overlap and discard the new
  * runlist if overlap present before returning ERR_PTR(-ERANGE)).
  */
 runlist_element *ntfs_mapping_pairs_decompress(const ntfs_volume *vol,
         const ATTR_RECORD *attr, runlist_element *old_rl)
 {
     VCN vcn;        /* Current vcn. */
     LCN lcn;        /* Current lcn. */
     s64 deltaxcn;       /* Change in [vl]cn. */
     runlist_element *rl;    /* The output runlist. */
     u8 *buf;        /* Current position in mapping pairs array. */
     u8 *attr_end;       /* End of attribute. */
     int rlsize;     /* Size of runlist buffer. */
     u16 rlpos;      /* Current runlist position in units of
                    runlist_elements. */
     u8 b;           /* Current byte offset in buf. */
 
 #ifdef DEBUG
     /* Make sure attr exists and is non-resident. */
     if (!attr || !attr->non_resident || sle64_to_cpu(
             attr->data.non_resident.lowest_vcn) < (VCN)0) {
         ntfs_error(vol->sb, "Invalid arguments.");
         return ERR_PTR(-EINVAL);
     }
 #endif
     /* Start at vcn = lowest_vcn and lcn 0. */
     vcn = sle64_to_cpu(attr->data.non_resident.lowest_vcn);
     lcn = 0;
     /* Get start of the mapping pairs array. */
     buf = (u8*)attr + le16_to_cpu(
             attr->data.non_resident.mapping_pairs_offset);
     attr_end = (u8*)attr + le32_to_cpu(attr->length);
     if (unlikely(buf < (u8*)attr || buf > attr_end)) {
         ntfs_error(vol->sb, "Corrupt attribute.");
         return ERR_PTR(-EIO);
     }
     /* If the mapping pairs array is valid but empty, nothing to do. */
     if (!vcn && !*buf)
         return old_rl;
     /* Current position in runlist array. */
     rlpos = 0;
     /* Allocate first page and set current runlist size to one page. */
     rl = ntfs_malloc_nofs(rlsize = PAGE_SIZE);
     if (unlikely(!rl))
         return ERR_PTR(-ENOMEM);
     /* Insert unmapped starting element if necessary. */
     if (vcn) {
         rl->vcn = 0;
         rl->lcn = LCN_RL_NOT_MAPPED;
         rl->length = vcn;
         rlpos++;
     }
     while (buf < attr_end && *buf) {
         /*
          * Allocate more memory if needed, including space for the
          * not-mapped and terminator elements. ntfs_malloc_nofs()
          * operates on whole pages only.
          */
         if (((rlpos + 3) * sizeof(*old_rl)) > rlsize) {
             runlist_element *rl2;
 
             rl2 = ntfs_malloc_nofs(rlsize + (int)PAGE_SIZE);
             if (unlikely(!rl2)) {
                 ntfs_free(rl);
                 return ERR_PTR(-ENOMEM);
             }
             memcpy(rl2, rl, rlsize);
             ntfs_free(rl);
             rl = rl2;
             rlsize += PAGE_SIZE;
         }
         /* Enter the current vcn into the current runlist element. */
         rl[rlpos].vcn = vcn;
         /*
          * Get the change in vcn, i.e. the run length in clusters.
          * Doing it this way ensures that we signextend negative values.
          * A negative run length doesn't make any sense, but hey, I
          * didn't make up the NTFS specs and Windows NT4 treats the run
          * length as a signed value so that's how it is...
          */
         b = *buf & 0xf;
         if (b) {
             if (unlikely(buf + b > attr_end))
                 goto io_error;
             for (deltaxcn = (s8)buf[b--]; b; b--)
                 deltaxcn = (deltaxcn << 8) + buf[b];
         } else { /* The length entry is compulsory. */
             ntfs_error(vol->sb, "Missing length entry in mapping "
                     "pairs array.");
             deltaxcn = (s64)-1;
         }
         /*
          * Assume a negative length to indicate data corruption and
          * hence clean-up and return NULL.
          */
         if (unlikely(deltaxcn < 0)) {
             ntfs_error(vol->sb, "Invalid length in mapping pairs "
                     "array.");
             goto err_out;
         }
         /*
          * Enter the current run length into the current runlist
          * element.
          */
         rl[rlpos].length = deltaxcn;
         /* Increment the current vcn by the current run length. */
         vcn += deltaxcn;
         /*
          * There might be no lcn change at all, as is the case for
          * sparse clusters on NTFS 3.0+, in which case we set the lcn
          * to LCN_HOLE.
          */
         if (!(*buf & 0xf0))
             rl[rlpos].lcn = LCN_HOLE;
         else {
             /* Get the lcn change which really can be negative. */
             u8 b2 = *buf & 0xf;
             b = b2 + ((*buf >> 4) & 0xf);
             if (buf + b > attr_end)
                 goto io_error;
             for (deltaxcn = (s8)buf[b--]; b > b2; b--)
                 deltaxcn = (deltaxcn << 8) + buf[b];
             /* Change the current lcn to its new value. */
             lcn += deltaxcn;
 #ifdef DEBUG
             /*
              * On NTFS 1.2-, apparently can have lcn == -1 to
              * indicate a hole. But we haven't verified ourselves
              * whether it is really the lcn or the deltaxcn that is
              * -1. So if either is found give us a message so we
              * can investigate it further!
              */
             if (vol->major_ver < 3) {
                 if (unlikely(deltaxcn == (LCN)-1))
                     ntfs_error(vol->sb, "lcn delta == -1");
                 if (unlikely(lcn == (LCN)-1))
                     ntfs_error(vol->sb, "lcn == -1");
             }
 #endif
             /* Check lcn is not below -1. */
             if (unlikely(lcn < (LCN)-1)) {
                 ntfs_error(vol->sb, "Invalid LCN < -1 in "
                         "mapping pairs array.");
                 goto err_out;
             }
             /* Enter the current lcn into the runlist element. */
             rl[rlpos].lcn = lcn;
         }
         /* Get to the next runlist element. */
         rlpos++;
         /* Increment the buffer position to the next mapping pair. */
         buf += (*buf & 0xf) + ((*buf >> 4) & 0xf) + 1;
     }
     if (unlikely(buf >= attr_end))
         goto io_error;
     /*
      * If there is a highest_vcn specified, it must be equal to the final
      * vcn in the runlist - 1, or something has gone badly wrong.
      */
     deltaxcn = sle64_to_cpu(attr->data.non_resident.highest_vcn);
     if (unlikely(deltaxcn && vcn - 1 != deltaxcn)) {
 mpa_err:
         ntfs_error(vol->sb, "Corrupt mapping pairs array in "
                 "non-resident attribute.");
         goto err_out;
     }
     /* Setup not mapped runlist element if this is the base extent. */
     if (!attr->data.non_resident.lowest_vcn) {
         VCN max_cluster;
 
         max_cluster = ((sle64_to_cpu(
                 attr->data.non_resident.allocated_size) +
                 vol->cluster_size - 1) >>
                 vol->cluster_size_bits) - 1;
         /*
          * A highest_vcn of zero means this is a single extent
          * attribute so simply terminate the runlist with LCN_ENOENT).
          */
         if (deltaxcn) {
             /*
              * If there is a difference between the highest_vcn and
              * the highest cluster, the runlist is either corrupt
              * or, more likely, there are more extents following
              * this one.
              */
             if (deltaxcn < max_cluster) {
                 ntfs_debug("More extents to follow; deltaxcn "
                         "= 0x%llx, max_cluster = "
                         "0x%llx",
                         (unsigned long long)deltaxcn,
                         (unsigned long long)
                         max_cluster);
                 rl[rlpos].vcn = vcn;
                 vcn += rl[rlpos].length = max_cluster -
                         deltaxcn;
                 rl[rlpos].lcn = LCN_RL_NOT_MAPPED;
                 rlpos++;
             } else if (unlikely(deltaxcn > max_cluster)) {
                 ntfs_error(vol->sb, "Corrupt attribute.  "
                         "deltaxcn = 0x%llx, "
                         "max_cluster = 0x%llx",
                         (unsigned long long)deltaxcn,
                         (unsigned long long)
                         max_cluster);
                 goto mpa_err;
             }
         }
         rl[rlpos].lcn = LCN_ENOENT;
     } else /* Not the base extent. There may be more extents to follow. */
         rl[rlpos].lcn = LCN_RL_NOT_MAPPED;
 
     /* Setup terminating runlist element. */
     rl[rlpos].vcn = vcn;
     rl[rlpos].length = (s64)0;
     /* If no existing runlist was specified, we are done. */
     if (!old_rl) {
         ntfs_debug("Mapping pairs array successfully decompressed:");
         ntfs_debug_dump_runlist(rl);
         return rl;
     }
     /* Now combine the new and old runlists checking for overlaps. */
     old_rl = ntfs_runlists_merge(old_rl, rl);
     if (!IS_ERR(old_rl))
         return old_rl;
     ntfs_free(rl);
     ntfs_error(vol->sb, "Failed to merge runlists.");
     return old_rl;
 io_error:
     ntfs_error(vol->sb, "Corrupt attribute.");
 err_out:
     ntfs_free(rl);
     return ERR_PTR(-EIO);
 }
 
 /**
  * ntfs_rl_vcn_to_lcn - convert a vcn into a lcn given a runlist
  * @rl:     runlist to use for conversion
  * @vcn:    vcn to convert
  *
  * Convert the virtual cluster number @vcn of an attribute into a logical
  * cluster number (lcn) of a device using the runlist @rl to map vcns to their
  * corresponding lcns.
  *
  * It is up to the caller to serialize access to the runlist @rl.
  *
  * Since lcns must be >= 0, we use negative return codes with special meaning:
  *
  * Return code      Meaning / Description
  * ==================================================
  *  LCN_HOLE        Hole / not allocated on disk.
  *  LCN_RL_NOT_MAPPED   This is part of the runlist which has not been
  *          inserted into the runlist yet.
  *  LCN_ENOENT      There is no such vcn in the attribute.
  *
  * Locking: - The caller must have locked the runlist (for reading or writing).
  *      - This function does not touch the lock, nor does it modify the
  *        runlist.
  */
 LCN ntfs_rl_vcn_to_lcn(const runlist_element *rl, const VCN vcn)
 {
     int i;
 
     BUG_ON(vcn < 0);
     /*
      * If rl is NULL, assume that we have found an unmapped runlist. The
      * caller can then attempt to map it and fail appropriately if
      * necessary.
      */
     if (unlikely(!rl))
         return LCN_RL_NOT_MAPPED;
 
     /* Catch out of lower bounds vcn. */
     if (unlikely(vcn < rl[0].vcn))
         return LCN_ENOENT;
 
     for (i = 0; likely(rl[i].length); i++) {
         if (unlikely(vcn < rl[i+1].vcn)) {
             if (likely(rl[i].lcn >= (LCN)0))
                 return rl[i].lcn + (vcn - rl[i].vcn);
             return rl[i].lcn;
         }
     }
     /*
      * The terminator element is setup to the correct value, i.e. one of
      * LCN_HOLE, LCN_RL_NOT_MAPPED, or LCN_ENOENT.
      */
     if (likely(rl[i].lcn < (LCN)0))
         return rl[i].lcn;
     /* Just in case... We could replace this with BUG() some day. */
     return LCN_ENOENT;
 }
 
 #ifdef NTFS_RW
 
 /**
  * ntfs_rl_find_vcn_nolock - find a vcn in a runlist
  * @rl:     runlist to search
  * @vcn:    vcn to find
  *
  * Find the virtual cluster number @vcn in the runlist @rl and return the
  * address of the runlist element containing the @vcn on success.
  *
  * Return NULL if @rl is NULL or @vcn is in an unmapped part/out of bounds of
  * the runlist.
  *
  * Locking: The runlist must be locked on entry.
  */
 runlist_element *ntfs_rl_find_vcn_nolock(runlist_element *rl, const VCN vcn)
 {
     BUG_ON(vcn < 0);
     if (unlikely(!rl || vcn < rl[0].vcn))
         return NULL;
     while (likely(rl->length)) {
         if (unlikely(vcn < rl[1].vcn)) {
             if (likely(rl->lcn >= LCN_HOLE))
                 return rl;
             return NULL;
         }
         rl++;
     }
     if (likely(rl->lcn == LCN_ENOENT))
         return rl;
     return NULL;
 }
 
 /**
  * ntfs_get_nr_significant_bytes - get number of bytes needed to store a number
  * @n:      number for which to get the number of bytes for
  *
  * Return the number of bytes required to store @n unambiguously as
  * a signed number.
  *
  * This is used in the context of the mapping pairs array to determine how
  * many bytes will be needed in the array to store a given logical cluster
  * number (lcn) or a specific run length.
  *
  * Return the number of bytes written.  This function cannot fail.
  */
 static inline int ntfs_get_nr_significant_bytes(const s64 n)
 {
     s64 l = n;
     int i;
     s8 j;
 
     i = 0;
     do {
         l >>= 8;
         i++;
     } while (l != 0 && l != -1);
     j = (n >> 8 * (i - 1)) & 0xff;
     /* If the sign bit is wrong, we need an extra byte. */
     if ((n < 0 && j >= 0) || (n > 0 && j < 0))
         i++;
     return i;
 }
 
 /**
  * ntfs_get_size_for_mapping_pairs - get bytes needed for mapping pairs array
  * @vol:    ntfs volume (needed for the ntfs version)
  * @rl:     locked runlist to determine the size of the mapping pairs of
  * @first_vcn:  first vcn which to include in the mapping pairs array
  * @last_vcn:   last vcn which to include in the mapping pairs array
  *
  * Walk the locked runlist @rl and calculate the size in bytes of the mapping
  * pairs array corresponding to the runlist @rl, starting at vcn @first_vcn and
  * finishing with vcn @last_vcn.
  *
  * A @last_vcn of -1 means end of runlist and in that case the size of the
  * mapping pairs array corresponding to the runlist starting at vcn @first_vcn
  * and finishing at the end of the runlist is determined.
  *
  * This for example allows us to allocate a buffer of the right size when
  * building the mapping pairs array.
  *
  * If @rl is NULL, just return 1 (for the single terminator byte).
  *
  * Return the calculated size in bytes on success.  On error, return -errno.
  * The following error codes are defined:
  *  -EINVAL - Run list contains unmapped elements.  Make sure to only pass
  *        fully mapped runlists to this function.
  *  -EIO    - The runlist is corrupt.
  *
  * Locking: @rl must be locked on entry (either for reading or writing), it
  *      remains locked throughout, and is left locked upon return.
  */
 int ntfs_get_size_for_mapping_pairs(const ntfs_volume *vol,
         const runlist_element *rl, const VCN first_vcn,
         const VCN last_vcn)
 {
     LCN prev_lcn;
     int rls;
     bool the_end = false;
 
     BUG_ON(first_vcn < 0);
     BUG_ON(last_vcn < -1);
     BUG_ON(last_vcn >= 0 && first_vcn > last_vcn);
     if (!rl) {
         BUG_ON(first_vcn);
         BUG_ON(last_vcn > 0);
         return 1;
     }
     /* Skip to runlist element containing @first_vcn. */
     while (rl->length && first_vcn >= rl[1].vcn)
         rl++;
     if (unlikely((!rl->length && first_vcn > rl->vcn) ||
             first_vcn < rl->vcn))
         return -EINVAL;
     prev_lcn = 0;
     /* Always need the termining zero byte. */
     rls = 1;
     /* Do the first partial run if present. */
     if (first_vcn > rl->vcn) {
         s64 delta, length = rl->length;
 
         /* We know rl->length != 0 already. */
         if (unlikely(length < 0 || rl->lcn < LCN_HOLE))
             goto err_out;
         /*
          * If @stop_vcn is given and finishes inside this run, cap the
          * run length.
          */
         if (unlikely(last_vcn >= 0 && rl[1].vcn > last_vcn)) {
             s64 s1 = last_vcn + 1;
             if (unlikely(rl[1].vcn > s1))
                 length = s1 - rl->vcn;
             the_end = true;
         }
         delta = first_vcn - rl->vcn;
         /* Header byte + length. */
         rls += 1 + ntfs_get_nr_significant_bytes(length - delta);
         /*
          * If the logical cluster number (lcn) denotes a hole and we
          * are on NTFS 3.0+, we don't store it at all, i.e. we need
          * zero space.  On earlier NTFS versions we just store the lcn.
          * Note: this assumes that on NTFS 1.2-, holes are stored with
          * an lcn of -1 and not a delta_lcn of -1 (unless both are -1).
          */
         if (likely(rl->lcn >= 0 || vol->major_ver < 3)) {
             prev_lcn = rl->lcn;
             if (likely(rl->lcn >= 0))
                 prev_lcn += delta;
             /* Change in lcn. */
             rls += ntfs_get_nr_significant_bytes(prev_lcn);
         }
         /* Go to next runlist element. */
         rl++;
     }
     /* Do the full runs. */
     for (; rl->length && !the_end; rl++) {
         s64 length = rl->length;
 
         if (unlikely(length < 0 || rl->lcn < LCN_HOLE))
             goto err_out;
         /*
          * If @stop_vcn is given and finishes inside this run, cap the
          * run length.
          */
         if (unlikely(last_vcn >= 0 && rl[1].vcn > last_vcn)) {
             s64 s1 = last_vcn + 1;
             if (unlikely(rl[1].vcn > s1))
                 length = s1 - rl->vcn;
             the_end = true;
         }
         /* Header byte + length. */
         rls += 1 + ntfs_get_nr_significant_bytes(length);
         /*
          * If the logical cluster number (lcn) denotes a hole and we
          * are on NTFS 3.0+, we don't store it at all, i.e. we need
          * zero space.  On earlier NTFS versions we just store the lcn.
          * Note: this assumes that on NTFS 1.2-, holes are stored with
          * an lcn of -1 and not a delta_lcn of -1 (unless both are -1).
          */
         if (likely(rl->lcn >= 0 || vol->major_ver < 3)) {
             /* Change in lcn. */
             rls += ntfs_get_nr_significant_bytes(rl->lcn -
                     prev_lcn);
             prev_lcn = rl->lcn;
         }
     }
     return rls;
 err_out:
     if (rl->lcn == LCN_RL_NOT_MAPPED)
         rls = -EINVAL;
     else
         rls = -EIO;
     return rls;
 }
 
 /**
  * ntfs_write_significant_bytes - write the significant bytes of a number
  * @dst:    destination buffer to write to
  * @dst_max:    pointer to last byte of destination buffer for bounds checking
  * @n:      number whose significant bytes to write
  *
  * Store in @dst, the minimum bytes of the number @n which are required to
  * identify @n unambiguously as a signed number, taking care not to exceed
  * @dest_max, the maximum position within @dst to which we are allowed to
  * write.
  *
  * This is used when building the mapping pairs array of a runlist to compress
  * a given logical cluster number (lcn) or a specific run length to the minimum
  * size possible.
  *
  * Return the number of bytes written on success.  On error, i.e. the
  * destination buffer @dst is too small, return -ENOSPC.
  */
 static inline int ntfs_write_significant_bytes(s8 *dst, const s8 *dst_max,
         const s64 n)
 {
     s64 l = n;
     int i;
     s8 j;
 
     i = 0;
     do {
         if (unlikely(dst > dst_max))
             goto err_out;
         *dst++ = l & 0xffll;
         l >>= 8;
         i++;
     } while (l != 0 && l != -1);
     j = (n >> 8 * (i - 1)) & 0xff;
     /* If the sign bit is wrong, we need an extra byte. */
     if (n < 0 && j >= 0) {
         if (unlikely(dst > dst_max))
             goto err_out;
         i++;
         *dst = (s8)-1;
     } else if (n > 0 && j < 0) {
         if (unlikely(dst > dst_max))
             goto err_out;
         i++;
         *dst = (s8)0;
     }
     return i;
 err_out:
     return -ENOSPC;
 }
 
 /**
  * ntfs_mapping_pairs_build - build the mapping pairs array from a runlist
  * @vol:    ntfs volume (needed for the ntfs version)
  * @dst:    destination buffer to which to write the mapping pairs array
  * @dst_len:    size of destination buffer @dst in bytes
  * @rl:     locked runlist for which to build the mapping pairs array
  * @first_vcn:  first vcn which to include in the mapping pairs array
  * @last_vcn:   last vcn which to include in the mapping pairs array
  * @stop_vcn:   first vcn outside destination buffer on success or -ENOSPC
  *
  * Create the mapping pairs array from the locked runlist @rl, starting at vcn
  * @first_vcn and finishing with vcn @last_vcn and save the array in @dst.
  * @dst_len is the size of @dst in bytes and it should be at least equal to the
  * value obtained by calling ntfs_get_size_for_mapping_pairs().
  *
  * A @last_vcn of -1 means end of runlist and in that case the mapping pairs
  * array corresponding to the runlist starting at vcn @first_vcn and finishing
  * at the end of the runlist is created.
  *
  * If @rl is NULL, just write a single terminator byte to @dst.
  *
  * On success or -ENOSPC error, if @stop_vcn is not NULL, *@stop_vcn is set to
  * the first vcn outside the destination buffer.  Note that on error, @dst has
  * been filled with all the mapping pairs that will fit, thus it can be treated
  * as partial success, in that a new attribute extent needs to be created or
  * the next extent has to be used and the mapping pairs build has to be
  * continued with @first_vcn set to *@stop_vcn.
  *
  * Return 0 on success and -errno on error.  The following error codes are
  * defined:
  *  -EINVAL - Run list contains unmapped elements.  Make sure to only pass
  *        fully mapped runlists to this function.
  *  -EIO    - The runlist is corrupt.
  *  -ENOSPC - The destination buffer is too small.
  *
  * Locking: @rl must be locked on entry (either for reading or writing), it
  *      remains locked throughout, and is left locked upon return.
  */
 int ntfs_mapping_pairs_build(const ntfs_volume *vol, s8 *dst,
         const int dst_len, const runlist_element *rl,
         const VCN first_vcn, const VCN last_vcn, VCN *const stop_vcn)
 {
     LCN prev_lcn;
     s8 *dst_max, *dst_next;
     int err = -ENOSPC;
     bool the_end = false;
     s8 len_len, lcn_len;
 
     BUG_ON(first_vcn < 0);
     BUG_ON(last_vcn < -1);
     BUG_ON(last_vcn >= 0 && first_vcn > last_vcn);
     BUG_ON(dst_len < 1);
     if (!rl) {
         BUG_ON(first_vcn);
         BUG_ON(last_vcn > 0);
         if (stop_vcn)
             *stop_vcn = 0;
         /* Terminator byte. */
         *dst = 0;
         return 0;
     }
     /* Skip to runlist element containing @first_vcn. */
     while (rl->length && first_vcn >= rl[1].vcn)
         rl++;
     if (unlikely((!rl->length && first_vcn > rl->vcn) ||
             first_vcn < rl->vcn))
         return -EINVAL;
     /*
      * @dst_max is used for bounds checking in
      * ntfs_write_significant_bytes().
      */
     dst_max = dst + dst_len - 1;
     prev_lcn = 0;
     /* Do the first partial run if present. */
     if (first_vcn > rl->vcn) {
         s64 delta, length = rl->length;
 
         /* We know rl->length != 0 already. */
         if (unlikely(length < 0 || rl->lcn < LCN_HOLE))
             goto err_out;
         /*
          * If @stop_vcn is given and finishes inside this run, cap the
          * run length.
          */
         if (unlikely(last_vcn >= 0 && rl[1].vcn > last_vcn)) {
             s64 s1 = last_vcn + 1;
             if (unlikely(rl[1].vcn > s1))
                 length = s1 - rl->vcn;
             the_end = true;
         }
         delta = first_vcn - rl->vcn;
         /* Write length. */
         len_len = ntfs_write_significant_bytes(dst + 1, dst_max,
                 length - delta);
         if (unlikely(len_len < 0))
             goto size_err;
         /*
          * If the logical cluster number (lcn) denotes a hole and we
          * are on NTFS 3.0+, we don't store it at all, i.e. we need
          * zero space.  On earlier NTFS versions we just write the lcn
          * change.  FIXME: Do we need to write the lcn change or just
          * the lcn in that case?  Not sure as I have never seen this
          * case on NT4. - We assume that we just need to write the lcn
          * change until someone tells us otherwise... (AIA)
          */
         if (likely(rl->lcn >= 0 || vol->major_ver < 3)) {
             prev_lcn = rl->lcn;
             if (likely(rl->lcn >= 0))
                 prev_lcn += delta;
             /* Write change in lcn. */
             lcn_len = ntfs_write_significant_bytes(dst + 1 +
                     len_len, dst_max, prev_lcn);
             if (unlikely(lcn_len < 0))
                 goto size_err;
         } else
             lcn_len = 0;
         dst_next = dst + len_len + lcn_len + 1;
         if (unlikely(dst_next > dst_max))
             goto size_err;
         /* Update header byte. */
         *dst = lcn_len << 4 | len_len;
         /* Position at next mapping pairs array element. */
         dst = dst_next;
         /* Go to next runlist element. */
         rl++;
     }
     /* Do the full runs. */
     for (; rl->length && !the_end; rl++) {
         s64 length = rl->length;
 
         if (unlikely(length < 0 || rl->lcn < LCN_HOLE))
             goto err_out;
         /*
          * If @stop_vcn is given and finishes inside this run, cap the
          * run length.
          */
         if (unlikely(last_vcn >= 0 && rl[1].vcn > last_vcn)) {
             s64 s1 = last_vcn + 1;
             if (unlikely(rl[1].vcn > s1))
                 length = s1 - rl->vcn;
             the_end = true;
         }
         /* Write length. */
         len_len = ntfs_write_significant_bytes(dst + 1, dst_max,
                 length);
         if (unlikely(len_len < 0))
             goto size_err;
         /*
          * If the logical cluster number (lcn) denotes a hole and we
          * are on NTFS 3.0+, we don't store it at all, i.e. we need
          * zero space.  On earlier NTFS versions we just write the lcn
          * change.  FIXME: Do we need to write the lcn change or just
          * the lcn in that case?  Not sure as I have never seen this
          * case on NT4. - We assume that we just need to write the lcn
          * change until someone tells us otherwise... (AIA)
          */
         if (likely(rl->lcn >= 0 || vol->major_ver < 3)) {
             /* Write change in lcn. */
             lcn_len = ntfs_write_significant_bytes(dst + 1 +
                     len_len, dst_max, rl->lcn - prev_lcn);
             if (unlikely(lcn_len < 0))
                 goto size_err;
             prev_lcn = rl->lcn;
         } else
             lcn_len = 0;
         dst_next = dst + len_len + lcn_len + 1;
         if (unlikely(dst_next > dst_max))
             goto size_err;
         /* Update header byte. */
         *dst = lcn_len << 4 | len_len;
         /* Position at next mapping pairs array element. */
         dst = dst_next;
     }
     /* Success. */
     err = 0;
 size_err:
     /* Set stop vcn. */
     if (stop_vcn)
         *stop_vcn = rl->vcn;
     /* Add terminator byte. */
     *dst = 0;
     return err;
 err_out:
     if (rl->lcn == LCN_RL_NOT_MAPPED)
         err = -EINVAL;
     else
         err = -EIO;
     return err;
 }
 
 /**
  * ntfs_rl_truncate_nolock - truncate a runlist starting at a specified vcn
  * @vol:    ntfs volume (needed for error output)
  * @runlist:    runlist to truncate
  * @new_length: the new length of the runlist in VCNs
  *
  * Truncate the runlist described by @runlist as well as the memory buffer
  * holding the runlist elements to a length of @new_length VCNs.
  *
  * If @new_length lies within the runlist, the runlist elements with VCNs of
  * @new_length and above are discarded.  As a special case if @new_length is
  * zero, the runlist is discarded and set to NULL.
  *
  * If @new_length lies beyond the runlist, a sparse runlist element is added to
  * the end of the runlist @runlist or if the last runlist element is a sparse
  * one already, this is extended.
  *
  * Note, no checking is done for unmapped runlist elements.  It is assumed that
  * the caller has mapped any elements that need to be mapped already.
  *
  * Return 0 on success and -errno on error.
  *
  * Locking: The caller must hold @runlist->lock for writing.
  */
 int ntfs_rl_truncate_nolock(const ntfs_volume *vol, runlist *const runlist,
         const s64 new_length)
 {
     runlist_element *rl;
     int old_size;
 
     ntfs_debug("Entering for new_length 0x%llx.", (long long)new_length);
     BUG_ON(!runlist);
     BUG_ON(new_length < 0);
     rl = runlist->rl;
     if (!new_length) {
         ntfs_debug("Freeing runlist.");
         runlist->rl = NULL;
         if (rl)
             ntfs_free(rl);
         return 0;
     }
     if (unlikely(!rl)) {
         /*
          * Create a runlist consisting of a sparse runlist element of
          * length @new_length followed by a terminator runlist element.
          */
         rl = ntfs_malloc_nofs(PAGE_SIZE);
         if (unlikely(!rl)) {
             ntfs_error(vol->sb, "Not enough memory to allocate "
                     "runlist element buffer.");
             return -ENOMEM;
         }
         runlist->rl = rl;
         rl[1].length = rl->vcn = 0;
         rl->lcn = LCN_HOLE;
         rl[1].vcn = rl->length = new_length;
         rl[1].lcn = LCN_ENOENT;
         return 0;
     }
     BUG_ON(new_length < rl->vcn);
     /* Find @new_length in the runlist. */
     while (likely(rl->length && new_length >= rl[1].vcn))
         rl++;
     /*
      * If not at the end of the runlist we need to shrink it.
      * If at the end of the runlist we need to expand it.
      */
     if (rl->length) {
         runlist_element *trl;
         bool is_end;
 
         ntfs_debug("Shrinking runlist.");
         /* Determine the runlist size. */
         trl = rl + 1;
         while (likely(trl->length))
             trl++;
         old_size = trl - runlist->rl + 1;
         /* Truncate the run. */
         rl->length = new_length - rl->vcn;
         /*
          * If a run was partially truncated, make the following runlist
          * element a terminator.
          */
         is_end = false;
         if (rl->length) {
             rl++;
             if (!rl->length)
                 is_end = true;
             rl->vcn = new_length;
             rl->length = 0;
         }
         rl->lcn = LCN_ENOENT;
         /* Reallocate memory if necessary. */
         if (!is_end) {
             int new_size = rl - runlist->rl + 1;
             rl = ntfs_rl_realloc(runlist->rl, old_size, new_size);
             if (IS_ERR(rl))
                 ntfs_warning(vol->sb, "Failed to shrink "
                         "runlist buffer.  This just "
                         "wastes a bit of memory "
                         "temporarily so we ignore it "
                         "and return success.");
             else
                 runlist->rl = rl;
         }
     } else if (likely(/* !rl->length && */ new_length > rl->vcn)) {
         ntfs_debug("Expanding runlist.");
         /*
          * If there is a previous runlist element and it is a sparse
          * one, extend it.  Otherwise need to add a new, sparse runlist
          * element.
          */
         if ((rl > runlist->rl) && ((rl - 1)->lcn == LCN_HOLE))
             (rl - 1)->length = new_length - (rl - 1)->vcn;
         else {
             /* Determine the runlist size. */
             old_size = rl - runlist->rl + 1;
             /* Reallocate memory if necessary. */
             rl = ntfs_rl_realloc(runlist->rl, old_size,
                     old_size + 1);
             if (IS_ERR(rl)) {
                 ntfs_error(vol->sb, "Failed to expand runlist "
                         "buffer, aborting.");
                 return PTR_ERR(rl);
             }
             runlist->rl = rl;
             /*
              * Set @rl to the same runlist element in the new
              * runlist as before in the old runlist.
              */
             rl += old_size - 1;
             /* Add a new, sparse runlist element. */
             rl->lcn = LCN_HOLE;
             rl->length = new_length - rl->vcn;
             /* Add a new terminator runlist element. */
             rl++;
             rl->length = 0;
         }
         rl->vcn = new_length;
         rl->lcn = LCN_ENOENT;
     } else /* if (unlikely(!rl->length && new_length == rl->vcn)) */ {
         /* Runlist already has same size as requested. */
         rl->lcn = LCN_ENOENT;
     }
     ntfs_debug("Done.");
     return 0;
 }
 
 /**
  * ntfs_rl_punch_nolock - punch a hole into a runlist
  * @vol:    ntfs volume (needed for error output)
  * @runlist:    runlist to punch a hole into
  * @start:  starting VCN of the hole to be created
  * @length: size of the hole to be created in units of clusters
  *
  * Punch a hole into the runlist @runlist starting at VCN @start and of size
  * @length clusters.
  *
  * Return 0 on success and -errno on error, in which case @runlist has not been
  * modified.
  *
  * If @start and/or @start + @length are outside the runlist return error code
  * -ENOENT.
  *
  * If the runlist contains unmapped or error elements between @start and @start
  * + @length return error code -EINVAL.
  *
  * Locking: The caller must hold @runlist->lock for writing.
  */
 int ntfs_rl_punch_nolock(const ntfs_volume *vol, runlist *const runlist,
         const VCN start, const s64 length)
 {
     const VCN end = start + length;
     s64 delta;
     runlist_element *rl, *rl_end, *rl_real_end, *trl;
     int old_size;
     bool lcn_fixup = false;
 
     ntfs_debug("Entering for start 0x%llx, length 0x%llx.",
             (long long)start, (long long)length);
     BUG_ON(!runlist);
     BUG_ON(start < 0);
     BUG_ON(length < 0);
     BUG_ON(end < 0);
     rl = runlist->rl;
     if (unlikely(!rl)) {
         if (likely(!start && !length))
             return 0;
         return -ENOENT;
     }
     /* Find @start in the runlist. */
     while (likely(rl->length && start >= rl[1].vcn))
         rl++;
     rl_end = rl;
     /* Find @end in the runlist. */
     while (likely(rl_end->length && end >= rl_end[1].vcn)) {
         /* Verify there are no unmapped or error elements. */
         if (unlikely(rl_end->lcn < LCN_HOLE))
             return -EINVAL;
         rl_end++;
     }
     /* Check the last element. */
     if (unlikely(rl_end->length && rl_end->lcn < LCN_HOLE))
         return -EINVAL;
     /* This covers @start being out of bounds, too. */
     if (!rl_end->length && end > rl_end->vcn)
         return -ENOENT;
     if (!length)
         return 0;
     if (!rl->length)
         return -ENOENT;
     rl_real_end = rl_end;
     /* Determine the runlist size. */
     while (likely(rl_real_end->length))
         rl_real_end++;
     old_size = rl_real_end - runlist->rl + 1;
     /* If @start is in a hole simply extend the hole. */
     if (rl->lcn == LCN_HOLE) {
         /*
          * If both @start and @end are in the same sparse run, we are
          * done.
          */
         if (end <= rl[1].vcn) {
             ntfs_debug("Done (requested hole is already sparse).");
             return 0;
         }
 extend_hole:
         /* Extend the hole. */
         rl->length = end - rl->vcn;
         /* If @end is in a hole, merge it with the current one. */
         if (rl_end->lcn == LCN_HOLE) {
             rl_end++;
             rl->length = rl_end->vcn - rl->vcn;
         }
         /* We have done the hole.  Now deal with the remaining tail. */
         rl++;
         /* Cut out all runlist elements up to @end. */
         if (rl < rl_end)
             memmove(rl, rl_end, (rl_real_end - rl_end + 1) *
                     sizeof(*rl));
         /* Adjust the beginning of the tail if necessary. */
         if (end > rl->vcn) {
             delta = end - rl->vcn;
             rl->vcn = end;
             rl->length -= delta;
             /* Only adjust the lcn if it is real. */
             if (rl->lcn >= 0)
                 rl->lcn += delta;
         }
 shrink_allocation:
         /* Reallocate memory if the allocation changed. */
         if (rl < rl_end) {
             rl = ntfs_rl_realloc(runlist->rl, old_size,
                     old_size - (rl_end - rl));
             if (IS_ERR(rl))
                 ntfs_warning(vol->sb, "Failed to shrink "
                         "runlist buffer.  This just "
                         "wastes a bit of memory "
                         "temporarily so we ignore it "
                         "and return success.");
             else
                 runlist->rl = rl;
         }
         ntfs_debug("Done (extend hole).");
         return 0;
     }
     /*
      * If @start is at the beginning of a run things are easier as there is
      * no need to split the first run.
      */
     if (start == rl->vcn) {
         /*
          * @start is at the beginning of a run.
          *
          * If the previous run is sparse, extend its hole.
          *
          * If @end is not in the same run, switch the run to be sparse
          * and extend the newly created hole.
          *
          * Thus both of these cases reduce the problem to the above
          * case of "@start is in a hole".
          */
         if (rl > runlist->rl && (rl - 1)->lcn == LCN_HOLE) {
             rl--;
             goto extend_hole;
         }
         if (end >= rl[1].vcn) {
             rl->lcn = LCN_HOLE;
             goto extend_hole;
         }
         /*
          * The final case is when @end is in the same run as @start.
          * For this need to split the run into two.  One run for the
          * sparse region between the beginning of the old run, i.e.
          * @start, and @end and one for the remaining non-sparse
          * region, i.e. between @end and the end of the old run.
          */
         trl = ntfs_rl_realloc(runlist->rl, old_size, old_size + 1);
         if (IS_ERR(trl))
             goto enomem_out;
         old_size++;
         if (runlist->rl != trl) {
             rl = trl + (rl - runlist->rl);
             rl_end = trl + (rl_end - runlist->rl);
             rl_real_end = trl + (rl_real_end - runlist->rl);
             runlist->rl = trl;
         }
 split_end:
         /* Shift all the runs up by one. */
         memmove(rl + 1, rl, (rl_real_end - rl + 1) * sizeof(*rl));
         /* Finally, setup the two split runs. */
         rl->lcn = LCN_HOLE;
         rl->length = length;
         rl++;
         rl->vcn += length;
         /* Only adjust the lcn if it is real. */
         if (rl->lcn >= 0 || lcn_fixup)
             rl->lcn += length;
         rl->length -= length;
         ntfs_debug("Done (split one).");
         return 0;
     }
     /*
      * @start is neither in a hole nor at the beginning of a run.
      *
      * If @end is in a hole, things are easier as simply truncating the run
      * @start is in to end at @start - 1, deleting all runs after that up
      * to @end, and finally extending the beginning of the run @end is in
      * to be @start is all that is needed.
      */
     if (rl_end->lcn == LCN_HOLE) {
         /* Truncate the run containing @start. */
         rl->length = start - rl->vcn;
         rl++;
         /* Cut out all runlist elements up to @end. */
         if (rl < rl_end)
             memmove(rl, rl_end, (rl_real_end - rl_end + 1) *
                     sizeof(*rl));
         /* Extend the beginning of the run @end is in to be @start. */
         rl->vcn = start;
         rl->length = rl[1].vcn - start;
         goto shrink_allocation;
     }
     /* 
      * If @end is not in a hole there are still two cases to distinguish.
      * Either @end is or is not in the same run as @start.
      *
      * The second case is easier as it can be reduced to an already solved
      * problem by truncating the run @start is in to end at @start - 1.
      * Then, if @end is in the next run need to split the run into a sparse
      * run followed by a non-sparse run (already covered above) and if @end
      * is not in the next run switching it to be sparse, again reduces the
      * problem to the already covered case of "@start is in a hole".
      */
     if (end >= rl[1].vcn) {
         /*
          * If @end is not in the next run, reduce the problem to the
          * case of "@start is in a hole".
          */
         if (rl[1].length && end >= rl[2].vcn) {
             /* Truncate the run containing @start. */
             rl->length = start - rl->vcn;
             rl++;
             rl->vcn = start;
             rl->lcn = LCN_HOLE;
             goto extend_hole;
         }
         trl = ntfs_rl_realloc(runlist->rl, old_size, old_size + 1);
         if (IS_ERR(trl))
             goto enomem_out;
         old_size++;
         if (runlist->rl != trl) {
             rl = trl + (rl - runlist->rl);
             rl_end = trl + (rl_end - runlist->rl);
             rl_real_end = trl + (rl_real_end - runlist->rl);
             runlist->rl = trl;
         }
         /* Truncate the run containing @start. */
         rl->length = start - rl->vcn;
         rl++;
         /*
          * @end is in the next run, reduce the problem to the case
          * where "@start is at the beginning of a run and @end is in
          * the same run as @start".
          */
         delta = rl->vcn - start;
         rl->vcn = start;
         if (rl->lcn >= 0) {
             rl->lcn -= delta;
             /* Need this in case the lcn just became negative. */
             lcn_fixup = true;
         }
         rl->length += delta;
         goto split_end;
     }
     /*
      * The first case from above, i.e. @end is in the same run as @start.
      * We need to split the run into three.  One run for the non-sparse
      * region between the beginning of the old run and @start, one for the
      * sparse region between @start and @end, and one for the remaining
      * non-sparse region, i.e. between @end and the end of the old run.
      */
     trl = ntfs_rl_realloc(runlist->rl, old_size, old_size + 2);
     if (IS_ERR(trl))
         goto enomem_out;
     old_size += 2;
     if (runlist->rl != trl) {
         rl = trl + (rl - runlist->rl);
         rl_end = trl + (rl_end - runlist->rl);
         rl_real_end = trl + (rl_real_end - runlist->rl);
         runlist->rl = trl;
     }
     /* Shift all the runs up by two. */
     memmove(rl + 2, rl, (rl_real_end - rl + 1) * sizeof(*rl));
     /* Finally, setup the three split runs. */
     rl->length = start - rl->vcn;
     rl++;
     rl->vcn = start;
     rl->lcn = LCN_HOLE;
     rl->length = length;
     rl++;
     delta = end - rl->vcn;
     rl->vcn = end;
     rl->lcn += delta;
     rl->length -= delta;
     ntfs_debug("Done (split both).");
     return 0;
 enomem_out:
     ntfs_error(vol->sb, "Not enough memory to extend runlist buffer.");
     return -ENOMEM;
 }
 
 #endif /* NTFS_RW */

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