// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * NTFS runlist handling code.
 *
 * Copyright (c) 2001-2007 Anton Altaparmakov
 * Copyright (c) 2002-2005 Richard Russon
 * Copyright (c) 2025 LG Electronics Co., Ltd.
 *
 * Part of this file is based on code from the NTFS-3G.
 * and is copyrighted by the respective authors below:
 * Copyright (c) 2002-2005 Anton Altaparmakov
 * Copyright (c) 2002-2005 Richard Russon
 * Copyright (c) 2002-2008 Szabolcs Szakacsits
 * Copyright (c) 2004 Yura Pakhuchiy
 * Copyright (c) 2007-2022 Jean-Pierre Andre
 */

#include <linux/overflow.h>

#include "ntfs.h"
#include "attrib.h"

/*
 * ntfs_rl_mm - runlist memmove
 * @base: base runlist array
 * @dst: destination index in @base
 * @src: source index in @base
 * @size: number of elements to move
 *
 * It is up to the caller to serialize access to the runlist @base.
 */
static inline void ntfs_rl_mm(struct 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
 * @dstbase: destination runlist array
 * @dst: destination index in @dstbase
 * @srcbase: source runlist array
 * @src: source index in @srcbase
 * @size: number of elements to copy
 *
 * It is up to the caller to serialize access to the runlists @dstbase and
 * @srcbase.
 */
static inline void ntfs_rl_mc(struct runlist_element *dstbase, int dst,
                struct 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.
 */
struct runlist_element *ntfs_rl_realloc(struct runlist_element *rl,
                int old_size, int new_size)
{
        struct runlist_element *new_rl;

        old_size = old_size * sizeof(*rl);
        new_size = new_size * sizeof(*rl);
        if (old_size == new_size)
                return rl;

        new_rl = kvzalloc(new_size, GFP_NOFS);
        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);
                kvfree(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.
 */
static inline struct runlist_element *ntfs_rl_realloc_nofail(struct runlist_element *rl,
                int old_size, int new_size)
{
        struct runlist_element *new_rl;

        old_size = old_size * sizeof(*rl);
        new_size = new_size * sizeof(*rl);
        if (old_size == new_size)
                return rl;

        new_rl = kvmalloc(new_size, GFP_NOFS | __GFP_NOFAIL);
        if (likely(rl != NULL)) {
                if (unlikely(old_size > new_size))
                        old_size = new_size;
                memcpy(new_rl, rl, old_size);
                kvfree(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(struct runlist_element *dst,
                struct runlist_element *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;
        /* If we are merging two dealloc, we can merge them. */
        if ((dst->lcn == LCN_DELALLOC) && (src->lcn == LCN_DELALLOC))
                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(struct runlist_element *dst, struct runlist_element *src)
{
        dst->length += src->length;
}

/*
 * ntfs_rl_append - append a runlist after a given element
 * @dst: destination runlist to append to
 * @dsize: number of elements in @dst
 * @src: source runlist to append from
 * @ssize: number of elements in @src
 * @loc: index in @dst after which to append @src
 * @new_size: on success, set to the new combined size
 *
 * 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.
 */
static inline struct runlist_element *ntfs_rl_append(struct runlist_element *dst,
                int dsize, struct runlist_element *src, int ssize, int loc,
                size_t *new_size)
{
        bool right = false;     /* Right end of @src needs merging. */
        int marker;             /* End of the inserted runs. */

        /* 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;

        *new_size = dsize + ssize - right;
        /*
         * 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: destination runlist to insert into
 * @dsize: number of elements in @dst
 * @src: source runlist to insert from
 * @ssize: number of elements in @src
 * @loc: index in @dst at which to insert @src
 * @new_size: on success, set to the new combined size
 *
 * 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.
 */
static inline struct runlist_element *ntfs_rl_insert(struct runlist_element *dst,
                int dsize, struct runlist_element *src, int ssize, int loc,
                size_t *new_size)
{
        bool left = false;      /* Left end of @src needs merging. */
        bool disc = false;      /* Discontinuity between @dst and @src. */
        int marker;             /* End of the inserted runs. */

        /*
         * 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;

        *new_size = dsize + ssize - left + disc;
        /*
         * 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].lcn == LCN_DELALLOC)
                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: destination runlist to replace in
 * @dsize: number of elements in @dst
 * @src: source runlist to replace with
 * @ssize: number of elements in @src
 * @loc: index in @dst to replace
 * @new_size: on success, set to the new combined size
 *
 * 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.
 */
static inline struct runlist_element *ntfs_rl_replace(struct runlist_element *dst,
                int dsize, struct runlist_element *src, int ssize, int loc,
                size_t *new_size)
{
        int 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. */

        /* 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;
        }

        *new_size = dsize + delta;
        /*
         * 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: destination runlist with a hole
 * @dsize: number of elements in @dst
 * @src: source runlist to insert
 * @ssize: number of elements in @src
 * @loc: index in @dst of the hole to split
 * @new_size: on success, set to the new combined size
 *
 * 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.
 */
static inline struct runlist_element *ntfs_rl_split(struct runlist_element *dst, int dsize,
                struct runlist_element *src, int ssize, int loc,
                size_t *new_size)
{
        /* Space required: @dst size + @src size + one new hole. */
        dst = ntfs_rl_realloc(dst, dsize, dsize + ssize + 1);
        if (IS_ERR(dst))
                return dst;

        *new_size = dsize + ssize + 1;
        /*
         * 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
 * @d_runlist: destination runlist structure to merge into
 * @srl: source runlist to merge from
 * @s_rl_count: number of elements in @srl (0 to auto-detect)
 * @new_rl_count: on success, set to the new combined runlist size
 *
 * 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.
 */
struct runlist_element *ntfs_runlists_merge(struct runlist *d_runlist,
                                     struct runlist_element *srl, size_t s_rl_count,
                                     size_t *new_rl_count)
{
        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;
        s64 marker_vcn = 0;
        struct runlist_element *drl = d_runlist->rl, *rl;

#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);

        if (s_rl_count == 0) {
                for (; srl[s_rl_count].length; s_rl_count++)
                        ;
                s_rl_count++;
        }

        /* 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. */
                        drl = ntfs_rl_realloc(drl, s_rl_count, s_rl_count + 1);
                        if (IS_ERR(drl))
                                return drl;
                        /* Insert start element at the front of the runlist. */
                        ntfs_rl_mm(drl, 1, 0, s_rl_count);
                        drl[0].vcn = 0;
                        drl[0].lcn = LCN_RL_NOT_MAPPED;
                        drl[0].length = drl[1].vcn;
                        s_rl_count++;
                }

                *new_rl_count = s_rl_count;
                goto finished;
        }

        if (d_runlist->count < 1 || s_rl_count < 2)
                return ERR_PTR(-EINVAL);

        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. */
        WARN_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.
         */
        rl = __ntfs_attr_find_vcn_nolock(d_runlist, srl[sstart].vcn);
        if (IS_ERR(rl))
                di = (int)d_runlist->count - 1;
        else
                di = (int)(rl - d_runlist->rl);
        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. */
        send = (int)s_rl_count - 1;
        dend = (int)d_runlist->count - 1;

        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 (start) {
                if (finish)
                        drl = ntfs_rl_replace(drl, ds, srl + sstart, ss, dins, new_rl_count);
                else
                        drl = ntfs_rl_insert(drl, ds, srl + sstart, ss, dins, new_rl_count);
        } else {
                if (finish)
                        drl = ntfs_rl_append(drl, ds, srl + sstart, ss, dins, new_rl_count);
                else
                        drl = ntfs_rl_split(drl, ds, srl + sstart, ss, dins, new_rl_count);
        }
        if (IS_ERR(drl)) {
                ntfs_error(NULL, "Merge failed.");
                return drl;
        }
        kvfree(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.",
                                                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;
                                        *new_rl_count += 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);
                                *new_rl_count += 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
 * @attr: attribute record whose mapping pairs to decompress
 * @old_runlist: optional runlist to merge the decompressed runlist into
 * @new_rl_count: on success, set to the new runlist size
 *
 * 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.
 */
struct runlist_element *ntfs_mapping_pairs_decompress(const struct ntfs_volume *vol,
                const struct attr_record *attr, struct runlist *old_runlist,
                size_t *new_rl_count)
{
        s64 vcn;                /* Current vcn. */
        s64 lcn;                /* Current lcn. */
        s64 deltaxcn;           /* Change in [vl]cn. */
        struct runlist_element *rl, *new_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 struct runlist_elements. */
        u8 b;                   /* Current byte offset in buf. */
        u64 lowest_vcn;         /* Raw on-disk lowest_vcn. */

#ifdef DEBUG
        /* Make sure attr exists and is non-resident. */
        if (!attr || !attr->non_resident) {
                ntfs_error(vol->sb, "Invalid arguments.");
                return ERR_PTR(-EINVAL);
        }
#endif
        lowest_vcn = le64_to_cpu(attr->data.non_resident.lowest_vcn);
        /* Validate lowest_vcn from on-disk metadata to ensure it is sane. */
        if (overflows_type(lowest_vcn, vcn)) {
                ntfs_error(vol->sb, "Invalid lowest_vcn in mapping pairs.");
                return ERR_PTR(-EIO);
        }
        /* Start at vcn = lowest_vcn and lcn 0. */
        vcn = 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);
        }

        /* Current position in runlist array. */
        rlpos = 0;
        /* Allocate first page and set current runlist size to one page. */
        rl = kvzalloc(rlsize = PAGE_SIZE, GFP_NOFS);
        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. kvzalloc()
                 * operates on whole pages only.
                 */
                if (((rlpos + 3) * sizeof(*rl)) > rlsize) {
                        struct runlist_element *rl2;

                        rl2 = kvzalloc(rlsize + PAGE_SIZE, GFP_NOFS);
                        if (unlikely(!rl2)) {
                                kvfree(rl);
                                return ERR_PTR(-ENOMEM);
                        }
                        memcpy(rl2, rl, rlsize);
                        kvfree(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.
                 * Guard against s64 overflow from a crafted mapping
                 * pairs array to preserve the monotonically-increasing
                 * vcn invariant.
                 */
                if (unlikely(check_add_overflow(vcn, deltaxcn, &vcn))) {
                        ntfs_error(vol->sb, "VCN overflow in mapping pairs array.");
                        goto err_out;
                }

                /*
                 * 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. */
                        if (unlikely(check_add_overflow(lcn, deltaxcn, &lcn))) {
                                ntfs_error(vol->sb,
                                                "LCN overflow in mapping pairs array.");
                                goto err_out;
                        }
#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 == -1))
                                        ntfs_error(vol->sb, "lcn delta == -1");
                                if (unlikely(lcn == -1))
                                        ntfs_error(vol->sb, "lcn == -1");
                        }
#endif
                        /* Check lcn is not below -1. */
                        if (unlikely(lcn < -1)) {
                                ntfs_error(vol->sb, "Invalid s64 < -1 in mapping pairs array.");
                                goto err_out;
                        }

                        /* chkdsk accepts zero-sized runs only for holes */
                        if ((lcn != -1) && !rl[rlpos].length) {
                                ntfs_error(vol->sb,
                                           "Invalid zero-sized data run(lcn : %lld).\n",
                                           lcn);
                                goto err_out;
                        }

                        /* Enter the current lcn into the runlist element. */
                        rl[rlpos].lcn = lcn;
                }
                /* Get to the next runlist element, skipping zero-sized holes */
                if (rl[rlpos].length)
                        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 = le64_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) {
                s64 max_cluster;

                max_cluster = ((le64_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",
                                                deltaxcn, 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",
                                           deltaxcn, 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_runlist || !old_runlist->rl) {
                *new_rl_count = rlpos + 1;
                ntfs_debug("Mapping pairs array successfully decompressed:");
                ntfs_debug_dump_runlist(rl);
                return rl;
        }
        /* Now combine the new and old runlists checking for overlaps. */
        new_rl = ntfs_runlists_merge(old_runlist, rl, rlpos + 1, new_rl_count);
        if (!IS_ERR(new_rl))
                return new_rl;
        kvfree(rl);
        ntfs_error(vol->sb, "Failed to merge runlists.");
        return new_rl;
io_error:
        ntfs_error(vol->sb, "Corrupt attribute.");
err_out:
        kvfree(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.
 */
s64 ntfs_rl_vcn_to_lcn(const struct runlist_element *rl, const s64 vcn)
{
        int i;

        /*
         * 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 (vcn < rl[i+1].vcn) {
                        if (likely(rl[i].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 < 0))
                return rl[i].lcn;
        /* Just in case... We could replace this with BUG() some day. */
        return LCN_ENOENT;
}

/*
 * 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.
 */
struct runlist_element *ntfs_rl_find_vcn_nolock(struct runlist_element *rl, const s64 vcn)
{
        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
 * @rl: runlist to calculate the mapping pairs array size for
 * @first_vcn: first vcn which to include in the mapping pairs array
 * @last_vcn: last vcn which to include in the mapping pairs array
 * @max_mp_size: maximum size to return (0 or less means unlimited)
 *
 * 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.
 */
int ntfs_get_size_for_mapping_pairs(const struct ntfs_volume *vol,
                const struct runlist_element *rl, const s64 first_vcn,
                const s64 last_vcn, int max_mp_size)
{
        s64 prev_lcn;
        int rls;
        bool the_end = false;

        if (first_vcn < 0 || last_vcn < -1)
                return -EINVAL;

        if (last_vcn >= 0 && first_vcn > last_vcn)
                return -EINVAL;

        if (!rl) {
                WARN_ON(first_vcn);
                WARN_ON(last_vcn > 0);
                return 1;
        }
        if (max_mp_size <= 0)
                max_mp_size = INT_MAX;
        /* 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;
                }

                if (rls > max_mp_size)
                        break;
        }
        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
 * @dst: destination buffer to build mapping pairs array into
 * @dst_len: size of @dst in bytes
 * @rl: runlist to build the mapping pairs array from
 * @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: on return, set to the first vcn outside the destination buffer
 * @stop_rl: on return, set to the runlist element where encoding stopped
 * @de_cluster_count: on return, set to the number of clusters encoded
 *
 * 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 struct ntfs_volume *vol, s8 *dst,
                const int dst_len, const struct runlist_element *rl,
                const s64 first_vcn, const s64 last_vcn, s64 *const stop_vcn,
                struct runlist_element **stop_rl, unsigned int *de_cluster_count)
{
        s64 prev_lcn;
        s8 *dst_max, *dst_next;
        int err = -ENOSPC;
        bool the_end = false;
        s8 len_len, lcn_len;
        unsigned int de_cnt = 0;

        if (first_vcn < 0 || last_vcn < -1 || dst_len < 1)
                return -EINVAL;
        if (last_vcn >= 0 && first_vcn > last_vcn)
                return -EINVAL;

        if (!rl) {
                WARN_ON(first_vcn || 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.
                 */
                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.
                 */
                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 {
                        if (rl->lcn == LCN_DELALLOC)
                                de_cnt += rl->length;
                        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. */
        if (de_cluster_count)
                *de_cluster_count = de_cnt;
        err = 0;
size_err:
        /* Set stop vcn. */
        if (stop_vcn)
                *stop_vcn = rl->vcn;
        if (stop_rl)
                *stop_rl = (struct runlist_element *)rl;
        /* 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 struct ntfs_volume *vol, struct runlist *const runlist,
                const s64 new_length)
{
        struct runlist_element *rl;
        int old_size;

        ntfs_debug("Entering for new_length 0x%llx.", (long long)new_length);

        if (!runlist || new_length < 0)
                return -EINVAL;

        rl = runlist->rl;
        if (new_length < rl->vcn)
                return -EINVAL;

        /* 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) {
                struct 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;
                runlist->count = rl - runlist->rl + 1;
                /* 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;
                        runlist->count = old_size + 1;
                }
                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_sparse - check whether runlist have sparse regions or not.
 * @rl:         runlist to check
 *
 * Return 1 if have, 0 if not, -errno on error.
 */
int ntfs_rl_sparse(struct runlist_element *rl)
{
        struct runlist_element *rlc;

        if (!rl)
                return -EINVAL;

        for (rlc = rl; rlc->length; rlc++)
                if (rlc->lcn < 0) {
                        if (rlc->lcn != LCN_HOLE && rlc->lcn != LCN_DELALLOC) {
                                pr_err("%s: bad runlist\n", __func__);
                                return -EINVAL;
                        }
                        return 1;
                }
        return 0;
}

/*
 * ntfs_rl_get_compressed_size - calculate length of non sparse regions
 * @vol:        ntfs volume (need for cluster size)
 * @rl:         runlist to calculate for
 *
 * Return compressed size or -errno on error.
 */
s64 ntfs_rl_get_compressed_size(struct ntfs_volume *vol, struct runlist_element *rl)
{
        struct runlist_element *rlc;
        s64 ret = 0;

        if (!rl)
                return -EINVAL;

        for (rlc = rl; rlc->length; rlc++) {
                if (rlc->lcn < 0) {
                        if (rlc->lcn != LCN_HOLE && rlc->lcn != LCN_DELALLOC) {
                                ntfs_error(vol->sb, "%s: bad runlist, rlc->lcn : %lld",
                                                __func__, rlc->lcn);
                                return -EINVAL;
                        }
                } else
                        ret += rlc->length;
        }
        return NTFS_CLU_TO_B(vol, ret);
}

static inline bool ntfs_rle_lcn_contiguous(struct runlist_element *left_rle,
                                           struct runlist_element *right_rle)
{
        if (left_rle->lcn > LCN_HOLE &&
            left_rle->lcn + left_rle->length == right_rle->lcn)
                return true;
        else if (left_rle->lcn == LCN_HOLE && right_rle->lcn == LCN_HOLE)
                return true;
        else
                return false;
}

static inline bool ntfs_rle_contain(struct runlist_element *rle, s64 vcn)
{
        if (rle->length > 0 &&
            vcn >= rle->vcn && vcn < rle->vcn + rle->length)
                return true;
        else
                return false;
}

struct runlist_element *ntfs_rl_insert_range(struct runlist_element *dst_rl, int dst_cnt,
                                      struct runlist_element *src_rl, int src_cnt,
                                      size_t *new_rl_cnt)
{
        struct runlist_element *i_rl, *new_rl, *src_rl_origin = src_rl;
        struct runlist_element dst_rl_split;
        s64 start_vcn;
        int new_1st_cnt, new_2nd_cnt, new_3rd_cnt, new_cnt;

        if (!dst_rl || !src_rl || !new_rl_cnt)
                return ERR_PTR(-EINVAL);
        if (dst_cnt <= 0 || src_cnt <= 0)
                return ERR_PTR(-EINVAL);
        if (!(dst_rl[dst_cnt - 1].lcn == LCN_ENOENT &&
              dst_rl[dst_cnt - 1].length == 0) ||
            src_rl[src_cnt - 1].lcn < LCN_HOLE)
                return ERR_PTR(-EINVAL);

        start_vcn = src_rl[0].vcn;

        i_rl = ntfs_rl_find_vcn_nolock(dst_rl, start_vcn);
        if (!i_rl ||
            (i_rl->lcn == LCN_ENOENT && i_rl->vcn != start_vcn) ||
            (i_rl->lcn != LCN_ENOENT && !ntfs_rle_contain(i_rl, start_vcn)))
                return ERR_PTR(-EINVAL);

        new_1st_cnt = (int)(i_rl - dst_rl);
        if (new_1st_cnt > dst_cnt)
                return ERR_PTR(-EINVAL);
        new_3rd_cnt = dst_cnt - new_1st_cnt;
        if (new_3rd_cnt < 1)
                return ERR_PTR(-EINVAL);

        if (i_rl[0].vcn != start_vcn) {
                if (i_rl[0].lcn == LCN_HOLE && src_rl[0].lcn == LCN_HOLE)
                        goto merge_src_rle;

                /* split @i_rl[0] and create @dst_rl_split */
                dst_rl_split.vcn = i_rl[0].vcn;
                dst_rl_split.length = start_vcn - i_rl[0].vcn;
                dst_rl_split.lcn = i_rl[0].lcn;

                i_rl[0].vcn = start_vcn;
                i_rl[0].length -= dst_rl_split.length;
                i_rl[0].lcn += dst_rl_split.length;
        } else {
                struct runlist_element *dst_rle, *src_rle;
merge_src_rle:

                /* not split @i_rl[0] */
                dst_rl_split.lcn = LCN_ENOENT;

                /* merge @src_rl's first run and @i_rl[0]'s left run if possible */
                dst_rle = &dst_rl[new_1st_cnt - 1];
                src_rle = &src_rl[0];
                if (new_1st_cnt > 0 && ntfs_rle_lcn_contiguous(dst_rle, src_rle)) {
                        WARN_ON(dst_rle->vcn + dst_rle->length != src_rle->vcn);
                        dst_rle->length += src_rle->length;
                        src_rl++;
                        src_cnt--;
                } else {
                        /* merge @src_rl's last run and @i_rl[0]'s right if possible */
                        dst_rle = &dst_rl[new_1st_cnt];
                        src_rle = &src_rl[src_cnt - 1];

                        if (ntfs_rle_lcn_contiguous(dst_rle, src_rle)) {
                                dst_rle->length += src_rle->length;
                                src_cnt--;
                        }
                }
        }

        new_2nd_cnt = src_cnt;
        new_cnt = new_1st_cnt + new_2nd_cnt + new_3rd_cnt;
        new_cnt += dst_rl_split.lcn >= LCN_HOLE ? 1 : 0;
        new_rl = kvcalloc(new_cnt, sizeof(*new_rl), GFP_NOFS);
        if (!new_rl)
                return ERR_PTR(-ENOMEM);

        /* Copy the @dst_rl's first half to @new_rl */
        ntfs_rl_mc(new_rl, 0, dst_rl, 0, new_1st_cnt);
        if (dst_rl_split.lcn >= LCN_HOLE) {
                ntfs_rl_mc(new_rl, new_1st_cnt, &dst_rl_split, 0, 1);
                new_1st_cnt++;
        }
        /* Copy the @src_rl to @new_rl */
        ntfs_rl_mc(new_rl, new_1st_cnt, src_rl, 0, new_2nd_cnt);
        /* Copy the @dst_rl's second half to @new_rl */
        if (new_3rd_cnt >= 1) {
                struct runlist_element *rl, *rl_3rd;
                int dst_1st_cnt = dst_rl_split.lcn >= LCN_HOLE ?
                        new_1st_cnt - 1 : new_1st_cnt;

                ntfs_rl_mc(new_rl, new_1st_cnt + new_2nd_cnt,
                           dst_rl, dst_1st_cnt, new_3rd_cnt);
                /* Update vcn of the @dst_rl's second half runs to reflect
                 * appended @src_rl.
                 */
                if (new_1st_cnt + new_2nd_cnt == 0) {
                        rl_3rd = &new_rl[new_1st_cnt + new_2nd_cnt + 1];
                        rl = &new_rl[new_1st_cnt + new_2nd_cnt];
                } else {
                        rl_3rd = &new_rl[new_1st_cnt + new_2nd_cnt];
                        rl = &new_rl[new_1st_cnt + new_2nd_cnt - 1];
                }
                do {
                        rl_3rd->vcn = rl->vcn + rl->length;
                        if (rl_3rd->length <= 0)
                                break;
                        rl = rl_3rd;
                        rl_3rd++;
                } while (1);
        }
        *new_rl_cnt = new_1st_cnt + new_2nd_cnt + new_3rd_cnt;

        kvfree(dst_rl);
        kvfree(src_rl_origin);
        return new_rl;
}

struct runlist_element *ntfs_rl_punch_hole(struct runlist_element *dst_rl, int dst_cnt,
                                    s64 start_vcn, s64 len,
                                    struct runlist_element **punch_rl,
                                    size_t *new_rl_cnt)
{
        struct runlist_element *s_rl, *e_rl, *new_rl, *dst_3rd_rl, hole_rl[1];
        s64 end_vcn;
        int new_1st_cnt, dst_3rd_cnt, new_cnt, punch_cnt, merge_cnt;
        bool begin_split, end_split, one_split_3;

        if (dst_cnt < 2 ||
            !(dst_rl[dst_cnt - 1].lcn == LCN_ENOENT &&
              dst_rl[dst_cnt - 1].length == 0))
                return ERR_PTR(-EINVAL);

        end_vcn = min(start_vcn + len - 1,
                      dst_rl[dst_cnt - 2].vcn + dst_rl[dst_cnt - 2].length - 1);

        s_rl = ntfs_rl_find_vcn_nolock(dst_rl, start_vcn);
        if (!s_rl ||
            s_rl->lcn <= LCN_ENOENT ||
            !ntfs_rle_contain(s_rl, start_vcn))
                return ERR_PTR(-EINVAL);

        begin_split = s_rl->vcn != start_vcn;

        e_rl = ntfs_rl_find_vcn_nolock(dst_rl, end_vcn);
        if (!e_rl ||
            e_rl->lcn <= LCN_ENOENT ||
            !ntfs_rle_contain(e_rl, end_vcn))
                return ERR_PTR(-EINVAL);

        end_split = e_rl->vcn + e_rl->length - 1 != end_vcn;

        /* @s_rl has to be split into left, punched hole, and right */
        one_split_3 = e_rl == s_rl && begin_split && end_split;

        punch_cnt = (int)(e_rl - s_rl) + 1;

        *punch_rl = kvcalloc(punch_cnt + 1, sizeof(struct runlist_element),
                        GFP_NOFS);
        if (!*punch_rl)
                return ERR_PTR(-ENOMEM);

        new_cnt = dst_cnt - (int)(e_rl - s_rl + 1) + 3;
        new_rl = kvcalloc(new_cnt, sizeof(struct runlist_element), GFP_NOFS);
        if (!new_rl) {
                kvfree(*punch_rl);
                *punch_rl = NULL;
                return ERR_PTR(-ENOMEM);
        }

        new_1st_cnt = (int)(s_rl - dst_rl) + 1;
        ntfs_rl_mc(*punch_rl, 0, dst_rl, new_1st_cnt - 1, punch_cnt);

        (*punch_rl)[punch_cnt].lcn = LCN_ENOENT;
        (*punch_rl)[punch_cnt].length = 0;

        if (!begin_split)
                new_1st_cnt--;
        dst_3rd_rl = e_rl;
        dst_3rd_cnt = (int)(&dst_rl[dst_cnt - 1] - e_rl) + 1;
        if (!end_split) {
                dst_3rd_rl++;
                dst_3rd_cnt--;
        }

        /* Copy the 1st part of @dst_rl into @new_rl */
        ntfs_rl_mc(new_rl, 0, dst_rl, 0, new_1st_cnt);
        if (begin_split) {
                /* the @e_rl has to be splited and copied into the last of @new_rl
                 * and the first of @punch_rl
                 */
                s64 first_cnt = start_vcn - dst_rl[new_1st_cnt - 1].vcn;

                if (new_1st_cnt)
                        new_rl[new_1st_cnt - 1].length = first_cnt;

                (*punch_rl)[0].vcn = start_vcn;
                (*punch_rl)[0].length -= first_cnt;
                if ((*punch_rl)[0].lcn > LCN_HOLE)
                        (*punch_rl)[0].lcn += first_cnt;
        }

        /* Copy a hole into @new_rl */
        hole_rl[0].vcn = start_vcn;
        hole_rl[0].length = (s64)len;
        hole_rl[0].lcn = LCN_HOLE;
        ntfs_rl_mc(new_rl, new_1st_cnt, hole_rl, 0, 1);

        /* Copy the 3rd part of @dst_rl into @new_rl */
        ntfs_rl_mc(new_rl, new_1st_cnt + 1, dst_3rd_rl, 0, dst_3rd_cnt);
        if (end_split) {
                /* the @e_rl has to be splited and copied into the first of
                 * @new_rl and the last of @punch_rl
                 */
                s64 first_cnt = end_vcn - dst_3rd_rl[0].vcn + 1;

                new_rl[new_1st_cnt + 1].vcn = end_vcn + 1;
                new_rl[new_1st_cnt + 1].length -= first_cnt;
                if (new_rl[new_1st_cnt + 1].lcn > LCN_HOLE)
                        new_rl[new_1st_cnt + 1].lcn += first_cnt;

                if (one_split_3)
                        (*punch_rl)[punch_cnt - 1].length -=
                                new_rl[new_1st_cnt + 1].length;
                else
                        (*punch_rl)[punch_cnt - 1].length = first_cnt;
        }

        /* Merge left and hole, or hole and right in @new_rl, if left or right
         * consists of holes.
         */
        merge_cnt = 0;
        if (new_1st_cnt > 0 && new_rl[new_1st_cnt - 1].lcn == LCN_HOLE) {
                /* Merge right and hole */
                s_rl =  &new_rl[new_1st_cnt - 1];
                s_rl->length += s_rl[1].length;
                merge_cnt = 1;
                /* Merge left and right */
                if (new_1st_cnt + 1 < new_cnt &&
                    new_rl[new_1st_cnt + 1].lcn == LCN_HOLE) {
                        s_rl->length += s_rl[2].length;
                        merge_cnt++;
                }
        } else if (new_1st_cnt + 1 < new_cnt &&
                   new_rl[new_1st_cnt + 1].lcn == LCN_HOLE) {
                /* Merge left and hole */
                s_rl = &new_rl[new_1st_cnt];
                s_rl->length += s_rl[1].length;
                merge_cnt = 1;
        }
        if (merge_cnt) {
                struct runlist_element *d_rl, *src_rl;

                d_rl = s_rl + 1;
                src_rl = s_rl + 1 + merge_cnt;
                ntfs_rl_mm(new_rl, (int)(d_rl - new_rl), (int)(src_rl - new_rl),
                           (int)(&new_rl[new_cnt - 1] - src_rl) + 1);
        }

        (*punch_rl)[punch_cnt].vcn = (*punch_rl)[punch_cnt - 1].vcn +
                (*punch_rl)[punch_cnt - 1].length;

        /* punch_cnt elements of dst are replaced with one hole */
        *new_rl_cnt = dst_cnt - (punch_cnt - (int)begin_split - (int)end_split) +
                1 - merge_cnt;
        kvfree(dst_rl);
        return new_rl;
}

struct runlist_element *ntfs_rl_collapse_range(struct runlist_element *dst_rl, int dst_cnt,
                                        s64 start_vcn, s64 len,
                                        struct runlist_element **punch_rl,
                                        size_t *new_rl_cnt)
{
        struct runlist_element *s_rl, *e_rl, *new_rl, *dst_3rd_rl;
        s64 end_vcn;
        int new_1st_cnt, dst_3rd_cnt, new_cnt, punch_cnt, merge_cnt, i;
        bool begin_split, end_split, one_split_3;

        if (dst_cnt < 2 ||
            !(dst_rl[dst_cnt - 1].lcn == LCN_ENOENT &&
              dst_rl[dst_cnt - 1].length == 0))
                return ERR_PTR(-EINVAL);

        end_vcn = min(start_vcn + len - 1,
                        dst_rl[dst_cnt - 1].vcn - 1);

        s_rl = ntfs_rl_find_vcn_nolock(dst_rl, start_vcn);
        if (!s_rl ||
            s_rl->lcn <= LCN_ENOENT ||
            !ntfs_rle_contain(s_rl, start_vcn))
                return ERR_PTR(-EINVAL);

        begin_split = s_rl->vcn != start_vcn;

        e_rl = ntfs_rl_find_vcn_nolock(dst_rl, end_vcn);
        if (!e_rl ||
            e_rl->lcn <= LCN_ENOENT ||
            !ntfs_rle_contain(e_rl, end_vcn))
                return ERR_PTR(-EINVAL);

        end_split = e_rl->vcn + e_rl->length - 1 != end_vcn;

        /* @s_rl has to be split into left, collapsed, and right */
        one_split_3 = e_rl == s_rl && begin_split && end_split;

        punch_cnt = (int)(e_rl - s_rl) + 1;
        *punch_rl = kvcalloc(punch_cnt + 1, sizeof(struct runlist_element),
                        GFP_NOFS);
        if (!*punch_rl)
                return ERR_PTR(-ENOMEM);

        new_cnt = dst_cnt - (int)(e_rl - s_rl + 1) + 3;
        new_rl = kvcalloc(new_cnt, sizeof(struct runlist_element), GFP_NOFS);
        if (!new_rl) {
                kvfree(*punch_rl);
                *punch_rl = NULL;
                return ERR_PTR(-ENOMEM);
        }

        new_1st_cnt = (int)(s_rl - dst_rl) + 1;
        ntfs_rl_mc(*punch_rl, 0, dst_rl, new_1st_cnt - 1, punch_cnt);
        (*punch_rl)[punch_cnt].lcn = LCN_ENOENT;
        (*punch_rl)[punch_cnt].length = 0;

        if (!begin_split)
                new_1st_cnt--;
        dst_3rd_rl = e_rl;
        dst_3rd_cnt = (int)(&dst_rl[dst_cnt - 1] - e_rl) + 1;
        if (!end_split) {
                dst_3rd_rl++;
                dst_3rd_cnt--;
        }

        /* Copy the 1st part of @dst_rl into @new_rl */
        ntfs_rl_mc(new_rl, 0, dst_rl, 0, new_1st_cnt);
        if (begin_split) {
                /* the @e_rl has to be splited and copied into the last of @new_rl
                 * and the first of @punch_rl
                 */
                s64 first_cnt = start_vcn - dst_rl[new_1st_cnt - 1].vcn;

                new_rl[new_1st_cnt - 1].length = first_cnt;

                (*punch_rl)[0].vcn = start_vcn;
                (*punch_rl)[0].length -= first_cnt;
                if ((*punch_rl)[0].lcn > LCN_HOLE)
                        (*punch_rl)[0].lcn += first_cnt;
        }

        /* Copy the 3rd part of @dst_rl into @new_rl */
        ntfs_rl_mc(new_rl, new_1st_cnt, dst_3rd_rl, 0, dst_3rd_cnt);
        if (end_split) {
                /* the @e_rl has to be splited and copied into the first of
                 * @new_rl and the last of @punch_rl
                 */
                s64 first_cnt = end_vcn - dst_3rd_rl[0].vcn + 1;

                new_rl[new_1st_cnt].vcn = end_vcn + 1;
                new_rl[new_1st_cnt].length -= first_cnt;
                if (new_rl[new_1st_cnt].lcn > LCN_HOLE)
                        new_rl[new_1st_cnt].lcn += first_cnt;

                if (one_split_3)
                        (*punch_rl)[punch_cnt - 1].length -=
                                new_rl[new_1st_cnt].length;
                else
                        (*punch_rl)[punch_cnt - 1].length = first_cnt;
        }

        /* Adjust vcn */
        if (new_1st_cnt == 0)
                new_rl[new_1st_cnt].vcn = 0;
        for (i = new_1st_cnt == 0 ? 1 : new_1st_cnt; new_rl[i].length; i++)
                new_rl[i].vcn = new_rl[i - 1].vcn + new_rl[i - 1].length;
        new_rl[i].vcn = new_rl[i - 1].vcn + new_rl[i - 1].length;

        /* Merge left and hole, or hole and right in @new_rl, if left or right
         * consists of holes.
         */
        merge_cnt = 0;
        if (new_1st_cnt > 0 &&
            ntfs_rle_lcn_contiguous(&new_rl[new_1st_cnt - 1],
                                    &new_rl[new_1st_cnt])) {
                /* Merge right and left. */
                s_rl = &new_rl[new_1st_cnt - 1];
                s_rl->length += s_rl[1].length;
                merge_cnt = 1;
        }
        if (merge_cnt) {
                struct runlist_element *d_rl, *src_rl;

                d_rl = s_rl + 1;
                src_rl = s_rl + 1 + merge_cnt;
                ntfs_rl_mm(new_rl, (int)(d_rl - new_rl), (int)(src_rl - new_rl),
                           (int)(&new_rl[new_cnt - 1] - src_rl) + 1);
        }

        (*punch_rl)[punch_cnt].vcn = (*punch_rl)[punch_cnt - 1].vcn +
                (*punch_rl)[punch_cnt - 1].length;

        /* punch_cnt elements of dst are extracted */
        *new_rl_cnt = dst_cnt - (punch_cnt - (int)begin_split - (int)end_split) -
                merge_cnt;

        kvfree(dst_rl);
        return new_rl;
}