// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * lcnalloc.c - Cluster (de)allocation code.  Part of the Linux-NTFS project.
 *
 * Copyright (c) 2004-2005 Anton Altaparmakov
 */

#ifdef NTFS_RW

#include <linux/pagemap.h>

#include "lcnalloc.h"
#include "debug.h"
#include "bitmap.h"
#include "inode.h"
#include "volume.h"
#include "attrib.h"
#include "malloc.h"
#include "aops.h"
#include "ntfs.h"

/**
 * ntfs_cluster_free_from_rl_nolock - free clusters from runlist
 * @vol:        mounted ntfs volume on which to free the clusters
 * @rl:         runlist describing the clusters to free
 *
 * Free all the clusters described by the runlist @rl on the volume @vol.  In
 * the case of an error being returned, at least some of the clusters were not
 * freed.
 *
 * Return 0 on success and -errno on error.
 *
 * Locking: - The volume lcn bitmap must be locked for writing on entry and is
 *            left locked on return.
 */
int ntfs_cluster_free_from_rl_nolock(ntfs_volume *vol,
                const runlist_element *rl)
{
        struct inode *lcnbmp_vi = vol->lcnbmp_ino;
        int ret = 0;

        ntfs_debug("Entering.");
        if (!rl)
                return 0;
        for (; rl->length; rl++) {
                int err;

                if (rl->lcn < 0)
                        continue;
                err = ntfs_bitmap_clear_run(lcnbmp_vi, rl->lcn, rl->length);
                if (unlikely(err && (!ret || ret == -ENOMEM) && ret != err))
                        ret = err;
        }
        ntfs_debug("Done.");
        return ret;
}

/**
 * ntfs_cluster_alloc - allocate clusters on an ntfs volume
 * @vol:        mounted ntfs volume on which to allocate the clusters
 * @start_vcn:  vcn to use for the first allocated cluster
 * @count:      number of clusters to allocate
 * @start_lcn:  starting lcn at which to allocate the clusters (or -1 if none)
 * @zone:       zone from which to allocate the clusters
 * @is_extension:       if 'true', this is an attribute extension
 *
 * Allocate @count clusters preferably starting at cluster @start_lcn or at the
 * current allocator position if @start_lcn is -1, on the mounted ntfs volume
 * @vol. @zone is either DATA_ZONE for allocation of normal clusters or
 * MFT_ZONE for allocation of clusters for the master file table, i.e. the
 * $MFT/$DATA attribute.
 *
 * @start_vcn specifies the vcn of the first allocated cluster.  This makes
 * merging the resulting runlist with the old runlist easier.
 *
 * If @is_extension is 'true', the caller is allocating clusters to extend an
 * attribute and if it is 'false', the caller is allocating clusters to fill a
 * hole in an attribute.  Practically the difference is that if @is_extension
 * is 'true' the returned runlist will be terminated with LCN_ENOENT and if
 * @is_extension is 'false' the runlist will be terminated with
 * LCN_RL_NOT_MAPPED.
 *
 * You need to check the return value with IS_ERR().  If this is false, the
 * function was successful and the return value is a runlist describing the
 * allocated cluster(s).  If IS_ERR() is true, the function failed and
 * PTR_ERR() gives you the error code.
 *
 * Notes on the allocation algorithm
 * =================================
 *
 * There are two data zones.  First is the area between the end of the mft zone
 * and the end of the volume, and second is the area between the start of the
 * volume and the start of the mft zone.  On unmodified/standard NTFS 1.x
 * volumes, the second data zone does not exist due to the mft zone being
 * expanded to cover the start of the volume in order to reserve space for the
 * mft bitmap attribute.
 *
 * This is not the prettiest function but the complexity stems from the need of
 * implementing the mft vs data zoned approach and from the fact that we have
 * access to the lcn bitmap in portions of up to 8192 bytes at a time, so we
 * need to cope with crossing over boundaries of two buffers.  Further, the
 * fact that the allocator allows for caller supplied hints as to the location
 * of where allocation should begin and the fact that the allocator keeps track
 * of where in the data zones the next natural allocation should occur,
 * contribute to the complexity of the function.  But it should all be
 * worthwhile, because this allocator should: 1) be a full implementation of
 * the MFT zone approach used by Windows NT, 2) cause reduction in
 * fragmentation, and 3) be speedy in allocations (the code is not optimized
 * for speed, but the algorithm is, so further speed improvements are probably
 * possible).
 *
 * FIXME: We should be monitoring cluster allocation and increment the MFT zone
 * size dynamically but this is something for the future.  We will just cause
 * heavier fragmentation by not doing it and I am not even sure Windows would
 * grow the MFT zone dynamically, so it might even be correct not to do this.
 * The overhead in doing dynamic MFT zone expansion would be very large and
 * unlikely worth the effort. (AIA)
 *
 * TODO: I have added in double the required zone position pointer wrap around
 * logic which can be optimized to having only one of the two logic sets.
 * However, having the double logic will work fine, but if we have only one of
 * the sets and we get it wrong somewhere, then we get into trouble, so
 * removing the duplicate logic requires _very_ careful consideration of _all_
 * possible code paths.  So at least for now, I am leaving the double logic -
 * better safe than sorry... (AIA)
 *
 * Locking: - The volume lcn bitmap must be unlocked on entry and is unlocked
 *            on return.
 *          - This function takes the volume lcn bitmap lock for writing and
 *            modifies the bitmap contents.
 */
runlist_element *ntfs_cluster_alloc(ntfs_volume *vol, const VCN start_vcn,
                const s64 count, const LCN start_lcn,
                const NTFS_CLUSTER_ALLOCATION_ZONES zone,
                const bool is_extension)
{
        LCN zone_start, zone_end, bmp_pos, bmp_initial_pos, last_read_pos, lcn;
        LCN prev_lcn = 0, prev_run_len = 0, mft_zone_size;
        s64 clusters;
        loff_t i_size;
        struct inode *lcnbmp_vi;
        runlist_element *rl = NULL;
        struct address_space *mapping;
        struct page *page = NULL;
        u8 *buf, *byte;
        int err = 0, rlpos, rlsize, buf_size;
        u8 pass, done_zones, search_zone, need_writeback = 0, bit;

        ntfs_debug("Entering for start_vcn 0x%llx, count 0x%llx, start_lcn "
                        "0x%llx, zone %s_ZONE.", (unsigned long long)start_vcn,
                        (unsigned long long)count,
                        (unsigned long long)start_lcn,
                        zone == MFT_ZONE ? "MFT" : "DATA");
        BUG_ON(!vol);
        lcnbmp_vi = vol->lcnbmp_ino;
        BUG_ON(!lcnbmp_vi);
        BUG_ON(start_vcn < 0);
        BUG_ON(count < 0);
        BUG_ON(start_lcn < -1);
        BUG_ON(zone < FIRST_ZONE);
        BUG_ON(zone > LAST_ZONE);

        /* Return NULL if @count is zero. */
        if (!count)
                return NULL;
        /* Take the lcnbmp lock for writing. */
        down_write(&vol->lcnbmp_lock);
        /*
         * If no specific @start_lcn was requested, use the current data zone
         * position, otherwise use the requested @start_lcn but make sure it
         * lies outside the mft zone.  Also set done_zones to 0 (no zones done)
         * and pass depending on whether we are starting inside a zone (1) or
         * at the beginning of a zone (2).  If requesting from the MFT_ZONE,
         * we either start at the current position within the mft zone or at
         * the specified position.  If the latter is out of bounds then we start
         * at the beginning of the MFT_ZONE.
         */
        done_zones = 0;
        pass = 1;
        /*
         * zone_start and zone_end are the current search range.  search_zone
         * is 1 for mft zone, 2 for data zone 1 (end of mft zone till end of
         * volume) and 4 for data zone 2 (start of volume till start of mft
         * zone).
         */
        zone_start = start_lcn;
        if (zone_start < 0) {
                if (zone == DATA_ZONE)
                        zone_start = vol->data1_zone_pos;
                else
                        zone_start = vol->mft_zone_pos;
                if (!zone_start) {
                        /*
                         * Zone starts at beginning of volume which means a
                         * single pass is sufficient.
                         */
                        pass = 2;
                }
        } else if (zone == DATA_ZONE && zone_start >= vol->mft_zone_start &&
                        zone_start < vol->mft_zone_end) {
                zone_start = vol->mft_zone_end;
                /*
                 * Starting at beginning of data1_zone which means a single
                 * pass in this zone is sufficient.
                 */
                pass = 2;
        } else if (zone == MFT_ZONE && (zone_start < vol->mft_zone_start ||
                        zone_start >= vol->mft_zone_end)) {
                zone_start = vol->mft_lcn;
                if (!vol->mft_zone_end)
                        zone_start = 0;
                /*
                 * Starting at beginning of volume which means a single pass
                 * is sufficient.
                 */
                pass = 2;
        }
        if (zone == MFT_ZONE) {
                zone_end = vol->mft_zone_end;
                search_zone = 1;
        } else /* if (zone == DATA_ZONE) */ {
                /* Skip searching the mft zone. */
                done_zones |= 1;
                if (zone_start >= vol->mft_zone_end) {
                        zone_end = vol->nr_clusters;
                        search_zone = 2;
                } else {
                        zone_end = vol->mft_zone_start;
                        search_zone = 4;
                }
        }
        /*
         * bmp_pos is the current bit position inside the bitmap.  We use
         * bmp_initial_pos to determine whether or not to do a zone switch.
         */
        bmp_pos = bmp_initial_pos = zone_start;

        /* Loop until all clusters are allocated, i.e. clusters == 0. */
        clusters = count;
        rlpos = rlsize = 0;
        mapping = lcnbmp_vi->i_mapping;
        i_size = i_size_read(lcnbmp_vi);
        while (1) {
                ntfs_debug("Start of outer while loop: done_zones 0x%x, "
                                "search_zone %i, pass %i, zone_start 0x%llx, "
                                "zone_end 0x%llx, bmp_initial_pos 0x%llx, "
                                "bmp_pos 0x%llx, rlpos %i, rlsize %i.",
                                done_zones, search_zone, pass,
                                (unsigned long long)zone_start,
                                (unsigned long long)zone_end,
                                (unsigned long long)bmp_initial_pos,
                                (unsigned long long)bmp_pos, rlpos, rlsize);
                /* Loop until we run out of free clusters. */
                last_read_pos = bmp_pos >> 3;
                ntfs_debug("last_read_pos 0x%llx.",
                                (unsigned long long)last_read_pos);
                if (last_read_pos > i_size) {
                        ntfs_debug("End of attribute reached.  "
                                        "Skipping to zone_pass_done.");
                        goto zone_pass_done;
                }
                if (likely(page)) {
                        if (need_writeback) {
                                ntfs_debug("Marking page dirty.");
                                flush_dcache_page(page);
                                set_page_dirty(page);
                                need_writeback = 0;
                        }
                        ntfs_unmap_page(page);
                }
                page = ntfs_map_page(mapping, last_read_pos >>
                                PAGE_SHIFT);
                if (IS_ERR(page)) {
                        err = PTR_ERR(page);
                        ntfs_error(vol->sb, "Failed to map page.");
                        goto out;
                }
                buf_size = last_read_pos & ~PAGE_MASK;
                buf = page_address(page) + buf_size;
                buf_size = PAGE_SIZE - buf_size;
                if (unlikely(last_read_pos + buf_size > i_size))
                        buf_size = i_size - last_read_pos;
                buf_size <<= 3;
                lcn = bmp_pos & 7;
                bmp_pos &= ~(LCN)7;
                ntfs_debug("Before inner while loop: buf_size %i, lcn 0x%llx, "
                                "bmp_pos 0x%llx, need_writeback %i.", buf_size,
                                (unsigned long long)lcn,
                                (unsigned long long)bmp_pos, need_writeback);
                while (lcn < buf_size && lcn + bmp_pos < zone_end) {
                        byte = buf + (lcn >> 3);
                        ntfs_debug("In inner while loop: buf_size %i, "
                                        "lcn 0x%llx, bmp_pos 0x%llx, "
                                        "need_writeback %i, byte ofs 0x%x, "
                                        "*byte 0x%x.", buf_size,
                                        (unsigned long long)lcn,
                                        (unsigned long long)bmp_pos,
                                        need_writeback,
                                        (unsigned int)(lcn >> 3),
                                        (unsigned int)*byte);
                        /* Skip full bytes. */
                        if (*byte == 0xff) {
                                lcn = (lcn + 8) & ~(LCN)7;
                                ntfs_debug("Continuing while loop 1.");
                                continue;
                        }
                        bit = 1 << (lcn & 7);
                        ntfs_debug("bit 0x%x.", bit);
                        /* If the bit is already set, go onto the next one. */
                        if (*byte & bit) {
                                lcn++;
                                ntfs_debug("Continuing while loop 2.");
                                continue;
                        }
                        /*
                         * Allocate more memory if needed, including space for
                         * the terminator element.
                         * ntfs_malloc_nofs() operates on whole pages only.
                         */
                        if ((rlpos + 2) * sizeof(*rl) > rlsize) {
                                runlist_element *rl2;

                                ntfs_debug("Reallocating memory.");
                                if (!rl)
                                        ntfs_debug("First free bit is at LCN "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        (lcn + bmp_pos));
                                rl2 = ntfs_malloc_nofs(rlsize + (int)PAGE_SIZE);
                                if (unlikely(!rl2)) {
                                        err = -ENOMEM;
                                        ntfs_error(vol->sb, "Failed to "
                                                        "allocate memory.");
                                        goto out;
                                }
                                memcpy(rl2, rl, rlsize);
                                ntfs_free(rl);
                                rl = rl2;
                                rlsize += PAGE_SIZE;
                                ntfs_debug("Reallocated memory, rlsize 0x%x.",
                                                rlsize);
                        }
                        /* Allocate the bitmap bit. */
                        *byte |= bit;
                        /* We need to write this bitmap page to disk. */
                        need_writeback = 1;
                        ntfs_debug("*byte 0x%x, need_writeback is set.",
                                        (unsigned int)*byte);
                        /*
                         * Coalesce with previous run if adjacent LCNs.
                         * Otherwise, append a new run.
                         */
                        ntfs_debug("Adding run (lcn 0x%llx, len 0x%llx), "
                                        "prev_lcn 0x%llx, lcn 0x%llx, "
                                        "bmp_pos 0x%llx, prev_run_len 0x%llx, "
                                        "rlpos %i.",
                                        (unsigned long long)(lcn + bmp_pos),
                                        1ULL, (unsigned long long)prev_lcn,
                                        (unsigned long long)lcn,
                                        (unsigned long long)bmp_pos,
                                        (unsigned long long)prev_run_len,
                                        rlpos);
                        if (prev_lcn == lcn + bmp_pos - prev_run_len && rlpos) {
                                ntfs_debug("Coalescing to run (lcn 0x%llx, "
                                                "len 0x%llx).",
                                                (unsigned long long)
                                                rl[rlpos - 1].lcn,
                                                (unsigned long long)
                                                rl[rlpos - 1].length);
                                rl[rlpos - 1].length = ++prev_run_len;
                                ntfs_debug("Run now (lcn 0x%llx, len 0x%llx), "
                                                "prev_run_len 0x%llx.",
                                                (unsigned long long)
                                                rl[rlpos - 1].lcn,
                                                (unsigned long long)
                                                rl[rlpos - 1].length,
                                                (unsigned long long)
                                                prev_run_len);
                        } else {
                                if (likely(rlpos)) {
                                        ntfs_debug("Adding new run, (previous "
                                                        "run lcn 0x%llx, "
                                                        "len 0x%llx).",
                                                        (unsigned long long)
                                                        rl[rlpos - 1].lcn,
                                                        (unsigned long long)
                                                        rl[rlpos - 1].length);
                                        rl[rlpos].vcn = rl[rlpos - 1].vcn +
                                                        prev_run_len;
                                } else {
                                        ntfs_debug("Adding new run, is first "
                                                        "run.");
                                        rl[rlpos].vcn = start_vcn;
                                }
                                rl[rlpos].lcn = prev_lcn = lcn + bmp_pos;
                                rl[rlpos].length = prev_run_len = 1;
                                rlpos++;
                        }
                        /* Done? */
                        if (!--clusters) {
                                LCN tc;
                                /*
                                 * Update the current zone position.  Positions
                                 * of already scanned zones have been updated
                                 * during the respective zone switches.
                                 */
                                tc = lcn + bmp_pos + 1;
                                ntfs_debug("Done. Updating current zone "
                                                "position, tc 0x%llx, "
                                                "search_zone %i.",
                                                (unsigned long long)tc,
                                                search_zone);
                                switch (search_zone) {
                                case 1:
                                        ntfs_debug("Before checks, "
                                                        "vol->mft_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->mft_zone_pos);
                                        if (tc >= vol->mft_zone_end) {
                                                vol->mft_zone_pos =
                                                                vol->mft_lcn;
                                                if (!vol->mft_zone_end)
                                                        vol->mft_zone_pos = 0;
                                        } else if ((bmp_initial_pos >=
                                                        vol->mft_zone_pos ||
                                                        tc > vol->mft_zone_pos)
                                                        && tc >= vol->mft_lcn)
                                                vol->mft_zone_pos = tc;
                                        ntfs_debug("After checks, "
                                                        "vol->mft_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->mft_zone_pos);
                                        break;
                                case 2:
                                        ntfs_debug("Before checks, "
                                                        "vol->data1_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->data1_zone_pos);
                                        if (tc >= vol->nr_clusters)
                                                vol->data1_zone_pos =
                                                             vol->mft_zone_end;
                                        else if ((bmp_initial_pos >=
                                                    vol->data1_zone_pos ||
                                                    tc > vol->data1_zone_pos)
                                                    && tc >= vol->mft_zone_end)
                                                vol->data1_zone_pos = tc;
                                        ntfs_debug("After checks, "
                                                        "vol->data1_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->data1_zone_pos);
                                        break;
                                case 4:
                                        ntfs_debug("Before checks, "
                                                        "vol->data2_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->data2_zone_pos);
                                        if (tc >= vol->mft_zone_start)
                                                vol->data2_zone_pos = 0;
                                        else if (bmp_initial_pos >=
                                                      vol->data2_zone_pos ||
                                                      tc > vol->data2_zone_pos)
                                                vol->data2_zone_pos = tc;
                                        ntfs_debug("After checks, "
                                                        "vol->data2_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->data2_zone_pos);
                                        break;
                                default:
                                        BUG();
                                }
                                ntfs_debug("Finished.  Going to out.");
                                goto out;
                        }
                        lcn++;
                }
                bmp_pos += buf_size;
                ntfs_debug("After inner while loop: buf_size 0x%x, lcn "
                                "0x%llx, bmp_pos 0x%llx, need_writeback %i.",
                                buf_size, (unsigned long long)lcn,
                                (unsigned long long)bmp_pos, need_writeback);
                if (bmp_pos < zone_end) {
                        ntfs_debug("Continuing outer while loop, "
                                        "bmp_pos 0x%llx, zone_end 0x%llx.",
                                        (unsigned long long)bmp_pos,
                                        (unsigned long long)zone_end);
                        continue;
                }
zone_pass_done: /* Finished with the current zone pass. */
                ntfs_debug("At zone_pass_done, pass %i.", pass);
                if (pass == 1) {
                        /*
                         * Now do pass 2, scanning the first part of the zone
                         * we omitted in pass 1.
                         */
                        pass = 2;
                        zone_end = zone_start;
                        switch (search_zone) {
                        case 1: /* mft_zone */
                                zone_start = vol->mft_zone_start;
                                break;
                        case 2: /* data1_zone */
                                zone_start = vol->mft_zone_end;
                                break;
                        case 4: /* data2_zone */
                                zone_start = 0;
                                break;
                        default:
                                BUG();
                        }
                        /* Sanity check. */
                        if (zone_end < zone_start)
                                zone_end = zone_start;
                        bmp_pos = zone_start;
                        ntfs_debug("Continuing outer while loop, pass 2, "
                                        "zone_start 0x%llx, zone_end 0x%llx, "
                                        "bmp_pos 0x%llx.",
                                        (unsigned long long)zone_start,
                                        (unsigned long long)zone_end,
                                        (unsigned long long)bmp_pos);
                        continue;
                } /* pass == 2 */
done_zones_check:
                ntfs_debug("At done_zones_check, search_zone %i, done_zones "
                                "before 0x%x, done_zones after 0x%x.",
                                search_zone, done_zones,
                                done_zones | search_zone);
                done_zones |= search_zone;
                if (done_zones < 7) {
                        ntfs_debug("Switching zone.");
                        /* Now switch to the next zone we haven't done yet. */
                        pass = 1;
                        switch (search_zone) {
                        case 1:
                                ntfs_debug("Switching from mft zone to data1 "
                                                "zone.");
                                /* Update mft zone position. */
                                if (rlpos) {
                                        LCN tc;

                                        ntfs_debug("Before checks, "
                                                        "vol->mft_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->mft_zone_pos);
                                        tc = rl[rlpos - 1].lcn +
                                                        rl[rlpos - 1].length;
                                        if (tc >= vol->mft_zone_end) {
                                                vol->mft_zone_pos =
                                                                vol->mft_lcn;
                                                if (!vol->mft_zone_end)
                                                        vol->mft_zone_pos = 0;
                                        } else if ((bmp_initial_pos >=
                                                        vol->mft_zone_pos ||
                                                        tc > vol->mft_zone_pos)
                                                        && tc >= vol->mft_lcn)
                                                vol->mft_zone_pos = tc;
                                        ntfs_debug("After checks, "
                                                        "vol->mft_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->mft_zone_pos);
                                }
                                /* Switch from mft zone to data1 zone. */
switch_to_data1_zone:           search_zone = 2;
                                zone_start = bmp_initial_pos =
                                                vol->data1_zone_pos;
                                zone_end = vol->nr_clusters;
                                if (zone_start == vol->mft_zone_end)
                                        pass = 2;
                                if (zone_start >= zone_end) {
                                        vol->data1_zone_pos = zone_start =
                                                        vol->mft_zone_end;
                                        pass = 2;
                                }
                                break;
                        case 2:
                                ntfs_debug("Switching from data1 zone to "
                                                "data2 zone.");
                                /* Update data1 zone position. */
                                if (rlpos) {
                                        LCN tc;

                                        ntfs_debug("Before checks, "
                                                        "vol->data1_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->data1_zone_pos);
                                        tc = rl[rlpos - 1].lcn +
                                                        rl[rlpos - 1].length;
                                        if (tc >= vol->nr_clusters)
                                                vol->data1_zone_pos =
                                                             vol->mft_zone_end;
                                        else if ((bmp_initial_pos >=
                                                    vol->data1_zone_pos ||
                                                    tc > vol->data1_zone_pos)
                                                    && tc >= vol->mft_zone_end)
                                                vol->data1_zone_pos = tc;
                                        ntfs_debug("After checks, "
                                                        "vol->data1_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->data1_zone_pos);
                                }
                                /* Switch from data1 zone to data2 zone. */
                                search_zone = 4;
                                zone_start = bmp_initial_pos =
                                                vol->data2_zone_pos;
                                zone_end = vol->mft_zone_start;
                                if (!zone_start)
                                        pass = 2;
                                if (zone_start >= zone_end) {
                                        vol->data2_zone_pos = zone_start =
                                                        bmp_initial_pos = 0;
                                        pass = 2;
                                }
                                break;
                        case 4:
                                ntfs_debug("Switching from data2 zone to "
                                                "data1 zone.");
                                /* Update data2 zone position. */
                                if (rlpos) {
                                        LCN tc;

                                        ntfs_debug("Before checks, "
                                                        "vol->data2_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->data2_zone_pos);
                                        tc = rl[rlpos - 1].lcn +
                                                        rl[rlpos - 1].length;
                                        if (tc >= vol->mft_zone_start)
                                                vol->data2_zone_pos = 0;
                                        else if (bmp_initial_pos >=
                                                      vol->data2_zone_pos ||
                                                      tc > vol->data2_zone_pos)
                                                vol->data2_zone_pos = tc;
                                        ntfs_debug("After checks, "
                                                        "vol->data2_zone_pos "
                                                        "0x%llx.",
                                                        (unsigned long long)
                                                        vol->data2_zone_pos);
                                }
                                /* Switch from data2 zone to data1 zone. */
                                goto switch_to_data1_zone;
                        default:
                                BUG();
                        }
                        ntfs_debug("After zone switch, search_zone %i, "
                                        "pass %i, bmp_initial_pos 0x%llx, "
                                        "zone_start 0x%llx, zone_end 0x%llx.",
                                        search_zone, pass,
                                        (unsigned long long)bmp_initial_pos,
                                        (unsigned long long)zone_start,
                                        (unsigned long long)zone_end);
                        bmp_pos = zone_start;
                        if (zone_start == zone_end) {
                                ntfs_debug("Empty zone, going to "
                                                "done_zones_check.");
                                /* Empty zone. Don't bother searching it. */
                                goto done_zones_check;
                        }
                        ntfs_debug("Continuing outer while loop.");
                        continue;
                } /* done_zones == 7 */
                ntfs_debug("All zones are finished.");
                /*
                 * All zones are finished!  If DATA_ZONE, shrink mft zone.  If
                 * MFT_ZONE, we have really run out of space.
                 */
                mft_zone_size = vol->mft_zone_end - vol->mft_zone_start;
                ntfs_debug("vol->mft_zone_start 0x%llx, vol->mft_zone_end "
                                "0x%llx, mft_zone_size 0x%llx.",
                                (unsigned long long)vol->mft_zone_start,
                                (unsigned long long)vol->mft_zone_end,
                                (unsigned long long)mft_zone_size);
                if (zone == MFT_ZONE || mft_zone_size <= 0) {
                        ntfs_debug("No free clusters left, going to out.");
                        /* Really no more space left on device. */
                        err = -ENOSPC;
                        goto out;
                } /* zone == DATA_ZONE && mft_zone_size > 0 */
                ntfs_debug("Shrinking mft zone.");
                zone_end = vol->mft_zone_end;
                mft_zone_size >>= 1;
                if (mft_zone_size > 0)
                        vol->mft_zone_end = vol->mft_zone_start + mft_zone_size;
                else /* mft zone and data2 zone no longer exist. */
                        vol->data2_zone_pos = vol->mft_zone_start =
                                        vol->mft_zone_end = 0;
                if (vol->mft_zone_pos >= vol->mft_zone_end) {
                        vol->mft_zone_pos = vol->mft_lcn;
                        if (!vol->mft_zone_end)
                                vol->mft_zone_pos = 0;
                }
                bmp_pos = zone_start = bmp_initial_pos =
                                vol->data1_zone_pos = vol->mft_zone_end;
                search_zone = 2;
                pass = 2;
                done_zones &= ~2;
                ntfs_debug("After shrinking mft zone, mft_zone_size 0x%llx, "
                                "vol->mft_zone_start 0x%llx, "
                                "vol->mft_zone_end 0x%llx, "
                                "vol->mft_zone_pos 0x%llx, search_zone 2, "
                                "pass 2, dones_zones 0x%x, zone_start 0x%llx, "
                                "zone_end 0x%llx, vol->data1_zone_pos 0x%llx, "
                                "continuing outer while loop.",
                                (unsigned long long)mft_zone_size,
                                (unsigned long long)vol->mft_zone_start,
                                (unsigned long long)vol->mft_zone_end,
                                (unsigned long long)vol->mft_zone_pos,
                                done_zones, (unsigned long long)zone_start,
                                (unsigned long long)zone_end,
                                (unsigned long long)vol->data1_zone_pos);
        }
        ntfs_debug("After outer while loop.");
out:
        ntfs_debug("At out.");
        /* Add runlist terminator element. */
        if (likely(rl)) {
                rl[rlpos].vcn = rl[rlpos - 1].vcn + rl[rlpos - 1].length;
                rl[rlpos].lcn = is_extension ? LCN_ENOENT : LCN_RL_NOT_MAPPED;
                rl[rlpos].length = 0;
        }
        if (likely(page && !IS_ERR(page))) {
                if (need_writeback) {
                        ntfs_debug("Marking page dirty.");
                        flush_dcache_page(page);
                        set_page_dirty(page);
                        need_writeback = 0;
                }
                ntfs_unmap_page(page);
        }
        if (likely(!err)) {
                up_write(&vol->lcnbmp_lock);
                ntfs_debug("Done.");
                return rl;
        }
        ntfs_error(vol->sb, "Failed to allocate clusters, aborting "
                        "(error %i).", err);
        if (rl) {
                int err2;

                if (err == -ENOSPC)
                        ntfs_debug("Not enough space to complete allocation, "
                                        "err -ENOSPC, first free lcn 0x%llx, "
                                        "could allocate up to 0x%llx "
                                        "clusters.",
                                        (unsigned long long)rl[0].lcn,
                                        (unsigned long long)(count - clusters));
                /* Deallocate all allocated clusters. */
                ntfs_debug("Attempting rollback...");
                err2 = ntfs_cluster_free_from_rl_nolock(vol, rl);
                if (err2) {
                        ntfs_error(vol->sb, "Failed to rollback (error %i).  "
                                        "Leaving inconsistent metadata!  "
                                        "Unmount and run chkdsk.", err2);
                        NVolSetErrors(vol);
                }
                /* Free the runlist. */
                ntfs_free(rl);
        } else if (err == -ENOSPC)
                ntfs_debug("No space left at all, err = -ENOSPC, first free "
                                "lcn = 0x%llx.",
                                (long long)vol->data1_zone_pos);
        up_write(&vol->lcnbmp_lock);
        return ERR_PTR(err);
}

/**
 * __ntfs_cluster_free - free clusters on an ntfs volume
 * @ni:         ntfs inode whose runlist describes the clusters to free
 * @start_vcn:  vcn in the runlist of @ni at which to start freeing clusters
 * @count:      number of clusters to free or -1 for all clusters
 * @ctx:        active attribute search context if present or NULL if not
 * @is_rollback:        true if this is a rollback operation
 *
 * Free @count clusters starting at the cluster @start_vcn in the runlist
 * described by the vfs inode @ni.
 *
 * If @count is -1, all clusters from @start_vcn to the end of the runlist are
 * deallocated.  Thus, to completely free all clusters in a runlist, use
 * @start_vcn = 0 and @count = -1.
 *
 * If @ctx is specified, it is an active search context of @ni and its base mft
 * record.  This is needed when __ntfs_cluster_free() encounters unmapped
 * runlist fragments and allows their mapping.  If you do not have the mft
 * record mapped, you can specify @ctx as NULL and __ntfs_cluster_free() will
 * perform the necessary mapping and unmapping.
 *
 * Note, __ntfs_cluster_free() saves the state of @ctx on entry and restores it
 * before returning.  Thus, @ctx will be left pointing to the same attribute on
 * return as on entry.  However, the actual pointers in @ctx may point to
 * different memory locations on return, so you must remember to reset any
 * cached pointers from the @ctx, i.e. after the call to __ntfs_cluster_free(),
 * you will probably want to do:
 *      m = ctx->mrec;
 *      a = ctx->attr;
 * Assuming you cache ctx->attr in a variable @a of type ATTR_RECORD * and that
 * you cache ctx->mrec in a variable @m of type MFT_RECORD *.
 *
 * @is_rollback should always be 'false', it is for internal use to rollback
 * errors.  You probably want to use ntfs_cluster_free() instead.
 *
 * Note, __ntfs_cluster_free() does not modify the runlist, so you have to
 * remove from the runlist or mark sparse the freed runs later.
 *
 * Return the number of deallocated clusters (not counting sparse ones) on
 * success and -errno on error.
 *
 * WARNING: If @ctx is supplied, regardless of whether success or failure is
 *          returned, you need to check IS_ERR(@ctx->mrec) and if 'true' the @ctx
 *          is no longer valid, i.e. you need to either call
 *          ntfs_attr_reinit_search_ctx() or ntfs_attr_put_search_ctx() on it.
 *          In that case PTR_ERR(@ctx->mrec) will give you the error code for
 *          why the mapping of the old inode failed.
 *
 * Locking: - The runlist described by @ni must be locked for writing on entry
 *            and is locked on return.  Note the runlist may be modified when
 *            needed runlist fragments need to be mapped.
 *          - The volume lcn bitmap must be unlocked on entry and is unlocked
 *            on return.
 *          - This function takes the volume lcn bitmap lock for writing and
 *            modifies the bitmap contents.
 *          - If @ctx is NULL, the base mft record of @ni must not be mapped on
 *            entry and it will be left unmapped on return.
 *          - If @ctx is not NULL, the base mft record must be mapped on entry
 *            and it will be left mapped on return.
 */
s64 __ntfs_cluster_free(ntfs_inode *ni, const VCN start_vcn, s64 count,
                ntfs_attr_search_ctx *ctx, const bool is_rollback)
{
        s64 delta, to_free, total_freed, real_freed;
        ntfs_volume *vol;
        struct inode *lcnbmp_vi;
        runlist_element *rl;
        int err;

        BUG_ON(!ni);
        ntfs_debug("Entering for i_ino 0x%lx, start_vcn 0x%llx, count "
                        "0x%llx.%s", ni->mft_no, (unsigned long long)start_vcn,
                        (unsigned long long)count,
                        is_rollback ? " (rollback)" : "");
        vol = ni->vol;
        lcnbmp_vi = vol->lcnbmp_ino;
        BUG_ON(!lcnbmp_vi);
        BUG_ON(start_vcn < 0);
        BUG_ON(count < -1);
        /*
         * Lock the lcn bitmap for writing but only if not rolling back.  We
         * must hold the lock all the way including through rollback otherwise
         * rollback is not possible because once we have cleared a bit and
         * dropped the lock, anyone could have set the bit again, thus
         * allocating the cluster for another use.
         */
        if (likely(!is_rollback))
                down_write(&vol->lcnbmp_lock);

        total_freed = real_freed = 0;

        rl = ntfs_attr_find_vcn_nolock(ni, start_vcn, ctx);
        if (IS_ERR(rl)) {
                if (!is_rollback)
                        ntfs_error(vol->sb, "Failed to find first runlist "
                                        "element (error %li), aborting.",
                                        PTR_ERR(rl));
                err = PTR_ERR(rl);
                goto err_out;
        }
        if (unlikely(rl->lcn < LCN_HOLE)) {
                if (!is_rollback)
                        ntfs_error(vol->sb, "First runlist element has "
                                        "invalid lcn, aborting.");
                err = -EIO;
                goto err_out;
        }
        /* Find the starting cluster inside the run that needs freeing. */
        delta = start_vcn - rl->vcn;

        /* The number of clusters in this run that need freeing. */
        to_free = rl->length - delta;
        if (count >= 0 && to_free > count)
                to_free = count;

        if (likely(rl->lcn >= 0)) {
                /* Do the actual freeing of the clusters in this run. */
                err = ntfs_bitmap_set_bits_in_run(lcnbmp_vi, rl->lcn + delta,
                                to_free, likely(!is_rollback) ? 0 : 1);
                if (unlikely(err)) {
                        if (!is_rollback)
                                ntfs_error(vol->sb, "Failed to clear first run "
                                                "(error %i), aborting.", err);
                        goto err_out;
                }
                /* We have freed @to_free real clusters. */
                real_freed = to_free;
        };
        /* Go to the next run and adjust the number of clusters left to free. */
        ++rl;
        if (count >= 0)
                count -= to_free;

        /* Keep track of the total "freed" clusters, including sparse ones. */
        total_freed = to_free;
        /*
         * Loop over the remaining runs, using @count as a capping value, and
         * free them.
         */
        for (; rl->length && count != 0; ++rl) {
                if (unlikely(rl->lcn < LCN_HOLE)) {
                        VCN vcn;

                        /* Attempt to map runlist. */
                        vcn = rl->vcn;
                        rl = ntfs_attr_find_vcn_nolock(ni, vcn, ctx);
                        if (IS_ERR(rl)) {
                                err = PTR_ERR(rl);
                                if (!is_rollback)
                                        ntfs_error(vol->sb, "Failed to map "
                                                        "runlist fragment or "
                                                        "failed to find "
                                                        "subsequent runlist "
                                                        "element.");
                                goto err_out;
                        }
                        if (unlikely(rl->lcn < LCN_HOLE)) {
                                if (!is_rollback)
                                        ntfs_error(vol->sb, "Runlist element "
                                                        "has invalid lcn "
                                                        "(0x%llx).",
                                                        (unsigned long long)
                                                        rl->lcn);
                                err = -EIO;
                                goto err_out;
                        }
                }
                /* The number of clusters in this run that need freeing. */
                to_free = rl->length;
                if (count >= 0 && to_free > count)
                        to_free = count;

                if (likely(rl->lcn >= 0)) {
                        /* Do the actual freeing of the clusters in the run. */
                        err = ntfs_bitmap_set_bits_in_run(lcnbmp_vi, rl->lcn,
                                        to_free, likely(!is_rollback) ? 0 : 1);
                        if (unlikely(err)) {
                                if (!is_rollback)
                                        ntfs_error(vol->sb, "Failed to clear "
                                                        "subsequent run.");
                                goto err_out;
                        }
                        /* We have freed @to_free real clusters. */
                        real_freed += to_free;
                }
                /* Adjust the number of clusters left to free. */
                if (count >= 0)
                        count -= to_free;
        
                /* Update the total done clusters. */
                total_freed += to_free;
        }
        if (likely(!is_rollback))
                up_write(&vol->lcnbmp_lock);

        BUG_ON(count > 0);

        /* We are done.  Return the number of actually freed clusters. */
        ntfs_debug("Done.");
        return real_freed;
err_out:
        if (is_rollback)
                return err;
        /* If no real clusters were freed, no need to rollback. */
        if (!real_freed) {
                up_write(&vol->lcnbmp_lock);
                return err;
        }
        /*
         * Attempt to rollback and if that succeeds just return the error code.
         * If rollback fails, set the volume errors flag, emit an error
         * message, and return the error code.
         */
        delta = __ntfs_cluster_free(ni, start_vcn, total_freed, ctx, true);
        if (delta < 0) {
                ntfs_error(vol->sb, "Failed to rollback (error %i).  Leaving "
                                "inconsistent metadata!  Unmount and run "
                                "chkdsk.", (int)delta);
                NVolSetErrors(vol);
        }
        up_write(&vol->lcnbmp_lock);
        ntfs_error(vol->sb, "Aborting (error %i).", err);
        return err;
}

#endif /* NTFS_RW */