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lcnalloc.c

/*
 * lcnalloc.c - Cluster (de)allocation code.  Part of the Linux-NTFS project.
 *
 * Copyright (c) 2004-2005 Anton Altaparmakov
 *
 * This program/include file is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program/include file is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program (in the main directory of the Linux-NTFS
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#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_CACHE_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_CACHE_MASK;
            buf = page_address(page) + buf_size;
            buf_size = PAGE_CACHE_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 */

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