/*
   * 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 */