// SPDX-License-Identifier: GPL-2.0-only

  /* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * reservations.c
   *
   * Allocation reservations implementation
   *
   * Some code borrowed from fs/ext3/balloc.c and is:
   *
   * Copyright (C) 1992, 1993, 1994, 1995
   * Remy Card (card@masi.ibp.fr)
   * Laboratoire MASI - Institut Blaise Pascal
   * Universite Pierre et Marie Curie (Paris VI)
   *
   * The rest is copyright (C) 2010 Novell.  All rights reserved.

   */
  
  #include <linux/fs.h>
  #include <linux/types.h>

  #include <linux/highmem.h>
  #include <linux/bitops.h>
  #include <linux/list.h>

  #include <cluster/masklog.h>
  
  #include "ocfs2.h"

  #include "ocfs2_trace.h"

  
  #ifdef CONFIG_OCFS2_DEBUG_FS
  #define OCFS2_CHECK_RESERVATIONS
  #endif

  static DEFINE_SPINLOCK(resv_lock);

  int ocfs2_dir_resv_allowed(struct ocfs2_super *osb)
  {
  	return (osb->osb_resv_level && osb->osb_dir_resv_level);
  }

  
  static unsigned int ocfs2_resv_window_bits(struct ocfs2_reservation_map *resmap,
  					   struct ocfs2_alloc_reservation *resv)
  {
  	struct ocfs2_super *osb = resmap->m_osb;
  	unsigned int bits;

  	if (!(resv->r_flags & OCFS2_RESV_FLAG_DIR)) {
  		/* 8, 16, 32, 64, 128, 256, 512, 1024 */
  		bits = 4 << osb->osb_resv_level;

  	} else {

  		bits = 4 << osb->osb_dir_resv_level;

  	}

  	return bits;
  }
  
  static inline unsigned int ocfs2_resv_end(struct ocfs2_alloc_reservation *resv)
  {
  	if (resv->r_len)
  		return resv->r_start + resv->r_len - 1;
  	return resv->r_start;
  }
  
  static inline int ocfs2_resv_empty(struct ocfs2_alloc_reservation *resv)
  {
  	return !!(resv->r_len == 0);
  }
  
  static inline int ocfs2_resmap_disabled(struct ocfs2_reservation_map *resmap)
  {
  	if (resmap->m_osb->osb_resv_level == 0)
  		return 1;
  	return 0;
  }
  
  static void ocfs2_dump_resv(struct ocfs2_reservation_map *resmap)
  {
  	struct ocfs2_super *osb = resmap->m_osb;
  	struct rb_node *node;
  	struct ocfs2_alloc_reservation *resv;
  	int i = 0;
  
  	mlog(ML_NOTICE, "Dumping resmap for device %s. Bitmap length: %u
  ",
  	     osb->dev_str, resmap->m_bitmap_len);
  
  	node = rb_first(&resmap->m_reservations);
  	while (node) {
  		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
  
  		mlog(ML_NOTICE, "start: %u\tend: %u\tlen: %u\tlast_start: %u"
  		     "\tlast_len: %u
  ", resv->r_start,
  		     ocfs2_resv_end(resv), resv->r_len, resv->r_last_start,
  		     resv->r_last_len);
  
  		node = rb_next(node);
  		i++;
  	}
  
  	mlog(ML_NOTICE, "%d reservations found. LRU follows
  ", i);
  
  	i = 0;
  	list_for_each_entry(resv, &resmap->m_lru, r_lru) {
  		mlog(ML_NOTICE, "LRU(%d) start: %u\tend: %u\tlen: %u\t"
  		     "last_start: %u\tlast_len: %u
  ", i, resv->r_start,
  		     ocfs2_resv_end(resv), resv->r_len, resv->r_last_start,
  		     resv->r_last_len);
  
  		i++;
  	}
  }
  
  #ifdef OCFS2_CHECK_RESERVATIONS
  static int ocfs2_validate_resmap_bits(struct ocfs2_reservation_map *resmap,
  				      int i,
  				      struct ocfs2_alloc_reservation *resv)
  {
  	char *disk_bitmap = resmap->m_disk_bitmap;
  	unsigned int start = resv->r_start;
  	unsigned int end = ocfs2_resv_end(resv);
  
  	while (start <= end) {
  		if (ocfs2_test_bit(start, disk_bitmap)) {
  			mlog(ML_ERROR,
  			     "reservation %d covers an allocated area "
  			     "starting at bit %u!
  ", i, start);
  			return 1;
  		}
  
  		start++;
  	}
  	return 0;
  }
  
  static void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
  {
  	unsigned int off = 0;
  	int i = 0;
  	struct rb_node *node;
  	struct ocfs2_alloc_reservation *resv;
  
  	node = rb_first(&resmap->m_reservations);
  	while (node) {
  		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
  
  		if (i > 0 && resv->r_start <= off) {
  			mlog(ML_ERROR, "reservation %d has bad start off!
  ",
  			     i);
  			goto bad;
  		}
  
  		if (resv->r_len == 0) {
  			mlog(ML_ERROR, "reservation %d has no length!
  ",
  			     i);
  			goto bad;
  		}
  
  		if (resv->r_start > ocfs2_resv_end(resv)) {
  			mlog(ML_ERROR, "reservation %d has invalid range!
  ",
  			     i);
  			goto bad;
  		}
  
  		if (ocfs2_resv_end(resv) >= resmap->m_bitmap_len) {
  			mlog(ML_ERROR, "reservation %d extends past bitmap!
  ",
  			     i);
  			goto bad;
  		}
  
  		if (ocfs2_validate_resmap_bits(resmap, i, resv))
  			goto bad;
  
  		off = ocfs2_resv_end(resv);
  		node = rb_next(node);
  
  		i++;
  	}
  	return;
  
  bad:
  	ocfs2_dump_resv(resmap);
  	BUG();
  }
  #else
  static inline void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
  {
  
  }
  #endif
  
  void ocfs2_resv_init_once(struct ocfs2_alloc_reservation *resv)
  {
  	memset(resv, 0, sizeof(*resv));
  	INIT_LIST_HEAD(&resv->r_lru);
  }
  
  void ocfs2_resv_set_type(struct ocfs2_alloc_reservation *resv,
  			 unsigned int flags)
  {
  	BUG_ON(flags & ~OCFS2_RESV_TYPES);
  
  	resv->r_flags |= flags;
  }
  
  int ocfs2_resmap_init(struct ocfs2_super *osb,
  		      struct ocfs2_reservation_map *resmap)
  {
  	memset(resmap, 0, sizeof(*resmap));
  
  	resmap->m_osb = osb;
  	resmap->m_reservations = RB_ROOT;
  	/* m_bitmap_len is initialized to zero by the above memset. */
  	INIT_LIST_HEAD(&resmap->m_lru);
  
  	return 0;
  }
  
  static void ocfs2_resv_mark_lru(struct ocfs2_reservation_map *resmap,
  				struct ocfs2_alloc_reservation *resv)
  {
  	assert_spin_locked(&resv_lock);
  
  	if (!list_empty(&resv->r_lru))
  		list_del_init(&resv->r_lru);
  
  	list_add_tail(&resv->r_lru, &resmap->m_lru);
  }
  
  static void __ocfs2_resv_trunc(struct ocfs2_alloc_reservation *resv)
  {
  	resv->r_len = 0;
  	resv->r_start = 0;
  }
  
  static void ocfs2_resv_remove(struct ocfs2_reservation_map *resmap,
  			      struct ocfs2_alloc_reservation *resv)
  {
  	if (resv->r_flags & OCFS2_RESV_FLAG_INUSE) {
  		list_del_init(&resv->r_lru);
  		rb_erase(&resv->r_node, &resmap->m_reservations);
  		resv->r_flags &= ~OCFS2_RESV_FLAG_INUSE;
  	}
  }
  
  static void __ocfs2_resv_discard(struct ocfs2_reservation_map *resmap,
  				 struct ocfs2_alloc_reservation *resv)
  {
  	assert_spin_locked(&resv_lock);
  
  	__ocfs2_resv_trunc(resv);
  	/*
  	 * last_len and last_start no longer make sense if
  	 * we're changing the range of our allocations.
  	 */
  	resv->r_last_len = resv->r_last_start = 0;
  
  	ocfs2_resv_remove(resmap, resv);
  }
  
  /* does nothing if 'resv' is null */
  void ocfs2_resv_discard(struct ocfs2_reservation_map *resmap,
  			struct ocfs2_alloc_reservation *resv)
  {
  	if (resv) {
  		spin_lock(&resv_lock);
  		__ocfs2_resv_discard(resmap, resv);
  		spin_unlock(&resv_lock);
  	}
  }
  
  static void ocfs2_resmap_clear_all_resv(struct ocfs2_reservation_map *resmap)
  {
  	struct rb_node *node;
  	struct ocfs2_alloc_reservation *resv;
  
  	assert_spin_locked(&resv_lock);
  
  	while ((node = rb_last(&resmap->m_reservations)) != NULL) {
  		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
  
  		__ocfs2_resv_discard(resmap, resv);
  	}
  }
  
  void ocfs2_resmap_restart(struct ocfs2_reservation_map *resmap,
  			  unsigned int clen, char *disk_bitmap)
  {
  	if (ocfs2_resmap_disabled(resmap))
  		return;
  
  	spin_lock(&resv_lock);
  
  	ocfs2_resmap_clear_all_resv(resmap);
  	resmap->m_bitmap_len = clen;
  	resmap->m_disk_bitmap = disk_bitmap;
  
  	spin_unlock(&resv_lock);
  }
  
  void ocfs2_resmap_uninit(struct ocfs2_reservation_map *resmap)
  {
  	/* Does nothing for now. Keep this around for API symmetry */
  }
  
  static void ocfs2_resv_insert(struct ocfs2_reservation_map *resmap,
  			      struct ocfs2_alloc_reservation *new)
  {
  	struct rb_root *root = &resmap->m_reservations;
  	struct rb_node *parent = NULL;
  	struct rb_node **p = &root->rb_node;
  	struct ocfs2_alloc_reservation *tmp;
  
  	assert_spin_locked(&resv_lock);

  	trace_ocfs2_resv_insert(new->r_start, new->r_len);

  
  	while (*p) {
  		parent = *p;
  
  		tmp = rb_entry(parent, struct ocfs2_alloc_reservation, r_node);
  
  		if (new->r_start < tmp->r_start) {
  			p = &(*p)->rb_left;
  
  			/*
  			 * This is a good place to check for
  			 * overlapping reservations.
  			 */
  			BUG_ON(ocfs2_resv_end(new) >= tmp->r_start);
  		} else if (new->r_start > ocfs2_resv_end(tmp)) {
  			p = &(*p)->rb_right;
  		} else {
  			/* This should never happen! */
  			mlog(ML_ERROR, "Duplicate reservation window!
  ");
  			BUG();
  		}
  	}
  
  	rb_link_node(&new->r_node, parent, p);
  	rb_insert_color(&new->r_node, root);
  	new->r_flags |= OCFS2_RESV_FLAG_INUSE;
  
  	ocfs2_resv_mark_lru(resmap, new);
  
  	ocfs2_check_resmap(resmap);
  }
  
  /**
   * ocfs2_find_resv_lhs() - find the window which contains goal
   * @resmap: reservation map to search
   * @goal: which bit to search for
   *
   * If a window containing that goal is not found, we return the window
   * which comes before goal. Returns NULL on empty rbtree or no window
   * before goal.
   */
  static struct ocfs2_alloc_reservation *
  ocfs2_find_resv_lhs(struct ocfs2_reservation_map *resmap, unsigned int goal)
  {
  	struct ocfs2_alloc_reservation *resv = NULL;
  	struct ocfs2_alloc_reservation *prev_resv = NULL;
  	struct rb_node *node = resmap->m_reservations.rb_node;

  
  	assert_spin_locked(&resv_lock);
  
  	if (!node)
  		return NULL;
  
  	node = rb_first(&resmap->m_reservations);
  	while (node) {
  		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
  
  		if (resv->r_start <= goal && ocfs2_resv_end(resv) >= goal)
  			break;
  
  		/* Check if we overshot the reservation just before goal? */
  		if (resv->r_start > goal) {
  			resv = prev_resv;
  			break;
  		}
  
  		prev_resv = resv;

  		node = rb_next(node);
  	}
  
  	return resv;
  }
  
  /*
   * We are given a range within the bitmap, which corresponds to a gap
   * inside the reservations tree (search_start, search_len). The range
   * can be anything from the whole bitmap, to a gap between
   * reservations.
   *
   * The start value of *rstart is insignificant.
   *
   * This function searches the bitmap range starting at search_start

   * with length search_len for a set of contiguous free bits. We try

   * to find up to 'wanted' bits, but can sometimes return less.
   *
   * Returns the length of allocation, 0 if no free bits are found.
   *
   * *cstart and *clen will also be populated with the result.
   */
  static int ocfs2_resmap_find_free_bits(struct ocfs2_reservation_map *resmap,
  				       unsigned int wanted,
  				       unsigned int search_start,
  				       unsigned int search_len,
  				       unsigned int *rstart,
  				       unsigned int *rlen)
  {
  	void *bitmap = resmap->m_disk_bitmap;
  	unsigned int best_start, best_len = 0;
  	int offset, start, found;

  	trace_ocfs2_resmap_find_free_bits_begin(search_start, search_len,
  						wanted, resmap->m_bitmap_len);

  
  	found = best_start = best_len = 0;
  
  	start = search_start;
  	while ((offset = ocfs2_find_next_zero_bit(bitmap, resmap->m_bitmap_len,
  						 start)) != -1) {
  		/* Search reached end of the region */
  		if (offset >= (search_start + search_len))
  			break;
  
  		if (offset == start) {
  			/* we found a zero */
  			found++;
  			/* move start to the next bit to test */
  			start++;
  		} else {
  			/* got a zero after some ones */
  			found = 1;
  			start = offset + 1;
  		}
  		if (found > best_len) {
  			best_len = found;
  			best_start = start - found;
  		}
  
  		if (found >= wanted)
  			break;
  	}
  
  	if (best_len == 0)
  		return 0;
  
  	if (best_len >= wanted)
  		best_len = wanted;
  
  	*rlen = best_len;
  	*rstart = best_start;

  	trace_ocfs2_resmap_find_free_bits_end(best_start, best_len);

  
  	return *rlen;
  }
  
  static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
  				     struct ocfs2_alloc_reservation *resv,
  				     unsigned int goal, unsigned int wanted)
  {
  	struct rb_root *root = &resmap->m_reservations;
  	unsigned int gap_start, gap_end, gap_len;
  	struct ocfs2_alloc_reservation *prev_resv, *next_resv;
  	struct rb_node *prev, *next;
  	unsigned int cstart, clen;
  	unsigned int best_start = 0, best_len = 0;
  
  	/*
  	 * Nasty cases to consider:
  	 *
  	 * - rbtree is empty
  	 * - our window should be first in all reservations
  	 * - our window should be last in all reservations
  	 * - need to make sure we don't go past end of bitmap
  	 */

  	trace_ocfs2_resv_find_window_begin(resv->r_start, ocfs2_resv_end(resv),
  					   goal, wanted, RB_EMPTY_ROOT(root));

  
  	assert_spin_locked(&resv_lock);
  
  	if (RB_EMPTY_ROOT(root)) {
  		/*
  		 * Easiest case - empty tree. We can just take
  		 * whatever window of free bits we want.
  		 */

  		clen = ocfs2_resmap_find_free_bits(resmap, wanted, goal,
  						   resmap->m_bitmap_len - goal,
  						   &cstart, &clen);
  
  		/*
  		 * This should never happen - the local alloc window
  		 * will always have free bits when we're called.
  		 */
  		BUG_ON(goal == 0 && clen == 0);
  
  		if (clen == 0)
  			return;
  
  		resv->r_start = cstart;
  		resv->r_len = clen;
  
  		ocfs2_resv_insert(resmap, resv);
  		return;
  	}
  
  	prev_resv = ocfs2_find_resv_lhs(resmap, goal);
  
  	if (prev_resv == NULL) {

  		/*
  		 * A NULL here means that the search code couldn't
  		 * find a window that starts before goal.
  		 *
  		 * However, we can take the first window after goal,
  		 * which is also by definition, the leftmost window in
  		 * the entire tree. If we can find free bits in the
  		 * gap between goal and the LHS window, then the
  		 * reservation can safely be placed there.
  		 *
  		 * Otherwise we fall back to a linear search, checking
  		 * the gaps in between windows for a place to
  		 * allocate.
  		 */
  
  		next = rb_first(root);
  		next_resv = rb_entry(next, struct ocfs2_alloc_reservation,
  				     r_node);
  
  		/*
  		 * The search should never return such a window. (see
  		 * comment above
  		 */
  		if (next_resv->r_start <= goal) {
  			mlog(ML_ERROR, "goal: %u next_resv: start %u len %u
  ",
  			     goal, next_resv->r_start, next_resv->r_len);
  			ocfs2_dump_resv(resmap);
  			BUG();
  		}
  
  		clen = ocfs2_resmap_find_free_bits(resmap, wanted, goal,
  						   next_resv->r_start - goal,
  						   &cstart, &clen);
  		if (clen) {
  			best_len = clen;
  			best_start = cstart;
  			if (best_len == wanted)
  				goto out_insert;
  		}
  
  		prev_resv = next_resv;
  		next_resv = NULL;
  	}

  	trace_ocfs2_resv_find_window_prev(prev_resv->r_start,
  					  ocfs2_resv_end(prev_resv));

  	prev = &prev_resv->r_node;
  
  	/* Now we do a linear search for a window, starting at 'prev_rsv' */
  	while (1) {
  		next = rb_next(prev);
  		if (next) {

  			next_resv = rb_entry(next,
  					     struct ocfs2_alloc_reservation,
  					     r_node);
  
  			gap_start = ocfs2_resv_end(prev_resv) + 1;
  			gap_end = next_resv->r_start - 1;
  			gap_len = gap_end - gap_start + 1;
  		} else {

  			/*
  			 * We're at the rightmost edge of the
  			 * tree. See if a reservation between this
  			 * window and the end of the bitmap will work.
  			 */
  			gap_start = ocfs2_resv_end(prev_resv) + 1;
  			gap_len = resmap->m_bitmap_len - gap_start;
  			gap_end = resmap->m_bitmap_len - 1;
  		}

  		trace_ocfs2_resv_find_window_next(next ? next_resv->r_start: -1,
  					next ? ocfs2_resv_end(next_resv) : -1);

  		/*
  		 * No need to check this gap if we have already found
  		 * a larger region of free bits.
  		 */
  		if (gap_len <= best_len)
  			goto next_resv;
  
  		clen = ocfs2_resmap_find_free_bits(resmap, wanted, gap_start,
  						   gap_len, &cstart, &clen);
  		if (clen == wanted) {
  			best_len = clen;
  			best_start = cstart;
  			goto out_insert;
  		} else if (clen > best_len) {
  			best_len = clen;
  			best_start = cstart;
  		}
  
  next_resv:
  		if (!next)
  			break;
  
  		prev = next;
  		prev_resv = rb_entry(prev, struct ocfs2_alloc_reservation,
  				     r_node);
  	}
  
  out_insert:
  	if (best_len) {
  		resv->r_start = best_start;
  		resv->r_len = best_len;
  		ocfs2_resv_insert(resmap, resv);
  	}
  }
  
  static void ocfs2_cannibalize_resv(struct ocfs2_reservation_map *resmap,
  				   struct ocfs2_alloc_reservation *resv,
  				   unsigned int wanted)
  {
  	struct ocfs2_alloc_reservation *lru_resv;
  	int tmpwindow = !!(resv->r_flags & OCFS2_RESV_FLAG_TMP);
  	unsigned int min_bits;
  
  	if (!tmpwindow)
  		min_bits = ocfs2_resv_window_bits(resmap, resv) >> 1;
  	else
  		min_bits = wanted; /* We at know the temp window will use all
  				    * of these bits */
  
  	/*
  	 * Take the first reservation off the LRU as our 'target'. We
  	 * don't try to be smart about it. There might be a case for
  	 * searching based on size but I don't have enough data to be
  	 * sure. --Mark (3/16/2010)
  	 */
  	lru_resv = list_first_entry(&resmap->m_lru,
  				    struct ocfs2_alloc_reservation, r_lru);

  	trace_ocfs2_cannibalize_resv_begin(lru_resv->r_start,
  					   lru_resv->r_len,
  					   ocfs2_resv_end(lru_resv));

  
  	/*
  	 * Cannibalize (some or all) of the target reservation and
  	 * feed it to the current window.
  	 */
  	if (lru_resv->r_len <= min_bits) {
  		/*
  		 * Discard completely if size is less than or equal to a
  		 * reasonable threshold - 50% of window bits for non temporary
  		 * windows.
  		 */
  		resv->r_start = lru_resv->r_start;
  		resv->r_len = lru_resv->r_len;
  
  		__ocfs2_resv_discard(resmap, lru_resv);
  	} else {
  		unsigned int shrink;
  		if (tmpwindow)
  			shrink = min_bits;
  		else
  			shrink = lru_resv->r_len / 2;
  
  		lru_resv->r_len -= shrink;
  
  		resv->r_start = ocfs2_resv_end(lru_resv) + 1;
  		resv->r_len = shrink;
  	}

  	trace_ocfs2_cannibalize_resv_end(resv->r_start, ocfs2_resv_end(resv),
  					 resv->r_len, resv->r_last_start,
  					 resv->r_last_len);

  
  	ocfs2_resv_insert(resmap, resv);
  }
  
  static void ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
  				   struct ocfs2_alloc_reservation *resv,
  				   unsigned int wanted)
  {
  	unsigned int goal = 0;
  
  	BUG_ON(!ocfs2_resv_empty(resv));
  
  	/*
  	 * Begin by trying to get a window as close to the previous
  	 * one as possible. Using the most recent allocation as a
  	 * start goal makes sense.
  	 */
  	if (resv->r_last_len) {
  		goal = resv->r_last_start + resv->r_last_len;
  		if (goal >= resmap->m_bitmap_len)
  			goal = 0;
  	}
  
  	__ocfs2_resv_find_window(resmap, resv, goal, wanted);
  
  	/* Search from last alloc didn't work, try once more from beginning. */
  	if (ocfs2_resv_empty(resv) && goal != 0)
  		__ocfs2_resv_find_window(resmap, resv, 0, wanted);
  
  	if (ocfs2_resv_empty(resv)) {
  		/*
  		 * Still empty? Pull oldest one off the LRU, remove it from
  		 * tree, put this one in it's place.
  		 */
  		ocfs2_cannibalize_resv(resmap, resv, wanted);
  	}
  
  	BUG_ON(ocfs2_resv_empty(resv));
  }
  
  int ocfs2_resmap_resv_bits(struct ocfs2_reservation_map *resmap,
  			   struct ocfs2_alloc_reservation *resv,
  			   int *cstart, int *clen)
  {

  	if (resv == NULL || ocfs2_resmap_disabled(resmap))
  		return -ENOSPC;
  
  	spin_lock(&resv_lock);

  	if (ocfs2_resv_empty(resv)) {

  		/*
  		 * We don't want to over-allocate for temporary
  		 * windows. Otherwise, we run the risk of fragmenting the
  		 * allocation space.
  		 */
  		unsigned int wanted = ocfs2_resv_window_bits(resmap, resv);

  		if ((resv->r_flags & OCFS2_RESV_FLAG_TMP) || wanted < *clen)
  			wanted = *clen;

  		/*
  		 * Try to get a window here. If it works, we must fall
  		 * through and test the bitmap . This avoids some
  		 * ping-ponging of windows due to non-reserved space
  		 * being allocation before we initialize a window for
  		 * that inode.
  		 */
  		ocfs2_resv_find_window(resmap, resv, wanted);

  		trace_ocfs2_resmap_resv_bits(resv->r_start, resv->r_len);

  	}
  
  	BUG_ON(ocfs2_resv_empty(resv));
  
  	*cstart = resv->r_start;
  	*clen = resv->r_len;
  
  	spin_unlock(&resv_lock);
  	return 0;
  }
  
  static void
  	ocfs2_adjust_resv_from_alloc(struct ocfs2_reservation_map *resmap,
  				     struct ocfs2_alloc_reservation *resv,
  				     unsigned int start, unsigned int end)
  {

  	unsigned int rhs = 0;
  	unsigned int old_end = ocfs2_resv_end(resv);

  	BUG_ON(start != resv->r_start || old_end < end);

  
  	/*
  	 * Completely used? We can remove it then.
  	 */

  	if (old_end == end) {

  		__ocfs2_resv_discard(resmap, resv);
  		return;
  	}

  	rhs = old_end - end;

  
  	/*

  	 * This should have been trapped above.

  	 */

  	BUG_ON(rhs == 0);

  	resv->r_start = end + 1;
  	resv->r_len = old_end - resv->r_start + 1;

  }
  
  void ocfs2_resmap_claimed_bits(struct ocfs2_reservation_map *resmap,
  			       struct ocfs2_alloc_reservation *resv,
  			       u32 cstart, u32 clen)
  {
  	unsigned int cend = cstart + clen - 1;
  
  	if (resmap == NULL || ocfs2_resmap_disabled(resmap))
  		return;
  
  	if (resv == NULL)
  		return;

  	BUG_ON(cstart != resv->r_start);

  	spin_lock(&resv_lock);

  	trace_ocfs2_resmap_claimed_bits_begin(cstart, cend, clen, resv->r_start,
  					      ocfs2_resv_end(resv), resv->r_len,
  					      resv->r_last_start,
  					      resv->r_last_len);

  
  	BUG_ON(cstart < resv->r_start);
  	BUG_ON(cstart > ocfs2_resv_end(resv));
  	BUG_ON(cend > ocfs2_resv_end(resv));
  
  	ocfs2_adjust_resv_from_alloc(resmap, resv, cstart, cend);
  	resv->r_last_start = cstart;
  	resv->r_last_len = clen;
  
  	/*
  	 * May have been discarded above from
  	 * ocfs2_adjust_resv_from_alloc().
  	 */
  	if (!ocfs2_resv_empty(resv))
  		ocfs2_resv_mark_lru(resmap, resv);

  	trace_ocfs2_resmap_claimed_bits_end(resv->r_start, ocfs2_resv_end(resv),
  					    resv->r_len, resv->r_last_start,
  					    resv->r_last_len);

  
  	ocfs2_check_resmap(resmap);
  
  	spin_unlock(&resv_lock);
  }