/* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * localalloc.c
   *
   * Node local data allocation
   *
   * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
   *
   * This program 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 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; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   */
  
  #include <linux/fs.h>
  #include <linux/types.h>
  #include <linux/slab.h>
  #include <linux/highmem.h>
  #include <linux/bitops.h>
  
  #define MLOG_MASK_PREFIX ML_DISK_ALLOC
  #include <cluster/masklog.h>
  
  #include "ocfs2.h"
  
  #include "alloc.h"
  #include "dlmglue.h"
  #include "inode.h"
  #include "journal.h"
  #include "localalloc.h"
  #include "suballoc.h"
  #include "super.h"
  #include "sysfile.h"
  
  #include "buffer_head_io.h"
  
  #define OCFS2_LOCAL_ALLOC(dinode)	(&((dinode)->id2.i_lab))
  
  static inline int ocfs2_local_alloc_window_bits(struct ocfs2_super *osb);
  
  static u32 ocfs2_local_alloc_count_bits(struct ocfs2_dinode *alloc);
  
  static int ocfs2_local_alloc_find_clear_bits(struct ocfs2_super *osb,
  					     struct ocfs2_dinode *alloc,
  					     u32 numbits);
  
  static void ocfs2_clear_local_alloc(struct ocfs2_dinode *alloc);
  
  static int ocfs2_sync_local_to_main(struct ocfs2_super *osb,

  				    handle_t *handle,

  				    struct ocfs2_dinode *alloc,
  				    struct inode *main_bm_inode,
  				    struct buffer_head *main_bm_bh);
  
  static int ocfs2_local_alloc_reserve_for_window(struct ocfs2_super *osb,

  						struct ocfs2_alloc_context **ac,
  						struct inode **bitmap_inode,
  						struct buffer_head **bitmap_bh);
  
  static int ocfs2_local_alloc_new_window(struct ocfs2_super *osb,

  					handle_t *handle,

  					struct ocfs2_alloc_context *ac);
  
  static int ocfs2_local_alloc_slide_window(struct ocfs2_super *osb,
  					  struct inode *local_alloc_inode);
  
  /*
   * Determine how large our local alloc window should be, in bits.
   *
   * These values (and the behavior in ocfs2_alloc_should_use_local) have
   * been chosen so that most allocations, including new block groups go
   * through local alloc.
   */
  static inline int ocfs2_local_alloc_window_bits(struct ocfs2_super *osb)
  {
  	BUG_ON(osb->s_clustersize_bits < 12);
  
  	return 2048 >> (osb->s_clustersize_bits - 12);
  }
  
  /*
   * Tell us whether a given allocation should use the local alloc
   * file. Otherwise, it has to go to the main bitmap.
   */
  int ocfs2_alloc_should_use_local(struct ocfs2_super *osb, u64 bits)
  {
  	int la_bits = ocfs2_local_alloc_window_bits(osb);
  
  	if (osb->local_alloc_state != OCFS2_LA_ENABLED)
  		return 0;
  
  	/* la_bits should be at least twice the size (in clusters) of
  	 * a new block group. We want to be sure block group
  	 * allocations go through the local alloc, so allow an
  	 * allocation to take up to half the bitmap. */
  	if (bits > (la_bits / 2))
  		return 0;
  
  	return 1;
  }
  
  int ocfs2_load_local_alloc(struct ocfs2_super *osb)
  {
  	int status = 0;
  	struct ocfs2_dinode *alloc = NULL;
  	struct buffer_head *alloc_bh = NULL;
  	u32 num_used;
  	struct inode *inode = NULL;
  	struct ocfs2_local_alloc *la;
  
  	mlog_entry_void();
  
  	/* read the alloc off disk */
  	inode = ocfs2_get_system_file_inode(osb, LOCAL_ALLOC_SYSTEM_INODE,
  					    osb->slot_num);
  	if (!inode) {
  		status = -EINVAL;
  		mlog_errno(status);
  		goto bail;
  	}
  
  	status = ocfs2_read_block(osb, OCFS2_I(inode)->ip_blkno,
  				  &alloc_bh, 0, inode);
  	if (status < 0) {
  		mlog_errno(status);
  		goto bail;
  	}
  
  	alloc = (struct ocfs2_dinode *) alloc_bh->b_data;
  	la = OCFS2_LOCAL_ALLOC(alloc);
  
  	if (!(le32_to_cpu(alloc->i_flags) &
  	    (OCFS2_LOCAL_ALLOC_FL|OCFS2_BITMAP_FL))) {

  		mlog(ML_ERROR, "Invalid local alloc inode, %llu
  ",
  		     (unsigned long long)OCFS2_I(inode)->ip_blkno);

  		status = -EINVAL;
  		goto bail;
  	}
  
  	if ((la->la_size == 0) ||
  	    (le16_to_cpu(la->la_size) > ocfs2_local_alloc_size(inode->i_sb))) {
  		mlog(ML_ERROR, "Local alloc size is invalid (la_size = %u)
  ",
  		     le16_to_cpu(la->la_size));
  		status = -EINVAL;
  		goto bail;
  	}
  
  	/* do a little verification. */
  	num_used = ocfs2_local_alloc_count_bits(alloc);
  
  	/* hopefully the local alloc has always been recovered before
  	 * we load it. */
  	if (num_used
  	    || alloc->id1.bitmap1.i_used
  	    || alloc->id1.bitmap1.i_total
  	    || la->la_bm_off)
  		mlog(ML_ERROR, "Local alloc hasn't been recovered!
  "
  		     "found = %u, set = %u, taken = %u, off = %u
  ",
  		     num_used, le32_to_cpu(alloc->id1.bitmap1.i_used),
  		     le32_to_cpu(alloc->id1.bitmap1.i_total),
  		     OCFS2_LOCAL_ALLOC(alloc)->la_bm_off);
  
  	osb->local_alloc_bh = alloc_bh;
  	osb->local_alloc_state = OCFS2_LA_ENABLED;
  
  bail:
  	if (status < 0)
  		if (alloc_bh)
  			brelse(alloc_bh);
  	if (inode)
  		iput(inode);
  
  	mlog_exit(status);
  	return status;
  }
  
  /*
   * return any unused bits to the bitmap and write out a clean
   * local_alloc.
   *
   * local_alloc_bh is optional. If not passed, we will simply use the
   * one off osb. If you do pass it however, be warned that it *will* be
   * returned brelse'd and NULL'd out.*/
  void ocfs2_shutdown_local_alloc(struct ocfs2_super *osb)
  {
  	int status;

  	handle_t *handle;

  	struct inode *local_alloc_inode = NULL;
  	struct buffer_head *bh = NULL;
  	struct buffer_head *main_bm_bh = NULL;
  	struct inode *main_bm_inode = NULL;
  	struct ocfs2_dinode *alloc_copy = NULL;
  	struct ocfs2_dinode *alloc = NULL;
  
  	mlog_entry_void();
  
  	if (osb->local_alloc_state == OCFS2_LA_UNUSED)

  		goto out;

  
  	local_alloc_inode =
  		ocfs2_get_system_file_inode(osb,
  					    LOCAL_ALLOC_SYSTEM_INODE,
  					    osb->slot_num);
  	if (!local_alloc_inode) {
  		status = -ENOENT;
  		mlog_errno(status);

  		goto out;

  	}
  
  	osb->local_alloc_state = OCFS2_LA_DISABLED;

  	main_bm_inode = ocfs2_get_system_file_inode(osb,
  						    GLOBAL_BITMAP_SYSTEM_INODE,
  						    OCFS2_INVALID_SLOT);
  	if (!main_bm_inode) {
  		status = -EINVAL;
  		mlog_errno(status);

  		goto out;

  	}

  	mutex_lock(&main_bm_inode->i_mutex);

  	status = ocfs2_meta_lock(main_bm_inode, &main_bm_bh, 1);

  	if (status < 0) {
  		mlog_errno(status);

  		goto out_mutex;

  	}
  
  	/* WINDOW_MOVE_CREDITS is a bit heavy... */

  	handle = ocfs2_start_trans(osb, OCFS2_WINDOW_MOVE_CREDITS);

  	if (IS_ERR(handle)) {
  		mlog_errno(PTR_ERR(handle));
  		handle = NULL;

  		goto out_unlock;

  	}
  
  	bh = osb->local_alloc_bh;
  	alloc = (struct ocfs2_dinode *) bh->b_data;
  
  	alloc_copy = kmalloc(bh->b_size, GFP_KERNEL);
  	if (!alloc_copy) {
  		status = -ENOMEM;

  		goto out_commit;

  	}
  	memcpy(alloc_copy, alloc, bh->b_size);
  
  	status = ocfs2_journal_access(handle, local_alloc_inode, bh,
  				      OCFS2_JOURNAL_ACCESS_WRITE);
  	if (status < 0) {
  		mlog_errno(status);

  		goto out_commit;

  	}
  
  	ocfs2_clear_local_alloc(alloc);
  
  	status = ocfs2_journal_dirty(handle, bh);
  	if (status < 0) {
  		mlog_errno(status);

  		goto out_commit;

  	}
  
  	brelse(bh);
  	osb->local_alloc_bh = NULL;
  	osb->local_alloc_state = OCFS2_LA_UNUSED;
  
  	status = ocfs2_sync_local_to_main(osb, handle, alloc_copy,
  					  main_bm_inode, main_bm_bh);
  	if (status < 0)
  		mlog_errno(status);

  out_commit:

  	ocfs2_commit_trans(osb, handle);

  out_unlock:

  	if (main_bm_bh)
  		brelse(main_bm_bh);

  	ocfs2_meta_unlock(main_bm_inode, 1);

  out_mutex:
  	mutex_unlock(&main_bm_inode->i_mutex);
  	iput(main_bm_inode);
  
  out:

  	if (local_alloc_inode)
  		iput(local_alloc_inode);
  
  	if (alloc_copy)
  		kfree(alloc_copy);
  
  	mlog_exit_void();
  }
  
  /*
   * We want to free the bitmap bits outside of any recovery context as
   * we'll need a cluster lock to do so, but we must clear the local
   * alloc before giving up the recovered nodes journal. To solve this,
   * we kmalloc a copy of the local alloc before it's change for the
   * caller to process with ocfs2_complete_local_alloc_recovery
   */
  int ocfs2_begin_local_alloc_recovery(struct ocfs2_super *osb,
  				     int slot_num,
  				     struct ocfs2_dinode **alloc_copy)
  {
  	int status = 0;
  	struct buffer_head *alloc_bh = NULL;
  	struct inode *inode = NULL;
  	struct ocfs2_dinode *alloc;
  
  	mlog_entry("(slot_num = %d)
  ", slot_num);
  
  	*alloc_copy = NULL;
  
  	inode = ocfs2_get_system_file_inode(osb,
  					    LOCAL_ALLOC_SYSTEM_INODE,
  					    slot_num);
  	if (!inode) {
  		status = -EINVAL;
  		mlog_errno(status);
  		goto bail;
  	}

  	mutex_lock(&inode->i_mutex);

  
  	status = ocfs2_read_block(osb, OCFS2_I(inode)->ip_blkno,
  				  &alloc_bh, 0, inode);
  	if (status < 0) {
  		mlog_errno(status);
  		goto bail;
  	}
  
  	*alloc_copy = kmalloc(alloc_bh->b_size, GFP_KERNEL);
  	if (!(*alloc_copy)) {
  		status = -ENOMEM;
  		goto bail;
  	}
  	memcpy((*alloc_copy), alloc_bh->b_data, alloc_bh->b_size);
  
  	alloc = (struct ocfs2_dinode *) alloc_bh->b_data;
  	ocfs2_clear_local_alloc(alloc);
  
  	status = ocfs2_write_block(osb, alloc_bh, inode);
  	if (status < 0)
  		mlog_errno(status);
  
  bail:
  	if ((status < 0) && (*alloc_copy)) {
  		kfree(*alloc_copy);
  		*alloc_copy = NULL;
  	}
  
  	if (alloc_bh)
  		brelse(alloc_bh);
  
  	if (inode) {

  		mutex_unlock(&inode->i_mutex);

  		iput(inode);
  	}
  
  	mlog_exit(status);
  	return status;
  }
  
  /*
   * Step 2: By now, we've completed the journal recovery, we've stamped
   * a clean local alloc on disk and dropped the node out of the
   * recovery map. Dlm locks will no longer stall, so lets clear out the
   * main bitmap.
   */
  int ocfs2_complete_local_alloc_recovery(struct ocfs2_super *osb,
  					struct ocfs2_dinode *alloc)
  {
  	int status;

  	handle_t *handle;

  	struct buffer_head *main_bm_bh = NULL;

  	struct inode *main_bm_inode;

  
  	mlog_entry_void();

  	main_bm_inode = ocfs2_get_system_file_inode(osb,
  						    GLOBAL_BITMAP_SYSTEM_INODE,
  						    OCFS2_INVALID_SLOT);
  	if (!main_bm_inode) {
  		status = -EINVAL;
  		mlog_errno(status);

  		goto out;

  	}

  	mutex_lock(&main_bm_inode->i_mutex);

  	status = ocfs2_meta_lock(main_bm_inode, &main_bm_bh, 1);

  	if (status < 0) {
  		mlog_errno(status);

  		goto out_mutex;

  	}

  	handle = ocfs2_start_trans(osb, OCFS2_WINDOW_MOVE_CREDITS);

  	if (IS_ERR(handle)) {
  		status = PTR_ERR(handle);
  		handle = NULL;
  		mlog_errno(status);

  		goto out_unlock;

  	}
  
  	/* we want the bitmap change to be recorded on disk asap */

  	handle->h_sync = 1;

  
  	status = ocfs2_sync_local_to_main(osb, handle, alloc,
  					  main_bm_inode, main_bm_bh);
  	if (status < 0)
  		mlog_errno(status);

  	ocfs2_commit_trans(osb, handle);

  
  out_unlock:
  	ocfs2_meta_unlock(main_bm_inode, 1);
  
  out_mutex:
  	mutex_unlock(&main_bm_inode->i_mutex);

  
  	if (main_bm_bh)
  		brelse(main_bm_bh);

  	iput(main_bm_inode);

  out:

  	mlog_exit(status);
  	return status;
  }
  
  /*
   * make sure we've got at least bitswanted contiguous bits in the

   * local alloc. You lose them when you drop i_mutex.

   *
   * We will add ourselves to the transaction passed in, but may start
   * our own in order to shift windows.
   */
  int ocfs2_reserve_local_alloc_bits(struct ocfs2_super *osb,

  				   u32 bits_wanted,
  				   struct ocfs2_alloc_context *ac)
  {
  	int status;
  	struct ocfs2_dinode *alloc;
  	struct inode *local_alloc_inode;
  	unsigned int free_bits;
  
  	mlog_entry_void();

  	BUG_ON(!ac);

  
  	local_alloc_inode =
  		ocfs2_get_system_file_inode(osb,
  					    LOCAL_ALLOC_SYSTEM_INODE,
  					    osb->slot_num);
  	if (!local_alloc_inode) {
  		status = -ENOENT;
  		mlog_errno(status);
  		goto bail;
  	}

  
  	mutex_lock(&local_alloc_inode->i_mutex);

  	if (osb->local_alloc_state != OCFS2_LA_ENABLED) {
  		status = -ENOSPC;
  		goto bail;
  	}
  
  	if (bits_wanted > ocfs2_local_alloc_window_bits(osb)) {
  		mlog(0, "Asking for more than my max window size!
  ");
  		status = -ENOSPC;
  		goto bail;
  	}
  
  	alloc = (struct ocfs2_dinode *) osb->local_alloc_bh->b_data;
  
  	if (le32_to_cpu(alloc->id1.bitmap1.i_used) !=
  	    ocfs2_local_alloc_count_bits(alloc)) {

  		ocfs2_error(osb->sb, "local alloc inode %llu says it has "

  			    "%u free bits, but a count shows %u",

  			    (unsigned long long)le64_to_cpu(alloc->i_blkno),

  			    le32_to_cpu(alloc->id1.bitmap1.i_used),
  			    ocfs2_local_alloc_count_bits(alloc));
  		status = -EIO;
  		goto bail;
  	}
  
  	free_bits = le32_to_cpu(alloc->id1.bitmap1.i_total) -
  		le32_to_cpu(alloc->id1.bitmap1.i_used);
  	if (bits_wanted > free_bits) {
  		/* uhoh, window change time. */
  		status =
  			ocfs2_local_alloc_slide_window(osb, local_alloc_inode);
  		if (status < 0) {
  			if (status != -ENOSPC)
  				mlog_errno(status);
  			goto bail;
  		}
  	}

  	ac->ac_inode = local_alloc_inode;
  	ac->ac_which = OCFS2_AC_USE_LOCAL;

  	get_bh(osb->local_alloc_bh);
  	ac->ac_bh = osb->local_alloc_bh;

  	status = 0;
  bail:

  	if (status < 0 && local_alloc_inode)
  		iput(local_alloc_inode);

  
  	mlog_exit(status);
  	return status;
  }
  
  int ocfs2_claim_local_alloc_bits(struct ocfs2_super *osb,

  				 handle_t *handle,

  				 struct ocfs2_alloc_context *ac,
  				 u32 min_bits,
  				 u32 *bit_off,
  				 u32 *num_bits)
  {
  	int status, start;
  	struct inode *local_alloc_inode;
  	u32 bits_wanted;
  	void *bitmap;
  	struct ocfs2_dinode *alloc;
  	struct ocfs2_local_alloc *la;
  
  	mlog_entry_void();
  	BUG_ON(ac->ac_which != OCFS2_AC_USE_LOCAL);
  
  	bits_wanted = ac->ac_bits_wanted - ac->ac_bits_given;
  	local_alloc_inode = ac->ac_inode;
  	alloc = (struct ocfs2_dinode *) osb->local_alloc_bh->b_data;
  	la = OCFS2_LOCAL_ALLOC(alloc);
  
  	start = ocfs2_local_alloc_find_clear_bits(osb, alloc, bits_wanted);
  	if (start == -1) {
  		/* TODO: Shouldn't we just BUG here? */
  		status = -ENOSPC;
  		mlog_errno(status);
  		goto bail;
  	}
  
  	bitmap = la->la_bitmap;
  	*bit_off = le32_to_cpu(la->la_bm_off) + start;
  	/* local alloc is always contiguous by nature -- we never
  	 * delete bits from it! */
  	*num_bits = bits_wanted;
  
  	status = ocfs2_journal_access(handle, local_alloc_inode,
  				      osb->local_alloc_bh,
  				      OCFS2_JOURNAL_ACCESS_WRITE);
  	if (status < 0) {
  		mlog_errno(status);
  		goto bail;
  	}
  
  	while(bits_wanted--)
  		ocfs2_set_bit(start++, bitmap);
  
  	alloc->id1.bitmap1.i_used = cpu_to_le32(*num_bits +
  				le32_to_cpu(alloc->id1.bitmap1.i_used));
  
  	status = ocfs2_journal_dirty(handle, osb->local_alloc_bh);
  	if (status < 0) {
  		mlog_errno(status);
  		goto bail;
  	}
  
  	status = 0;
  bail:
  	mlog_exit(status);
  	return status;
  }
  
  static u32 ocfs2_local_alloc_count_bits(struct ocfs2_dinode *alloc)
  {
  	int i;
  	u8 *buffer;
  	u32 count = 0;
  	struct ocfs2_local_alloc *la = OCFS2_LOCAL_ALLOC(alloc);
  
  	mlog_entry_void();
  
  	buffer = la->la_bitmap;
  	for (i = 0; i < le16_to_cpu(la->la_size); i++)
  		count += hweight8(buffer[i]);
  
  	mlog_exit(count);
  	return count;
  }
  
  static int ocfs2_local_alloc_find_clear_bits(struct ocfs2_super *osb,
  					     struct ocfs2_dinode *alloc,
  					     u32 numbits)
  {
  	int numfound, bitoff, left, startoff, lastzero;
  	void *bitmap = NULL;
  
  	mlog_entry("(numbits wanted = %u)
  ", numbits);
  
  	if (!alloc->id1.bitmap1.i_total) {
  		mlog(0, "No bits in my window!
  ");
  		bitoff = -1;
  		goto bail;
  	}
  
  	bitmap = OCFS2_LOCAL_ALLOC(alloc)->la_bitmap;
  
  	numfound = bitoff = startoff = 0;
  	lastzero = -1;
  	left = le32_to_cpu(alloc->id1.bitmap1.i_total);
  	while ((bitoff = ocfs2_find_next_zero_bit(bitmap, left, startoff)) != -1) {
  		if (bitoff == left) {
  			/* mlog(0, "bitoff (%d) == left", bitoff); */
  			break;
  		}
  		/* mlog(0, "Found a zero: bitoff = %d, startoff = %d, "
  		   "numfound = %d
  ", bitoff, startoff, numfound);*/
  
  		/* Ok, we found a zero bit... is it contig. or do we
  		 * start over?*/
  		if (bitoff == startoff) {
  			/* we found a zero */
  			numfound++;
  			startoff++;
  		} else {
  			/* got a zero after some ones */
  			numfound = 1;
  			startoff = bitoff+1;
  		}
  		/* we got everything we needed */
  		if (numfound == numbits) {
  			/* mlog(0, "Found it all!
  "); */
  			break;
  		}
  	}
  
  	mlog(0, "Exiting loop, bitoff = %d, numfound = %d
  ", bitoff,
  	     numfound);
  
  	if (numfound == numbits)
  		bitoff = startoff - numfound;
  	else
  		bitoff = -1;
  
  bail:
  	mlog_exit(bitoff);
  	return bitoff;
  }
  
  static void ocfs2_clear_local_alloc(struct ocfs2_dinode *alloc)
  {
  	struct ocfs2_local_alloc *la = OCFS2_LOCAL_ALLOC(alloc);
  	int i;
  	mlog_entry_void();
  
  	alloc->id1.bitmap1.i_total = 0;
  	alloc->id1.bitmap1.i_used = 0;
  	la->la_bm_off = 0;
  	for(i = 0; i < le16_to_cpu(la->la_size); i++)
  		la->la_bitmap[i] = 0;
  
  	mlog_exit_void();
  }
  
  #if 0
  /* turn this on and uncomment below to aid debugging window shifts. */
  static void ocfs2_verify_zero_bits(unsigned long *bitmap,
  				   unsigned int start,
  				   unsigned int count)
  {
  	unsigned int tmp = count;
  	while(tmp--) {
  		if (ocfs2_test_bit(start + tmp, bitmap)) {
  			printk("ocfs2_verify_zero_bits: start = %u, count = "
  			       "%u
  ", start, count);
  			printk("ocfs2_verify_zero_bits: bit %u is set!",
  			       start + tmp);
  			BUG();
  		}
  	}
  }
  #endif
  
  /*
   * sync the local alloc to main bitmap.
   *
   * assumes you've already locked the main bitmap -- the bitmap inode
   * passed is used for caching.
   */
  static int ocfs2_sync_local_to_main(struct ocfs2_super *osb,

  				    handle_t *handle,

  				    struct ocfs2_dinode *alloc,
  				    struct inode *main_bm_inode,
  				    struct buffer_head *main_bm_bh)
  {
  	int status = 0;
  	int bit_off, left, count, start;
  	u64 la_start_blk;
  	u64 blkno;
  	void *bitmap;
  	struct ocfs2_local_alloc *la = OCFS2_LOCAL_ALLOC(alloc);
  
  	mlog_entry("total = %u, COUNT = %u, used = %u
  ",
  		   le32_to_cpu(alloc->id1.bitmap1.i_total),
  		   ocfs2_local_alloc_count_bits(alloc),
  		   le32_to_cpu(alloc->id1.bitmap1.i_used));
  
  	if (!alloc->id1.bitmap1.i_total) {
  		mlog(0, "nothing to sync!
  ");
  		goto bail;
  	}
  
  	if (le32_to_cpu(alloc->id1.bitmap1.i_used) ==
  	    le32_to_cpu(alloc->id1.bitmap1.i_total)) {
  		mlog(0, "all bits were taken!
  ");
  		goto bail;
  	}
  
  	la_start_blk = ocfs2_clusters_to_blocks(osb->sb,
  						le32_to_cpu(la->la_bm_off));
  	bitmap = la->la_bitmap;
  	start = count = bit_off = 0;
  	left = le32_to_cpu(alloc->id1.bitmap1.i_total);
  
  	while ((bit_off = ocfs2_find_next_zero_bit(bitmap, left, start))
  	       != -1) {
  		if ((bit_off < left) && (bit_off == start)) {
  			count++;
  			start++;
  			continue;
  		}
  		if (count) {
  			blkno = la_start_blk +
  				ocfs2_clusters_to_blocks(osb->sb,
  							 start - count);

  			mlog(0, "freeing %u bits starting at local alloc bit "
  			     "%u (la_start_blk = %llu, blkno = %llu)
  ",
  			     count, start - count,
  			     (unsigned long long)la_start_blk,
  			     (unsigned long long)blkno);

  
  			status = ocfs2_free_clusters(handle, main_bm_inode,
  						     main_bm_bh, blkno, count);
  			if (status < 0) {
  				mlog_errno(status);
  				goto bail;
  			}
  		}
  		if (bit_off >= left)
  			break;
  		count = 1;
  		start = bit_off + 1;
  	}
  
  bail:
  	mlog_exit(status);
  	return status;
  }
  
  static int ocfs2_local_alloc_reserve_for_window(struct ocfs2_super *osb,

  						struct ocfs2_alloc_context **ac,
  						struct inode **bitmap_inode,
  						struct buffer_head **bitmap_bh)
  {
  	int status;

  	*ac = kzalloc(sizeof(struct ocfs2_alloc_context), GFP_KERNEL);

  	if (!(*ac)) {
  		status = -ENOMEM;
  		mlog_errno(status);
  		goto bail;
  	}

  	(*ac)->ac_bits_wanted = ocfs2_local_alloc_window_bits(osb);
  
  	status = ocfs2_reserve_cluster_bitmap_bits(osb, *ac);
  	if (status < 0) {
  		if (status != -ENOSPC)
  			mlog_errno(status);
  		goto bail;
  	}
  
  	*bitmap_inode = (*ac)->ac_inode;
  	igrab(*bitmap_inode);
  	*bitmap_bh = (*ac)->ac_bh;
  	get_bh(*bitmap_bh);
  	status = 0;
  bail:
  	if ((status < 0) && *ac) {
  		ocfs2_free_alloc_context(*ac);
  		*ac = NULL;
  	}
  
  	mlog_exit(status);
  	return status;
  }
  
  /*
   * pass it the bitmap lock in lock_bh if you have it.
   */
  static int ocfs2_local_alloc_new_window(struct ocfs2_super *osb,

  					handle_t *handle,

  					struct ocfs2_alloc_context *ac)
  {
  	int status = 0;
  	u32 cluster_off, cluster_count;
  	struct ocfs2_dinode *alloc = NULL;
  	struct ocfs2_local_alloc *la;
  
  	mlog_entry_void();
  
  	alloc = (struct ocfs2_dinode *) osb->local_alloc_bh->b_data;
  	la = OCFS2_LOCAL_ALLOC(alloc);
  
  	if (alloc->id1.bitmap1.i_total)
  		mlog(0, "asking me to alloc a new window over a non-empty "
  		     "one
  ");
  
  	mlog(0, "Allocating %u clusters for a new window.
  ",
  	     ocfs2_local_alloc_window_bits(osb));

  
  	/* Instruct the allocation code to try the most recently used
  	 * cluster group. We'll re-record the group used this pass
  	 * below. */
  	ac->ac_last_group = osb->la_last_gd;

  	/* we used the generic suballoc reserve function, but we set
  	 * everything up nicely, so there's no reason why we can't use
  	 * the more specific cluster api to claim bits. */
  	status = ocfs2_claim_clusters(osb, handle, ac,
  				      ocfs2_local_alloc_window_bits(osb),
  				      &cluster_off, &cluster_count);
  	if (status < 0) {
  		if (status != -ENOSPC)
  			mlog_errno(status);
  		goto bail;
  	}

  	osb->la_last_gd = ac->ac_last_group;

  	la->la_bm_off = cpu_to_le32(cluster_off);
  	alloc->id1.bitmap1.i_total = cpu_to_le32(cluster_count);
  	/* just in case... In the future when we find space ourselves,
  	 * we don't have to get all contiguous -- but we'll have to
  	 * set all previously used bits in bitmap and update
  	 * la_bits_set before setting the bits in the main bitmap. */
  	alloc->id1.bitmap1.i_used = 0;
  	memset(OCFS2_LOCAL_ALLOC(alloc)->la_bitmap, 0,
  	       le16_to_cpu(la->la_size));
  
  	mlog(0, "New window allocated:
  ");
  	mlog(0, "window la_bm_off = %u
  ",
  	     OCFS2_LOCAL_ALLOC(alloc)->la_bm_off);
  	mlog(0, "window bits = %u
  ", le32_to_cpu(alloc->id1.bitmap1.i_total));
  
  bail:
  	mlog_exit(status);
  	return status;
  }
  
  /* Note that we do *NOT* lock the local alloc inode here as
   * it's been locked already for us. */
  static int ocfs2_local_alloc_slide_window(struct ocfs2_super *osb,
  					  struct inode *local_alloc_inode)
  {
  	int status = 0;
  	struct buffer_head *main_bm_bh = NULL;
  	struct inode *main_bm_inode = NULL;

  	handle_t *handle = NULL;

  	struct ocfs2_dinode *alloc;
  	struct ocfs2_dinode *alloc_copy = NULL;
  	struct ocfs2_alloc_context *ac = NULL;
  
  	mlog_entry_void();

  	/* This will lock the main bitmap for us. */
  	status = ocfs2_local_alloc_reserve_for_window(osb,

  						      &ac,
  						      &main_bm_inode,
  						      &main_bm_bh);
  	if (status < 0) {
  		if (status != -ENOSPC)
  			mlog_errno(status);
  		goto bail;
  	}

  	handle = ocfs2_start_trans(osb, OCFS2_WINDOW_MOVE_CREDITS);

  	if (IS_ERR(handle)) {
  		status = PTR_ERR(handle);
  		handle = NULL;
  		mlog_errno(status);
  		goto bail;
  	}
  
  	alloc = (struct ocfs2_dinode *) osb->local_alloc_bh->b_data;
  
  	/* We want to clear the local alloc before doing anything
  	 * else, so that if we error later during this operation,
  	 * local alloc shutdown won't try to double free main bitmap
  	 * bits. Make a copy so the sync function knows which bits to
  	 * free. */
  	alloc_copy = kmalloc(osb->local_alloc_bh->b_size, GFP_KERNEL);
  	if (!alloc_copy) {
  		status = -ENOMEM;
  		mlog_errno(status);
  		goto bail;
  	}
  	memcpy(alloc_copy, alloc, osb->local_alloc_bh->b_size);
  
  	status = ocfs2_journal_access(handle, local_alloc_inode,
  				      osb->local_alloc_bh,
  				      OCFS2_JOURNAL_ACCESS_WRITE);
  	if (status < 0) {
  		mlog_errno(status);
  		goto bail;
  	}
  
  	ocfs2_clear_local_alloc(alloc);
  
  	status = ocfs2_journal_dirty(handle, osb->local_alloc_bh);
  	if (status < 0) {
  		mlog_errno(status);
  		goto bail;
  	}
  
  	status = ocfs2_sync_local_to_main(osb, handle, alloc_copy,
  					  main_bm_inode, main_bm_bh);
  	if (status < 0) {
  		mlog_errno(status);
  		goto bail;
  	}
  
  	status = ocfs2_local_alloc_new_window(osb, handle, ac);
  	if (status < 0) {
  		if (status != -ENOSPC)
  			mlog_errno(status);
  		goto bail;
  	}
  
  	atomic_inc(&osb->alloc_stats.moves);
  
  	status = 0;
  bail:
  	if (handle)

  		ocfs2_commit_trans(osb, handle);

  
  	if (main_bm_bh)
  		brelse(main_bm_bh);
  
  	if (main_bm_inode)
  		iput(main_bm_inode);
  
  	if (alloc_copy)
  		kfree(alloc_copy);
  
  	if (ac)
  		ocfs2_free_alloc_context(ac);
  
  	mlog_exit(status);
  	return status;
  }