text: /*-
   *  modified for Lites 1.1
   *
   *  Aug 1995, Godmar Back (gback@cs.utah.edu)
   *  University of Utah, Department of Computer Science
   */
  /*-
   * SPDX-License-Identifier: BSD-3-Clause
   *
   * Copyright (c) 1982, 1986, 1989, 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   *	@(#)ffs_alloc.c	8.8 (Berkeley) 2/21/94
   * $FreeBSD$
   */
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/conf.h>
  #include <sys/vnode.h>
  #include <sys/stat.h>
  #include <sys/mount.h>
  #include <sys/sysctl.h>
  #include <sys/syslog.h>
  #include <sys/buf2.h>
  #include <sys/endian.h>
  #include <sys/malloc.h>
  #include <sys/mutex2.h>
  
  #include <vfs/ext2fs/fs.h>
  #include <vfs/ext2fs/inode.h>
  #include <vfs/ext2fs/ext2_mount.h>
  #include <vfs/ext2fs/ext2fs.h>
  #include <vfs/ext2fs/ext2_extern.h>
  
  SDT_PROVIDER_DEFINE(ext2fs);
  /*
   * ext2fs trace probe:
   * arg0: verbosity. Higher numbers give more verbose messages
   * arg1: Textual message
   */
  SDT_PROBE_DEFINE2(ext2fs, , alloc, trace, "int", "char*");
  SDT_PROBE_DEFINE3(ext2fs, , alloc, ext2_reallocblks_realloc,
      "ino_t", "e2fs_lbn_t", "e2fs_lbn_t");
  SDT_PROBE_DEFINE1(ext2fs, , alloc, ext2_reallocblks_bap, "uint32_t");
  SDT_PROBE_DEFINE1(ext2fs, , alloc, ext2_reallocblks_blkno, "e2fs_daddr_t");
  SDT_PROBE_DEFINE2(ext2fs, , alloc, ext2_b_bitmap_validate_error, "char*", "int");
  SDT_PROBE_DEFINE3(ext2fs, , alloc, ext2_nodealloccg_bmap_corrupted,
      "int", "daddr_t", "char*");
  SDT_PROBE_DEFINE2(ext2fs, , alloc, ext2_blkfree_bad_block, "ino_t", "e4fs_daddr_t");
  SDT_PROBE_DEFINE2(ext2fs, , alloc, ext2_vfree_doublefree, "char*", "ino_t");
  
  static daddr_t	ext2_alloccg(struct inode *, int, daddr_t, int);
  static daddr_t	ext2_clusteralloc(struct inode *, int, daddr_t, int);
  static u_long	ext2_dirpref(struct inode *);
  static e4fs_daddr_t ext2_hashalloc(struct inode *, int, long, int,
      daddr_t (*)(struct inode *, int, daddr_t, 
  						int));
  static daddr_t	ext2_nodealloccg(struct inode *, int, daddr_t, int);
  static daddr_t  ext2_mapsearch(struct m_ext2fs *, char *, daddr_t);
  
  /*
   * Allocate a block in the filesystem.
   *
   * A preference may be optionally specified. If a preference is given
   * the following hierarchy is used to allocate a block:
   *   1) allocate the requested block.
   *   2) allocate a rotationally optimal block in the same cylinder.
   *   3) allocate a block in the same cylinder group.
   *   4) quadratically rehash into other cylinder groups, until an
   *        available block is located.
   * If no block preference is given the following hierarchy is used
   * to allocate a block:
   *   1) allocate a block in the cylinder group that contains the
   *        inode for the file.
   *   2) quadratically rehash into other cylinder groups, until an
   *        available block is located.
   */
  int
  ext2_alloc(struct inode *ip, daddr_t lbn, e4fs_daddr_t bpref, int size,
      struct ucred *cred, e4fs_daddr_t *bnp)
  {
  	struct m_ext2fs *fs;
  	struct ext2mount *ump;
  	e4fs_daddr_t bno;
  	int cg;
  
  	*bnp = 0;
  	fs = ip->i_e2fs;
  	ump = ip->i_ump;
  	mtx_assert(EXT2_MTX(ump), MA_OWNED);
  #ifdef INVARIANTS
  	if ((u_int)size > fs->e2fs_bsize || blkoff(fs, size) != 0) {
  		printf("bsize = %lu, size = %d, fs = %s\n",
  		    (long unsigned int)fs->e2fs_bsize, size, fs->e2fs_fsmnt);
  		panic("ext2_alloc: bad size");
  	}
  	if (cred == NOCRED)
  		panic("ext2_alloc: missing credential");
  #endif		/* INVARIANTS */
  	if (size == fs->e2fs_bsize && fs->e2fs_fbcount == 0)
  		goto nospace;
  	if (cred->cr_uid != 0 &&
  	    fs->e2fs_fbcount < fs->e2fs_rbcount)
  		goto nospace;
  	if (bpref >= fs->e2fs_bcount)
  		bpref = 0;
  	if (bpref == 0)
  		cg = ino_to_cg(fs, ip->i_number);
  	else
  		cg = dtog(fs, bpref);
  	bno = (daddr_t)ext2_hashalloc(ip, cg, bpref, fs->e2fs_bsize,
  	    ext2_alloccg);
  	if (bno > 0) {
  		/* set next_alloc fields as done in block_getblk */
  		ip->i_next_alloc_block = lbn;
  		ip->i_next_alloc_goal = bno;
  
  		ip->i_blocks += btodb(fs->e2fs_bsize);
  		ip->i_flag |= IN_CHANGE | IN_UPDATE;
  		*bnp = bno;
  		return (0);
  	}
  nospace:
  	EXT2_UNLOCK(ump);
  	SDT_PROBE2(ext2fs, , alloc, trace, 1, "cannot allocate data block");
  	return (ENOSPC);
  }
  
  /*
   * Allocate EA's block for inode.
   */
  e4fs_daddr_t
  ext2_alloc_meta(struct inode *ip)
  {
  	struct m_ext2fs *fs;
  	daddr_t blk;
  
  	fs = ip->i_e2fs;
  
  	EXT2_LOCK(ip->i_ump);
  	blk = ext2_hashalloc(ip, ino_to_cg(fs, ip->i_number), 0, fs->e2fs_bsize,
  	    ext2_alloccg);
  	if (0 == blk) {
  		EXT2_UNLOCK(ip->i_ump);
  		SDT_PROBE2(ext2fs, , alloc, trace, 1, "cannot allocate meta block");
  	}
  
  	return (blk);
  }
  
  /*
   * Reallocate a sequence of blocks into a contiguous sequence of blocks.
   *
   * The vnode and an array of buffer pointers for a range of sequential
   * logical blocks to be made contiguous is given. The allocator attempts
   * to find a range of sequential blocks starting as close as possible to
   * an fs_rotdelay offset from the end of the allocation for the logical
   * block immediately preceding the current range. If successful, the
   * physical block numbers in the buffer pointers and in the inode are
   * changed to reflect the new allocation. If unsuccessful, the allocation
   * is left unchanged. The success in doing the reallocation is returned.
   * Note that the error return is not reflected back to the user. Rather
   * the previous block allocation will be used.
   */
  
  static SYSCTL_NODE(_vfs, OID_AUTO, ext2fs, CTLFLAG_RW, 0, "EXT2FS filesystem");
  
  static int doasyncfree = 1;
  
  SYSCTL_INT(_vfs_ext2fs, OID_AUTO, doasyncfree, CTLFLAG_RW, &doasyncfree, 0,
      "Use asynchronous writes to update block pointers when freeing blocks");
  
  static int doreallocblks = 0;
  
  SYSCTL_INT(_vfs_ext2fs, OID_AUTO, doreallocblks, CTLFLAG_RW, &doreallocblks, 0, "");
  
  int
  ext2_reallocblks(struct vop_reallocblks_args *ap)
  {
  	struct m_ext2fs *fs;
  	struct inode *ip;
  	struct vnode *vp;
  	struct buf *sbp, *ebp;
  	uint32_t *bap, *sbap, *ebap;
  	struct ext2mount *ump;
  	struct cluster_save *buflist;
  	struct indir start_ap[EXT2_NIADDR + 1], end_ap[EXT2_NIADDR + 1], *idp;
  	e2fs_lbn_t start_lbn, end_lbn;
  	int soff;
  	e2fs_daddr_t newblk, blkno;
  	int i, len, start_lvl, end_lvl, pref, ssize;
  
  	if (doreallocblks == 0)
  		return (ENOSPC);
  
  	vp = ap->a_vp;
  	ip = VTOI(vp);
  	fs = ip->i_e2fs;
  	ump = ip->i_ump;
  
  	if (fs->e2fs_contigsumsize <= 0 || ip->i_flag & IN_E4EXTENTS)
  		return (ENOSPC);
  
  	buflist = ap->a_buflist;
  	len = buflist->bs_nchildren;
  	start_lbn = lblkno(fs, buflist->bs_children[0]->b_loffset);
  	end_lbn = start_lbn + len - 1;
  #ifdef INVARIANTS
  	for (i = 1; i < len; i++)
  		if (buflist->bs_children[i]->b_loffset != lblktodoff(fs, start_lbn + i))
  			panic("ext2_reallocblks: non-cluster");
  #endif
  	/*
  	 * If the cluster crosses the boundary for the first indirect
  	 * block, leave space for the indirect block. Indirect blocks
  	 * are initially laid out in a position after the last direct
  	 * block. Block reallocation would usually destroy locality by
  	 * moving the indirect block out of the way to make room for
  	 * data blocks if we didn't compensate here. We should also do
  	 * this for other indirect block boundaries, but it is only
  	 * important for the first one.
  	 */
  	if (start_lbn < EXT2_NDADDR && end_lbn >= EXT2_NDADDR)
  		return (ENOSPC);
  	/*
  	 * If the latest allocation is in a new cylinder group, assume that
  	 * the filesystem has decided to move and do not force it back to
  	 * the previous cylinder group.
  	 */
  	if (dtog(fs, dofftofsb(fs, buflist->bs_children[0]->b_bio2.bio_offset)) !=
  	    dtog(fs, dofftofsb(fs, buflist->bs_children[len - 1]->b_bio2.bio_offset)))
  		return (ENOSPC);
  	if (ext2_getlbns(vp, start_lbn, start_ap, &start_lvl) ||
  	    ext2_getlbns(vp, end_lbn, end_ap, &end_lvl))
  		return (ENOSPC);
  	/*
  	 * Get the starting offset and block map for the first block.
  	 */
  	if (start_lvl == 0) {
  		sbap = &ip->i_db[0];
  		soff = start_lbn;
  	} else {
  		idp = &start_ap[start_lvl - 1];
  		if (bread(vp, lblktodoff(fs, idp->in_lbn), (int)fs->e2fs_bsize,
  		    &sbp)) {
  			brelse(sbp);
  			return (ENOSPC);
  		}
  		sbap = (u_int *)sbp->b_data;
  		soff = idp->in_off;
  	}
  	/*
  	 * If the block range spans two block maps, get the second map.
  	 */
  	ebap = NULL;
  	if (end_lvl == 0 || (idp = &end_ap[end_lvl - 1])->in_off + 1 >= len) {
  		ssize = len;
  	} else {
  #ifdef INVARIANTS
  		if (start_ap[start_lvl - 1].in_lbn == idp->in_lbn)
  			panic("ext2_reallocblks: start == end");
  #endif
  		ssize = len - (idp->in_off + 1);
  		if (bread(vp, lblktodoff(fs, idp->in_lbn), (int)fs->e2fs_bsize,
  		    &ebp))
  			goto fail;
  		ebap = (u_int *)ebp->b_data;
  	}
  	/*
  	 * Find the preferred location for the cluster.
  	 */
  	EXT2_LOCK(ump);
  	pref = ext2_blkpref(ip, start_lbn, soff, sbap, 0);
  	/*
  	 * Search the block map looking for an allocation of the desired size.
  	 */
  	if ((newblk = (e2fs_daddr_t)ext2_hashalloc(ip, dtog(fs, pref), pref,
  	    len, ext2_clusteralloc)) == 0) {
  		EXT2_UNLOCK(ump);
  		goto fail;
  	}
  	/*
  	 * We have found a new contiguous block.
  	 *
  	 * First we have to replace the old block pointers with the new
  	 * block pointers in the inode and indirect blocks associated
  	 * with the file.
  	 */
  	SDT_PROBE3(ext2fs, , alloc, ext2_reallocblks_realloc,
  	    ip->i_number, start_lbn, end_lbn);
  	blkno = newblk;
  	for (bap = &sbap[soff], i = 0; i < len; i++, blkno += fs->e2fs_fpb) {
  		if (i == ssize) {
  			bap = ebap;
  			soff = -i;
  		}
  #ifdef INVARIANTS
  		if (buflist->bs_children[i]->b_bio2.bio_offset !=
  		    fsbtodoff(fs, *bap))
  			panic("ext2_reallocblks: alloc mismatch");
  #endif
  		SDT_PROBE1(ext2fs, , alloc, ext2_reallocblks_bap, *bap);
  		*bap++ = blkno;
  	}
  	/*
  	 * Next we must write out the modified inode and indirect blocks.
  	 * For strict correctness, the writes should be synchronous since
  	 * the old block values may have been written to disk. In practise
  	 * they are almost never written, but if we are concerned about
  	 * strict correctness, the `doasyncfree' flag should be set to zero.
  	 *
  	 * The test on `doasyncfree' should be changed to test a flag
  	 * that shows whether the associated buffers and inodes have
  	 * been written. The flag should be set when the cluster is
  	 * started and cleared whenever the buffer or inode is flushed.
  	 * We can then check below to see if it is set, and do the
  	 * synchronous write only when it has been cleared.
  	 */
  	if (sbap != &ip->i_db[0]) {
  		if (doasyncfree)
  			bdwrite(sbp);
  		else
  			bwrite(sbp);
  	} else {
  		ip->i_flag |= IN_CHANGE | IN_UPDATE;
  		if (!doasyncfree)
  			ext2_update(vp, 1);
  	}
  	if (ssize < len) {
  		if (doasyncfree)
  			bdwrite(ebp);
  		else
  			bwrite(ebp);
  	}
  	/*
  	 * Last, free the old blocks and assign the new blocks to the buffers.
  	 */
  	for (blkno = newblk, i = 0; i < len; i++, blkno += fs->e2fs_fpb) {
  		ext2_blkfree(ip, dofftofsb(fs, buflist->bs_children[i]->b_bio2.bio_offset),
  		    fs->e2fs_bsize);
  		buflist->bs_children[i]->b_bio2.bio_offset = fsbtodoff(fs, blkno);
  		SDT_PROBE1(ext2fs, , alloc, ext2_reallocblks_blkno, blkno);
  	}
  
  	return (0);
  
  fail:
  	if (ssize < len)
  		brelse(ebp);
  	if (sbap != &ip->i_db[0])
  		brelse(sbp);
  	return (ENOSPC);
  }
  
  /*
   * Allocate an inode in the filesystem.
   *
   */
  int
  ext2_valloc(struct vnode *pvp, int mode, struct ucred *cred, struct vnode **vpp)
  {
  	struct timespec ts;
  	struct m_ext2fs *fs;
  	struct ext2mount *ump;
  	struct inode *pip;
  	struct inode *ip;
  	struct vnode *vp;
  	ino_t ino, ipref;
  	int error, cg;
  
  	*vpp = NULL;
  	pip = VTOI(pvp);
  	fs = pip->i_e2fs;
  	ump = pip->i_ump;
  
  	EXT2_LOCK(ump);
  	if (fs->e2fs_ficount == 0)
  		goto noinodes;
  	/*
  	 * If it is a directory then obtain a cylinder group based on
  	 * ext2_dirpref else obtain it using ino_to_cg. The preferred inode is
  	 * always the next inode.
  	 */
  	if ((mode & IFMT) == IFDIR) {
  		cg = ext2_dirpref(pip);
  		if (fs->e2fs_contigdirs[cg] < 255)
  			fs->e2fs_contigdirs[cg]++;
  	} else {
  		cg = ino_to_cg(fs, pip->i_number);
  		if (fs->e2fs_contigdirs[cg] > 0)
  			fs->e2fs_contigdirs[cg]--;
  	}
  	ipref = cg * fs->e2fs_ipg + 1;
  	ino = (ino_t)ext2_hashalloc(pip, cg, (long)ipref, mode, ext2_nodealloccg);
  	if (ino == 0)
  		goto noinodes;
  restart:
  	if ((vp = ext2_ihashget(ump->um_dev, ino)) != NULL) {
  		printf("ext2_valloc: vp %p exists for inode %lu\n", vp, ino);
  		return (EEXIST);
  	}
  	if (ext2_alloc_vnode(ump->um_mountp, ino, &vp) == -1)
  		goto restart;
  	ip = VTOI(vp);
  
  	if ((error = ext2_vinit(vp->v_mount, &vp)) != 0) {
  		*vpp = NULL;
  		vp->v_type = VBAD;
  		vx_put(vp);
  		return (error);
  	}
  
  	if (EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_EXTENTS)
  	    && (S_ISREG(mode) || S_ISDIR(mode)))
  		ext4_ext_tree_init(ip);
  	else
  		memset(ip->i_data, 0, sizeof(ip->i_data));
  
  	/*
  	 * Set up a new generation number for this inode.
  	 * Avoid zero values.
  	 */
  	do {
  		ip->i_gen = karc4random();
  	} while (ip->i_gen == 0);
  
  	vfs_timestamp(&ts);
  	ip->i_birthtime = ts.tv_sec;
  	ip->i_birthnsec = ts.tv_nsec;
  
  	/*
  	 * Finish inode initialization now that aliasing has been resolved.
  	 */
  	vref(ip->i_devvp);
  	/*
  	 * Return the locked and refd vnode.
  	 */
  	vx_downgrade(vp);	/* downgrade VX lock to VN lock */
  	*vpp = vp;
  
  	return (0);
  
  noinodes:
  	EXT2_UNLOCK(ump);
  	SDT_PROBE2(ext2fs, , alloc, trace, 1, "out of inodes");
  	return (ENOSPC);
  }
  
  /*
   * 64-bit compatible getters and setters for struct ext2_gd from ext2fs.h
   */
  uint64_t
  e2fs_gd_get_b_bitmap(struct ext2_gd *gd)
  {
  
  	return (((uint64_t)(le32toh(gd->ext4bgd_b_bitmap_hi)) << 32) |
  	    le32toh(gd->ext2bgd_b_bitmap));
  }
  
  uint64_t
  e2fs_gd_get_i_bitmap(struct ext2_gd *gd)
  {
  
  	return (((uint64_t)(le32toh(gd->ext4bgd_i_bitmap_hi)) << 32) |
  	    le32toh(gd->ext2bgd_i_bitmap));
  }
  
  uint64_t
  e2fs_gd_get_i_tables(struct ext2_gd *gd)
  {
  
  	return (((uint64_t)(le32toh(gd->ext4bgd_i_tables_hi)) << 32) |
  	    le32toh(gd->ext2bgd_i_tables));
  }
  
  static uint32_t
  e2fs_gd_get_nbfree(struct ext2_gd *gd)
  {
  
  	return (((uint32_t)(le16toh(gd->ext4bgd_nbfree_hi)) << 16) |
  	    le16toh(gd->ext2bgd_nbfree));
  }
  
  static void
  e2fs_gd_set_nbfree(struct ext2_gd *gd, uint32_t val)
  {
  
  	gd->ext2bgd_nbfree = htole16(val & 0xffff);
  	gd->ext4bgd_nbfree_hi = htole16(val >> 16);
  }
  
  static uint32_t
  e2fs_gd_get_nifree(struct ext2_gd *gd)
  {
  
  	return (((uint32_t)(le16toh(gd->ext4bgd_nifree_hi)) << 16) |
  	    le16toh(gd->ext2bgd_nifree));
  }
  
  static void
  e2fs_gd_set_nifree(struct ext2_gd *gd, uint32_t val)
  {
  
  	gd->ext2bgd_nifree = htole16(val & 0xffff);
  	gd->ext4bgd_nifree_hi = htole16(val >> 16);
  }
  
  uint32_t
  e2fs_gd_get_ndirs(struct ext2_gd *gd)
  {
  
  	return (((uint32_t)(le16toh(gd->ext4bgd_ndirs_hi)) << 16) |
  	    le16toh(gd->ext2bgd_ndirs));
  }
  
  static void
  e2fs_gd_set_ndirs(struct ext2_gd *gd, uint32_t val)
  {
  
  	gd->ext2bgd_ndirs = htole16(val & 0xffff);
  	gd->ext4bgd_ndirs_hi = htole16(val >> 16);
  }
  
  static uint32_t
  e2fs_gd_get_i_unused(struct ext2_gd *gd)
  {
  	return ((uint32_t)(le16toh(gd->ext4bgd_i_unused_hi) << 16) |
  	    le16toh(gd->ext4bgd_i_unused));
  }
  
  static void
  e2fs_gd_set_i_unused(struct ext2_gd *gd, uint32_t val)
  {
  
  	gd->ext4bgd_i_unused = htole16(val & 0xffff);
  	gd->ext4bgd_i_unused_hi = htole16(val >> 16);
  }
  
  /*
   * Find a cylinder to place a directory.
   *
   * The policy implemented by this algorithm is to allocate a
   * directory inode in the same cylinder group as its parent
   * directory, but also to reserve space for its files inodes
   * and data. Restrict the number of directories which may be
   * allocated one after another in the same cylinder group
   * without intervening allocation of files.
   *
   * If we allocate a first level directory then force allocation
   * in another cylinder group.
   *
   */
  static u_long
  ext2_dirpref(struct inode *pip)
  {
  	struct m_ext2fs *fs;
  	int cg, prefcg, cgsize;
  	uint64_t avgbfree, minbfree;
  	u_int avgifree, avgndir, curdirsize;
  	u_int minifree, maxndir;
  	u_int mincg, minndir;
  	u_int dirsize, maxcontigdirs;
  
  	mtx_assert(EXT2_MTX(pip->i_ump), MA_OWNED);
  	fs = pip->i_e2fs;
  
  	avgifree = fs->e2fs_ficount / fs->e2fs_gcount;
  	avgbfree = fs->e2fs_fbcount / fs->e2fs_gcount;
  	avgndir = fs->e2fs_total_dir / fs->e2fs_gcount;
  
  	/*
  	 * Force allocation in another cg if creating a first level dir.
  	 */
  	ASSERT_VOP_LOCKED(ITOV(pip), "ext2fs_dirpref");
  	if (ITOV(pip)->v_flag & VROOT) {
  		prefcg = karc4random() % fs->e2fs_gcount;
  		mincg = prefcg;
  		minndir = fs->e2fs_ipg;
  		for (cg = prefcg; cg < fs->e2fs_gcount; cg++)
  			if (e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) < minndir &&
  			    e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= avgifree &&
  			    e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) >= avgbfree) {
  				mincg = cg;
  				minndir = e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]);
  			}
  		for (cg = 0; cg < prefcg; cg++)
  			if (e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) < minndir &&
  			    e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= avgifree &&
  			    e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) >= avgbfree) {
  				mincg = cg;
  				minndir = e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]);
  			}
  		return (mincg);
  	}
  	/*
  	 * Count various limits which used for
  	 * optimal allocation of a directory inode.
  	 */
  	maxndir = min(avgndir + fs->e2fs_ipg / 16, fs->e2fs_ipg);
  	minifree = avgifree - avgifree / 4;
  	if (minifree < 1)
  		minifree = 1;
  	minbfree = avgbfree - avgbfree / 4;
  	if (minbfree < 1)
  		minbfree = 1;
  	cgsize = fs->e2fs_fsize * fs->e2fs_fpg;
  	dirsize = AVGDIRSIZE;
  	curdirsize = avgndir ?
  	    (cgsize - avgbfree * fs->e2fs_bsize) / avgndir : 0;
  	if (dirsize < curdirsize)
  		dirsize = curdirsize;
  	maxcontigdirs = min((avgbfree * fs->e2fs_bsize) / dirsize, 255);
  	maxcontigdirs = min(maxcontigdirs, fs->e2fs_ipg / AFPDIR);
  	if (maxcontigdirs == 0)
  		maxcontigdirs = 1;
  
  	/*
  	 * Limit number of dirs in one cg and reserve space for
  	 * regular files, but only if we have no deficit in
  	 * inodes or space.
  	 */
  	prefcg = ino_to_cg(fs, pip->i_number);
  	for (cg = prefcg; cg < fs->e2fs_gcount; cg++)
  		if (e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) < maxndir &&
  		    e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= minifree &&
  		    e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) >= minbfree) {
  			if (fs->e2fs_contigdirs[cg] < maxcontigdirs)
  				return (cg);
  		}
  	for (cg = 0; cg < prefcg; cg++)
  		if (e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) < maxndir &&
  		    e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= minifree &&
  		    e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) >= minbfree) {
  			if (fs->e2fs_contigdirs[cg] < maxcontigdirs)
  				return (cg);
  		}
  	/*
  	 * This is a backstop when we have deficit in space.
  	 */
  	for (cg = prefcg; cg < fs->e2fs_gcount; cg++)
  		if (e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= avgifree)
  			return (cg);
  	for (cg = 0; cg < prefcg; cg++)
  		if (e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= avgifree)
  			break;
  	return (cg);
  }
  
  /*
   * Select the desired position for the next block in a file.
   *
   * we try to mimic what Remy does in inode_getblk/block_getblk
   *
   * we note: blocknr == 0 means that we're about to allocate either
   * a direct block or a pointer block at the first level of indirection
   * (In other words, stuff that will go in i_db[] or i_ib[])
   *
   * blocknr != 0 means that we're allocating a block that is none
   * of the above. Then, blocknr tells us the number of the block
   * that will hold the pointer
   */
  e4fs_daddr_t
  ext2_blkpref(struct inode *ip, e2fs_lbn_t lbn, int indx, e2fs_daddr_t *bap,
      e2fs_daddr_t blocknr)
  {
  	struct m_ext2fs *fs;
  	int tmp;
  
  	fs = ip->i_e2fs;
  
  	mtx_assert(EXT2_MTX(ip->i_ump), MA_OWNED);
  
  	/*
  	 * If the next block is actually what we thought it is, then set the
  	 * goal to what we thought it should be.
  	 */
  	if (ip->i_next_alloc_block == lbn && ip->i_next_alloc_goal != 0)
  		return ip->i_next_alloc_goal;
  
  	/*
  	 * Now check whether we were provided with an array that basically
  	 * tells us previous blocks to which we want to stay close.
  	 */
  	if (bap)
  		for (tmp = indx - 1; tmp >= 0; tmp--)
  			if (bap[tmp])
  				return (le32toh(bap[tmp]));
  
  	/*
  	 * Else lets fall back to the blocknr or, if there is none, follow
  	 * the rule that a block should be allocated near its inode.
  	 */
  	return (blocknr ? blocknr :
  	    (e2fs_daddr_t)(ip->i_block_group *
  	    EXT2_BLOCKS_PER_GROUP(fs)) + le32toh(fs->e2fs->e2fs_first_dblock));
  }
  
  /*
   * Implement the cylinder overflow algorithm.
   *
   * The policy implemented by this algorithm is:
   *   1) allocate the block in its requested cylinder group.
   *   2) quadratically rehash on the cylinder group number.
   *   3) brute force search for a free block.
   */
  static e4fs_daddr_t
  ext2_hashalloc(struct inode *ip, int cg, long pref, int size,
      daddr_t (*allocator) (struct inode *, int, daddr_t, int))
  {
  	struct m_ext2fs *fs;
  	e4fs_daddr_t result;
  	int i, icg = cg;
  
  	mtx_assert(EXT2_MTX(ip->i_ump), MA_OWNED);
  	fs = ip->i_e2fs;
  	/*
  	 * 1: preferred cylinder group
  	 */
  	result = (*allocator)(ip, cg, pref, size);
  	if (result)
  		return (result);
  	/*
  	 * 2: quadratic rehash
  	 */
  	for (i = 1; i < fs->e2fs_gcount; i *= 2) {
  		cg += i;
  		if (cg >= fs->e2fs_gcount)
  			cg -= fs->e2fs_gcount;
  		result = (*allocator)(ip, cg, 0, size);
  		if (result)
  			return (result);
  	}
  	/*
  	 * 3: brute force search
  	 * Note that we start at i == 2, since 0 was checked initially,
  	 * and 1 is always checked in the quadratic rehash.
  	 */
  	cg = (icg + 2) % fs->e2fs_gcount;
  	for (i = 2; i < fs->e2fs_gcount; i++) {
  		result = (*allocator)(ip, cg, 0, size);
  		if (result)
  			return (result);
  		cg++;
  		if (cg == fs->e2fs_gcount)
  			cg = 0;
  	}
  	return (0);
  }
  
  static uint64_t
  ext2_cg_number_gdb_nometa(struct m_ext2fs *fs, int cg)
  {
  
  	if (!ext2_cg_has_sb(fs, cg))
  		return (0);
  
  	if (EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_META_BG))
  		return (le32toh(fs->e2fs->e3fs_first_meta_bg));
  
  	return ((fs->e2fs_gcount + EXT2_DESCS_PER_BLOCK(fs) - 1) /
  	    EXT2_DESCS_PER_BLOCK(fs));
  }
  
  static uint64_t
  ext2_cg_number_gdb_meta(struct m_ext2fs *fs, int cg)
  {
  	unsigned long metagroup;
  	int first, last;
  
  	metagroup = cg / EXT2_DESCS_PER_BLOCK(fs);
  	first = metagroup * EXT2_DESCS_PER_BLOCK(fs);
  	last = first + EXT2_DESCS_PER_BLOCK(fs) - 1;
  
  	if (cg == first || cg == first + 1 || cg == last)
  		return (1);
  
  	return (0);
  }
  
  uint64_t
  ext2_cg_number_gdb(struct m_ext2fs *fs, int cg)
  {
  	unsigned long first_meta_bg, metagroup;
  
  	first_meta_bg = le32toh(fs->e2fs->e3fs_first_meta_bg);
  	metagroup = cg / EXT2_DESCS_PER_BLOCK(fs);
  
  	if (!EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_META_BG) ||
  	    metagroup < first_meta_bg)
  		return (ext2_cg_number_gdb_nometa(fs, cg));
  
  	return ext2_cg_number_gdb_meta(fs, cg);
  }
  
  static int
  ext2_number_base_meta_blocks(struct m_ext2fs *fs, int cg)
  {
  	int number;
  
  	number = ext2_cg_has_sb(fs, cg);
  
  	if (!EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_META_BG) ||
  	    cg < le32toh(fs->e2fs->e3fs_first_meta_bg) *
  	    EXT2_DESCS_PER_BLOCK(fs)) {
  		if (number) {
  			number += ext2_cg_number_gdb(fs, cg);
  			number += le16toh(fs->e2fs->e2fs_reserved_ngdb);
  		}
  	} else {
  		number += ext2_cg_number_gdb(fs, cg);
  	}
  
  	return (number);
  }
  
  static void
  ext2_mark_bitmap_end(int start_bit, int end_bit, char *bitmap)
  {
  	int i;
  
  	if (start_bit >= end_bit)
  		return;
  
  	for (i = start_bit; i < ((start_bit + 7) & ~7UL); i++)
  		setbit(bitmap, i);
  	if (i < end_bit)
  		memset(bitmap + (i >> 3), 0xff, (end_bit - i) >> 3);
  }
  
  static int
  ext2_get_group_number(struct m_ext2fs *fs, e4fs_daddr_t block)
  {
  
  	return ((block - le32toh(fs->e2fs->e2fs_first_dblock)) /
  	    fs->e2fs_bsize);
  }
  
  static int
  ext2_block_in_group(struct m_ext2fs *fs, e4fs_daddr_t block, int cg)
  {
  
  	return ((ext2_get_group_number(fs, block) == cg) ? 1 : 0);
  }
  
  static int
  ext2_cg_block_bitmap_init(struct m_ext2fs *fs, int cg, struct buf *bp)
  {
  	int bit, bit_max, inodes_per_block;
  	uint64_t start, tmp;
  
  	if (!(le16toh(fs->e2fs_gd[cg].ext4bgd_flags) & EXT2_BG_BLOCK_UNINIT))
  		return (0);
  
  	memset(bp->b_data, 0, fs->e2fs_bsize);
  
  	bit_max = ext2_number_base_meta_blocks(fs, cg);
  	if ((bit_max >> 3) >= fs->e2fs_bsize)
  		return (EINVAL);
  
  	for (bit = 0; bit < bit_max; bit++)
  		setbit(bp->b_data, bit);
  
  	start = (uint64_t)cg * fs->e2fs_bpg +
  	    le32toh(fs->e2fs->e2fs_first_dblock);
  
  	/* Set bits for block and inode bitmaps, and inode table. */
  	tmp = e2fs_gd_get_b_bitmap(&fs->e2fs_gd[cg]);
  	if (!EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_FLEX_BG) ||
  	    ext2_block_in_group(fs, tmp, cg))
  		setbit(bp->b_data, tmp - start);
  
  	tmp = e2fs_gd_get_i_bitmap(&fs->e2fs_gd[cg]);
  	if (!EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_FLEX_BG) ||
  	    ext2_block_in_group(fs, tmp, cg))
  		setbit(bp->b_data, tmp - start);
  
  	tmp = e2fs_gd_get_i_tables(&fs->e2fs_gd[cg]);
  	inodes_per_block = fs->e2fs_bsize/EXT2_INODE_SIZE(fs);
  	while( tmp < e2fs_gd_get_i_tables(&fs->e2fs_gd[cg]) +
  	    fs->e2fs_ipg / inodes_per_block ) {
  		if (!EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_FLEX_BG) ||
  		    ext2_block_in_group(fs, tmp, cg))
  			setbit(bp->b_data, tmp - start);
  		tmp++;
  	}
  
  	/*
  	 * Also if the number of blocks within the group is less than
  	 * the blocksize * 8 ( which is the size of bitmap ), set rest
  	 * of the block bitmap to 1
  	 */
  	ext2_mark_bitmap_end(fs->e2fs_bpg, fs->e2fs_bsize * 8,
  	    bp->b_data);
  
  	/* Clean the flag */
  	fs->e2fs_gd[cg].ext4bgd_flags = htole16(le16toh(
  	    fs->e2fs_gd[cg].ext4bgd_flags) & ~EXT2_BG_BLOCK_UNINIT);
  
  	return (0);
  }
  
  static int
  ext2_b_bitmap_validate(struct m_ext2fs *fs, struct buf *bp, int cg)
  {
  	struct ext2_gd *gd;
  	uint64_t group_first_block;
  	unsigned int offset, max_bit;
  
  	if (EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_FLEX_BG)) {
  		/*
  		 * It is not possible to check block bitmap in case of this
  		 * feature, because the inode and block bitmaps and inode table
  		 * blocks may not be in the group at all.
  		 * So, skip check in this case.
  		 */
  		return (0);
  	}
  
  	gd = &fs->e2fs_gd[cg];
  	max_bit = fs->e2fs_fpg;
  	group_first_block = ((uint64_t)cg) * fs->e2fs_fpg +
  	    le32toh(fs->e2fs->e2fs_first_dblock);
  
  	/* Check block bitmap block number */
  	offset = e2fs_gd_get_b_bitmap(gd) - group_first_block;
  	if (offset >= max_bit || !isset(bp->b_data, offset)) {
  		SDT_PROBE2(ext2fs, , alloc, ext2_b_bitmap_validate_error,
  		    "bad block bitmap, group", cg);
  		return (EINVAL);
  	}
  
  	/* Check inode bitmap block number */
  	offset = e2fs_gd_get_i_bitmap(gd) - group_first_block;
  	if (offset >= max_bit || !isset(bp->b_data, offset)) {
  		SDT_PROBE2(ext2fs, , alloc, ext2_b_bitmap_validate_error,
  		    "bad inode bitmap", cg);
  		return (EINVAL);
  	}
  
  	/* Check inode table */
  	offset = e2fs_gd_get_i_tables(gd) - group_first_block;
  	if (offset >= max_bit || offset + fs->e2fs_itpg >= max_bit) {
  		SDT_PROBE2(ext2fs, , alloc, ext2_b_bitmap_validate_error,
  		    "bad inode table, group", cg);
  		return (EINVAL);
  	}
  
  	return (0);
  }
  
  /*
   * Determine whether a block can be allocated.
   *
   * Check to see if a block of the appropriate size is available,
   * and if it is, allocate it.
   */
  static daddr_t
  ext2_alloccg(struct inode *ip, int cg, daddr_t bpref, int size)
  {
  	struct m_ext2fs *fs;
  	struct buf *bp;
  	struct ext2mount *ump;
  	daddr_t bno, runstart, runlen;
  	int bit, loc, end, error, start;
  	char *bbp;
  	/* XXX ondisk32 */
  	fs = ip->i_e2fs;
  	ump = ip->i_ump;
  	if (e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) == 0)
  		return (0);
  
  	EXT2_UNLOCK(ump);
  	error = bread(ip->i_devvp, fsbtodoff(fs,
  	    e2fs_gd_get_b_bitmap(&fs->e2fs_gd[cg])),
  	    (int)fs->e2fs_bsize, &bp);
  	if (error)
  		goto fail;
  
  	if (EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_GDT_CSUM) ||
  	    EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_METADATA_CKSUM)) {
  		error = ext2_cg_block_bitmap_init(fs, cg, bp);
  		if (error)
  			goto fail;
  
  		ext2_gd_b_bitmap_csum_set(fs, cg, bp);
  	}
  	error = ext2_gd_b_bitmap_csum_verify(fs, cg, bp);
  	if (error)
  		goto fail;
  
  	error = ext2_b_bitmap_validate(fs,bp, cg);
  	if (error)
  		goto fail;
  
  	/*
  	 * Check, that another thread did not not allocate the last block in
  	 * this group while we were waiting for the buffer.
  	 */
  	if (e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) == 0)
  		goto fail;
  
  	bbp = (char *)bp->b_data;
  
  	if (dtog(fs, bpref) != cg)
  		bpref = 0;
  	if (bpref != 0) {
  		bpref = dtogd(fs, bpref);
  		/*
  		 * if the requested block is available, use it
  		 */
  		if (isclr(bbp, bpref)) {
  			bno = bpref;
  			goto gotit;
  		}
  	}
  	/*
  	 * no blocks in the requested cylinder, so take next
  	 * available one in this cylinder group.
  	 * first try to get 8 contigous blocks, then fall back to a single
  	 * block.
  	 */
  	if (bpref)
  		start = dtogd(fs, bpref) / NBBY;
  	else
  		start = 0;
  	end = howmany(fs->e2fs_fpg, NBBY) - start;
  retry:
  	runlen = 0;
  	runstart = 0;
  	for (loc = start; loc < end; loc++) {
  		if (bbp[loc] == (char)0xff) {
  			runlen = 0;
  			continue;
  		}
  
  		/* Start of a run, find the number of high clear bits. */
  		if (runlen == 0) {
  			bit = fls(bbp[loc]);
  			runlen = NBBY - bit;
  			runstart = loc * NBBY + bit;
  		} else if (bbp[loc] == 0) {
  			/* Continue a run. */
  			runlen += NBBY;
  		} else {
  			/*
  			 * Finish the current run.  If it isn't long
  			 * enough, start a new one.
  			 */
  			bit = ffs(bbp[loc]) - 1;
  			runlen += bit;
  			if (runlen >= 8) {
  				bno = runstart;
  				goto gotit;
  			}
  
  			/* Run was too short, start a new one. */
  			bit = fls(bbp[loc]);
  			runlen = NBBY - bit;
  			runstart = loc * NBBY + bit;
  		}
  
  		/* If the current run is long enough, use it. */
  		if (runlen >= 8) {
  			bno = runstart;
  			goto gotit;
  		}
  	}
  	if (start != 0) {
  		end = start;
  		start = 0;
  		goto retry;
  	}
  	bno = ext2_mapsearch(fs, bbp, bpref);
  	if (bno < 0)
  		goto fail;
  
  gotit:
  #ifdef INVARIANTS
  	if (isset(bbp, bno)) {
  		printf("ext2fs_alloccgblk: cg=%d bno=%jd fs=%s\n",
  		    cg, (intmax_t)bno, fs->e2fs_fsmnt);
  		panic("ext2fs_alloccg: dup alloc");
  	}
  #endif
  	setbit(bbp, bno);
  	EXT2_LOCK(ump);
  	ext2_clusteracct(fs, bbp, cg, bno, -1);
  	fs->e2fs_fbcount--;
  	e2fs_gd_set_nbfree(&fs->e2fs_gd[cg],
  	    e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) - 1);
  	fs->e2fs_fmod = 1;
  	EXT2_UNLOCK(ump);
  	ext2_gd_b_bitmap_csum_set(fs, cg, bp);
  	bdwrite(bp);
  	return (((uint64_t)cg) * fs->e2fs_fpg +
  	    le32toh(fs->e2fs->e2fs_first_dblock) + bno);
  
  fail:
  	brelse(bp);
  	EXT2_LOCK(ump);
  	return (0);
  }
  
  /*
   * Determine whether a cluster can be allocated.
   */
  static daddr_t
  ext2_clusteralloc(struct inode *ip, int cg, daddr_t bpref, int len)
  {
  	struct m_ext2fs *fs;
  	struct ext2mount *ump;
  	struct buf *bp;
  	char *bbp;
  	int bit, error, got, i, loc, run;
  	int32_t *lp;
  	daddr_t bno;
  
  	fs = ip->i_e2fs;
  	ump = ip->i_ump;
  
  	if (fs->e2fs_maxcluster[cg] < len)
  		return (0);
  
  	EXT2_UNLOCK(ump);
  	error = bread(ip->i_devvp,
  	    fsbtodoff(fs, e2fs_gd_get_b_bitmap(&fs->e2fs_gd[cg])),
  	    (int)fs->e2fs_bsize, &bp);
  	if (error)
  		goto fail_lock;
  
  	bbp = (char *)bp->b_data;
  	EXT2_LOCK(ump);
  	/*
  	 * Check to see if a cluster of the needed size (or bigger) is
  	 * available in this cylinder group.
  	 */
  	lp = &fs->e2fs_clustersum[cg].cs_sum[len];
  	for (i = len; i <= fs->e2fs_contigsumsize; i++)
  		if (*lp++ > 0)
  			break;
  	if (i > fs->e2fs_contigsumsize) {
  		/*
  		 * Update the cluster summary information to reflect
  		 * the true maximum-sized cluster so that future cluster
  		 * allocation requests can avoid reading the bitmap only
  		 * to find no cluster.
  		 */
  		lp = &fs->e2fs_clustersum[cg].cs_sum[len - 1];
  		for (i = len - 1; i > 0; i--)
  			if (*lp-- > 0)
  				break;
  		fs->e2fs_maxcluster[cg] = i;
  		goto fail;
  	}
  	EXT2_UNLOCK(ump);
  
  	/* Search the bitmap to find a big enough cluster like in FFS. */
  	if (dtog(fs, bpref) != cg)
  		bpref = 0;
  	if (bpref != 0)
  		bpref = dtogd(fs, bpref);
  	loc = bpref / NBBY;
  	bit = 1 << (bpref % NBBY);
  	for (run = 0, got = bpref; got < fs->e2fs_fpg; got++) {
  		if ((bbp[loc] & bit) != 0)
  			run = 0;
  		else {
  			run++;
  			if (run == len)
  				break;
  		}
  		if ((got & (NBBY - 1)) != (NBBY - 1))
  			bit <<= 1;
  		else {
  			loc++;
  			bit = 1;
  		}
  	}
  
  	if (got >= fs->e2fs_fpg)
  		goto fail_lock;
  
  	/* Allocate the cluster that we found. */
  	for (i = 1; i < len; i++)
  		if (!isclr(bbp, got - run + i))
  			panic("ext2_clusteralloc: map mismatch");
  
  	bno = got - run + 1;
  	if (bno >= fs->e2fs_fpg)
  		panic("ext2_clusteralloc: allocated out of group");
  
  	EXT2_LOCK(ump);
  	for (i = 0; i < len; i += fs->e2fs_fpb) {
  		setbit(bbp, bno + i);
  		ext2_clusteracct(fs, bbp, cg, bno + i, -1);
  		fs->e2fs_fbcount--;
  		e2fs_gd_set_nbfree(&fs->e2fs_gd[cg],
  		    e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) - 1);
  	}
  	fs->e2fs_fmod = 1;
  	EXT2_UNLOCK(ump);
  
  	bdwrite(bp);
  	return (cg * fs->e2fs_fpg + le32toh(fs->e2fs->e2fs_first_dblock)
  	    + bno);
  
  fail_lock:
  	EXT2_LOCK(ump);
  fail:
  	brelse(bp);
  	return (0);
  }
  
  static int
  ext2_zero_inode_table(struct inode *ip, int cg)
  {
  	struct m_ext2fs *fs;
  	struct buf *bp;
  	int i, all_blks, used_blks;
  
  	fs = ip->i_e2fs;
  
  	if (le16toh(fs->e2fs_gd[cg].ext4bgd_flags) & EXT2_BG_INODE_ZEROED)
  		return (0);
  
  	all_blks = le16toh(fs->e2fs->e2fs_inode_size) * fs->e2fs_ipg /
  	    fs->e2fs_bsize;
  
  	used_blks = howmany(fs->e2fs_ipg -
  	    e2fs_gd_get_i_unused(&fs->e2fs_gd[cg]),
  	    fs->e2fs_bsize / EXT2_INODE_SIZE(fs));
  
  	for (i = 0; i < all_blks - used_blks; i++) {
  		bp = getblk(ip->i_devvp, fsbtodoff(fs,
  		    e2fs_gd_get_i_tables(&fs->e2fs_gd[cg]) + used_blks + i),
  		    fs->e2fs_bsize, 0, 0);
  		if (!bp)
  			return (EIO);
  
  		vfs_bio_clrbuf(bp);
  		bawrite(bp);
  	}
  
  	fs->e2fs_gd[cg].ext4bgd_flags = htole16(le16toh(
  	    fs->e2fs_gd[cg].ext4bgd_flags) | EXT2_BG_INODE_ZEROED);
  
  	return (0);
  }
  
  static void
  ext2_fix_bitmap_tail(unsigned char *bitmap, int first, int last)
  {
  	int i;
  
  	for (i = first; i <= last; i++)
  		bitmap[i] = 0xff;
  }
  
  /*
   * Determine whether an inode can be allocated.
   *
   * Check to see if an inode is available, and if it is,
   * allocate it using tode in the specified cylinder group.
   */
  static daddr_t
  ext2_nodealloccg(struct inode *ip, int cg, daddr_t ipref, int mode)
  {
  	struct m_ext2fs *fs;
  	struct buf *bp;
  	struct ext2mount *ump;
  	int error, start, len, ifree, ibytes;
  	char *ibp, *loc;
  
  	ipref--;	/* to avoid a lot of (ipref -1) */
  	if (ipref == -1)
  		ipref = 0;
  	fs = ip->i_e2fs;
  	ump = ip->i_ump;
  	if (e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) == 0)
  		return (0);
  	EXT2_UNLOCK(ump);
  	error = bread(ip->i_devvp, fsbtodoff(fs,
  	    e2fs_gd_get_i_bitmap(&fs->e2fs_gd[cg])),
  	    (int)fs->e2fs_bsize, &bp);
  	if (error) {
  		brelse(bp);
  		EXT2_LOCK(ump);
  		return (0);
  	}
  	if (EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_GDT_CSUM) ||
  	    EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_METADATA_CKSUM)) {
  		if (le16toh(fs->e2fs_gd[cg].ext4bgd_flags) &
  		    EXT2_BG_INODE_UNINIT) {
  			ibytes = fs->e2fs_ipg / 8;
  			memset(bp->b_data, 0, ibytes - 1);
  			ext2_fix_bitmap_tail(bp->b_data, ibytes,
  			    fs->e2fs_bsize - 1);
  			fs->e2fs_gd[cg].ext4bgd_flags = htole16(le16toh(
  			    fs->e2fs_gd[cg].ext4bgd_flags) &
  			    ~EXT2_BG_INODE_UNINIT);
  		}
  		ext2_gd_i_bitmap_csum_set(fs, cg, bp);
  		error = ext2_zero_inode_table(ip, cg);
  		if (error) {
  			brelse(bp);
  			EXT2_LOCK(ump);
  			return (0);
  		}
  	}
  	error = ext2_gd_i_bitmap_csum_verify(fs, cg, bp);
  	if (error) {
  		brelse(bp);
  		EXT2_LOCK(ump);
  		return (0);
  	}
  	if (e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) == 0) {
  		/*
  		 * Another thread allocated the last i-node in this
  		 * group while we were waiting for the buffer.
  		 */
  		brelse(bp);
  		EXT2_LOCK(ump);
  		return (0);
  	}
  	ibp = (char *)bp->b_data;
  	if (ipref) {
  		ipref %= fs->e2fs_ipg;
  		if (isclr(ibp, ipref))
  			goto gotit;
  	}
  	start = ipref / NBBY;
  	len = howmany(fs->e2fs_ipg - ipref, NBBY);
  	loc = memcchr(&ibp[start], 0xff, len);
  	if (loc == NULL) {
  		len = start + 1;
  		start = 0;
  		loc = memcchr(&ibp[start], 0xff, len);
  		if (loc == NULL) {
  			SDT_PROBE3(ext2fs, , alloc,
  			    ext2_nodealloccg_bmap_corrupted, cg, ipref,
  			    fs->e2fs_fsmnt);
  			brelse(bp);
  			EXT2_LOCK(ump);
  			return (0);
  		}
  	}
  	ipref = (loc - ibp) * NBBY + ffs(~*loc) - 1;
  gotit:
  	setbit(ibp, ipref);
  	EXT2_LOCK(ump);
  	e2fs_gd_set_nifree(&fs->e2fs_gd[cg],
  	    e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) - 1);
  	if (EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_GDT_CSUM) ||
  	    EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_METADATA_CKSUM)) {
  		ifree = fs->e2fs_ipg - e2fs_gd_get_i_unused(&fs->e2fs_gd[cg]);
  		if (ipref + 1 > ifree)
  			e2fs_gd_set_i_unused(&fs->e2fs_gd[cg],
  			    fs->e2fs_ipg - (ipref + 1));
  	}
  	fs->e2fs_ficount--;
  	fs->e2fs_fmod = 1;
  	if ((mode & IFMT) == IFDIR) {
  		e2fs_gd_set_ndirs(&fs->e2fs_gd[cg],
  		    e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) + 1);
  		fs->e2fs_total_dir++;
  	}
  	EXT2_UNLOCK(ump);
  	ext2_gd_i_bitmap_csum_set(fs, cg, bp);
  	bdwrite(bp);
  	return ((uint64_t)cg * fs->e2fs_ipg + ipref + 1);
  }
  
  /*
   * Free a block or fragment.
   *
   */
  void
  ext2_blkfree(struct inode *ip, e4fs_daddr_t bno, long size)
  {
  	struct m_ext2fs *fs;
  	struct buf *bp;
  	struct ext2mount *ump;
  	int cg, error;
  	char *bbp;
  
  	fs = ip->i_e2fs;
  	ump = ip->i_ump;
  	cg = dtog(fs, bno);
  	if (bno >= fs->e2fs_bcount) {
  		SDT_PROBE2(ext2fs, , alloc, ext2_blkfree_bad_block,
  		    ip->i_number, bno);
  		return;
  	}
  	error = bread(ip->i_devvp,
  	    fsbtodoff(fs, e2fs_gd_get_b_bitmap(&fs->e2fs_gd[cg])),
  	    (int)fs->e2fs_bsize, &bp);
  	if (error) {
  		brelse(bp);
  		return;
  	}
  	bbp = (char *)bp->b_data;
  	bno = dtogd(fs, bno);
  	if (isclr(bbp, bno)) {
  		panic("ext2_blkfree: freeing free block %lld, fs=%s",
  		    (long long)bno, fs->e2fs_fsmnt);
  	}
  	clrbit(bbp, bno);
  	EXT2_LOCK(ump);
  	ext2_clusteracct(fs, bbp, cg, bno, 1);
  	fs->e2fs_fbcount++;
  	e2fs_gd_set_nbfree(&fs->e2fs_gd[cg],
  	    e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) + 1);
  	fs->e2fs_fmod = 1;
  	EXT2_UNLOCK(ump);
  	ext2_gd_b_bitmap_csum_set(fs, cg, bp);
  	bdwrite(bp);
  }
  
  /*
   * Free an inode.
   *
   */
  int
  ext2_vfree(struct vnode *pvp, ino_t ino, int mode)
  {
  	struct m_ext2fs *fs;
  	struct inode *pip;
  	struct buf *bp;
  	struct ext2mount *ump;
  	int error, cg;
  	char *ibp;
  
  	pip = VTOI(pvp);
  	fs = pip->i_e2fs;
  	ump = pip->i_ump;
  	if ((u_int)ino > fs->e2fs_ipg * fs->e2fs_gcount)
  		panic("ext2_vfree: range: devvp = %p, ino = %ju, fs = %s",
  		    pip->i_devvp, (uintmax_t)ino, fs->e2fs_fsmnt);
  
  	cg = ino_to_cg(fs, ino);
  	error = bread(pip->i_devvp,
  	    fsbtodoff(fs, e2fs_gd_get_i_bitmap(&fs->e2fs_gd[cg])),
  	    (int)fs->e2fs_bsize, &bp);
  	if (error) {
  		brelse(bp);
  		return (0);
  	}
  	ibp = (char *)bp->b_data;
  	ino = (ino - 1) % fs->e2fs_ipg;
  	if (isclr(ibp, ino)) {
  		SDT_PROBE2(ext2fs, , alloc, ext2_vfree_doublefree,
  		    fs->e2fs_fsmnt, ino);
  		if (fs->e2fs_ronly == 0)
  			panic("ext2_vfree: freeing free inode");
  	}
  	clrbit(ibp, ino);
  	EXT2_LOCK(ump);
  	fs->e2fs_ficount++;
  	e2fs_gd_set_nifree(&fs->e2fs_gd[cg],
  	    e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) + 1);
  	if ((mode & IFMT) == IFDIR) {
  		e2fs_gd_set_ndirs(&fs->e2fs_gd[cg],
  		    e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) - 1);
  		fs->e2fs_total_dir--;
  	}
  	fs->e2fs_fmod = 1;
  	EXT2_UNLOCK(ump);
  	ext2_gd_i_bitmap_csum_set(fs, cg, bp);
  	bdwrite(bp);
  	return (0);
  }
  
  /*
   * Find a block in the specified cylinder group.
   *
   * It is a panic if a request is made to find a block if none are
   * available.
   */
  static daddr_t
  ext2_mapsearch(struct m_ext2fs *fs, char *bbp, daddr_t bpref)
  {
  	char *loc;
  	int start, len;
  
  	/*
  	 * find the fragment by searching through the free block
  	 * map for an appropriate bit pattern
  	 */
  	if (bpref)
  		start = dtogd(fs, bpref) / NBBY;
  	else
  		start = 0;
  	len = howmany(fs->e2fs_fpg, NBBY) - start;
  	loc = memcchr(&bbp[start], 0xff, len);
  	if (loc == NULL) {
  		len = start + 1;
  		start = 0;
  		loc = memcchr(&bbp[start], 0xff, len);
  		if (loc == NULL) {
  			panic("ext2_mapsearch: map corrupted: start=%d, len=%d,"
  			    "fs=%s", start, len, fs->e2fs_fsmnt);
  			/* NOTREACHED */
  		}
  	}
  	return ((loc - bbp) * NBBY + ffs(~*loc) - 1);
  }
  
  int
  ext2_cg_has_sb(struct m_ext2fs *fs, int cg)
  {
  	int a3, a5, a7;
  
  	if (cg == 0)
  		return (1);
  
  	if (EXT2_HAS_COMPAT_FEATURE(fs, EXT2F_COMPAT_SPARSESUPER2)) {
  		if (cg == le32toh(fs->e2fs->e4fs_backup_bgs[0]) ||
  		    cg == le32toh(fs->e2fs->e4fs_backup_bgs[1]))
  			return (1);
  		return (0);
  	}
  
  	if ((cg <= 1) ||
  	    !EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_SPARSESUPER))
  		return (1);
  
  	if (!(cg & 1))
  		return (0);
  
  	for (a3 = 3, a5 = 5, a7 = 7;
  	    a3 <= cg || a5 <= cg || a7 <= cg;
  	    a3 *= 3, a5 *= 5, a7 *= 7)
  		if (cg == a3 || cg == a5 || cg == a7)
  			return (1);
  	return (0);
  }
  