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extents.c

/*
 * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com
 * Written by Alex Tomas <alex@clusterfs.com>
 *
 * Architecture independence:
 *   Copyright (c) 2005, Bull S.A.
 *   Written by Pierre Peiffer <pierre.peiffer@bull.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * 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 Licens
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
 */

/*
 * Extents support for EXT4
 *
 * TODO:
 *   - ext4*_error() should be used in some situations
 *   - analyze all BUG()/BUG_ON(), use -EIO where appropriate
 *   - smart tree reduction
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/ext4_jbd2.h>
#include <linux/jbd2.h>
#include <linux/highuid.h>
#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/falloc.h>
#include <linux/ext4_fs_extents.h>
#include <asm/uaccess.h>


/*
 * ext_pblock:
 * combine low and high parts of physical block number into ext4_fsblk_t
 */
static ext4_fsblk_t ext_pblock(struct ext4_extent *ex)
{
      ext4_fsblk_t block;

      block = le32_to_cpu(ex->ee_start_lo);
      block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1;
      return block;
}

/*
 * idx_pblock:
 * combine low and high parts of a leaf physical block number into ext4_fsblk_t
 */
static ext4_fsblk_t idx_pblock(struct ext4_extent_idx *ix)
{
      ext4_fsblk_t block;

      block = le32_to_cpu(ix->ei_leaf_lo);
      block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1;
      return block;
}

/*
 * ext4_ext_store_pblock:
 * stores a large physical block number into an extent struct,
 * breaking it into parts
 */
static void ext4_ext_store_pblock(struct ext4_extent *ex, ext4_fsblk_t pb)
{
      ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
      ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 0xffff);
}

/*
 * ext4_idx_store_pblock:
 * stores a large physical block number into an index struct,
 * breaking it into parts
 */
static void ext4_idx_store_pblock(struct ext4_extent_idx *ix, ext4_fsblk_t pb)
{
      ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
      ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 0xffff);
}

static handle_t *ext4_ext_journal_restart(handle_t *handle, int needed)
{
      int err;

      if (handle->h_buffer_credits > needed)
            return handle;
      if (!ext4_journal_extend(handle, needed))
            return handle;
      err = ext4_journal_restart(handle, needed);

      return handle;
}

/*
 * could return:
 *  - EROFS
 *  - ENOMEM
 */
static int ext4_ext_get_access(handle_t *handle, struct inode *inode,
                        struct ext4_ext_path *path)
{
      if (path->p_bh) {
            /* path points to block */
            return ext4_journal_get_write_access(handle, path->p_bh);
      }
      /* path points to leaf/index in inode body */
      /* we use in-core data, no need to protect them */
      return 0;
}

/*
 * could return:
 *  - EROFS
 *  - ENOMEM
 *  - EIO
 */
static int ext4_ext_dirty(handle_t *handle, struct inode *inode,
                        struct ext4_ext_path *path)
{
      int err;
      if (path->p_bh) {
            /* path points to block */
            err = ext4_journal_dirty_metadata(handle, path->p_bh);
      } else {
            /* path points to leaf/index in inode body */
            err = ext4_mark_inode_dirty(handle, inode);
      }
      return err;
}

static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
                        struct ext4_ext_path *path,
                        ext4_fsblk_t block)
{
      struct ext4_inode_info *ei = EXT4_I(inode);
      ext4_fsblk_t bg_start;
      ext4_grpblk_t colour;
      int depth;

      if (path) {
            struct ext4_extent *ex;
            depth = path->p_depth;

            /* try to predict block placement */
            ex = path[depth].p_ext;
            if (ex)
                  return ext_pblock(ex)+(block-le32_to_cpu(ex->ee_block));

            /* it looks like index is empty;
             * try to find starting block from index itself */
            if (path[depth].p_bh)
                  return path[depth].p_bh->b_blocknr;
      }

      /* OK. use inode's group */
      bg_start = (ei->i_block_group * EXT4_BLOCKS_PER_GROUP(inode->i_sb)) +
            le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_first_data_block);
      colour = (current->pid % 16) *
                  (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
      return bg_start + colour + block;
}

static ext4_fsblk_t
ext4_ext_new_block(handle_t *handle, struct inode *inode,
                  struct ext4_ext_path *path,
                  struct ext4_extent *ex, int *err)
{
      ext4_fsblk_t goal, newblock;

      goal = ext4_ext_find_goal(inode, path, le32_to_cpu(ex->ee_block));
      newblock = ext4_new_block(handle, inode, goal, err);
      return newblock;
}

static int ext4_ext_space_block(struct inode *inode)
{
      int size;

      size = (inode->i_sb->s_blocksize - sizeof(struct ext4_extent_header))
                  / sizeof(struct ext4_extent);
#ifdef AGGRESSIVE_TEST
      if (size > 6)
            size = 6;
#endif
      return size;
}

static int ext4_ext_space_block_idx(struct inode *inode)
{
      int size;

      size = (inode->i_sb->s_blocksize - sizeof(struct ext4_extent_header))
                  / sizeof(struct ext4_extent_idx);
#ifdef AGGRESSIVE_TEST
      if (size > 5)
            size = 5;
#endif
      return size;
}

static int ext4_ext_space_root(struct inode *inode)
{
      int size;

      size = sizeof(EXT4_I(inode)->i_data);
      size -= sizeof(struct ext4_extent_header);
      size /= sizeof(struct ext4_extent);
#ifdef AGGRESSIVE_TEST
      if (size > 3)
            size = 3;
#endif
      return size;
}

static int ext4_ext_space_root_idx(struct inode *inode)
{
      int size;

      size = sizeof(EXT4_I(inode)->i_data);
      size -= sizeof(struct ext4_extent_header);
      size /= sizeof(struct ext4_extent_idx);
#ifdef AGGRESSIVE_TEST
      if (size > 4)
            size = 4;
#endif
      return size;
}

static int
ext4_ext_max_entries(struct inode *inode, int depth)
{
      int max;

      if (depth == ext_depth(inode)) {
            if (depth == 0)
                  max = ext4_ext_space_root(inode);
            else
                  max = ext4_ext_space_root_idx(inode);
      } else {
            if (depth == 0)
                  max = ext4_ext_space_block(inode);
            else
                  max = ext4_ext_space_block_idx(inode);
      }

      return max;
}

static int __ext4_ext_check_header(const char *function, struct inode *inode,
                              struct ext4_extent_header *eh,
                              int depth)
{
      const char *error_msg;
      int max = 0;

      if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
            error_msg = "invalid magic";
            goto corrupted;
      }
      if (unlikely(le16_to_cpu(eh->eh_depth) != depth)) {
            error_msg = "unexpected eh_depth";
            goto corrupted;
      }
      if (unlikely(eh->eh_max == 0)) {
            error_msg = "invalid eh_max";
            goto corrupted;
      }
      max = ext4_ext_max_entries(inode, depth);
      if (unlikely(le16_to_cpu(eh->eh_max) > max)) {
            error_msg = "too large eh_max";
            goto corrupted;
      }
      if (unlikely(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max))) {
            error_msg = "invalid eh_entries";
            goto corrupted;
      }
      return 0;

corrupted:
      ext4_error(inode->i_sb, function,
                  "bad header in inode #%lu: %s - magic %x, "
                  "entries %u, max %u(%u), depth %u(%u)",
                  inode->i_ino, error_msg, le16_to_cpu(eh->eh_magic),
                  le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max),
                  max, le16_to_cpu(eh->eh_depth), depth);

      return -EIO;
}

#define ext4_ext_check_header(inode, eh, depth) \
      __ext4_ext_check_header(__FUNCTION__, inode, eh, depth)

#ifdef EXT_DEBUG
static void ext4_ext_show_path(struct inode *inode, struct ext4_ext_path *path)
{
      int k, l = path->p_depth;

      ext_debug("path:");
      for (k = 0; k <= l; k++, path++) {
            if (path->p_idx) {
              ext_debug("  %d->%llu", le32_to_cpu(path->p_idx->ei_block),
                      idx_pblock(path->p_idx));
            } else if (path->p_ext) {
                  ext_debug("  %d:%d:%llu ",
                          le32_to_cpu(path->p_ext->ee_block),
                          ext4_ext_get_actual_len(path->p_ext),
                          ext_pblock(path->p_ext));
            } else
                  ext_debug("  []");
      }
      ext_debug("\n");
}

static void ext4_ext_show_leaf(struct inode *inode, struct ext4_ext_path *path)
{
      int depth = ext_depth(inode);
      struct ext4_extent_header *eh;
      struct ext4_extent *ex;
      int i;

      if (!path)
            return;

      eh = path[depth].p_hdr;
      ex = EXT_FIRST_EXTENT(eh);

      for (i = 0; i < le16_to_cpu(eh->eh_entries); i++, ex++) {
            ext_debug("%d:%d:%llu ", le32_to_cpu(ex->ee_block),
                    ext4_ext_get_actual_len(ex), ext_pblock(ex));
      }
      ext_debug("\n");
}
#else
#define ext4_ext_show_path(inode,path)
#define ext4_ext_show_leaf(inode,path)
#endif

static void ext4_ext_drop_refs(struct ext4_ext_path *path)
{
      int depth = path->p_depth;
      int i;

      for (i = 0; i <= depth; i++, path++)
            if (path->p_bh) {
                  brelse(path->p_bh);
                  path->p_bh = NULL;
            }
}

/*
 * ext4_ext_binsearch_idx:
 * binary search for the closest index of the given block
 * the header must be checked before calling this
 */
static void
ext4_ext_binsearch_idx(struct inode *inode, struct ext4_ext_path *path, int block)
{
      struct ext4_extent_header *eh = path->p_hdr;
      struct ext4_extent_idx *r, *l, *m;


      ext_debug("binsearch for %d(idx):  ", block);

      l = EXT_FIRST_INDEX(eh) + 1;
      r = EXT_LAST_INDEX(eh);
      while (l <= r) {
            m = l + (r - l) / 2;
            if (block < le32_to_cpu(m->ei_block))
                  r = m - 1;
            else
                  l = m + 1;
            ext_debug("%p(%u):%p(%u):%p(%u) ", l, le32_to_cpu(l->ei_block),
                        m, le32_to_cpu(m->ei_block),
                        r, le32_to_cpu(r->ei_block));
      }

      path->p_idx = l - 1;
      ext_debug("  -> %d->%lld ", le32_to_cpu(path->p_idx->ei_block),
              idx_pblock(path->p_idx));

#ifdef CHECK_BINSEARCH
      {
            struct ext4_extent_idx *chix, *ix;
            int k;

            chix = ix = EXT_FIRST_INDEX(eh);
            for (k = 0; k < le16_to_cpu(eh->eh_entries); k++, ix++) {
              if (k != 0 &&
                  le32_to_cpu(ix->ei_block) <= le32_to_cpu(ix[-1].ei_block)) {
                        printk("k=%d, ix=0x%p, first=0x%p\n", k,
                              ix, EXT_FIRST_INDEX(eh));
                        printk("%u <= %u\n",
                               le32_to_cpu(ix->ei_block),
                               le32_to_cpu(ix[-1].ei_block));
                  }
                  BUG_ON(k && le32_to_cpu(ix->ei_block)
                                 <= le32_to_cpu(ix[-1].ei_block));
                  if (block < le32_to_cpu(ix->ei_block))
                        break;
                  chix = ix;
            }
            BUG_ON(chix != path->p_idx);
      }
#endif

}

/*
 * ext4_ext_binsearch:
 * binary search for closest extent of the given block
 * the header must be checked before calling this
 */
static void
ext4_ext_binsearch(struct inode *inode, struct ext4_ext_path *path, int block)
{
      struct ext4_extent_header *eh = path->p_hdr;
      struct ext4_extent *r, *l, *m;

      if (eh->eh_entries == 0) {
            /*
             * this leaf is empty:
             * we get such a leaf in split/add case
             */
            return;
      }

      ext_debug("binsearch for %d:  ", block);

      l = EXT_FIRST_EXTENT(eh) + 1;
      r = EXT_LAST_EXTENT(eh);

      while (l <= r) {
            m = l + (r - l) / 2;
            if (block < le32_to_cpu(m->ee_block))
                  r = m - 1;
            else
                  l = m + 1;
            ext_debug("%p(%u):%p(%u):%p(%u) ", l, le32_to_cpu(l->ee_block),
                        m, le32_to_cpu(m->ee_block),
                        r, le32_to_cpu(r->ee_block));
      }

      path->p_ext = l - 1;
      ext_debug("  -> %d:%llu:%d ",
                  le32_to_cpu(path->p_ext->ee_block),
                  ext_pblock(path->p_ext),
                  ext4_ext_get_actual_len(path->p_ext));

#ifdef CHECK_BINSEARCH
      {
            struct ext4_extent *chex, *ex;
            int k;

            chex = ex = EXT_FIRST_EXTENT(eh);
            for (k = 0; k < le16_to_cpu(eh->eh_entries); k++, ex++) {
                  BUG_ON(k && le32_to_cpu(ex->ee_block)
                                <= le32_to_cpu(ex[-1].ee_block));
                  if (block < le32_to_cpu(ex->ee_block))
                        break;
                  chex = ex;
            }
            BUG_ON(chex != path->p_ext);
      }
#endif

}

int ext4_ext_tree_init(handle_t *handle, struct inode *inode)
{
      struct ext4_extent_header *eh;

      eh = ext_inode_hdr(inode);
      eh->eh_depth = 0;
      eh->eh_entries = 0;
      eh->eh_magic = EXT4_EXT_MAGIC;
      eh->eh_max = cpu_to_le16(ext4_ext_space_root(inode));
      ext4_mark_inode_dirty(handle, inode);
      ext4_ext_invalidate_cache(inode);
      return 0;
}

struct ext4_ext_path *
ext4_ext_find_extent(struct inode *inode, int block, struct ext4_ext_path *path)
{
      struct ext4_extent_header *eh;
      struct buffer_head *bh;
      short int depth, i, ppos = 0, alloc = 0;

      eh = ext_inode_hdr(inode);
      depth = ext_depth(inode);
      if (ext4_ext_check_header(inode, eh, depth))
            return ERR_PTR(-EIO);


      /* account possible depth increase */
      if (!path) {
            path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 2),
                        GFP_NOFS);
            if (!path)
                  return ERR_PTR(-ENOMEM);
            alloc = 1;
      }
      path[0].p_hdr = eh;

      i = depth;
      /* walk through the tree */
      while (i) {
            ext_debug("depth %d: num %d, max %d\n",
                    ppos, le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));

            ext4_ext_binsearch_idx(inode, path + ppos, block);
            path[ppos].p_block = idx_pblock(path[ppos].p_idx);
            path[ppos].p_depth = i;
            path[ppos].p_ext = NULL;

            bh = sb_bread(inode->i_sb, path[ppos].p_block);
            if (!bh)
                  goto err;

            eh = ext_block_hdr(bh);
            ppos++;
            BUG_ON(ppos > depth);
            path[ppos].p_bh = bh;
            path[ppos].p_hdr = eh;
            i--;

            if (ext4_ext_check_header(inode, eh, i))
                  goto err;
      }

      path[ppos].p_depth = i;
      path[ppos].p_hdr = eh;
      path[ppos].p_ext = NULL;
      path[ppos].p_idx = NULL;

      /* find extent */
      ext4_ext_binsearch(inode, path + ppos, block);

      ext4_ext_show_path(inode, path);

      return path;

err:
      ext4_ext_drop_refs(path);
      if (alloc)
            kfree(path);
      return ERR_PTR(-EIO);
}

/*
 * ext4_ext_insert_index:
 * insert new index [@logical;@ptr] into the block at @curp;
 * check where to insert: before @curp or after @curp
 */
static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
                        struct ext4_ext_path *curp,
                        int logical, ext4_fsblk_t ptr)
{
      struct ext4_extent_idx *ix;
      int len, err;

      err = ext4_ext_get_access(handle, inode, curp);
      if (err)
            return err;

      BUG_ON(logical == le32_to_cpu(curp->p_idx->ei_block));
      len = EXT_MAX_INDEX(curp->p_hdr) - curp->p_idx;
      if (logical > le32_to_cpu(curp->p_idx->ei_block)) {
            /* insert after */
            if (curp->p_idx != EXT_LAST_INDEX(curp->p_hdr)) {
                  len = (len - 1) * sizeof(struct ext4_extent_idx);
                  len = len < 0 ? 0 : len;
                  ext_debug("insert new index %d after: %llu. "
                              "move %d from 0x%p to 0x%p\n",
                              logical, ptr, len,
                              (curp->p_idx + 1), (curp->p_idx + 2));
                  memmove(curp->p_idx + 2, curp->p_idx + 1, len);
            }
            ix = curp->p_idx + 1;
      } else {
            /* insert before */
            len = len * sizeof(struct ext4_extent_idx);
            len = len < 0 ? 0 : len;
            ext_debug("insert new index %d before: %llu. "
                        "move %d from 0x%p to 0x%p\n",
                        logical, ptr, len,
                        curp->p_idx, (curp->p_idx + 1));
            memmove(curp->p_idx + 1, curp->p_idx, len);
            ix = curp->p_idx;
      }

      ix->ei_block = cpu_to_le32(logical);
      ext4_idx_store_pblock(ix, ptr);
      curp->p_hdr->eh_entries = cpu_to_le16(le16_to_cpu(curp->p_hdr->eh_entries)+1);

      BUG_ON(le16_to_cpu(curp->p_hdr->eh_entries)
                       > le16_to_cpu(curp->p_hdr->eh_max));
      BUG_ON(ix > EXT_LAST_INDEX(curp->p_hdr));

      err = ext4_ext_dirty(handle, inode, curp);
      ext4_std_error(inode->i_sb, err);

      return err;
}

/*
 * ext4_ext_split:
 * inserts new subtree into the path, using free index entry
 * at depth @at:
 * - allocates all needed blocks (new leaf and all intermediate index blocks)
 * - makes decision where to split
 * - moves remaining extents and index entries (right to the split point)
 *   into the newly allocated blocks
 * - initializes subtree
 */
static int ext4_ext_split(handle_t *handle, struct inode *inode,
                        struct ext4_ext_path *path,
                        struct ext4_extent *newext, int at)
{
      struct buffer_head *bh = NULL;
      int depth = ext_depth(inode);
      struct ext4_extent_header *neh;
      struct ext4_extent_idx *fidx;
      struct ext4_extent *ex;
      int i = at, k, m, a;
      ext4_fsblk_t newblock, oldblock;
      __le32 border;
      ext4_fsblk_t *ablocks = NULL; /* array of allocated blocks */
      int err = 0;

      /* make decision: where to split? */
      /* FIXME: now decision is simplest: at current extent */

      /* if current leaf will be split, then we should use
       * border from split point */
      BUG_ON(path[depth].p_ext > EXT_MAX_EXTENT(path[depth].p_hdr));
      if (path[depth].p_ext != EXT_MAX_EXTENT(path[depth].p_hdr)) {
            border = path[depth].p_ext[1].ee_block;
            ext_debug("leaf will be split."
                        " next leaf starts at %d\n",
                          le32_to_cpu(border));
      } else {
            border = newext->ee_block;
            ext_debug("leaf will be added."
                        " next leaf starts at %d\n",
                        le32_to_cpu(border));
      }

      /*
       * If error occurs, then we break processing
       * and mark filesystem read-only. index won't
       * be inserted and tree will be in consistent
       * state. Next mount will repair buffers too.
       */

      /*
       * Get array to track all allocated blocks.
       * We need this to handle errors and free blocks
       * upon them.
       */
      ablocks = kzalloc(sizeof(ext4_fsblk_t) * depth, GFP_NOFS);
      if (!ablocks)
            return -ENOMEM;

      /* allocate all needed blocks */
      ext_debug("allocate %d blocks for indexes/leaf\n", depth - at);
      for (a = 0; a < depth - at; a++) {
            newblock = ext4_ext_new_block(handle, inode, path, newext, &err);
            if (newblock == 0)
                  goto cleanup;
            ablocks[a] = newblock;
      }

      /* initialize new leaf */
      newblock = ablocks[--a];
      BUG_ON(newblock == 0);
      bh = sb_getblk(inode->i_sb, newblock);
      if (!bh) {
            err = -EIO;
            goto cleanup;
      }
      lock_buffer(bh);

      err = ext4_journal_get_create_access(handle, bh);
      if (err)
            goto cleanup;

      neh = ext_block_hdr(bh);
      neh->eh_entries = 0;
      neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode));
      neh->eh_magic = EXT4_EXT_MAGIC;
      neh->eh_depth = 0;
      ex = EXT_FIRST_EXTENT(neh);

      /* move remainder of path[depth] to the new leaf */
      BUG_ON(path[depth].p_hdr->eh_entries != path[depth].p_hdr->eh_max);
      /* start copy from next extent */
      /* TODO: we could do it by single memmove */
      m = 0;
      path[depth].p_ext++;
      while (path[depth].p_ext <=
                  EXT_MAX_EXTENT(path[depth].p_hdr)) {
            ext_debug("move %d:%llu:%d in new leaf %llu\n",
                        le32_to_cpu(path[depth].p_ext->ee_block),
                        ext_pblock(path[depth].p_ext),
                        ext4_ext_get_actual_len(path[depth].p_ext),
                        newblock);
            /*memmove(ex++, path[depth].p_ext++,
                        sizeof(struct ext4_extent));
            neh->eh_entries++;*/
            path[depth].p_ext++;
            m++;
      }
      if (m) {
            memmove(ex, path[depth].p_ext-m, sizeof(struct ext4_extent)*m);
            neh->eh_entries = cpu_to_le16(le16_to_cpu(neh->eh_entries)+m);
      }

      set_buffer_uptodate(bh);
      unlock_buffer(bh);

      err = ext4_journal_dirty_metadata(handle, bh);
      if (err)
            goto cleanup;
      brelse(bh);
      bh = NULL;

      /* correct old leaf */
      if (m) {
            err = ext4_ext_get_access(handle, inode, path + depth);
            if (err)
                  goto cleanup;
            path[depth].p_hdr->eh_entries =
                 cpu_to_le16(le16_to_cpu(path[depth].p_hdr->eh_entries)-m);
            err = ext4_ext_dirty(handle, inode, path + depth);
            if (err)
                  goto cleanup;

      }

      /* create intermediate indexes */
      k = depth - at - 1;
      BUG_ON(k < 0);
      if (k)
            ext_debug("create %d intermediate indices\n", k);
      /* insert new index into current index block */
      /* current depth stored in i var */
      i = depth - 1;
      while (k--) {
            oldblock = newblock;
            newblock = ablocks[--a];
            bh = sb_getblk(inode->i_sb, (ext4_fsblk_t)newblock);
            if (!bh) {
                  err = -EIO;
                  goto cleanup;
            }
            lock_buffer(bh);

            err = ext4_journal_get_create_access(handle, bh);
            if (err)
                  goto cleanup;

            neh = ext_block_hdr(bh);
            neh->eh_entries = cpu_to_le16(1);
            neh->eh_magic = EXT4_EXT_MAGIC;
            neh->eh_max = cpu_to_le16(ext4_ext_space_block_idx(inode));
            neh->eh_depth = cpu_to_le16(depth - i);
            fidx = EXT_FIRST_INDEX(neh);
            fidx->ei_block = border;
            ext4_idx_store_pblock(fidx, oldblock);

            ext_debug("int.index at %d (block %llu): %lu -> %llu\n", i,
                        newblock, (unsigned long) le32_to_cpu(border),
                        oldblock);
            /* copy indexes */
            m = 0;
            path[i].p_idx++;

            ext_debug("cur 0x%p, last 0x%p\n", path[i].p_idx,
                        EXT_MAX_INDEX(path[i].p_hdr));
            BUG_ON(EXT_MAX_INDEX(path[i].p_hdr) !=
                        EXT_LAST_INDEX(path[i].p_hdr));
            while (path[i].p_idx <= EXT_MAX_INDEX(path[i].p_hdr)) {
                  ext_debug("%d: move %d:%llu in new index %llu\n", i,
                              le32_to_cpu(path[i].p_idx->ei_block),
                              idx_pblock(path[i].p_idx),
                              newblock);
                  /*memmove(++fidx, path[i].p_idx++,
                              sizeof(struct ext4_extent_idx));
                  neh->eh_entries++;
                  BUG_ON(neh->eh_entries > neh->eh_max);*/
                  path[i].p_idx++;
                  m++;
            }
            if (m) {
                  memmove(++fidx, path[i].p_idx - m,
                        sizeof(struct ext4_extent_idx) * m);
                  neh->eh_entries =
                        cpu_to_le16(le16_to_cpu(neh->eh_entries) + m);
            }
            set_buffer_uptodate(bh);
            unlock_buffer(bh);

            err = ext4_journal_dirty_metadata(handle, bh);
            if (err)
                  goto cleanup;
            brelse(bh);
            bh = NULL;

            /* correct old index */
            if (m) {
                  err = ext4_ext_get_access(handle, inode, path + i);
                  if (err)
                        goto cleanup;
                  path[i].p_hdr->eh_entries = cpu_to_le16(le16_to_cpu(path[i].p_hdr->eh_entries)-m);
                  err = ext4_ext_dirty(handle, inode, path + i);
                  if (err)
                        goto cleanup;
            }

            i--;
      }

      /* insert new index */
      err = ext4_ext_insert_index(handle, inode, path + at,
                            le32_to_cpu(border), newblock);

cleanup:
      if (bh) {
            if (buffer_locked(bh))
                  unlock_buffer(bh);
            brelse(bh);
      }

      if (err) {
            /* free all allocated blocks in error case */
            for (i = 0; i < depth; i++) {
                  if (!ablocks[i])
                        continue;
                  ext4_free_blocks(handle, inode, ablocks[i], 1);
            }
      }
      kfree(ablocks);

      return err;
}

/*
 * ext4_ext_grow_indepth:
 * implements tree growing procedure:
 * - allocates new block
 * - moves top-level data (index block or leaf) into the new block
 * - initializes new top-level, creating index that points to the
 *   just created block
 */
static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
                              struct ext4_ext_path *path,
                              struct ext4_extent *newext)
{
      struct ext4_ext_path *curp = path;
      struct ext4_extent_header *neh;
      struct ext4_extent_idx *fidx;
      struct buffer_head *bh;
      ext4_fsblk_t newblock;
      int err = 0;

      newblock = ext4_ext_new_block(handle, inode, path, newext, &err);
      if (newblock == 0)
            return err;

      bh = sb_getblk(inode->i_sb, newblock);
      if (!bh) {
            err = -EIO;
            ext4_std_error(inode->i_sb, err);
            return err;
      }
      lock_buffer(bh);

      err = ext4_journal_get_create_access(handle, bh);
      if (err) {
            unlock_buffer(bh);
            goto out;
      }

      /* move top-level index/leaf into new block */
      memmove(bh->b_data, curp->p_hdr, sizeof(EXT4_I(inode)->i_data));

      /* set size of new block */
      neh = ext_block_hdr(bh);
      /* old root could have indexes or leaves
       * so calculate e_max right way */
      if (ext_depth(inode))
        neh->eh_max = cpu_to_le16(ext4_ext_space_block_idx(inode));
      else
        neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode));
      neh->eh_magic = EXT4_EXT_MAGIC;
      set_buffer_uptodate(bh);
      unlock_buffer(bh);

      err = ext4_journal_dirty_metadata(handle, bh);
      if (err)
            goto out;

      /* create index in new top-level index: num,max,pointer */
      err = ext4_ext_get_access(handle, inode, curp);
      if (err)
            goto out;

      curp->p_hdr->eh_magic = EXT4_EXT_MAGIC;
      curp->p_hdr->eh_max = cpu_to_le16(ext4_ext_space_root_idx(inode));
      curp->p_hdr->eh_entries = cpu_to_le16(1);
      curp->p_idx = EXT_FIRST_INDEX(curp->p_hdr);

      if (path[0].p_hdr->eh_depth)
            curp->p_idx->ei_block =
                  EXT_FIRST_INDEX(path[0].p_hdr)->ei_block;
      else
            curp->p_idx->ei_block =
                  EXT_FIRST_EXTENT(path[0].p_hdr)->ee_block;
      ext4_idx_store_pblock(curp->p_idx, newblock);

      neh = ext_inode_hdr(inode);
      fidx = EXT_FIRST_INDEX(neh);
      ext_debug("new root: num %d(%d), lblock %d, ptr %llu\n",
              le16_to_cpu(neh->eh_entries), le16_to_cpu(neh->eh_max),
              le32_to_cpu(fidx->ei_block), idx_pblock(fidx));

      neh->eh_depth = cpu_to_le16(path->p_depth + 1);
      err = ext4_ext_dirty(handle, inode, curp);
out:
      brelse(bh);

      return err;
}

/*
 * ext4_ext_create_new_leaf:
 * finds empty index and adds new leaf.
 * if no free index is found, then it requests in-depth growing.
 */
static int ext4_ext_create_new_leaf(handle_t *handle, struct inode *inode,
                              struct ext4_ext_path *path,
                              struct ext4_extent *newext)
{
      struct ext4_ext_path *curp;
      int depth, i, err = 0;

repeat:
      i = depth = ext_depth(inode);

      /* walk up to the tree and look for free index entry */
      curp = path + depth;
      while (i > 0 && !EXT_HAS_FREE_INDEX(curp)) {
            i--;
            curp--;
      }

      /* we use already allocated block for index block,
       * so subsequent data blocks should be contiguous */
      if (EXT_HAS_FREE_INDEX(curp)) {
            /* if we found index with free entry, then use that
             * entry: create all needed subtree and add new leaf */
            err = ext4_ext_split(handle, inode, path, newext, i);

            /* refill path */
            ext4_ext_drop_refs(path);
            path = ext4_ext_find_extent(inode,
                                  le32_to_cpu(newext->ee_block),
                                  path);
            if (IS_ERR(path))
                  err = PTR_ERR(path);
      } else {
            /* tree is full, time to grow in depth */
            err = ext4_ext_grow_indepth(handle, inode, path, newext);
            if (err)
                  goto out;

            /* refill path */
            ext4_ext_drop_refs(path);
            path = ext4_ext_find_extent(inode,
                                  le32_to_cpu(newext->ee_block),
                                  path);
            if (IS_ERR(path)) {
                  err = PTR_ERR(path);
                  goto out;
            }

            /*
             * only first (depth 0 -> 1) produces free space;
             * in all other cases we have to split the grown tree
             */
            depth = ext_depth(inode);
            if (path[depth].p_hdr->eh_entries == path[depth].p_hdr->eh_max) {
                  /* now we need to split */
                  goto repeat;
            }
      }

out:
      return err;
}

/*
 * ext4_ext_next_allocated_block:
 * returns allocated block in subsequent extent or EXT_MAX_BLOCK.
 * NOTE: it considers block number from index entry as
 * allocated block. Thus, index entries have to be consistent
 * with leaves.
 */
static unsigned long
ext4_ext_next_allocated_block(struct ext4_ext_path *path)
{
      int depth;

      BUG_ON(path == NULL);
      depth = path->p_depth;

      if (depth == 0 && path->p_ext == NULL)
            return EXT_MAX_BLOCK;

      while (depth >= 0) {
            if (depth == path->p_depth) {
                  /* leaf */
                  if (path[depth].p_ext !=
                              EXT_LAST_EXTENT(path[depth].p_hdr))
                    return le32_to_cpu(path[depth].p_ext[1].ee_block);
            } else {
                  /* index */
                  if (path[depth].p_idx !=
                              EXT_LAST_INDEX(path[depth].p_hdr))
                    return le32_to_cpu(path[depth].p_idx[1].ei_block);
            }
            depth--;
      }

      return EXT_MAX_BLOCK;
}

/*
 * ext4_ext_next_leaf_block:
 * returns first allocated block from next leaf or EXT_MAX_BLOCK
 */
static unsigned ext4_ext_next_leaf_block(struct inode *inode,
                              struct ext4_ext_path *path)
{
      int depth;

      BUG_ON(path == NULL);
      depth = path->p_depth;

      /* zero-tree has no leaf blocks at all */
      if (depth == 0)
            return EXT_MAX_BLOCK;

      /* go to index block */
      depth--;

      while (depth >= 0) {
            if (path[depth].p_idx !=
                        EXT_LAST_INDEX(path[depth].p_hdr))
              return le32_to_cpu(path[depth].p_idx[1].ei_block);
            depth--;
      }

      return EXT_MAX_BLOCK;
}

/*
 * ext4_ext_correct_indexes:
 * if leaf gets modified and modified extent is first in the leaf,
 * then we have to correct all indexes above.
 * TODO: do we need to correct tree in all cases?
 */
int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode,
                        struct ext4_ext_path *path)
{
      struct ext4_extent_header *eh;
      int depth = ext_depth(inode);
      struct ext4_extent *ex;
      __le32 border;
      int k, err = 0;

      eh = path[depth].p_hdr;
      ex = path[depth].p_ext;
      BUG_ON(ex == NULL);
      BUG_ON(eh == NULL);

      if (depth == 0) {
            /* there is no tree at all */
            return 0;
      }

      if (ex != EXT_FIRST_EXTENT(eh)) {
            /* we correct tree if first leaf got modified only */
            return 0;
      }

      /*
       * TODO: we need correction if border is smaller than current one
       */
      k = depth - 1;
      border = path[depth].p_ext->ee_block;
      err = ext4_ext_get_access(handle, inode, path + k);
      if (err)
            return err;
      path[k].p_idx->ei_block = border;
      err = ext4_ext_dirty(handle, inode, path + k);
      if (err)
            return err;

      while (k--) {
            /* change all left-side indexes */
            if (path[k+1].p_idx != EXT_FIRST_INDEX(path[k+1].p_hdr))
                  break;
            err = ext4_ext_get_access(handle, inode, path + k);
            if (err)
                  break;
            path[k].p_idx->ei_block = border;
            err = ext4_ext_dirty(handle, inode, path + k);
            if (err)
                  break;
      }

      return err;
}

static int
ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
                        struct ext4_extent *ex2)
{
      unsigned short ext1_ee_len, ext2_ee_len, max_len;

      /*
       * Make sure that either both extents are uninitialized, or
       * both are _not_.
       */
      if (ext4_ext_is_uninitialized(ex1) ^ ext4_ext_is_uninitialized(ex2))
            return 0;

      if (ext4_ext_is_uninitialized(ex1))
            max_len = EXT_UNINIT_MAX_LEN;
      else
            max_len = EXT_INIT_MAX_LEN;

      ext1_ee_len = ext4_ext_get_actual_len(ex1);
      ext2_ee_len = ext4_ext_get_actual_len(ex2);

      if (le32_to_cpu(ex1->ee_block) + ext1_ee_len !=
                  le32_to_cpu(ex2->ee_block))
            return 0;

      /*
       * To allow future support for preallocated extents to be added
       * as an RO_COMPAT feature, refuse to merge to extents if
       * this can result in the top bit of ee_len being set.
       */
      if (ext1_ee_len + ext2_ee_len > max_len)
            return 0;
#ifdef AGGRESSIVE_TEST
      if (le16_to_cpu(ex1->ee_len) >= 4)
            return 0;
#endif

      if (ext_pblock(ex1) + ext1_ee_len == ext_pblock(ex2))
            return 1;
      return 0;
}

/*
 * This function tries to merge the "ex" extent to the next extent in the tree.
 * It always tries to merge towards right. If you want to merge towards
 * left, pass "ex - 1" as argument instead of "ex".
 * Returns 0 if the extents (ex and ex+1) were _not_ merged and returns
 * 1 if they got merged.
 */
int ext4_ext_try_to_merge(struct inode *inode,
                    struct ext4_ext_path *path,
                    struct ext4_extent *ex)
{
      struct ext4_extent_header *eh;
      unsigned int depth, len;
      int merge_done = 0;
      int uninitialized = 0;

      depth = ext_depth(inode);
      BUG_ON(path[depth].p_hdr == NULL);
      eh = path[depth].p_hdr;

      while (ex < EXT_LAST_EXTENT(eh)) {
            if (!ext4_can_extents_be_merged(inode, ex, ex + 1))
                  break;
            /* merge with next extent! */
            if (ext4_ext_is_uninitialized(ex))
                  uninitialized = 1;
            ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
                        + ext4_ext_get_actual_len(ex + 1));
            if (uninitialized)
                  ext4_ext_mark_uninitialized(ex);

            if (ex + 1 < EXT_LAST_EXTENT(eh)) {
                  len = (EXT_LAST_EXTENT(eh) - ex - 1)
                        * sizeof(struct ext4_extent);
                  memmove(ex + 1, ex + 2, len);
            }
            eh->eh_entries = cpu_to_le16(le16_to_cpu(eh->eh_entries) - 1);
            merge_done = 1;
            WARN_ON(eh->eh_entries == 0);
            if (!eh->eh_entries)
                  ext4_error(inode->i_sb, "ext4_ext_try_to_merge",
                     "inode#%lu, eh->eh_entries = 0!", inode->i_ino);
      }

      return merge_done;
}

/*
 * check if a portion of the "newext" extent overlaps with an
 * existing extent.
 *
 * If there is an overlap discovered, it updates the length of the newext
 * such that there will be no overlap, and then returns 1.
 * If there is no overlap found, it returns 0.
 */
unsigned int ext4_ext_check_overlap(struct inode *inode,
                            struct ext4_extent *newext,
                            struct ext4_ext_path *path)
{
      unsigned long b1, b2;
      unsigned int depth, len1;
      unsigned int ret = 0;

      b1 = le32_to_cpu(newext->ee_block);
      len1 = ext4_ext_get_actual_len(newext);
      depth = ext_depth(inode);
      if (!path[depth].p_ext)
            goto out;
      b2 = le32_to_cpu(path[depth].p_ext->ee_block);

      /*
       * get the next allocated block if the extent in the path
       * is before the requested block(s) 
       */
      if (b2 < b1) {
            b2 = ext4_ext_next_allocated_block(path);
            if (b2 == EXT_MAX_BLOCK)
                  goto out;
      }

      /* check for wrap through zero */
      if (b1 + len1 < b1) {
            len1 = EXT_MAX_BLOCK - b1;
            newext->ee_len = cpu_to_le16(len1);
            ret = 1;
      }

      /* check for overlap */
      if (b1 + len1 > b2) {
            newext->ee_len = cpu_to_le16(b2 - b1);
            ret = 1;
      }
out:
      return ret;
}

/*
 * ext4_ext_insert_extent:
 * tries to merge requsted extent into the existing extent or
 * inserts requested extent as new one into the tree,
 * creating new leaf in the no-space case.
 */
int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
                        struct ext4_ext_path *path,
                        struct ext4_extent *newext)
{
      struct ext4_extent_header * eh;
      struct ext4_extent *ex, *fex;
      struct ext4_extent *nearex; /* nearest extent */
      struct ext4_ext_path *npath = NULL;
      int depth, len, err, next;
      unsigned uninitialized = 0;

      BUG_ON(ext4_ext_get_actual_len(newext) == 0);
      depth = ext_depth(inode);
      ex = path[depth].p_ext;
      BUG_ON(path[depth].p_hdr == NULL);

      /* try to insert block into found extent and return */
      if (ex && ext4_can_extents_be_merged(inode, ex, newext)) {
            ext_debug("append %d block to %d:%d (from %llu)\n",
                        ext4_ext_get_actual_len(newext),
                        le32_to_cpu(ex->ee_block),
                        ext4_ext_get_actual_len(ex), ext_pblock(ex));
            err = ext4_ext_get_access(handle, inode, path + depth);
            if (err)
                  return err;

            /*
             * ext4_can_extents_be_merged should have checked that either
             * both extents are uninitialized, or both aren't. Thus we
             * need to check only one of them here.
             */
            if (ext4_ext_is_uninitialized(ex))
                  uninitialized = 1;
            ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
                              + ext4_ext_get_actual_len(newext));
            if (uninitialized)
                  ext4_ext_mark_uninitialized(ex);
            eh = path[depth].p_hdr;
            nearex = ex;
            goto merge;
      }

repeat:
      depth = ext_depth(inode);
      eh = path[depth].p_hdr;
      if (le16_to_cpu(eh->eh_entries) < le16_to_cpu(eh->eh_max))
            goto has_space;

      /* probably next leaf has space for us? */
      fex = EXT_LAST_EXTENT(eh);
      next = ext4_ext_next_leaf_block(inode, path);
      if (le32_to_cpu(newext->ee_block) > le32_to_cpu(fex->ee_block)
          && next != EXT_MAX_BLOCK) {
            ext_debug("next leaf block - %d\n", next);
            BUG_ON(npath != NULL);
            npath = ext4_ext_find_extent(inode, next, NULL);
            if (IS_ERR(npath))
                  return PTR_ERR(npath);
            BUG_ON(npath->p_depth != path->p_depth);
            eh = npath[depth].p_hdr;
            if (le16_to_cpu(eh->eh_entries) < le16_to_cpu(eh->eh_max)) {
                  ext_debug("next leaf isnt full(%d)\n",
                          le16_to_cpu(eh->eh_entries));
                  path = npath;
                  goto repeat;
            }
            ext_debug("next leaf has no free space(%d,%d)\n",
                    le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));
      }

      /*
       * There is no free space in the found leaf.
       * We're gonna add a new leaf in the tree.
       */
      err = ext4_ext_create_new_leaf(handle, inode, path, newext);
      if (err)
            goto cleanup;
      depth = ext_depth(inode);
      eh = path[depth].p_hdr;

has_space:
      nearex = path[depth].p_ext;

      err = ext4_ext_get_access(handle, inode, path + depth);
      if (err)
            goto cleanup;

      if (!nearex) {
            /* there is no extent in this leaf, create first one */
            ext_debug("first extent in the leaf: %d:%llu:%d\n",
                        le32_to_cpu(newext->ee_block),
                        ext_pblock(newext),
                        ext4_ext_get_actual_len(newext));
            path[depth].p_ext = EXT_FIRST_EXTENT(eh);
      } else if (le32_to_cpu(newext->ee_block)
                     > le32_to_cpu(nearex->ee_block)) {
/*          BUG_ON(newext->ee_block == nearex->ee_block); */
            if (nearex != EXT_LAST_EXTENT(eh)) {
                  len = EXT_MAX_EXTENT(eh) - nearex;
                  len = (len - 1) * sizeof(struct ext4_extent);
                  len = len < 0 ? 0 : len;
                  ext_debug("insert %d:%llu:%d after: nearest 0x%p, "
                              "move %d from 0x%p to 0x%p\n",
                              le32_to_cpu(newext->ee_block),
                              ext_pblock(newext),
                              ext4_ext_get_actual_len(newext),
                              nearex, len, nearex + 1, nearex + 2);
                  memmove(nearex + 2, nearex + 1, len);
            }
            path[depth].p_ext = nearex + 1;
      } else {
            BUG_ON(newext->ee_block == nearex->ee_block);
            len = (EXT_MAX_EXTENT(eh) - nearex) * sizeof(struct ext4_extent);
            len = len < 0 ? 0 : len;
            ext_debug("insert %d:%llu:%d before: nearest 0x%p, "
                        "move %d from 0x%p to 0x%p\n",
                        le32_to_cpu(newext->ee_block),
                        ext_pblock(newext),
                        ext4_ext_get_actual_len(newext),
                        nearex, len, nearex + 1, nearex + 2);
            memmove(nearex + 1, nearex, len);
            path[depth].p_ext = nearex;
      }

      eh->eh_entries = cpu_to_le16(le16_to_cpu(eh->eh_entries)+1);
      nearex = path[depth].p_ext;
      nearex->ee_block = newext->ee_block;
      ext4_ext_store_pblock(nearex, ext_pblock(newext));
      nearex->ee_len = newext->ee_len;

merge:
      /* try to merge extents to the right */
      ext4_ext_try_to_merge(inode, path, nearex);

      /* try to merge extents to the left */

      /* time to correct all indexes above */
      err = ext4_ext_correct_indexes(handle, inode, path);
      if (err)
            goto cleanup;

      err = ext4_ext_dirty(handle, inode, path + depth);

cleanup:
      if (npath) {
            ext4_ext_drop_refs(npath);
            kfree(npath);
      }
      ext4_ext_tree_changed(inode);
      ext4_ext_invalidate_cache(inode);
      return err;
}

int ext4_ext_walk_space(struct inode *inode, unsigned long block,
                  unsigned long num, ext_prepare_callback func,
                  void *cbdata)
{
      struct ext4_ext_path *path = NULL;
      struct ext4_ext_cache cbex;
      struct ext4_extent *ex;
      unsigned long next, start = 0, end = 0;
      unsigned long last = block + num;
      int depth, exists, err = 0;

      BUG_ON(func == NULL);
      BUG_ON(inode == NULL);

      while (block < last && block != EXT_MAX_BLOCK) {
            num = last - block;
            /* find extent for this block */
            path = ext4_ext_find_extent(inode, block, path);
            if (IS_ERR(path)) {
                  err = PTR_ERR(path);
                  path = NULL;
                  break;
            }

            depth = ext_depth(inode);
            BUG_ON(path[depth].p_hdr == NULL);
            ex = path[depth].p_ext;
            next = ext4_ext_next_allocated_block(path);

            exists = 0;
            if (!ex) {
                  /* there is no extent yet, so try to allocate
                   * all requested space */
                  start = block;
                  end = block + num;
            } else if (le32_to_cpu(ex->ee_block) > block) {
                  /* need to allocate space before found extent */
                  start = block;
                  end = le32_to_cpu(ex->ee_block);
                  if (block + num < end)
                        end = block + num;
            } else if (block >= le32_to_cpu(ex->ee_block)
                              + ext4_ext_get_actual_len(ex)) {
                  /* need to allocate space after found extent */
                  start = block;
                  end = block + num;
                  if (end >= next)
                        end = next;
            } else if (block >= le32_to_cpu(ex->ee_block)) {
                  /*
                   * some part of requested space is covered
                   * by found extent
                   */
                  start = block;
                  end = le32_to_cpu(ex->ee_block)
                        + ext4_ext_get_actual_len(ex);
                  if (block + num < end)
                        end = block + num;
                  exists = 1;
            } else {
                  BUG();
            }
            BUG_ON(end <= start);

            if (!exists) {
                  cbex.ec_block = start;
                  cbex.ec_len = end - start;
                  cbex.ec_start = 0;
                  cbex.ec_type = EXT4_EXT_CACHE_GAP;
            } else {
                  cbex.ec_block = le32_to_cpu(ex->ee_block);
                  cbex.ec_len = ext4_ext_get_actual_len(ex);
                  cbex.ec_start = ext_pblock(ex);
                  cbex.ec_type = EXT4_EXT_CACHE_EXTENT;
            }

            BUG_ON(cbex.ec_len == 0);
            err = func(inode, path, &cbex, cbdata);
            ext4_ext_drop_refs(path);

            if (err < 0)
                  break;
            if (err == EXT_REPEAT)
                  continue;
            else if (err == EXT_BREAK) {
                  err = 0;
                  break;
            }

            if (ext_depth(inode) != depth) {
                  /* depth was changed. we have to realloc path */
                  kfree(path);
                  path = NULL;
            }

            block = cbex.ec_block + cbex.ec_len;
      }

      if (path) {
            ext4_ext_drop_refs(path);
            kfree(path);
      }

      return err;
}

static void
ext4_ext_put_in_cache(struct inode *inode, __u32 block,
                  __u32 len, ext4_fsblk_t start, int type)
{
      struct ext4_ext_cache *cex;
      BUG_ON(len == 0);
      cex = &EXT4_I(inode)->i_cached_extent;
      cex->ec_type = type;
      cex->ec_block = block;
      cex->ec_len = len;
      cex->ec_start = start;
}

/*
 * ext4_ext_put_gap_in_cache:
 * calculate boundaries of the gap that the requested block fits into
 * and cache this gap
 */
static void
ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
                        unsigned long block)
{
      int depth = ext_depth(inode);
      unsigned long lblock, len;
      struct ext4_extent *ex;

      ex = path[depth].p_ext;
      if (ex == NULL) {
            /* there is no extent yet, so gap is [0;-] */
            lblock = 0;
            len = EXT_MAX_BLOCK;
            ext_debug("cache gap(whole file):");
      } else if (block < le32_to_cpu(ex->ee_block)) {
            lblock = block;
            len = le32_to_cpu(ex->ee_block) - block;
            ext_debug("cache gap(before): %lu [%lu:%lu]",
                        (unsigned long) block,
                        (unsigned long) le32_to_cpu(ex->ee_block),
                        (unsigned long) ext4_ext_get_actual_len(ex));
      } else if (block >= le32_to_cpu(ex->ee_block)
                  + ext4_ext_get_actual_len(ex)) {
            lblock = le32_to_cpu(ex->ee_block)
                  + ext4_ext_get_actual_len(ex);
            len = ext4_ext_next_allocated_block(path);
            ext_debug("cache gap(after): [%lu:%lu] %lu",
                        (unsigned long) le32_to_cpu(ex->ee_block),
                        (unsigned long) ext4_ext_get_actual_len(ex),
                        (unsigned long) block);
            BUG_ON(len == lblock);
            len = len - lblock;
      } else {
            lblock = len = 0;
            BUG();
      }

      ext_debug(" -> %lu:%lu\n", (unsigned long) lblock, len);
      ext4_ext_put_in_cache(inode, lblock, len, 0, EXT4_EXT_CACHE_GAP);
}

static int
ext4_ext_in_cache(struct inode *inode, unsigned long block,
                  struct ext4_extent *ex)
{
      struct ext4_ext_cache *cex;

      cex = &EXT4_I(inode)->i_cached_extent;

      /* has cache valid data? */
      if (cex->ec_type == EXT4_EXT_CACHE_NO)
            return EXT4_EXT_CACHE_NO;

      BUG_ON(cex->ec_type != EXT4_EXT_CACHE_GAP &&
                  cex->ec_type != EXT4_EXT_CACHE_EXTENT);
      if (block >= cex->ec_block && block < cex->ec_block + cex->ec_len) {
            ex->ee_block = cpu_to_le32(cex->ec_block);
            ext4_ext_store_pblock(ex, cex->ec_start);
            ex->ee_len = cpu_to_le16(cex->ec_len);
            ext_debug("%lu cached by %lu:%lu:%llu\n",
                        (unsigned long) block,
                        (unsigned long) cex->ec_block,
                        (unsigned long) cex->ec_len,
                        cex->ec_start);
            return cex->ec_type;
      }

      /* not in cache */
      return EXT4_EXT_CACHE_NO;
}

/*
 * ext4_ext_rm_idx:
 * removes index from the index block.
 * It's used in truncate case only, thus all requests are for
 * last index in the block only.
 */
int ext4_ext_rm_idx(handle_t *handle, struct inode *inode,
                  struct ext4_ext_path *path)
{
      struct buffer_head *bh;
      int err;
      ext4_fsblk_t leaf;

      /* free index block */
      path--;
      leaf = idx_pblock(path->p_idx);
      BUG_ON(path->p_hdr->eh_entries == 0);
      err = ext4_ext_get_access(handle, inode, path);
      if (err)
            return err;
      path->p_hdr->eh_entries = cpu_to_le16(le16_to_cpu(path->p_hdr->eh_entries)-1);
      err = ext4_ext_dirty(handle, inode, path);
      if (err)
            return err;
      ext_debug("index is empty, remove it, free block %llu\n", leaf);
      bh = sb_find_get_block(inode->i_sb, leaf);
      ext4_forget(handle, 1, inode, bh, leaf);
      ext4_free_blocks(handle, inode, leaf, 1);
      return err;
}

/*
 * ext4_ext_calc_credits_for_insert:
 * This routine returns max. credits that the extent tree can consume.
 * It should be OK for low-performance paths like ->writepage()
 * To allow many writing processes to fit into a single transaction,
 * the caller should calculate credits under truncate_mutex and
 * pass the actual path.
 */
int ext4_ext_calc_credits_for_insert(struct inode *inode,
                                    struct ext4_ext_path *path)
{
      int depth, needed;

      if (path) {
            /* probably there is space in leaf? */
            depth = ext_depth(inode);
            if (le16_to_cpu(path[depth].p_hdr->eh_entries)
                        < le16_to_cpu(path[depth].p_hdr->eh_max))
                  return 1;
      }

      /*
       * given 32-bit logical block (4294967296 blocks), max. tree
       * can be 4 levels in depth -- 4 * 340^4 == 53453440000.
       * Let's also add one more level for imbalance.
       */
      depth = 5;

      /* allocation of new data block(s) */
      needed = 2;

      /*
       * tree can be full, so it would need to grow in depth:
       * we need one credit to modify old root, credits for
       * new root will be added in split accounting
       */
      needed += 1;

      /*
       * Index split can happen, we would need:
       *    allocate intermediate indexes (bitmap + group)
       *  + change two blocks at each level, but root (already included)
       */
      needed += (depth * 2) + (depth * 2);

      /* any allocation modifies superblock */
      needed += 1;

      return needed;
}

static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
                        struct ext4_extent *ex,
                        unsigned long from, unsigned long to)
{
      struct buffer_head *bh;
      unsigned short ee_len =  ext4_ext_get_actual_len(ex);
      int i;

#ifdef EXTENTS_STATS
      {
            struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
            spin_lock(&sbi->s_ext_stats_lock);
            sbi->s_ext_blocks += ee_len;
            sbi->s_ext_extents++;
            if (ee_len < sbi->s_ext_min)
                  sbi->s_ext_min = ee_len;
            if (ee_len > sbi->s_ext_max)
                  sbi->s_ext_max = ee_len;
            if (ext_depth(inode) > sbi->s_depth_max)
                  sbi->s_depth_max = ext_depth(inode);
            spin_unlock(&sbi->s_ext_stats_lock);
      }
#endif
      if (from >= le32_to_cpu(ex->ee_block)
          && to == le32_to_cpu(ex->ee_block) + ee_len - 1) {
            /* tail removal */
            unsigned long num;
            ext4_fsblk_t start;
            num = le32_to_cpu(ex->ee_block) + ee_len - from;
            start = ext_pblock(ex) + ee_len - num;
            ext_debug("free last %lu blocks starting %llu\n", num, start);
            for (i = 0; i < num; i++) {
                  bh = sb_find_get_block(inode->i_sb, start + i);
                  ext4_forget(handle, 0, inode, bh, start + i);
            }
            ext4_free_blocks(handle, inode, start, num);
      } else if (from == le32_to_cpu(ex->ee_block)
               && to <= le32_to_cpu(ex->ee_block) + ee_len - 1) {
            printk("strange request: removal %lu-%lu from %u:%u\n",
                  from, to, le32_to_cpu(ex->ee_block), ee_len);
      } else {
            printk("strange request: removal(2) %lu-%lu from %u:%u\n",
                  from, to, le32_to_cpu(ex->ee_block), ee_len);
      }
      return 0;
}

static int
ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
            struct ext4_ext_path *path, unsigned long start)
{
      int err = 0, correct_index = 0;
      int depth = ext_depth(inode), credits;
      struct ext4_extent_header *eh;
      unsigned a, b, block, num;
      unsigned long ex_ee_block;
      unsigned short ex_ee_len;
      unsigned uninitialized = 0;
      struct ext4_extent *ex;

      /* the header must be checked already in ext4_ext_remove_space() */
      ext_debug("truncate since %lu in leaf\n", start);
      if (!path[depth].p_hdr)
            path[depth].p_hdr = ext_block_hdr(path[depth].p_bh);
      eh = path[depth].p_hdr;
      BUG_ON(eh == NULL);

      /* find where to start removing */
      ex = EXT_LAST_EXTENT(eh);

      ex_ee_block = le32_to_cpu(ex->ee_block);
      if (ext4_ext_is_uninitialized(ex))
            uninitialized = 1;
      ex_ee_len = ext4_ext_get_actual_len(ex);

      while (ex >= EXT_FIRST_EXTENT(eh) &&
                  ex_ee_block + ex_ee_len > start) {
            ext_debug("remove ext %lu:%u\n", ex_ee_block, ex_ee_len);
            path[depth].p_ext = ex;

            a = ex_ee_block > start ? ex_ee_block : start;
            b = ex_ee_block + ex_ee_len - 1 < EXT_MAX_BLOCK ?
                  ex_ee_block + ex_ee_len - 1 : EXT_MAX_BLOCK;

            ext_debug("  border %u:%u\n", a, b);

            if (a != ex_ee_block && b != ex_ee_block + ex_ee_len - 1) {
                  block = 0;
                  num = 0;
                  BUG();
            } else if (a != ex_ee_block) {
                  /* remove tail of the extent */
                  block = ex_ee_block;
                  num = a - block;
            } else if (b != ex_ee_block + ex_ee_len - 1) {
                  /* remove head of the extent */
                  block = a;
                  num = b - a;
                  /* there is no "make a hole" API yet */
                  BUG();
            } else {
                  /* remove whole extent: excellent! */
                  block = ex_ee_block;
                  num = 0;
                  BUG_ON(a != ex_ee_block);
                  BUG_ON(b != ex_ee_block + ex_ee_len - 1);
            }

            /* at present, extent can't cross block group: */
            /* leaf + bitmap + group desc + sb + inode */
            credits = 5;
            if (ex == EXT_FIRST_EXTENT(eh)) {
                  correct_index = 1;
                  credits += (ext_depth(inode)) + 1;
            }
#ifdef CONFIG_QUOTA
            credits += 2 * EXT4_QUOTA_TRANS_BLOCKS(inode->i_sb);
#endif

            handle = ext4_ext_journal_restart(handle, credits);
            if (IS_ERR(handle)) {
                  err = PTR_ERR(handle);
                  goto out;
            }

            err = ext4_ext_get_access(handle, inode, path + depth);
            if (err)
                  goto out;

            err = ext4_remove_blocks(handle, inode, ex, a, b);
            if (err)
                  goto out;

            if (num == 0) {
                  /* this extent is removed; mark slot entirely unused */
                  ext4_ext_store_pblock(ex, 0);
                  eh->eh_entries = cpu_to_le16(le16_to_cpu(eh->eh_entries)-1);
            }

            ex->ee_block = cpu_to_le32(block);
            ex->ee_len = cpu_to_le16(num);
            /*
             * Do not mark uninitialized if all the blocks in the
             * extent have been removed.
             */
            if (uninitialized && num)
                  ext4_ext_mark_uninitialized(ex);

            err = ext4_ext_dirty(handle, inode, path + depth);
            if (err)
                  goto out;

            ext_debug("new extent: %u:%u:%llu\n", block, num,
                        ext_pblock(ex));
            ex--;
            ex_ee_block = le32_to_cpu(ex->ee_block);
            ex_ee_len = ext4_ext_get_actual_len(ex);
      }

      if (correct_index && eh->eh_entries)
            err = ext4_ext_correct_indexes(handle, inode, path);

      /* if this leaf is free, then we should
       * remove it from index block above */
      if (err == 0 && eh->eh_entries == 0 && path[depth].p_bh != NULL)
            err = ext4_ext_rm_idx(handle, inode, path + depth);

out:
      return err;
}

/*
 * ext4_ext_more_to_rm:
 * returns 1 if current index has to be freed (even partial)
 */
static int
ext4_ext_more_to_rm(struct ext4_ext_path *path)
{
      BUG_ON(path->p_idx == NULL);

      if (path->p_idx < EXT_FIRST_INDEX(path->p_hdr))
            return 0;

      /*
       * if truncate on deeper level happened, it wasn't partial,
       * so we have to consider current index for truncation
       */
      if (le16_to_cpu(path->p_hdr->eh_entries) == path->p_block)
            return 0;
      return 1;
}

int ext4_ext_remove_space(struct inode *inode, unsigned long start)
{
      struct super_block *sb = inode->i_sb;
      int depth = ext_depth(inode);
      struct ext4_ext_path *path;
      handle_t *handle;
      int i = 0, err = 0;

      ext_debug("truncate since %lu\n", start);

      /* probably first extent we're gonna free will be last in block */
      handle = ext4_journal_start(inode, depth + 1);
      if (IS_ERR(handle))
            return PTR_ERR(handle);

      ext4_ext_invalidate_cache(inode);

      /*
       * We start scanning from right side, freeing all the blocks
       * after i_size and walking into the tree depth-wise.
       */
      path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 1), GFP_KERNEL);
      if (path == NULL) {
            ext4_journal_stop(handle);
            return -ENOMEM;
      }
      path[0].p_hdr = ext_inode_hdr(inode);
      if (ext4_ext_check_header(inode, path[0].p_hdr, depth)) {
            err = -EIO;
            goto out;
      }
      path[0].p_depth = depth;

      while (i >= 0 && err == 0) {
            if (i == depth) {
                  /* this is leaf block */
                  err = ext4_ext_rm_leaf(handle, inode, path, start);
                  /* root level has p_bh == NULL, brelse() eats this */
                  brelse(path[i].p_bh);
                  path[i].p_bh = NULL;
                  i--;
                  continue;
            }

            /* this is index block */
            if (!path[i].p_hdr) {
                  ext_debug("initialize header\n");
                  path[i].p_hdr = ext_block_hdr(path[i].p_bh);
            }

            if (!path[i].p_idx) {
                  /* this level hasn't been touched yet */
                  path[i].p_idx = EXT_LAST_INDEX(path[i].p_hdr);
                  path[i].p_block = le16_to_cpu(path[i].p_hdr->eh_entries)+1;
                  ext_debug("init index ptr: hdr 0x%p, num %d\n",
                          path[i].p_hdr,
                          le16_to_cpu(path[i].p_hdr->eh_entries));
            } else {
                  /* we were already here, see at next index */
                  path[i].p_idx--;
            }

            ext_debug("level %d - index, first 0x%p, cur 0x%p\n",
                        i, EXT_FIRST_INDEX(path[i].p_hdr),
                        path[i].p_idx);
            if (ext4_ext_more_to_rm(path + i)) {
                  struct buffer_head *bh;
                  /* go to the next level */
                  ext_debug("move to level %d (block %llu)\n",
                          i + 1, idx_pblock(path[i].p_idx));
                  memset(path + i + 1, 0, sizeof(*path));
                  bh = sb_bread(sb, idx_pblock(path[i].p_idx));
                  if (!bh) {
                        /* should we reset i_size? */
                        err = -EIO;
                        break;
                  }
                  if (WARN_ON(i + 1 > depth)) {
                        err = -EIO;
                        break;
                  }
                  if (ext4_ext_check_header(inode, ext_block_hdr(bh),
                                          depth - i - 1)) {
                        err = -EIO;
                        break;
                  }
                  path[i + 1].p_bh = bh;

                  /* save actual number of indexes since this
                   * number is changed at the next iteration */
                  path[i].p_block = le16_to_cpu(path[i].p_hdr->eh_entries);
                  i++;
            } else {
                  /* we finished processing this index, go up */
                  if (path[i].p_hdr->eh_entries == 0 && i > 0) {
                        /* index is empty, remove it;
                         * handle must be already prepared by the
                         * truncatei_leaf() */
                        err = ext4_ext_rm_idx(handle, inode, path + i);
                  }
                  /* root level has p_bh == NULL, brelse() eats this */
                  brelse(path[i].p_bh);
                  path[i].p_bh = NULL;
                  i--;
                  ext_debug("return to level %d\n", i);
            }
      }

      /* TODO: flexible tree reduction should be here */
      if (path->p_hdr->eh_entries == 0) {
            /*
             * truncate to zero freed all the tree,
             * so we need to correct eh_depth
             */
            err = ext4_ext_get_access(handle, inode, path);
            if (err == 0) {
                  ext_inode_hdr(inode)->eh_depth = 0;
                  ext_inode_hdr(inode)->eh_max =
                        cpu_to_le16(ext4_ext_space_root(inode));
                  err = ext4_ext_dirty(handle, inode, path);
            }
      }
out:
      ext4_ext_tree_changed(inode);
      ext4_ext_drop_refs(path);
      kfree(path);
      ext4_journal_stop(handle);

      return err;
}

/*
 * called at mount time
 */
void ext4_ext_init(struct super_block *sb)
{
      /*
       * possible initialization would be here
       */

      if (test_opt(sb, EXTENTS)) {
            printk("EXT4-fs: file extents enabled");
#ifdef AGGRESSIVE_TEST
            printk(", aggressive tests");
#endif
#ifdef CHECK_BINSEARCH
            printk(", check binsearch");
#endif
#ifdef EXTENTS_STATS
            printk(", stats");
#endif
            printk("\n");
#ifdef EXTENTS_STATS
            spin_lock_init(&EXT4_SB(sb)->s_ext_stats_lock);
            EXT4_SB(sb)->s_ext_min = 1 << 30;
            EXT4_SB(sb)->s_ext_max = 0;
#endif
      }
}

/*
 * called at umount time
 */
void ext4_ext_release(struct super_block *sb)
{
      if (!test_opt(sb, EXTENTS))
            return;

#ifdef EXTENTS_STATS
      if (EXT4_SB(sb)->s_ext_blocks && EXT4_SB(sb)->s_ext_extents) {
            struct ext4_sb_info *sbi = EXT4_SB(sb);
            printk(KERN_ERR "EXT4-fs: %lu blocks in %lu extents (%lu ave)\n",
                  sbi->s_ext_blocks, sbi->s_ext_extents,
                  sbi->s_ext_blocks / sbi->s_ext_extents);
            printk(KERN_ERR "EXT4-fs: extents: %lu min, %lu max, max depth %lu\n",
                  sbi->s_ext_min, sbi->s_ext_max, sbi->s_depth_max);
      }
#endif
}

/*
 * This function is called by ext4_ext_get_blocks() if someone tries to write
 * to an uninitialized extent. It may result in splitting the uninitialized
 * extent into multiple extents (upto three - one initialized and two
 * uninitialized).
 * There are three possibilities:
 *   a> There is no split required: Entire extent should be initialized
 *   b> Splits in two extents: Write is happening at either end of the extent
 *   c> Splits in three extents: Somone is writing in middle of the extent
 */
int ext4_ext_convert_to_initialized(handle_t *handle, struct inode *inode,
                              struct ext4_ext_path *path,
                              ext4_fsblk_t iblock,
                              unsigned long max_blocks)
{
      struct ext4_extent *ex, newex;
      struct ext4_extent *ex1 = NULL;
      struct ext4_extent *ex2 = NULL;
      struct ext4_extent *ex3 = NULL;
      struct ext4_extent_header *eh;
      unsigned int allocated, ee_block, ee_len, depth;
      ext4_fsblk_t newblock;
      int err = 0;
      int ret = 0;

      depth = ext_depth(inode);
      eh = path[depth].p_hdr;
      ex = path[depth].p_ext;
      ee_block = le32_to_cpu(ex->ee_block);
      ee_len = ext4_ext_get_actual_len(ex);
      allocated = ee_len - (iblock - ee_block);
      newblock = iblock - ee_block + ext_pblock(ex);
      ex2 = ex;

      /* ex1: ee_block to iblock - 1 : uninitialized */
      if (iblock > ee_block) {
            ex1 = ex;
            ex1->ee_len = cpu_to_le16(iblock - ee_block);
            ext4_ext_mark_uninitialized(ex1);
            ex2 = &newex;
      }
      /*
       * for sanity, update the length of the ex2 extent before
       * we insert ex3, if ex1 is NULL. This is to avoid temporary
       * overlap of blocks.
       */
      if (!ex1 && allocated > max_blocks)
            ex2->ee_len = cpu_to_le16(max_blocks);
      /* ex3: to ee_block + ee_len : uninitialised */
      if (allocated > max_blocks) {
            unsigned int newdepth;
            ex3 = &newex;
            ex3->ee_block = cpu_to_le32(iblock + max_blocks);
            ext4_ext_store_pblock(ex3, newblock + max_blocks);
            ex3->ee_len = cpu_to_le16(allocated - max_blocks);
            ext4_ext_mark_uninitialized(ex3);
            err = ext4_ext_insert_extent(handle, inode, path, ex3);
            if (err)
                  goto out;
            /*
             * The depth, and hence eh & ex might change
             * as part of the insert above.
             */
            newdepth = ext_depth(inode);
            if (newdepth != depth) {
                  depth = newdepth;
                  path = ext4_ext_find_extent(inode, iblock, NULL);
                  if (IS_ERR(path)) {
                        err = PTR_ERR(path);
                        path = NULL;
                        goto out;
                  }
                  eh = path[depth].p_hdr;
                  ex = path[depth].p_ext;
                  if (ex2 != &newex)
                        ex2 = ex;
            }
            allocated = max_blocks;
      }
      /*
       * If there was a change of depth as part of the
       * insertion of ex3 above, we need to update the length
       * of the ex1 extent again here
       */
      if (ex1 && ex1 != ex) {
            ex1 = ex;
            ex1->ee_len = cpu_to_le16(iblock - ee_block);
            ext4_ext_mark_uninitialized(ex1);
            ex2 = &newex;
      }
      /* ex2: iblock to iblock + maxblocks-1 : initialised */
      ex2->ee_block = cpu_to_le32(iblock);
      ext4_ext_store_pblock(ex2, newblock);
      ex2->ee_len = cpu_to_le16(allocated);
      if (ex2 != ex)
            goto insert;
      err = ext4_ext_get_access(handle, inode, path + depth);
      if (err)
            goto out;
      /*
       * New (initialized) extent starts from the first block
       * in the current extent. i.e., ex2 == ex
       * We have to see if it can be merged with the extent
       * on the left.
       */
      if (ex2 > EXT_FIRST_EXTENT(eh)) {
            /*
             * To merge left, pass "ex2 - 1" to try_to_merge(),
             * since it merges towards right _only_.
             */
            ret = ext4_ext_try_to_merge(inode, path, ex2 - 1);
            if (ret) {
                  err = ext4_ext_correct_indexes(handle, inode, path);
                  if (err)
                        goto out;
                  depth = ext_depth(inode);
                  ex2--;
            }
      }
      /*
       * Try to Merge towards right. This might be required
       * only when the whole extent is being written to.
       * i.e. ex2 == ex and ex3 == NULL.
       */
      if (!ex3) {
            ret = ext4_ext_try_to_merge(inode, path, ex2);
            if (ret) {
                  err = ext4_ext_correct_indexes(handle, inode, path);
                  if (err)
                        goto out;
            }
      }
      /* Mark modified extent as dirty */
      err = ext4_ext_dirty(handle, inode, path + depth);
      goto out;
insert:
      err = ext4_ext_insert_extent(handle, inode, path, &newex);
out:
      return err ? err : allocated;
}

int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
                  ext4_fsblk_t iblock,
                  unsigned long max_blocks, struct buffer_head *bh_result,
                  int create, int extend_disksize)
{
      struct ext4_ext_path *path = NULL;
      struct ext4_extent_header *eh;
      struct ext4_extent newex, *ex;
      ext4_fsblk_t goal, newblock;
      int err = 0, depth, ret;
      unsigned long allocated = 0;

      __clear_bit(BH_New, &bh_result->b_state);
      ext_debug("blocks %d/%lu requested for inode %u\n", (int) iblock,
                  max_blocks, (unsigned) inode->i_ino);
      mutex_lock(&EXT4_I(inode)->truncate_mutex);

      /* check in cache */
      goal = ext4_ext_in_cache(inode, iblock, &newex);
      if (goal) {
            if (goal == EXT4_EXT_CACHE_GAP) {
                  if (!create) {
                        /*
                         * block isn't allocated yet and
                         * user doesn't want to allocate it
                         */
                        goto out2;
                  }
                  /* we should allocate requested block */
            } else if (goal == EXT4_EXT_CACHE_EXTENT) {
                  /* block is already allocated */
                  newblock = iblock
                           - le32_to_cpu(newex.ee_block)
                           + ext_pblock(&newex);
                  /* number of remaining blocks in the extent */
                  allocated = le16_to_cpu(newex.ee_len) -
                              (iblock - le32_to_cpu(newex.ee_block));
                  goto out;
            } else {
                  BUG();
            }
      }

      /* find extent for this block */
      path = ext4_ext_find_extent(inode, iblock, NULL);
      if (IS_ERR(path)) {
            err = PTR_ERR(path);
            path = NULL;
            goto out2;
      }

      depth = ext_depth(inode);

      /*
       * consistent leaf must not be empty;
       * this situation is possible, though, _during_ tree modification;
       * this is why assert can't be put in ext4_ext_find_extent()
       */
      BUG_ON(path[depth].p_ext == NULL && depth != 0);
      eh = path[depth].p_hdr;

      ex = path[depth].p_ext;
      if (ex) {
            unsigned long ee_block = le32_to_cpu(ex->ee_block);
            ext4_fsblk_t ee_start = ext_pblock(ex);
            unsigned short ee_len;

            /*
             * Uninitialized extents are treated as holes, except that
             * we split out initialized portions during a write.
             */
            ee_len = ext4_ext_get_actual_len(ex);
            /* if found extent covers block, simply return it */
            if (iblock >= ee_block && iblock < ee_block + ee_len) {
                  newblock = iblock - ee_block + ee_start;
                  /* number of remaining blocks in the extent */
                  allocated = ee_len - (iblock - ee_block);
                  ext_debug("%d fit into %lu:%d -> %llu\n", (int) iblock,
                              ee_block, ee_len, newblock);

                  /* Do not put uninitialized extent in the cache */
                  if (!ext4_ext_is_uninitialized(ex)) {
                        ext4_ext_put_in_cache(inode, ee_block,
                                          ee_len, ee_start,
                                          EXT4_EXT_CACHE_EXTENT);
                        goto out;
                  }
                  if (create == EXT4_CREATE_UNINITIALIZED_EXT)
                        goto out;
                  if (!create)
                        goto out2;

                  ret = ext4_ext_convert_to_initialized(handle, inode,
                                                path, iblock,
                                                max_blocks);
                  if (ret <= 0)
                        goto out2;
                  else
                        allocated = ret;
                  goto outnew;
            }
      }

      /*
       * requested block isn't allocated yet;
       * we couldn't try to create block if create flag is zero
       */
      if (!create) {
            /*
             * put just found gap into cache to speed up
             * subsequent requests
             */
            ext4_ext_put_gap_in_cache(inode, path, iblock);
            goto out2;
      }
      /*
       * Okay, we need to do block allocation.  Lazily initialize the block
       * allocation info here if necessary.
       */
      if (S_ISREG(inode->i_mode) && (!EXT4_I(inode)->i_block_alloc_info))
            ext4_init_block_alloc_info(inode);

      /* allocate new block */
      goal = ext4_ext_find_goal(inode, path, iblock);

      /*
       * See if request is beyond maximum number of blocks we can have in
       * a single extent. For an initialized extent this limit is
       * EXT_INIT_MAX_LEN and for an uninitialized extent this limit is
       * EXT_UNINIT_MAX_LEN.
       */
      if (max_blocks > EXT_INIT_MAX_LEN &&
          create != EXT4_CREATE_UNINITIALIZED_EXT)
            max_blocks = EXT_INIT_MAX_LEN;
      else if (max_blocks > EXT_UNINIT_MAX_LEN &&
             create == EXT4_CREATE_UNINITIALIZED_EXT)
            max_blocks = EXT_UNINIT_MAX_LEN;

      /* Check if we can really insert (iblock)::(iblock+max_blocks) extent */
      newex.ee_block = cpu_to_le32(iblock);
      newex.ee_len = cpu_to_le16(max_blocks);
      err = ext4_ext_check_overlap(inode, &newex, path);
      if (err)
            allocated = le16_to_cpu(newex.ee_len);
      else
            allocated = max_blocks;
      newblock = ext4_new_blocks(handle, inode, goal, &allocated, &err);
      if (!newblock)
            goto out2;
      ext_debug("allocate new block: goal %llu, found %llu/%lu\n",
                  goal, newblock, allocated);

      /* try to insert new extent into found leaf and return */
      ext4_ext_store_pblock(&newex, newblock);
      newex.ee_len = cpu_to_le16(allocated);
      if (create == EXT4_CREATE_UNINITIALIZED_EXT)  /* Mark uninitialized */
            ext4_ext_mark_uninitialized(&newex);
      err = ext4_ext_insert_extent(handle, inode, path, &newex);
      if (err) {
            /* free data blocks we just allocated */
            ext4_free_blocks(handle, inode, ext_pblock(&newex),
                              le16_to_cpu(newex.ee_len));
            goto out2;
      }

      if (extend_disksize && inode->i_size > EXT4_I(inode)->i_disksize)
            EXT4_I(inode)->i_disksize = inode->i_size;

      /* previous routine could use block we allocated */
      newblock = ext_pblock(&newex);
outnew:
      __set_bit(BH_New, &bh_result->b_state);

      /* Cache only when it is _not_ an uninitialized extent */
      if (create != EXT4_CREATE_UNINITIALIZED_EXT)
            ext4_ext_put_in_cache(inode, iblock, allocated, newblock,
                                    EXT4_EXT_CACHE_EXTENT);
out:
      if (allocated > max_blocks)
            allocated = max_blocks;
      ext4_ext_show_leaf(inode, path);
      __set_bit(BH_Mapped, &bh_result->b_state);
      bh_result->b_bdev = inode->i_sb->s_bdev;
      bh_result->b_blocknr = newblock;
out2:
      if (path) {
            ext4_ext_drop_refs(path);
            kfree(path);
      }
      mutex_unlock(&EXT4_I(inode)->truncate_mutex);

      return err ? err : allocated;
}

void ext4_ext_truncate(struct inode * inode, struct page *page)
{
      struct address_space *mapping = inode->i_mapping;
      struct super_block *sb = inode->i_sb;
      unsigned long last_block;
      handle_t *handle;
      int err = 0;

      /*
       * probably first extent we're gonna free will be last in block
       */
      err = ext4_writepage_trans_blocks(inode) + 3;
      handle = ext4_journal_start(inode, err);
      if (IS_ERR(handle)) {
            if (page) {
                  clear_highpage(page);
                  flush_dcache_page(page);
                  unlock_page(page);
                  page_cache_release(page);
            }
            return;
      }

      if (page)
            ext4_block_truncate_page(handle, page, mapping, inode->i_size);

      mutex_lock(&EXT4_I(inode)->truncate_mutex);
      ext4_ext_invalidate_cache(inode);

      /*
       * TODO: optimization is possible here.
       * Probably we need not scan at all,
       * because page truncation is enough.
       */
      if (ext4_orphan_add(handle, inode))
            goto out_stop;

      /* we have to know where to truncate from in crash case */
      EXT4_I(inode)->i_disksize = inode->i_size;
      ext4_mark_inode_dirty(handle, inode);

      last_block = (inode->i_size + sb->s_blocksize - 1)
                  >> EXT4_BLOCK_SIZE_BITS(sb);
      err = ext4_ext_remove_space(inode, last_block);

      /* In a multi-transaction truncate, we only make the final
       * transaction synchronous.
       */
      if (IS_SYNC(inode))
            handle->h_sync = 1;

out_stop:
      /*
       * If this was a simple ftruncate() and the file will remain alive,
       * then we need to clear up the orphan record which we created above.
       * However, if this was a real unlink then we were called by
       * ext4_delete_inode(), and we allow that function to clean up the
       * orphan info for us.
       */
      if (inode->i_nlink)
            ext4_orphan_del(handle, inode);

      mutex_unlock(&EXT4_I(inode)->truncate_mutex);
      ext4_journal_stop(handle);
}

/*
 * ext4_ext_writepage_trans_blocks:
 * calculate max number of blocks we could modify
 * in order to allocate new block for an inode
 */
int ext4_ext_writepage_trans_blocks(struct inode *inode, int num)
{
      int needed;

      needed = ext4_ext_calc_credits_for_insert(inode, NULL);

      /* caller wants to allocate num blocks, but note it includes sb */
      needed = needed * num - (num - 1);

#ifdef CONFIG_QUOTA
      needed += 2 * EXT4_QUOTA_TRANS_BLOCKS(inode->i_sb);
#endif

      return needed;
}

/*
 * preallocate space for a file. This implements ext4's fallocate inode
 * operation, which gets called from sys_fallocate system call.
 * For block-mapped files, posix_fallocate should fall back to the method
 * of writing zeroes to the required new blocks (the same behavior which is
 * expected for file systems which do not support fallocate() system call).
 */
long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
{
      handle_t *handle;
      ext4_fsblk_t block, max_blocks;
      ext4_fsblk_t nblocks = 0;
      int ret = 0;
      int ret2 = 0;
      int retries = 0;
      struct buffer_head map_bh;
      unsigned int credits, blkbits = inode->i_blkbits;

      /*
       * currently supporting (pre)allocate mode for extent-based
       * files _only_
       */
      if (!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL))
            return -EOPNOTSUPP;

      /* preallocation to directories is currently not supported */
      if (S_ISDIR(inode->i_mode))
            return -ENODEV;

      block = offset >> blkbits;
      max_blocks = (EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits)
                  - block;

      /*
       * credits to insert 1 extent into extent tree + buffers to be able to
       * modify 1 super block, 1 block bitmap and 1 group descriptor.
       */
      credits = EXT4_DATA_TRANS_BLOCKS(inode->i_sb) + 3;
retry:
      while (ret >= 0 && ret < max_blocks) {
            block = block + ret;
            max_blocks = max_blocks - ret;
            handle = ext4_journal_start(inode, credits);
            if (IS_ERR(handle)) {
                  ret = PTR_ERR(handle);
                  break;
            }

            ret = ext4_ext_get_blocks(handle, inode, block,
                                max_blocks, &map_bh,
                                EXT4_CREATE_UNINITIALIZED_EXT, 0);
            WARN_ON(!ret);
            if (!ret) {
                  ext4_error(inode->i_sb, "ext4_fallocate",
                           "ext4_ext_get_blocks returned 0! inode#%lu"
                           ", block=%llu, max_blocks=%llu",
                           inode->i_ino, block, max_blocks);
                  ret = -EIO;
                  ext4_mark_inode_dirty(handle, inode);
                  ret2 = ext4_journal_stop(handle);
                  break;
            }
            if (ret > 0) {
                  /* check wrap through sign-bit/zero here */
                  if ((block + ret) < 0 || (block + ret) < block) {
                        ret = -EIO;
                        ext4_mark_inode_dirty(handle, inode);
                        ret2 = ext4_journal_stop(handle);
                        break;
                  }
                  if (buffer_new(&map_bh) && ((block + ret) >
                      (EXT4_BLOCK_ALIGN(i_size_read(inode), blkbits)
                      >> blkbits)))
                              nblocks = nblocks + ret;
            }

            /* Update ctime if new blocks get allocated */
            if (nblocks) {
                  struct timespec now;

                  now = current_fs_time(inode->i_sb);
                  if (!timespec_equal(&inode->i_ctime, &now))
                        inode->i_ctime = now;
            }

            ext4_mark_inode_dirty(handle, inode);
            ret2 = ext4_journal_stop(handle);
            if (ret2)
                  break;
      }

      if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
            goto retry;

      /*
       * Time to update the file size.
       * Update only when preallocation was requested beyond the file size.
       */
      if (!(mode & FALLOC_FL_KEEP_SIZE) &&
          (offset + len) > i_size_read(inode)) {
            if (ret > 0) {
                  /*
                   * if no error, we assume preallocation succeeded
                   * completely
                   */
                  mutex_lock(&inode->i_mutex);
                  i_size_write(inode, offset + len);
                  EXT4_I(inode)->i_disksize = i_size_read(inode);
                  mutex_unlock(&inode->i_mutex);
            } else if (ret < 0 && nblocks) {
                  /* Handle partial allocation scenario */
                  loff_t newsize;

                  mutex_lock(&inode->i_mutex);
                  newsize  = (nblocks << blkbits) + i_size_read(inode);
                  i_size_write(inode, EXT4_BLOCK_ALIGN(newsize, blkbits));
                  EXT4_I(inode)->i_disksize = i_size_read(inode);
                  mutex_unlock(&inode->i_mutex);
            }
      }

      return ret > 0 ? ret2 : ret;
}

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