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inode.c

/*
 *  linux/fs/ext4/inode.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Goal-directed block allocation by Stephen Tweedie
 *    (sct@redhat.com), 1993, 1998
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 *  64-bit file support on 64-bit platforms by Jakub Jelinek
 *    (jj@sunsite.ms.mff.cuni.cz)
 *
 *  Assorted race fixes, rewrite of ext4_get_block() by Al Viro, 2000
 */

#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/buffer_head.h>
#include <linux/writeback.h>
#include <linux/mpage.h>
#include <linux/uio.h>
#include <linux/bio.h>
#include "xattr.h"
#include "acl.h"

/*
 * Test whether an inode is a fast symlink.
 */
static int ext4_inode_is_fast_symlink(struct inode *inode)
{
      int ea_blocks = EXT4_I(inode)->i_file_acl ?
            (inode->i_sb->s_blocksize >> 9) : 0;

      return (S_ISLNK(inode->i_mode) && inode->i_blocks - ea_blocks == 0);
}

/*
 * The ext4 forget function must perform a revoke if we are freeing data
 * which has been journaled.  Metadata (eg. indirect blocks) must be
 * revoked in all cases.
 *
 * "bh" may be NULL: a metadata block may have been freed from memory
 * but there may still be a record of it in the journal, and that record
 * still needs to be revoked.
 */
int ext4_forget(handle_t *handle, int is_metadata, struct inode *inode,
                  struct buffer_head *bh, ext4_fsblk_t blocknr)
{
      int err;

      might_sleep();

      BUFFER_TRACE(bh, "enter");

      jbd_debug(4, "forgetting bh %p: is_metadata = %d, mode %o, "
              "data mode %lx\n",
              bh, is_metadata, inode->i_mode,
              test_opt(inode->i_sb, DATA_FLAGS));

      /* Never use the revoke function if we are doing full data
       * journaling: there is no need to, and a V1 superblock won't
       * support it.  Otherwise, only skip the revoke on un-journaled
       * data blocks. */

      if (test_opt(inode->i_sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA ||
          (!is_metadata && !ext4_should_journal_data(inode))) {
            if (bh) {
                  BUFFER_TRACE(bh, "call jbd2_journal_forget");
                  return ext4_journal_forget(handle, bh);
            }
            return 0;
      }

      /*
       * data!=journal && (is_metadata || should_journal_data(inode))
       */
      BUFFER_TRACE(bh, "call ext4_journal_revoke");
      err = ext4_journal_revoke(handle, blocknr, bh);
      if (err)
            ext4_abort(inode->i_sb, __FUNCTION__,
                     "error %d when attempting revoke", err);
      BUFFER_TRACE(bh, "exit");
      return err;
}

/*
 * Work out how many blocks we need to proceed with the next chunk of a
 * truncate transaction.
 */
static unsigned long blocks_for_truncate(struct inode *inode)
{
      unsigned long needed;

      needed = inode->i_blocks >> (inode->i_sb->s_blocksize_bits - 9);

      /* Give ourselves just enough room to cope with inodes in which
       * i_blocks is corrupt: we've seen disk corruptions in the past
       * which resulted in random data in an inode which looked enough
       * like a regular file for ext4 to try to delete it.  Things
       * will go a bit crazy if that happens, but at least we should
       * try not to panic the whole kernel. */
      if (needed < 2)
            needed = 2;

      /* But we need to bound the transaction so we don't overflow the
       * journal. */
      if (needed > EXT4_MAX_TRANS_DATA)
            needed = EXT4_MAX_TRANS_DATA;

      return EXT4_DATA_TRANS_BLOCKS(inode->i_sb) + needed;
}

/*
 * Truncate transactions can be complex and absolutely huge.  So we need to
 * be able to restart the transaction at a conventient checkpoint to make
 * sure we don't overflow the journal.
 *
 * start_transaction gets us a new handle for a truncate transaction,
 * and extend_transaction tries to extend the existing one a bit.  If
 * extend fails, we need to propagate the failure up and restart the
 * transaction in the top-level truncate loop. --sct
 */
static handle_t *start_transaction(struct inode *inode)
{
      handle_t *result;

      result = ext4_journal_start(inode, blocks_for_truncate(inode));
      if (!IS_ERR(result))
            return result;

      ext4_std_error(inode->i_sb, PTR_ERR(result));
      return result;
}

/*
 * Try to extend this transaction for the purposes of truncation.
 *
 * Returns 0 if we managed to create more room.  If we can't create more
 * room, and the transaction must be restarted we return 1.
 */
static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
{
      if (handle->h_buffer_credits > EXT4_RESERVE_TRANS_BLOCKS)
            return 0;
      if (!ext4_journal_extend(handle, blocks_for_truncate(inode)))
            return 0;
      return 1;
}

/*
 * Restart the transaction associated with *handle.  This does a commit,
 * so before we call here everything must be consistently dirtied against
 * this transaction.
 */
static int ext4_journal_test_restart(handle_t *handle, struct inode *inode)
{
      jbd_debug(2, "restarting handle %p\n", handle);
      return ext4_journal_restart(handle, blocks_for_truncate(inode));
}

/*
 * Called at the last iput() if i_nlink is zero.
 */
void ext4_delete_inode (struct inode * inode)
{
      handle_t *handle;

      truncate_inode_pages(&inode->i_data, 0);

      if (is_bad_inode(inode))
            goto no_delete;

      handle = start_transaction(inode);
      if (IS_ERR(handle)) {
            /*
             * If we're going to skip the normal cleanup, we still need to
             * make sure that the in-core orphan linked list is properly
             * cleaned up.
             */
            ext4_orphan_del(NULL, inode);
            goto no_delete;
      }

      if (IS_SYNC(inode))
            handle->h_sync = 1;
      inode->i_size = 0;
      if (inode->i_blocks)
            ext4_truncate(inode);
      /*
       * Kill off the orphan record which ext4_truncate created.
       * AKPM: I think this can be inside the above `if'.
       * Note that ext4_orphan_del() has to be able to cope with the
       * deletion of a non-existent orphan - this is because we don't
       * know if ext4_truncate() actually created an orphan record.
       * (Well, we could do this if we need to, but heck - it works)
       */
      ext4_orphan_del(handle, inode);
      EXT4_I(inode)->i_dtime  = get_seconds();

      /*
       * One subtle ordering requirement: if anything has gone wrong
       * (transaction abort, IO errors, whatever), then we can still
       * do these next steps (the fs will already have been marked as
       * having errors), but we can't free the inode if the mark_dirty
       * fails.
       */
      if (ext4_mark_inode_dirty(handle, inode))
            /* If that failed, just do the required in-core inode clear. */
            clear_inode(inode);
      else
            ext4_free_inode(handle, inode);
      ext4_journal_stop(handle);
      return;
no_delete:
      clear_inode(inode);     /* We must guarantee clearing of inode... */
}

typedef struct {
      __le32      *p;
      __le32      key;
      struct buffer_head *bh;
} Indirect;

static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
{
      p->key = *(p->p = v);
      p->bh = bh;
}

static int verify_chain(Indirect *from, Indirect *to)
{
      while (from <= to && from->key == *from->p)
            from++;
      return (from > to);
}

/**
 *    ext4_block_to_path - parse the block number into array of offsets
 *    @inode: inode in question (we are only interested in its superblock)
 *    @i_block: block number to be parsed
 *    @offsets: array to store the offsets in
 *    @boundary: set this non-zero if the referred-to block is likely to be
 *           followed (on disk) by an indirect block.
 *
 *    To store the locations of file's data ext4 uses a data structure common
 *    for UNIX filesystems - tree of pointers anchored in the inode, with
 *    data blocks at leaves and indirect blocks in intermediate nodes.
 *    This function translates the block number into path in that tree -
 *    return value is the path length and @offsets[n] is the offset of
 *    pointer to (n+1)th node in the nth one. If @block is out of range
 *    (negative or too large) warning is printed and zero returned.
 *
 *    Note: function doesn't find node addresses, so no IO is needed. All
 *    we need to know is the capacity of indirect blocks (taken from the
 *    inode->i_sb).
 */

/*
 * Portability note: the last comparison (check that we fit into triple
 * indirect block) is spelled differently, because otherwise on an
 * architecture with 32-bit longs and 8Kb pages we might get into trouble
 * if our filesystem had 8Kb blocks. We might use long long, but that would
 * kill us on x86. Oh, well, at least the sign propagation does not matter -
 * i_block would have to be negative in the very beginning, so we would not
 * get there at all.
 */

static int ext4_block_to_path(struct inode *inode,
                  long i_block, int offsets[4], int *boundary)
{
      int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
      int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
      const long direct_blocks = EXT4_NDIR_BLOCKS,
            indirect_blocks = ptrs,
            double_blocks = (1 << (ptrs_bits * 2));
      int n = 0;
      int final = 0;

      if (i_block < 0) {
            ext4_warning (inode->i_sb, "ext4_block_to_path", "block < 0");
      } else if (i_block < direct_blocks) {
            offsets[n++] = i_block;
            final = direct_blocks;
      } else if ( (i_block -= direct_blocks) < indirect_blocks) {
            offsets[n++] = EXT4_IND_BLOCK;
            offsets[n++] = i_block;
            final = ptrs;
      } else if ((i_block -= indirect_blocks) < double_blocks) {
            offsets[n++] = EXT4_DIND_BLOCK;
            offsets[n++] = i_block >> ptrs_bits;
            offsets[n++] = i_block & (ptrs - 1);
            final = ptrs;
      } else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
            offsets[n++] = EXT4_TIND_BLOCK;
            offsets[n++] = i_block >> (ptrs_bits * 2);
            offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
            offsets[n++] = i_block & (ptrs - 1);
            final = ptrs;
      } else {
            ext4_warning(inode->i_sb, "ext4_block_to_path", "block > big");
      }
      if (boundary)
            *boundary = final - 1 - (i_block & (ptrs - 1));
      return n;
}

/**
 *    ext4_get_branch - read the chain of indirect blocks leading to data
 *    @inode: inode in question
 *    @depth: depth of the chain (1 - direct pointer, etc.)
 *    @offsets: offsets of pointers in inode/indirect blocks
 *    @chain: place to store the result
 *    @err: here we store the error value
 *
 *    Function fills the array of triples <key, p, bh> and returns %NULL
 *    if everything went OK or the pointer to the last filled triple
 *    (incomplete one) otherwise. Upon the return chain[i].key contains
 *    the number of (i+1)-th block in the chain (as it is stored in memory,
 *    i.e. little-endian 32-bit), chain[i].p contains the address of that
 *    number (it points into struct inode for i==0 and into the bh->b_data
 *    for i>0) and chain[i].bh points to the buffer_head of i-th indirect
 *    block for i>0 and NULL for i==0. In other words, it holds the block
 *    numbers of the chain, addresses they were taken from (and where we can
 *    verify that chain did not change) and buffer_heads hosting these
 *    numbers.
 *
 *    Function stops when it stumbles upon zero pointer (absent block)
 *          (pointer to last triple returned, *@err == 0)
 *    or when it gets an IO error reading an indirect block
 *          (ditto, *@err == -EIO)
 *    or when it notices that chain had been changed while it was reading
 *          (ditto, *@err == -EAGAIN)
 *    or when it reads all @depth-1 indirect blocks successfully and finds
 *    the whole chain, all way to the data (returns %NULL, *err == 0).
 */
static Indirect *ext4_get_branch(struct inode *inode, int depth, int *offsets,
                         Indirect chain[4], int *err)
{
      struct super_block *sb = inode->i_sb;
      Indirect *p = chain;
      struct buffer_head *bh;

      *err = 0;
      /* i_data is not going away, no lock needed */
      add_chain (chain, NULL, EXT4_I(inode)->i_data + *offsets);
      if (!p->key)
            goto no_block;
      while (--depth) {
            bh = sb_bread(sb, le32_to_cpu(p->key));
            if (!bh)
                  goto failure;
            /* Reader: pointers */
            if (!verify_chain(chain, p))
                  goto changed;
            add_chain(++p, bh, (__le32*)bh->b_data + *++offsets);
            /* Reader: end */
            if (!p->key)
                  goto no_block;
      }
      return NULL;

changed:
      brelse(bh);
      *err = -EAGAIN;
      goto no_block;
failure:
      *err = -EIO;
no_block:
      return p;
}

/**
 *    ext4_find_near - find a place for allocation with sufficient locality
 *    @inode: owner
 *    @ind: descriptor of indirect block.
 *
 *    This function returns the prefered place for block allocation.
 *    It is used when heuristic for sequential allocation fails.
 *    Rules are:
 *      + if there is a block to the left of our position - allocate near it.
 *      + if pointer will live in indirect block - allocate near that block.
 *      + if pointer will live in inode - allocate in the same
 *        cylinder group.
 *
 * In the latter case we colour the starting block by the callers PID to
 * prevent it from clashing with concurrent allocations for a different inode
 * in the same block group.   The PID is used here so that functionally related
 * files will be close-by on-disk.
 *
 *    Caller must make sure that @ind is valid and will stay that way.
 */
static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
{
      struct ext4_inode_info *ei = EXT4_I(inode);
      __le32 *start = ind->bh ? (__le32*) ind->bh->b_data : ei->i_data;
      __le32 *p;
      ext4_fsblk_t bg_start;
      ext4_grpblk_t colour;

      /* Try to find previous block */
      for (p = ind->p - 1; p >= start; p--) {
            if (*p)
                  return le32_to_cpu(*p);
      }

      /* No such thing, so let's try location of indirect block */
      if (ind->bh)
            return ind->bh->b_blocknr;

      /*
       * It is going to be referred to from the inode itself? OK, just put it
       * into the same cylinder group then.
       */
      bg_start = ext4_group_first_block_no(inode->i_sb, ei->i_block_group);
      colour = (current->pid % 16) *
                  (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
      return bg_start + colour;
}

/**
 *    ext4_find_goal - find a prefered place for allocation.
 *    @inode: owner
 *    @block:  block we want
 *    @chain:  chain of indirect blocks
 *    @partial: pointer to the last triple within a chain
 *    @goal:      place to store the result.
 *
 *    Normally this function find the prefered place for block allocation,
 *    stores it in *@goal and returns zero.
 */

static ext4_fsblk_t ext4_find_goal(struct inode *inode, long block,
            Indirect chain[4], Indirect *partial)
{
      struct ext4_block_alloc_info *block_i;

      block_i =  EXT4_I(inode)->i_block_alloc_info;

      /*
       * try the heuristic for sequential allocation,
       * failing that at least try to get decent locality.
       */
      if (block_i && (block == block_i->last_alloc_logical_block + 1)
            && (block_i->last_alloc_physical_block != 0)) {
            return block_i->last_alloc_physical_block + 1;
      }

      return ext4_find_near(inode, partial);
}

/**
 *    ext4_blks_to_allocate: Look up the block map and count the number
 *    of direct blocks need to be allocated for the given branch.
 *
 *    @branch: chain of indirect blocks
 *    @k: number of blocks need for indirect blocks
 *    @blks: number of data blocks to be mapped.
 *    @blocks_to_boundary:  the offset in the indirect block
 *
 *    return the total number of blocks to be allocate, including the
 *    direct and indirect blocks.
 */
static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned long blks,
            int blocks_to_boundary)
{
      unsigned long count = 0;

      /*
       * Simple case, [t,d]Indirect block(s) has not allocated yet
       * then it's clear blocks on that path have not allocated
       */
      if (k > 0) {
            /* right now we don't handle cross boundary allocation */
            if (blks < blocks_to_boundary + 1)
                  count += blks;
            else
                  count += blocks_to_boundary + 1;
            return count;
      }

      count++;
      while (count < blks && count <= blocks_to_boundary &&
            le32_to_cpu(*(branch[0].p + count)) == 0) {
            count++;
      }
      return count;
}

/**
 *    ext4_alloc_blocks: multiple allocate blocks needed for a branch
 *    @indirect_blks: the number of blocks need to allocate for indirect
 *                blocks
 *
 *    @new_blocks: on return it will store the new block numbers for
 *    the indirect blocks(if needed) and the first direct block,
 *    @blks:      on return it will store the total number of allocated
 *          direct blocks
 */
static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
                  ext4_fsblk_t goal, int indirect_blks, int blks,
                  ext4_fsblk_t new_blocks[4], int *err)
{
      int target, i;
      unsigned long count = 0;
      int index = 0;
      ext4_fsblk_t current_block = 0;
      int ret = 0;

      /*
       * Here we try to allocate the requested multiple blocks at once,
       * on a best-effort basis.
       * To build a branch, we should allocate blocks for
       * the indirect blocks(if not allocated yet), and at least
       * the first direct block of this branch.  That's the
       * minimum number of blocks need to allocate(required)
       */
      target = blks + indirect_blks;

      while (1) {
            count = target;
            /* allocating blocks for indirect blocks and direct blocks */
            current_block = ext4_new_blocks(handle,inode,goal,&count,err);
            if (*err)
                  goto failed_out;

            target -= count;
            /* allocate blocks for indirect blocks */
            while (index < indirect_blks && count) {
                  new_blocks[index++] = current_block++;
                  count--;
            }

            if (count > 0)
                  break;
      }

      /* save the new block number for the first direct block */
      new_blocks[index] = current_block;

      /* total number of blocks allocated for direct blocks */
      ret = count;
      *err = 0;
      return ret;
failed_out:
      for (i = 0; i <index; i++)
            ext4_free_blocks(handle, inode, new_blocks[i], 1);
      return ret;
}

/**
 *    ext4_alloc_branch - allocate and set up a chain of blocks.
 *    @inode: owner
 *    @indirect_blks: number of allocated indirect blocks
 *    @blks: number of allocated direct blocks
 *    @offsets: offsets (in the blocks) to store the pointers to next.
 *    @branch: place to store the chain in.
 *
 *    This function allocates blocks, zeroes out all but the last one,
 *    links them into chain and (if we are synchronous) writes them to disk.
 *    In other words, it prepares a branch that can be spliced onto the
 *    inode. It stores the information about that chain in the branch[], in
 *    the same format as ext4_get_branch() would do. We are calling it after
 *    we had read the existing part of chain and partial points to the last
 *    triple of that (one with zero ->key). Upon the exit we have the same
 *    picture as after the successful ext4_get_block(), except that in one
 *    place chain is disconnected - *branch->p is still zero (we did not
 *    set the last link), but branch->key contains the number that should
 *    be placed into *branch->p to fill that gap.
 *
 *    If allocation fails we free all blocks we've allocated (and forget
 *    their buffer_heads) and return the error value the from failed
 *    ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
 *    as described above and return 0.
 */
static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
                  int indirect_blks, int *blks, ext4_fsblk_t goal,
                  int *offsets, Indirect *branch)
{
      int blocksize = inode->i_sb->s_blocksize;
      int i, n = 0;
      int err = 0;
      struct buffer_head *bh;
      int num;
      ext4_fsblk_t new_blocks[4];
      ext4_fsblk_t current_block;

      num = ext4_alloc_blocks(handle, inode, goal, indirect_blks,
                        *blks, new_blocks, &err);
      if (err)
            return err;

      branch[0].key = cpu_to_le32(new_blocks[0]);
      /*
       * metadata blocks and data blocks are allocated.
       */
      for (n = 1; n <= indirect_blks;  n++) {
            /*
             * Get buffer_head for parent block, zero it out
             * and set the pointer to new one, then send
             * parent to disk.
             */
            bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
            branch[n].bh = bh;
            lock_buffer(bh);
            BUFFER_TRACE(bh, "call get_create_access");
            err = ext4_journal_get_create_access(handle, bh);
            if (err) {
                  unlock_buffer(bh);
                  brelse(bh);
                  goto failed;
            }

            memset(bh->b_data, 0, blocksize);
            branch[n].p = (__le32 *) bh->b_data + offsets[n];
            branch[n].key = cpu_to_le32(new_blocks[n]);
            *branch[n].p = branch[n].key;
            if ( n == indirect_blks) {
                  current_block = new_blocks[n];
                  /*
                   * End of chain, update the last new metablock of
                   * the chain to point to the new allocated
                   * data blocks numbers
                   */
                  for (i=1; i < num; i++)
                        *(branch[n].p + i) = cpu_to_le32(++current_block);
            }
            BUFFER_TRACE(bh, "marking uptodate");
            set_buffer_uptodate(bh);
            unlock_buffer(bh);

            BUFFER_TRACE(bh, "call ext4_journal_dirty_metadata");
            err = ext4_journal_dirty_metadata(handle, bh);
            if (err)
                  goto failed;
      }
      *blks = num;
      return err;
failed:
      /* Allocation failed, free what we already allocated */
      for (i = 1; i <= n ; i++) {
            BUFFER_TRACE(branch[i].bh, "call jbd2_journal_forget");
            ext4_journal_forget(handle, branch[i].bh);
      }
      for (i = 0; i <indirect_blks; i++)
            ext4_free_blocks(handle, inode, new_blocks[i], 1);

      ext4_free_blocks(handle, inode, new_blocks[i], num);

      return err;
}

/**
 * ext4_splice_branch - splice the allocated branch onto inode.
 * @inode: owner
 * @block: (logical) number of block we are adding
 * @chain: chain of indirect blocks (with a missing link - see
 *    ext4_alloc_branch)
 * @where: location of missing link
 * @num:   number of indirect blocks we are adding
 * @blks:  number of direct blocks we are adding
 *
 * This function fills the missing link and does all housekeeping needed in
 * inode (->i_blocks, etc.). In case of success we end up with the full
 * chain to new block and return 0.
 */
static int ext4_splice_branch(handle_t *handle, struct inode *inode,
                  long block, Indirect *where, int num, int blks)
{
      int i;
      int err = 0;
      struct ext4_block_alloc_info *block_i;
      ext4_fsblk_t current_block;

      block_i = EXT4_I(inode)->i_block_alloc_info;
      /*
       * If we're splicing into a [td]indirect block (as opposed to the
       * inode) then we need to get write access to the [td]indirect block
       * before the splice.
       */
      if (where->bh) {
            BUFFER_TRACE(where->bh, "get_write_access");
            err = ext4_journal_get_write_access(handle, where->bh);
            if (err)
                  goto err_out;
      }
      /* That's it */

      *where->p = where->key;

      /*
       * Update the host buffer_head or inode to point to more just allocated
       * direct blocks blocks
       */
      if (num == 0 && blks > 1) {
            current_block = le32_to_cpu(where->key) + 1;
            for (i = 1; i < blks; i++)
                  *(where->p + i ) = cpu_to_le32(current_block++);
      }

      /*
       * update the most recently allocated logical & physical block
       * in i_block_alloc_info, to assist find the proper goal block for next
       * allocation
       */
      if (block_i) {
            block_i->last_alloc_logical_block = block + blks - 1;
            block_i->last_alloc_physical_block =
                        le32_to_cpu(where[num].key) + blks - 1;
      }

      /* We are done with atomic stuff, now do the rest of housekeeping */

      inode->i_ctime = ext4_current_time(inode);
      ext4_mark_inode_dirty(handle, inode);

      /* had we spliced it onto indirect block? */
      if (where->bh) {
            /*
             * If we spliced it onto an indirect block, we haven't
             * altered the inode.  Note however that if it is being spliced
             * onto an indirect block at the very end of the file (the
             * file is growing) then we *will* alter the inode to reflect
             * the new i_size.  But that is not done here - it is done in
             * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
             */
            jbd_debug(5, "splicing indirect only\n");
            BUFFER_TRACE(where->bh, "call ext4_journal_dirty_metadata");
            err = ext4_journal_dirty_metadata(handle, where->bh);
            if (err)
                  goto err_out;
      } else {
            /*
             * OK, we spliced it into the inode itself on a direct block.
             * Inode was dirtied above.
             */
            jbd_debug(5, "splicing direct\n");
      }
      return err;

err_out:
      for (i = 1; i <= num; i++) {
            BUFFER_TRACE(where[i].bh, "call jbd2_journal_forget");
            ext4_journal_forget(handle, where[i].bh);
            ext4_free_blocks(handle,inode,le32_to_cpu(where[i-1].key),1);
      }
      ext4_free_blocks(handle, inode, le32_to_cpu(where[num].key), blks);

      return err;
}

/*
 * Allocation strategy is simple: if we have to allocate something, we will
 * have to go the whole way to leaf. So let's do it before attaching anything
 * to tree, set linkage between the newborn blocks, write them if sync is
 * required, recheck the path, free and repeat if check fails, otherwise
 * set the last missing link (that will protect us from any truncate-generated
 * removals - all blocks on the path are immune now) and possibly force the
 * write on the parent block.
 * That has a nice additional property: no special recovery from the failed
 * allocations is needed - we simply release blocks and do not touch anything
 * reachable from inode.
 *
 * `handle' can be NULL if create == 0.
 *
 * The BKL may not be held on entry here.  Be sure to take it early.
 * return > 0, # of blocks mapped or allocated.
 * return = 0, if plain lookup failed.
 * return < 0, error case.
 */
int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
            sector_t iblock, unsigned long maxblocks,
            struct buffer_head *bh_result,
            int create, int extend_disksize)
{
      int err = -EIO;
      int offsets[4];
      Indirect chain[4];
      Indirect *partial;
      ext4_fsblk_t goal;
      int indirect_blks;
      int blocks_to_boundary = 0;
      int depth;
      struct ext4_inode_info *ei = EXT4_I(inode);
      int count = 0;
      ext4_fsblk_t first_block = 0;


      J_ASSERT(!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL));
      J_ASSERT(handle != NULL || create == 0);
      depth = ext4_block_to_path(inode,iblock,offsets,&blocks_to_boundary);

      if (depth == 0)
            goto out;

      partial = ext4_get_branch(inode, depth, offsets, chain, &err);

      /* Simplest case - block found, no allocation needed */
      if (!partial) {
            first_block = le32_to_cpu(chain[depth - 1].key);
            clear_buffer_new(bh_result);
            count++;
            /*map more blocks*/
            while (count < maxblocks && count <= blocks_to_boundary) {
                  ext4_fsblk_t blk;

                  if (!verify_chain(chain, partial)) {
                        /*
                         * Indirect block might be removed by
                         * truncate while we were reading it.
                         * Handling of that case: forget what we've
                         * got now. Flag the err as EAGAIN, so it
                         * will reread.
                         */
                        err = -EAGAIN;
                        count = 0;
                        break;
                  }
                  blk = le32_to_cpu(*(chain[depth-1].p + count));

                  if (blk == first_block + count)
                        count++;
                  else
                        break;
            }
            if (err != -EAGAIN)
                  goto got_it;
      }

      /* Next simple case - plain lookup or failed read of indirect block */
      if (!create || err == -EIO)
            goto cleanup;

      mutex_lock(&ei->truncate_mutex);

      /*
       * If the indirect block is missing while we are reading
       * the chain(ext4_get_branch() returns -EAGAIN err), or
       * if the chain has been changed after we grab the semaphore,
       * (either because another process truncated this branch, or
       * another get_block allocated this branch) re-grab the chain to see if
       * the request block has been allocated or not.
       *
       * Since we already block the truncate/other get_block
       * at this point, we will have the current copy of the chain when we
       * splice the branch into the tree.
       */
      if (err == -EAGAIN || !verify_chain(chain, partial)) {
            while (partial > chain) {
                  brelse(partial->bh);
                  partial--;
            }
            partial = ext4_get_branch(inode, depth, offsets, chain, &err);
            if (!partial) {
                  count++;
                  mutex_unlock(&ei->truncate_mutex);
                  if (err)
                        goto cleanup;
                  clear_buffer_new(bh_result);
                  goto got_it;
            }
      }

      /*
       * Okay, we need to do block allocation.  Lazily initialize the block
       * allocation info here if necessary
      */
      if (S_ISREG(inode->i_mode) && (!ei->i_block_alloc_info))
            ext4_init_block_alloc_info(inode);

      goal = ext4_find_goal(inode, iblock, chain, partial);

      /* the number of blocks need to allocate for [d,t]indirect blocks */
      indirect_blks = (chain + depth) - partial - 1;

      /*
       * Next look up the indirect map to count the totoal number of
       * direct blocks to allocate for this branch.
       */
      count = ext4_blks_to_allocate(partial, indirect_blks,
                              maxblocks, blocks_to_boundary);
      /*
       * Block out ext4_truncate while we alter the tree
       */
      err = ext4_alloc_branch(handle, inode, indirect_blks, &count, goal,
                        offsets + (partial - chain), partial);

      /*
       * The ext4_splice_branch call will free and forget any buffers
       * on the new chain if there is a failure, but that risks using
       * up transaction credits, especially for bitmaps where the
       * credits cannot be returned.  Can we handle this somehow?  We
       * may need to return -EAGAIN upwards in the worst case.  --sct
       */
      if (!err)
            err = ext4_splice_branch(handle, inode, iblock,
                              partial, indirect_blks, count);
      /*
       * i_disksize growing is protected by truncate_mutex.  Don't forget to
       * protect it if you're about to implement concurrent
       * ext4_get_block() -bzzz
      */
      if (!err && extend_disksize && inode->i_size > ei->i_disksize)
            ei->i_disksize = inode->i_size;
      mutex_unlock(&ei->truncate_mutex);
      if (err)
            goto cleanup;

      set_buffer_new(bh_result);
got_it:
      map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
      if (count > blocks_to_boundary)
            set_buffer_boundary(bh_result);
      err = count;
      /* Clean up and exit */
      partial = chain + depth - 1;  /* the whole chain */
cleanup:
      while (partial > chain) {
            BUFFER_TRACE(partial->bh, "call brelse");
            brelse(partial->bh);
            partial--;
      }
      BUFFER_TRACE(bh_result, "returned");
out:
      return err;
}

#define DIO_CREDITS (EXT4_RESERVE_TRANS_BLOCKS + 32)

static int ext4_get_block(struct inode *inode, sector_t iblock,
                  struct buffer_head *bh_result, int create)
{
      handle_t *handle = ext4_journal_current_handle();
      int ret = 0;
      unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;

      if (!create)
            goto get_block;         /* A read */

      if (max_blocks == 1)
            goto get_block;         /* A single block get */

      if (handle->h_transaction->t_state == T_LOCKED) {
            /*
             * Huge direct-io writes can hold off commits for long
             * periods of time.  Let this commit run.
             */
            ext4_journal_stop(handle);
            handle = ext4_journal_start(inode, DIO_CREDITS);
            if (IS_ERR(handle))
                  ret = PTR_ERR(handle);
            goto get_block;
      }

      if (handle->h_buffer_credits <= EXT4_RESERVE_TRANS_BLOCKS) {
            /*
             * Getting low on buffer credits...
             */
            ret = ext4_journal_extend(handle, DIO_CREDITS);
            if (ret > 0) {
                  /*
                   * Couldn't extend the transaction.  Start a new one.
                   */
                  ret = ext4_journal_restart(handle, DIO_CREDITS);
            }
      }

get_block:
      if (ret == 0) {
            ret = ext4_get_blocks_wrap(handle, inode, iblock,
                              max_blocks, bh_result, create, 0);
            if (ret > 0) {
                  bh_result->b_size = (ret << inode->i_blkbits);
                  ret = 0;
            }
      }
      return ret;
}

/*
 * `handle' can be NULL if create is zero
 */
struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
                        long block, int create, int *errp)
{
      struct buffer_head dummy;
      int fatal = 0, err;

      J_ASSERT(handle != NULL || create == 0);

      dummy.b_state = 0;
      dummy.b_blocknr = -1000;
      buffer_trace_init(&dummy.b_history);
      err = ext4_get_blocks_wrap(handle, inode, block, 1,
                              &dummy, create, 1);
      /*
       * ext4_get_blocks_handle() returns number of blocks
       * mapped. 0 in case of a HOLE.
       */
      if (err > 0) {
            if (err > 1)
                  WARN_ON(1);
            err = 0;
      }
      *errp = err;
      if (!err && buffer_mapped(&dummy)) {
            struct buffer_head *bh;
            bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
            if (!bh) {
                  *errp = -EIO;
                  goto err;
            }
            if (buffer_new(&dummy)) {
                  J_ASSERT(create != 0);
                  J_ASSERT(handle != NULL);

                  /*
                   * Now that we do not always journal data, we should
                   * keep in mind whether this should always journal the
                   * new buffer as metadata.  For now, regular file
                   * writes use ext4_get_block instead, so it's not a
                   * problem.
                   */
                  lock_buffer(bh);
                  BUFFER_TRACE(bh, "call get_create_access");
                  fatal = ext4_journal_get_create_access(handle, bh);
                  if (!fatal && !buffer_uptodate(bh)) {
                        memset(bh->b_data,0,inode->i_sb->s_blocksize);
                        set_buffer_uptodate(bh);
                  }
                  unlock_buffer(bh);
                  BUFFER_TRACE(bh, "call ext4_journal_dirty_metadata");
                  err = ext4_journal_dirty_metadata(handle, bh);
                  if (!fatal)
                        fatal = err;
            } else {
                  BUFFER_TRACE(bh, "not a new buffer");
            }
            if (fatal) {
                  *errp = fatal;
                  brelse(bh);
                  bh = NULL;
            }
            return bh;
      }
err:
      return NULL;
}

struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
                         int block, int create, int *err)
{
      struct buffer_head * bh;

      bh = ext4_getblk(handle, inode, block, create, err);
      if (!bh)
            return bh;
      if (buffer_uptodate(bh))
            return bh;
      ll_rw_block(READ_META, 1, &bh);
      wait_on_buffer(bh);
      if (buffer_uptodate(bh))
            return bh;
      put_bh(bh);
      *err = -EIO;
      return NULL;
}

static int walk_page_buffers( handle_t *handle,
                        struct buffer_head *head,
                        unsigned from,
                        unsigned to,
                        int *partial,
                        int (*fn)(  handle_t *handle,
                                    struct buffer_head *bh))
{
      struct buffer_head *bh;
      unsigned block_start, block_end;
      unsigned blocksize = head->b_size;
      int err, ret = 0;
      struct buffer_head *next;

      for ( bh = head, block_start = 0;
            ret == 0 && (bh != head || !block_start);
            block_start = block_end, bh = next)
      {
            next = bh->b_this_page;
            block_end = block_start + blocksize;
            if (block_end <= from || block_start >= to) {
                  if (partial && !buffer_uptodate(bh))
                        *partial = 1;
                  continue;
            }
            err = (*fn)(handle, bh);
            if (!ret)
                  ret = err;
      }
      return ret;
}

/*
 * To preserve ordering, it is essential that the hole instantiation and
 * the data write be encapsulated in a single transaction.  We cannot
 * close off a transaction and start a new one between the ext4_get_block()
 * and the commit_write().  So doing the jbd2_journal_start at the start of
 * prepare_write() is the right place.
 *
 * Also, this function can nest inside ext4_writepage() ->
 * block_write_full_page(). In that case, we *know* that ext4_writepage()
 * has generated enough buffer credits to do the whole page.  So we won't
 * block on the journal in that case, which is good, because the caller may
 * be PF_MEMALLOC.
 *
 * By accident, ext4 can be reentered when a transaction is open via
 * quota file writes.  If we were to commit the transaction while thus
 * reentered, there can be a deadlock - we would be holding a quota
 * lock, and the commit would never complete if another thread had a
 * transaction open and was blocking on the quota lock - a ranking
 * violation.
 *
 * So what we do is to rely on the fact that jbd2_journal_stop/journal_start
 * will _not_ run commit under these circumstances because handle->h_ref
 * is elevated.  We'll still have enough credits for the tiny quotafile
 * write.
 */
static int do_journal_get_write_access(handle_t *handle,
                              struct buffer_head *bh)
{
      if (!buffer_mapped(bh) || buffer_freed(bh))
            return 0;
      return ext4_journal_get_write_access(handle, bh);
}

static int ext4_write_begin(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned flags,
                        struct page **pagep, void **fsdata)
{
      struct inode *inode = mapping->host;
      int ret, needed_blocks = ext4_writepage_trans_blocks(inode);
      handle_t *handle;
      int retries = 0;
      struct page *page;
      pgoff_t index;
      unsigned from, to;

      index = pos >> PAGE_CACHE_SHIFT;
      from = pos & (PAGE_CACHE_SIZE - 1);
      to = from + len;

retry:
      page = __grab_cache_page(mapping, index);
      if (!page)
            return -ENOMEM;
      *pagep = page;

      handle = ext4_journal_start(inode, needed_blocks);
      if (IS_ERR(handle)) {
            unlock_page(page);
            page_cache_release(page);
            ret = PTR_ERR(handle);
            goto out;
      }

      ret = block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
                                          ext4_get_block);

      if (!ret && ext4_should_journal_data(inode)) {
            ret = walk_page_buffers(handle, page_buffers(page),
                        from, to, NULL, do_journal_get_write_access);
      }

      if (ret) {
            ext4_journal_stop(handle);
            unlock_page(page);
            page_cache_release(page);
      }

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

int ext4_journal_dirty_data(handle_t *handle, struct buffer_head *bh)
{
      int err = jbd2_journal_dirty_data(handle, bh);
      if (err)
            ext4_journal_abort_handle(__FUNCTION__, __FUNCTION__,
                                    bh, handle, err);
      return err;
}

/* For write_end() in data=journal mode */
static int write_end_fn(handle_t *handle, struct buffer_head *bh)
{
      if (!buffer_mapped(bh) || buffer_freed(bh))
            return 0;
      set_buffer_uptodate(bh);
      return ext4_journal_dirty_metadata(handle, bh);
}

/*
 * Generic write_end handler for ordered and writeback ext4 journal modes.
 * We can't use generic_write_end, because that unlocks the page and we need to
 * unlock the page after ext4_journal_stop, but ext4_journal_stop must run
 * after block_write_end.
 */
static int ext4_generic_write_end(struct file *file,
                        struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *page, void *fsdata)
{
      struct inode *inode = file->f_mapping->host;

      copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);

      if (pos+copied > inode->i_size) {
            i_size_write(inode, pos+copied);
            mark_inode_dirty(inode);
      }

      return copied;
}

/*
 * We need to pick up the new inode size which generic_commit_write gave us
 * `file' can be NULL - eg, when called from page_symlink().
 *
 * ext4 never places buffers on inode->i_mapping->private_list.  metadata
 * buffers are managed internally.
 */
static int ext4_ordered_write_end(struct file *file,
                        struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *page, void *fsdata)
{
      handle_t *handle = ext4_journal_current_handle();
      struct inode *inode = file->f_mapping->host;
      unsigned from, to;
      int ret = 0, ret2;

      from = pos & (PAGE_CACHE_SIZE - 1);
      to = from + len;

      ret = walk_page_buffers(handle, page_buffers(page),
            from, to, NULL, ext4_journal_dirty_data);

      if (ret == 0) {
            /*
             * generic_write_end() will run mark_inode_dirty() if i_size
             * changes.  So let's piggyback the i_disksize mark_inode_dirty
             * into that.
             */
            loff_t new_i_size;

            new_i_size = pos + copied;
            if (new_i_size > EXT4_I(inode)->i_disksize)
                  EXT4_I(inode)->i_disksize = new_i_size;
            copied = ext4_generic_write_end(file, mapping, pos, len, copied,
                                          page, fsdata);
            if (copied < 0)
                  ret = copied;
      }
      ret2 = ext4_journal_stop(handle);
      if (!ret)
            ret = ret2;
      unlock_page(page);
      page_cache_release(page);

      return ret ? ret : copied;
}

static int ext4_writeback_write_end(struct file *file,
                        struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *page, void *fsdata)
{
      handle_t *handle = ext4_journal_current_handle();
      struct inode *inode = file->f_mapping->host;
      int ret = 0, ret2;
      loff_t new_i_size;

      new_i_size = pos + copied;
      if (new_i_size > EXT4_I(inode)->i_disksize)
            EXT4_I(inode)->i_disksize = new_i_size;

      copied = ext4_generic_write_end(file, mapping, pos, len, copied,
                                          page, fsdata);
      if (copied < 0)
            ret = copied;

      ret2 = ext4_journal_stop(handle);
      if (!ret)
            ret = ret2;
      unlock_page(page);
      page_cache_release(page);

      return ret ? ret : copied;
}

static int ext4_journalled_write_end(struct file *file,
                        struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *page, void *fsdata)
{
      handle_t *handle = ext4_journal_current_handle();
      struct inode *inode = mapping->host;
      int ret = 0, ret2;
      int partial = 0;
      unsigned from, to;

      from = pos & (PAGE_CACHE_SIZE - 1);
      to = from + len;

      if (copied < len) {
            if (!PageUptodate(page))
                  copied = 0;
            page_zero_new_buffers(page, from+copied, to);
      }

      ret = walk_page_buffers(handle, page_buffers(page), from,
                        to, &partial, write_end_fn);
      if (!partial)
            SetPageUptodate(page);
      if (pos+copied > inode->i_size)
            i_size_write(inode, pos+copied);
      EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
      if (inode->i_size > EXT4_I(inode)->i_disksize) {
            EXT4_I(inode)->i_disksize = inode->i_size;
            ret2 = ext4_mark_inode_dirty(handle, inode);
            if (!ret)
                  ret = ret2;
      }

      ret2 = ext4_journal_stop(handle);
      if (!ret)
            ret = ret2;
      unlock_page(page);
      page_cache_release(page);

      return ret ? ret : copied;
}

/*
 * bmap() is special.  It gets used by applications such as lilo and by
 * the swapper to find the on-disk block of a specific piece of data.
 *
 * Naturally, this is dangerous if the block concerned is still in the
 * journal.  If somebody makes a swapfile on an ext4 data-journaling
 * filesystem and enables swap, then they may get a nasty shock when the
 * data getting swapped to that swapfile suddenly gets overwritten by
 * the original zero's written out previously to the journal and
 * awaiting writeback in the kernel's buffer cache.
 *
 * So, if we see any bmap calls here on a modified, data-journaled file,
 * take extra steps to flush any blocks which might be in the cache.
 */
static sector_t ext4_bmap(struct address_space *mapping, sector_t block)
{
      struct inode *inode = mapping->host;
      journal_t *journal;
      int err;

      if (EXT4_I(inode)->i_state & EXT4_STATE_JDATA) {
            /*
             * This is a REALLY heavyweight approach, but the use of
             * bmap on dirty files is expected to be extremely rare:
             * only if we run lilo or swapon on a freshly made file
             * do we expect this to happen.
             *
             * (bmap requires CAP_SYS_RAWIO so this does not
             * represent an unprivileged user DOS attack --- we'd be
             * in trouble if mortal users could trigger this path at
             * will.)
             *
             * NB. EXT4_STATE_JDATA is not set on files other than
             * regular files.  If somebody wants to bmap a directory
             * or symlink and gets confused because the buffer
             * hasn't yet been flushed to disk, they deserve
             * everything they get.
             */

            EXT4_I(inode)->i_state &= ~EXT4_STATE_JDATA;
            journal = EXT4_JOURNAL(inode);
            jbd2_journal_lock_updates(journal);
            err = jbd2_journal_flush(journal);
            jbd2_journal_unlock_updates(journal);

            if (err)
                  return 0;
      }

      return generic_block_bmap(mapping,block,ext4_get_block);
}

static int bget_one(handle_t *handle, struct buffer_head *bh)
{
      get_bh(bh);
      return 0;
}

static int bput_one(handle_t *handle, struct buffer_head *bh)
{
      put_bh(bh);
      return 0;
}

static int jbd2_journal_dirty_data_fn(handle_t *handle, struct buffer_head *bh)
{
      if (buffer_mapped(bh))
            return ext4_journal_dirty_data(handle, bh);
      return 0;
}

/*
 * Note that we always start a transaction even if we're not journalling
 * data.  This is to preserve ordering: any hole instantiation within
 * __block_write_full_page -> ext4_get_block() should be journalled
 * along with the data so we don't crash and then get metadata which
 * refers to old data.
 *
 * In all journalling modes block_write_full_page() will start the I/O.
 *
 * Problem:
 *
 *    ext4_writepage() -> kmalloc() -> __alloc_pages() -> page_launder() ->
 *          ext4_writepage()
 *
 * Similar for:
 *
 *    ext4_file_write() -> generic_file_write() -> __alloc_pages() -> ...
 *
 * Same applies to ext4_get_block().  We will deadlock on various things like
 * lock_journal and i_truncate_mutex.
 *
 * Setting PF_MEMALLOC here doesn't work - too many internal memory
 * allocations fail.
 *
 * 16May01: If we're reentered then journal_current_handle() will be
 *        non-zero. We simply *return*.
 *
 * 1 July 2001: @@@ FIXME:
 *   In journalled data mode, a data buffer may be metadata against the
 *   current transaction.  But the same file is part of a shared mapping
 *   and someone does a writepage() on it.
 *
 *   We will move the buffer onto the async_data list, but *after* it has
 *   been dirtied. So there's a small window where we have dirty data on
 *   BJ_Metadata.
 *
 *   Note that this only applies to the last partial page in the file.  The
 *   bit which block_write_full_page() uses prepare/commit for.  (That's
 *   broken code anyway: it's wrong for msync()).
 *
 *   It's a rare case: affects the final partial page, for journalled data
 *   where the file is subject to bith write() and writepage() in the same
 *   transction.  To fix it we'll need a custom block_write_full_page().
 *   We'll probably need that anyway for journalling writepage() output.
 *
 * We don't honour synchronous mounts for writepage().  That would be
 * disastrous.  Any write() or metadata operation will sync the fs for
 * us.
 *
 * AKPM2: if all the page's buffers are mapped to disk and !data=journal,
 * we don't need to open a transaction here.
 */
static int ext4_ordered_writepage(struct page *page,
                        struct writeback_control *wbc)
{
      struct inode *inode = page->mapping->host;
      struct buffer_head *page_bufs;
      handle_t *handle = NULL;
      int ret = 0;
      int err;

      J_ASSERT(PageLocked(page));

      /*
       * We give up here if we're reentered, because it might be for a
       * different filesystem.
       */
      if (ext4_journal_current_handle())
            goto out_fail;

      handle = ext4_journal_start(inode, ext4_writepage_trans_blocks(inode));

      if (IS_ERR(handle)) {
            ret = PTR_ERR(handle);
            goto out_fail;
      }

      if (!page_has_buffers(page)) {
            create_empty_buffers(page, inode->i_sb->s_blocksize,
                        (1 << BH_Dirty)|(1 << BH_Uptodate));
      }
      page_bufs = page_buffers(page);
      walk_page_buffers(handle, page_bufs, 0,
                  PAGE_CACHE_SIZE, NULL, bget_one);

      ret = block_write_full_page(page, ext4_get_block, wbc);

      /*
       * The page can become unlocked at any point now, and
       * truncate can then come in and change things.  So we
       * can't touch *page from now on.  But *page_bufs is
       * safe due to elevated refcount.
       */

      /*
       * And attach them to the current transaction.  But only if
       * block_write_full_page() succeeded.  Otherwise they are unmapped,
       * and generally junk.
       */
      if (ret == 0) {
            err = walk_page_buffers(handle, page_bufs, 0, PAGE_CACHE_SIZE,
                              NULL, jbd2_journal_dirty_data_fn);
            if (!ret)
                  ret = err;
      }
      walk_page_buffers(handle, page_bufs, 0,
                  PAGE_CACHE_SIZE, NULL, bput_one);
      err = ext4_journal_stop(handle);
      if (!ret)
            ret = err;
      return ret;

out_fail:
      redirty_page_for_writepage(wbc, page);
      unlock_page(page);
      return ret;
}

static int ext4_writeback_writepage(struct page *page,
                        struct writeback_control *wbc)
{
      struct inode *inode = page->mapping->host;
      handle_t *handle = NULL;
      int ret = 0;
      int err;

      if (ext4_journal_current_handle())
            goto out_fail;

      handle = ext4_journal_start(inode, ext4_writepage_trans_blocks(inode));
      if (IS_ERR(handle)) {
            ret = PTR_ERR(handle);
            goto out_fail;
      }

      if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode))
            ret = nobh_writepage(page, ext4_get_block, wbc);
      else
            ret = block_write_full_page(page, ext4_get_block, wbc);

      err = ext4_journal_stop(handle);
      if (!ret)
            ret = err;
      return ret;

out_fail:
      redirty_page_for_writepage(wbc, page);
      unlock_page(page);
      return ret;
}

static int ext4_journalled_writepage(struct page *page,
                        struct writeback_control *wbc)
{
      struct inode *inode = page->mapping->host;
      handle_t *handle = NULL;
      int ret = 0;
      int err;

      if (ext4_journal_current_handle())
            goto no_write;

      handle = ext4_journal_start(inode, ext4_writepage_trans_blocks(inode));
      if (IS_ERR(handle)) {
            ret = PTR_ERR(handle);
            goto no_write;
      }

      if (!page_has_buffers(page) || PageChecked(page)) {
            /*
             * It's mmapped pagecache.  Add buffers and journal it.  There
             * doesn't seem much point in redirtying the page here.
             */
            ClearPageChecked(page);
            ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE,
                              ext4_get_block);
            if (ret != 0) {
                  ext4_journal_stop(handle);
                  goto out_unlock;
            }
            ret = walk_page_buffers(handle, page_buffers(page), 0,
                  PAGE_CACHE_SIZE, NULL, do_journal_get_write_access);

            err = walk_page_buffers(handle, page_buffers(page), 0,
                        PAGE_CACHE_SIZE, NULL, write_end_fn);
            if (ret == 0)
                  ret = err;
            EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
            unlock_page(page);
      } else {
            /*
             * It may be a page full of checkpoint-mode buffers.  We don't
             * really know unless we go poke around in the buffer_heads.
             * But block_write_full_page will do the right thing.
             */
            ret = block_write_full_page(page, ext4_get_block, wbc);
      }
      err = ext4_journal_stop(handle);
      if (!ret)
            ret = err;
out:
      return ret;

no_write:
      redirty_page_for_writepage(wbc, page);
out_unlock:
      unlock_page(page);
      goto out;
}

static int ext4_readpage(struct file *file, struct page *page)
{
      return mpage_readpage(page, ext4_get_block);
}

static int
ext4_readpages(struct file *file, struct address_space *mapping,
            struct list_head *pages, unsigned nr_pages)
{
      return mpage_readpages(mapping, pages, nr_pages, ext4_get_block);
}

static void ext4_invalidatepage(struct page *page, unsigned long offset)
{
      journal_t *journal = EXT4_JOURNAL(page->mapping->host);

      /*
       * If it's a full truncate we just forget about the pending dirtying
       */
      if (offset == 0)
            ClearPageChecked(page);

      jbd2_journal_invalidatepage(journal, page, offset);
}

static int ext4_releasepage(struct page *page, gfp_t wait)
{
      journal_t *journal = EXT4_JOURNAL(page->mapping->host);

      WARN_ON(PageChecked(page));
      if (!page_has_buffers(page))
            return 0;
      return jbd2_journal_try_to_free_buffers(journal, page, wait);
}

/*
 * If the O_DIRECT write will extend the file then add this inode to the
 * orphan list.  So recovery will truncate it back to the original size
 * if the machine crashes during the write.
 *
 * If the O_DIRECT write is intantiating holes inside i_size and the machine
 * crashes then stale disk data _may_ be exposed inside the file.
 */
static ssize_t ext4_direct_IO(int rw, struct kiocb *iocb,
                  const struct iovec *iov, loff_t offset,
                  unsigned long nr_segs)
{
      struct file *file = iocb->ki_filp;
      struct inode *inode = file->f_mapping->host;
      struct ext4_inode_info *ei = EXT4_I(inode);
      handle_t *handle = NULL;
      ssize_t ret;
      int orphan = 0;
      size_t count = iov_length(iov, nr_segs);

      if (rw == WRITE) {
            loff_t final_size = offset + count;

            handle = ext4_journal_start(inode, DIO_CREDITS);
            if (IS_ERR(handle)) {
                  ret = PTR_ERR(handle);
                  goto out;
            }
            if (final_size > inode->i_size) {
                  ret = ext4_orphan_add(handle, inode);
                  if (ret)
                        goto out_stop;
                  orphan = 1;
                  ei->i_disksize = inode->i_size;
            }
      }

      ret = blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
                         offset, nr_segs,
                         ext4_get_block, NULL);

      /*
       * Reacquire the handle: ext4_get_block() can restart the transaction
       */
      handle = ext4_journal_current_handle();

out_stop:
      if (handle) {
            int err;

            if (orphan && inode->i_nlink)
                  ext4_orphan_del(handle, inode);
            if (orphan && ret > 0) {
                  loff_t end = offset + ret;
                  if (end > inode->i_size) {
                        ei->i_disksize = end;
                        i_size_write(inode, end);
                        /*
                         * We're going to return a positive `ret'
                         * here due to non-zero-length I/O, so there's
                         * no way of reporting error returns from
                         * ext4_mark_inode_dirty() to userspace.  So
                         * ignore it.
                         */
                        ext4_mark_inode_dirty(handle, inode);
                  }
            }
            err = ext4_journal_stop(handle);
            if (ret == 0)
                  ret = err;
      }
out:
      return ret;
}

/*
 * Pages can be marked dirty completely asynchronously from ext4's journalling
 * activity.  By filemap_sync_pte(), try_to_unmap_one(), etc.  We cannot do
 * much here because ->set_page_dirty is called under VFS locks.  The page is
 * not necessarily locked.
 *
 * We cannot just dirty the page and leave attached buffers clean, because the
 * buffers' dirty state is "definitive".  We cannot just set the buffers dirty
 * or jbddirty because all the journalling code will explode.
 *
 * So what we do is to mark the page "pending dirty" and next time writepage
 * is called, propagate that into the buffers appropriately.
 */
static int ext4_journalled_set_page_dirty(struct page *page)
{
      SetPageChecked(page);
      return __set_page_dirty_nobuffers(page);
}

static const struct address_space_operations ext4_ordered_aops = {
      .readpage   = ext4_readpage,
      .readpages  = ext4_readpages,
      .writepage  = ext4_ordered_writepage,
      .sync_page  = block_sync_page,
      .write_begin      = ext4_write_begin,
      .write_end  = ext4_ordered_write_end,
      .bmap       = ext4_bmap,
      .invalidatepage   = ext4_invalidatepage,
      .releasepage      = ext4_releasepage,
      .direct_IO  = ext4_direct_IO,
      .migratepage      = buffer_migrate_page,
};

static const struct address_space_operations ext4_writeback_aops = {
      .readpage   = ext4_readpage,
      .readpages  = ext4_readpages,
      .writepage  = ext4_writeback_writepage,
      .sync_page  = block_sync_page,
      .write_begin      = ext4_write_begin,
      .write_end  = ext4_writeback_write_end,
      .bmap       = ext4_bmap,
      .invalidatepage   = ext4_invalidatepage,
      .releasepage      = ext4_releasepage,
      .direct_IO  = ext4_direct_IO,
      .migratepage      = buffer_migrate_page,
};

static const struct address_space_operations ext4_journalled_aops = {
      .readpage   = ext4_readpage,
      .readpages  = ext4_readpages,
      .writepage  = ext4_journalled_writepage,
      .sync_page  = block_sync_page,
      .write_begin      = ext4_write_begin,
      .write_end  = ext4_journalled_write_end,
      .set_page_dirty   = ext4_journalled_set_page_dirty,
      .bmap       = ext4_bmap,
      .invalidatepage   = ext4_invalidatepage,
      .releasepage      = ext4_releasepage,
};

void ext4_set_aops(struct inode *inode)
{
      if (ext4_should_order_data(inode))
            inode->i_mapping->a_ops = &ext4_ordered_aops;
      else if (ext4_should_writeback_data(inode))
            inode->i_mapping->a_ops = &ext4_writeback_aops;
      else
            inode->i_mapping->a_ops = &ext4_journalled_aops;
}

/*
 * ext4_block_truncate_page() zeroes out a mapping from file offset `from'
 * up to the end of the block which corresponds to `from'.
 * This required during truncate. We need to physically zero the tail end
 * of that block so it doesn't yield old data if the file is later grown.
 */
int ext4_block_truncate_page(handle_t *handle, struct page *page,
            struct address_space *mapping, loff_t from)
{
      ext4_fsblk_t index = from >> PAGE_CACHE_SHIFT;
      unsigned offset = from & (PAGE_CACHE_SIZE-1);
      unsigned blocksize, iblock, length, pos;
      struct inode *inode = mapping->host;
      struct buffer_head *bh;
      int err = 0;

      blocksize = inode->i_sb->s_blocksize;
      length = blocksize - (offset & (blocksize - 1));
      iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);

      /*
       * For "nobh" option,  we can only work if we don't need to
       * read-in the page - otherwise we create buffers to do the IO.
       */
      if (!page_has_buffers(page) && test_opt(inode->i_sb, NOBH) &&
           ext4_should_writeback_data(inode) && PageUptodate(page)) {
            zero_user_page(page, offset, length, KM_USER0);
            set_page_dirty(page);
            goto unlock;
      }

      if (!page_has_buffers(page))
            create_empty_buffers(page, blocksize, 0);

      /* Find the buffer that contains "offset" */
      bh = page_buffers(page);
      pos = blocksize;
      while (offset >= pos) {
            bh = bh->b_this_page;
            iblock++;
            pos += blocksize;
      }

      err = 0;
      if (buffer_freed(bh)) {
            BUFFER_TRACE(bh, "freed: skip");
            goto unlock;
      }

      if (!buffer_mapped(bh)) {
            BUFFER_TRACE(bh, "unmapped");
            ext4_get_block(inode, iblock, bh, 0);
            /* unmapped? It's a hole - nothing to do */
            if (!buffer_mapped(bh)) {
                  BUFFER_TRACE(bh, "still unmapped");
                  goto unlock;
            }
      }

      /* Ok, it's mapped. Make sure it's up-to-date */
      if (PageUptodate(page))
            set_buffer_uptodate(bh);

      if (!buffer_uptodate(bh)) {
            err = -EIO;
            ll_rw_block(READ, 1, &bh);
            wait_on_buffer(bh);
            /* Uhhuh. Read error. Complain and punt. */
            if (!buffer_uptodate(bh))
                  goto unlock;
      }

      if (ext4_should_journal_data(inode)) {
            BUFFER_TRACE(bh, "get write access");
            err = ext4_journal_get_write_access(handle, bh);
            if (err)
                  goto unlock;
      }

      zero_user_page(page, offset, length, KM_USER0);

      BUFFER_TRACE(bh, "zeroed end of block");

      err = 0;
      if (ext4_should_journal_data(inode)) {
            err = ext4_journal_dirty_metadata(handle, bh);
      } else {
            if (ext4_should_order_data(inode))
                  err = ext4_journal_dirty_data(handle, bh);
            mark_buffer_dirty(bh);
      }

unlock:
      unlock_page(page);
      page_cache_release(page);
      return err;
}

/*
 * Probably it should be a library function... search for first non-zero word
 * or memcmp with zero_page, whatever is better for particular architecture.
 * Linus?
 */
static inline int all_zeroes(__le32 *p, __le32 *q)
{
      while (p < q)
            if (*p++)
                  return 0;
      return 1;
}

/**
 *    ext4_find_shared - find the indirect blocks for partial truncation.
 *    @inode:       inode in question
 *    @depth:       depth of the affected branch
 *    @offsets: offsets of pointers in that branch (see ext4_block_to_path)
 *    @chain:       place to store the pointers to partial indirect blocks
 *    @top:   place to the (detached) top of branch
 *
 *    This is a helper function used by ext4_truncate().
 *
 *    When we do truncate() we may have to clean the ends of several
 *    indirect blocks but leave the blocks themselves alive. Block is
 *    partially truncated if some data below the new i_size is refered
 *    from it (and it is on the path to the first completely truncated
 *    data block, indeed).  We have to free the top of that path along
 *    with everything to the right of the path. Since no allocation
 *    past the truncation point is possible until ext4_truncate()
 *    finishes, we may safely do the latter, but top of branch may
 *    require special attention - pageout below the truncation point
 *    might try to populate it.
 *
 *    We atomically detach the top of branch from the tree, store the
 *    block number of its root in *@top, pointers to buffer_heads of
 *    partially truncated blocks - in @chain[].bh and pointers to
 *    their last elements that should not be removed - in
 *    @chain[].p. Return value is the pointer to last filled element
 *    of @chain.
 *
 *    The work left to caller to do the actual freeing of subtrees:
 *          a) free the subtree starting from *@top
 *          b) free the subtrees whose roots are stored in
 *                (@chain[i].p+1 .. end of @chain[i].bh->b_data)
 *          c) free the subtrees growing from the inode past the @chain[0].
 *                (no partially truncated stuff there).  */

static Indirect *ext4_find_shared(struct inode *inode, int depth,
                  int offsets[4], Indirect chain[4], __le32 *top)
{
      Indirect *partial, *p;
      int k, err;

      *top = 0;
      /* Make k index the deepest non-null offest + 1 */
      for (k = depth; k > 1 && !offsets[k-1]; k--)
            ;
      partial = ext4_get_branch(inode, k, offsets, chain, &err);
      /* Writer: pointers */
      if (!partial)
            partial = chain + k-1;
      /*
       * If the branch acquired continuation since we've looked at it -
       * fine, it should all survive and (new) top doesn't belong to us.
       */
      if (!partial->key && *partial->p)
            /* Writer: end */
            goto no_top;
      for (p=partial; p>chain && all_zeroes((__le32*)p->bh->b_data,p->p); p--)
            ;
      /*
       * OK, we've found the last block that must survive. The rest of our
       * branch should be detached before unlocking. However, if that rest
       * of branch is all ours and does not grow immediately from the inode
       * it's easier to cheat and just decrement partial->p.
       */
      if (p == chain + k - 1 && p > chain) {
            p->p--;
      } else {
            *top = *p->p;
            /* Nope, don't do this in ext4.  Must leave the tree intact */
#if 0
            *p->p = 0;
#endif
      }
      /* Writer: end */

      while(partial > p) {
            brelse(partial->bh);
            partial--;
      }
no_top:
      return partial;
}

/*
 * Zero a number of block pointers in either an inode or an indirect block.
 * If we restart the transaction we must again get write access to the
 * indirect block for further modification.
 *
 * We release `count' blocks on disk, but (last - first) may be greater
 * than `count' because there can be holes in there.
 */
static void ext4_clear_blocks(handle_t *handle, struct inode *inode,
            struct buffer_head *bh, ext4_fsblk_t block_to_free,
            unsigned long count, __le32 *first, __le32 *last)
{
      __le32 *p;
      if (try_to_extend_transaction(handle, inode)) {
            if (bh) {
                  BUFFER_TRACE(bh, "call ext4_journal_dirty_metadata");
                  ext4_journal_dirty_metadata(handle, bh);
            }
            ext4_mark_inode_dirty(handle, inode);
            ext4_journal_test_restart(handle, inode);
            if (bh) {
                  BUFFER_TRACE(bh, "retaking write access");
                  ext4_journal_get_write_access(handle, bh);
            }
      }

      /*
       * Any buffers which are on the journal will be in memory. We find
       * them on the hash table so jbd2_journal_revoke() will run jbd2_journal_forget()
       * on them.  We've already detached each block from the file, so
       * bforget() in jbd2_journal_forget() should be safe.
       *
       * AKPM: turn on bforget in jbd2_journal_forget()!!!
       */
      for (p = first; p < last; p++) {
            u32 nr = le32_to_cpu(*p);
            if (nr) {
                  struct buffer_head *bh;

                  *p = 0;
                  bh = sb_find_get_block(inode->i_sb, nr);
                  ext4_forget(handle, 0, inode, bh, nr);
            }
      }

      ext4_free_blocks(handle, inode, block_to_free, count);
}

/**
 * ext4_free_data - free a list of data blocks
 * @handle: handle for this transaction
 * @inode:  inode we are dealing with
 * @this_bh:      indirect buffer_head which contains *@first and *@last
 * @first:  array of block numbers
 * @last:   points immediately past the end of array
 *
 * We are freeing all blocks refered from that array (numbers are stored as
 * little-endian 32-bit) and updating @inode->i_blocks appropriately.
 *
 * We accumulate contiguous runs of blocks to free.  Conveniently, if these
 * blocks are contiguous then releasing them at one time will only affect one
 * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
 * actually use a lot of journal space.
 *
 * @this_bh will be %NULL if @first and @last point into the inode's direct
 * block pointers.
 */
static void ext4_free_data(handle_t *handle, struct inode *inode,
                     struct buffer_head *this_bh,
                     __le32 *first, __le32 *last)
{
      ext4_fsblk_t block_to_free = 0;    /* Starting block # of a run */
      unsigned long count = 0;          /* Number of blocks in the run */
      __le32 *block_to_free_p = NULL;         /* Pointer into inode/ind
                                     corresponding to
                                     block_to_free */
      ext4_fsblk_t nr;            /* Current block # */
      __le32 *p;                  /* Pointer into inode/ind
                                     for current block */
      int err;

      if (this_bh) {                      /* For indirect block */
            BUFFER_TRACE(this_bh, "get_write_access");
            err = ext4_journal_get_write_access(handle, this_bh);
            /* Important: if we can't update the indirect pointers
             * to the blocks, we can't free them. */
            if (err)
                  return;
      }

      for (p = first; p < last; p++) {
            nr = le32_to_cpu(*p);
            if (nr) {
                  /* accumulate blocks to free if they're contiguous */
                  if (count == 0) {
                        block_to_free = nr;
                        block_to_free_p = p;
                        count = 1;
                  } else if (nr == block_to_free + count) {
                        count++;
                  } else {
                        ext4_clear_blocks(handle, inode, this_bh,
                                      block_to_free,
                                      count, block_to_free_p, p);
                        block_to_free = nr;
                        block_to_free_p = p;
                        count = 1;
                  }
            }
      }

      if (count > 0)
            ext4_clear_blocks(handle, inode, this_bh, block_to_free,
                          count, block_to_free_p, p);

      if (this_bh) {
            BUFFER_TRACE(this_bh, "call ext4_journal_dirty_metadata");
            ext4_journal_dirty_metadata(handle, this_bh);
      }
}

/**
 *    ext4_free_branches - free an array of branches
 *    @handle: JBD handle for this transaction
 *    @inode:     inode we are dealing with
 *    @parent_bh: the buffer_head which contains *@first and *@last
 *    @first:     array of block numbers
 *    @last:      pointer immediately past the end of array
 *    @depth:     depth of the branches to free
 *
 *    We are freeing all blocks refered from these branches (numbers are
 *    stored as little-endian 32-bit) and updating @inode->i_blocks
 *    appropriately.
 */
static void ext4_free_branches(handle_t *handle, struct inode *inode,
                         struct buffer_head *parent_bh,
                         __le32 *first, __le32 *last, int depth)
{
      ext4_fsblk_t nr;
      __le32 *p;

      if (is_handle_aborted(handle))
            return;

      if (depth--) {
            struct buffer_head *bh;
            int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
            p = last;
            while (--p >= first) {
                  nr = le32_to_cpu(*p);
                  if (!nr)
                        continue;         /* A hole */

                  /* Go read the buffer for the next level down */
                  bh = sb_bread(inode->i_sb, nr);

                  /*
                   * A read failure? Report error and clear slot
                   * (should be rare).
                   */
                  if (!bh) {
                        ext4_error(inode->i_sb, "ext4_free_branches",
                                 "Read failure, inode=%lu, block=%llu",
                                 inode->i_ino, nr);
                        continue;
                  }

                  /* This zaps the entire block.  Bottom up. */
                  BUFFER_TRACE(bh, "free child branches");
                  ext4_free_branches(handle, inode, bh,
                                 (__le32*)bh->b_data,
                                 (__le32*)bh->b_data + addr_per_block,
                                 depth);

                  /*
                   * We've probably journalled the indirect block several
                   * times during the truncate.  But it's no longer
                   * needed and we now drop it from the transaction via
                   * jbd2_journal_revoke().
                   *
                   * That's easy if it's exclusively part of this
                   * transaction.  But if it's part of the committing
                   * transaction then jbd2_journal_forget() will simply
                   * brelse() it.  That means that if the underlying
                   * block is reallocated in ext4_get_block(),
                   * unmap_underlying_metadata() will find this block
                   * and will try to get rid of it.  damn, damn.
                   *
                   * If this block has already been committed to the
                   * journal, a revoke record will be written.  And
                   * revoke records must be emitted *before* clearing
                   * this block's bit in the bitmaps.
                   */
                  ext4_forget(handle, 1, inode, bh, bh->b_blocknr);

                  /*
                   * Everything below this this pointer has been
                   * released.  Now let this top-of-subtree go.
                   *
                   * We want the freeing of this indirect block to be
                   * atomic in the journal with the updating of the
                   * bitmap block which owns it.  So make some room in
                   * the journal.
                   *
                   * We zero the parent pointer *after* freeing its
                   * pointee in the bitmaps, so if extend_transaction()
                   * for some reason fails to put the bitmap changes and
                   * the release into the same transaction, recovery
                   * will merely complain about releasing a free block,
                   * rather than leaking blocks.
                   */
                  if (is_handle_aborted(handle))
                        return;
                  if (try_to_extend_transaction(handle, inode)) {
                        ext4_mark_inode_dirty(handle, inode);
                        ext4_journal_test_restart(handle, inode);
                  }

                  ext4_free_blocks(handle, inode, nr, 1);

                  if (parent_bh) {
                        /*
                         * The block which we have just freed is
                         * pointed to by an indirect block: journal it
                         */
                        BUFFER_TRACE(parent_bh, "get_write_access");
                        if (!ext4_journal_get_write_access(handle,
                                                   parent_bh)){
                              *p = 0;
                              BUFFER_TRACE(parent_bh,
                              "call ext4_journal_dirty_metadata");
                              ext4_journal_dirty_metadata(handle,
                                                    parent_bh);
                        }
                  }
            }
      } else {
            /* We have reached the bottom of the tree. */
            BUFFER_TRACE(parent_bh, "free data blocks");
            ext4_free_data(handle, inode, parent_bh, first, last);
      }
}

/*
 * ext4_truncate()
 *
 * We block out ext4_get_block() block instantiations across the entire
 * transaction, and VFS/VM ensures that ext4_truncate() cannot run
 * simultaneously on behalf of the same inode.
 *
 * As we work through the truncate and commmit bits of it to the journal there
 * is one core, guiding principle: the file's tree must always be consistent on
 * disk.  We must be able to restart the truncate after a crash.
 *
 * The file's tree may be transiently inconsistent in memory (although it
 * probably isn't), but whenever we close off and commit a journal transaction,
 * the contents of (the filesystem + the journal) must be consistent and
 * restartable.  It's pretty simple, really: bottom up, right to left (although
 * left-to-right works OK too).
 *
 * Note that at recovery time, journal replay occurs *before* the restart of
 * truncate against the orphan inode list.
 *
 * The committed inode has the new, desired i_size (which is the same as
 * i_disksize in this case).  After a crash, ext4_orphan_cleanup() will see
 * that this inode's truncate did not complete and it will again call
 * ext4_truncate() to have another go.  So there will be instantiated blocks
 * to the right of the truncation point in a crashed ext4 filesystem.  But
 * that's fine - as long as they are linked from the inode, the post-crash
 * ext4_truncate() run will find them and release them.
 */
void ext4_truncate(struct inode *inode)
{
      handle_t *handle;
      struct ext4_inode_info *ei = EXT4_I(inode);
      __le32 *i_data = ei->i_data;
      int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
      struct address_space *mapping = inode->i_mapping;
      int offsets[4];
      Indirect chain[4];
      Indirect *partial;
      __le32 nr = 0;
      int n;
      long last_block;
      unsigned blocksize = inode->i_sb->s_blocksize;
      struct page *page;

      if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
          S_ISLNK(inode->i_mode)))
            return;
      if (ext4_inode_is_fast_symlink(inode))
            return;
      if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
            return;

      /*
       * We have to lock the EOF page here, because lock_page() nests
       * outside jbd2_journal_start().
       */
      if ((inode->i_size & (blocksize - 1)) == 0) {
            /* Block boundary? Nothing to do */
            page = NULL;
      } else {
            page = grab_cache_page(mapping,
                        inode->i_size >> PAGE_CACHE_SHIFT);
            if (!page)
                  return;
      }

      if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
            return ext4_ext_truncate(inode, page);

      handle = start_transaction(inode);
      if (IS_ERR(handle)) {
            if (page) {
                  clear_highpage(page);
                  flush_dcache_page(page);
                  unlock_page(page);
                  page_cache_release(page);
            }
            return;           /* AKPM: return what? */
      }

      last_block = (inode->i_size + blocksize-1)
                              >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);

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

      n = ext4_block_to_path(inode, last_block, offsets, NULL);
      if (n == 0)
            goto out_stop;    /* error */

      /*
       * OK.  This truncate is going to happen.  We add the inode to the
       * orphan list, so that if this truncate spans multiple transactions,
       * and we crash, we will resume the truncate when the filesystem
       * recovers.  It also marks the inode dirty, to catch the new size.
       *
       * Implication: the file must always be in a sane, consistent
       * truncatable state while each transaction commits.
       */
      if (ext4_orphan_add(handle, inode))
            goto out_stop;

      /*
       * The orphan list entry will now protect us from any crash which
       * occurs before the truncate completes, so it is now safe to propagate
       * the new, shorter inode size (held for now in i_size) into the
       * on-disk inode. We do this via i_disksize, which is the value which
       * ext4 *really* writes onto the disk inode.
       */
      ei->i_disksize = inode->i_size;

      /*
       * From here we block out all ext4_get_block() callers who want to
       * modify the block allocation tree.
       */
      mutex_lock(&ei->truncate_mutex);

      if (n == 1) {           /* direct blocks */
            ext4_free_data(handle, inode, NULL, i_data+offsets[0],
                         i_data + EXT4_NDIR_BLOCKS);
            goto do_indirects;
      }

      partial = ext4_find_shared(inode, n, offsets, chain, &nr);
      /* Kill the top of shared branch (not detached) */
      if (nr) {
            if (partial == chain) {
                  /* Shared branch grows from the inode */
                  ext4_free_branches(handle, inode, NULL,
                                 &nr, &nr+1, (chain+n-1) - partial);
                  *partial->p = 0;
                  /*
                   * We mark the inode dirty prior to restart,
                   * and prior to stop.  No need for it here.
                   */
            } else {
                  /* Shared branch grows from an indirect block */
                  BUFFER_TRACE(partial->bh, "get_write_access");
                  ext4_free_branches(handle, inode, partial->bh,
                              partial->p,
                              partial->p+1, (chain+n-1) - partial);
            }
      }
      /* Clear the ends of indirect blocks on the shared branch */
      while (partial > chain) {
            ext4_free_branches(handle, inode, partial->bh, partial->p + 1,
                           (__le32*)partial->bh->b_data+addr_per_block,
                           (chain+n-1) - partial);
            BUFFER_TRACE(partial->bh, "call brelse");
            brelse (partial->bh);
            partial--;
      }
do_indirects:
      /* Kill the remaining (whole) subtrees */
      switch (offsets[0]) {
      default:
            nr = i_data[EXT4_IND_BLOCK];
            if (nr) {
                  ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
                  i_data[EXT4_IND_BLOCK] = 0;
            }
      case EXT4_IND_BLOCK:
            nr = i_data[EXT4_DIND_BLOCK];
            if (nr) {
                  ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
                  i_data[EXT4_DIND_BLOCK] = 0;
            }
      case EXT4_DIND_BLOCK:
            nr = i_data[EXT4_TIND_BLOCK];
            if (nr) {
                  ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
                  i_data[EXT4_TIND_BLOCK] = 0;
            }
      case EXT4_TIND_BLOCK:
            ;
      }

      ext4_discard_reservation(inode);

      mutex_unlock(&ei->truncate_mutex);
      inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
      ext4_mark_inode_dirty(handle, inode);

      /*
       * 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);

      ext4_journal_stop(handle);
}

static ext4_fsblk_t ext4_get_inode_block(struct super_block *sb,
            unsigned long ino, struct ext4_iloc *iloc)
{
      unsigned long desc, group_desc, block_group;
      unsigned long offset;
      ext4_fsblk_t block;
      struct buffer_head *bh;
      struct ext4_group_desc * gdp;

      if (!ext4_valid_inum(sb, ino)) {
            /*
             * This error is already checked for in namei.c unless we are
             * looking at an NFS filehandle, in which case no error
             * report is needed
             */
            return 0;
      }

      block_group = (ino - 1) / EXT4_INODES_PER_GROUP(sb);
      if (block_group >= EXT4_SB(sb)->s_groups_count) {
            ext4_error(sb,"ext4_get_inode_block","group >= groups count");
            return 0;
      }
      smp_rmb();
      group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
      desc = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
      bh = EXT4_SB(sb)->s_group_desc[group_desc];
      if (!bh) {
            ext4_error (sb, "ext4_get_inode_block",
                      "Descriptor not loaded");
            return 0;
      }

      gdp = (struct ext4_group_desc *)((__u8 *)bh->b_data +
            desc * EXT4_DESC_SIZE(sb));
      /*
       * Figure out the offset within the block group inode table
       */
      offset = ((ino - 1) % EXT4_INODES_PER_GROUP(sb)) *
            EXT4_INODE_SIZE(sb);
      block = ext4_inode_table(sb, gdp) +
            (offset >> EXT4_BLOCK_SIZE_BITS(sb));

      iloc->block_group = block_group;
      iloc->offset = offset & (EXT4_BLOCK_SIZE(sb) - 1);
      return block;
}

/*
 * ext4_get_inode_loc returns with an extra refcount against the inode's
 * underlying buffer_head on success. If 'in_mem' is true, we have all
 * data in memory that is needed to recreate the on-disk version of this
 * inode.
 */
static int __ext4_get_inode_loc(struct inode *inode,
                        struct ext4_iloc *iloc, int in_mem)
{
      ext4_fsblk_t block;
      struct buffer_head *bh;

      block = ext4_get_inode_block(inode->i_sb, inode->i_ino, iloc);
      if (!block)
            return -EIO;

      bh = sb_getblk(inode->i_sb, block);
      if (!bh) {
            ext4_error (inode->i_sb, "ext4_get_inode_loc",
                        "unable to read inode block - "
                        "inode=%lu, block=%llu",
                         inode->i_ino, block);
            return -EIO;
      }
      if (!buffer_uptodate(bh)) {
            lock_buffer(bh);
            if (buffer_uptodate(bh)) {
                  /* someone brought it uptodate while we waited */
                  unlock_buffer(bh);
                  goto has_buffer;
            }

            /*
             * If we have all information of the inode in memory and this
             * is the only valid inode in the block, we need not read the
             * block.
             */
            if (in_mem) {
                  struct buffer_head *bitmap_bh;
                  struct ext4_group_desc *desc;
                  int inodes_per_buffer;
                  int inode_offset, i;
                  int block_group;
                  int start;

                  block_group = (inode->i_ino - 1) /
                              EXT4_INODES_PER_GROUP(inode->i_sb);
                  inodes_per_buffer = bh->b_size /
                        EXT4_INODE_SIZE(inode->i_sb);
                  inode_offset = ((inode->i_ino - 1) %
                              EXT4_INODES_PER_GROUP(inode->i_sb));
                  start = inode_offset & ~(inodes_per_buffer - 1);

                  /* Is the inode bitmap in cache? */
                  desc = ext4_get_group_desc(inode->i_sb,
                                    block_group, NULL);
                  if (!desc)
                        goto make_io;

                  bitmap_bh = sb_getblk(inode->i_sb,
                        ext4_inode_bitmap(inode->i_sb, desc));
                  if (!bitmap_bh)
                        goto make_io;

                  /*
                   * If the inode bitmap isn't in cache then the
                   * optimisation may end up performing two reads instead
                   * of one, so skip it.
                   */
                  if (!buffer_uptodate(bitmap_bh)) {
                        brelse(bitmap_bh);
                        goto make_io;
                  }
                  for (i = start; i < start + inodes_per_buffer; i++) {
                        if (i == inode_offset)
                              continue;
                        if (ext4_test_bit(i, bitmap_bh->b_data))
                              break;
                  }
                  brelse(bitmap_bh);
                  if (i == start + inodes_per_buffer) {
                        /* all other inodes are free, so skip I/O */
                        memset(bh->b_data, 0, bh->b_size);
                        set_buffer_uptodate(bh);
                        unlock_buffer(bh);
                        goto has_buffer;
                  }
            }

make_io:
            /*
             * There are other valid inodes in the buffer, this inode
             * has in-inode xattrs, or we don't have this inode in memory.
             * Read the block from disk.
             */
            get_bh(bh);
            bh->b_end_io = end_buffer_read_sync;
            submit_bh(READ_META, bh);
            wait_on_buffer(bh);
            if (!buffer_uptodate(bh)) {
                  ext4_error(inode->i_sb, "ext4_get_inode_loc",
                              "unable to read inode block - "
                              "inode=%lu, block=%llu",
                              inode->i_ino, block);
                  brelse(bh);
                  return -EIO;
            }
      }
has_buffer:
      iloc->bh = bh;
      return 0;
}

int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)
{
      /* We have all inode data except xattrs in memory here. */
      return __ext4_get_inode_loc(inode, iloc,
            !(EXT4_I(inode)->i_state & EXT4_STATE_XATTR));
}

void ext4_set_inode_flags(struct inode *inode)
{
      unsigned int flags = EXT4_I(inode)->i_flags;

      inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
      if (flags & EXT4_SYNC_FL)
            inode->i_flags |= S_SYNC;
      if (flags & EXT4_APPEND_FL)
            inode->i_flags |= S_APPEND;
      if (flags & EXT4_IMMUTABLE_FL)
            inode->i_flags |= S_IMMUTABLE;
      if (flags & EXT4_NOATIME_FL)
            inode->i_flags |= S_NOATIME;
      if (flags & EXT4_DIRSYNC_FL)
            inode->i_flags |= S_DIRSYNC;
}

/* Propagate flags from i_flags to EXT4_I(inode)->i_flags */
void ext4_get_inode_flags(struct ext4_inode_info *ei)
{
      unsigned int flags = ei->vfs_inode.i_flags;

      ei->i_flags &= ~(EXT4_SYNC_FL|EXT4_APPEND_FL|
                  EXT4_IMMUTABLE_FL|EXT4_NOATIME_FL|EXT4_DIRSYNC_FL);
      if (flags & S_SYNC)
            ei->i_flags |= EXT4_SYNC_FL;
      if (flags & S_APPEND)
            ei->i_flags |= EXT4_APPEND_FL;
      if (flags & S_IMMUTABLE)
            ei->i_flags |= EXT4_IMMUTABLE_FL;
      if (flags & S_NOATIME)
            ei->i_flags |= EXT4_NOATIME_FL;
      if (flags & S_DIRSYNC)
            ei->i_flags |= EXT4_DIRSYNC_FL;
}

void ext4_read_inode(struct inode * inode)
{
      struct ext4_iloc iloc;
      struct ext4_inode *raw_inode;
      struct ext4_inode_info *ei = EXT4_I(inode);
      struct buffer_head *bh;
      int block;

#ifdef CONFIG_EXT4DEV_FS_POSIX_ACL
      ei->i_acl = EXT4_ACL_NOT_CACHED;
      ei->i_default_acl = EXT4_ACL_NOT_CACHED;
#endif
      ei->i_block_alloc_info = NULL;

      if (__ext4_get_inode_loc(inode, &iloc, 0))
            goto bad_inode;
      bh = iloc.bh;
      raw_inode = ext4_raw_inode(&iloc);
      inode->i_mode = le16_to_cpu(raw_inode->i_mode);
      inode->i_uid = (uid_t)le16_to_cpu(raw_inode->i_uid_low);
      inode->i_gid = (gid_t)le16_to_cpu(raw_inode->i_gid_low);
      if(!(test_opt (inode->i_sb, NO_UID32))) {
            inode->i_uid |= le16_to_cpu(raw_inode->i_uid_high) << 16;
            inode->i_gid |= le16_to_cpu(raw_inode->i_gid_high) << 16;
      }
      inode->i_nlink = le16_to_cpu(raw_inode->i_links_count);
      inode->i_size = le32_to_cpu(raw_inode->i_size);

      ei->i_state = 0;
      ei->i_dir_start_lookup = 0;
      ei->i_dtime = le32_to_cpu(raw_inode->i_dtime);
      /* We now have enough fields to check if the inode was active or not.
       * This is needed because nfsd might try to access dead inodes
       * the test is that same one that e2fsck uses
       * NeilBrown 1999oct15
       */
      if (inode->i_nlink == 0) {
            if (inode->i_mode == 0 ||
                !(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_ORPHAN_FS)) {
                  /* this inode is deleted */
                  brelse (bh);
                  goto bad_inode;
            }
            /* The only unlinked inodes we let through here have
             * valid i_mode and are being read by the orphan
             * recovery code: that's fine, we're about to complete
             * the process of deleting those. */
      }
      inode->i_blocks = le32_to_cpu(raw_inode->i_blocks);
      ei->i_flags = le32_to_cpu(raw_inode->i_flags);
      ei->i_file_acl = le32_to_cpu(raw_inode->i_file_acl);
      if (EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
          cpu_to_le32(EXT4_OS_HURD))
            ei->i_file_acl |=
                  ((__u64)le16_to_cpu(raw_inode->i_file_acl_high)) << 32;
      if (!S_ISREG(inode->i_mode)) {
            ei->i_dir_acl = le32_to_cpu(raw_inode->i_dir_acl);
      } else {
            inode->i_size |=
                  ((__u64)le32_to_cpu(raw_inode->i_size_high)) << 32;
      }
      ei->i_disksize = inode->i_size;
      inode->i_generation = le32_to_cpu(raw_inode->i_generation);
      ei->i_block_group = iloc.block_group;
      /*
       * NOTE! The in-memory inode i_data array is in little-endian order
       * even on big-endian machines: we do NOT byteswap the block numbers!
       */
      for (block = 0; block < EXT4_N_BLOCKS; block++)
            ei->i_data[block] = raw_inode->i_block[block];
      INIT_LIST_HEAD(&ei->i_orphan);

      if (inode->i_ino >= EXT4_FIRST_INO(inode->i_sb) + 1 &&
          EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
            /*
             * When mke2fs creates big inodes it does not zero out
             * the unused bytes above EXT4_GOOD_OLD_INODE_SIZE,
             * so ignore those first few inodes.
             */
            ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
            if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >
                EXT4_INODE_SIZE(inode->i_sb)) {
                  brelse (bh);
                  goto bad_inode;
            }
            if (ei->i_extra_isize == 0) {
                  /* The extra space is currently unused. Use it. */
                  ei->i_extra_isize = sizeof(struct ext4_inode) -
                                  EXT4_GOOD_OLD_INODE_SIZE;
            } else {
                  __le32 *magic = (void *)raw_inode +
                              EXT4_GOOD_OLD_INODE_SIZE +
                              ei->i_extra_isize;
                  if (*magic == cpu_to_le32(EXT4_XATTR_MAGIC))
                         ei->i_state |= EXT4_STATE_XATTR;
            }
      } else
            ei->i_extra_isize = 0;

      EXT4_INODE_GET_XTIME(i_ctime, inode, raw_inode);
      EXT4_INODE_GET_XTIME(i_mtime, inode, raw_inode);
      EXT4_INODE_GET_XTIME(i_atime, inode, raw_inode);
      EXT4_EINODE_GET_XTIME(i_crtime, ei, raw_inode);

      if (S_ISREG(inode->i_mode)) {
            inode->i_op = &ext4_file_inode_operations;
            inode->i_fop = &ext4_file_operations;
            ext4_set_aops(inode);
      } else if (S_ISDIR(inode->i_mode)) {
            inode->i_op = &ext4_dir_inode_operations;
            inode->i_fop = &ext4_dir_operations;
      } else if (S_ISLNK(inode->i_mode)) {
            if (ext4_inode_is_fast_symlink(inode))
                  inode->i_op = &ext4_fast_symlink_inode_operations;
            else {
                  inode->i_op = &ext4_symlink_inode_operations;
                  ext4_set_aops(inode);
            }
      } else {
            inode->i_op = &ext4_special_inode_operations;
            if (raw_inode->i_block[0])
                  init_special_inode(inode, inode->i_mode,
                     old_decode_dev(le32_to_cpu(raw_inode->i_block[0])));
            else
                  init_special_inode(inode, inode->i_mode,
                     new_decode_dev(le32_to_cpu(raw_inode->i_block[1])));
      }
      brelse (iloc.bh);
      ext4_set_inode_flags(inode);
      return;

bad_inode:
      make_bad_inode(inode);
      return;
}

/*
 * Post the struct inode info into an on-disk inode location in the
 * buffer-cache.  This gobbles the caller's reference to the
 * buffer_head in the inode location struct.
 *
 * The caller must have write access to iloc->bh.
 */
static int ext4_do_update_inode(handle_t *handle,
                        struct inode *inode,
                        struct ext4_iloc *iloc)
{
      struct ext4_inode *raw_inode = ext4_raw_inode(iloc);
      struct ext4_inode_info *ei = EXT4_I(inode);
      struct buffer_head *bh = iloc->bh;
      int err = 0, rc, block;

      /* For fields not not tracking in the in-memory inode,
       * initialise them to zero for new inodes. */
      if (ei->i_state & EXT4_STATE_NEW)
            memset(raw_inode, 0, EXT4_SB(inode->i_sb)->s_inode_size);

      ext4_get_inode_flags(ei);
      raw_inode->i_mode = cpu_to_le16(inode->i_mode);
      if(!(test_opt(inode->i_sb, NO_UID32))) {
            raw_inode->i_uid_low = cpu_to_le16(low_16_bits(inode->i_uid));
            raw_inode->i_gid_low = cpu_to_le16(low_16_bits(inode->i_gid));
/*
 * Fix up interoperability with old kernels. Otherwise, old inodes get
 * re-used with the upper 16 bits of the uid/gid intact
 */
            if(!ei->i_dtime) {
                  raw_inode->i_uid_high =
                        cpu_to_le16(high_16_bits(inode->i_uid));
                  raw_inode->i_gid_high =
                        cpu_to_le16(high_16_bits(inode->i_gid));
            } else {
                  raw_inode->i_uid_high = 0;
                  raw_inode->i_gid_high = 0;
            }
      } else {
            raw_inode->i_uid_low =
                  cpu_to_le16(fs_high2lowuid(inode->i_uid));
            raw_inode->i_gid_low =
                  cpu_to_le16(fs_high2lowgid(inode->i_gid));
            raw_inode->i_uid_high = 0;
            raw_inode->i_gid_high = 0;
      }
      raw_inode->i_links_count = cpu_to_le16(inode->i_nlink);
      raw_inode->i_size = cpu_to_le32(ei->i_disksize);

      EXT4_INODE_SET_XTIME(i_ctime, inode, raw_inode);
      EXT4_INODE_SET_XTIME(i_mtime, inode, raw_inode);
      EXT4_INODE_SET_XTIME(i_atime, inode, raw_inode);
      EXT4_EINODE_SET_XTIME(i_crtime, ei, raw_inode);

      raw_inode->i_blocks = cpu_to_le32(inode->i_blocks);
      raw_inode->i_dtime = cpu_to_le32(ei->i_dtime);
      raw_inode->i_flags = cpu_to_le32(ei->i_flags);
      if (EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
          cpu_to_le32(EXT4_OS_HURD))
            raw_inode->i_file_acl_high =
                  cpu_to_le16(ei->i_file_acl >> 32);
      raw_inode->i_file_acl = cpu_to_le32(ei->i_file_acl);
      if (!S_ISREG(inode->i_mode)) {
            raw_inode->i_dir_acl = cpu_to_le32(ei->i_dir_acl);
      } else {
            raw_inode->i_size_high =
                  cpu_to_le32(ei->i_disksize >> 32);
            if (ei->i_disksize > 0x7fffffffULL) {
                  struct super_block *sb = inode->i_sb;
                  if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
                              EXT4_FEATURE_RO_COMPAT_LARGE_FILE) ||
                      EXT4_SB(sb)->s_es->s_rev_level ==
                              cpu_to_le32(EXT4_GOOD_OLD_REV)) {
                         /* If this is the first large file
                        * created, add a flag to the superblock.
                        */
                        err = ext4_journal_get_write_access(handle,
                                    EXT4_SB(sb)->s_sbh);
                        if (err)
                              goto out_brelse;
                        ext4_update_dynamic_rev(sb);
                        EXT4_SET_RO_COMPAT_FEATURE(sb,
                              EXT4_FEATURE_RO_COMPAT_LARGE_FILE);
                        sb->s_dirt = 1;
                        handle->h_sync = 1;
                        err = ext4_journal_dirty_metadata(handle,
                                    EXT4_SB(sb)->s_sbh);
                  }
            }
      }
      raw_inode->i_generation = cpu_to_le32(inode->i_generation);
      if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) {
            if (old_valid_dev(inode->i_rdev)) {
                  raw_inode->i_block[0] =
                        cpu_to_le32(old_encode_dev(inode->i_rdev));
                  raw_inode->i_block[1] = 0;
            } else {
                  raw_inode->i_block[0] = 0;
                  raw_inode->i_block[1] =
                        cpu_to_le32(new_encode_dev(inode->i_rdev));
                  raw_inode->i_block[2] = 0;
            }
      } else for (block = 0; block < EXT4_N_BLOCKS; block++)
            raw_inode->i_block[block] = ei->i_data[block];

      if (ei->i_extra_isize)
            raw_inode->i_extra_isize = cpu_to_le16(ei->i_extra_isize);

      BUFFER_TRACE(bh, "call ext4_journal_dirty_metadata");
      rc = ext4_journal_dirty_metadata(handle, bh);
      if (!err)
            err = rc;
      ei->i_state &= ~EXT4_STATE_NEW;

out_brelse:
      brelse (bh);
      ext4_std_error(inode->i_sb, err);
      return err;
}

/*
 * ext4_write_inode()
 *
 * We are called from a few places:
 *
 * - Within generic_file_write() for O_SYNC files.
 *   Here, there will be no transaction running. We wait for any running
 *   trasnaction to commit.
 *
 * - Within sys_sync(), kupdate and such.
 *   We wait on commit, if tol to.
 *
 * - Within prune_icache() (PF_MEMALLOC == true)
 *   Here we simply return.  We can't afford to block kswapd on the
 *   journal commit.
 *
 * In all cases it is actually safe for us to return without doing anything,
 * because the inode has been copied into a raw inode buffer in
 * ext4_mark_inode_dirty().  This is a correctness thing for O_SYNC and for
 * knfsd.
 *
 * Note that we are absolutely dependent upon all inode dirtiers doing the
 * right thing: they *must* call mark_inode_dirty() after dirtying info in
 * which we are interested.
 *
 * It would be a bug for them to not do this.  The code:
 *
 *    mark_inode_dirty(inode)
 *    stuff();
 *    inode->i_size = expr;
 *
 * is in error because a kswapd-driven write_inode() could occur while
 * `stuff()' is running, and the new i_size will be lost.  Plus the inode
 * will no longer be on the superblock's dirty inode list.
 */
int ext4_write_inode(struct inode *inode, int wait)
{
      if (current->flags & PF_MEMALLOC)
            return 0;

      if (ext4_journal_current_handle()) {
            jbd_debug(1, "called recursively, non-PF_MEMALLOC!\n");
            dump_stack();
            return -EIO;
      }

      if (!wait)
            return 0;

      return ext4_force_commit(inode->i_sb);
}

/*
 * ext4_setattr()
 *
 * Called from notify_change.
 *
 * We want to trap VFS attempts to truncate the file as soon as
 * possible.  In particular, we want to make sure that when the VFS
 * shrinks i_size, we put the inode on the orphan list and modify
 * i_disksize immediately, so that during the subsequent flushing of
 * dirty pages and freeing of disk blocks, we can guarantee that any
 * commit will leave the blocks being flushed in an unused state on
 * disk.  (On recovery, the inode will get truncated and the blocks will
 * be freed, so we have a strong guarantee that no future commit will
 * leave these blocks visible to the user.)
 *
 * Called with inode->sem down.
 */
int ext4_setattr(struct dentry *dentry, struct iattr *attr)
{
      struct inode *inode = dentry->d_inode;
      int error, rc = 0;
      const unsigned int ia_valid = attr->ia_valid;

      error = inode_change_ok(inode, attr);
      if (error)
            return error;

      if ((ia_valid & ATTR_UID && attr->ia_uid != inode->i_uid) ||
            (ia_valid & ATTR_GID && attr->ia_gid != inode->i_gid)) {
            handle_t *handle;

            /* (user+group)*(old+new) structure, inode write (sb,
             * inode block, ? - but truncate inode update has it) */
            handle = ext4_journal_start(inode, 2*(EXT4_QUOTA_INIT_BLOCKS(inode->i_sb)+
                              EXT4_QUOTA_DEL_BLOCKS(inode->i_sb))+3);
            if (IS_ERR(handle)) {
                  error = PTR_ERR(handle);
                  goto err_out;
            }
            error = DQUOT_TRANSFER(inode, attr) ? -EDQUOT : 0;
            if (error) {
                  ext4_journal_stop(handle);
                  return error;
            }
            /* Update corresponding info in inode so that everything is in
             * one transaction */
            if (attr->ia_valid & ATTR_UID)
                  inode->i_uid = attr->ia_uid;
            if (attr->ia_valid & ATTR_GID)
                  inode->i_gid = attr->ia_gid;
            error = ext4_mark_inode_dirty(handle, inode);
            ext4_journal_stop(handle);
      }

      if (S_ISREG(inode->i_mode) &&
          attr->ia_valid & ATTR_SIZE && attr->ia_size < inode->i_size) {
            handle_t *handle;

            handle = ext4_journal_start(inode, 3);
            if (IS_ERR(handle)) {
                  error = PTR_ERR(handle);
                  goto err_out;
            }

            error = ext4_orphan_add(handle, inode);
            EXT4_I(inode)->i_disksize = attr->ia_size;
            rc = ext4_mark_inode_dirty(handle, inode);
            if (!error)
                  error = rc;
            ext4_journal_stop(handle);
      }

      rc = inode_setattr(inode, attr);

      /* If inode_setattr's call to ext4_truncate failed to get a
       * transaction handle at all, we need to clean up the in-core
       * orphan list manually. */
      if (inode->i_nlink)
            ext4_orphan_del(NULL, inode);

      if (!rc && (ia_valid & ATTR_MODE))
            rc = ext4_acl_chmod(inode);

err_out:
      ext4_std_error(inode->i_sb, error);
      if (!error)
            error = rc;
      return error;
}


/*
 * How many blocks doth make a writepage()?
 *
 * With N blocks per page, it may be:
 * N data blocks
 * 2 indirect block
 * 2 dindirect
 * 1 tindirect
 * N+5 bitmap blocks (from the above)
 * N+5 group descriptor summary blocks
 * 1 inode block
 * 1 superblock.
 * 2 * EXT4_SINGLEDATA_TRANS_BLOCKS for the quote files
 *
 * 3 * (N + 5) + 2 + 2 * EXT4_SINGLEDATA_TRANS_BLOCKS
 *
 * With ordered or writeback data it's the same, less the N data blocks.
 *
 * If the inode's direct blocks can hold an integral number of pages then a
 * page cannot straddle two indirect blocks, and we can only touch one indirect
 * and dindirect block, and the "5" above becomes "3".
 *
 * This still overestimates under most circumstances.  If we were to pass the
 * start and end offsets in here as well we could do block_to_path() on each
 * block and work out the exact number of indirects which are touched.  Pah.
 */

int ext4_writepage_trans_blocks(struct inode *inode)
{
      int bpp = ext4_journal_blocks_per_page(inode);
      int indirects = (EXT4_NDIR_BLOCKS % bpp) ? 5 : 3;
      int ret;

      if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
            return ext4_ext_writepage_trans_blocks(inode, bpp);

      if (ext4_should_journal_data(inode))
            ret = 3 * (bpp + indirects) + 2;
      else
            ret = 2 * (bpp + indirects) + 2;

#ifdef CONFIG_QUOTA
      /* We know that structure was already allocated during DQUOT_INIT so
       * we will be updating only the data blocks + inodes */
      ret += 2*EXT4_QUOTA_TRANS_BLOCKS(inode->i_sb);
#endif

      return ret;
}

/*
 * The caller must have previously called ext4_reserve_inode_write().
 * Give this, we know that the caller already has write access to iloc->bh.
 */
int ext4_mark_iloc_dirty(handle_t *handle,
            struct inode *inode, struct ext4_iloc *iloc)
{
      int err = 0;

      /* the do_update_inode consumes one bh->b_count */
      get_bh(iloc->bh);

      /* ext4_do_update_inode() does jbd2_journal_dirty_metadata */
      err = ext4_do_update_inode(handle, inode, iloc);
      put_bh(iloc->bh);
      return err;
}

/*
 * On success, We end up with an outstanding reference count against
 * iloc->bh.  This _must_ be cleaned up later.
 */

int
ext4_reserve_inode_write(handle_t *handle, struct inode *inode,
                   struct ext4_iloc *iloc)
{
      int err = 0;
      if (handle) {
            err = ext4_get_inode_loc(inode, iloc);
            if (!err) {
                  BUFFER_TRACE(iloc->bh, "get_write_access");
                  err = ext4_journal_get_write_access(handle, iloc->bh);
                  if (err) {
                        brelse(iloc->bh);
                        iloc->bh = NULL;
                  }
            }
      }
      ext4_std_error(inode->i_sb, err);
      return err;
}

/*
 * Expand an inode by new_extra_isize bytes.
 * Returns 0 on success or negative error number on failure.
 */
int ext4_expand_extra_isize(struct inode *inode, unsigned int new_extra_isize,
                  struct ext4_iloc iloc, handle_t *handle)
{
      struct ext4_inode *raw_inode;
      struct ext4_xattr_ibody_header *header;
      struct ext4_xattr_entry *entry;

      if (EXT4_I(inode)->i_extra_isize >= new_extra_isize)
            return 0;

      raw_inode = ext4_raw_inode(&iloc);

      header = IHDR(inode, raw_inode);
      entry = IFIRST(header);

      /* No extended attributes present */
      if (!(EXT4_I(inode)->i_state & EXT4_STATE_XATTR) ||
            header->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC)) {
            memset((void *)raw_inode + EXT4_GOOD_OLD_INODE_SIZE, 0,
                  new_extra_isize);
            EXT4_I(inode)->i_extra_isize = new_extra_isize;
            return 0;
      }

      /* try to expand with EAs present */
      return ext4_expand_extra_isize_ea(inode, new_extra_isize,
                                raw_inode, handle);
}

/*
 * What we do here is to mark the in-core inode as clean with respect to inode
 * dirtiness (it may still be data-dirty).
 * This means that the in-core inode may be reaped by prune_icache
 * without having to perform any I/O.  This is a very good thing,
 * because *any* task may call prune_icache - even ones which
 * have a transaction open against a different journal.
 *
 * Is this cheating?  Not really.  Sure, we haven't written the
 * inode out, but prune_icache isn't a user-visible syncing function.
 * Whenever the user wants stuff synced (sys_sync, sys_msync, sys_fsync)
 * we start and wait on commits.
 *
 * Is this efficient/effective?  Well, we're being nice to the system
 * by cleaning up our inodes proactively so they can be reaped
 * without I/O.  But we are potentially leaving up to five seconds'
 * worth of inodes floating about which prune_icache wants us to
 * write out.  One way to fix that would be to get prune_icache()
 * to do a write_super() to free up some memory.  It has the desired
 * effect.
 */
int ext4_mark_inode_dirty(handle_t *handle, struct inode *inode)
{
      struct ext4_iloc iloc;
      struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
      static unsigned int mnt_count;
      int err, ret;

      might_sleep();
      err = ext4_reserve_inode_write(handle, inode, &iloc);
      if (EXT4_I(inode)->i_extra_isize < sbi->s_want_extra_isize &&
          !(EXT4_I(inode)->i_state & EXT4_STATE_NO_EXPAND)) {
            /*
             * We need extra buffer credits since we may write into EA block
             * with this same handle. If journal_extend fails, then it will
             * only result in a minor loss of functionality for that inode.
             * If this is felt to be critical, then e2fsck should be run to
             * force a large enough s_min_extra_isize.
             */
            if ((jbd2_journal_extend(handle,
                       EXT4_DATA_TRANS_BLOCKS(inode->i_sb))) == 0) {
                  ret = ext4_expand_extra_isize(inode,
                                          sbi->s_want_extra_isize,
                                          iloc, handle);
                  if (ret) {
                        EXT4_I(inode)->i_state |= EXT4_STATE_NO_EXPAND;
                        if (mnt_count !=
                              le16_to_cpu(sbi->s_es->s_mnt_count)) {
                              ext4_warning(inode->i_sb, __FUNCTION__,
                              "Unable to expand inode %lu. Delete"
                              " some EAs or run e2fsck.",
                              inode->i_ino);
                              mnt_count =
                                le16_to_cpu(sbi->s_es->s_mnt_count);
                        }
                  }
            }
      }
      if (!err)
            err = ext4_mark_iloc_dirty(handle, inode, &iloc);
      return err;
}

/*
 * ext4_dirty_inode() is called from __mark_inode_dirty()
 *
 * We're really interested in the case where a file is being extended.
 * i_size has been changed by generic_commit_write() and we thus need
 * to include the updated inode in the current transaction.
 *
 * Also, DQUOT_ALLOC_SPACE() will always dirty the inode when blocks
 * are allocated to the file.
 *
 * If the inode is marked synchronous, we don't honour that here - doing
 * so would cause a commit on atime updates, which we don't bother doing.
 * We handle synchronous inodes at the highest possible level.
 */
void ext4_dirty_inode(struct inode *inode)
{
      handle_t *current_handle = ext4_journal_current_handle();
      handle_t *handle;

      handle = ext4_journal_start(inode, 2);
      if (IS_ERR(handle))
            goto out;
      if (current_handle &&
            current_handle->h_transaction != handle->h_transaction) {
            /* This task has a transaction open against a different fs */
            printk(KERN_EMERG "%s: transactions do not match!\n",
                   __FUNCTION__);
      } else {
            jbd_debug(5, "marking dirty.  outer handle=%p\n",
                        current_handle);
            ext4_mark_inode_dirty(handle, inode);
      }
      ext4_journal_stop(handle);
out:
      return;
}

#if 0
/*
 * Bind an inode's backing buffer_head into this transaction, to prevent
 * it from being flushed to disk early.  Unlike
 * ext4_reserve_inode_write, this leaves behind no bh reference and
 * returns no iloc structure, so the caller needs to repeat the iloc
 * lookup to mark the inode dirty later.
 */
static int ext4_pin_inode(handle_t *handle, struct inode *inode)
{
      struct ext4_iloc iloc;

      int err = 0;
      if (handle) {
            err = ext4_get_inode_loc(inode, &iloc);
            if (!err) {
                  BUFFER_TRACE(iloc.bh, "get_write_access");
                  err = jbd2_journal_get_write_access(handle, iloc.bh);
                  if (!err)
                        err = ext4_journal_dirty_metadata(handle,
                                                  iloc.bh);
                  brelse(iloc.bh);
            }
      }
      ext4_std_error(inode->i_sb, err);
      return err;
}
#endif

int ext4_change_inode_journal_flag(struct inode *inode, int val)
{
      journal_t *journal;
      handle_t *handle;
      int err;

      /*
       * We have to be very careful here: changing a data block's
       * journaling status dynamically is dangerous.  If we write a
       * data block to the journal, change the status and then delete
       * that block, we risk forgetting to revoke the old log record
       * from the journal and so a subsequent replay can corrupt data.
       * So, first we make sure that the journal is empty and that
       * nobody is changing anything.
       */

      journal = EXT4_JOURNAL(inode);
      if (is_journal_aborted(journal))
            return -EROFS;

      jbd2_journal_lock_updates(journal);
      jbd2_journal_flush(journal);

      /*
       * OK, there are no updates running now, and all cached data is
       * synced to disk.  We are now in a completely consistent state
       * which doesn't have anything in the journal, and we know that
       * no filesystem updates are running, so it is safe to modify
       * the inode's in-core data-journaling state flag now.
       */

      if (val)
            EXT4_I(inode)->i_flags |= EXT4_JOURNAL_DATA_FL;
      else
            EXT4_I(inode)->i_flags &= ~EXT4_JOURNAL_DATA_FL;
      ext4_set_aops(inode);

      jbd2_journal_unlock_updates(journal);

      /* Finally we can mark the inode as dirty. */

      handle = ext4_journal_start(inode, 1);
      if (IS_ERR(handle))
            return PTR_ERR(handle);

      err = ext4_mark_inode_dirty(handle, inode);
      handle->h_sync = 1;
      ext4_journal_stop(handle);
      ext4_std_error(inode->i_sb, err);

      return err;
}

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