Cross-Referenced Linux and Device Driver Code

   /*
    *  linux/fs/ext3/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 ext3_get_block() by Al Viro, 2000
   */
  
  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/time.h>
  #include <linux/ext3_jbd.h>
  #include <linux/jbd.h>
  #include <linux/smp_lock.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 "xattr.h"
  #include "acl.h"
  
  static int ext3_writepage_trans_blocks(struct inode *inode);
  
  /*
   * Test whether an inode is a fast symlink.
   */
  static inline int ext3_inode_is_fast_symlink(struct inode *inode)
  {
          int ea_blocks = EXT3_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 ext3 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 ext3_forget(handle_t *handle, int is_metadata,
                         struct inode *inode, struct buffer_head *bh,
                         int 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) == EXT3_MOUNT_JOURNAL_DATA ||
              (!is_metadata && !ext3_should_journal_data(inode))) {
                  if (bh) {
                          BUFFER_TRACE(bh, "call journal_forget");
                          return ext3_journal_forget(handle, bh);
                  }
                  return 0;
          }
  
          /*
           * data!=journal && (is_metadata || should_journal_data(inode))
           */
          BUFFER_TRACE(bh, "call ext3_journal_revoke");
          err = ext3_journal_revoke(handle, blocknr, bh);
          if (err)
                 ext3_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 progress 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 ext3 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 > EXT3_MAX_TRANS_DATA) 
                 needed = EXT3_MAX_TRANS_DATA;
 
         return EXT3_DATA_TRANS_BLOCKS + 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 = ext3_journal_start(inode, blocks_for_truncate(inode));
         if (!IS_ERR(result))
                 return result;
 
         ext3_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 > EXT3_RESERVE_TRANS_BLOCKS)
                 return 0;
         if (!ext3_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 ext3_journal_test_restart(handle_t *handle, struct inode *inode)
 {
         jbd_debug(2, "restarting handle %p\n", handle);
         return ext3_journal_restart(handle, blocks_for_truncate(inode));
 }
 
 /*
  * Called at the last iput() if i_nlink is zero.
  */
 void ext3_delete_inode (struct inode * inode)
 {
         handle_t *handle;
 
         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. */
                 ext3_orphan_del(NULL, inode);
                 goto no_delete;
         }
 
         if (IS_SYNC(inode))
                 handle->h_sync = 1;
         inode->i_size = 0;
         if (inode->i_blocks)
                 ext3_truncate(inode);
         /*
          * Kill off the orphan record which ext3_truncate created.
          * AKPM: I think this can be inside the above `if'.
          * Note that ext3_orphan_del() has to be able to cope with the
          * deletion of a non-existent orphan - this is because we don't
          * know if ext3_truncate() actually created an orphan record.
          * (Well, we could do this if we need to, but heck - it works)
          */
         ext3_orphan_del(handle, inode);
         EXT3_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 (ext3_mark_inode_dirty(handle, inode))
                 /* If that failed, just do the required in-core inode clear. */
                 clear_inode(inode);
         else
                 ext3_free_inode(handle, inode);
         ext3_journal_stop(handle);
         return;
 no_delete:
         clear_inode(inode);     /* We must guarantee clearing of inode... */
 }
 
 static int ext3_alloc_block (handle_t *handle,
                         struct inode * inode, unsigned long goal, int *err)
 {
         unsigned long result;
 
         result = ext3_new_block(handle, inode, goal, err);
         return result;
 }
 
 
 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 inline int verify_chain(Indirect *from, Indirect *to)
 {
         while (from <= to && from->key == *from->p)
                 from++;
         return (from > to);
 }
 
 /**
  *      ext3_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 ext3 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 ext3_block_to_path(struct inode *inode,
                         long i_block, int offsets[4], int *boundary)
 {
         int ptrs = EXT3_ADDR_PER_BLOCK(inode->i_sb);
         int ptrs_bits = EXT3_ADDR_PER_BLOCK_BITS(inode->i_sb);
         const long direct_blocks = EXT3_NDIR_BLOCKS,
                 indirect_blocks = ptrs,
                 double_blocks = (1 << (ptrs_bits * 2));
         int n = 0;
         int final = 0;
 
         if (i_block < 0) {
                 ext3_warning (inode->i_sb, "ext3_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++] = EXT3_IND_BLOCK;
                 offsets[n++] = i_block;
                 final = ptrs;
         } else if ((i_block -= indirect_blocks) < double_blocks) {
                 offsets[n++] = EXT3_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++] = EXT3_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 {
                 ext3_warning (inode->i_sb, "ext3_block_to_path", "block > big");
         }
         if (boundary)
                 *boundary = (i_block & (ptrs - 1)) == (final - 1);
         return n;
 }
 
 /**
  *      ext3_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 *ext3_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, EXT3_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;
 }
 
 /**
  *      ext3_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 unsigned long ext3_find_near(struct inode *inode, Indirect *ind)
 {
         struct ext3_inode_info *ei = EXT3_I(inode);
         __le32 *start = ind->bh ? (__le32*) ind->bh->b_data : ei->i_data;
         __le32 *p;
         unsigned long bg_start;
         unsigned long 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 refered from inode itself? OK, just put it into
          * the same cylinder group then.
          */
         bg_start = (ei->i_block_group * EXT3_BLOCKS_PER_GROUP(inode->i_sb)) +
                 le32_to_cpu(EXT3_SB(inode->i_sb)->s_es->s_first_data_block);
         colour = (current->pid % 16) *
                         (EXT3_BLOCKS_PER_GROUP(inode->i_sb) / 16);
         return bg_start + colour;
 }
 
 /**
  *      ext3_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. If the branch had been changed
  *      under us we return -EAGAIN.
  */
 
 static int ext3_find_goal(struct inode *inode, long block, Indirect chain[4],
                           Indirect *partial, unsigned long *goal)
 {
         struct ext3_inode_info *ei = EXT3_I(inode);
         /* Writer: ->i_next_alloc* */
         if ((block == ei->i_next_alloc_block + 1)&& ei->i_next_alloc_goal) {
                 ei->i_next_alloc_block++;
                 ei->i_next_alloc_goal++;
         }
         /* Writer: end */
         /* Reader: pointers, ->i_next_alloc* */
         if (verify_chain(chain, partial)) {
                 /*
                  * try the heuristic for sequential allocation,
                  * failing that at least try to get decent locality.
                  */
                 if (block == ei->i_next_alloc_block)
                         *goal = ei->i_next_alloc_goal;
                 if (!*goal)
                         *goal = ext3_find_near(inode, partial);
                 return 0;
         }
         /* Reader: end */
         return -EAGAIN;
 }
 
 /**
  *      ext3_alloc_branch - allocate and set up a chain of blocks.
  *      @inode: owner
  *      @num: depth of the chain (number of blocks to allocate)
  *      @offsets: offsets (in the blocks) to store the pointers to next.
  *      @branch: place to store the chain in.
  *
  *      This function allocates @num 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 ext3_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 ext3_get_block(), excpet 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
  *      ext3_alloc_block() (normally -ENOSPC). Otherwise we set the chain
  *      as described above and return 0.
  */
 
 static int ext3_alloc_branch(handle_t *handle, struct inode *inode,
                              int num,
                              unsigned long goal,
                              int *offsets,
                              Indirect *branch)
 {
         int blocksize = inode->i_sb->s_blocksize;
         int n = 0, keys = 0;
         int err = 0;
         int i;
         int parent = ext3_alloc_block(handle, inode, goal, &err);
 
         branch[0].key = cpu_to_le32(parent);
         if (parent) {
                 for (n = 1; n < num; n++) {
                         struct buffer_head *bh;
                         /* Allocate the next block */
                         int nr = ext3_alloc_block(handle, inode, parent, &err);
                         if (!nr)
                                 break;
                         branch[n].key = cpu_to_le32(nr);
                         keys = n+1;
 
                         /*
                          * 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, parent);
                         branch[n].bh = bh;
                         lock_buffer(bh);
                         BUFFER_TRACE(bh, "call get_create_access");
                         err = ext3_journal_get_create_access(handle, bh);
                         if (err) {
                                 unlock_buffer(bh);
                                 brelse(bh);
                                 break;
                         }
 
                         memset(bh->b_data, 0, blocksize);
                         branch[n].p = (__le32*) bh->b_data + offsets[n];
                         *branch[n].p = branch[n].key;
                         BUFFER_TRACE(bh, "marking uptodate");
                         set_buffer_uptodate(bh);
                         unlock_buffer(bh);
 
                         BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
                         err = ext3_journal_dirty_metadata(handle, bh);
                         if (err)
                                 break;
 
                         parent = nr;
                 }
         }
         if (n == num)
                 return 0;
 
         /* Allocation failed, free what we already allocated */
         for (i = 1; i < keys; i++) {
                 BUFFER_TRACE(branch[i].bh, "call journal_forget");
                 ext3_journal_forget(handle, branch[i].bh);
         }
         for (i = 0; i < keys; i++)
                 ext3_free_blocks(handle, inode, le32_to_cpu(branch[i].key), 1);
         return err;
 }
 
 /**
  *      ext3_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
  *              ext3_alloc_branch)
  *      @where: location of missing link
  *      @num:   number of blocks we are adding
  *
  *      This function verifies that chain (up to the missing link) had not
  *      changed, 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. Otherwise (== chain had been changed)
  *      we free the new blocks (forgetting their buffer_heads, indeed) and
  *      return -EAGAIN.
  */
 
 static int ext3_splice_branch(handle_t *handle, struct inode *inode, long block,
                               Indirect chain[4], Indirect *where, int num)
 {
         int i;
         int err = 0;
         struct ext3_inode_info *ei = EXT3_I(inode);
 
         /*
          * 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 = ext3_journal_get_write_access(handle, where->bh);
                 if (err)
                         goto err_out;
         }
         /* Verify that place we are splicing to is still there and vacant */
 
         /* Writer: pointers, ->i_next_alloc* */
         if (!verify_chain(chain, where-1) || *where->p)
                 /* Writer: end */
                 goto changed;
 
         /* That's it */
 
         *where->p = where->key;
         ei->i_next_alloc_block = block;
         ei->i_next_alloc_goal = le32_to_cpu(where[num-1].key);
         /* Writer: end */
 
         /* We are done with atomic stuff, now do the rest of housekeeping */
 
         inode->i_ctime = CURRENT_TIME_SEC;
         ext3_mark_inode_dirty(handle, inode);
 
         /* had we spliced it onto indirect block? */
         if (where->bh) {
                 /*
                  * akpm: 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->ext3_dirty_inode.
                  */
                 jbd_debug(5, "splicing indirect only\n");
                 BUFFER_TRACE(where->bh, "call ext3_journal_dirty_metadata");
                 err = ext3_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;
 
 changed:
         /*
          * AKPM: if where[i].bh isn't part of the current updating
          * transaction then we explode nastily.  Test this code path.
          */
         jbd_debug(1, "the chain changed: try again\n");
         err = -EAGAIN;
 
 err_out:
         for (i = 1; i < num; i++) {
                 BUFFER_TRACE(where[i].bh, "call journal_forget");
                 ext3_journal_forget(handle, where[i].bh);
         }
         /* For the normal collision cleanup case, we free up the blocks.
          * On genuine filesystem errors we don't even think about doing
          * that. */
         if (err == -EAGAIN)
                 for (i = 0; i < num; i++)
                         ext3_free_blocks(handle, inode, 
                                          le32_to_cpu(where[i].key), 1);
         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.
  *
  * akpm: `handle' can be NULL if create == 0.
  *
  * The BKL may not be held on entry here.  Be sure to take it early.
  */
 
 static int
 ext3_get_block_handle(handle_t *handle, struct inode *inode, sector_t iblock,
                 struct buffer_head *bh_result, int create, int extend_disksize)
 {
         int err = -EIO;
         int offsets[4];
         Indirect chain[4];
         Indirect *partial;
         unsigned long goal;
         int left;
         int boundary = 0;
         int depth = ext3_block_to_path(inode, iblock, offsets, &boundary);
         struct ext3_inode_info *ei = EXT3_I(inode);
 
         J_ASSERT(handle != NULL || create == 0);
 
         if (depth == 0)
                 goto out;
 
 reread:
         partial = ext3_get_branch(inode, depth, offsets, chain, &err);
 
         /* Simplest case - block found, no allocation needed */
         if (!partial) {
                 clear_buffer_new(bh_result);
 got_it:
                 map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
                 if (boundary)
                         set_buffer_boundary(bh_result);
                 /* Clean up and exit */
                 partial = chain+depth-1; /* the whole chain */
                 goto cleanup;
         }
 
         /* Next simple case - plain lookup or failed read of indirect block */
         if (!create || err == -EIO) {
 cleanup:
                 while (partial > chain) {
                         BUFFER_TRACE(partial->bh, "call brelse");
                         brelse(partial->bh);
                         partial--;
                 }
                 BUFFER_TRACE(bh_result, "returned");
 out:
                 return err;
         }
 
         /*
          * Indirect block might be removed by truncate while we were
          * reading it. Handling of that case (forget what we've got and
          * reread) is taken out of the main path.
          */
         if (err == -EAGAIN)
                 goto changed;
 
         goal = 0;
         down(&ei->truncate_sem);
         if (ext3_find_goal(inode, iblock, chain, partial, &goal) < 0) {
                 up(&ei->truncate_sem);
                 goto changed;
         }
 
         left = (chain + depth) - partial;
 
         /*
          * Block out ext3_truncate while we alter the tree
          */
         err = ext3_alloc_branch(handle, inode, left, goal,
                                         offsets+(partial-chain), partial);
 
         /* The ext3_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 = ext3_splice_branch(handle, inode, iblock, chain,
                                          partial, left);
         /* i_disksize growing is protected by truncate_sem
          * don't forget to protect it if you're about to implement
          * concurrent ext3_get_block() -bzzz */
         if (!err && extend_disksize && inode->i_size > ei->i_disksize)
                 ei->i_disksize = inode->i_size;
         up(&ei->truncate_sem);
         if (err == -EAGAIN)
                 goto changed;
         if (err)
                 goto cleanup;
 
         set_buffer_new(bh_result);
         goto got_it;
 
 changed:
         while (partial > chain) {
                 jbd_debug(1, "buffer chain changed, retrying\n");
                 BUFFER_TRACE(partial->bh, "brelsing");
                 brelse(partial->bh);
                 partial--;
         }
         goto reread;
 }
 
 static int ext3_get_block(struct inode *inode, sector_t iblock,
                         struct buffer_head *bh_result, int create)
 {
         handle_t *handle = NULL;
         int ret;
 
         if (create) {
                 handle = ext3_journal_current_handle();
                 J_ASSERT(handle != 0);
         }
         ret = ext3_get_block_handle(handle, inode, iblock,
                                 bh_result, create, 1);
         return ret;
 }
 
 #define DIO_CREDITS (EXT3_RESERVE_TRANS_BLOCKS + 32)
 
 static int
 ext3_direct_io_get_blocks(struct inode *inode, sector_t iblock,
                 unsigned long max_blocks, struct buffer_head *bh_result,
                 int create)
 {
         handle_t *handle = journal_current_handle();
         int ret = 0;
 
         if (!handle)
                 goto get_block;         /* A read */
 
         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.
                  */
                 ext3_journal_stop(handle);
                 handle = ext3_journal_start(inode, DIO_CREDITS);
                 if (IS_ERR(handle))
                         ret = PTR_ERR(handle);
                 goto get_block;
         }
 
         if (handle->h_buffer_credits <= EXT3_RESERVE_TRANS_BLOCKS) {
                 /*
                  * Getting low on buffer credits...
                  */
                 ret = ext3_journal_extend(handle, DIO_CREDITS);
                 if (ret > 0) {
                         /*
                          * Couldn't extend the transaction.  Start a new one.
                          */
                         ret = ext3_journal_restart(handle, DIO_CREDITS);
                 }
         }
 
 get_block:
         if (ret == 0)
                 ret = ext3_get_block_handle(handle, inode, iblock,
                                         bh_result, create, 0);
         bh_result->b_size = (1 << inode->i_blkbits);
         return ret;
 }
 
 /*
  * `handle' can be NULL if create is zero
  */
 struct buffer_head *ext3_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);
         *errp = ext3_get_block_handle(handle, inode, block, &dummy, create, 1);
         if (!*errp && buffer_mapped(&dummy)) {
                 struct buffer_head *bh;
                 bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
                 if (buffer_new(&dummy)) {
                         J_ASSERT(create != 0);
                         J_ASSERT(handle != 0);
 
                         /* 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
                            ext3_get_block instead, so it's not a
                            problem. */
                         lock_buffer(bh);
                         BUFFER_TRACE(bh, "call get_create_access");
                         fatal = ext3_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 ext3_journal_dirty_metadata");
                         err = ext3_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;
         }
         return NULL;
 }
 
 struct buffer_head *ext3_bread(handle_t *handle, struct inode * inode,
                                int block, int create, int *err)
 {
         struct buffer_head * bh;
 
         bh = ext3_getblk(handle, inode, block, create, err);
         if (!bh)
                 return bh;
         if (buffer_uptodate(bh))
                 return bh;
         ll_rw_block(READ, 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 ext3_get_block()
  * and the commit_write().  So doing the journal_start at the start of
  * prepare_write() is the right place.
  *
  * Also, this function can nest inside ext3_writepage() ->
  * block_write_full_page(). In that case, we *know* that ext3_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, ext3 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 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 ext3_journal_get_write_access(handle, bh);
 }
 
 static int ext3_prepare_write(struct file *file, struct page *page,
                               unsigned from, unsigned to)
 {
         struct inode *inode = page->mapping->host;
         int ret, needed_blocks = ext3_writepage_trans_blocks(inode);
         handle_t *handle;
         int retries = 0;
 
 retry:
         handle = ext3_journal_start(inode, needed_blocks);
         if (IS_ERR(handle)) {
                 ret = PTR_ERR(handle);
                 goto out;
         }
         ret = block_prepare_write(page, from, to, ext3_get_block);
         if (ret)
                 goto prepare_write_failed;
 
         if (ext3_should_journal_data(inode)) {
                 ret = walk_page_buffers(handle, page_buffers(page),
                                 from, to, NULL, do_journal_get_write_access);
         }
 prepare_write_failed:
         if (ret)
                 ext3_journal_stop(handle);
         if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
                 goto retry;
 out:
         return ret;
 }
 
 int
 ext3_journal_dirty_data(handle_t *handle, struct buffer_head *bh)
 {
         int err = journal_dirty_data(handle, bh);
         if (err)
                 ext3_journal_abort_handle(__FUNCTION__, __FUNCTION__,
                                                 bh, handle,err);
         return err;
 }
 
 /* For commit_write() in data=journal mode */
 static int commit_write_fn(handle_t *handle, struct buffer_head *bh)
 {
         if (!buffer_mapped(bh) || buffer_freed(bh))
                 return 0;
         set_buffer_uptodate(bh);
         return ext3_journal_dirty_metadata(handle, bh);
 }
 
 /*
  * 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().
  *
  * ext3 never places buffers on inode->i_mapping->private_list.  metadata
  * buffers are managed internally.
  */
 
 static int ext3_ordered_commit_write(struct file *file, struct page *page,
                              unsigned from, unsigned to)
 {
         handle_t *handle = ext3_journal_current_handle();
         struct inode *inode = page->mapping->host;
         int ret = 0, ret2;
 
         ret = walk_page_buffers(handle, page_buffers(page),
                 from, to, NULL, ext3_journal_dirty_data);
 
         if (ret == 0) {
                 /*
                  * generic_commit_write() 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 = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
                 if (new_i_size > EXT3_I(inode)->i_disksize)
                         EXT3_I(inode)->i_disksize = new_i_size;
                 ret = generic_commit_write(file, page, from, to);
         }
         ret2 = ext3_journal_stop(handle);
         if (!ret)
                 ret = ret2;
         return ret;
 }
 
 static int ext3_writeback_commit_write(struct file *file, struct page *page,
                              unsigned from, unsigned to)
 {
         handle_t *handle = ext3_journal_current_handle();
         struct inode *inode = page->mapping->host;
         int ret = 0, ret2;
         loff_t new_i_size;
 
         new_i_size = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
         if (new_i_size > EXT3_I(inode)->i_disksize)
                 EXT3_I(inode)->i_disksize = new_i_size;
         ret = generic_commit_write(file, page, from, to);
         ret2 = ext3_journal_stop(handle);
         if (!ret)
                 ret = ret2;
         return ret;
 }
 
 static int ext3_journalled_commit_write(struct file *file,
                         struct page *page, unsigned from, unsigned to)
 {
         handle_t *handle = ext3_journal_current_handle();
         struct inode *inode = page->mapping->host;
         int ret = 0, ret2;
         int partial = 0;
         loff_t pos;
 
         /*
          * Here we duplicate the generic_commit_write() functionality
          */
         pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
 
         ret = walk_page_buffers(handle, page_buffers(page), from,
                                 to, &partial, commit_write_fn);
         if (!partial)
                 SetPageUptodate(page);
         if (pos > inode->i_size)
                 i_size_write(inode, pos);
         EXT3_I(inode)->i_state |= EXT3_STATE_JDATA;
         if (inode->i_size > EXT3_I(inode)->i_disksize) {
                 EXT3_I(inode)->i_disksize = inode->i_size;
                 ret2 = ext3_mark_inode_dirty(handle, inode);
                 if (!ret) 
                         ret = ret2;
         }
         ret2 = ext3_journal_stop(handle);
         if (!ret)
                 ret = ret2;
         return ret;
 }
 
 /* 
  * 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 ext3 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 ext3_bmap(struct address_space *mapping, sector_t block)
 {
         struct inode *inode = mapping->host;
         journal_t *journal;
         int err;
 
         if (EXT3_I(inode)->i_state & EXT3_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. EXT3_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.
                  */
 
                 EXT3_I(inode)->i_state &= ~EXT3_STATE_JDATA;
                 journal = EXT3_JOURNAL(inode);
                 journal_lock_updates(journal);
                 err = journal_flush(journal);
                 journal_unlock_updates(journal);
 
                 if (err)
                         return 0;
         }
 
         return generic_block_bmap(mapping,block,ext3_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 journal_dirty_data_fn(handle_t *handle, struct buffer_head *bh)
 {
         if (buffer_mapped(bh))
                 return ext3_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 -> ext3_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:
  *
  *      ext3_writepage() -> kmalloc() -> __alloc_pages() -> page_launder() ->
  *              ext3_writepage()
  *
  * Similar for:
  *
  *      ext3_file_write() -> generic_file_write() -> __alloc_pages() -> ...
  *
  * Same applies to ext3_get_block().  We will deadlock on various things like
  * lock_journal and i_truncate_sem.
  *
  * 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 ext3_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 (ext3_journal_current_handle())
                 goto out_fail;
 
         handle = ext3_journal_start(inode, ext3_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, ext3_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, journal_dirty_data_fn);
                 if (!ret)
                         ret = err;
         }
         walk_page_buffers(handle, page_bufs, 0,
                         PAGE_CACHE_SIZE, NULL, bput_one);
         err = ext3_journal_stop(handle);
         if (!ret)
                 ret = err;
         return ret;
 
 out_fail:
         redirty_page_for_writepage(wbc, page);
         unlock_page(page);
         return ret;
 }
 
 static int ext3_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 (ext3_journal_current_handle())
                 goto out_fail;
 
         handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode));
         if (IS_ERR(handle)) {
                 ret = PTR_ERR(handle);
                 goto out_fail;
         }
 
         ret = block_write_full_page(page, ext3_get_block, wbc);
         err = ext3_journal_stop(handle);
         if (!ret)
                 ret = err;
         return ret;
 
 out_fail:
         redirty_page_for_writepage(wbc, page);
         unlock_page(page);
         return ret;
 }
 
 static int ext3_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 (ext3_journal_current_handle())
                 goto no_write;
 
         handle = ext3_journal_start(inode, ext3_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,
                                         ext3_get_block);
                 if (ret != 0)
                         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, commit_write_fn);
                 if (ret == 0)
                         ret = err;
                 EXT3_I(inode)->i_state |= EXT3_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, ext3_get_block, wbc);
         }
         err = ext3_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 ext3_readpage(struct file *file, struct page *page)
 {
         return mpage_readpage(page, ext3_get_block);
 }
 
 static int
 ext3_readpages(struct file *file, struct address_space *mapping,
                 struct list_head *pages, unsigned nr_pages)
 {
         return mpage_readpages(mapping, pages, nr_pages, ext3_get_block);
 }
 
 static int ext3_invalidatepage(struct page *page, unsigned long offset)
 {
         journal_t *journal = EXT3_JOURNAL(page->mapping->host);
 
         /*
          * If it's a full truncate we just forget about the pending dirtying
          */
         if (offset == 0)
                 ClearPageChecked(page);
 
         return journal_invalidatepage(journal, page, offset);
 }
 
 static int ext3_releasepage(struct page *page, int wait)
 {
         journal_t *journal = EXT3_JOURNAL(page->mapping->host);
 
         WARN_ON(PageChecked(page));
         return 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 ext3_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 ext3_inode_info *ei = EXT3_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 = ext3_journal_start(inode, DIO_CREDITS);
                 if (IS_ERR(handle)) {
                         ret = PTR_ERR(handle);
                         goto out;
                 }
                 if (final_size > inode->i_size) {
                         ret = ext3_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,
                                  ext3_direct_io_get_blocks, NULL);
 
         /*
          * Reacquire the handle: ext3_direct_io_get_block() can restart the
          * transaction
          */
         handle = journal_current_handle();
 
 out_stop:
         if (handle) {
                 int err;
 
                 if (orphan && inode->i_nlink)
                         ext3_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
                                  * ext3_mark_inode_dirty() to userspace.  So
                                  * ignore it.
                                  */
                                 ext3_mark_inode_dirty(handle, inode);
                         }
                 }
                 err = ext3_journal_stop(handle);
                 if (ret == 0)
                         ret = err;
         }
 out:
         return ret;
 }
 
 /*
  * Pages can be marked dirty completely asynchronously from ext3'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 ext3_journalled_set_page_dirty(struct page *page)
 {
         SetPageChecked(page);
         return __set_page_dirty_nobuffers(page);
 }
 
 static struct address_space_operations ext3_ordered_aops = {
         .readpage       = ext3_readpage,
         .readpages      = ext3_readpages,
         .writepage      = ext3_ordered_writepage,
         .sync_page      = block_sync_page,
         .prepare_write  = ext3_prepare_write,
         .commit_write   = ext3_ordered_commit_write,
         .bmap           = ext3_bmap,
         .invalidatepage = ext3_invalidatepage,
         .releasepage    = ext3_releasepage,
         .direct_IO      = ext3_direct_IO,
 };
 
 static struct address_space_operations ext3_writeback_aops = {
         .readpage       = ext3_readpage,
         .readpages      = ext3_readpages,
         .writepage      = ext3_writeback_writepage,
         .sync_page      = block_sync_page,
         .prepare_write  = ext3_prepare_write,
         .commit_write   = ext3_writeback_commit_write,
         .bmap           = ext3_bmap,
         .invalidatepage = ext3_invalidatepage,
         .releasepage    = ext3_releasepage,
         .direct_IO      = ext3_direct_IO,
 };
 
 static struct address_space_operations ext3_journalled_aops = {
         .readpage       = ext3_readpage,
         .readpages      = ext3_readpages,
         .writepage      = ext3_journalled_writepage,
         .sync_page      = block_sync_page,
         .prepare_write  = ext3_prepare_write,
         .commit_write   = ext3_journalled_commit_write,
         .set_page_dirty = ext3_journalled_set_page_dirty,
         .bmap           = ext3_bmap,
         .invalidatepage = ext3_invalidatepage,
         .releasepage    = ext3_releasepage,
 };
 
 void ext3_set_aops(struct inode *inode)
 {
         if (ext3_should_order_data(inode))
                 inode->i_mapping->a_ops = &ext3_ordered_aops;
         else if (ext3_should_writeback_data(inode))
                 inode->i_mapping->a_ops = &ext3_writeback_aops;
         else
                 inode->i_mapping->a_ops = &ext3_journalled_aops;
 }
 
 /*
  * ext3_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.
  */
 static int ext3_block_truncate_page(handle_t *handle, struct page *page,
                 struct address_space *mapping, loff_t from)
 {
         unsigned long 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;
         void *kaddr;
 
         blocksize = inode->i_sb->s_blocksize;
         length = blocksize - (offset & (blocksize - 1));
         iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
 
         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");
                 ext3_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 (ext3_should_journal_data(inode)) {
                 BUFFER_TRACE(bh, "get write access");
                 err = ext3_journal_get_write_access(handle, bh);
                 if (err)
                         goto unlock;
         }
 
         kaddr = kmap_atomic(page, KM_USER0);
         memset(kaddr + offset, 0, length);
         flush_dcache_page(page);
         kunmap_atomic(kaddr, KM_USER0);
 
         BUFFER_TRACE(bh, "zeroed end of block");
 
         err = 0;
         if (ext3_should_journal_data(inode)) {
                 err = ext3_journal_dirty_metadata(handle, bh);
         } else {
                 if (ext3_should_order_data(inode))
                         err = ext3_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;
 }
 
 /**
  *      ext3_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 ext3_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 ext3_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 ext3_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 *ext3_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 = ext3_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 ext3.  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
 ext3_clear_blocks(handle_t *handle, struct inode *inode, struct buffer_head *bh,
                 unsigned long 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 ext3_journal_dirty_metadata");
                         ext3_journal_dirty_metadata(handle, bh);
                 }
                 ext3_mark_inode_dirty(handle, inode);
                 ext3_journal_test_restart(handle, inode);
                 if (bh) {
                         BUFFER_TRACE(bh, "retaking write access");
                         ext3_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 journal_revoke() will run journal_forget()
          * on them.  We've already detached each block from the file, so
          * bforget() in journal_forget() should be safe.
          *
          * AKPM: turn on bforget in 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);
                         ext3_forget(handle, 0, inode, bh, nr);
                 }
         }
 
         ext3_free_blocks(handle, inode, block_to_free, count);
 }
 
 /**
  * ext3_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 ext3_free_data(handle_t *handle, struct inode *inode,
                            struct buffer_head *this_bh,
                            __le32 *first, __le32 *last)
 {
         unsigned long 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 */
         unsigned long 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 = ext3_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 {
                                 ext3_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)
                 ext3_clear_blocks(handle, inode, this_bh, block_to_free,
                                   count, block_to_free_p, p);
 
         if (this_bh) {
                 BUFFER_TRACE(this_bh, "call ext3_journal_dirty_metadata");
                 ext3_journal_dirty_metadata(handle, this_bh);
         }
 }
 
 /**
  *      ext3_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 ext3_free_branches(handle_t *handle, struct inode *inode,
                                struct buffer_head *parent_bh,
                                __le32 *first, __le32 *last, int depth)
 {
         unsigned long nr;
         __le32 *p;
 
         if (is_handle_aborted(handle))
                 return;
 
         if (depth--) {
                 struct buffer_head *bh;
                 int addr_per_block = EXT3_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) {
                                 ext3_error(inode->i_sb, "ext3_free_branches",
                                            "Read failure, inode=%ld, block=%ld",
                                            inode->i_ino, nr);
                                 continue;
                         }
 
                         /* This zaps the entire block.  Bottom up. */
                         BUFFER_TRACE(bh, "free child branches");
                         ext3_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
                          * journal_revoke().
                          *
                          * That's easy if it's exclusively part of this
                          * transaction.  But if it's part of the committing
                          * transaction then journal_forget() will simply
                          * brelse() it.  That means that if the underlying
                          * block is reallocated in ext3_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.
                          */
                         ext3_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)) {
                                 ext3_mark_inode_dirty(handle, inode);
                                 ext3_journal_test_restart(handle, inode);
                         }
 
                         ext3_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 (!ext3_journal_get_write_access(handle,
                                                                    parent_bh)){
                                         *p = 0;
                                         BUFFER_TRACE(parent_bh,
                                         "call ext3_journal_dirty_metadata");
                                         ext3_journal_dirty_metadata(handle, 
                                                                     parent_bh);
                                 }
                         }
                 }
         } else {
                 /* We have reached the bottom of the tree. */
                 BUFFER_TRACE(parent_bh, "free data blocks");
                 ext3_free_data(handle, inode, parent_bh, first, last);
         }
 }
 
 /*
  * ext3_truncate()
  *
  * We block out ext3_get_block() block instantiations across the entire
  * transaction, and VFS/VM ensures that ext3_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, ext3_orphan_cleanup() will see
  * that this inode's truncate did not complete and it will again call
  * ext3_truncate() to have another go.  So there will be instantiated blocks
  * to the right of the truncation point in a crashed ext3 filesystem.  But
  * that's fine - as long as they are linked from the inode, the post-crash
  * ext3_truncate() run will find them and release them.
  */
 
 void ext3_truncate(struct inode * inode)
 {
         handle_t *handle;
         struct ext3_inode_info *ei = EXT3_I(inode);
         __le32 *i_data = ei->i_data;
         int addr_per_block = EXT3_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 (ext3_inode_is_fast_symlink(inode))
                 return;
         if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
                 return;
 
         ext3_discard_reservation(inode);
 
         /*
          * We have to lock the EOF page here, because lock_page() nests
          * outside 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;
         }
 
         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)
                                         >> EXT3_BLOCK_SIZE_BITS(inode->i_sb);
 
         if (page)
                 ext3_block_truncate_page(handle, page, mapping, inode->i_size);
 
         n = ext3_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 (ext3_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
          * ext3 *really* writes onto the disk inode.
          */
         ei->i_disksize = inode->i_size;
 
         /*
          * From here we block out all ext3_get_block() callers who want to
          * modify the block allocation tree.
          */
         down(&ei->truncate_sem);
 
         if (n == 1) {           /* direct blocks */
                 ext3_free_data(handle, inode, NULL, i_data+offsets[0],
                                i_data + EXT3_NDIR_BLOCKS);
                 goto do_indirects;
         }
 
         partial = ext3_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 */
                         ext3_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");
                         ext3_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) {
                 ext3_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[EXT3_IND_BLOCK];
                         if (nr) {
                                 ext3_free_branches(handle, inode, NULL,
                                                    &nr, &nr+1, 1);
                                 i_data[EXT3_IND_BLOCK] = 0;
                         }
                 case EXT3_IND_BLOCK:
                         nr = i_data[EXT3_DIND_BLOCK];
                         if (nr) {
                                 ext3_free_branches(handle, inode, NULL,
                                                    &nr, &nr+1, 2);
                                 i_data[EXT3_DIND_BLOCK] = 0;
                         }
                 case EXT3_DIND_BLOCK:
                         nr = i_data[EXT3_TIND_BLOCK];
                         if (nr) {
                                 ext3_free_branches(handle, inode, NULL,
                                                    &nr, &nr+1, 3);
                                 i_data[EXT3_TIND_BLOCK] = 0;
                         }
                 case EXT3_TIND_BLOCK:
                         ;
         }
         up(&ei->truncate_sem);
         inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
         ext3_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
          * ext3_delete_inode(), and we allow that function to clean up the
          * orphan info for us.
          */
         if (inode->i_nlink)
                 ext3_orphan_del(handle, inode);
 
         ext3_journal_stop(handle);
 }
 
 static unsigned long ext3_get_inode_block(struct super_block *sb,
                 unsigned long ino, struct ext3_iloc *iloc)
 {
         unsigned long desc, group_desc, block_group;
         unsigned long offset, block;
         struct buffer_head *bh;
         struct ext3_group_desc * gdp;
 
 
         if ((ino != EXT3_ROOT_INO &&
                 ino != EXT3_JOURNAL_INO &&
                 ino != EXT3_RESIZE_INO &&
                 ino < EXT3_FIRST_INO(sb)) ||
                 ino > le32_to_cpu(
                         EXT3_SB(sb)->s_es->s_inodes_count)) {
                 ext3_error (sb, "ext3_get_inode_block",
                             "bad inode number: %lu", ino);
                 return 0;
         }
         block_group = (ino - 1) / EXT3_INODES_PER_GROUP(sb);
         if (block_group >= EXT3_SB(sb)->s_groups_count) {
                 ext3_error (sb, "ext3_get_inode_block",
                             "group >= groups count");
                 return 0;
         }
         smp_rmb();
         group_desc = block_group >> EXT3_DESC_PER_BLOCK_BITS(sb);
         desc = block_group & (EXT3_DESC_PER_BLOCK(sb) - 1);
         bh = EXT3_SB(sb)->s_group_desc[group_desc];
         if (!bh) {
                 ext3_error (sb, "ext3_get_inode_block",
                             "Descriptor not loaded");
                 return 0;
         }
 
         gdp = (struct ext3_group_desc *) bh->b_data;
         /*
          * Figure out the offset within the block group inode table
          */
         offset = ((ino - 1) % EXT3_INODES_PER_GROUP(sb)) *
                 EXT3_INODE_SIZE(sb);
         block = le32_to_cpu(gdp[desc].bg_inode_table) +
                 (offset >> EXT3_BLOCK_SIZE_BITS(sb));
 
         iloc->block_group = block_group;
         iloc->offset = offset & (EXT3_BLOCK_SIZE(sb) - 1);
         return block;
 }
 
 /*
  * ext3_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 __ext3_get_inode_loc(struct inode *inode,
                                 struct ext3_iloc *iloc, int in_mem)
 {
         unsigned long block;
         struct buffer_head *bh;
 
         block = ext3_get_inode_block(inode->i_sb, inode->i_ino, iloc);
         if (!block)
                 return -EIO;
 
         bh = sb_getblk(inode->i_sb, block);
         if (!bh) {
                 ext3_error (inode->i_sb, "ext3_get_inode_loc",
                                 "unable to read inode block - "
                                 "inode=%lu, block=%lu", 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 ext3_group_desc *desc;
                         int inodes_per_buffer;
                         int inode_offset, i;
                         int block_group;
                         int start;
 
                         block_group = (inode->i_ino - 1) /
                                         EXT3_INODES_PER_GROUP(inode->i_sb);
                         inodes_per_buffer = bh->b_size /
                                 EXT3_INODE_SIZE(inode->i_sb);
                         inode_offset = ((inode->i_ino - 1) %
                                         EXT3_INODES_PER_GROUP(inode->i_sb));
                         start = inode_offset & ~(inodes_per_buffer - 1);
 
                         /* Is the inode bitmap in cache? */
                         desc = ext3_get_group_desc(inode->i_sb,
                                                 block_group, NULL);
                         if (!desc)
                                 goto make_io;
 
                         bitmap_bh = sb_getblk(inode->i_sb,
                                         le32_to_cpu(desc->bg_inode_bitmap));
                         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 (ext3_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, bh);
                 wait_on_buffer(bh);
                 if (!buffer_uptodate(bh)) {
                         ext3_error(inode->i_sb, "ext3_get_inode_loc",
                                         "unable to read inode block - "
                                         "inode=%lu, block=%lu",
                                         inode->i_ino, block);
                         brelse(bh);
                         return -EIO;
                 }
         }
 has_buffer:
         iloc->bh = bh;
         return 0;
 }
 
 int ext3_get_inode_loc(struct inode *inode, struct ext3_iloc *iloc)
 {
         /* We have all inode data except xattrs in memory here. */
         return __ext3_get_inode_loc(inode, iloc,
                 !(EXT3_I(inode)->i_state & EXT3_STATE_XATTR));
 }
 
 void ext3_set_inode_flags(struct inode *inode)
 {
         unsigned int flags = EXT3_I(inode)->i_flags;
 
         inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
         if (flags & EXT3_SYNC_FL)
                 inode->i_flags |= S_SYNC;
         if (flags & EXT3_APPEND_FL)
                 inode->i_flags |= S_APPEND;
         if (flags & EXT3_IMMUTABLE_FL)
                 inode->i_flags |= S_IMMUTABLE;
         if (flags & EXT3_NOATIME_FL)
                 inode->i_flags |= S_NOATIME;
         if (flags & EXT3_DIRSYNC_FL)
                 inode->i_flags |= S_DIRSYNC;
 }
 
 void ext3_read_inode(struct inode * inode)
 {
         struct ext3_iloc iloc;
         struct ext3_inode *raw_inode;
         struct ext3_inode_info *ei = EXT3_I(inode);
         struct buffer_head *bh;
         int block;
 
 #ifdef CONFIG_EXT3_FS_POSIX_ACL
         ei->i_acl = EXT3_ACL_NOT_CACHED;
         ei->i_default_acl = EXT3_ACL_NOT_CACHED;
 #endif
         ei->i_rsv_window.rsv_end = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
 
         if (__ext3_get_inode_loc(inode, &iloc, 0))
                 goto bad_inode;
         bh = iloc.bh;
         raw_inode = ext3_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);
         inode->i_atime.tv_sec = le32_to_cpu(raw_inode->i_atime);
         inode->i_ctime.tv_sec = le32_to_cpu(raw_inode->i_ctime);
         inode->i_mtime.tv_sec = le32_to_cpu(raw_inode->i_mtime);
         inode->i_atime.tv_nsec = inode->i_ctime.tv_nsec = inode->i_mtime.tv_nsec = 0;
 
         ei->i_state = 0;
         ei->i_next_alloc_block = 0;
         ei->i_next_alloc_goal = 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 ||
                     !(EXT3_SB(inode->i_sb)->s_mount_state & EXT3_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_blksize = PAGE_SIZE;   /* This is the optimal IO size
                                          * (for stat), not the fs block
                                          * size */  
         inode->i_blocks = le32_to_cpu(raw_inode->i_blocks);
         ei->i_flags = le32_to_cpu(raw_inode->i_flags);
 #ifdef EXT3_FRAGMENTS
         ei->i_faddr = le32_to_cpu(raw_inode->i_faddr);
         ei->i_frag_no = raw_inode->i_frag;
         ei->i_frag_size = raw_inode->i_fsize;
 #endif
         ei->i_file_acl = le32_to_cpu(raw_inode->i_file_acl);
         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;
         ei->i_rsv_window.rsv_start = 0;
         ei->i_rsv_window.rsv_end= 0;
         atomic_set(&ei->i_rsv_window.rsv_goal_size, EXT3_DEFAULT_RESERVE_BLOCKS);
         seqlock_init(&ei->i_rsv_window.rsv_seqlock);
         /*
          * 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 < EXT3_N_BLOCKS; block++)
                 ei->i_data[block] = raw_inode->i_block[block];
         INIT_LIST_HEAD(&ei->i_orphan);
 
         if (inode->i_ino >= EXT3_FIRST_INO(inode->i_sb) + 1 &&
             EXT3_INODE_SIZE(inode->i_sb) > EXT3_GOOD_OLD_INODE_SIZE) {
                 /*
                  * When mke2fs creates big inodes it does not zero out
                  * the unused bytes above EXT3_GOOD_OLD_INODE_SIZE,
                  * so ignore those first few inodes.
                  */
                 ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
                 if (EXT3_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >
                     EXT3_INODE_SIZE(inode->i_sb))
                         goto bad_inode;
                 if (ei->i_extra_isize == 0) {
                         /* The extra space is currently unused. Use it. */
                         ei->i_extra_isize = sizeof(struct ext3_inode) -
                                             EXT3_GOOD_OLD_INODE_SIZE;
                 } else {
                         __le32 *magic = (void *)raw_inode +
                                         EXT3_GOOD_OLD_INODE_SIZE +
                                         ei->i_extra_isize;
                         if (*magic == cpu_to_le32(EXT3_XATTR_MAGIC))
                                  ei->i_state |= EXT3_STATE_XATTR;
                 }
         } else
                 ei->i_extra_isize = 0;
 
         if (S_ISREG(inode->i_mode)) {
                 inode->i_op = &ext3_file_inode_operations;
                 inode->i_fop = &ext3_file_operations;
                 ext3_set_aops(inode);
         } else if (S_ISDIR(inode->i_mode)) {
                 inode->i_op = &ext3_dir_inode_operations;
                 inode->i_fop = &ext3_dir_operations;
         } else if (S_ISLNK(inode->i_mode)) {
                 if (ext3_inode_is_fast_symlink(inode))
                         inode->i_op = &ext3_fast_symlink_inode_operations;
                 else {
                         inode->i_op = &ext3_symlink_inode_operations;
                         ext3_set_aops(inode);
                 }
         } else {
                 inode->i_op = &ext3_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);
         ext3_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 ext3_do_update_inode(handle_t *handle, 
                                 struct inode *inode, 
                                 struct ext3_iloc *iloc)
 {
         struct ext3_inode *raw_inode = ext3_raw_inode(iloc);
         struct ext3_inode_info *ei = EXT3_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 & EXT3_STATE_NEW)
                 memset(raw_inode, 0, EXT3_SB(inode->i_sb)->s_inode_size);
 
         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);
         raw_inode->i_atime = cpu_to_le32(inode->i_atime.tv_sec);
         raw_inode->i_ctime = cpu_to_le32(inode->i_ctime.tv_sec);
         raw_inode->i_mtime = cpu_to_le32(inode->i_mtime.tv_sec);
         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);
 #ifdef EXT3_FRAGMENTS
         raw_inode->i_faddr = cpu_to_le32(ei->i_faddr);
         raw_inode->i_frag = ei->i_frag_no;
         raw_inode->i_fsize = ei->i_frag_size;
 #endif
         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 (!EXT3_HAS_RO_COMPAT_FEATURE(sb,
                                         EXT3_FEATURE_RO_COMPAT_LARGE_FILE) ||
                             EXT3_SB(sb)->s_es->s_rev_level ==
                                         cpu_to_le32(EXT3_GOOD_OLD_REV)) {
                                /* If this is the first large file
                                 * created, add a flag to the superblock.
                                 */
                                 err = ext3_journal_get_write_access(handle,
                                                 EXT3_SB(sb)->s_sbh);
                                 if (err)
                                         goto out_brelse;
                                 ext3_update_dynamic_rev(sb);
                                 EXT3_SET_RO_COMPAT_FEATURE(sb,
                                         EXT3_FEATURE_RO_COMPAT_LARGE_FILE);
                                 sb->s_dirt = 1;
                                 handle->h_sync = 1;
                                 err = ext3_journal_dirty_metadata(handle,
                                                 EXT3_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 < EXT3_N_BLOCKS; block++)
                 raw_inode->i_block[block] = ei->i_data[block];
 
         if (EXT3_INODE_SIZE(inode->i_sb) > EXT3_GOOD_OLD_INODE_SIZE)
                 raw_inode->i_extra_isize = cpu_to_le16(ei->i_extra_isize);
 
         BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
         rc = ext3_journal_dirty_metadata(handle, bh);
         if (!err)
                 err = rc;
         ei->i_state &= ~EXT3_STATE_NEW;
 
 out_brelse:
         brelse (bh);
         ext3_std_error(inode->i_sb, err);
         return err;
 }
 
 /*
  * ext3_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
  * ext3_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 ext3_write_inode(struct inode *inode, int wait)
 {
         if (current->flags & PF_MEMALLOC)
                 return 0;
 
         if (ext3_journal_current_handle()) {
                 jbd_debug(0, "called recursively, non-PF_MEMALLOC!\n");
                 dump_stack();
                 return -EIO;
         }
 
         if (!wait)
                 return 0;
 
         return ext3_force_commit(inode->i_sb);
 }
 
 /*
  * ext3_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 ext3_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 = ext3_journal_start(inode, 4*EXT3_QUOTA_INIT_BLOCKS+3);
                 if (IS_ERR(handle)) {
                         error = PTR_ERR(handle);
                         goto err_out;
                 }
                 error = DQUOT_TRANSFER(inode, attr) ? -EDQUOT : 0;
                 if (error) {
                         ext3_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 = ext3_mark_inode_dirty(handle, inode);
                 ext3_journal_stop(handle);
         }
 
         if (S_ISREG(inode->i_mode) &&
             attr->ia_valid & ATTR_SIZE && attr->ia_size < inode->i_size) {
                 handle_t *handle;
 
                 handle = ext3_journal_start(inode, 3);
                 if (IS_ERR(handle)) {
                         error = PTR_ERR(handle);
                         goto err_out;
                 }
 
                 error = ext3_orphan_add(handle, inode);
                 EXT3_I(inode)->i_disksize = attr->ia_size;
                 rc = ext3_mark_inode_dirty(handle, inode);
                 if (!error)
                         error = rc;
                 ext3_journal_stop(handle);
         }
 
         rc = inode_setattr(inode, attr);
 
         /* If inode_setattr's call to ext3_truncate failed to get a
          * transaction handle at all, we need to clean up the in-core
          * orphan list manually. */
         if (inode->i_nlink)
                 ext3_orphan_del(NULL, inode);
 
         if (!rc && (ia_valid & ATTR_MODE))
                 rc = ext3_acl_chmod(inode);
 
 err_out:
         ext3_std_error(inode->i_sb, error);
         if (!error)
                 error = rc;
         return error;
 }
 
 
 /*
  * akpm: 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 * EXT3_SINGLEDATA_TRANS_BLOCKS for the quote files
  *
  * 3 * (N + 5) + 2 + 2 * EXT3_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.
  */
 
 static int ext3_writepage_trans_blocks(struct inode *inode)
 {
         int bpp = ext3_journal_blocks_per_page(inode);
         int indirects = (EXT3_NDIR_BLOCKS % bpp) ? 5 : 3;
         int ret;
 
         if (ext3_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*EXT3_QUOTA_TRANS_BLOCKS;
 #endif
 
         return ret;
 }
 
 /*
  * The caller must have previously called ext3_reserve_inode_write().
  * Give this, we know that the caller already has write access to iloc->bh.
  */
 int ext3_mark_iloc_dirty(handle_t *handle,
                 struct inode *inode, struct ext3_iloc *iloc)
 {
         int err = 0;
 
         /* the do_update_inode consumes one bh->b_count */
         get_bh(iloc->bh);
 
         /* ext3_do_update_inode() does journal_dirty_metadata */
         err = ext3_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
 ext3_reserve_inode_write(handle_t *handle, struct inode *inode, 
                          struct ext3_iloc *iloc)
 {
         int err = 0;
         if (handle) {
                 err = ext3_get_inode_loc(inode, iloc);
                 if (!err) {
                         BUFFER_TRACE(iloc->bh, "get_write_access");
                         err = ext3_journal_get_write_access(handle, iloc->bh);
                         if (err) {
                                 brelse(iloc->bh);
                                 iloc->bh = NULL;
                         }
                 }
         }
         ext3_std_error(inode->i_sb, err);
         return err;
 }
 
 /*
  * akpm: 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 ext3_mark_inode_dirty(handle_t *handle, struct inode *inode)
 {
         struct ext3_iloc iloc;
         int err;
 
         might_sleep();
         err = ext3_reserve_inode_write(handle, inode, &iloc);
         if (!err)
                 err = ext3_mark_iloc_dirty(handle, inode, &iloc);
         return err;
 }
 
 /*
  * akpm: ext3_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 ext3_dirty_inode(struct inode *inode)
 {
         handle_t *current_handle = ext3_journal_current_handle();
         handle_t *handle;
 
         handle = ext3_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);
                 ext3_mark_inode_dirty(handle, inode);
         }
         ext3_journal_stop(handle);
 out:
         return;
 }
 
 #ifdef AKPM
 /* 
  * Bind an inode's backing buffer_head into this transaction, to prevent
  * it from being flushed to disk early.  Unlike
  * ext3_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 inline int
 ext3_pin_inode(handle_t *handle, struct inode *inode)
 {
         struct ext3_iloc iloc;
 
         int err = 0;
         if (handle) {
                 err = ext3_get_inode_loc(inode, &iloc);
                 if (!err) {
                         BUFFER_TRACE(iloc.bh, "get_write_access");
                         err = journal_get_write_access(handle, iloc.bh);
                         if (!err)
                                 err = ext3_journal_dirty_metadata(handle, 
                                                                   iloc.bh);
                         brelse(iloc.bh);
                 }
         }
         ext3_std_error(inode->i_sb, err);
         return err;
 }
 #endif
 
 int ext3_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 = EXT3_JOURNAL(inode);
         if (is_journal_aborted(journal) || IS_RDONLY(inode))
                 return -EROFS;
 
         journal_lock_updates(journal);
         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)
                 EXT3_I(inode)->i_flags |= EXT3_JOURNAL_DATA_FL;
         else
                 EXT3_I(inode)->i_flags &= ~EXT3_JOURNAL_DATA_FL;
         ext3_set_aops(inode);
 
         journal_unlock_updates(journal);
 
         /* Finally we can mark the inode as dirty. */
 
         handle = ext3_journal_start(inode, 1);
         if (IS_ERR(handle))
                 return PTR_ERR(handle);
 
         err = ext3_mark_inode_dirty(handle, inode);
         handle->h_sync = 1;
         ext3_journal_stop(handle);
         ext3_std_error(inode->i_sb, err);
 
         return err;
 }