text: /*
   *  linux/fs/ext2/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@dcs.ed.ac.uk), 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 ext2_get_block() by Al Viro, 2000
   */
  
  #include <linux/smp_lock.h>
  #include <linux/time.h>
  #include <linux/highuid.h>
  #include <linux/pagemap.h>
  #include <linux/quotaops.h>
  #include <linux/module.h>
  #include <linux/writeback.h>
  #include <linux/buffer_head.h>
  #include <linux/mpage.h>
  #include <linux/fiemap.h>
  #include <linux/namei.h>
  #include "ext2.h"
  #include "acl.h"
  #include "xip.h"
  
  MODULE_AUTHOR("Remy Card and others");
  MODULE_DESCRIPTION("Second Extended Filesystem");
  MODULE_LICENSE("GPL");
  
  /*
   * Test whether an inode is a fast symlink.
   */
  static inline int ext2_inode_is_fast_symlink(struct inode *inode)
  {
  	int ea_blocks = EXT2_I(inode)->i_file_acl ?
  		(inode->i_sb->s_blocksize >> 9) : 0;
  
  	return (S_ISLNK(inode->i_mode) &&
  		inode->i_blocks - ea_blocks == 0);
  }
  
  /*
   * Called at the last iput() if i_nlink is zero.
   */
  void ext2_delete_inode (struct inode * inode)
  {
  	truncate_inode_pages(&inode->i_data, 0);
  
  	if (is_bad_inode(inode))
  		goto no_delete;
  	EXT2_I(inode)->i_dtime	= get_seconds();
  	mark_inode_dirty(inode);
  	ext2_write_inode(inode, inode_needs_sync(inode));
  
  	inode->i_size = 0;
  	if (inode->i_blocks)
  		ext2_truncate (inode);
  	ext2_free_inode (inode);
  
  	return;
  no_delete:
  	clear_inode(inode);	/* We must guarantee clearing of inode... */
  }
  
  typedef struct {
  	__le32	*p;
  	__le32	key;
  	struct buffer_head *bh;
  } Indirect;
  
  static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
  {
  	p->key = *(p->p = v);
  	p->bh = bh;
  }
  
  static inline int verify_chain(Indirect *from, Indirect *to)
  {
  	while (from <= to && from->key == *from->p)
  		from++;
  	return (from > to);
  }
  
  /**
   *	ext2_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 ext2 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 ext2_block_to_path(struct inode *inode,
  			long i_block, int offsets[4], int *boundary)
  {
  	int ptrs = EXT2_ADDR_PER_BLOCK(inode->i_sb);
  	int ptrs_bits = EXT2_ADDR_PER_BLOCK_BITS(inode->i_sb);
  	const long direct_blocks = EXT2_NDIR_BLOCKS,
  		indirect_blocks = ptrs,
  		double_blocks = (1 << (ptrs_bits * 2));
  	int n = 0;
  	int final = 0;
  
  	if (i_block < 0) {
  		ext2_msg(inode->i_sb, KERN_WARNING,
  			"warning: %s: block < 0", __func__);
  	} else if (i_block < direct_blocks) {
  		offsets[n++] = i_block;
  		final = direct_blocks;
  	} else if ( (i_block -= direct_blocks) < indirect_blocks) {
  		offsets[n++] = EXT2_IND_BLOCK;
  		offsets[n++] = i_block;
  		final = ptrs;
  	} else if ((i_block -= indirect_blocks) < double_blocks) {
  		offsets[n++] = EXT2_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++] = EXT2_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 {
  		ext2_msg(inode->i_sb, KERN_WARNING,
  			"warning: %s: block is too big", __func__);
  	}
  	if (boundary)
  		*boundary = final - 1 - (i_block & (ptrs - 1));
  
  	return n;
  }
  
  /**
   *	ext2_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 *ext2_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, EXT2_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;
  		read_lock(&EXT2_I(inode)->i_meta_lock);
  		if (!verify_chain(chain, p))
  			goto changed;
  		add_chain(++p, bh, (__le32*)bh->b_data + *++offsets);
  		read_unlock(&EXT2_I(inode)->i_meta_lock);
  		if (!p->key)
  			goto no_block;
  	}
  	return NULL;
  
  changed:
  	read_unlock(&EXT2_I(inode)->i_meta_lock);
  	brelse(bh);
  	*err = -EAGAIN;
  	goto no_block;
  failure:
  	*err = -EIO;
  no_block:
  	return p;
  }
  
  /**
   *	ext2_find_near - find a place for allocation with sufficient locality
   *	@inode: owner
   *	@ind: descriptor of indirect block.
   *
   *	This function returns the preferred 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 ext2_fsblk_t ext2_find_near(struct inode *inode, Indirect *ind)
  {
  	struct ext2_inode_info *ei = EXT2_I(inode);
  	__le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
  	__le32 *p;
  	ext2_fsblk_t bg_start;
  	ext2_fsblk_t colour;
  
  	/* Try to find previous block */
  	for (p = ind->p - 1; p >= start; p--)
  		if (*p)
  			return le32_to_cpu(*p);
  
  	/* No such thing, so let's try location of indirect block */
  	if (ind->bh)
  		return ind->bh->b_blocknr;
  
  	/*
  	 * It is going to be refered from inode itself? OK, just put it into
  	 * the same cylinder group then.
  	 */
  	bg_start = ext2_group_first_block_no(inode->i_sb, ei->i_block_group);
  	colour = (current->pid % 16) *
  			(EXT2_BLOCKS_PER_GROUP(inode->i_sb) / 16);
  	return bg_start + colour;
  }
  
  /**
   *	ext2_find_goal - find a preferred place for allocation.
   *	@inode: owner
   *	@block:  block we want
   *	@partial: pointer to the last triple within a chain
   *
   *	Returns preferred place for a block (the goal).
   */
  
  static inline ext2_fsblk_t ext2_find_goal(struct inode *inode, long block,
  					  Indirect *partial)
  {
  	struct ext2_block_alloc_info *block_i;
  
  	block_i = EXT2_I(inode)->i_block_alloc_info;
  
  	/*
  	 * try the heuristic for sequential allocation,
  	 * failing that at least try to get decent locality.
  	 */
  	if (block_i && (block == block_i->last_alloc_logical_block + 1)
  		&& (block_i->last_alloc_physical_block != 0)) {
  		return block_i->last_alloc_physical_block + 1;
  	}
  
  	return ext2_find_near(inode, partial);
  }
  
  /**
   *	ext2_blks_to_allocate: Look up the block map and count the number
   *	of direct blocks need to be allocated for the given branch.
   *
   * 	@branch: chain of indirect blocks
   *	@k: number of blocks need for indirect blocks
   *	@blks: number of data blocks to be mapped.
   *	@blocks_to_boundary:  the offset in the indirect block
   *
   *	return the total number of blocks to be allocate, including the
   *	direct and indirect blocks.
   */
  static int
  ext2_blks_to_allocate(Indirect * branch, int k, unsigned long blks,
  		int blocks_to_boundary)
  {
  	unsigned long count = 0;
  
  	/*
  	 * Simple case, [t,d]Indirect block(s) has not allocated yet
  	 * then it's clear blocks on that path have not allocated
  	 */
  	if (k > 0) {
  		/* right now don't hanel cross boundary allocation */
  		if (blks < blocks_to_boundary + 1)
  			count += blks;
  		else
  			count += blocks_to_boundary + 1;
  		return count;
  	}
  
  	count++;
  	while (count < blks && count <= blocks_to_boundary
  		&& le32_to_cpu(*(branch[0].p + count)) == 0) {
  		count++;
  	}
  	return count;
  }
  
  /**
   *	ext2_alloc_blocks: multiple allocate blocks needed for a branch
   *	@indirect_blks: the number of blocks need to allocate for indirect
   *			blocks
   *
   *	@new_blocks: on return it will store the new block numbers for
   *	the indirect blocks(if needed) and the first direct block,
   *	@blks:	on return it will store the total number of allocated
   *		direct blocks
   */
  static int ext2_alloc_blocks(struct inode *inode,
  			ext2_fsblk_t goal, int indirect_blks, int blks,
  			ext2_fsblk_t new_blocks[4], int *err)
  {
  	int target, i;
  	unsigned long count = 0;
  	int index = 0;
  	ext2_fsblk_t current_block = 0;
  	int ret = 0;
  
  	/*
  	 * Here we try to allocate the requested multiple blocks at once,
  	 * on a best-effort basis.
  	 * To build a branch, we should allocate blocks for
  	 * the indirect blocks(if not allocated yet), and at least
  	 * the first direct block of this branch.  That's the
  	 * minimum number of blocks need to allocate(required)
  	 */
  	target = blks + indirect_blks;
  
  	while (1) {
  		count = target;
  		/* allocating blocks for indirect blocks and direct blocks */
  		current_block = ext2_new_blocks(inode,goal,&count,err);
  		if (*err)
  			goto failed_out;
  
  		target -= count;
  		/* allocate blocks for indirect blocks */
  		while (index < indirect_blks && count) {
  			new_blocks[index++] = current_block++;
  			count--;
  		}
  
  		if (count > 0)
  			break;
  	}
  
  	/* save the new block number for the first direct block */
  	new_blocks[index] = current_block;
  
  	/* total number of blocks allocated for direct blocks */
  	ret = count;
  	*err = 0;
  	return ret;
  failed_out:
  	for (i = 0; i <index; i++)
  		ext2_free_blocks(inode, new_blocks[i], 1);
  	return ret;
  }
  
  /**
   *	ext2_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 ext2_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 ext2_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
   *	ext2_alloc_block() (normally -ENOSPC). Otherwise we set the chain
   *	as described above and return 0.
   */
  
  static int ext2_alloc_branch(struct inode *inode,
  			int indirect_blks, int *blks, ext2_fsblk_t goal,
  			int *offsets, Indirect *branch)
  {
  	int blocksize = inode->i_sb->s_blocksize;
  	int i, n = 0;
  	int err = 0;
  	struct buffer_head *bh;
  	int num;
  	ext2_fsblk_t new_blocks[4];
  	ext2_fsblk_t current_block;
  
  	num = ext2_alloc_blocks(inode, goal, indirect_blks,
  				*blks, new_blocks, &err);
  	if (err)
  		return err;
  
  	branch[0].key = cpu_to_le32(new_blocks[0]);
  	/*
  	 * metadata blocks and data blocks are allocated.
  	 */
  	for (n = 1; n <= indirect_blks;  n++) {
  		/*
  		 * Get buffer_head for parent block, zero it out
  		 * and set the pointer to new one, then send
  		 * parent to disk.
  		 */
  		bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
  		branch[n].bh = bh;
  		lock_buffer(bh);
  		memset(bh->b_data, 0, blocksize);
  		branch[n].p = (__le32 *) bh->b_data + offsets[n];
  		branch[n].key = cpu_to_le32(new_blocks[n]);
  		*branch[n].p = branch[n].key;
  		if ( n == indirect_blks) {
  			current_block = new_blocks[n];
  			/*
  			 * End of chain, update the last new metablock of
  			 * the chain to point to the new allocated
  			 * data blocks numbers
  			 */
  			for (i=1; i < num; i++)
  				*(branch[n].p + i) = cpu_to_le32(++current_block);
  		}
  		set_buffer_uptodate(bh);
  		unlock_buffer(bh);
  		mark_buffer_dirty_inode(bh, inode);
  		/* We used to sync bh here if IS_SYNC(inode).
  		 * But we now rely upon generic_write_sync()
  		 * and b_inode_buffers.  But not for directories.
  		 */
  		if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode))
  			sync_dirty_buffer(bh);
  	}
  	*blks = num;
  	return err;
  }
  
  /**
   * ext2_splice_branch - splice the allocated branch onto inode.
   * @inode: owner
   * @block: (logical) number of block we are adding
   * @where: location of missing link
   * @num:   number of indirect blocks we are adding
   * @blks:  number of direct blocks we are adding
   *
   * This function fills the missing link and does all housekeeping needed in
   * inode (->i_blocks, etc.). In case of success we end up with the full
   * chain to new block and return 0.
   */
  static void ext2_splice_branch(struct inode *inode,
  			long block, Indirect *where, int num, int blks)
  {
  	int i;
  	struct ext2_block_alloc_info *block_i;
  	ext2_fsblk_t current_block;
  
  	block_i = EXT2_I(inode)->i_block_alloc_info;
  
  	/* XXX LOCKING probably should have i_meta_lock ?*/
  	/* That's it */
  
  	*where->p = where->key;
  
  	/*
  	 * Update the host buffer_head or inode to point to more just allocated
  	 * direct blocks blocks
  	 */
  	if (num == 0 && blks > 1) {
  		current_block = le32_to_cpu(where->key) + 1;
  		for (i = 1; i < blks; i++)
  			*(where->p + i ) = cpu_to_le32(current_block++);
  	}
  
  	/*
  	 * update the most recently allocated logical & physical block
  	 * in i_block_alloc_info, to assist find the proper goal block for next
  	 * allocation
  	 */
  	if (block_i) {
  		block_i->last_alloc_logical_block = block + blks - 1;
  		block_i->last_alloc_physical_block =
  				le32_to_cpu(where[num].key) + blks - 1;
  	}
  
  	/* We are done with atomic stuff, now do the rest of housekeeping */
  
  	/* had we spliced it onto indirect block? */
  	if (where->bh)
  		mark_buffer_dirty_inode(where->bh, inode);
  
  	inode->i_ctime = CURRENT_TIME_SEC;
  	mark_inode_dirty(inode);
  }
  
  /*
   * Allocation strategy is simple: if we have to allocate something, we will
   * have to go the whole way to leaf. So let's do it before attaching anything
   * to tree, set linkage between the newborn blocks, write them if sync is
   * required, recheck the path, free and repeat if check fails, otherwise
   * set the last missing link (that will protect us from any truncate-generated
   * removals - all blocks on the path are immune now) and possibly force the
   * write on the parent block.
   * That has a nice additional property: no special recovery from the failed
   * allocations is needed - we simply release blocks and do not touch anything
   * reachable from inode.
   *
   * `handle' can be NULL if create == 0.
   *
   * return > 0, # of blocks mapped or allocated.
   * return = 0, if plain lookup failed.
   * return < 0, error case.
   */
  static int ext2_get_blocks(struct inode *inode,
  			   sector_t iblock, unsigned long maxblocks,
  			   struct buffer_head *bh_result,
  			   int create)
  {
  	int err = -EIO;
  	int offsets[4];
  	Indirect chain[4];
  	Indirect *partial;
  	ext2_fsblk_t goal;
  	int indirect_blks;
  	int blocks_to_boundary = 0;
  	int depth;
  	struct ext2_inode_info *ei = EXT2_I(inode);
  	int count = 0;
  	ext2_fsblk_t first_block = 0;
  
  	depth = ext2_block_to_path(inode,iblock,offsets,&blocks_to_boundary);
  
  	if (depth == 0)
  		return (err);
  
  	partial = ext2_get_branch(inode, depth, offsets, chain, &err);
  	/* Simplest case - block found, no allocation needed */
  	if (!partial) {
  		first_block = le32_to_cpu(chain[depth - 1].key);
  		clear_buffer_new(bh_result); /* What's this do? */
  		count++;
  		/*map more blocks*/
  		while (count < maxblocks && count <= blocks_to_boundary) {
  			ext2_fsblk_t blk;
  
  			if (!verify_chain(chain, chain + depth - 1)) {
  				/*
  				 * Indirect block might be removed by
  				 * truncate while we were reading it.
  				 * Handling of that case: forget what we've
  				 * got now, go to reread.
  				 */
  				err = -EAGAIN;
  				count = 0;
  				break;
  			}
  			blk = le32_to_cpu(*(chain[depth-1].p + count));
  			if (blk == first_block + count)
  				count++;
  			else
  				break;
  		}
  		if (err != -EAGAIN)
  			goto got_it;
  	}
  
  	/* Next simple case - plain lookup or failed read of indirect block */
  	if (!create || err == -EIO)
  		goto cleanup;
  
  	mutex_lock(&ei->truncate_mutex);
  	/*
  	 * If the indirect block is missing while we are reading
  	 * the chain(ext3_get_branch() returns -EAGAIN err), or
  	 * if the chain has been changed after we grab the semaphore,
  	 * (either because another process truncated this branch, or
  	 * another get_block allocated this branch) re-grab the chain to see if
  	 * the request block has been allocated or not.
  	 *
  	 * Since we already block the truncate/other get_block
  	 * at this point, we will have the current copy of the chain when we
  	 * splice the branch into the tree.
  	 */
  	if (err == -EAGAIN || !verify_chain(chain, partial)) {
  		while (partial > chain) {
  			brelse(partial->bh);
  			partial--;
  		}
  		partial = ext2_get_branch(inode, depth, offsets, chain, &err);
  		if (!partial) {
  			count++;
  			mutex_unlock(&ei->truncate_mutex);
  			if (err)
  				goto cleanup;
  			clear_buffer_new(bh_result);
  			goto got_it;
  		}
  	}
  
  	/*
  	 * Okay, we need to do block allocation.  Lazily initialize the block
  	 * allocation info here if necessary
  	*/
  	if (S_ISREG(inode->i_mode) && (!ei->i_block_alloc_info))
  		ext2_init_block_alloc_info(inode);
  
  	goal = ext2_find_goal(inode, iblock, partial);
  
  	/* the number of blocks need to allocate for [d,t]indirect blocks */
  	indirect_blks = (chain + depth) - partial - 1;
  	/*
  	 * Next look up the indirect map to count the totoal number of
  	 * direct blocks to allocate for this branch.
  	 */
  	count = ext2_blks_to_allocate(partial, indirect_blks,
  					maxblocks, blocks_to_boundary);
  	/*
  	 * XXX ???? Block out ext2_truncate while we alter the tree
  	 */
  	err = ext2_alloc_branch(inode, indirect_blks, &count, goal,
  				offsets + (partial - chain), partial);
  
  	if (err) {
  		mutex_unlock(&ei->truncate_mutex);
  		goto cleanup;
  	}
  
  	if (ext2_use_xip(inode->i_sb)) {
  		/*
  		 * we need to clear the block
  		 */
  		err = ext2_clear_xip_target (inode,
  			le32_to_cpu(chain[depth-1].key));
  		if (err) {
  			mutex_unlock(&ei->truncate_mutex);
  			goto cleanup;
  		}
  	}
  
  	ext2_splice_branch(inode, iblock, partial, indirect_blks, count);
  	mutex_unlock(&ei->truncate_mutex);
  	set_buffer_new(bh_result);
  got_it:
  	map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
  	if (count > blocks_to_boundary)
  		set_buffer_boundary(bh_result);
  	err = count;
  	/* Clean up and exit */
  	partial = chain + depth - 1;	/* the whole chain */
  cleanup:
  	while (partial > chain) {
  		brelse(partial->bh);
  		partial--;
  	}
  	return err;
  }
  
  int ext2_get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create)
  {
  	unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
  	int ret = ext2_get_blocks(inode, iblock, max_blocks,
  			      bh_result, create);
  	if (ret > 0) {
  		bh_result->b_size = (ret << inode->i_blkbits);
  		ret = 0;
  	}
  	return ret;
  
  }
  
  int ext2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
  		u64 start, u64 len)
  {
  	return generic_block_fiemap(inode, fieinfo, start, len,
  				    ext2_get_block);
  }
  
  static int ext2_writepage(struct page *page, struct writeback_control *wbc)
  {
  	return block_write_full_page(page, ext2_get_block, wbc);
  }
  
  static int ext2_readpage(struct file *file, struct page *page)
  {
  	return mpage_readpage(page, ext2_get_block);
  }
  
  static int
  ext2_readpages(struct file *file, struct address_space *mapping,
  		struct list_head *pages, unsigned nr_pages)
  {
  	return mpage_readpages(mapping, pages, nr_pages, ext2_get_block);
  }
  
  int __ext2_write_begin(struct file *file, struct address_space *mapping,
  		loff_t pos, unsigned len, unsigned flags,
  		struct page **pagep, void **fsdata)
  {
  	return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
  							ext2_get_block);
  }
  
  static int
  ext2_write_begin(struct file *file, struct address_space *mapping,
  		loff_t pos, unsigned len, unsigned flags,
  		struct page **pagep, void **fsdata)
  {
  	*pagep = NULL;
  	return __ext2_write_begin(file, mapping, pos, len, flags, pagep,fsdata);
  }
  
  static int
  ext2_nobh_write_begin(struct file *file, struct address_space *mapping,
  		loff_t pos, unsigned len, unsigned flags,
  		struct page **pagep, void **fsdata)
  {
  	/*
  	 * Dir-in-pagecache still uses ext2_write_begin. Would have to rework
  	 * directory handling code to pass around offsets rather than struct
  	 * pages in order to make this work easily.
  	 */
  	return nobh_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
  							ext2_get_block);
  }
  
  static int ext2_nobh_writepage(struct page *page,
  			struct writeback_control *wbc)
  {
  	return nobh_writepage(page, ext2_get_block, wbc);
  }
  
  static sector_t ext2_bmap(struct address_space *mapping, sector_t block)
  {
  	return generic_block_bmap(mapping,block,ext2_get_block);
  }
  
  static ssize_t
  ext2_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;
  
  	return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
  				offset, nr_segs, ext2_get_block, NULL);
  }
  
  static int
  ext2_writepages(struct address_space *mapping, struct writeback_control *wbc)
  {
  	return mpage_writepages(mapping, wbc, ext2_get_block);
  }
  
  const struct address_space_operations ext2_aops = {
  	.readpage		= ext2_readpage,
  	.readpages		= ext2_readpages,
  	.writepage		= ext2_writepage,
  	.sync_page		= block_sync_page,
  	.write_begin		= ext2_write_begin,
  	.write_end		= generic_write_end,
  	.bmap			= ext2_bmap,
  	.direct_IO		= ext2_direct_IO,
  	.writepages		= ext2_writepages,
  	.migratepage		= buffer_migrate_page,
  	.is_partially_uptodate	= block_is_partially_uptodate,
  	.error_remove_page	= generic_error_remove_page,
  };
  
  const struct address_space_operations ext2_aops_xip = {
  	.bmap			= ext2_bmap,
  	.get_xip_mem		= ext2_get_xip_mem,
  };
  
  const struct address_space_operations ext2_nobh_aops = {
  	.readpage		= ext2_readpage,
  	.readpages		= ext2_readpages,
  	.writepage		= ext2_nobh_writepage,
  	.sync_page		= block_sync_page,
  	.write_begin		= ext2_nobh_write_begin,
  	.write_end		= nobh_write_end,
  	.bmap			= ext2_bmap,
  	.direct_IO		= ext2_direct_IO,
  	.writepages		= ext2_writepages,
  	.migratepage		= buffer_migrate_page,
  	.error_remove_page	= generic_error_remove_page,
  };
  
  /*
   * 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;
  }
  
  /**
   *	ext2_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 ext2_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 ext2_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 ext2_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].p
   *			(no partially truncated stuff there).
   */
  
  static Indirect *ext2_find_shared(struct inode *inode,
  				int depth,
  				int offsets[4],
  				Indirect chain[4],
  				__le32 *top)
  {
  	Indirect *partial, *p;
  	int k, err;
  
  	*top = 0;
  	for (k = depth; k > 1 && !offsets[k-1]; k--)
  		;
  	partial = ext2_get_branch(inode, k, offsets, chain, &err);
  	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.
  	 */
  	write_lock(&EXT2_I(inode)->i_meta_lock);
  	if (!partial->key && *partial->p) {
  		write_unlock(&EXT2_I(inode)->i_meta_lock);
  		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;
  		*p->p = 0;
  	}
  	write_unlock(&EXT2_I(inode)->i_meta_lock);
  
  	while(partial > p)
  	{
  		brelse(partial->bh);
  		partial--;
  	}
  no_top:
  	return partial;
  }
  
  /**
   *	ext2_free_data - free a list of data blocks
   *	@inode:	inode we are dealing with
   *	@p:	array of block numbers
   *	@q:	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.
   */
  static inline void ext2_free_data(struct inode *inode, __le32 *p, __le32 *q)
  {
  	unsigned long block_to_free = 0, count = 0;
  	unsigned long nr;
  
  	for ( ; p < q ; p++) {
  		nr = le32_to_cpu(*p);
  		if (nr) {
  			*p = 0;
  			/* accumulate blocks to free if they're contiguous */
  			if (count == 0)
  				goto free_this;
  			else if (block_to_free == nr - count)
  				count++;
  			else {
  				mark_inode_dirty(inode);
  				ext2_free_blocks (inode, block_to_free, count);
  			free_this:
  				block_to_free = nr;
  				count = 1;
  			}
  		}
  	}
  	if (count > 0) {
  		mark_inode_dirty(inode);
  		ext2_free_blocks (inode, block_to_free, count);
  	}
  }
  
  /**
   *	ext2_free_branches - free an array of branches
   *	@inode:	inode we are dealing with
   *	@p:	array of block numbers
   *	@q:	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 ext2_free_branches(struct inode *inode, __le32 *p, __le32 *q, int depth)
  {
  	struct buffer_head * bh;
  	unsigned long nr;
  
  	if (depth--) {
  		int addr_per_block = EXT2_ADDR_PER_BLOCK(inode->i_sb);
  		for ( ; p < q ; p++) {
  			nr = le32_to_cpu(*p);
  			if (!nr)
  				continue;
  			*p = 0;
  			bh = sb_bread(inode->i_sb, nr);
  			/*
  			 * A read failure? Report error and clear slot
  			 * (should be rare).
  			 */ 
  			if (!bh) {
  				ext2_error(inode->i_sb, "ext2_free_branches",
  					"Read failure, inode=%ld, block=%ld",
  					inode->i_ino, nr);
  				continue;
  			}
  			ext2_free_branches(inode,
  					   (__le32*)bh->b_data,
  					   (__le32*)bh->b_data + addr_per_block,
  					   depth);
  			bforget(bh);
  			ext2_free_blocks(inode, nr, 1);
  			mark_inode_dirty(inode);
  		}
  	} else
  		ext2_free_data(inode, p, q);
  }
  
  void ext2_truncate(struct inode *inode)
  {
  	__le32 *i_data = EXT2_I(inode)->i_data;
  	struct ext2_inode_info *ei = EXT2_I(inode);
  	int addr_per_block = EXT2_ADDR_PER_BLOCK(inode->i_sb);
  	int offsets[4];
  	Indirect chain[4];
  	Indirect *partial;
  	__le32 nr = 0;
  	int n;
  	long iblock;
  	unsigned blocksize;
  
  	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
  	    S_ISLNK(inode->i_mode)))
  		return;
  	if (ext2_inode_is_fast_symlink(inode))
  		return;
  	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
  		return;
  
  	blocksize = inode->i_sb->s_blocksize;
  	iblock = (inode->i_size + blocksize-1)
  					>> EXT2_BLOCK_SIZE_BITS(inode->i_sb);
  
  	if (mapping_is_xip(inode->i_mapping))
  		xip_truncate_page(inode->i_mapping, inode->i_size);
  	else if (test_opt(inode->i_sb, NOBH))
  		nobh_truncate_page(inode->i_mapping,
  				inode->i_size, ext2_get_block);
  	else
  		block_truncate_page(inode->i_mapping,
  				inode->i_size, ext2_get_block);
  
  	n = ext2_block_to_path(inode, iblock, offsets, NULL);
  	if (n == 0)
  		return;
  
  	/*
  	 * From here we block out all ext2_get_block() callers who want to
  	 * modify the block allocation tree.
  	 */
  	mutex_lock(&ei->truncate_mutex);
  
  	if (n == 1) {
  		ext2_free_data(inode, i_data+offsets[0],
  					i_data + EXT2_NDIR_BLOCKS);
  		goto do_indirects;
  	}
  
  	partial = ext2_find_shared(inode, n, offsets, chain, &nr);
  	/* Kill the top of shared branch (already detached) */
  	if (nr) {
  		if (partial == chain)
  			mark_inode_dirty(inode);
  		else
  			mark_buffer_dirty_inode(partial->bh, inode);
  		ext2_free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
  	}
  	/* Clear the ends of indirect blocks on the shared branch */
  	while (partial > chain) {
  		ext2_free_branches(inode,
  				   partial->p + 1,
  				   (__le32*)partial->bh->b_data+addr_per_block,
  				   (chain+n-1) - partial);
  		mark_buffer_dirty_inode(partial->bh, inode);
  		brelse (partial->bh);
  		partial--;
  	}
  do_indirects:
  	/* Kill the remaining (whole) subtrees */
  	switch (offsets[0]) {
  		default:
  			nr = i_data[EXT2_IND_BLOCK];
  			if (nr) {
  				i_data[EXT2_IND_BLOCK] = 0;
  				mark_inode_dirty(inode);
  				ext2_free_branches(inode, &nr, &nr+1, 1);
  			}
  		case EXT2_IND_BLOCK:
  			nr = i_data[EXT2_DIND_BLOCK];
  			if (nr) {
  				i_data[EXT2_DIND_BLOCK] = 0;
  				mark_inode_dirty(inode);
  				ext2_free_branches(inode, &nr, &nr+1, 2);
  			}
  		case EXT2_DIND_BLOCK:
  			nr = i_data[EXT2_TIND_BLOCK];
  			if (nr) {
  				i_data[EXT2_TIND_BLOCK] = 0;
  				mark_inode_dirty(inode);
  				ext2_free_branches(inode, &nr, &nr+1, 3);
  			}
  		case EXT2_TIND_BLOCK:
  			;
  	}
  
  	ext2_discard_reservation(inode);
  
  	mutex_unlock(&ei->truncate_mutex);
  	inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
  	if (inode_needs_sync(inode)) {
  		sync_mapping_buffers(inode->i_mapping);
  		ext2_sync_inode (inode);
  	} else {
  		mark_inode_dirty(inode);
  	}
  }
  
  static struct ext2_inode *ext2_get_inode(struct super_block *sb, ino_t ino,
  					struct buffer_head **p)
  {
  	struct buffer_head * bh;
  	unsigned long block_group;
  	unsigned long block;
  	unsigned long offset;
  	struct ext2_group_desc * gdp;
  
  	*p = NULL;
  	if ((ino != EXT2_ROOT_INO && ino < EXT2_FIRST_INO(sb)) ||
  	    ino > le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count))
  		goto Einval;
  
  	block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb);
  	gdp = ext2_get_group_desc(sb, block_group, NULL);
  	if (!gdp)
  		goto Egdp;
  	/*
  	 * Figure out the offset within the block group inode table
  	 */
  	offset = ((ino - 1) % EXT2_INODES_PER_GROUP(sb)) * EXT2_INODE_SIZE(sb);
  	block = le32_to_cpu(gdp->bg_inode_table) +
  		(offset >> EXT2_BLOCK_SIZE_BITS(sb));
  	if (!(bh = sb_bread(sb, block)))
  		goto Eio;
  
  	*p = bh;
  	offset &= (EXT2_BLOCK_SIZE(sb) - 1);
  	return (struct ext2_inode *) (bh->b_data + offset);
  
  Einval:
  	ext2_error(sb, "ext2_get_inode", "bad inode number: %lu",
  		   (unsigned long) ino);
  	return ERR_PTR(-EINVAL);
  Eio:
  	ext2_error(sb, "ext2_get_inode",
  		   "unable to read inode block - inode=%lu, block=%lu",
  		   (unsigned long) ino, block);
  Egdp:
  	return ERR_PTR(-EIO);
  }
  
  void ext2_set_inode_flags(struct inode *inode)
  {
  	unsigned int flags = EXT2_I(inode)->i_flags;
  
  	inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
  	if (flags & EXT2_SYNC_FL)
  		inode->i_flags |= S_SYNC;
  	if (flags & EXT2_APPEND_FL)
  		inode->i_flags |= S_APPEND;
  	if (flags & EXT2_IMMUTABLE_FL)
  		inode->i_flags |= S_IMMUTABLE;
  	if (flags & EXT2_NOATIME_FL)
  		inode->i_flags |= S_NOATIME;
  	if (flags & EXT2_DIRSYNC_FL)
  		inode->i_flags |= S_DIRSYNC;
  }
  
  /* Propagate flags from i_flags to EXT2_I(inode)->i_flags */
  void ext2_get_inode_flags(struct ext2_inode_info *ei)
  {
  	unsigned int flags = ei->vfs_inode.i_flags;
  
  	ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|
  			EXT2_IMMUTABLE_FL|EXT2_NOATIME_FL|EXT2_DIRSYNC_FL);
  	if (flags & S_SYNC)
  		ei->i_flags |= EXT2_SYNC_FL;
  	if (flags & S_APPEND)
  		ei->i_flags |= EXT2_APPEND_FL;
  	if (flags & S_IMMUTABLE)
  		ei->i_flags |= EXT2_IMMUTABLE_FL;
  	if (flags & S_NOATIME)
  		ei->i_flags |= EXT2_NOATIME_FL;
  	if (flags & S_DIRSYNC)
  		ei->i_flags |= EXT2_DIRSYNC_FL;
  }
  
  struct inode *ext2_iget (struct super_block *sb, unsigned long ino)
  {
  	struct ext2_inode_info *ei;
  	struct buffer_head * bh;
  	struct ext2_inode *raw_inode;
  	struct inode *inode;
  	long ret = -EIO;
  	int n;
  
  	inode = iget_locked(sb, ino);
  	if (!inode)
  		return ERR_PTR(-ENOMEM);
  	if (!(inode->i_state & I_NEW))
  		return inode;
  
  	ei = EXT2_I(inode);
  	ei->i_block_alloc_info = NULL;
  
  	raw_inode = ext2_get_inode(inode->i_sb, ino, &bh);
  	if (IS_ERR(raw_inode)) {
  		ret = PTR_ERR(raw_inode);
   		goto bad_inode;
  	}
  
  	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 = (signed)le32_to_cpu(raw_inode->i_atime);
  	inode->i_ctime.tv_sec = (signed)le32_to_cpu(raw_inode->i_ctime);
  	inode->i_mtime.tv_sec = (signed)le32_to_cpu(raw_inode->i_mtime);
  	inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 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 && (inode->i_mode == 0 || ei->i_dtime)) {
  		/* this inode is deleted */
  		brelse (bh);
  		ret = -ESTALE;
  		goto bad_inode;
  	}
  	inode->i_blocks = le32_to_cpu(raw_inode->i_blocks);
  	ei->i_flags = le32_to_cpu(raw_inode->i_flags);
  	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;
  	ei->i_file_acl = le32_to_cpu(raw_inode->i_file_acl);
  	ei->i_dir_acl = 0;
  	if (S_ISREG(inode->i_mode))
  		inode->i_size |= ((__u64)le32_to_cpu(raw_inode->i_size_high)) << 32;
  	else
  		ei->i_dir_acl = le32_to_cpu(raw_inode->i_dir_acl);
  	ei->i_dtime = 0;
  	inode->i_generation = le32_to_cpu(raw_inode->i_generation);
  	ei->i_state = 0;
  	ei->i_block_group = (ino - 1) / EXT2_INODES_PER_GROUP(inode->i_sb);
  	ei->i_dir_start_lookup = 0;
  
  	/*
  	 * 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 (n = 0; n < EXT2_N_BLOCKS; n++)
  		ei->i_data[n] = raw_inode->i_block[n];
  
  	if (S_ISREG(inode->i_mode)) {
  		inode->i_op = &ext2_file_inode_operations;
  		if (ext2_use_xip(inode->i_sb)) {
  			inode->i_mapping->a_ops = &ext2_aops_xip;
  			inode->i_fop = &ext2_xip_file_operations;
  		} else if (test_opt(inode->i_sb, NOBH)) {
  			inode->i_mapping->a_ops = &ext2_nobh_aops;
  			inode->i_fop = &ext2_file_operations;
  		} else {
  			inode->i_mapping->a_ops = &ext2_aops;
  			inode->i_fop = &ext2_file_operations;
  		}
  	} else if (S_ISDIR(inode->i_mode)) {
  		inode->i_op = &ext2_dir_inode_operations;
  		inode->i_fop = &ext2_dir_operations;
  		if (test_opt(inode->i_sb, NOBH))
  			inode->i_mapping->a_ops = &ext2_nobh_aops;
  		else
  			inode->i_mapping->a_ops = &ext2_aops;
  	} else if (S_ISLNK(inode->i_mode)) {
  		if (ext2_inode_is_fast_symlink(inode)) {
  			inode->i_op = &ext2_fast_symlink_inode_operations;
  			nd_terminate_link(ei->i_data, inode->i_size,
  				sizeof(ei->i_data) - 1);
  		} else {
  			inode->i_op = &ext2_symlink_inode_operations;
  			if (test_opt(inode->i_sb, NOBH))
  				inode->i_mapping->a_ops = &ext2_nobh_aops;
  			else
  				inode->i_mapping->a_ops = &ext2_aops;
  		}
  	} else {
  		inode->i_op = &ext2_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 (bh);
  	ext2_set_inode_flags(inode);
  	unlock_new_inode(inode);
  	return inode;
  	
  bad_inode:
  	iget_failed(inode);
  	return ERR_PTR(ret);
  }
  
  int ext2_write_inode(struct inode *inode, int do_sync)
  {
  	struct ext2_inode_info *ei = EXT2_I(inode);
  	struct super_block *sb = inode->i_sb;
  	ino_t ino = inode->i_ino;
  	uid_t uid = inode->i_uid;
  	gid_t gid = inode->i_gid;
  	struct buffer_head * bh;
  	struct ext2_inode * raw_inode = ext2_get_inode(sb, ino, &bh);
  	int n;
  	int err = 0;
  
  	if (IS_ERR(raw_inode))
   		return -EIO;
  
  	/* For fields not not tracking in the in-memory inode,
  	 * initialise them to zero for new inodes. */
  	if (ei->i_state & EXT2_STATE_NEW)
  		memset(raw_inode, 0, EXT2_SB(sb)->s_inode_size);
  
  	ext2_get_inode_flags(ei);
  	raw_inode->i_mode = cpu_to_le16(inode->i_mode);
  	if (!(test_opt(sb, NO_UID32))) {
  		raw_inode->i_uid_low = cpu_to_le16(low_16_bits(uid));
  		raw_inode->i_gid_low = cpu_to_le16(low_16_bits(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(uid));
  			raw_inode->i_gid_high = cpu_to_le16(high_16_bits(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(uid));
  		raw_inode->i_gid_low = cpu_to_le16(fs_high2lowgid(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(inode->i_size);
  	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);
  	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;
  	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(inode->i_size >> 32);
  		if (inode->i_size > 0x7fffffffULL) {
  			if (!EXT2_HAS_RO_COMPAT_FEATURE(sb,
  					EXT2_FEATURE_RO_COMPAT_LARGE_FILE) ||
  			    EXT2_SB(sb)->s_es->s_rev_level ==
  					cpu_to_le32(EXT2_GOOD_OLD_REV)) {
  			       /* If this is the first large file
  				* created, add a flag to the superblock.
  				*/
  				lock_kernel();
  				ext2_update_dynamic_rev(sb);
  				EXT2_SET_RO_COMPAT_FEATURE(sb,
  					EXT2_FEATURE_RO_COMPAT_LARGE_FILE);
  				unlock_kernel();
  				ext2_write_super(sb);
  			}
  		}
  	}
  	
  	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 (n = 0; n < EXT2_N_BLOCKS; n++)
  		raw_inode->i_block[n] = ei->i_data[n];
  	mark_buffer_dirty(bh);
  	if (do_sync) {
  		sync_dirty_buffer(bh);
  		if (buffer_req(bh) && !buffer_uptodate(bh)) {
  			printk ("IO error syncing ext2 inode [%s:%08lx]\n",
  				sb->s_id, (unsigned long) ino);
  			err = -EIO;
  		}
  	}
  	ei->i_state &= ~EXT2_STATE_NEW;
  	brelse (bh);
  	return err;
  }
  
  int ext2_sync_inode(struct inode *inode)
  {
  	struct writeback_control wbc = {
  		.sync_mode = WB_SYNC_ALL,
  		.nr_to_write = 0,	/* sys_fsync did this */
  	};
  	return sync_inode(inode, &wbc);
  }
  
  int ext2_setattr(struct dentry *dentry, struct iattr *iattr)
  {
  	struct inode *inode = dentry->d_inode;
  	int error;
  
  	error = inode_change_ok(inode, iattr);
  	if (error)
  		return error;
  	if ((iattr->ia_valid & ATTR_UID && iattr->ia_uid != inode->i_uid) ||
  	    (iattr->ia_valid & ATTR_GID && iattr->ia_gid != inode->i_gid)) {
  		error = vfs_dq_transfer(inode, iattr) ? -EDQUOT : 0;
  		if (error)
  			return error;
  	}
  	error = inode_setattr(inode, iattr);
  	if (!error && (iattr->ia_valid & ATTR_MODE))
  		error = ext2_acl_chmod(inode);
  	return error;
  }
  