[RFC][PATCH 2/3] Move the file data to the new blocks

[sho@tnes.nec.co.jp]

Move the blocks on the temporary inode to the original inode
by a page.
1. Read the file data from the old blocks to the page
2. Move the block on the temporary inode to the original inode
3. Write the file data on the page into the new blocks

Signed-off-by: Takashi Sato <sho@tnes.nec.co.jp>
---
diff -Nrup -X linux-2.6.19-rc6-1/Documentation/dontdiff linux-2.6.19-rc6-1/fs/ext4/extents.c linux-2.6.19-rc6-full/fs/ext4/extents.c
--- linux-2.6.19-rc6-1/fs/ext4/extents.c	2006-12-22 14:41:49.000000000 +0900
+++ linux-2.6.19-rc6-full/fs/ext4/extents.c	2006-12-22 14:56:17.000000000 +0900
@@ -2518,6 +2518,470 @@ ext4_ext_next_extent(struct inode *inode
 }
 
 /**
+ * ext4_ext_merge_extents - merge new extent to the extent block
+ *
+ * @handle      journal handle
+ * @inode       target file's inode
+ * @org_path    path indicates first extent to be defraged
+ * @o_start     first original extent to be defraged
+ * @o_end       last original extent to be defraged
+ * @start_ext   first new extent to be merged
+ * @new_ext     middle of new extent to be merged
+ * @end_ext     last new extent to be merged
+ * @replaced    the number of blocks which will be replaced with new_ext
+ *
+ * This function returns 0 if succeed, otherwise returns -1.
+ */
+static int
+ext4_ext_merge_extents(handle_t *handle, struct inode *inode,
+		struct ext4_ext_path *org_path,
+		struct ext4_extent *o_start, struct ext4_extent *o_end,
+		struct ext4_extent *start_ext, struct ext4_extent *new_ext,
+		struct ext4_extent *end_ext, unsigned long replaced)
+{
+	int	i = 0;
+	unsigned need_slots;
+	unsigned slots_range, len;
+	int	 range_to_move;
+	struct	ext4_extent_header * eh;
+	struct	ext4_extent *free_start, *free_end;
+	int	depth;
+
+	/* The extents need to be inserted
+	 * start_extent + new_extent + end_extent
+	 */
+	need_slots = (le16_to_cpu(start_ext->ee_len) ? 1 : 0) +
+			(le16_to_cpu(end_ext->ee_len) ? 1 : 0) +
+			(le16_to_cpu(new_ext->ee_len) ? 1 : 0);
+
+	/* The number of slots between start and end */
+	slots_range = o_end - o_start + 1;
+
+	/* Range to move the end of extent */
+	range_to_move = need_slots - slots_range;
+	depth = org_path->p_depth;
+	org_path += depth;
+	eh = org_path->p_hdr;
+	/* expansion */
+	if (range_to_move > 0) {
+		if (range_to_move > le16_to_cpu(eh->eh_max)
+				- le16_to_cpu(eh->eh_entries)) {
+			printk("Cannot merge extents due to no space\n");
+			return -1;
+		}
+	}
+	if (depth) {
+		/* Register to journal */
+		if (ext4_journal_get_write_access(handle, org_path->p_bh)) {
+			return -1;
+		}
+	}
+
+	/* Free old blocks
+	 * dest        |---------------|
+	 * org  |---------------|
+	 */
+	free_start = o_start;
+	free_end = o_end;
+	if (le16_to_cpu(start_ext->ee_len)) {
+		if (le16_to_cpu(o_start->ee_len)
+			> le16_to_cpu(start_ext->ee_len)) {
+			ext4_free_blocks(handle, inode,
+				ext_pblock(o_start)
+					+ le16_to_cpu(start_ext->ee_len),
+				le16_to_cpu(o_start->ee_len)
+					- le16_to_cpu(start_ext->ee_len), 0);
+		}
+		free_start++;
+	}
+
+	/* dest |----------------|
+	 * org          |---------------|
+	 */
+	if (le16_to_cpu(end_ext->ee_len)) {
+		ext4_free_blocks(handle, inode, ext_pblock(o_end),
+			le16_to_cpu(o_end->ee_len)
+				- le16_to_cpu(end_ext->ee_len), 0);
+		free_end--;
+	}
+
+	/* dest |-------------------|
+	 * org   |-----------------|
+	 */
+	for (; free_start <= free_end; free_start++) {
+		ext4_free_blocks(handle, inode,
+			ext_pblock(free_start),
+			le32_to_cpu(free_start->ee_len), 0);
+	}
+
+	/* Move the existing extents */
+	if (range_to_move && o_end < EXT_LAST_EXTENT(eh)) {
+		len = EXT_LAST_EXTENT(eh) - (o_end + 1) + 1;
+		len = len * sizeof(struct ext4_extent);
+		memmove(o_end + 1 + range_to_move, o_end + 1, len);
+	}
+
+	/* Insert start entry */
+	if (le16_to_cpu(start_ext->ee_len)) {
+		o_start[i++].ee_len = start_ext->ee_len;
+	}
+
+	/* Insert new entry */
+	if (le16_to_cpu(new_ext->ee_len)) {
+		o_start[i].ee_block = new_ext->ee_block;
+		o_start[i].ee_len = cpu_to_le16(replaced);
+		ext4_ext_store_pblock(&o_start[i++], ext_pblock(new_ext));
+	}
+
+	/* Insert end entry */
+	if (end_ext->ee_len) {
+		o_start[i] = *end_ext;
+	}
+
+	/* Increment the total entries counter on the extent block */
+	eh->eh_entries
+		= cpu_to_le16(le16_to_cpu(eh->eh_entries) + range_to_move);
+	if (depth) {
+		if (ext4_journal_dirty_metadata(handle, org_path->p_bh)) {
+			return -1;
+		}
+	} else {
+		if (ext4_mark_inode_dirty(handle, inode) < 0) {
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * ext4_ext_defrag_leaf_block -  Defragmentation for one leaf extent block.
+ * @handle      journal handle
+ * @org_inode   target inode
+ * @org_path    path indicates first extent to be defraged
+ * @dext        destination extent
+ * @from        start offset on the target file
+ *
+ * This function returns 0 if succeed, otherwise returns error value.
+ */
+static int
+ext4_ext_defrag_leaf_block(handle_t *handle, struct inode *org_inode,
+		struct ext4_ext_path *org_path, struct ext4_extent *dext,
+		unsigned long *from, unsigned long *delete_start)
+{
+	unsigned long depth, replaced = 0;
+	struct ext4_extent *oext, *o_start = NULL, *o_end = NULL, *prev_ext;
+	struct ext4_extent new_ext, start_ext, end_ext;
+	unsigned long new_end;
+	unsigned long lblock;
+	unsigned long len;
+	unsigned long long new_phys_end;
+	int	ret;
+
+	depth = ext_depth(org_inode);
+	start_ext.ee_len = end_ext.ee_len = 0;
+	o_start = o_end = oext = org_path[depth].p_ext;
+	ext4_ext_store_pblock(&new_ext, ext_pblock(dext));	
+	len = new_ext.ee_len = dext->ee_len;
+	new_ext.ee_block = cpu_to_le32(*from);
+	lblock = le32_to_cpu(oext->ee_block);
+	new_end = le32_to_cpu(new_ext.ee_block)
+		+ le16_to_cpu(new_ext.ee_len) - 1;
+	new_phys_end = ext_pblock(&new_ext)
+		+ le16_to_cpu(new_ext.ee_len) - 1;
+
+	/* First original extent
+	 * dest         |---------------|
+	 * org  |---------------|
+	 */
+	if (le32_to_cpu(new_ext.ee_block) >
+		le32_to_cpu(oext->ee_block) &&
+		le32_to_cpu(new_ext.ee_block) <
+		le32_to_cpu(oext->ee_block)
+		+ le16_to_cpu(oext->ee_len)) {
+		start_ext.ee_len = cpu_to_le32(le32_to_cpu(new_ext.ee_block)
+					- le32_to_cpu(oext->ee_block));
+		replaced += le16_to_cpu(oext->ee_len)
+					- le16_to_cpu(start_ext.ee_len);
+	} else if (oext > EXT_FIRST_EXTENT(org_path[depth].p_hdr)) {
+		/* We can merge previous extent. */
+		prev_ext = oext -1;
+		if ((ext_pblock(prev_ext)
+			+ le32_to_cpu(prev_ext->ee_len))
+			== ext_pblock(&new_ext)) {
+			o_start = prev_ext;
+			start_ext.ee_len = cpu_to_le32(
+					le16_to_cpu(prev_ext->ee_len)
+					+ le16_to_cpu(new_ext.ee_len));
+			new_ext.ee_len = 0;
+		}
+	}
+
+	for (;;) {
+
+		/* The extent for destination must be found. */
+		BUG_ON(!oext || lblock != le32_to_cpu(oext->ee_block));
+		lblock += le16_to_cpu(oext->ee_len);
+
+		/* Middle of original extent
+		 * dest |-------------------|
+		 * org   |-----------------|
+		 */
+		if (le32_to_cpu(new_ext.ee_block) <=
+			le32_to_cpu(oext->ee_block) &&
+			new_end >= le32_to_cpu(oext->ee_block)
+			+ le16_to_cpu(oext->ee_len) -1) {
+			replaced += le16_to_cpu(oext->ee_len);
+		}
+
+		/* Last original extent
+		 * dest |----------------|
+		 * org          |---------------|
+		 */
+		if (new_end >= le32_to_cpu(oext->ee_block) &&
+			new_end < le32_to_cpu(oext->ee_block)
+				+ le16_to_cpu(oext->ee_len) - 1) {
+			end_ext.ee_len
+				= cpu_to_le16(le32_to_cpu(oext->ee_block)
+				+ le16_to_cpu(oext->ee_len) -1 - new_end);
+			ext4_ext_store_pblock(&end_ext, (ext_pblock(o_end)
+				+ cpu_to_le16(oext->ee_len)
+				- cpu_to_le16(end_ext.ee_len)));
+			end_ext.ee_block
+				= cpu_to_le32(le32_to_cpu(o_end->ee_block)
+				+ le16_to_cpu(oext->ee_len)
+				- le16_to_cpu(end_ext.ee_len));
+			replaced += le16_to_cpu(oext->ee_len)
+				- le16_to_cpu(end_ext.ee_len);
+		}
+
+		/* Detected the block end, reached the number of replaced
+		 * blocks to dext->ee_len.  Then, merge the extent.
+		 */
+		if (oext == EXT_LAST_EXTENT(org_path[depth].p_hdr) ||
+			new_end <= le32_to_cpu(oext->ee_block)
+				+ le16_to_cpu(oext->ee_len) - 1) {
+			if (ext4_ext_merge_extents(handle, org_inode,
+				org_path, o_start, o_end,
+				&start_ext, &new_ext, &end_ext, replaced) < 0) {
+				return -EIO;
+			}
+
+			*delete_start = le32_to_cpu(new_ext.ee_block)
+							+ replaced;
+
+			/* All expected blocks are replaced */
+			if (new_ext.ee_len <= 0) {
+				if (DQUOT_ALLOC_BLOCK
+					(org_inode, len)) {
+					return -EDQUOT;
+				}
+				return 0;
+			}
+
+			/* re-calculate new_ext */
+			new_ext.ee_len = cpu_to_le32(le16_to_cpu(new_ext.ee_len)
+				- replaced);
+			new_ext.ee_block =
+				cpu_to_le32(le32_to_cpu(new_ext.ee_block)
+				+ replaced);
+			ext4_ext_store_pblock(&new_ext, ext_pblock(&new_ext)
+					 + replaced);
+			replaced = 0;
+			start_ext.ee_len = end_ext.ee_len = 0;
+			o_start = NULL;
+
+			/* All expected blocks are replaced */
+			if (new_ext.ee_len <= 0) {
+				if (DQUOT_ALLOC_BLOCK
+					(org_inode, len)) {
+					return -EDQUOT;
+				}
+				return 0;
+			}
+		}
+
+		/* Get next extent for original. */
+		if ((ret
+		 = ext4_ext_next_extent(org_inode, org_path, &oext))
+								!= 0) {
+			if (ret == 1)
+				ret = -EIO;
+			return ret;
+		}
+		o_end = oext;
+		if (!o_start)
+			o_start = oext;
+	}
+}
+
+/**
+ * ext4_ext_replace_branches - replace original extents with new extents.
+ * @org_inode    Original inode
+ * @dest_inode   temporary inode
+ * @from_page    Page offset
+ * @count_page   Page count to be replaced
+ * @delete_start block offset for deletion
+ *
+ * This function returns 0 if succeed, otherwise returns error value.
+ * Replace extents for blocks from "from" to "from+count-1".
+ */
+static int
+ext4_ext_replace_branches(struct inode *org_inode, struct inode *dest_inode,
+			pgoff_t from_page,  pgoff_t dest_from_page,
+			pgoff_t count_page, unsigned long *delete_start) 
+{
+	struct ext4_ext_path *org_path = NULL;
+	struct ext4_ext_path *dest_path = NULL;
+	struct ext4_extent   *oext, *dext;
+	struct ext4_extent   tmp_ext;
+	int	err = 0;
+	int	depth;
+	unsigned long from, count, dest_off, diff, replaced_count = 0;
+	handle_t *handle = NULL;
+	unsigned jnum;
+
+	from = from_page << (PAGE_CACHE_SHIFT - dest_inode->i_blkbits);
+	count = count_page << (PAGE_CACHE_SHIFT - dest_inode->i_blkbits);
+	dest_off = dest_from_page << (PAGE_CACHE_SHIFT - 
+			dest_inode->i_blkbits);
+	jnum = ext4_ext_writepage_trans_blocks(org_inode, count) + 3;
+	handle = ext4_journal_start(org_inode, jnum);
+	if (IS_ERR(handle)) {
+		err = PTR_ERR(handle);
+		goto out;
+	}
+
+	/* Get the original extent for the block "from" */
+	org_path = ext4_ext_find_extent(org_inode, from, NULL);
+	if (IS_ERR(org_path)) {
+		err = PTR_ERR(org_path);
+		org_path = NULL;
+		goto out;
+	}
+
+	/* Get the destination extent for the head */
+	dest_path = ext4_ext_find_extent(dest_inode, dest_off, NULL);
+	if (IS_ERR(dest_path)) {
+		err = PTR_ERR(dest_path);
+		dest_path = NULL;
+		goto out;
+	}
+	depth = ext_depth(dest_inode);
+	dext = dest_path[depth].p_ext;
+	/* When dext is too large, pick up the target range. */
+	diff = dest_off - le32_to_cpu(dext->ee_block);
+	ext4_ext_store_pblock(&tmp_ext, ext_pblock(dext) + diff);
+	tmp_ext.ee_block = cpu_to_le32(le32_to_cpu(dext->ee_block) + diff);
+	tmp_ext.ee_len = cpu_to_le16(le16_to_cpu(dext->ee_len) - diff);
+	if (count < tmp_ext.ee_len) {
+		tmp_ext.ee_len = cpu_to_le16(count);
+	}
+	dext = &tmp_ext;
+
+	/* loop for the destination extents */
+	while (1) {
+		/* The extent for destination must be found. */
+		BUG_ON(!dext || dest_off != le32_to_cpu(dext->ee_block));
+
+		/* loop for the original extent blocks */
+		if ((err = ext4_ext_defrag_leaf_block(handle, org_inode,
+			org_path, dext, &from, delete_start)) < 0) {
+			goto out;
+		}
+
+		replaced_count += le16_to_cpu(dext->ee_len);
+		dest_off += le16_to_cpu(dext->ee_len);
+		from += le16_to_cpu(dext->ee_len);
+
+		/* Already moved the expected blocks */
+		if (replaced_count >= count)
+			break;
+
+		/* get the next extent on both original and destination. */
+		err = ext4_ext_next_extent(dest_inode, dest_path, &dext);
+		if (err != 0) {
+			if (err > 0) {
+				err = 0;
+			}
+			goto out;
+		}
+		if ((err =
+			ext4_ext_next_extent(org_inode, org_path, &oext)) < 0) {
+			goto out;
+		}
+	}
+out:
+	if (handle) {
+		ext4_journal_stop(handle);
+	}
+	if (org_path) {
+		ext4_ext_drop_refs(org_path);
+		kfree(org_path);
+	}
+	if (dest_path) {
+		ext4_ext_drop_refs(dest_path);
+		kfree(dest_path);
+	}
+
+	return err;
+}
+
+/**
+ * ext4_ext_remove_index_blocks - remove leaf blocks and index blocks
+ * @handle      handle
+ * @dest_inode  temporary inode
+ * @eh          extent header
+ * @depth       depth of extent tree
+ *
+ * This function returns 0 if succeed, otherwise returns error value
+ */
+static int ext4_ext_remove_index_blocks(handle_t *handle,
+			struct inode *dest_inode,
+			struct ext4_extent_header *eh, int depth)
+{
+	struct ext4_extent_idx *idx;
+	struct buffer_head *bh;
+	int metadata = 1;
+	int credits = 0;
+	int i, ret = 0;
+
+	if (depth == 0) {
+		eh->eh_entries = 0;
+		return 0;
+	}
+
+	idx = EXT_FIRST_INDEX(eh);
+
+	for (i = 1; i <= eh->eh_entries; i++) {
+		if (depth > 1) {
+			bh = sb_bread(dest_inode->i_sb, idx->ei_leaf);
+			if (!bh) {
+				ret = -EIO;
+			} else {
+				ret = ext4_ext_remove_index_blocks(handle,
+					dest_inode, ext_block_hdr(bh),
+					depth - 1);
+				brelse(bh);
+			}
+		}
+#ifdef CONFIG_QUOTA
+		credits = 2 * EXT4_QUOTA_TRANS_BLOCKS(dest_inode->i_sb);
+#endif
+		handle = ext4_ext_journal_restart(handle,
+				credits + EXT4_TRANS_META_BLOCKS);
+		if (IS_ERR(handle))
+			return PTR_ERR(handle);
+
+		ext4_free_blocks(handle, dest_inode,
+				idx->ei_leaf, 1, metadata);
+		eh->eh_entries--;
+		idx++;
+	}
+	return ret;
+}
+
+/**
  * ext4_ext_alloc_blocks - allocate contiguous blocks to temporary inode
  * @dest_inode   temporary inode for multiple block allocation
  * @iblock       file related offset
@@ -2645,6 +3109,61 @@ out2:
 }
 
 /**
+ * ext4_ext_defrag_partial - defrag original file partially
+ * @filp:		pointer to file
+ * @org_offset:		page index on original file
+ * @dest_offset:	page index on temporary file
+ *
+ * This function returns 0 if succeeded, otherwise returns error value
+ */
+static int
+ext4_ext_defrag_partial(struct inode *tmp_inode,
+			struct file *filp,
+			pgoff_t org_offset,
+			pgoff_t dest_offset, unsigned long *delete_start)
+{
+	struct inode *inode = filp->f_dentry->d_inode;
+	struct address_space *mapping = inode->i_mapping;
+	struct page *page;
+	pgoff_t offset_in_page = PAGE_SIZE;
+	int ret = 0;
+
+	page = read_cache_page(inode->i_mapping,
+		       org_offset, (filler_t *)inode->i_mapping->a_ops->readpage,
+		       NULL);
+
+	if (IS_ERR(page)) {
+		ret = PTR_ERR(page);
+		return ret;
+	}
+
+	wait_on_page_locked(page);
+	lock_page(page);
+	/* release old bh and drop refs */
+	try_to_release_page(page, 0);
+	ret = ext4_ext_replace_branches(inode, tmp_inode, org_offset, 
+			dest_offset, 1, delete_start);
+	if (ret < 0)
+		goto ERR;
+
+	if (org_offset == ((inode->i_size - 1) >> PAGE_SHIFT))
+		offset_in_page = (inode->i_size & (PAGE_CACHE_SIZE - 1));
+
+	ret = mapping->a_ops->prepare_write(filp, page,
+					    0, offset_in_page);
+	if (ret)
+		goto ERR;
+
+	ret = mapping->a_ops->commit_write(filp, page,
+					   0, offset_in_page);
+ERR:
+	unlock_page(page);
+	page_cache_release(page);
+
+	return (ret < 0 ? ret : 0);
+}
+
+/**
  * ext4_ext_new_extent_tree -  allocate contiguous blocks
  * @inode:		inode of the original file
  * @tmp_inode:		inode of the temporary file