ext4: cleanup ext4_ext_grow_indepth code

Currently code make an impression what grow procedure is very complicated
and some mythical paths, blocks are involved. But in fact grow in depth
it relatively simple procedure:
 1) Just create new meta block and copy root data to that block.
 2) Convert root from extent to index if old depth == 0
 3) Update root block pointer

This patch does:
 - Reorganize code to make it more self explanatory
 - Do not pass path parameter to new_meta_block() in order to
   provoke allocation from inode's group because top-level block
   should site closer to it's inode, but not to leaf data block.

   [ This happens anyway, due to logic in mballoc; we should drop
     the path parameter from new_meta_block() entirely.  -- tytso ]
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/extents.c

@@ -1050,16 +1050,14 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
  */
 static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
 				 unsigned int flags,
-				 struct ext4_ext_path *path,
 				 struct ext4_extent *newext)
 {
-	struct ext4_ext_path *curp = path;
 	struct ext4_extent_header *neh;
 	struct buffer_head *bh;
 	ext4_fsblk_t newblock;
 	int err = 0;
 
-	newblock = ext4_ext_new_meta_block(handle, inode, path,
+	newblock = ext4_ext_new_meta_block(handle, inode, NULL,
 		newext, &err, flags);
 	if (newblock == 0)
 		return err;
@@ -1079,7 +1077,8 @@ static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
 	}
 
 	/* move top-level index/leaf into new block */
-	memmove(bh->b_data, curp->p_hdr, sizeof(EXT4_I(inode)->i_data));
+	memmove(bh->b_data, EXT4_I(inode)->i_data,
+		sizeof(EXT4_I(inode)->i_data));
 
 	/* set size of new block */
 	neh = ext_block_hdr(bh);
@@ -1097,32 +1096,23 @@ static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
 	if (err)
 		goto out;
 
-	/* create index in new top-level index: num,max,pointer */
-	err = ext4_ext_get_access(handle, inode, curp);
-	if (err)
-		goto out;
-
-	curp->p_hdr->eh_magic = EXT4_EXT_MAGIC;
-	curp->p_hdr->eh_max = cpu_to_le16(ext4_ext_space_root_idx(inode, 0));
-	curp->p_hdr->eh_entries = cpu_to_le16(1);
-	curp->p_idx = EXT_FIRST_INDEX(curp->p_hdr);
-
-	if (path[0].p_hdr->eh_depth)
-		curp->p_idx->ei_block =
-			EXT_FIRST_INDEX(path[0].p_hdr)->ei_block;
-	else
-		curp->p_idx->ei_block =
-			EXT_FIRST_EXTENT(path[0].p_hdr)->ee_block;
-	ext4_idx_store_pblock(curp->p_idx, newblock);
-
+	/* Update top-level index: num,max,pointer */
 	neh = ext_inode_hdr(inode);
+	neh->eh_entries = cpu_to_le16(1);
+	ext4_idx_store_pblock(EXT_FIRST_INDEX(neh), newblock);
+	if (neh->eh_depth == 0) {
+		/* Root extent block becomes index block */
+		neh->eh_max = cpu_to_le16(ext4_ext_space_root_idx(inode, 0));
+		EXT_FIRST_INDEX(neh)->ei_block =
+			EXT_FIRST_EXTENT(neh)->ee_block;
+	}
 	ext_debug("new root: num %d(%d), lblock %d, ptr %llu\n",
 		  le16_to_cpu(neh->eh_entries), le16_to_cpu(neh->eh_max),
 		  le32_to_cpu(EXT_FIRST_INDEX(neh)->ei_block),
 		  ext4_idx_pblock(EXT_FIRST_INDEX(neh)));
 
-	neh->eh_depth = cpu_to_le16(path->p_depth + 1);
-	err = ext4_ext_dirty(handle, inode, curp);
+	neh->eh_depth = cpu_to_le16(neh->eh_depth + 1);
+	ext4_mark_inode_dirty(handle, inode);
 out:
 	brelse(bh);
 
@@ -1170,8 +1160,7 @@ static int ext4_ext_create_new_leaf(handle_t *handle, struct inode *inode,
 			err = PTR_ERR(path);
 	} else {
 		/* tree is full, time to grow in depth */
-		err = ext4_ext_grow_indepth(handle, inode, flags,
-					    path, newext);
+		err = ext4_ext_grow_indepth(handle, inode, flags, newext);
 		if (err)
 			goto out;