removes static definition of dx_root struct. so that "." and ".." dirent can
have extra data. This patch does not change any functionality but is required for
ext4_data_in_dirent patch.
 
Index: linux-3.10.0-123.9.3.el7.x86_64/fs/ext4/namei.c
===================================================================
--- linux-3.10.0-123.9.3.el7.x86_64.orig/fs/ext4/namei.c
+++ linux-3.10.0-123.9.3.el7.x86_64/fs/ext4/namei.c
@@ -193,22 +193,13 @@ struct dx_entry
  * hash version mod 4 should never be 0.  Sincerely, the paranoia department.
  */
 
-struct dx_root
+struct dx_root_info
 {
-	struct fake_dirent dot;
-	char dot_name[4];
-	struct fake_dirent dotdot;
-	char dotdot_name[4];
-	struct dx_root_info
-	{
-		__le32 reserved_zero;
-		u8 hash_version;
-		u8 info_length; /* 8 */
-		u8 indirect_levels;
-		u8 unused_flags;
-	}
-	info;
-	struct dx_entry	entries[0];
+	__le32 reserved_zero;
+	u8 hash_version;
+	u8 info_length; /* 8 */
+	u8 indirect_levels;
+	u8 unused_flags;
 };
 
 struct dx_node
@@ -511,6 +502,16 @@ ext4_next_entry(struct ext4_dir_entry_2
  * Future: use high four bits of block for coalesce-on-delete flags
  * Mask them off for now.
  */
+struct dx_root_info *dx_get_dx_info(struct ext4_dir_entry_2 *de)
+{
+	/* get dotdot first */
+	de = (struct ext4_dir_entry_2 *)((char *)de + EXT4_DIR_REC_LEN(1));
+
+	/* dx root info is after dotdot entry */
+	de = (struct ext4_dir_entry_2 *)((char *)de + EXT4_DIR_REC_LEN(2));
+
+	return (struct dx_root_info *)de;
+}
 
 static inline ext4_lblk_t dx_get_block(struct dx_entry *entry)
 {
@@ -673,7 +674,7 @@ dx_probe(const struct qstr *d_name, stru
 {
 	unsigned count, indirect;
 	struct dx_entry *at, *entries, *p, *q, *m;
-	struct dx_root *root;
+	struct dx_root_info *info;
 	struct buffer_head *bh;
 	struct dx_frame *frame = frame_in;
 	u32 hash;
@@ -684,17 +685,18 @@ dx_probe(const struct qstr *d_name, stru
 		*err = PTR_ERR(bh);
 		goto fail;
 	}
-	root = (struct dx_root *) bh->b_data;
-	if (root->info.hash_version != DX_HASH_TEA &&
-	    root->info.hash_version != DX_HASH_HALF_MD4 &&
-	    root->info.hash_version != DX_HASH_LEGACY) {
-		ext4_warning(dir->i_sb, "Unrecognised inode hash code %d for directory "
-                             "#%lu", root->info.hash_version, dir->i_ino);
+
+	info = dx_get_dx_info((struct ext4_dir_entry_2 *)bh->b_data);
+	if (info->hash_version != DX_HASH_TEA &&
+	    info->hash_version != DX_HASH_HALF_MD4 &&
+	    info->hash_version != DX_HASH_LEGACY) {
+		ext4_warning(dir->i_sb, "inode #%lu: unrecognised hash code %u",
+			     dir->i_ino, info->hash_version);
 		brelse(bh);
 		*err = ERR_BAD_DX_DIR;
 		goto fail;
 	}
-	hinfo->hash_version = root->info.hash_version;
+	hinfo->hash_version = info->hash_version;
 	if (hinfo->hash_version <= DX_HASH_TEA)
 		hinfo->hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
 	hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed;
@@ -702,28 +704,33 @@ dx_probe(const struct qstr *d_name, stru
 		ext4fs_dirhash(d_name->name, d_name->len, hinfo);
 	hash = hinfo->hash;
 
-	if (root->info.unused_flags & 1) {
-		ext4_warning(dir->i_sb, "Unimplemented inode hash flags: %#06x",
-			     root->info.unused_flags);
+	if (info->unused_flags & 1) {
+		ext4_warning(dir->i_sb,
+			     "inode #%lu: unimplemented hash flags: %#06x",
+			     dir->i_ino, info->unused_flags);
 		brelse(bh);
 		*err = ERR_BAD_DX_DIR;
 		goto fail;
 	}
 
-	if ((indirect = root->info.indirect_levels) > 1) {
-		ext4_warning(dir->i_sb, "Unimplemented inode hash depth: %#06x",
-			     root->info.indirect_levels);
+	indirect = info->indirect_levels;
+	if (indirect > 1) {
+		ext4_warning(dir->i_sb,
+			     "inode #%lu: unimplemented hash depth %u",
+			     dir->i_ino, info->indirect_levels);
 		brelse(bh);
 		*err = ERR_BAD_DX_DIR;
 		goto fail;
 	}
 
-	entries = (struct dx_entry *) (((char *)&root->info) +
-				       root->info.info_length);
+	entries = (struct dx_entry *)(((char *)info) + info->info_length);
 
 	if (dx_get_limit(entries) != dx_root_limit(dir,
-						   root->info.info_length)) {
-		ext4_warning(dir->i_sb, "dx entry: limit != root limit");
+						   info->info_length)) {
+		ext4_warning(dir->i_sb, "dx entry: limit != root limit "
+			     "inode #%lu: dx entry: limit %u != root limit %u",
+			     dir->i_ino, dx_get_limit(entries),
+			     dx_root_limit(dir, info->info_length));
 		brelse(bh);
 		*err = ERR_BAD_DX_DIR;
 		goto fail;
@@ -807,10 +808,12 @@ fail:
 
 static void dx_release (struct dx_frame *frames)
 {
+	struct dx_root_info *info;
 	if (frames[0].bh == NULL)
 		return;
 
-	if (((struct dx_root *) frames[0].bh->b_data)->info.indirect_levels)
+	info = dx_get_dx_info((struct ext4_dir_entry_2 *)frames[0].bh->b_data);
+	if (info->indirect_levels)
 		brelse(frames[1].bh);
 	brelse(frames[0].bh);
 }
@@ -1787,10 +1790,9 @@ static int make_indexed_dir(handle_t *ha
 	const char	*name = dentry->d_name.name;
 	int		namelen = dentry->d_name.len;
 	struct buffer_head *bh2;
-	struct dx_root	*root;
 	struct dx_frame	frames[2], *frame;
 	struct dx_entry *entries;
-	struct ext4_dir_entry_2	*de, *de2;
+	struct ext4_dir_entry_2 *de, *de2, *dot_de, *dotdot_de;
 	struct ext4_dir_entry_tail *t;
 	char		*data1, *top;
 	unsigned	len;
@@ -1798,7 +1800,7 @@ static int make_indexed_dir(handle_t *ha
 	unsigned	blocksize;
 	struct dx_hash_info hinfo;
 	ext4_lblk_t  block;
-	struct fake_dirent *fde;
+	struct dx_root_info *dx_info;
 	int		csum_size = 0;
 
 	if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
@@ -1813,18 +1815,19 @@ static int make_indexed_dir(handle_t *ha
 		brelse(bh);
 		return retval;
 	}
-	root = (struct dx_root *) bh->b_data;
+
+	dot_de = (struct ext4_dir_entry_2 *)bh->b_data;
+	dotdot_de = ext4_next_entry(dot_de, blocksize);
 
 	/* The 0th block becomes the root, move the dirents out */
-	fde = &root->dotdot;
-	de = (struct ext4_dir_entry_2 *)((char *)fde +
-		ext4_rec_len_from_disk(fde->rec_len, blocksize));
-	if ((char *) de >= (((char *) root) + blocksize)) {
+	de = (struct ext4_dir_entry_2 *)((char *)dotdot_de +
+		ext4_rec_len_from_disk(dotdot_de->rec_len, blocksize));
+	if ((char *)de >= (((char *)dot_de) + blocksize)) {
 		EXT4_ERROR_INODE(dir, "invalid rec_len for '..'");
 		brelse(bh);
 		return -EIO;
 	}
-	len = ((char *) root) + (blocksize - csum_size) - (char *) de;
+	len = ((char *)dot_de) + (blocksize - csum_size) - (char *)de;
 
 	/* Allocate new block for the 0th block's dirents */
 	bh2 = ext4_append(handle, dir, &block);
@@ -1850,19 +1853,24 @@ static int make_indexed_dir(handle_t *ha
 	}
 
 	/* Initialize the root; the dot dirents already exist */
-	de = (struct ext4_dir_entry_2 *) (&root->dotdot);
-	de->rec_len = ext4_rec_len_to_disk(blocksize - EXT4_DIR_REC_LEN(2),
-					   blocksize);
-	memset (&root->info, 0, sizeof(root->info));
-	root->info.info_length = sizeof(root->info);
-	root->info.hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
-	entries = root->entries;
+	dotdot_de->rec_len =
+		ext4_rec_len_to_disk(blocksize - le16_to_cpu(dot_de->rec_len),
+				     blocksize);
+
+	/* initialize hashing info */
+	dx_info = dx_get_dx_info(dot_de);
+	memset(dx_info, 0, sizeof(*dx_info));
+	dx_info->info_length = sizeof(*dx_info);
+	dx_info->hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
+
+	entries = (void *)dx_info + sizeof(*dx_info);
+
 	dx_set_block(entries, 1);
 	dx_set_count(entries, 1);
-	dx_set_limit(entries, dx_root_limit(dir, sizeof(root->info)));
+	dx_set_limit(entries, dx_root_limit(dir, sizeof(*dx_info)));
 
 	/* Initialize as for dx_probe */
-	hinfo.hash_version = root->info.hash_version;
+	hinfo.hash_version = dx_info->hash_version;
 	if (hinfo.hash_version <= DX_HASH_TEA)
 		hinfo.hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
 	hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
@@ -2152,6 +2159,7 @@ static int ext4_dx_add_entry(handle_t *h
 				goto journal_error;
 			brelse (bh2);
 		} else {
+			struct dx_root_info *info;
 			dxtrace(printk(KERN_DEBUG
 				       "Creating second level index...\n"));
 			memcpy((char *) entries2, (char *) entries,
@@ -2161,7 +2169,9 @@ static int ext4_dx_add_entry(handle_t *h
 			/* Set up root */
 			dx_set_count(entries, 1);
 			dx_set_block(entries + 0, newblock);
-			((struct dx_root *) frames[0].bh->b_data)->info.indirect_levels = 1;
+			info = dx_get_dx_info((struct ext4_dir_entry_2 *)
+					      frames[0].bh->b_data);
+			info->indirect_levels = 1;
 
 			/* Add new access path frame */
 			frame = frames + 1;