add user data field in ext4 dirent

Index: b/fs/ext4/dir.c
===================================================================
@@ -53,6 +53,8 @@ const struct file_operations ext4_dir_op
 
 static unsigned char get_dtype(struct super_block *sb, int filetype)
 {
+	filetype &= EXT4_FT_MASK;
+
 	if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FILETYPE) ||
 	    (filetype >= EXT4_FT_MAX))
 		return DT_UNKNOWN;

@@ -70,11 +72,11 @@ int ext4_check_dir_entry(const char *fun
 	const int rlen = ext4_rec_len_from_disk(de->rec_len,
 						dir->i_sb->s_blocksize);
 
-	if (rlen < EXT4_DIR_REC_LEN(1))
+	if (rlen < __EXT4_DIR_REC_LEN(1))
 		error_msg = "rec_len is smaller than minimal";
 	else if (rlen % 4 != 0)
 		error_msg = "rec_len % 4 != 0";
-	else if (rlen < EXT4_DIR_REC_LEN(de->name_len))
+	else if (rlen < EXT4_DIR_REC_LEN(de))
 		error_msg = "rec_len is too small for name_len";
 	else if (((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize)
 		error_msg = "directory entry across blocks";

@@ -179,7 +181,7 @@ revalidate:
 				 * failure will be detected in the
 				 * dirent test below. */
 				if (ext4_rec_len_from_disk(de->rec_len,
-					sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
+					sb->s_blocksize) < __EXT4_DIR_REC_LEN(1))
 					break;
 				i += ext4_rec_len_from_disk(de->rec_len,
 							    sb->s_blocksize);

@@ -215,12 +217,13 @@ revalidate:
 				 * during the copy operation.
 				 */
 				u64 version = filp->f_version;
-
 				error = filldir(dirent, de->name,
 						de->name_len,
 						filp->f_pos,
 						le32_to_cpu(de->inode),
-						get_dtype(sb, de->file_type));
+						get_dtype(sb, de->file_type)|
+						(de->file_type &
+                                                 EXT4_DIRENT_LUFID));
 				if (error)
 					break;
 				if (version != filp->f_version)

@@ -342,12 +345,17 @@ int ext4_htree_store_dirent(struct file 
 	struct fname *fname, *new_fn;
 	struct dir_private_info *info;
 	int len;
+	int extra_data = 1;
 
 	info = (struct dir_private_info *) dir_file->private_data;
 	p = &info->root.rb_node;
 
 	/* Create and allocate the fname structure */
-	len = sizeof(struct fname) + dirent->name_len + 1;
+	if (dirent->file_type & EXT4_DIRENT_LUFID)
+		extra_data = ext4_get_dirent_data_len(dirent);
+
+	len = sizeof(struct fname) + dirent->name_len + extra_data;
+
 	new_fn = kzalloc(len, GFP_KERNEL);
 	if (!new_fn)
 		return -ENOMEM;

@@ -356,7 +364,7 @@ int ext4_htree_store_dirent(struct file 
 	new_fn->inode = le32_to_cpu(dirent->inode);
 	new_fn->name_len = dirent->name_len;
 	new_fn->file_type = dirent->file_type;
-	memcpy(new_fn->name, dirent->name, dirent->name_len);
+	memcpy(new_fn->name, dirent->name, dirent->name_len + extra_data);
 	new_fn->name[dirent->name_len] = 0;
 
 	while (*p) {

@@ -417,7 +425,9 @@ static int call_filldir(struct file *fil
 		error = filldir(dirent, fname->name,
 				fname->name_len, curr_pos,
 				fname->inode,
-				get_dtype(sb, fname->file_type));
+				get_dtype(sb, fname->file_type)|
+				(fname->file_type &
+				 EXT4_DIRENT_LUFID));
 		if (error) {
 			filp->f_pos = curr_pos;
 			info->extra_fname = fname;

Index: b/fs/ext4/ext4.h
===================================================================
@@ -1061,6 +1061,7 @@ static inline int ext4_valid_inum(struct
 #define EXT4_FEATURE_INCOMPAT_64BIT		0x0080
 #define EXT4_FEATURE_INCOMPAT_MMP               0x0100
 #define EXT4_FEATURE_INCOMPAT_FLEX_BG		0x0200
+#define EXT4_FEATURE_INCOMPAT_DIRDATA           0x1000
 
 #define EXT4_FEATURE_COMPAT_SUPP	EXT2_FEATURE_COMPAT_EXT_ATTR
 #define EXT4_FEATURE_INCOMPAT_SUPP	(EXT4_FEATURE_INCOMPAT_FILETYPE| \

@@ -1068,7 +1069,8 @@ static inline int ext4_valid_inum(struct
 					 EXT4_FEATURE_INCOMPAT_META_BG| \
 					 EXT4_FEATURE_INCOMPAT_EXTENTS| \
 					 EXT4_FEATURE_INCOMPAT_64BIT| \
-					 EXT4_FEATURE_INCOMPAT_FLEX_BG)
+					 EXT4_FEATURE_INCOMPAT_FLEX_BG| \
+					 EXT4_FEATURE_INCOMPAT_DIRDATA)
 #define EXT4_FEATURE_RO_COMPAT_SUPP	(EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \
 					 EXT4_FEATURE_RO_COMPAT_LARGE_FILE| \
 					 EXT4_FEATURE_RO_COMPAT_GDT_CSUM| \

@@ -1150,6 +1152,25 @@ struct ext4_dir_entry_2 {
 #define EXT4_FT_SYMLINK		7
 
 #define EXT4_FT_MAX		8
+#define EXT4_FT_MASK	        0xf
+
+
+#if EXT4_FT_MAX > EXT4_FT_MASK
+#error "conflicting EXT4_FT_MAX and EXT4_FT_MASK"
+#endif
+
+/*
+ * d_type has 4 unused bits, so it can hold four types data. these different
+ * type of data (e.g. lustre data, high 32 bits of 64-bit inode number) can be
+ * stored, in flag order, after file-name in ext4 dirent.
+*/
+/*
+ * this flag is added to d_type if ext4 dirent has extra data after
+ * filename. this data length is variable and length is stored in first byte
+ * of data. data start after filename NUL byte.
+ * This is used by Lustre FS.
+  */
+#define EXT4_DIRENT_LUFID               0x10
 
 /*
  * EXT4_DIR_PAD defines the directory entries boundaries

@@ -1158,8 +1179,11 @@ struct ext4_dir_entry_2 {
  */
 #define EXT4_DIR_PAD			4
 #define EXT4_DIR_ROUND			(EXT4_DIR_PAD - 1)
-#define EXT4_DIR_REC_LEN(name_len)	(((name_len) + 8 + EXT4_DIR_ROUND) & \
+#define __EXT4_DIR_REC_LEN(name_len)	(((name_len) + 8 + EXT4_DIR_ROUND) & \
 					 ~EXT4_DIR_ROUND)
+#define EXT4_DIR_REC_LEN(de)            (__EXT4_DIR_REC_LEN(de->name_len +\
+					ext4_get_dirent_data_len(de)))
+
 #define EXT4_MAX_REC_LEN		((1<<16)-1)
 
 /*

@@ -1678,6 +1702,17 @@ static inline void set_bitmap_uptodate(s
 	set_bit(BH_BITMAP_UPTODATE, &(bh)->b_state);
 }
 
+static inline int ext4_get_dirent_data_len(struct ext4_dir_entry_2 *de)
+{
+	int dlen = 0;
+	char *data;
+	if (de->file_type & EXT4_DIRENT_LUFID) {
+		data = de->name + de->name_len + 1;
+		dlen = *data + 1;
+	}
+	return dlen;
+}
+
 #endif	/* __KERNEL__ */
 
 #endif	/* _EXT4_H */

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