+__le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 block_group,
+ struct ext4_group_desc *gdp)
+{
+ __u16 crc = 0;
+
+ if (sbi->s_es->s_feature_ro_compat &
+ cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
+ int offset = offsetof(struct ext4_group_desc, bg_checksum);
+ __le32 le_group = cpu_to_le32(block_group);
+
+ crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
+ crc = crc16(crc, (__u8 *)&le_group, sizeof(le_group));
+ crc = crc16(crc, (__u8 *)gdp, offset);
+ offset += sizeof(gdp->bg_checksum); /* skip checksum */
+ /* for checksum of struct ext4_group_desc do the rest...*/
+ if ((sbi->s_es->s_feature_incompat &
+ cpu_to_le32(EXT4_FEATURE_INCOMPAT_64BIT)) &&
+ offset < le16_to_cpu(sbi->s_es->s_desc_size))
+ crc = crc16(crc, (__u8 *)gdp + offset,
+ le16_to_cpu(sbi->s_es->s_desc_size) -
+ offset);
+ }
+
+ return cpu_to_le16(crc);
+}
+
+int ext4_group_desc_csum_verify(struct ext4_sb_info *sbi, __u32 block_group,
+ struct ext4_group_desc *gdp)
+{
+ if ((sbi->s_es->s_feature_ro_compat &
+ cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) &&
+ (gdp->bg_checksum != ext4_group_desc_csum(sbi, block_group, gdp)))
+ return 0;
+
+ return 1;
+}
+