+#if CONFIG_META_CSUM_ENABLE
+static uint32_t
+ext4_dir_dx_checksum(struct ext4_inode_ref *inode_ref,
+ void *dirent,
+ int count_offset, int count, struct ext4_directory_dx_tail *t)
+{
+ uint32_t orig_checksum, checksum = 0;
+ struct ext4_sblock *sb = &inode_ref->fs->sb;
+ int size;
+
+ /* Compute the checksum only if the filesystem supports it */
+ if (ext4_sb_feature_ro_com(sb, EXT4_FRO_COM_METADATA_CSUM)) {
+ uint32_t ino_index = to_le32(inode_ref->index);
+ uint32_t ino_gen =
+ to_le32(ext4_inode_get_generation(inode_ref->inode));
+
+ size = count_offset +
+ (count * sizeof(struct ext4_directory_dx_tail));
+ orig_checksum = t->checksum;
+ t->checksum = 0;
+ /* First calculate crc32 checksum against fs uuid */
+ checksum = ext4_crc32c(EXT4_CRC32_INIT, sb->uuid,
+ sizeof(sb->uuid));
+ /* Then calculate crc32 checksum against inode number
+ * and inode generation */
+ checksum = ext4_crc32c(checksum, &ino_index,
+ sizeof(ino_index));
+ checksum = ext4_crc32c(checksum, &ino_gen,
+ sizeof(ino_gen));
+ /* After that calculate crc32 checksum against all the dx_entry */
+ checksum = ext4_crc32c(checksum, dirent, size);
+ /* Finally calculate crc32 checksum for dx_tail */
+ checksum = ext4_crc32c(checksum, t,
+ sizeof(struct ext4_directory_dx_tail));
+ t->checksum = orig_checksum;
+ }
+ return checksum;
+}
+
+static struct ext4_directory_dx_countlimit *
+ext4_dir_dx_get_countlimit(struct ext4_inode_ref *inode_ref,
+ struct ext4_directory_entry_ll *dirent,
+ int *offset)
+{
+ struct ext4_directory_entry_ll *dp;
+ struct ext4_directory_dx_root *root;
+ struct ext4_sblock *sb = &inode_ref->fs->sb;
+ int count_offset;
+
+ if (ext4_dir_entry_ll_get_entry_length(dirent) ==
+ ext4_sb_get_block_size(sb))
+ count_offset = 8;
+ else if (ext4_dir_entry_ll_get_entry_length(dirent) == 12) {
+ root = (struct ext4_directory_dx_root *)dirent;
+ dp = (struct ext4_directory_entry_ll *)&root->dots[1];
+ if (ext4_dir_entry_ll_get_entry_length(dp) !=
+ ext4_sb_get_block_size(sb) - 12)
+ return NULL;
+ if (root->info.reserved_zero ||
+ root->info.info_length != sizeof(struct ext4_directory_dx_root_info))
+ return NULL;
+ count_offset = 32;
+ } else
+ return NULL;
+
+ if (offset)
+ *offset = count_offset;
+ return (struct ext4_directory_dx_countlimit *)(((char *)dirent) + count_offset);
+}
+
+/*
+ * BIG FAT NOTES:
+ * Currently we do not verify the checksum of HTree node.
+ */
+static bool
+ext4_dir_dx_checksum_verify(struct ext4_inode_ref *inode_ref,
+ struct ext4_directory_entry_ll *dirent)
+{
+ struct ext4_sblock *sb = &inode_ref->fs->sb;
+ int count_offset, limit, count;
+
+ if (ext4_sb_feature_ro_com(sb, EXT4_FRO_COM_METADATA_CSUM)) {
+ struct ext4_directory_dx_countlimit *countlimit =
+ ext4_dir_dx_get_countlimit(inode_ref, dirent, &count_offset);
+ if (!countlimit) {
+ /* Directory seems corrupted. */
+ return true;
+ }
+ struct ext4_directory_dx_tail *t;
+ limit = ext4_dir_dx_countlimit_get_limit(countlimit);
+ count = ext4_dir_dx_countlimit_get_count(countlimit);
+ if (count_offset + (limit * sizeof(struct ext4_directory_dx_entry)) >
+ ext4_sb_get_block_size(sb) -
+ sizeof(struct ext4_directory_dx_tail)) {
+ /* There is no space to hold the checksum */
+ return true;
+ }
+ t = (struct ext4_directory_dx_tail *)
+ (((struct ext4_directory_dx_entry *)countlimit) + limit);
+
+ if (t->checksum != to_le32(ext4_dir_dx_checksum(inode_ref,
+ dirent,
+ count_offset,
+ count, t)))
+ return false;
+ }
+ return true;
+}
+
+
+static void
+ext4_dir_set_dx_checksum(struct ext4_inode_ref *inode_ref,
+ struct ext4_directory_entry_ll *dirent)
+{
+ int count_offset, limit, count;
+ struct ext4_sblock *sb = &inode_ref->fs->sb;
+
+ if (ext4_sb_feature_ro_com(sb, EXT4_FRO_COM_METADATA_CSUM)) {
+ struct ext4_directory_dx_countlimit *countlimit =
+ ext4_dir_dx_get_countlimit(inode_ref, dirent, &count_offset);
+ if (!countlimit) {
+ /* Directory seems corrupted. */
+ return;
+ }
+ struct ext4_directory_dx_tail *t;
+ limit = ext4_dir_dx_countlimit_get_limit(countlimit);
+ count = ext4_dir_dx_countlimit_get_count(countlimit);
+ if (count_offset + (limit * sizeof(struct ext4_directory_dx_entry)) >
+ ext4_sb_get_block_size(sb) -
+ sizeof(struct ext4_directory_dx_tail)) {
+ /* There is no space to hold the checksum */
+ return;
+ }
+ t = (struct ext4_directory_dx_tail *)
+ (((struct ext4_directory_dx_entry *)countlimit) + limit);
+
+ t->checksum =
+ to_le32(ext4_dir_dx_checksum(inode_ref, dirent, count_offset, count, t));
+ }
+}
+#else
+#define ext4_dir_dx_checksum_verify(...) true
+#define ext4_dir_set_dx_checksum(...)
+#endif
+