+
+static int num_desc_blocks(struct super_block *sb, ext4_group_t groups)
+{
+ return (groups + EXT4_DESC_PER_BLOCK(sb) - 1) / EXT4_DESC_PER_BLOCK(sb);
+}
+
+/*
+ * Release the resize inode and drop the resize_inode feature if there
+ * are no more reserved gdt blocks, and then convert the file system
+ * to enable meta_bg
+ */
+static int ext4_convert_meta_bg(struct super_block *sb, struct inode *inode)
+{
+ handle_t *handle;
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct ext4_super_block *es = sbi->s_es;
+ struct ext4_inode_info *ei = 0;
+ ext4_fsblk_t nr;
+ int i, ret, err = 0;
+ int credits = 1;
+
+ ext4_msg(sb, KERN_INFO, "Converting file system to meta_bg");
+ if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RESIZE_INODE)) {
+ if (es->s_reserved_gdt_blocks) {
+ ext4_error(sb, "Unexpected non-zero "
+ "s_reserved_gdt_blocks");
+ return -EPERM;
+ }
+ if (!inode) {
+ ext4_error(sb, "Unexpected NULL resize_inode");
+ return -EPERM;
+ }
+ ei = EXT4_I(inode);
+
+ /* Do a quick sanity check of the resize inode */
+ if (inode->i_blocks != 1 << (inode->i_blkbits - 9))
+ goto invalid_resize_inode;
+ for (i = 0; i < EXT4_N_BLOCKS; i++) {
+ if (i == EXT4_DIND_BLOCK) {
+ if (ei->i_data[i])
+ continue;
+ else
+ goto invalid_resize_inode;
+ }
+ if (ei->i_data[i])
+ goto invalid_resize_inode;
+ }
+ credits += 3; /* block bitmap, bg descriptor, resize inode */
+ }
+
+ handle = ext4_journal_start_sb(sb, credits);
+ if (IS_ERR(handle))
+ return PTR_ERR(handle);
+
+ err = ext4_journal_get_write_access(handle, sbi->s_sbh);
+ if (err)
+ goto errout;
+
+ EXT4_CLEAR_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RESIZE_INODE);
+ EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG);
+ sbi->s_es->s_first_meta_bg =
+ cpu_to_le32(num_desc_blocks(sb, sbi->s_groups_count));
+
+ err = ext4_handle_dirty_super(handle, sb);
+ if (err) {
+ ext4_std_error(sb, err);
+ goto errout;
+ }
+
+ if (inode) {
+ nr = le32_to_cpu(ei->i_data[EXT4_DIND_BLOCK]);
+ ext4_free_blocks(handle, inode, NULL, nr, 1,
+ EXT4_FREE_BLOCKS_METADATA |
+ EXT4_FREE_BLOCKS_FORGET);
+ ei->i_data[EXT4_DIND_BLOCK] = 0;
+ inode->i_blocks = 0;
+
+ err = ext4_mark_inode_dirty(handle, inode);
+ if (err)
+ ext4_std_error(sb, err);
+ }
+
+errout:
+ ret = ext4_journal_stop(handle);
+ if (!err)
+ err = ret;
+ return ret;
+
+invalid_resize_inode:
+ ext4_error(sb, "corrupted/inconsistent resize inode");
+ return -EINVAL;
+}
+