apfs: implement creation of free queue nodes

Extend apfs_create_node() to support the creation of free queue nodes.
Define and use apfs_cpoint_data_allocate() to allocate the blocks in the
checkpoint data area, and apfs_create_cpoint_map() to register them in
the checkpoint-mapping block.  In the future I would like to simplify
apfs_create_node() with functions such as "apfs_create_ephemeral_object"
and "apfs_create_virtual_object" that took care of this stuff.

The module will now be able to perform far more writes before getting
an error, which will simplify testing.  We still need to put a limit to
the size of the free queue tree, and actually free the blocks in the
bitmap.

Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>

fs/apfs/node.c

@@ -186,8 +186,19 @@ static struct apfs_node *apfs_create_node(struct super_block *sb, u32 storage)
 
 		subtype = APFS_OBJECT_TYPE_FSTREE;
 		break;
+	case APFS_OBJ_EPHEMERAL:
+		apfs_cpoint_data_allocate(sb, &bno);
+		oid = le64_to_cpu(msb_raw->nx_next_oid);
+		le64_add_cpu(&msb_raw->nx_next_oid, 1);
+
+		err = apfs_create_cpoint_map(sb, oid, bno);
+		if (err)
+			return ERR_PTR(err);
+
+		subtype = APFS_OBJECT_TYPE_SPACEMAN_FREE_QUEUE;
+		break;
 	default:
-		/* TODO: physical and ephemeral nodes */
+		/* TODO: physical nodes */
 		return ERR_PTR(-EOPNOTSUPP);
 	}
 

fs/apfs/object.c

@@ -92,6 +92,64 @@ static int apfs_cpm_lookup_oid(struct super_block *sb,
 	return -EAGAIN; /* The mapping may still be in the next block */
 }
 
+/**
+ * apfs_create_cpoint_map - Create a checkpoint mapping
+ * @sb:		filesystem superblock
+ * @oid:	ephemeral object id
+ * @bno:	block number
+ *
+ * Only mappings for free queue nodes are supported for now.  Returns 0 on
+ * success or a negative error code in case of failure.
+ */
+int apfs_create_cpoint_map(struct super_block *sb, u64 oid, u64 bno)
+{
+	struct apfs_sb_info *sbi = APFS_SB(sb);
+	struct apfs_nx_superblock *raw_sb = sbi->s_msb_raw;
+	u64 desc_base = le64_to_cpu(raw_sb->nx_xp_desc_base);
+	u32 desc_index = le32_to_cpu(raw_sb->nx_xp_desc_index);
+	u32 desc_blks = le32_to_cpu(raw_sb->nx_xp_desc_blocks);
+	u32 desc_len = le32_to_cpu(raw_sb->nx_xp_desc_len);
+	struct buffer_head *bh;
+	struct apfs_checkpoint_map_phys *cpm;
+	struct apfs_checkpoint_mapping *map;
+	u64 cpm_bno;
+	u32 cpm_count;
+	int err = 0;
+
+	if (!desc_blks || desc_len < 2)
+		return -EFSCORRUPTED;
+
+	/* Last block in area is superblock; we want the last mapping block */
+	cpm_bno = desc_base + (desc_index + desc_len - 2) % desc_blks;
+	bh = sb_bread(sb, cpm_bno);
+	if (!bh)
+		return -EIO;
+	cpm = (struct apfs_checkpoint_map_phys *)bh->b_data;
+	ASSERT(sbi->s_xid == le64_to_cpu(cpm->cpm_o.o_xid));
+
+	cpm_count = le32_to_cpu(cpm->cpm_count);
+	if (cpm_count >= apfs_max_maps_per_block(sb)) { /* TODO */
+		apfs_warn(sb, "creation of cpm blocks not yet supported");
+		err = -ENOSPC;
+		goto fail;
+	}
+	map = &cpm->cpm_map[cpm_count];
+	le32_add_cpu(&cpm->cpm_count, 1);
+
+	map->cpm_type = cpu_to_le32(APFS_OBJ_EPHEMERAL |
+				    APFS_OBJECT_TYPE_BTREE_NODE);
+	map->cpm_subtype = cpu_to_le32(APFS_OBJECT_TYPE_SPACEMAN_FREE_QUEUE);
+	map->cpm_size = cpu_to_le32(sb->s_blocksize);
+	map->cpm_pad = 0;
+	map->cpm_fs_oid = 0;
+	map->cpm_oid = cpu_to_le64(oid);
+	map->cpm_paddr = cpu_to_le64(bno);
+
+fail:
+	brelse(bh);
+	return err;
+}
+
 /**
  * apfs_read_ephemeral_object - Find and map an ephemeral object
  * @sb:		superblock structure

fs/apfs/object.h

@@ -91,6 +91,7 @@ extern int apfs_obj_verify_csum(struct super_block *sb,
 				struct apfs_obj_phys *obj);
 extern void apfs_obj_set_csum(struct super_block *sb,
 			      struct apfs_obj_phys *obj);
+extern int apfs_create_cpoint_map(struct super_block *sb, u64 oid, u64 bno);
 extern struct buffer_head *apfs_read_ephemeral_object(struct super_block *sb,
 						      u64 oid);
 extern struct buffer_head *apfs_read_object_block(struct super_block *sb,

fs/apfs/transaction.c

@@ -236,6 +236,29 @@ static int apfs_update_mapping_blocks(struct super_block *sb)
 	return 0;
 }
 
+/**
+ * apfs_cpoint_data_allocate - Allocate a new block in the checkpoint data area
+ * @sb:		superblock structure
+ * @bno:	on return, the allocated block number
+ */
+void apfs_cpoint_data_allocate(struct super_block *sb, u64 *bno)
+{
+	struct apfs_sb_info *sbi = APFS_SB(sb);
+	struct apfs_nx_superblock *raw_sb = sbi->s_msb_raw;
+	u64 data_base = le64_to_cpu(raw_sb->nx_xp_data_base);
+	u32 data_next = le32_to_cpu(raw_sb->nx_xp_data_next);
+	u32 data_blks = le32_to_cpu(raw_sb->nx_xp_data_blocks);
+	u32 data_len = le32_to_cpu(raw_sb->nx_xp_data_len);
+
+	*bno = data_base + data_next;
+	data_next = (data_next + 1) % data_blks;
+	data_len++;
+
+	ASSERT(sbi->s_xid == le64_to_cpu(raw_sb->nx_o.o_xid));
+	raw_sb->nx_xp_data_next = cpu_to_le32(data_next);
+	raw_sb->nx_xp_data_len = cpu_to_le32(data_len);
+}
+
 /**
  * apfs_checkpoint_start - Start the checkpoint for a new transaction
  * @sb:		superblock structure

fs/apfs/transaction.h

@@ -39,6 +39,7 @@ struct apfs_bh_info {
 	struct list_head	list;	/* List of buffers in the transaction */
 };
 
+extern void apfs_cpoint_data_allocate(struct super_block *sb, u64 *bno);
 extern int apfs_transaction_start(struct super_block *sb);
 extern int apfs_transaction_commit(struct super_block *sb);
 extern int apfs_transaction_join(struct super_block *sb,