nilfs2: add checkpoint tree to nilfs object
To hold multiple versions of a filesystem in one sb instance, a new
on-memory structure is necessary to handle one or more checkpoints.
This adds a red-black tree of checkpoints to nilfs object, and adds
lookup and create functions for them.
Each checkpoint is represented by "nilfs_root" structure, and this
structure has rb_node to configure the rb-tree.
The nilfs_root object is identified with a checkpoint number. For
each snapshot, a nilfs_root object is allocated and the checkpoint
number of snapshot is assigned to it. For a regular mount
(i.e. current mode mount), NILFS_CPTREE_CURRENT_CNO constant is
assigned to the corresponding nilfs_root object.
Each nilfs_root object has an ifile inode and some counters. These
items will displace those of nilfs_sb_info structure in successive
patches.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
2 files changed
