This adds specific functions to manage NAT pages, a cache for NAT entries, free
nids, direct/indirect node blocks for indexing data, and address space for node
pages.
- The key information of an NAT entry consists of a node id and a block address.
- An NAT page is composed of block addresses covered by a certain range of NAT
entries, which is maintained by the address space of meta_inode.
- A radix tree structure is used to cache NAT entries. The index for the tree
is a node id.
- When there is no free nid, F2FS should scan NAT entries to find new one. In
order to avoid scanning frequently, F2FS manages a list containing a number of
free nids in memory. Only when free nids in the list are exhausted, scanning
process, build_free_nids(), is triggered.
- F2FS has direct and indirect node blocks for indexing data. This patch adds
fuctions related to the node block management such as getting, allocating, and
truncating node blocks to index data.
- In order to cache node blocks in memory, F2FS has a node_inode with an address
space for node pages. This patch also adds the address space operations for
node_inode.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
