This patch introduces the core metadata block caching infrastructure to manage f2fs metadata independently of the page cache. It implements: - core cache APIs: get, create, put, drop, backed by a radix tree and a single global LRU list. - support multiple status of cached block: LOCKED, UPTODATE, DIRTY, WRITEBACK, INLINE. - internal bio based read/write helpers with adjacent block vector merging. Reviewed-by: Zhiguo Niu <zhiguo.niu@unisoc.com> Signed-off-by: Chao Yu <chao@kernel.org> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>