Hi all, This series allows to build a kernel without buffer_heads, which I think is useful to show where the dependencies are, and maybe also for some very much limited environments, where people just needs xfs and/or btrfs and some of the read-only block based file systems. It first switches buffered writes (but not writeback) for block devices to use iomap unconditionally, but still using buffer_heads, and then adds a CONFIG_BUFFER_HEAD selected by all file systems that need it (which is most block based file systems), makes the buffer_head support in iomap optional, and adds an alternative implementation of the block device address_operations using iomap. This latter implementation will also be useful to support block size > PAGE_SIZE for block device nodes as buffer_heads won't work very well for that. Note that for now the md software raid drivers is also disabled as it has some (rather questionable) buffer_head usage in the unconditionally built bitmap code. I have a series pending to make the bitmap code conditional and deprecated it, but it hasn't been merged yet. Changes since v1: - drop the already merged prep patches - depend on FS_IOMAP not IOMAP - pick a better new name for block_page_mkwrite_return
