| From: |
| Christoph Hellwig <hch-AT-lst.de> |
| To: |
| Jens Axboe <axboe-AT-kernel.dk> |
| Subject: |
| allow building a kernel without buffer_heads |
| Date: |
| Thu, 20 Jul 2023 16:04:46 +0200 |
| Message-ID: |
| <20230720140452.63817-1-hch@lst.de> |
| Cc: |
| "Darrick J. Wong" <djwong-AT-kernel.org>, Andrew Morton <akpm-AT-linux-foundation.org>, Matthew Wilcox <willy-AT-infradead.org>, Christian Brauner <christian-AT-brauner.io>, linux-block-AT-vger.kernel.org, linux-fsdevel-AT-vger.kernel.org, linux-xfs-AT-vger.kernel.org, linux-mm-AT-kvack.org, linux-kernel-AT-vger.kernel.org |
| Archive-link: |
| Article |
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
