Re: [PATCH 6/6] fs: add CONFIG_BUFFER_HEAD

[Hannes Reinecke]

On 7/20/23 16:04, Christoph Hellwig wrote:
> Add a new config option that controls building the buffer_head code, and
> select it from all file systems and stacking drivers that need it.
>
> For the block device nodes and alternative iomap based buffered I/O path
> is provided when buffer_head support is not enabled, and iomap needs a
> little tweak to be able to compile out the buffer_head based code path.
>
> Otherwise this is just Kconfig and ifdef changes.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
>   block/fops.c                 | 71 +++++++++++++++++++++++++++++++-----
>   drivers/md/Kconfig           |  1 +
>   fs/Kconfig                   |  4 ++
>   fs/Makefile                  |  2 +-
>   fs/adfs/Kconfig              |  1 +
>   fs/affs/Kconfig              |  1 +
>   fs/befs/Kconfig              |  1 +
>   fs/bfs/Kconfig               |  1 +
>   fs/efs/Kconfig               |  1 +
>   fs/exfat/Kconfig             |  1 +
>   fs/ext2/Kconfig              |  1 +
>   fs/ext4/Kconfig              |  1 +
>   fs/f2fs/Kconfig              |  1 +
>   fs/fat/Kconfig               |  1 +
>   fs/freevxfs/Kconfig          |  1 +
>   fs/gfs2/Kconfig              |  1 +
>   fs/hfs/Kconfig               |  1 +
>   fs/hfsplus/Kconfig           |  1 +
>   fs/hpfs/Kconfig              |  1 +
>   fs/iomap/buffered-io.c       | 12 ++++--
>   fs/isofs/Kconfig             |  1 +
>   fs/jfs/Kconfig               |  1 +
>   fs/minix/Kconfig             |  1 +
>   fs/nilfs2/Kconfig            |  1 +
>   fs/ntfs/Kconfig              |  1 +
>   fs/ntfs3/Kconfig             |  1 +
>   fs/ocfs2/Kconfig             |  1 +
>   fs/omfs/Kconfig              |  1 +
>   fs/qnx4/Kconfig              |  1 +
>   fs/qnx6/Kconfig              |  1 +
>   fs/reiserfs/Kconfig          |  1 +
>   fs/sysv/Kconfig              |  1 +
>   fs/udf/Kconfig               |  1 +
>   fs/ufs/Kconfig               |  1 +
>   include/linux/buffer_head.h  | 32 ++++++++--------
>   include/trace/events/block.h |  2 +
>   mm/migrate.c                 |  4 +-
>   37 files changed, 125 insertions(+), 32 deletions(-)
Hmm.

I actually have a patchset which _does_ allow for large I/O blocksizes 
with buffer_heads. (And even ltp/fsx is happy on xfs...)

Can we modify this to not have a compile-time option but rather a 
setting somewhere? EG kernel option or flag in struct address_space?

Cheers,

Hannes
--
Dr. Hannes Reinecke                Kernel Storage Architect
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