Re: refactor the iomap writeback code v2

[Andrew Price <anprice@redhat.com>]

On 17/06/2025 11:54, Christoph Hellwig wrote:
> Hi all,
> 
> this is an alternative approach to the writeback part of the
> "fuse: use iomap for buffered writes + writeback" series from Joanne.
> It doesn't try to make the code build without CONFIG_BLOCK yet.
> 
> The big difference compared to Joanne's version is that I hope the
> split between the generic and ioend/bio based writeback code is a bit
> cleaner here.  We have two methods that define the split between the
> generic writeback code, and the implemementation of it, and all knowledge
> of ioends and bios now sits below that layer.
> 
> This version passes basic testing on xfs, and gets as far as mainline
> for gfs2 (crashes in generic/361).

I can't get generic/361 to crash per se, but it does fail as it detects the new warning about the missing ->migrate_folio for the gfs2_{rgrp,meta}_aops, which I'm looking at now.

If you have different results to this, please let me know more about the crash and your test environment.

Thanks,
Andy

> 
> Changes since v1:
>   - fix iomap reuse in block/zonefs/gfs2
>   - catch too large return value from ->writeback_range
>   - mention the correct file name in a commit log
>   - add patches for folio laundering
>   - add patches for read/modify write in the generic write helpers
> 
> Diffstat:
>   Documentation/filesystems/iomap/design.rst     |    3
>   Documentation/filesystems/iomap/operations.rst |   51 --
>   block/fops.c                                   |   37 +-
>   fs/gfs2/aops.c                                 |    8
>   fs/gfs2/bmap.c                                 |   48 +-
>   fs/gfs2/bmap.h                                 |    1
>   fs/gfs2/file.c                                 |    3
>   fs/iomap/buffered-io.c                         |  438 ++++++-------------------
>   fs/iomap/internal.h                            |    1
>   fs/iomap/ioend.c                               |  220 ++++++++++++
>   fs/iomap/trace.h                               |    2
>   fs/xfs/xfs_aops.c                              |  238 +++++++------
>   fs/xfs/xfs_file.c                              |    6
>   fs/xfs/xfs_iomap.c                             |   12
>   fs/xfs/xfs_iomap.h                             |    1
>   fs/xfs/xfs_reflink.c                           |    3
>   fs/zonefs/file.c                               |   40 +-
>   include/linux/iomap.h                          |   81 ++--
>   18 files changed, 630 insertions(+), 563 deletions(-)
>