[PATCH v2 00/16] fuse: use iomap for buffered writes + writeback

[Joanne Koong <joannelkoong@gmail.com>]

This series adds fuse iomap support for buffered writes and dirty folio
writeback. This is needed so that granular uptodate and dirty tracking can
be used in fuse when large folios are enabled. This has two big advantages.
Now for writes, instead of the entire folio needing to be read into the page
cache, only the relevant portions need to be. Now for writeback, only the
dirty portions need to be written back instead of the entire folio.

This patchset does 3 things, in order of sequence:
a) Decouple iomap/buffered-io.c code from the CONFIG_BLOCK dependency, as some
environments that run fuse may not have CONFIG_BLOCK set
b) Add support to iomap buffered io for generic write and writeback that is
not dependent on bios
c) Add fuse integration with iomap

Patches 3 and 5 are obviated by the refactoring done later on in patches 10
and 11 but I left this patchset in this order in the hopes of making it
more logically easier to follow.

This series was run through fstests with large folios enabled and through
some quick sanity checks on passthrough_hp with a) writing 1 GB in 1 MB chunks
and then going back and dirtying a few bytes in each chunk and b) writing 50
MB in 1 MB chunks and going through dirtying the entire chunk for several runs.
a) showed about a 40% speedup increase with iomap support added and b) showed
roughly the same performance.

This patchset does not enable large folios yet. That will be sent out in a
separate future patchset.

This series is on top of commit 27605c8c0 ("Merge tag 'net-6.16-rc2'...") in
the linux tree.


Thanks,
Joanne


Changeset
-------
v1 -> v2:
* Drop IOMAP_IN_MEM type and just use IOMAP_MAPPED for fuse
* Separate out new helper functions added to iomap into separate commits
* Update iomap documentation
* Clean up iomap_writeback_dirty_folio() locking logic w/ christoph's
  recommendation 
* Refactor ->map_blocks() to generic ->writeback_folio()
* Refactor ->submit_ioend() to generic ->writeback_complete()
* Add patch for changing 'count' to 'async_writeback'
* Rebase commits onto linux branch instead of fuse branch
v1: https://lore.kernel.org/linux-fsdevel/20250606233803.1421259-1-joannelkoong@gmail.com/


Joanne Koong (16):
  iomap: move buffered io CONFIG_BLOCK dependent logic into separate
    file
  iomap: iomap_read_folio_sync() -> iomap_bio_read_folio_sync()
  iomap: iomap_add_to_ioend() -> iomap_bio_add_to_ioend()
  iomap: add wrapper function iomap_bio_readpage()
  iomap: add wrapper function iomap_bio_ioend_error()
  iomap: add wrapper function iomap_submit_bio()
  iomap: decouple buffered-io.o from CONFIG_BLOCK
  iomap: add read_folio_sync() handler for buffered writes
  iomap: change 'count' to 'async_writeback'
  iomap: replace ->map_blocks() with generic ->writeback_folio() for
    writeback
  iomap: replace ->submit_ioend() with generic ->writeback_complete()
    for writeback
  iomap: support more customized writeback handling
  iomap: add iomap_writeback_dirty_folio()
  fuse: use iomap for buffered writes
  fuse: use iomap for writeback
  fuse: use iomap for folio laundering

 .../filesystems/iomap/operations.rst          |  65 ++-
 block/fops.c                                  |   7 +-
 fs/fuse/Kconfig                               |   1 +
 fs/fuse/file.c                                | 308 +++++-------
 fs/gfs2/bmap.c                                |   7 +-
 fs/iomap/Makefile                             |   5 +-
 fs/iomap/buffered-io-bio.c                    | 365 ++++++++++++++
 fs/iomap/buffered-io.c                        | 471 +++---------------
 fs/iomap/internal.h                           |  40 ++
 fs/xfs/xfs_aops.c                             |  28 +-
 fs/zonefs/file.c                              |   7 +-
 include/linux/iomap.h                         |  88 +++-
 12 files changed, 775 insertions(+), 617 deletions(-)
 create mode 100644 fs/iomap/buffered-io-bio.c

-- 
2.47.1