Merge patch series "fuse: use iomap for buffered reads + readahead"

Joanne Koong <joannelkoong@gmail.com> says:

This series adds fuse iomap support for buffered reads and readahead.
This is needed so that granular uptodate tracking can be used in fuse when
large folios are enabled so that only the non-uptodate portions of the folio
need to be read in instead of having to read in the entire folio. It also is
needed in order to turn on large folios for servers that use the writeback
cache since otherwise there is a race condition that may lead to data
corruption if there is a partial write, then a read and the read happens
before the write has undergone writeback, since otherwise the folio will not
be marked uptodate from the partial write so the read will read in the entire
folio from disk, which will overwrite the partial write.

This is on top of two locally-patched iomap patches [1] [2] patched on top of
commit f1c864be6e88 ("Merge branch 'vfs-6.18.async' into vfs.all") in
Christian's vfs.all tree.

This series was run through fstests on fuse passthrough_hp with an
out-of kernel patch enabling fuse large folios.

This patchset does not enable large folios on fuse yet. That will be part
of a different patchset.

* patches from https://lore.kernel.org/20250926002609.1302233-1-joannelkoong@gmail.com:
  fuse: remove fc->blkbits workaround for partial writes
  fuse: use iomap for readahead
  fuse: use iomap for read_folio
  iomap: make iomap_read_folio() a void return
  iomap: move buffered io bio logic into new file
  iomap: add caller-provided callbacks for read and readahead
  iomap: set accurate iter->pos when reading folio ranges
  iomap: track pending read bytes more optimally
  iomap: rename iomap_readpage_ctx struct to iomap_read_folio_ctx
  iomap: rename iomap_readpage_iter() to iomap_read_folio_iter()
  iomap: iterate over folio mapping in iomap_readpage_iter()
  iomap: store read/readahead bio generically
  iomap: move read/readahead bio submission logic into helper function
  iomap: move bio read logic into helper function

Signed-off-by: Christian Brauner <brauner@kernel.org>