Hi,

在 2025/8/20 00:49, Keith Busch 写道:

From: Keith Busch <kbusch@kernel.org>

Previous version:

   https://lore.kernel.org/linux-block/20250805141123.332298-1-kbusch@meta.com/ (local)

This series removes the direct io requirement that io vector lengths
align to the logical block size.

I tested this on a few raw block device types including nvme,
virtio-blk, ahci, and loop. NVMe is the only one I tested with 4k
logical sectors; everything else was 512.

On each of those, I tested several iomap filesystems: xfs, ext4, and
btrfs. I found it interesting that each behave a little
differently with handling invalid vector alignments:

   - XFS is the most straight forward and reports failures on invalid
     vector conditions, same as raw blocks devices.

   - EXT4 falls back to buffered io for writes but not for reads.

I found it in ext4 too, i tried to fall the misaligned dio read request 
back to buffered io and submitted a patch[1], but haven't received any 
comments yet.

[1]:https://lore.kernel.org/all/20250710085910.123168-1-chensong_2000@189.cn/ (local)

Song

   - BTRFS doesn't even try direct io for any unusual alignments; it
     chooses buffered io from the start.

So it has been a little slow going figuring out which results to expect
from various tests, but I think I've got all the corner cases covered. I
can submit the tests cases to blktests and fstests for consideration
separately, too.

I'm not 100% sure where we're at with the last patch. I think Mike
initially indicated this was okay to remove, but I could swear I read
something saying that might not be the case anymore. I just can't find
the message now. Mike?

Changes from v2:

   Include vector lengths when validating a split. The length check is
   only valid for r/w commands, and skipped for passthrough
   DRV_IN/DRV_OUT commands.

   Introduce a prep patch having bio_iov_iter_get_pages() take the
   caller's desired length alignment.

   Additional code comments explaing less obvious error conditions.

   Added reviews on the patches that haven't changed.

Keith Busch (8):
   block: check for valid bio while splitting
   block: add size alignment to bio_iov_iter_get_pages
   block: align the bio after building it
   block: simplify direct io validity check
   iomap: simplify direct io validity check
   block: remove bdev_iter_is_aligned
   blk-integrity: use simpler alignment check
   iov_iter: remove iov_iter_is_aligned

  block/bio-integrity.c  |  4 +-
  block/bio.c            | 64 ++++++++++++++++++----------
  block/blk-map.c        |  2 +-
  block/blk-merge.c      | 20 +++++++--
  block/fops.c           | 13 +++---
  fs/iomap/direct-io.c   |  6 +--
  include/linux/bio.h    | 13 ++++--
  include/linux/blkdev.h | 20 +++++----
  include/linux/uio.h    |  2 -
  lib/iov_iter.c         | 95 ------------------------------------------
  10 files changed, 94 insertions(+), 145 deletions(-)