linux-kernel - Re: [PATCH 0/7] direct-io: even more flexible io vectors

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Message-ID: <43716438-2fb9-4377-a4a0-6f803d7b8aec@kernel.dk>
Date: Sat, 2 Aug 2025 09:37:32 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Keith Busch <kbusch@...a.com>, linux-block@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: snitzer@...nel.org, dw@...idwei.uk, brauner@...nel.org,
 Keith Busch <kbusch@...nel.org>
Subject: Re: [PATCH 0/7] direct-io: even more flexible io vectors

On 8/1/25 5:47 PM, Keith Busch wrote:
> From: Keith Busch <kbusch@...nel.org>
> 
> In furthering direct IO use from user space buffers without bouncing to
> align to unnecessary kernel software constraints, this series removes
> the requirement that io vector lengths align to the logical block size.
> The downside (if want to call it that) is that mis-aligned io vectors
> are caught further down the block stack rather than closer to the
> syscall.

That's not a downside imho, it's much nicer to have the correct/expected
case be fast, and catch the unexpected error case down the line when we
have to iterate the vecs anyway.

IOW, I love this patchset. I'll spend some time going over the details.
Did you write some test cases for this?

> This change also removes one walking of the io vector, so that's nice
> too.
> 
> Keith Busch (7):
>   block: check for valid bio while splitting
>   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            | 58 +++++++++++++++++---------
>  block/blk-merge.c      |  5 +++
>  block/fops.c           |  4 +-
>  fs/iomap/direct-io.c   |  3 +-
>  include/linux/blkdev.h |  7 ----
>  include/linux/uio.h    |  2 -
>  lib/iov_iter.c         | 95 ------------------------------------------
>  8 files changed, 49 insertions(+), 129 deletions(-)

Now that's a beautiful diffstat.

-- 
Jens Axboe