From: Keith Busch <kbusch@kernel.org>
To: Carlos Maiolino <cem@kernel.org>
Cc: brauner@kernel.org, linux-block@vger.kernel.org
Subject: Re: [PATCH] iomap: enforce DIO alignment check in iomap]
Date: Wed, 10 Jun 2026 11:14:30 -0600 [thread overview]
Message-ID: <aimbdmqC10uXrZuo@kbusch-mbp> (raw)
In-Reply-To: <aimGzU_UY3jV-ece@nidhogg.toxiclabs.cc>
On Wed, Jun 10, 2026 at 06:58:13PM +0200, Carlos Maiolino wrote:
> On Wed, Jun 10, 2026 at 09:37:17AM -0600, Keith Busch wrote:
> > On Wed, Jun 10, 2026 at 05:27:42PM +0200, Carlos Maiolino wrote:
> > > The DIO alignment check has been lifted from iomap layer to rely on the
> > > block layer to enforce proper alignment when issuing direct IO
> > > operations. This though, depending on the IO size and buffer address
> > > passed to the IO operation may lead to user-visible behavior change.
> > >
> > > This has been caught initially by LTP test diotest4 running on
> > > PPC architecture, where the test fails because a read() operation
> > > with a supposedly misaligned buffer succeeds instead of an expected
> > > -EINVAL.
> >
> > It's not supposed to matter where in the stack we determined this be an
> > invalid request: it should still fail if it's misaligned. Could you
> > clarify how this is succeeding?
>
> Fair enough, can you point me to where the alignment is supposed to be
> checked?
https://elixir.bootlin.com/linux/v7.1-rc7/source/block/blk-merge.c#L352
It does require that someone calls the bio split-to-limits routine,
which I had taken for granted as a given, but I realize that some
drivers don't do that. What block device are you using for your test?
next prev parent reply other threads:[~2026-06-10 17:14 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-10 15:27 [PATCH] iomap: enforce DIO alignment check in iomap] Carlos Maiolino
2026-06-10 15:37 ` Keith Busch
2026-06-10 16:58 ` Carlos Maiolino
2026-06-10 17:14 ` Keith Busch [this message]
2026-06-10 18:19 ` Carlos Maiolino
2026-06-10 19:54 ` Keith Busch
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