Re: [PATCH 1/2] file-posix: fix Linux alignment probing when EIO is returned

[Eric Biggers]

On Tue, Nov 01, 2022 at 03:00:30PM -0400, Stefan Hajnoczi wrote:
> Linux dm-crypt returns errno EIO from unaligned O_DIRECT pread(2) calls.

Citation needed.  For direct I/O to block devices, the kernel's block layer
checks the alignment before the I/O is actually submitted to the underlying
block device.  See
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/block/fops.c?h=v6.1-rc3#n306

> Buglink: https://gitlab.com/qemu-project/qemu/-/issues/1290

That "bug" seems to be based on a misunderstanding of the kernel source code,
and not any actual testing.

I just tested it, and the error code is EINVAL.

- Eric