Re: git: 2612f1b8649b - main - deadfs: Return ENXIO instead of EIO when the device is gone.

From: Konstantin Belousov <kostikbel_at_gmail.com>
Date: Fri, 24 Oct 2025 10:36:19 UTC 
On Fri, Oct 24, 2025 at 10:12:30AM +0000, Poul-Henning Kamp wrote:
> --------
> Konstantin Belousov writes:
> 
> > On Fri, Oct 24, 2025 at 07:41:11AM +0000, Poul-Henning Kamp wrote:
> 
> > >     Something changed recently, and while testing this fix, I noticed
> > Nothing changed WRT code, it is just a race that causes the behavior.
> 
> That is why I wrote "something", because I agree that it is not code
> in our tree which has changed.
> 
> > >     that drm-kmod-66/i915kms may be the condition which trigger
> > >     the different code-path.
> 
> It worries me if loading drm-kmod-66/i915kms can cause this kind
> of change of behaviour.
> 
> Even with the fix, I see 2-4 read(2) operations return EIO before
> the ENXIO manifests.
> 
> The only hypothesis I have, is that something in DRM-world hogs
> some kind of HW resource, but I do not have time (nor drm-skillz)
> to look into that this morning, and I wanted to get the ENXIO fix
> in for RELENG-15 purposes[1].

I do not think that DRM really affects the code path for io.
I see several EIOs in CAM, in particular scsi_da.c, but I do not
know CAM/USB/umass stack to track that down by reading.