I/O issues with writing to mtdblock devices on kirkwood

[Andrew Lunn]

On Sun, Oct 11, 2015 at 04:37:52PM +0200, JM wrote:
> On Sat, Sep 5, 2015 at 11:08 PM, Andrew Lunn <andrew at lunn.ch> wrote:
> > On Fri, Aug 21, 2015 at 01:24:17PM +0100, Ian Campbell wrote:
> >> Hi kirkwood-upstream,
> >>
> >> We (Debian) have had a couple of reports of I/O errors running Debian
> >> on kirkwood, specifically it seems to relate to later kernels (e.g.
> >> 4.0+) and I _suspect_ (without proof) that it may be due to the switch
> >> from board files to the DTS based kernel, or some change implied by
> >> this (e.g. different SATA driver now or timeouts have changed
> >> perhaps?).
> >
> > Hi Ian
> >
> > I've not reproduced this exactly, but something similar.
> >
> > I do a find / and in parallel a cat /dev/mtdblock3 > /dev/null
> >
> > While the cat is active, the find grinds to a halt. I don't get any
> > SATA timeouts, but that could be because /dev/mtdblock3 is small
> > enough that the timers don't expire.
> >
> > So i will now try to track down if there is a lock getting contended,
> > or at least why only the cat process makes progress.
> >
> >    Andrew
> 
> Is there any update on this? The bug persists with kernel 4.2.1

Sorry, not had time to look.

Do you have any idea when the issue started? My QNAP box got device
tree support somewhere around 3.5. So i would be tempted to see if
that has the issue, and then git bisect from there. Could you do the
same with you hardware?

     Andrew