I/O issues with writing to mtdblock devices on kirkwood

[Andrew Lunn]

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