Fwd: Dreamplug stable/10 usb - sd file transfer corruption error - cache related?

[Ian Lepore]

That old advice was based on bugs in old code that has been fixed.  I've
just been double-checking that the various fixes are in 10 (some of them
were things I submitted a PR for before I became a committer).  I'm not
sure about the usb driver, but there have been big changes in the dma
cache coherency code between 9 and 10, although much of that is the
fixes I was alluding to.

Basically what you're doing is a usb->usb copy, I'll see if I can
recreate the corruption on my dreamplug here the same way.

-- Ian

On Fri, 2013-10-25 at 14:38 -0700, Steven Lee wrote:
> ---------- Forwarded message ----------
> From: Steven Lee <ssl.qlt at gmail.com>
> Date: Fri, Oct 25, 2013 at 2:37 PM
> Subject: Re: Dreamplug stable/10 usb - sd file transfer corruption error -
> cache related?
> To: Ian Lepore <ian at freebsd.org>
> 
> 
> Ian, thanks for your reply.
> 
> I am using the DREAMPLUG-1001 stock kernel config, and you are right the
> internal sd card shows up as a usb device, /dev/da0.
> 
> As I mentioned, I tried modifying pmap.c as per one of your suggestions to
> an earlier poster / problem, but it didn't seem to help the issue.  I
> changed the pmap_pte_init_arm10() function to look like the
> pmap_pte_init_arm9() function.
> 
> Any other thoughts about things to try?  Since it seems like this is a
> regression between 9 and 10, are you aware of any specific cache related
> changes to the usb driver between the branches?
> 
> - Steve
> 
> 
> On Fri, Oct 25, 2013 at 2:03 PM, Ian Lepore <ian at freebsd.org> wrote:
> 
> > On Fri, 2013-10-25 at 13:37 -0700, Steven Lee wrote:
> > > Hello,
> > >
> > > In the process of upgrading my Dreamplug from the stable/9 branch to the
> > > stable/10 branch, I have run into a fairly
> > > significant file corruption problem.  The steps that create this problem
> > > are as follows:
> > >
> > > 1. Cross-compile the kernel and buildworld from the stable/10 branch on a
> > > separate host.
> > > 2. Install the kernel and installworld on a usb stick drive
> > > 3. Boot the Dreamplug from the usb drive
> > >
> > > There are no problems that show up to this point, the Dreamplug boots
> > with
> > > no errors.
> > >
> > > 4. Copy the kernel from the usb drive to the internal sd card
> > > 5. Copy the root filesystem from the usb drive to the internal sd card
> > > using (dump | restore)
> > >
> > > It is at step 5 that the error manifests itself, as I found that
> > > approximately 20 shell scripts in the /etc/rc.d directory
> > > had been randomly corrupted with strings of null characters (in groups of
> > > 32).  I assume that the rest of the file system
> > > was compromised in a similar fashion.  The bug is repeatable, however the
> > > corruption is somewhat random, so
> > > each time different files are corrupted in different places.
> > >
> > > When I followed the exact same steps from the stable/9 branch, the
> > problem
> > > did not occur, so there is clearly some
> > > type of regression error between the 9 and 10 branches.
> > >
> > > After searching through the arm mailing list, I attempted to work around
> > > the problem by:
> > > - mounting the file systems with -o noclusterr -o noclusterrw
> > > - mounting the file systems with -o sync
> > > - as per comments on bug arm/158950, attempted to modify the pmap.c
> > > functions to change the cache from
> > > write-back mode to write-through mode
> > >
> > > but all of these attempts were ineffective.
> > >
> > > Given that I am relatively new to FreeBSD, I was hoping to get any
> > insights
> > > as to any next steps that might make
> > > sense in terms of either working around the problem, narrowing down the
> > > bug, or any obvious rookie mistakes I
> > > am making before I give up and revert back to the 9 branch.
> > >
> > > Thanks for your help!
> > >
> > > Regards,
> >
> > On my dreamplug (model 1001) both the internal and external sd cards are
> > actually usb devices (they show up as /dev/da0 and da1, not mmcsd0/1).
> > I'm not sure if that's true on all models or not.
> >
> > Are you using the stock kernel config (DREAMPLUG-1001)?  If not, have
> > you got "option USB_HOST_ALIGN=32" in your kernel config?
> >
> > Corruption in 32 byte chunks is almost always partial cacheline flush
> > problems, but I haven't seen that happen on dreamplug for a long time
> > (and when I did see it, it was with a sata drive).
> >
> > -- Ian
> >
> >
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