On Thu, 2012-07-12 at 15:48 +0200, Mike Galbraith wrote: 

On Thu, 2012-07-12 at 15:43 +0200, Thomas Gleixner wrote: 

quoted

On Thu, 12 Jul 2012, Mike Galbraith wrote:

quoted

On Thu, 2012-07-12 at 15:31 +0200, Thomas Gleixner wrote: 

quoted

A quick check for memcpy finds that __btrfs_close_devices() does a
memcpy of btrfs_device structs w/o initializing the lock in the new
copy, but I have no idea whether that's the place we are looking for.

Cool, you found one, thanks!  I'm setting boobytraps.

Um, correction, box says I'm setting _buggy_ boobytraps :)

Tomorrow-man will test this and frob traps anew.

What kind of test setup do you have? i.e. raid, single disk ...

Yeah, megaraid sas.. x3550 M3.

(one disk for OS, one disk for xfstests to mangle)