Re: [PATCH v2 3/4] btrfs: Add zstd support

[Austin S. Hemmelgarn]

On 2017-07-07 23:07, Adam Borowski wrote:
> On Sat, Jul 08, 2017 at 01:40:18AM +0200, Adam Borowski wrote:
> > On Fri, Jul 07, 2017 at 11:17:49PM +0000, Nick Terrell wrote:
> > > On 7/6/17, 9:32 AM, "Adam Borowski" <kilobyte@xxxxxxxxxx> wrote:
> > > > Got a reproducible crash on amd64:
> >
> > > Thanks for the bug report Adam! I'm looking into the failure, and haven't
> > > been able to reproduce it yet. I've built my kernel from your tree, and
> > > I ran your script with the kernel.tar tarball 100 times, but haven't gotten
> > > a failure yet.
> >
> > > I have a few questions to guide my debugging.
> > >
> > > - How many cores are you running with? Iâve run the script with 1, 2, and 4 cores.
> > > - Which version of gcc are you using to compile the kernel? Iâm using gcc-6.2.0-5ubuntu12.
> > > - Are the failures always in exactly the same place, and does it fail 100%
> > >    of the time or just regularly?
> >
> > 6 cores -- all on bare metal.  gcc-7.1.0-9.
> > Lemme try with gcc-6, a different config or in a VM.
>
> I've tried the following:
> * gcc-6, defconfig (+btrfs obviously)
> * gcc-7, defconfig
> * gcc-6, my regular config
> * gcc-7, my regular config
> * gcc-7, debug + UBSAN + etc
> * gcc-7, defconfig, qemu-kvm with only 1 core
>
> Every build with gcc-7 reproduces the crash, every with gcc-6 does not.
Got a GCC7 tool-chain built, and I can confirm this here too, tested 
with various numbers of cores ranging from 1-32 in a QEMU+KVM VM, with 
various combinations of debug options and other config switches.