On Thu 01-09-16 20:57:38, Ross Zwisler wrote: > On Wed, Aug 31, 2016 at 04:44:47PM +0800, Xiao Guangrong wrote: > > On 08/31/2016 01:09 AM, Dan Williams wrote: > > > > > > Can you post your exact reproduction steps? This test is not failing for me. > > > > > > > Sure. > > > > 1. make the guest kernel based on your tree, the top commit is > > 10d7902fa0e82b (dax: unmap/truncate on device shutdown) and > > the config file can be found in this thread. > > > > 2. add guest kernel command line: memmap=6G!10G > > > > 3: start the guest: > > x86_64-softmmu/qemu-system-x86_64 -machine pc,nvdimm --enable-kvm \ > > -smp 16 -m 32G,maxmem=100G,slots=100 /other/VMs/centos6.img -monitor stdio > > > > 4: in guest: > > mkfs.ext4 /dev/pmem0 > > mount -o dax /dev/pmem0 /mnt/pmem/ > > echo > /mnt/pmem/xxx > > ./mmap /mnt/pmem/xxx > > ./read /mnt/pmem/xxx > > > > The source code of mmap and read has been attached in this mail. > > > > Hopefully, you can detect the error triggered by read test. > > > > Thanks! > > Okay, I think I've isolated this issue. Xiao's VM was an old CentOS 6 system, > and for some reason ext4+DAX with the old tools found in that VM fails. I was > able to reproduce this failure with a freshly installed CentOS 6.8 VM. > > You can see the failure with his tests, or perhaps more easily with this > series of commands: > > # mkfs.ext4 /dev/pmem0 > # mount -o dax /dev/pmem0 /mnt/pmem/ > # touch /mnt/pmem/x > # md5sum /mnt/pmem/x > md5sum: /mnt/pmem/x: Bad address > > This sequence of commands works fine in the old CentOS 6 system if you use XFS > instead of ext4, and it works fine with both ext4 and XFS in CentOS 7 and > with recent versions of Fedora. > > I've added the ext4 folks to this mail in case they care, but my guess is that > the tools in CentOS 6 are so old that it's not worth worrying about. For > reference, the kernel in CentOS 6 is based on 2.6.32. :) DAX was introduced > in v4.0. Hum, can you post 'dumpe2fs -h /dev/pmem0' output from that system when the md5sum fails? Because the only idea I have is that mkfs.ext4 in CentOS 6 creates the filesystem with a different set of features than more recent e2fsprogs and so we hit some untested path... Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
