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. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
