mount DCPMM fail with dax option

[yong li]

hi, all

I had install DCPMM in my computer and format it with mkfs.ext4. However, it fails when I mount the /dev/pmem0 into /pmem. It can mount success without dax option.

How can resolve this problem?

mkfs.ext4 /dev/pmem0

mount -o dax /dev/pmem0 /pmem0

mount: /pmem0: wrong fs type, bad option, bad superblock on /dev/pmem0, missing codepage or helper program, or other error.

Thanks.

------------

Yong Li

[Jeff Moyer]

Is /dev/pmem0 an fsdax namespace? Is there any information in dmesg
that helps? If not, try:

echo 'file drivers/dax/super.c +p' > /sys/kernel/debug/dynamic_debug/control

and retry the mount. Have a look in dmesg for why the operation failed.

HTH,
Jeff

[Steve Scargall]

If you were using XFS, there is a know DAX and REFLINK incompatibility described in Mounting a DAX XFS file system can return "wrong fs type, bad option, bad superblock, missing code page or helper program, or other error" that would explain the behaviour. ext4 doesn't have reflink and is not affected by that issue. 

In addition to the info Jeff requested, can you also provide more info about your environment:

- Linux Distro:

- Kernel version:

- `ndctl list -N`

- `fsck /dev/pmem0`

/Steve

[yong li]

thanks Jeff and Steve, I had solved the problem. The default mode of aep is raw which not support dax. I changed the mode into fsdax and mount success with dax. 

sudo ndctl create-namespace -f -e namespace0.0 --mode=fsdax

Li

yong li <li.yo...@gmail.com> 于2020年11月18日周三 下午8:59写道：

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