On Mon, 2016-06-13 at 16:18 -0700, Dan Williams wrote: > Thanks Toshi! > > On Mon, Jun 13, 2016 at 3:21 PM, Toshi Kani <toshi.kani@xxxxxxx> wrote: > > > > This patch-set adds DAX support to device-mapper dm-linear devices > > used by LVM. It works with LVM commands as follows: > > - Creation of a logical volume with all DAX capable devices (such > > as pmem) sets the logical volume DAX capable as well. > > - Once a logical volume is set to DAX capable, the volume may not > > be extended with non-DAX capable devices. > > I don't mind this, but it seems a policy decision that the kernel does > not need to make. A sufficiently sophisticated user could cope with > DAX being available at varying LBAs. Would it be sufficient to move > this policy decision to userspace tooling? I think this is a kernel restriction. When a block device is declared as DAX capable, it should mean that the whole device is DAX capable. So, I think we need to assure the same to a mapped device. In LVM level, a volume group may contain both DAX and non-DAX capable devices. There is no restriction for creating/extending a volume group. > > The direct_access interface is added to dm and dm-linear to map > > a request to a target device. > > I had dm-linear and md-raid0 support on my list of things to look at, > did you have raid0 in your plans? Yes, I hope to extend further and raid0 is a good candidate. Thanks, -Toshi -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
