On Mon, Jun 13, 2016 at 4:59 PM, Kani, Toshimitsu <toshi.kani@xxxxxxx> wrote: > 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. Hmm, but we already violate this with badblocks. The device is DAX capable, but certain LBAs will return an error if direct_access is attempted. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
