On Mon, Jun 13, 2016 at 5:02 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > 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. Nevermind, for this to be useful we would need to fallback to regular mmap for a portion of the linear span. That's different than the badblocks case. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
