On Wed, Nov 8, 2017 at 12:26 PM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > On Wed, 8 Nov 2017, Christoph Hellwig wrote: > >> Can you start by explaining what you actually need the vmap for? > > It is possible to use lvm on persistent memory. You can create linear or > striped logical volumes on persistent memory and these volumes still have > the direct_access method, so they can be mapped with the function > dax_direct_access(). > > If we create logical volumes on persistent memory, the method > dax_direct_access() won't return the whole device, it will return only a > part. When dax_direct_access() returns the whole device, my driver just > uses it without vmap. When dax_direct_access() return only a part of the > device, my driver calls it repeatedly to get all the parts and then > assembles the parts into a linear address space with vmap. I know I proposed "call dax_direct_access() once" as a strawman for an in-kernel driver user, but it's better to call it per access so you can better stay in sync with base driver events like new media errors and unplug / driver-unload. Either that, or at least have a plan how to handle those events. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
