On Mon, Dec 3, 2018 at 11:25 AM Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> wrote: > > Add a means of exposing if a pagemap supports refcount pinning. I am doing > this to expose if a given pagemap has backing struct pages that will allow > for the reference count of the page to be incremented to lock the page > into place. > > The KVM code already has several spots where it was trying to use a > pfn_valid check combined with a PageReserved check to determien if it could > take a reference on the page. I am adding this check so in the case of the > page having the reserved flag checked we can check the pagemap for the page > to determine if we might fall into the special DAX case. > > Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> > --- > drivers/nvdimm/pfn_devs.c | 2 ++ > include/linux/memremap.h | 5 ++++- > include/linux/mm.h | 11 +++++++++++ > 3 files changed, 17 insertions(+), 1 deletion(-) > > diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c > index 6f22272e8d80..7a4a85bcf7f4 100644 > --- a/drivers/nvdimm/pfn_devs.c > +++ b/drivers/nvdimm/pfn_devs.c > @@ -640,6 +640,8 @@ static int __nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap) > } else > return -ENXIO; > > + pgmap->support_refcount_pinning = true; > + There should be no dev_pagemap instance instance where this isn't true, so I'm missing why this is needed?
