On Wed, Sep 29, 2021 at 03:34:22PM -0600, Logan Gunthorpe wrote: > > > > On 2021-09-28 1:47 p.m., Jason Gunthorpe wrote: > > On Thu, Sep 16, 2021 at 05:40:54PM -0600, Logan Gunthorpe wrote: > >> Callers that expect PCI P2PDMA pages can now set FOLL_PCI_P2PDMA to > >> allow obtaining P2PDMA pages. If a caller does not set this flag > >> and tries to map P2PDMA pages it will fail. > >> > >> This is implemented by adding a flag and a check to get_dev_pagemap(). > > > > I would like to see the get_dev_pagemap() deleted from GUP in the > > first place. > > > > Why isn't this just a simple check of the page->pgmap type after > > acquiring a valid page reference? See my prior note > > It could be, but that will mean dereferencing the pgmap for every page > to determine the type of page and then comparing with FOLL_PCI_P2PDMA. It would be done under the pte devmap test and this is less expensive than the xarray search. Jason
