On Tue, Jan 19, 2021 at 01:34:26PM -0500, Pavel Tatashin wrote: > On Tue, Jan 19, 2021 at 1:30 PM Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > > > On Mon, Jan 18, 2021 at 11:39:14PM -0500, Pavel Tatashin wrote: > > > Zero page should not be used for long term pinned pages. Once pages > > > are pinned their physical addresses cannot changed until they are unpinned. > > > > > > Guarantee to always return real pages when they are pinned by adding > > > FOLL_WRITE. > > > > > > Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> > > > mm/gup.c | 10 +++++++++- > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > No, this will definitely break things > > What will break Things assuming GUP doesn't break COW, making all GUP WRITE was already tried and revered for some other reason > > Why does the zero page have to be movable? > > It is not even about being movable, we can't cow pinned pages returned > by GUP call, how can we use zero page for that? The zero page is always zero, it is never written to. What does cow matter? Jason
