On Fri, Dec 17, 2021 at 12:45:45PM -0800, Linus Torvalds wrote: > On Fri, Dec 17, 2021 at 12:42 PM David Hildenbrand <david@xxxxxxxxxx> wrote: > > > > > Then somebody else modified that page, and you got exactly what you > > > asked for - a COW event. The original R/O pin has the original page > > > that it asked for, and can read it just fine. > > > > Where in the code did I ask for a COW event? I asked for a R/O pin, not > > any kind of memory protection. > > Why didn't you ask for a shared pin, if that is what you want? > > We already support that. > > If you don't like the read-only pins, don't use them. It's that simple. So you are saying that if a GUP user wants to see changes made by userspace to the page after the GUP it must ask for FOLL_WRITE, even if it doesn't have intend to write to the page? That's news to me. Or did I misunderstand you? -- Kirill A. Shutemov
