On Mon, Apr 24, 2023 at 08:18:33PM +0100, Lorenzo Stoakes wrote: > I think this patch suggestion has scope crept from 'incremental > improvement' to 'major rework of GUP' at this point. I don't really expect to you clean up all the callers - but we are trying to understand what is actually wrong here to come up with the right FOLL_ names and overall strategy. Leave behind a comment, for instance. I don't think anyone has really thought about the ptrace users too much till now, we were all thinking about DMA use cases, it shows we still have some areas that need attention. > Also surely you'd want to obtain the PTL of all mappings to a file? No, just one is fine. If you do the memcpy under a single PTL that points at a writable copy of the page then everything is trivially fine because it is very similar to what the CPU itself would do, which is fine by definition.. Jason
