On Tue, Jan 11, 2022 at 12:17:18AM -0800, John Hubbard wrote: > Zooming in on the pinning aspect for a moment: last time I attempted to > convert O_DIRECT callers from gup to pup, I recall wanting very much to > record, in each bio_vec, whether these pages were acquired via FOLL_PIN, > or some non-FOLL_PIN method. Because at the end of the IO, it is not > easy to disentangle which pages require put_page() and which require > unpin_user_page*(). > > And changing the bio_vec for *that* purpose was not really acceptable. > > But now that you're looking to change it in a big way (and with some > spare bits avaiable...oohh!), maybe I can go that direction after all. > > Or, are you looking at a design in which any phyr is implicitly FOLL_PIN'd > if it exists at all? That. I think there's still good reasons to keep a single-page (or maybe dual-page) GUP around, but no reason to mix it with ranges. > Or any other thoughts in this area are very welcome. That's there's no support for unpinning part of a range. You pin it, do the IO, unpin it. That simplifies the accounting.
