On Sat, Apr 23, 2022 at 09:35:42AM -0700, Linus Torvalds wrote: > On Sat, Apr 23, 2022 at 3:07 AM Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > > > The series introduces fault_in_subpage_writeable() together with the > > arm64 probing counterpart and the btrfs fix. > > Looks fine to me - and I think it can probably go through the arm64 > tree since you'd be the only one really testing it anyway. I'll queue it via arm64 then. > I assume you checked that btrfs is the only one that uses > fault_in_writeable() in this way? Everybody else updates to the right > byte boundary and retries (or returns immediately)? I couldn't find any other places (by inspection or testing). The buffered file I/O can already make progress in current fault_in_*() + copy_*_user() loops. O_DIRECT either goes via GUP (and memcpy() doesn't fault) or, if the user buffer is not PAGE aligned, it may fall back to buffered I/O. That's why I simplified the series, AFAICT it's only btrfs search_ioctl() with this problem. -- Catalin
