On 01/20/2016 06:35 PM, Dave Hansen wrote: > Here's another revision taking Vlastimil's suggestions about > keeping __get_user_pages_unlocked() as-is in to account. > This does, indeed, look nicer. Now, all the "__" variants > take a full tsk/mm and flags. > > He also noted that the two sites where we called gup with > tsk=NULL were probably incorrectly changing behavior with respect > to fault accounting. Long-term, I wonder if we should just add > a "FOLL_" flag to make that more explicit, but for now, I've > fixed up those sites. > > --- > > From: Dave Hansen <[email protected]> > > For protection keys, we need to understand whether protections > should be enforced in software or not. In general, we enforce > protections when working on our own task, but not when on others. > We call these "current" and "foreign" operations. > > This patch introduces a new get_user_pages() variant: > > get_user_pages_foreign() > > The plain get_user_pages() can no longer be used on mm/tasks > other than 'current/current->mm', which is by far the most common > way it is called. Using it makes a few of the call sites look a > bit nicer. > > In other words, get_user_pages_foreign() is a replacement for > when get_user_pages() is called on non-current tsk/mm. > > This also switches get_user_pages_(un)locked() over to be like > get_user_pages() and not take a tsk/mm. There is no > get_user_pages_foreign_(un)locked(). If someone wants that > behavior they just have to use "__" variant and pass in > FOLL_FOREIGN explicitly.
Hm so this gets a bit ahead of patch "mm: add gup flag to indicate "foreign" mm access", right? It might be cleaner to postpone passing FOLL_FOREIGN until then, but not critical. BTW doesn't that other patch miss passing FOLL_FOREIGN from get_user_pages_foreign() or something? I see it only uses it from break_ksm(), am I missing something?
