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. > > Signed-off-by: Dave Hansen <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: Kirill A. Shutemov <[email protected]> > Cc: Andrea Arcangeli <[email protected]> > Cc: Naoya Horiguchi <[email protected]> > Cc: [email protected] > Cc: [email protected] > --- >
After you fix up the nommu version of __get_user_pages_unlocked() below to match the mmu one, Acked-by: Vlastimil Babka <[email protected]> > diff -puN mm/nommu.c~get_current_user_pages mm/nommu.c > --- a/mm/nommu.c~get_current_user_pages 2016-01-19 15:48:31.794063748 > -0800 > +++ b/mm/nommu.c 2016-01-19 15:48:31.835065603 -0800 [...] > -long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, > - unsigned long start, unsigned long nr_pages, > +long get_user_pages(unsigned long start, unsigned long nr_pages, > + int write, int force, struct page **pages, > + struct vm_area_struct **vmas) > +{ > + return get_user_pages_foreign(current, current->mm, start, nr_pages, > + write, force, pages, vmas); > +} > +EXPORT_SYMBOL(get_user_pages); > + > +long __get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, > int write, int force, struct page **pages, > unsigned int gup_flags) > { > long ret; > - down_read(&mm->mmap_sem); > - ret = get_user_pages(tsk, mm, start, nr_pages, write, force, > - pages, NULL); > - up_read(&mm->mmap_sem); > + down_read(¤t->mm->mmap_sem); > + ret = get_user_pages(start, nr_pages, write, force, pages, NULL); > + up_read(¤t->mm->mmap_sem); > return ret; > } > EXPORT_SYMBOL(__get_user_pages_unlocked); > > -long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, > - unsigned long start, unsigned long nr_pages, > +long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, > int write, int force, struct page **pages) > { > - return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write, > + return __get_user_pages_unlocked(start, nr_pages, write, > force, pages, 0); > } > EXPORT_SYMBOL(get_user_pages_unlocked);
