On Mon, 24 Sep 2018, Vlastimil Babka wrote:
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -653,13 +653,23 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
> > #endif
> > #endif /* CONFIG_ARCH_HAS_PKEYS */
> > };
> > + unsigned long flags = vma->vm_flags;
> > size_t i;
> >
> > + /*
> > + * Disabling thp is possible through both MADV_NOHUGEPAGE and
> > + * PR_SET_THP_DISABLE. Both historically used VM_NOHUGEPAGE. Since
> > + * the introduction of MMF_DISABLE_THP, however, userspace needs the
> > + * ability to detect vmas where thp is not eligible in the same manner.
> > + */
> > + if (vma->vm_mm && test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
> > + flags |= VM_NOHUGEPAGE;
>
> Should it also clear VM_HUGEPAGE? In case MMF_DISABLE_THP overrides a
> madvise(MADV_HUGEPAGE)'d vma? (I expect it does?)
>
Good point, I think that is should because MMF_DISABLE_THP will override
VM_HUGEPAGE. It looks like the Documentation file is still referencing
both as advise flags and doesn't address PR_SET_THP_DISABLE. Let me send
a v2 with a Documentation update and your suggested fix. Thanks
Vlastimil!
> > +
> > seq_puts(m, "VmFlags: ");
> > for (i = 0; i < BITS_PER_LONG; i++) {
> > if (!mnemonics[i][0])
> > continue;
> > - if (vma->vm_flags & (1UL << i)) {
> > + if (flags & (1UL << i)) {
> > seq_putc(m, mnemonics[i][0]);
> > seq_putc(m, mnemonics[i][1]);
> > seq_putc(m, ' ');
> >
