On Mon, Nov 30, 2020 at 11:31:20AM -0400, Jason Gunthorpe wrote:
> On Mon, Nov 30, 2020 at 12:27:10PM +0100, Peter Zijlstra wrote:
> > There's no point in having the identical routines for PTE/PMD have
> > different names.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> > include/linux/pgtable.h | 7 +------
> > mm/hmm.c | 2 +-
> > mm/mapping_dirty_helpers.c | 2 +-
> > mm/mprotect.c | 2 +-
> > mm/userfaultfd.c | 2 +-
> > 5 files changed, 5 insertions(+), 10 deletions(-)
> >
> > +++ b/include/linux/pgtable.h
> > @@ -1244,11 +1244,6 @@ static inline int pud_trans_unstable(pud
> > #endif
> > }
> >
> > -static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
> > -{
> > - return pmdp_get_lockless(pmdp);
> > -}
> > -
> > #ifndef arch_needs_pgtable_deposit
> > #define arch_needs_pgtable_deposit() (false)
> > #endif
> > @@ -1275,7 +1270,7 @@ static inline pmd_t pmd_read_atomic(pmd_
> > */
> > static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd)
> > {
> > - pmd_t pmdval = pmd_read_atomic(pmd);
> > + pmd_t pmdval = pmdp_get_lockless(pmd);
> > /*
> > * The barrier will stabilize the pmdval in a register or on
> > * the stack so that it will stop changing under the code.
> > +++ b/mm/hmm.c
> > @@ -356,7 +356,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
> > * huge or device mapping one and compute corresponding pfn
> > * values.
> > */
> > - pmd = pmd_read_atomic(pmdp);
> > + pmd = pmdp_get_lockless(pmdp);
> > barrier();
> > if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
> > goto again;
>
> The pagewalk API doesn't call the functions with interrupts disabled,
> doesn't this mean we hit this assertion?
>
> +#if CONFIG_PGTABLE_LEVELS > 2
> +static inline pmd_t pmdp_get_lockless(pmd_t *pmdp)
> +{
> + pmd_t pmd;
> +
> + lockdep_assert_irqs_disabled();
> +
>
> It is only holding the read side of the mmap_sem here
Hurmph, good point. I'll see what I can do about that.
