Re: [PATCH] mm: Fix pud_alloc_track()

From: Sedat Dilek
Date: Thu Jun 04 2020 - 12:58:44 EST


On Thu, Jun 4, 2020 at 6:49 PM Mike Rapoport <rppt@xxxxxxxxxx> wrote:
>
> On Thu, Jun 04, 2020 at 09:44:46AM +0200, Joerg Roedel wrote:
> > From: Joerg Roedel <jroedel@xxxxxxx>
> >
> > The pud_alloc_track() needs to do different checks based on whether
> > __ARCH_HAS_5LEVEL_HACK is defined, like it already does in
> > pud_alloc(). Otherwise it causes boot failures on PowerPC.
> >
> > Provide the correct implementations for both possible settings of
> > __ARCH_HAS_5LEVEL_HACK to fix the boot problems.
>
> There is a patch in mmotm [1] that completely removes
> __ARCH_HAS_5LEVEL_HACK which is a part of the series [2] that updates
> p4d folding accross architectures. This should fix boot on PowerPC and
> the addition of pXd_alloc_track() for __ARCH_HAS_5LEVEL_HACK wouldn't be
> necessary.
>
>
> [1] https://github.com/hnaz/linux-mm/commit/cfae68792af3731ac902ea6ba5ed8df5a0f6bd2f
> [2] https://lore.kernel.org/kvmarm/20200414153455.21744-1-rppt@xxxxxxxxxx/
>

That link shows an overview of v4 and is easily downloadable as a
single mbox file.
See " Series = mm: remove __ARCH_HAS_5LEVEL_HACK"

- Sedat -

[1] https://lore.kernel.org/patchwork/project/lkml/list/?series=438627

> > Reported-by: Abdul Haleem <abdhalee@xxxxxxxxxxxxxxxxxx>
> > Tested-by: Abdul Haleem <abdhalee@xxxxxxxxxxxxxxxxxx>
> > Tested-by: Satheesh Rajendran <sathnaga@xxxxxxxxxxxxxxxxxx>
> > Fixes: d8626138009b ("mm: add functions to track page directory modifications")
> > Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
> > ---
> > include/asm-generic/5level-fixup.h | 5 +++++
> > include/linux/mm.h | 26 +++++++++++++-------------
> > 2 files changed, 18 insertions(+), 13 deletions(-)
> >
> > diff --git a/include/asm-generic/5level-fixup.h b/include/asm-generic/5level-fixup.h
> > index 58046ddc08d0..afbab31fbd7e 100644
> > --- a/include/asm-generic/5level-fixup.h
> > +++ b/include/asm-generic/5level-fixup.h
> > @@ -17,6 +17,11 @@
> > ((unlikely(pgd_none(*(p4d))) && __pud_alloc(mm, p4d, address)) ? \
> > NULL : pud_offset(p4d, address))
> >
> > +#define pud_alloc_track(mm, p4d, address, mask) \
> > + ((unlikely(pgd_none(*(p4d))) && \
> > + (__pud_alloc(mm, p4d, address) || ({*(mask)|=PGTBL_P4D_MODIFIED;0;})))? \
> > + NULL : pud_offset(p4d, address))
> > +
> > #define p4d_alloc(mm, pgd, address) (pgd)
> > #define p4d_alloc_track(mm, pgd, address, mask) (pgd)
> > #define p4d_offset(pgd, start) (pgd)
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 66e0977f970a..ad3b31c5bcc3 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -2088,35 +2088,35 @@ static inline pud_t *pud_alloc(struct mm_struct *mm, p4d_t *p4d,
> > NULL : pud_offset(p4d, address);
> > }
> >
> > -static inline p4d_t *p4d_alloc_track(struct mm_struct *mm, pgd_t *pgd,
> > +static inline pud_t *pud_alloc_track(struct mm_struct *mm, p4d_t *p4d,
> > unsigned long address,
> > pgtbl_mod_mask *mod_mask)
> > -
> > {
> > - if (unlikely(pgd_none(*pgd))) {
> > - if (__p4d_alloc(mm, pgd, address))
> > + if (unlikely(p4d_none(*p4d))) {
> > + if (__pud_alloc(mm, p4d, address))
> > return NULL;
> > - *mod_mask |= PGTBL_PGD_MODIFIED;
> > + *mod_mask |= PGTBL_P4D_MODIFIED;
> > }
> >
> > - return p4d_offset(pgd, address);
> > + return pud_offset(p4d, address);
> > }
> >
> > -#endif /* !__ARCH_HAS_5LEVEL_HACK */
> > -
> > -static inline pud_t *pud_alloc_track(struct mm_struct *mm, p4d_t *p4d,
> > +static inline p4d_t *p4d_alloc_track(struct mm_struct *mm, pgd_t *pgd,
> > unsigned long address,
> > pgtbl_mod_mask *mod_mask)
> > +
> > {
> > - if (unlikely(p4d_none(*p4d))) {
> > - if (__pud_alloc(mm, p4d, address))
> > + if (unlikely(pgd_none(*pgd))) {
> > + if (__p4d_alloc(mm, pgd, address))
> > return NULL;
> > - *mod_mask |= PGTBL_P4D_MODIFIED;
> > + *mod_mask |= PGTBL_PGD_MODIFIED;
> > }
> >
> > - return pud_offset(p4d, address);
> > + return p4d_offset(pgd, address);
> > }
> >
> > +#endif /* !__ARCH_HAS_5LEVEL_HACK */
> > +
> > static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
> > {
> > return (unlikely(pud_none(*pud)) && __pmd_alloc(mm, pud, address))?
> > --
> > 2.26.2
> >
>
> --
> Sincerely yours,
> Mike.