Re: [PATCH] mm: Fix pud_alloc_track()

On Thu, Jun 4, 2020 at 6:49 PM Mike Rapoport [off-list ref] wrote:

On Thu, Jun 04, 2020 at 09:44:46AM +0200, Joerg Roedel wrote:

quoted

From: Joerg Roedel <redacted>

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@kernel.org/ (local)

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

quoted

Reported-by: Abdul Haleem <redacted>
Tested-by: Abdul Haleem <redacted>
Tested-by: Satheesh Rajendran <redacted>
Fixes: d8626138009b ("mm: add functions to track page directory modifications")
Signed-off-by: Joerg Roedel <redacted>
---
 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.