[PATCH] s390/mm: Add missing ctor/dtor on page table upgrade

Alexander Gordeev
2025-01-23T16:04:13Z

Commit 78966b550289 ("s390: pgtable: add statistics for PUD and P4D
level page table") misses the call to pagetable_p4d_ctor() against
a newly allocated P4D table in crst_table_upgrade();

Commit 68c601de75d8 ("mm: introduce ctor/dtor at PGD level") misses
the call to pagetable_pgd_ctor() against a newly allocated PGD and
the call to pagetable_dtor() against a newly allocated P4D that is
about to be freed on crst_table_upgrade() PGD upgrade fail path.

The missed constructors and destructor break (at least) the page
table accounting when a process memory space is upgraded.

Reported-by: Heiko Carstens <hca@linux.ibm.com>
Closes: https://lore.kernel.org/all/20250122074954.8685-A-hca@linux.ibm.com/
Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Fixes: 78966b550289 ("s390: pgtable: add statistics for PUD and P4D level page table")
Fixes: 68c601de75d8 ("mm: introduce ctor/dtor at PGD level")
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
---
The patch is against:

git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git next-20250123
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm mm-stable
---
arch/s390/mm/pgalloc.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c
index a4e761902093..d33f55b7ee98 100644
--- a/arch/s390/mm/pgalloc.c
+++ b/arch/s390/mm/pgalloc.c
@@ -88,12 +88,14 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
if (unlikely(!p4d))
goto err_p4d;
crst_table_init(p4d, _REGION2_ENTRY_EMPTY);
+ pagetable_p4d_ctor(virt_to_ptdesc(p4d));
}
if (end > _REGION1_SIZE) {
pgd = crst_table_alloc(mm);
if (unlikely(!pgd))
goto err_pgd;
crst_table_init(pgd, _REGION1_ENTRY_EMPTY);
+ pagetable_pgd_ctor(virt_to_ptdesc(pgd));
}

spin_lock_bh(&mm->page_table_lock);
@@ -130,6 +132,7 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
return 0;

err_pgd:
+ pagetable_dtor(virt_to_ptdesc(p4d));
crst_table_free(mm, p4d);
err_p4d:
return -ENOMEM;
--
2.45.2