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authorGerald Schaefer <gerald.schaefer@de.ibm.com>2020-05-06 13:04:07 +0200
committerVasily Gorbik <gor@linux.ibm.com>2020-05-20 10:13:27 +0200
commitac8372f3b4e41015549b331a4f350224661e7fc6 (patch)
tree80c620f663dddc5c60964399729f0bbed817546e /arch
parent70b690547d5ea1a3d135a4cc39cd1e08246d0c3a (diff)
downloadlinux-sh-ac8372f3b4e41015549b331a4f350224661e7fc6.tar.gz
s390/mm: fix set_huge_pte_at() for empty ptes
On s390, the layout of normal and large ptes (i.e. pmds/puds) differs. Therefore, set_huge_pte_at() does a conversion from a normal pte to the corresponding large pmd/pud. So, when converting an empty pte, this should result in an empty pmd/pud, which would return true for pmd/pud_none(). However, after conversion we also mark the pmd/pud as large, and therefore present. For empty ptes, this will result in an empty pmd/pud that is also marked as large, and pmd/pud_none() would not return true. There is currently no issue with this behaviour, as set_huge_pte_at() does not seem to be called for empty ptes. It would be valid though, so let's fix this by not marking empty ptes as large in set_huge_pte_at(). This was found by testing a patch from from Anshuman Khandual, which is currently discussed on LKML ("mm/debug: Add more arch page table helper tests"). Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/s390/mm/hugetlbpage.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/s390/mm/hugetlbpage.c b/arch/s390/mm/hugetlbpage.c
index f01daddcbc5e..4632d4e26b66 100644
--- a/arch/s390/mm/hugetlbpage.c
+++ b/arch/s390/mm/hugetlbpage.c
@@ -159,10 +159,13 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
rste &= ~_SEGMENT_ENTRY_NOEXEC;
/* Set correct table type for 2G hugepages */
- if ((pte_val(*ptep) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
- rste |= _REGION_ENTRY_TYPE_R3 | _REGION3_ENTRY_LARGE;
- else
+ if ((pte_val(*ptep) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3) {
+ if (likely(pte_present(pte)))
+ rste |= _REGION3_ENTRY_LARGE;
+ rste |= _REGION_ENTRY_TYPE_R3;
+ } else if (likely(pte_present(pte)))
rste |= _SEGMENT_ENTRY_LARGE;
+
clear_huge_pte_skeys(mm, rste);
pte_val(*ptep) = rste;
}