The patch titled
Subject: mm/huge_memory.c: fix modifying of page protection by insert_pfn_pmd()
has been added to the -mm tree. Its filename is
mm-fix-modifying-of-page-protection-by-insert_pfn_pmd.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-fix-modifying-of-page-protection-by-insert_pfn_pmd.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-modifying-of-page-protection-by-insert_pfn_pmd.patch
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------------------------------------------------------
From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Subject: mm/huge_memory.c: fix modifying of page protection by insert_pfn_pmd()
With some architectures like ppc64, set_pmd_at() cannot cope with a
situation where there is already some (different) valid entry present.
Use pmdp_set_access_flags() instead to modify the pfn which is built to
deal with modifying existing PMD entries.
This is similar to cae85cb8add3 ("mm/memory.c: fix modifying of page
protection by insert_pfn()")
We also do similar update w.r.t insert_pfn_pud eventhough ppc64 don't
support pud pfn entries now.
Without this patch we also see the below message in kernel log "BUG:
non-zero pgtables_bytes on freeing mm:"
Link: http://lkml.kernel.org/r/20190402115125.18803-1-aneesh.kumar@xxxxxxxxxxxxx
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Reported-by: Chandan Rajendra <chandan@xxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
--- a/mm/huge_memory.c~mm-fix-modifying-of-page-protection-by-insert_pfn_pmd
+++ a/mm/huge_memory.c
@@ -755,6 +755,21 @@ static void insert_pfn_pmd(struct vm_are
spinlock_t *ptl;
ptl = pmd_lock(mm, pmd);
+ if (!pmd_none(*pmd)) {
+ if (write) {
+ if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
+ WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
+ goto out_unlock;
+ }
+ entry = pmd_mkyoung(*pmd);
+ entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+ if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
+ update_mmu_cache_pmd(vma, addr, pmd);
+ }
+
+ goto out_unlock;
+ }
+
entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
if (pfn_t_devmap(pfn))
entry = pmd_mkdevmap(entry);
@@ -766,11 +781,16 @@ static void insert_pfn_pmd(struct vm_are
if (pgtable) {
pgtable_trans_huge_deposit(mm, pmd, pgtable);
mm_inc_nr_ptes(mm);
+ pgtable = NULL;
}
set_pmd_at(mm, addr, pmd, entry);
update_mmu_cache_pmd(vma, addr, pmd);
+
+out_unlock:
spin_unlock(ptl);
+ if (pgtable)
+ pte_free(mm, pgtable);
}
vm_fault_t vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
@@ -821,6 +841,20 @@ static void insert_pfn_pud(struct vm_are
spinlock_t *ptl;
ptl = pud_lock(mm, pud);
+ if (!pud_none(*pud)) {
+ if (write) {
+ if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
+ WARN_ON_ONCE(!is_huge_zero_pud(*pud));
+ goto out_unlock;
+ }
+ entry = pud_mkyoung(*pud);
+ entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
+ if (pudp_set_access_flags(vma, addr, pud, entry, 1))
+ update_mmu_cache_pud(vma, addr, pud);
+ }
+ goto out_unlock;
+ }
+
entry = pud_mkhuge(pfn_t_pud(pfn, prot));
if (pfn_t_devmap(pfn))
entry = pud_mkdevmap(entry);
@@ -830,6 +864,8 @@ static void insert_pfn_pud(struct vm_are
}
set_pud_at(mm, addr, pud, entry);
update_mmu_cache_pud(vma, addr, pud);
+
+out_unlock:
spin_unlock(ptl);
}
_
Patches currently in -mm which might be from aneesh.kumar@xxxxxxxxxxxxx are
mm-fix-modifying-of-page-protection-by-insert_pfn_pmd.patch
mm-page_mkclean-vs-madv_dontneed-race.patch
