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author | Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> | 2015-10-09 03:02:21 (GMT) |
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committer | Michael Ellerman <mpe@ellerman.id.au> | 2015-10-12 04:30:09 (GMT) |
commit | 891121e6c02c6242487aa4ea1d5c75b7ecdc45ee (patch) | |
tree | 118c5b4df68fe004438e4a1a629b04fbeed9b417 /arch/powerpc/mm/tlb_hash64.c | |
parent | ec2640b114d535ba7d895b6ee353791d542f2407 (diff) | |
download | linux-891121e6c02c6242487aa4ea1d5c75b7ecdc45ee.tar.xz |
powerpc/mm: Differentiate between hugetlb and THP during page walk
We need to properly identify whether a hugepage is an explicit or
a transparent hugepage in follow_huge_addr(). We used to depend
on hugepage shift argument to do that. But in some case that can
result in wrong results. For ex:
On finding a transparent hugepage we set hugepage shift to PMD_SHIFT.
But we can end up clearing the thp pte, via pmdp_huge_get_and_clear.
We do prevent reusing the pfn page via the usage of
kick_all_cpus_sync(). But that happens after we updated the pte to 0.
Hence in follow_huge_addr() we can find hugepage shift set, but transparent
huge page check fail for a thp pte.
NOTE: We fixed a variant of this race against thp split in commit
691e95fd7396905a38d98919e9c150dbc3ea21a3
("powerpc/mm/thp: Make page table walk safe against thp split/collapse")
Without this patch, we may hit the BUG_ON(flags & FOLL_GET) in
follow_page_mask occasionally.
In the long term, we may want to switch ppc64 64k page size config to
enable CONFIG_ARCH_WANT_GENERAL_HUGETLB
Reported-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/mm/tlb_hash64.c')
-rw-r--r-- | arch/powerpc/mm/tlb_hash64.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/powerpc/mm/tlb_hash64.c b/arch/powerpc/mm/tlb_hash64.c index c522969..f7b8039 100644 --- a/arch/powerpc/mm/tlb_hash64.c +++ b/arch/powerpc/mm/tlb_hash64.c @@ -190,6 +190,7 @@ void tlb_flush(struct mmu_gather *tlb) void __flush_hash_table_range(struct mm_struct *mm, unsigned long start, unsigned long end) { + bool is_thp; int hugepage_shift; unsigned long flags; @@ -208,21 +209,21 @@ void __flush_hash_table_range(struct mm_struct *mm, unsigned long start, local_irq_save(flags); arch_enter_lazy_mmu_mode(); for (; start < end; start += PAGE_SIZE) { - pte_t *ptep = find_linux_pte_or_hugepte(mm->pgd, start, + pte_t *ptep = find_linux_pte_or_hugepte(mm->pgd, start, &is_thp, &hugepage_shift); unsigned long pte; if (ptep == NULL) continue; pte = pte_val(*ptep); - if (hugepage_shift) + if (is_thp) trace_hugepage_invalidate(start, pte); if (!(pte & _PAGE_HASHPTE)) continue; - if (unlikely(hugepage_shift && pmd_trans_huge(*(pmd_t *)pte))) + if (unlikely(is_thp)) hpte_do_hugepage_flush(mm, start, (pmd_t *)ptep, pte); else - hpte_need_flush(mm, start, ptep, pte, 0); + hpte_need_flush(mm, start, ptep, pte, hugepage_shift); } arch_leave_lazy_mmu_mode(); local_irq_restore(flags); |