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| author | Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> | 2015-03-30 07:11:03 +0200 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2015-04-17 03:23:39 +0200 |
| commit | 691e95fd7396905a38d98919e9c150dbc3ea21a3 (patch) | |
| tree | d89b898d4f42d167f0da169f482d7104b46870d8 /arch/powerpc/include/asm | |
| parent | KVM: PPC: Remove page table walk helpers (diff) | |
| download | linux-691e95fd7396905a38d98919e9c150dbc3ea21a3.tar.xz linux-691e95fd7396905a38d98919e9c150dbc3ea21a3.zip | |
powerpc/mm/thp: Make page table walk safe against thp split/collapse
We can disable a THP split or a hugepage collapse by disabling irq.
We do send IPI to all the cpus in the early part of split/collapse,
and disabling local irq ensure we don't make progress with
split/collapse. If the THP is getting split we return NULL from
find_linux_pte_or_hugepte(). For all the current callers it should be ok.
We need to be careful if we want to use returned pte_t pointer outside
the irq disabled region. W.r.t to THP split, the pfn remains the same,
but then a hugepage collapse will result in a pfn change. There are
few steps we can take to avoid a hugepage collapse.One way is to take page
reference inside the irq disable region. Other option is to take
mmap_sem so that a parallel collapse will not happen. We can also
disable collapse by taking pmd_lock. Another method used by kvm
subsystem is to check whether we had a mmu_notifer update in between
using mmu_notifier_retry().
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/include/asm')
| -rw-r--r-- | arch/powerpc/include/asm/pgtable.h | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h index 92fe01c355a9..11a38635dd65 100644 --- a/arch/powerpc/include/asm/pgtable.h +++ b/arch/powerpc/include/asm/pgtable.h @@ -247,8 +247,17 @@ extern int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, #define pmd_large(pmd) 0 #define has_transparent_hugepage() 0 #endif -pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, +pte_t *__find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, unsigned *shift); +static inline pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, + unsigned *shift) +{ + if (!arch_irqs_disabled()) { + pr_info("%s called with irq enabled\n", __func__); + dump_stack(); + } + return __find_linux_pte_or_hugepte(pgdir, ea, shift); +} #endif /* __ASSEMBLY__ */ #endif /* __KERNEL__ */ |