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| author | Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> | 2015-10-09 08:32:21 +0530 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2015-10-12 15:30:09 +1100 |
| commit | 891121e6c02c6242487aa4ea1d5c75b7ecdc45ee (patch) | |
| tree | 118c5b4df68fe004438e4a1a629b04fbeed9b417 /arch/powerpc/include/asm/pgtable.h | |
| parent | ec2640b114d535ba7d895b6ee353791d542f2407 (diff) | |
| download | linux-891121e6c02c6242487aa4ea1d5c75b7ecdc45ee.tar.bz2 | |
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/include/asm/pgtable.h')
| -rw-r--r-- | arch/powerpc/include/asm/pgtable.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h index 0717693c8428..b64b4212b71f 100644 --- a/arch/powerpc/include/asm/pgtable.h +++ b/arch/powerpc/include/asm/pgtable.h @@ -259,15 +259,15 @@ extern int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, #define has_transparent_hugepage() 0 #endif pte_t *__find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, - unsigned *shift); + bool *is_thp, unsigned *shift); static inline pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, - unsigned *shift) + bool *is_thp, 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); + return __find_linux_pte_or_hugepte(pgdir, ea, is_thp, shift); } #endif /* __ASSEMBLY__ */ |