On Mon, 2014-01-13 at 11:34 +0530, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>
> This patch fix the below crash
Andrea, can you ack the generic bit please ?
Thanks !
Cheers,
Ben.
> NIP [c00000000004cee4] .__hash_page_thp+0x2a4/0x440
> LR [c0000000000439ac] .hash_page+0x18c/0x5e0
> ...
> Call Trace:
> [c000000736103c40] [00001ffffb000000] 0x1ffffb000000(unreliable)
> [437908.479693] [c000000736103d50] [c0000000000439ac] .hash_page+0x18c/0x5e0
> [437908.479699] [c000000736103e30] [c00000000000924c] .do_hash_page+0x4c/0x58
>
> On ppc64 we use the pgtable for storing the hpte slot information and
> store address to the pgtable at a constant offset (PTRS_PER_PMD) from
> pmd. On mremap, when we switch the pmd, we need to withdraw and deposit
> the pgtable again, so that we find the pgtable at PTRS_PER_PMD offset
> from new pmd.
>
> We also want to move the withdraw and deposit before the set_pmd so
> that, when page fault find the pmd as trans huge we can be sure that
> pgtable can be located at the offset.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> ---
> Changes from V3:
> * Drop "powerpc: mm: Move ppc64 page table range definitions to separate header"" patch
>
> arch/powerpc/include/asm/pgtable-ppc64.h | 14 ++++++++++++++
> include/asm-generic/pgtable.h | 12 ++++++++++++
> mm/huge_memory.c | 14 +++++---------
> 3 files changed, 31 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/pgtable-ppc64.h b/arch/powerpc/include/asm/pgtable-ppc64.h
> index 4a191c472867..d27960c89a71 100644
> --- a/arch/powerpc/include/asm/pgtable-ppc64.h
> +++ b/arch/powerpc/include/asm/pgtable-ppc64.h
> @@ -558,5 +558,19 @@ extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
> #define __HAVE_ARCH_PMDP_INVALIDATE
> extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
> pmd_t *pmdp);
> +
> +#define pmd_move_must_withdraw pmd_move_must_withdraw
> +typedef struct spinlock spinlock_t;
> +static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
> + spinlock_t *old_pmd_ptl)
> +{
> + /*
> + * Archs like ppc64 use pgtable to store per pmd
> + * specific information. So when we switch the pmd,
> + * we should also withdraw and deposit the pgtable
> + */
> + return true;
> +}
> +
> #endif /* __ASSEMBLY__ */
> #endif /* _ASM_POWERPC_PGTABLE_PPC64_H_ */
> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
> index db0923458940..8e4f41d9af4d 100644
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -558,6 +558,18 @@ static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
> }
> #endif
>
> +#ifndef pmd_move_must_withdraw
> +static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
> + spinlock_t *old_pmd_ptl)
> +{
> + /*
> + * With split pmd lock we also need to move preallocated
> + * PTE page table if new_pmd is on different PMD page table.
> + */
> + return new_pmd_ptl != old_pmd_ptl;
> +}
> +#endif
> +
> /*
> * This function is meant to be used by sites walking pagetables with
> * the mmap_sem hold in read mode to protect against MADV_DONTNEED and
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 95d1acb0f3d2..5d80c53b87cb 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1502,19 +1502,15 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
> spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
> pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
> VM_BUG_ON(!pmd_none(*new_pmd));
> - set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
> - if (new_ptl != old_ptl) {
> - pgtable_t pgtable;
>
> - /*
> - * Move preallocated PTE page table if new_pmd is on
> - * different PMD page table.
> - */
> + if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
> + pgtable_t pgtable;
> pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
> pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
> -
> - spin_unlock(new_ptl);
> }
> + set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
> + if (new_ptl != old_ptl)
> + spin_unlock(new_ptl);
> spin_unlock(old_ptl);
> }
> out:
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