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Subject: Re: [PATCH v9 05/24] mm: Introduce pte_spinlock for
 FAULT_FLAG_SPECULATIVE
To:     David Rientjes <rientjes@google.com>
Cc:     paulmck@linux.vnet.ibm.com, peterz@infradead.org,
        akpm@linux-foundation.org, kirill@shutemov.name,
        ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net,
        jack@suse.cz, Matthew Wilcox <willy@infradead.org>,
        benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, hpa@zytor.com,
        Will Deacon <will.deacon@arm.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com,
        Daniel Jordan <daniel.m.jordan@oracle.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com,
        npiggin@gmail.com, bsingharora@gmail.com,
        Tim Chen <tim.c.chen@linux.intel.com>,
        linuxppc-dev@lists.ozlabs.org, x86@kernel.org
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From:   Laurent Dufour <ldufour@linux.vnet.ibm.com>
Date:   Wed, 28 Mar 2018 10:15:47 +0200
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On 25/03/2018 23:50, David Rientjes wrote:
> On Tue, 13 Mar 2018, Laurent Dufour wrote:
> 
>> When handling page fault without holding the mmap_sem the fetch of the
>> pte lock pointer and the locking will have to be done while ensuring
>> that the VMA is not touched in our back.
>>
>> So move the fetch and locking operations in a dedicated function.
>>
>> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
>> ---
>>  mm/memory.c | 15 +++++++++++----
>>  1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index 8ac241b9f370..21b1212a0892 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -2288,6 +2288,13 @@ int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
>>  }
>>  EXPORT_SYMBOL_GPL(apply_to_page_range);
>>  
>> +static bool pte_spinlock(struct vm_fault *vmf)
> 
> inline?

You're right.
Indeed this was done in the patch 18 : "mm: Provide speculative fault
infrastructure", but this has to be done there too, I'll fix that.

> 
>> +{
>> +	vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
>> +	spin_lock(vmf->ptl);
>> +	return true;
>> +}
>> +
>>  static bool pte_map_lock(struct vm_fault *vmf)
>>  {
>>  	vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd,
> 
> Shouldn't pte_unmap_same() take struct vm_fault * and use the new 
> pte_spinlock()?

done in the next patch, but you already acked it..