Re: [RFC v3 03/17] mm: Introduce pte_spinlock

[Laurent Dufour]

On 30/04/2017 06:47, Matthew Wilcox wrote:
> On Thu, Apr 27, 2017 at 05:52:42PM +0200, Laurent Dufour wrote:
>> +++ b/mm/memory.c
>> @@ -2100,6 +2100,13 @@ static inline void wp_page_reuse(struct vm_fault *vmf)
>>  	pte_unmap_unlock(vmf->pte, vmf->ptl);
>>  }
>>  
>> +static bool pte_spinlock(struct vm_fault *vmf)
>> +{
>> +	vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
>> +	spin_lock(vmf->ptl);
>> +	return true;
>> +}
> 
> To me 'pte_spinlock' is a noun, but this is really pte_spin_lock() (a verb).

Fair enough. Even pte_trylock() should be more accurate since patch 8/17
changes this function to call spin_trylock().

> Actually, it's really vmf_lock_pte().  We're locking the pte
> referred to by this vmf.  And so we should probably have a matching
> vmf_unlock_pte(vmf) to preserve the abstraction.

I'm not sure this will ease the reading. In most of this code, the pte
are unlocked through the call to pte_unmap_unlock().
The call to pte_trylock() has been introduced because in few cases there
is the need to check the VMA validity before calling spinlock(ptl). The
unlock is then managed through pte_unmap_unlock().