Re: [PATCH] mm/swapfile: fix swapoff vs. software dirty bits

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Fri, Sep 18, 2015 at 11:10:38AM +0200, Martin Schwidefsky wrote:
> > 
> > You know, these are only two lines where we use _PAGE_SOFT_DIRTY
> > directly, so I don't see much point in adding 22 lines of code
> > for that. Maybe we can leave it as is?
>  
> Only x86 has pte_clear_flags. And the two lines require that there is exactly
> one bit in the PTE for soft-dirty. An alternative encoding will not be allowed.

Agreed, still I would defer until there is a real need for an alternative encoding.

> And the current set of primitives is asymmetric, there are functions to query
> and set the bit pte_soft_dirty and pte_mksoft_dirty but no function to clear
> the bit.

Yes, but again I don't see an urgent need for these helpers.

Anyway, there is no strong objections against this approach
from my side, but please at least compile-test the patch next
time, because this is definitely a typo

static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd)
{
	return pmp_clear_flags(pmd, _PAGE_SOFT_DIRTY);
}

I bet you meant pmd_clear_flags.

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