diff mbox series

[v2,2/4] mm/hugetlb.c: Remove the unnecessary non_swap_entry()

Message ID 20200723032248.24772-3-bhe@redhat.com (mailing list archive)
State New, archived
Headers show
Series mm/hugetlb: Small cleanup and improvement | expand

Commit Message

Baoquan He July 23, 2020, 3:22 a.m. UTC 
The checking is_migration_entry() and is_hwpoison_entry() are stricter
than non_swap_entry(), means they have covered the conditional check
which non_swap_entry() is doing.

Hence remove the unnecessary non_swap_entry() in is_hugetlb_entry_migration()
and is_hugetlb_entry_hwpoisoned() to simplify code.

Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 mm/hugetlb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Anshuman Khandual July 23, 2020, 5:06 a.m. UTC | #1 
On 07/23/2020 08:52 AM, Baoquan He wrote:
> The checking is_migration_entry() and is_hwpoison_entry() are stricter
> than non_swap_entry(), means they have covered the conditional check
> which non_swap_entry() is doing.

They are no stricter as such but implicitly contains non_swap_entry() in itself.
If a swap entry tests positive for either is_[migration|hwpoison]_entry(), then
its swap_type() is among SWP_MIGRATION_READ, SWP_MIGRATION_WRITE and SWP_HWPOISON.
All these types >= MAX_SWAPFILES, exactly what is asserted with non_swap_entry().

> 
> Hence remove the unnecessary non_swap_entry() in is_hugetlb_entry_migration()
> and is_hugetlb_entry_hwpoisoned() to simplify code.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> ---
>  mm/hugetlb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 3569e731e66b..c14837854392 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3748,7 +3748,7 @@ bool is_hugetlb_entry_migration(pte_t pte)
>  	if (huge_pte_none(pte) || pte_present(pte))
>  		return false;
>  	swp = pte_to_swp_entry(pte);
> -	if (non_swap_entry(swp) && is_migration_entry(swp))
> +	if (is_migration_entry(swp))
>  		return true;
>  	else
>  		return false;
> @@ -3761,7 +3761,7 @@ static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
>  	if (huge_pte_none(pte) || pte_present(pte))
>  		return false;
>  	swp = pte_to_swp_entry(pte);
> -	if (non_swap_entry(swp) && is_hwpoison_entry(swp))
> +	if (is_hwpoison_entry(swp))
>  		return true;
>  	else
>  		return false;
> 

It would be better if the commit message contains details about
the existing redundant check. But either way.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Baoquan He July 23, 2020, 6:14 a.m. UTC | #2 
On 07/23/20 at 10:36am, Anshuman Khandual wrote:
> 
> 
> On 07/23/2020 08:52 AM, Baoquan He wrote:
> > The checking is_migration_entry() and is_hwpoison_entry() are stricter
> > than non_swap_entry(), means they have covered the conditional check
> > which non_swap_entry() is doing.
> 
> They are no stricter as such but implicitly contains non_swap_entry() in itself.
> If a swap entry tests positive for either is_[migration|hwpoison]_entry(), then
> its swap_type() is among SWP_MIGRATION_READ, SWP_MIGRATION_WRITE and SWP_HWPOISON.
> All these types >= MAX_SWAPFILES, exactly what is asserted with non_swap_entry().
> 
> > 
> > Hence remove the unnecessary non_swap_entry() in is_hugetlb_entry_migration()
> > and is_hugetlb_entry_hwpoisoned() to simplify code.
> > 
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> > Reviewed-by: David Hildenbrand <david@redhat.com>
> > ---
> >  mm/hugetlb.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 3569e731e66b..c14837854392 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -3748,7 +3748,7 @@ bool is_hugetlb_entry_migration(pte_t pte)
> >  	if (huge_pte_none(pte) || pte_present(pte))
> >  		return false;
> >  	swp = pte_to_swp_entry(pte);
> > -	if (non_swap_entry(swp) && is_migration_entry(swp))
> > +	if (is_migration_entry(swp))
> >  		return true;
> >  	else
> >  		return false;
> > @@ -3761,7 +3761,7 @@ static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
> >  	if (huge_pte_none(pte) || pte_present(pte))
> >  		return false;
> >  	swp = pte_to_swp_entry(pte);
> > -	if (non_swap_entry(swp) && is_hwpoison_entry(swp))
> > +	if (is_hwpoison_entry(swp))
> >  		return true;
> >  	else
> >  		return false;
> > 
> 
> It would be better if the commit message contains details about
> the existing redundant check. But either way.

Thanks for your advice. Do you think updating the log as below is OK?

~~~~~~~~
If a swap entry tests positive for either is_[migration|hwpoison]_entry(), then
its swap_type() is among SWP_MIGRATION_READ, SWP_MIGRATION_WRITE and SWP_HWPOISON.
All these types >= MAX_SWAPFILES, exactly what is asserted with non_swap_entry().

So the checking non_swap_entry() in is_hugetlb_entry_migration() and
is_hugetlb_entry_hwpoisoned() is redundant.

Let's remove it to optimize code.
~~~~~~~~

Thanks
Baoquan
Anshuman Khandual July 23, 2020, 8:52 a.m. UTC | #3 
On 07/23/2020 11:44 AM, Baoquan He wrote:
> On 07/23/20 at 10:36am, Anshuman Khandual wrote:
>>
>>
>> On 07/23/2020 08:52 AM, Baoquan He wrote:
>>> The checking is_migration_entry() and is_hwpoison_entry() are stricter
>>> than non_swap_entry(), means they have covered the conditional check
>>> which non_swap_entry() is doing.
>>
>> They are no stricter as such but implicitly contains non_swap_entry() in itself.
>> If a swap entry tests positive for either is_[migration|hwpoison]_entry(), then
>> its swap_type() is among SWP_MIGRATION_READ, SWP_MIGRATION_WRITE and SWP_HWPOISON.
>> All these types >= MAX_SWAPFILES, exactly what is asserted with non_swap_entry().
>>
>>>
>>> Hence remove the unnecessary non_swap_entry() in is_hugetlb_entry_migration()
>>> and is_hugetlb_entry_hwpoisoned() to simplify code.
>>>
>>> Signed-off-by: Baoquan He <bhe@redhat.com>
>>> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
>>> Reviewed-by: David Hildenbrand <david@redhat.com>
>>> ---
>>>  mm/hugetlb.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>> index 3569e731e66b..c14837854392 100644
>>> --- a/mm/hugetlb.c
>>> +++ b/mm/hugetlb.c
>>> @@ -3748,7 +3748,7 @@ bool is_hugetlb_entry_migration(pte_t pte)
>>>  	if (huge_pte_none(pte) || pte_present(pte))
>>>  		return false;
>>>  	swp = pte_to_swp_entry(pte);
>>> -	if (non_swap_entry(swp) && is_migration_entry(swp))
>>> +	if (is_migration_entry(swp))
>>>  		return true;
>>>  	else
>>>  		return false;
>>> @@ -3761,7 +3761,7 @@ static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
>>>  	if (huge_pte_none(pte) || pte_present(pte))
>>>  		return false;
>>>  	swp = pte_to_swp_entry(pte);
>>> -	if (non_swap_entry(swp) && is_hwpoison_entry(swp))
>>> +	if (is_hwpoison_entry(swp))
>>>  		return true;
>>>  	else
>>>  		return false;
>>>
>>
>> It would be better if the commit message contains details about
>> the existing redundant check. But either way.
> 
> Thanks for your advice. Do you think updating the log as below is OK?
> 
> ~~~~~~~~
> If a swap entry tests positive for either is_[migration|hwpoison]_entry(), then
> its swap_type() is among SWP_MIGRATION_READ, SWP_MIGRATION_WRITE and SWP_HWPOISON.
> All these types >= MAX_SWAPFILES, exactly what is asserted with non_swap_entry().
> 
> So the checking non_swap_entry() in is_hugetlb_entry_migration() and
> is_hugetlb_entry_hwpoisoned() is redundant.
> 
> Let's remove it to optimize code.
> ~~~~~~~~

Something like above would be good.
diff mbox series

Patch

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3569e731e66b..c14837854392 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3748,7 +3748,7 @@  bool is_hugetlb_entry_migration(pte_t pte)
 	if (huge_pte_none(pte) || pte_present(pte))
 		return false;
 	swp = pte_to_swp_entry(pte);
-	if (non_swap_entry(swp) && is_migration_entry(swp))
+	if (is_migration_entry(swp))
 		return true;
 	else
 		return false;
@@ -3761,7 +3761,7 @@  static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
 	if (huge_pte_none(pte) || pte_present(pte))
 		return false;
 	swp = pte_to_swp_entry(pte);
-	if (non_swap_entry(swp) && is_hwpoison_entry(swp))
+	if (is_hwpoison_entry(swp))
 		return true;
 	else
 		return false;