[PATCH] maple_tree: not necessary to filter MAPLE_PARENT_ROOT since it is not a root

[PATCH] maple_tree: not necessary to filter MAPLE_PARENT_ROOT since it is not a root

[Wei Yang]

Root node is return at the beginning, so we are sure bit 0 is not set.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
CC: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
 lib/maple_tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 9aad98c24f3e..f8c4755e7c75 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -436,7 +436,7 @@ enum maple_type mte_parent_enum(struct maple_enode *p_enode,
 		return 0; /* Validated in the caller. */
 
 	p_type &= MAPLE_NODE_MASK;
-	p_type = p_type & ~(MAPLE_PARENT_ROOT | mte_parent_slot_mask(p_type));
+	p_type = p_type & ~mte_parent_slot_mask(p_type);
 
 	switch (p_type) {
 	case MAPLE_PARENT_RANGE64: /* or MAPLE_PARENT_ARANGE64 */
-- 
2.33.1

Re: [PATCH] maple_tree: not necessary to filter MAPLE_PARENT_ROOT since it is not a root

[Liam Howlett]

* Wei Yang <richard.weiyang@gmail.com> [221112 19:56]:
> Root node is return at the beginning, so we are sure bit 0 is not set.
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> CC: Liam R. Howlett <Liam.Howlett@Oracle.com>
> ---
>  lib/maple_tree.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index 9aad98c24f3e..f8c4755e7c75 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -436,7 +436,7 @@ enum maple_type mte_parent_enum(struct maple_enode *p_enode,
>  		return 0; /* Validated in the caller. */
>  
>  	p_type &= MAPLE_NODE_MASK;
> -	p_type = p_type & ~(MAPLE_PARENT_ROOT | mte_parent_slot_mask(p_type));
> +	p_type = p_type & ~mte_parent_slot_mask(p_type);

I think there is a larger cleanup that can be done here.  It looks like
mte_parent_enum() is called from one location and that location is a
wrapper.

The check for the root bit should also probably trigger a WARN_ON() and
still return 0.  I don't think the callers are doing enough to validate
it - although they should never reach this function with a root node.
And, in fact, I am not doing enough in the test code since I didn't
guard this correctly in the verification of the parent slot before
calling this function.

Thanks for pointing this out.  I will send out a patch to clean this up
shortly.

>  
>  	switch (p_type) {
>  	case MAPLE_PARENT_RANGE64: /* or MAPLE_PARENT_ARANGE64 */
> -- 
> 2.33.1
> 

Re: [PATCH] maple_tree: not necessary to filter MAPLE_PARENT_ROOT since it is not a root

[Liam Howlett]

* Liam R. Howlett <Liam.Howlett@Oracle.com> [221115 09:29]:
> * Wei Yang <richard.weiyang@gmail.com> [221112 19:56]:
> > Root node is return at the beginning, so we are sure bit 0 is not set.
> > 
> > Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> > CC: Liam R. Howlett <Liam.Howlett@Oracle.com>
> > ---
> >  lib/maple_tree.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> > index 9aad98c24f3e..f8c4755e7c75 100644
> > --- a/lib/maple_tree.c
> > +++ b/lib/maple_tree.c
> > @@ -436,7 +436,7 @@ enum maple_type mte_parent_enum(struct maple_enode *p_enode,
> >  		return 0; /* Validated in the caller. */
> >  
> >  	p_type &= MAPLE_NODE_MASK;
> > -	p_type = p_type & ~(MAPLE_PARENT_ROOT | mte_parent_slot_mask(p_type));
> > +	p_type = p_type & ~mte_parent_slot_mask(p_type);
> 
> I think there is a larger cleanup that can be done here.  It looks like
> mte_parent_enum() is called from one location and that location is a
> wrapper.
> 
> The check for the root bit should also probably trigger a WARN_ON() and
> still return 0.  I don't think the callers are doing enough to validate
> it - although they should never reach this function with a root node.
> And, in fact, I am not doing enough in the test code since I didn't
> guard this correctly in the verification of the parent slot before
> calling this function.
> 
> Thanks for pointing this out.  I will send out a patch to clean this up
> shortly.

On second thought, I will hold off for the 6.2 merge window for this to
go upstream.

Thanks,
Liam

Re: [PATCH] maple_tree: not necessary to filter MAPLE_PARENT_ROOT since it is not a root

[Wei Yang]

On Tue, Nov 15, 2022 at 02:31:15PM +0000, Liam Howlett wrote:
>* Wei Yang <richard.weiyang@gmail.com> [221112 19:56]:
>> Root node is return at the beginning, so we are sure bit 0 is not set.
>> 
>> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> CC: Liam R. Howlett <Liam.Howlett@Oracle.com>
>> ---
>>  lib/maple_tree.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
>> index 9aad98c24f3e..f8c4755e7c75 100644
>> --- a/lib/maple_tree.c
>> +++ b/lib/maple_tree.c
>> @@ -436,7 +436,7 @@ enum maple_type mte_parent_enum(struct maple_enode *p_enode,
>>  		return 0; /* Validated in the caller. */
>>  
>>  	p_type &= MAPLE_NODE_MASK;
>> -	p_type = p_type & ~(MAPLE_PARENT_ROOT | mte_parent_slot_mask(p_type));
>> +	p_type = p_type & ~mte_parent_slot_mask(p_type);
>
>I think there is a larger cleanup that can be done here.  It looks like
>mte_parent_enum() is called from one location and that location is a
>wrapper.
>
>The check for the root bit should also probably trigger a WARN_ON() and
>still return 0.  I don't think the callers are doing enough to validate
>it - although they should never reach this function with a root node.
>And, in fact, I am not doing enough in the test code since I didn't
>guard this correctly in the verification of the parent slot before
>calling this function.
>
>Thanks for pointing this out.  I will send out a patch to clean this up
>shortly.
>

Yep, look forward your cleanup.

While I have a question here. We get 4 types in maple_type, here we just
return two of them. This means the other two is not possible to be parent
node, right?

>>  
>>  	switch (p_type) {
>>  	case MAPLE_PARENT_RANGE64: /* or MAPLE_PARENT_ARANGE64 */
>> -- 
>> 2.33.1
>> 

-- 
Wei Yang
Help you, Help me