[PATCH 1/1] mm/vmalloc.c: eliminate extra loop in pcpu_get_vm_areas error path

[PATCH 1/1] mm/vmalloc.c: eliminate extra loop in pcpu_get_vm_areas error path

[Kautuk Consul]

If either of the vas or vms arrays are not properly kzalloced,
then the code jumps to the err_free label.

The err_free label runs a loop to check and free each of the array
members of the vas and vms arrays which is not required for this
situation as none of the array members have been allocated till this
point.

Eliminate the extra loop we have to go through by introducing a new
label err_free2 and then jumping to it.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
---
 mm/vmalloc.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index b669aa6..1a0d4e2 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2352,7 +2352,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
 	vms = kzalloc(sizeof(vms[0]) * nr_vms, GFP_KERNEL);
 	vas = kzalloc(sizeof(vas[0]) * nr_vms, GFP_KERNEL);
 	if (!vas || !vms)
-		goto err_free;
+		goto err_free2;
 
 	for (area = 0; area < nr_vms; area++) {
 		vas[area] = kzalloc(sizeof(struct vmap_area), GFP_KERNEL);
@@ -2455,6 +2455,7 @@ err_free:
 		if (vms)
 			kfree(vms[area]);
 	}
+err_free2:
 	kfree(vas);
 	kfree(vms);
 	return NULL;
-- 
1.7.6

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Re: [PATCH 1/1] mm/vmalloc.c: eliminate extra loop in pcpu_get_vm_areas error path

[Andrew Morton]

On Fri, 18 Nov 2011 17:13:50 +0530
Kautuk Consul <consul.kautuk@gmail.com> wrote:

> If either of the vas or vms arrays are not properly kzalloced,
> then the code jumps to the err_free label.
> 
> The err_free label runs a loop to check and free each of the array
> members of the vas and vms arrays which is not required for this
> situation as none of the array members have been allocated till this
> point.
> 
> Eliminate the extra loop we have to go through by introducing a new
> label err_free2 and then jumping to it.
> 
> Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
> ---
>  mm/vmalloc.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index b669aa6..1a0d4e2 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2352,7 +2352,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
>  	vms = kzalloc(sizeof(vms[0]) * nr_vms, GFP_KERNEL);
>  	vas = kzalloc(sizeof(vas[0]) * nr_vms, GFP_KERNEL);
>  	if (!vas || !vms)
> -		goto err_free;
> +		goto err_free2;
>  
>  	for (area = 0; area < nr_vms; area++) {
>  		vas[area] = kzalloc(sizeof(struct vmap_area), GFP_KERNEL);
> @@ -2455,6 +2455,7 @@ err_free:
>  		if (vms)
>  			kfree(vms[area]);
>  	}
> +err_free2:
>  	kfree(vas);
>  	kfree(vms);
>  	return NULL;

Which means we can also do the below, yes?  (please check my homework!)

--- a/mm/vmalloc.c~mm-vmallocc-eliminate-extra-loop-in-pcpu_get_vm_areas-error-path-fix
+++ a/mm/vmalloc.c
@@ -2449,10 +2449,8 @@ found:
 
 err_free:
 	for (area = 0; area < nr_vms; area++) {
-		if (vas)
-			kfree(vas[area]);
-		if (vms)
-			kfree(vms[area]);
+		kfree(vas[area]);
+		kfree(vms[area]);
 	}
 err_free2:
 	kfree(vas);
_


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Re: [PATCH 1/1] mm/vmalloc.c: eliminate extra loop in pcpu_get_vm_areas error path

[kautuk.c @samsung.com]

Oh yes, I missed that out. :)

We should also do that.

Do you need me to redo this patch with this change ?
Although, I do notice that you seem to have already accepted this patch.


On Fri, Nov 18, 2011 at 2:59 PM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Fri, 18 Nov 2011 17:13:50 +0530
> Kautuk Consul <consul.kautuk@gmail.com> wrote:
>
>> If either of the vas or vms arrays are not properly kzalloced,
>> then the code jumps to the err_free label.
>>
>> The err_free label runs a loop to check and free each of the array
>> members of the vas and vms arrays which is not required for this
>> situation as none of the array members have been allocated till this
>> point.
>>
>> Eliminate the extra loop we have to go through by introducing a new
>> label err_free2 and then jumping to it.
>>
>> Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
>> ---
>>  mm/vmalloc.c |    3 ++-
>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>> index b669aa6..1a0d4e2 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -2352,7 +2352,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
>>       vms = kzalloc(sizeof(vms[0]) * nr_vms, GFP_KERNEL);
>>       vas = kzalloc(sizeof(vas[0]) * nr_vms, GFP_KERNEL);
>>       if (!vas || !vms)
>> -             goto err_free;
>> +             goto err_free2;
>>
>>       for (area = 0; area < nr_vms; area++) {
>>               vas[area] = kzalloc(sizeof(struct vmap_area), GFP_KERNEL);
>> @@ -2455,6 +2455,7 @@ err_free:
>>               if (vms)
>>                       kfree(vms[area]);
>>       }
>> +err_free2:
>>       kfree(vas);
>>       kfree(vms);
>>       return NULL;
>
> Which means we can also do the below, yes?  (please check my homework!)
>
> --- a/mm/vmalloc.c~mm-vmallocc-eliminate-extra-loop-in-pcpu_get_vm_areas-error-path-fix
> +++ a/mm/vmalloc.c
> @@ -2449,10 +2449,8 @@ found:
>
>  err_free:
>        for (area = 0; area < nr_vms; area++) {
> -               if (vas)
> -                       kfree(vas[area]);
> -               if (vms)
> -                       kfree(vms[area]);
> +               kfree(vas[area]);
> +               kfree(vms[area]);
>        }
>  err_free2:
>        kfree(vas);
> _
>
>
>

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Re: [PATCH 1/1] mm/vmalloc.c: eliminate extra loop in pcpu_get_vm_areas error path

[David Rientjes]

On Fri, 18 Nov 2011, Andrew Morton wrote:

> > If either of the vas or vms arrays are not properly kzalloced,
> > then the code jumps to the err_free label.
> > 
> > The err_free label runs a loop to check and free each of the array
> > members of the vas and vms arrays which is not required for this
> > situation as none of the array members have been allocated till this
> > point.
> > 
> > Eliminate the extra loop we have to go through by introducing a new
> > label err_free2 and then jumping to it.
> > 
> > Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
> > ---
> >  mm/vmalloc.c |    3 ++-
> >  1 files changed, 2 insertions(+), 1 deletions(-)
> > 
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index b669aa6..1a0d4e2 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2352,7 +2352,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
> >  	vms = kzalloc(sizeof(vms[0]) * nr_vms, GFP_KERNEL);
> >  	vas = kzalloc(sizeof(vas[0]) * nr_vms, GFP_KERNEL);
> >  	if (!vas || !vms)
> > -		goto err_free;
> > +		goto err_free2;
> >  
> >  	for (area = 0; area < nr_vms; area++) {
> >  		vas[area] = kzalloc(sizeof(struct vmap_area), GFP_KERNEL);
> > @@ -2455,6 +2455,7 @@ err_free:
> >  		if (vms)
> >  			kfree(vms[area]);
> >  	}
> > +err_free2:
> >  	kfree(vas);
> >  	kfree(vms);
> >  	return NULL;
> 
> Which means we can also do the below, yes?  (please check my homework!)
> 
> --- a/mm/vmalloc.c~mm-vmallocc-eliminate-extra-loop-in-pcpu_get_vm_areas-error-path-fix
> +++ a/mm/vmalloc.c
> @@ -2449,10 +2449,8 @@ found:
>  
>  err_free:
>  	for (area = 0; area < nr_vms; area++) {
> -		if (vas)
> -			kfree(vas[area]);
> -		if (vms)
> -			kfree(vms[area]);
> +		kfree(vas[area]);
> +		kfree(vms[area]);
>  	}
>  err_free2:
>  	kfree(vas);

On both patches:

Acked-by: David Rientjes <rientjes@google.com>

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