linux-kernel - Re: [PATCH 1/1] mm/vmalloc.c: eliminate extra loop in pcpu_get_vm

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Date:	Fri, 18 Nov 2011 11:59:55 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Kautuk Consul <consul.kautuk@...il.com>
Cc:	Joe Perches <joe@...ches.com>,
	David Rientjes <rientjes@...gle.com>,
	Minchan Kim <minchan.kim@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] mm/vmalloc.c: eliminate extra loop in
 pcpu_get_vm_areas error path

On Fri, 18 Nov 2011 17:13:50 +0530
Kautuk Consul <consul.kautuk@...il.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@...il.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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