[PATCH] net/netfilter/x_tables.c: use __seq_open_private()

[PATCH] net/netfilter/x_tables.c: use __seq_open_private()

[Rob Jones]

Reduce boilerplate code by using __seq_open_private() instead of seq_open()
in xt_match_open() and xt_target_open().

Signed-off-by: Rob Jones <rob.jones@codethink.co.uk>
---

This patch uses an existing variant of seq_open() to reduce the kernel code
size.

The only significant variation from the pre-existing code is the fact that
__seq_open_private() calls kzalloc() rather than kmalloc(), which could
conceivably have an impact on timing.

** I am sending this to the developers' list now. I failed to transcribe
the full cc list output by get-maintainer.pl, mea culpa, mea maxima culpa **

 net/netfilter/x_tables.c |   30 ++++--------------------------
 1 file changed, 4 insertions(+), 26 deletions(-)

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 227aa11..89aa680 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -1137,22 +1137,11 @@ static const struct seq_operations xt_match_seq_ops = {
 
 static int xt_match_open(struct inode *inode, struct file *file)
 {
-	struct seq_file *seq;
 	struct nf_mttg_trav *trav;
-	int ret;
-
-	trav = kmalloc(sizeof(*trav), GFP_KERNEL);
-	if (trav == NULL)
+	trav = __seq_open_private(file, &xt_match_seq_ops, sizeof(*trav));
+	if (!trav)
 		return -ENOMEM;
 
-	ret = seq_open(file, &xt_match_seq_ops);
-	if (ret < 0) {
-		kfree(trav);
-		return ret;
-	}
-
-	seq = file->private_data;
-	seq->private = trav;
 	trav->nfproto = (unsigned long)PDE_DATA(inode);
 	return 0;
 }
@@ -1201,22 +1190,11 @@ static const struct seq_operations xt_target_seq_ops = {
 
 static int xt_target_open(struct inode *inode, struct file *file)
 {
-	struct seq_file *seq;
 	struct nf_mttg_trav *trav;
-	int ret;
-
-	trav = kmalloc(sizeof(*trav), GFP_KERNEL);
-	if (trav == NULL)
+	trav = __seq_open_private(file, &xt_target_seq_ops, sizeof(*trav));
+	if (!trav)
 		return -ENOMEM;
 
-	ret = seq_open(file, &xt_target_seq_ops);
-	if (ret < 0) {
-		kfree(trav);
-		return ret;
-	}
-
-	seq = file->private_data;
-	seq->private = trav;
 	trav->nfproto = (unsigned long)PDE_DATA(inode);
 	return 0;
 }
-- 
1.7.10.4

Re: [PATCH] net/netfilter/x_tables.c: use __seq_open_private()

[Pablo Neira Ayuso]

On Fri, Sep 19, 2014 at 11:27:51AM +0100, Rob Jones wrote:
> Reduce boilerplate code by using __seq_open_private() instead of seq_open()
> in xt_match_open() and xt_target_open().
> 
> Signed-off-by: Rob Jones <rob.jones@codethink.co.uk>
> ---
> 
> This patch uses an existing variant of seq_open() to reduce the kernel code
> size.

Less code to maintain, good.

> The only significant variation from the pre-existing code is the fact that
> __seq_open_private() calls kzalloc() rather than kmalloc(), which could
> conceivably have an impact on timing.

I think you can skip

        trav->class = MTTG_TRAV_INIT;

too, now that trav is set to zero.

Re: [PATCH] net/netfilter/x_tables.c: use __seq_open_private()

[Rob Jones]

Would you like that change made and re-submitted? It's the work of
moments to do it.

I was only concentrating on not changing the logic so I didn't check on
whether and existing initialisation was made redundant.

On 23/09/14 15:02, Pablo Neira Ayuso wrote:
> On Fri, Sep 19, 2014 at 11:27:51AM +0100, Rob Jones wrote:
>> Reduce boilerplate code by using __seq_open_private() instead of seq_open()
>> in xt_match_open() and xt_target_open().
>>
>> Signed-off-by: Rob Jones <rob.jones@codethink.co.uk>
>> ---
>>
>> This patch uses an existing variant of seq_open() to reduce the kernel code
>> size.
>
> Less code to maintain, good.
>
>> The only significant variation from the pre-existing code is the fact that
>> __seq_open_private() calls kzalloc() rather than kmalloc(), which could
>> conceivably have an impact on timing.
>
> I think you can skip
>
>          trav->class = MTTG_TRAV_INIT;
>
> too, now that trav is set to zero.
>
>
>

-- 
Rob Jones
Codethink Ltd
mailto:rob.jones@codethink.co.uk
tel:+44 161 236 5575

Re: [PATCH] net/netfilter/x_tables.c: use __seq_open_private()

[Pablo Neira Ayuso]

On Tue, Sep 23, 2014 at 04:32:39PM +0100, Rob Jones wrote:
> Would you like that change made and re-submitted? It's the work of
> moments to do it.

Yes please, send us a v2. Thanks.

Re: [PATCH] net/netfilter/x_tables.c: use __seq_open_private()

[Rob Jones]

Will do.

On 23/09/14 16:36, Pablo Neira Ayuso wrote:
> On Tue, Sep 23, 2014 at 04:32:39PM +0100, Rob Jones wrote:
>> Would you like that change made and re-submitted? It's the work of
>> moments to do it.
>
> Yes please, send us a v2. Thanks.
>
>
>

-- 
Rob Jones
Codethink Ltd
mailto:rob.jones@codethink.co.uk
tel:+44 161 236 5575