linux-kernel - Re: [PATCH 2/3] xen-scsiback: One function call less in scsiback_device

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Date:	Mon, 18 Jul 2016 07:11:36 +0200
From:	Juergen Gross <jgross@...e.com>
To:	SF Markus Elfring <elfring@...rs.sourceforge.net>,
	xen-devel@...ts.xenproject.org, linux-scsi@...r.kernel.org,
	David Vrabel <david.vrabel@...rix.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org,
	Julia Lawall <julia.lawall@...6.fr>
Subject: Re: [PATCH 2/3] xen-scsiback: One function call less in
 scsiback_device_action() after error detection

On 16/07/16 22:23, SF Markus Elfring wrote:
> From: Markus Elfring <elfring@...rs.sourceforge.net>
> Date: Sat, 16 Jul 2016 21:42:42 +0200
> 
> The kfree() function was called in one case by the
> scsiback_device_action() function during error handling
> even if the passed variable "tmr" contained a null pointer.
> 
> Adjust jump targets according to the Linux coding style convention.
> 
> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
> ---
>  drivers/xen/xen-scsiback.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
> index 4a48c06..7612bc9 100644
> --- a/drivers/xen/xen-scsiback.c
> +++ b/drivers/xen/xen-scsiback.c
> @@ -606,7 +606,7 @@ static void scsiback_device_action(struct vscsibk_pend *pending_req,
>  	tmr = kzalloc(sizeof(struct scsiback_tmr), GFP_KERNEL);
>  	if (!tmr) {
>  		target_put_sess_cmd(se_cmd);
> -		goto err;
> +		goto do_resp;
>  	}

Hmm, I'm not convinced this is an improvement.

I'd rather rename the new error label to "put_cmd" and get rid of the
braces in above if statement:

-	if (!tmr) {
-		target_put_sess_cmd(se_cmd);
-		goto err;
-	}
+	if (!tmr)
+		goto put_cmd;

and then in the error path:

-err:
+put_cmd:
+	target_put_sess_cmd(se_cmd);
+free_tmr:
	kfree(tmr);


Juergen

>  
>  	init_waitqueue_head(&tmr->tmr_wait);
> @@ -616,7 +616,7 @@ static void scsiback_device_action(struct vscsibk_pend *pending_req,
>  			       unpacked_lun, tmr, act, GFP_KERNEL,
>  			       tag, TARGET_SCF_ACK_KREF);
>  	if (rc)
> -		goto err;
> +		goto free_tmr;
>  
>  	wait_event(tmr->tmr_wait, atomic_read(&tmr->tmr_complete));
>  
> @@ -626,8 +626,9 @@ static void scsiback_device_action(struct vscsibk_pend *pending_req,
>  	scsiback_do_resp_with_sense(NULL, err, 0, pending_req);
>  	transport_generic_free_cmd(&pending_req->se_cmd, 1);
>  	return;
> -err:
> +free_tmr:
>  	kfree(tmr);
> +do_resp:
>  	scsiback_do_resp_with_sense(NULL, err, 0, pending_req);
>  }
>  
>