From: Arnd Bergmann <arnd@arndb.de>
To: "Stoyan Gaydarov" <stoyboyker@gmail.com>
Subject: Re: [PATCH] ioctl conversion
Date: Fri, 11 Jul 2008 10:08:20 +0200
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On Friday 11 July 2008, Stoyan Gaydarov wrote:
> - ? ? ? if (_IOC_TYPE(cmd) != SNAPSHOT_IOC_MAGIC)
> + ? ? ? lock_kernel();
> +
> + ? ? ? if (_IOC_TYPE(cmd) != SNAPSHOT_IOC_MAGIC) {
> + ? ? ? ? ? ? ? unlock_kernel();
> ? ? ? ? ? ? ? ? return -ENOTTY;
> - ? ? ? if (_IOC_NR(cmd) > SNAPSHOT_IOC_MAXNR)
> + ? ? ? }
> + ? ? ? if (_IOC_NR(cmd) > SNAPSHOT_IOC_MAXNR) {
> + ? ? ? ? ? ? ? unlock_kernel();
> ? ? ? ? ? ? ? ? return -ENOTTY;
> - ? ? ? if (!capable(CAP_SYS_ADMIN))
> + ? ? ? }
> + ? ? ? if (!capable(CAP_SYS_ADMIN)) {
> + ? ? ? ? ? ? ? unlock_kernel();
> ? ? ? ? ? ? ? ? return -EPERM;
> + ? ? ? }
> 
> ? ? ? ? data = filp->private_data;

The more common way to express this is to end the function with

out:
	unlock_kernel();
	return ret;
}

and then jump to that label in the error case. This makes it
much easier to verify that you haven't missed a cased.

	Arnd <><
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