linux-kernel - Re: [PATCH] Change paride driver to use unlocked

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Date:	Wed, 9 Jan 2008 08:06:20 +0000
From:	Christoph Hellwig <hch@...radead.org>
To:	Nikanth Karthikesan <knikanth@...e.de>
Cc:	grant@...que.net, tim@...erelk.net, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] Change paride driver to use unlocked_ioctl instead of
	ioctl

On Thu, Jan 10, 2008 at 11:44:20AM +0530, Nikanth Karthikesan wrote:
> -static int pt_ioctl(struct inode *inode, struct file *file,
> -	 unsigned int cmd, unsigned long arg)
> +static long pt_ioctl(struct file *file, unsigned int cmd, unsigned long
> arg)

this looks line-wrapper by your mailer.

> -		if (copy_from_user(&mtop, p, sizeof(struct mtop)))
> +		if (copy_from_user(&mtop, p, sizeof(struct mtop))) {
> +			unlock_kernel();
>  			return -EFAULT;
> +		}
> 
>  		switch (mtop.mt_op) {
> 
>  		case MTREW:
>  			pt_rewind(tape);
> +			unlock_kernel();

It's generally considered good style to only have as few as possible
return values.  And this is especially important when returning from
a section that's under a lock.  So in this case it would be much better
if you changes this function to have a local 'int error' variable
and then just do

	error = -EFOO;
	goto out_unlock;

wherever you have an early return with the end of the function looking
like


out_unlock:
	unlock_kernel();
	return error;
--
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