linux-kernel - Re: [PATCH] Code style fix for open

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Date:	Thu, 04 Oct 2007 13:35:20 -0400
From:	Casey Dahlin <cjdahlin@...u.edu>
To:	Christoph Hellwig <hch@...radead.org>,
	Casey Dahlin <cjdahlin@...u.edu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Code style fix for open_exec

Christoph Hellwig wrote:
> On Wed, Oct 03, 2007 at 10:40:25PM -0400, Casey Dahlin wrote:
>   
>> From d2a6c5d29dc34cfea892124ab72b4eb55d2f8a80 Mon Sep 17 00:00:00 2001
>> From: Casey Dahlin <cjdahlin@...u.edu>
>> Date: Wed, 3 Oct 2007 22:01:49 -0400
>> Subject: [PATCH] Code style fix for open_exec
>>
>> Fix a horribly mangled 5 level indent and severe abuse of goto in the 
>> open_exec
>> function.
>>     
>
> While the function is not nice your version makes it even worse.
>   
    Ouch :) I don't think I did so bad.
> Try this one instead which has been in my pending testing tree for a while:
>   
Pretty much all of the stylistic changes were recommended to me already 
off list by Joe Perches. I have that in my branch now, and was waiting 
on any further feedback before resubmitting. There's a couple of things 
here though (particularly the unlikelys) that are worth having. This is 
the better code.
>
>
> Index: linux-2.6/fs/exec.c
> ===================================================================
> --- linux-2.6.orig/fs/exec.c	2007-09-16 20:29:01.000000000 +0200
> +++ linux-2.6/fs/exec.c	2007-09-16 20:29:56.000000000 +0200
> @@ -669,41 +669,55 @@ EXPORT_SYMBOL(setup_arg_pages);
>  
>  #endif /* CONFIG_MMU */
>  
> +/**
> + * open_exec - open file for execution
> + * @name:	filename to open
> + *
> + * Open the file pointed to by @filename in the current namespace
> + * for execution.  Error out if the file is not a regular file or
> + * this mount does not allow executing files on it.
> + */
>  struct file *open_exec(const char *name)
>  {
>  	struct nameidata nd;
> -	int err;
>  	struct file *file;
> +	int err;
>  
> -	err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd, FMODE_READ|FMODE_EXEC);
> -	file = ERR_PTR(err);
> +	err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd,
> +				FMODE_READ|FMODE_EXEC);
> +	if (unlikely(err))
> +		goto out;
>  
> -	if (!err) {
> -		struct inode *inode = nd.dentry->d_inode;
> -		file = ERR_PTR(-EACCES);
> -		if (!(nd.mnt->mnt_flags & MNT_NOEXEC) &&
> -		    S_ISREG(inode->i_mode)) {
> -			int err = vfs_permission(&nd, MAY_EXEC);
> -			file = ERR_PTR(err);
> -			if (!err) {
> -				file = nameidata_to_filp(&nd, O_RDONLY);
> -				if (!IS_ERR(file)) {
> -					err = deny_write_access(file);
> -					if (err) {
> -						fput(file);
> -						file = ERR_PTR(err);
> -					}
> -				}
> -out:
> -				return file;
> -			}
> -		}
> -		release_open_intent(&nd);
> -		path_release(&nd);
> +	err = -EACCES;
> +	if (unlikely(nd.mnt->mnt_flags & MNT_NOEXEC))
> +		goto out_path_release;
> +	if (unlikely(!S_ISREG(nd.dentry->d_inode->i_mode)))
> +		goto out_path_release;
> +
> +	err = vfs_permission(&nd, MAY_EXEC);
> +	if (unlikely(err))
> +		goto out_path_release;
> +
> +	file = nameidata_to_filp(&nd, O_RDONLY);
> +	if (unlikely(IS_ERR(file))) {
> +		err = PTR_ERR(file);
> +		goto out;
> +	}
> +
> +	err = deny_write_access(file);
> +	if (unlikely(err)) {
> +		fput(file);
> +		goto out;
>  	}
> -	goto out;
> -}
>  
> +	return file;
> +
> + out_path_release:
> +	release_open_intent(&nd);
> +	path_release(&nd);
> + out:
> +	return ERR_PTR(err);
> +}
>  EXPORT_SYMBOL(open_exec);
>  
>  int kernel_read(struct file *file, unsigned long offset,
> -
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