linux-kernel - Re: [PATCH 08/24] make access() use mnt check

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Message-ID: <20070919173216.GH20917@infradead.org>
Date:	Wed, 19 Sep 2007 18:32:16 +0100
From:	Christoph Hellwig <hch@...radead.org>
To:	Dave Hansen <haveblue@...ibm.com>
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org, hch@...radead.org
Subject: Re: [PATCH 08/24] make access() use mnt check

On Mon, Sep 17, 2007 at 11:27:28AM -0700, Dave Hansen wrote:
>  	if(res || !(mode & S_IWOTH) ||
>  	   special_file(nd.dentry->d_inode->i_mode))
>  		goto out_path_release;
> -
> -	if(IS_RDONLY(nd.dentry->d_inode))
> +	/*
> +	 * This is a rare case where using __mnt_is_readonly()
> +	 * is OK without a mnt_want/drop_write() pair.  Since
> +	 * no actual write to the fs is performed here, we do
> +	 * not need to telegraph to that to anyone.
> +	 *
> +	 * By doing this, we accept that this access is
> +	 * inherently racy and know that the fs may change
> +	 * state before we even see this result.
> +	 */
> +	if (__mnt_is_readonly(nd.mnt))
>  		res = -EROFS;

Ok.
-
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