linux-kernel - Re: [PATCH 3/3] have pipefs ensure i_ino uniqueness by calling iunique and hashing the inode

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Date:	Wed, 10 Jan 2007 21:24:48 +0000
From:	Christoph Hellwig <hch@...radead.org>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	esandeen@...hat.com, aviro@...hat.com, haveblue@...ibm.com
Subject: Re: [PATCH 3/3] have pipefs ensure i_ino uniqueness by calling iunique and hashing the inode

On Mon, Jan 08, 2007 at 03:47:17PM -0500, Jeff Layton wrote:
> This converts pipefs to use the new scheme. Here we're calling iunique to get
> a unique i_ino value for the new inode, and then hashing it afterward. We
> call iunique with a max_reserved value of 1 to avoid collision with the root
> inode.  Since the inode is now hashed, we need to take care that we end up in
> generic_delete_inode rather than generic_forget_inode or we'll create a nasty
> leak, so we clear_nlink when we destroy the pipe info.
> 
> I'm not certain that this is the right place to add the clear_nlink, though
> it does seem to work. I'm open to suggestions on a better place to put
> this, or of a better way to make sure that we end up with i_nlink == 0 at
> iput time.

You should Cc Dave Hansen as he's did the nlink helpers and works on
the per-mount readonly code that requires them.

> Signed-off-by: Jeff Layton <jlayton@...hat.com>
> 
> diff --git a/fs/pipe.c b/fs/pipe.c
> index 68090e8..1d44ff0 100644
> --- a/fs/pipe.c
> +++ b/fs/pipe.c
> @@ -825,6 +825,7 @@ void free_pipe_info(struct inode *inode)
>  {
>  	__free_pipe_info(inode->i_pipe);
>  	inode->i_pipe = NULL;
> +	clear_nlink(inode);
>  }
>  
>  static struct vfsmount *pipe_mnt __read_mostly;
> @@ -871,6 +872,8 @@ static struct inode * get_pipe_inode(void)
>  	inode->i_uid = current->fsuid;
>  	inode->i_gid = current->fsgid;
>  	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
> +	inode->i_ino = iunique(pipe_mnt->mnt_sb, 1);
> +	insert_inode_hash(inode);
>  
>  	return inode;
>  
> -
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