linux-kernel - Re: [patch 4/8] fs, exportfs: Add export_encode_inode

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Message-ID: <20120815204546.GC25062@fieldses.org>
Date:	Wed, 15 Aug 2012 16:45:46 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Cyrill Gorcunov <gorcunov@...nvz.org>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Al Viro <viro@...iv.linux.org.uk>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	James Bottomley <jbottomley@...allels.com>,
	Matthew Helsley <matt.helsley@...il.com>
Subject: Re: [patch 4/8] fs, exportfs: Add export_encode_inode_fh helper

On Wed, Aug 15, 2012 at 01:21:20PM +0400, Cyrill Gorcunov wrote:
> To provide fsnotify object inodes being watched without
> binding to alphabetical path we need to encode them with
> exportfs help. This patch adds a helper which operates
> with plain inodes directly.

I don't get it--this seems like a really roundabout way to get inode and
generation number, if that's all you want.

On the other hand, if you want a real filehandle then wouldn't you want
to e.g. call the filesystem's ->encode_fh() if necessary, as
exportfs_encode_fh() does?

--b.

> 
> Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
> Acked-by: Pavel Emelyanov <xemul@...allels.com>
> CC: Al Viro <viro@...IV.linux.org.uk>
> CC: Alexey Dobriyan <adobriyan@...il.com>
> CC: Andrew Morton <akpm@...ux-foundation.org>
> CC: James Bottomley <jbottomley@...allels.com>
> ---
>  fs/exportfs/expfs.c      |   19 +++++++++++++++++++
>  include/linux/exportfs.h |    2 ++
>  2 files changed, 21 insertions(+)
> 
> Index: linux-2.6.git/fs/exportfs/expfs.c
> ===================================================================
> --- linux-2.6.git.orig/fs/exportfs/expfs.c
> +++ linux-2.6.git/fs/exportfs/expfs.c
> @@ -302,6 +302,25 @@ out:
>  	return error;
>  }
>  
> +int export_encode_inode_fh(struct inode *inode, struct fid *fid, int *max_len)
> +{
> +	int len = *max_len;
> +	int type = FILEID_INO32_GEN;
> +
> +	if (len < 2) {
> +		*max_len = 2;
> +		return 255;
> +	}
> +
> +	len = 2;
> +	fid->i32.ino = inode->i_ino;
> +	fid->i32.gen = inode->i_generation;
> +	*max_len = len;
> +
> +	return type;
> +}
> +EXPORT_SYMBOL_GPL(export_encode_inode_fh);
> +
>  /**
>   * export_encode_fh - default export_operations->encode_fh function
>   * @inode:   the object to encode
> Index: linux-2.6.git/include/linux/exportfs.h
> ===================================================================
> --- linux-2.6.git.orig/include/linux/exportfs.h
> +++ linux-2.6.git/include/linux/exportfs.h
> @@ -177,6 +177,8 @@ struct export_operations {
>  	int (*commit_metadata)(struct inode *inode);
>  };
>  
> +extern int export_encode_inode_fh(struct inode *inode, struct fid *fid, int *max_len);
> +
>  extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
>  	int *max_len, int connectable);
>  extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
> 
> --
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