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

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Message-ID: <20120816153559.GD13382@moon>
Date:	Thu, 16 Aug 2012 19:35:59 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	Pavel Emelyanov <xemul@...allels.com>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	James Bottomley <jbottomley@...allels.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Helsley <matt.helsley@...il.com>
Subject: Re: [patch 4/8] fs, exportfs: Add export_encode_inode_fh helper

On Thu, Aug 16, 2012 at 07:06:18PM +0400, Pavel Emelyanov wrote:
> On 08/16/2012 06:55 PM, Al Viro wrote:
> > On Thu, Aug 16, 2012 at 06:48:35PM +0400, Cyrill Gorcunov wrote:
> > 
> >>> Good luck doing that with e.g. VFAT...  And then there's such thing
> >>> as filesystems that don't have ->encode_fh() for a lot of very good
> >>
> >> Wait, Al, it seems I messed up. If some fs has no encode_fh() implemented
> >> the default encoding with FILEID_INO32_GEN_PARENT will be used for that.
> > 
> > ... which doesn't work for a lot of filesystems.  Not if you want to be
> > able to decode the result afterwards and get something useful out of
> > that.  Trying to implement ->fh_to_dentry(), especially with fhandle
> > generated by inode alone is going to be really interesting for a bunch
> > of stuff...
> > .
> > 
> 
> Hm... Then I suppose the best we can do is -- show in a fdinfo file the inode
> number, device where it is and a filehandle _iff_ provided by a filesystem.
> For fanotify/dnotify -- only a path.

For notifications on mount points it's not a problem (we already do that

+		ret = seq_printf(m, "fanotify mnt_id: %8x mask: %8x ignored_mask: %8x\n",
+				 mnt->mnt_id, mark->mask, mark->ignored_mask);

printing inode number and device it's easy as well. Fetching the path is not
obvious for me since inotify carries inodes only. To generate path I would
have to obtain dentry from inode I suppose, that's what you mean?

	Cyrill
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