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

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Date:	Thu, 23 Aug 2012 10:54:44 +0200
From:	Marco Stornelli <marco.stornelli@...il.com>
To:	Cyrill Gorcunov <gorcunov@...nvz.org>
CC:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...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>,
	James Bottomley <jbottomley@...allels.com>,
	Matthew Helsley <matt.helsley@...il.com>
Subject: Re: [patch 4/8] fs, exportfs: Add export_encode_inode_fh helper

Il 23/08/2012 10:06, Cyrill Gorcunov ha scritto:
> On Wed, Aug 22, 2012 at 11:19:07AM +0530, Aneesh Kumar K.V wrote:
>> Pavel Emelyanov <xemul@...allels.com> writes:
>>
>>> Why? For e.g. ext4 you can construct a handle in userspace and open by
>>> it.
>>
>> open_by_handle use exportfs_decode_fh which use file system specific
>> fh_to_dentry
>>
>> foe ext4 we require a generation number
>>
>> 		inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
>>
>
> Hi Aneesh, yes we need i_generation but for ext3/4 it could be
> fetched with ioctl as far as i see.
>
>> For brtfs
>>
>> 	objectid = fid->objectid;
>> 	root_objectid = fid->root_objectid;
>> 	generation = fid->gen;
>>
>> 	return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
>
> For btrfs it become more complex. But still the last version I'm about
> to send for review today (once everything get tested) will provide
> fhandle carried with inotify mark _and_ inode number and device. This
> information should be enough for us. After all having inode and device
> should allow us to figure out the fs used on inotify target.
>
> 	Cyrill
> --

Sorry if it's a really stupid question but I didn't follow deeply the 
thread. How can you provide a device if the fs is mounted on "none" (ex 
tmpfs)? In this case you can't associate device <=> fs, because you 
haven't got a /dev/something.

Marco
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