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

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Date:	Tue, 21 Aug 2012 16:40:16 +0400
From:	Pavel Emelyanov <xemul@...allels.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
CC:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	"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>,
	James Bottomley <jbottomley@...allels.com>,
	Matthew Helsley <matt.helsley@...il.com>
Subject: Re: [patch 4/8] fs, exportfs: Add export_encode_inode_fh helper

>>>> Al, Bruce, Aneesh,
>>>>
>>>> What if we calculate the handle at the time we do have struct path at hands (i.e.
>>>> when we create the inotify) and store it on the inotify structure purely to be 
>>>> shown later in proc. Would that be acceptable?
>>>
>>> Was it the lack of a dentry that was really the problem?  I thought it
>>> was just the fact that not all filesystems support filehandles.
>>
>> Initial problem -- we don't know what is being watched by an inotify fd.
>>
>> Having a dentry somewhere was the 1st attempt to solve this -- keep a path
>> in inotify and show it when required. It doesn't work since holding a ref on
>> path changes the behavior of watched inode (we cannot rename/unlink/remount
>> it the same way as we could before patching the kernel).
> 
> OK.  So if you don't mind the fact that there are filesystems with
> inotify support but not filehandle support, then I think generating a
> filehandle early as you describe would work.  I guess it's a little more
> memory per watched inode.

Great! Thanks, Bruce, we'll rework the patch accordingly :)

> --b.
> .
> 

Thanks,
Pavel
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