linux-kernel - Re: [PATCH] UDF: fix deadlock on inode being dropped

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Message-ID: <20070607143657.GB8393@cvg>
Date:	Thu, 7 Jun 2007 18:36:57 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Eric Sandeen <sandeen@...deen.net>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] UDF: fix deadlock on inode being dropped

[Jan Kara - Thu, Jun 07, 2007 at 04:41:21PM +0200]
| On Thu 07-06-07 17:54:58, Cyrill Gorcunov wrote:
| > [Jan Kara - Thu, Jun 07, 2007 at 11:36:07AM +0200]
| > |   Hi Cyrill!
| > | 
| > | On Wed 06-06-07 21:53:51, Cyrill Gorcunov wrote:
| > | > This patch prevents from deadlock on inode being dropped.
| > | > The deadlock is caused by inderect call of mark_inode_dirty()
| > | > within udf_drop_inode() but inode lock is already kept
| > | > by the kernel. So moving code from udf_drop_inode() to
| > | > udf_delete_inode() we save its functionality and avoid
| > | > deadlock.
| > |   The patch is wrong. You cannot truncate the extent just in delete_inode.
| > | That would lead to inodes with untruncated last extent on disk after
| > | unmounting, which is forbidden in the specification. You need to truncate
| > | the last extent whenever inode is being removed from memory or something
| > | like that... I'm already thinking how to do it and avoid calling
| > | mark_inode_dirty()...
| > | 
| > 
| > Arh, thanks... Jan, actually the reason I've moved the code into
| > 'delete' section was that I found no reasonable difference for our
| > case between 'drop' and 'delete'. Moreover, by seeing into VFS code
| > the only diff between 'drop' and 'delete' is that
| > inside generic_delete_inode() a few inode structure elements
| > are being destroyed and then our udf_drop_inode is called. So assuming,
| > that you're right in drop_inode I've code just moved to 'delete' section.
|   The difference is that udf_delete_inode() is called only when inode has
| i_nlink == 0 and thus it's being deleted on disk. udf_drop_inode() is
| called whenever inode is removed from memory which is what we want.
|   I'm already testing a patch which should fix the problem...
| 
| 								Honza
| -- 
| Jan Kara <jack@...e.cz>
| SuSE CR Labs
| 

Thanks for eplanation, Jan

		Cyrill

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