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Date:	Wed, 18 Jun 2008 11:45:42 +0200
From:	Jan Kara <jack@...e.cz>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: circular locking dependency detected with lock inversion

  Hi,

On Tue 17-06-08 22:32:49, Aneesh Kumar K.V wrote:
> 
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.26-rc6-autokern1 #1
> -------------------------------------------------------
> umount/28231 is trying to acquire lock:
>  (&ei->i_data_sem){----}, at: [<ffffffff8030be45>] ext4_get_blocks_wrap+0x36/0x15c
> 
> but task is already holding lock:
>  (&type->s_lock_key#7){--..}, at: [<ffffffff8028a856>] lock_super+0x22/0x24
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #1 (&type->s_lock_key#7){--..}:
>        [<ffffffff8024dbcf>] __lock_acquire+0xc3c/0xe20
>        [<ffffffff8024e052>] lock_acquire+0x53/0x6d
>        [<ffffffff80503ae2>] mutex_lock_nested+0xd6/0x27d
>        [<ffffffff8028a856>] lock_super+0x22/0x24
>        [<ffffffff803105e1>] ext4_orphan_add+0x29/0x17d
>        [<ffffffff8031a538>] ext4_ext_truncate+0x91/0x19c
>        [<ffffffff8030c984>] ext4_truncate+0xbb/0x568
>        [<ffffffff8026f07e>] vmtruncate+0xc2/0xe0
>        [<ffffffff8029d586>] inode_setattr+0x28/0x123
>        [<ffffffff8030ad2f>] ext4_setattr+0x226/0x284
>        [<ffffffff8029d7ea>] notify_change+0x169/0x27b
>        [<ffffffff80287886>] do_truncate+0x60/0x7e
>        [<ffffffff80287a16>] sys_truncate+0x172/0x1a8
>        [<ffffffff80222721>] sys32_truncate64+0x16/0x18
>        [<ffffffff802223a2>] ia32_sysret+0x0/0xa
>        [<ffffffffffffffff>] 0xffffffffffffffff
> 
> -> #0 (&ei->i_data_sem){----}:
>        [<ffffffff8024dab7>] __lock_acquire+0xb24/0xe20
>        [<ffffffff8024e052>] lock_acquire+0x53/0x6d
>        [<ffffffff805045f7>] down_read+0x25/0x31
>        [<ffffffff8030be45>] ext4_get_blocks_wrap+0x36/0x15c
>        [<ffffffff8030c4cc>] ext4_get_block+0xb5/0xf3
>        [<ffffffff802ab7ee>] generic_block_bmap+0x3a/0x40
>        [<ffffffff803093bb>] ext4_bmap+0x70/0x79
>        [<ffffffff8029c9aa>] bmap+0x1f/0x27
>        [<ffffffff80335c8d>] jbd2_journal_bmap+0x2c/0x8a
>        [<ffffffff80335fe5>] jbd2_journal_next_log_block+0x76/0x7e
>        [<ffffffff803362cd>] jbd2_journal_get_descriptor_buffer+0x17/0x80
>        [<ffffffff80331b15>] jbd2_journal_commit_transaction+0x56e/0x1045
>        [<ffffffff803356c4>] jbd2_journal_destroy+0xfc/0x250
>        [<ffffffff80312acf>] ext4_put_super+0x3e/0x213
>        [<ffffffff8028a96a>] generic_shutdown_super+0x63/0xf8
>        [<ffffffff8028b6d6>] kill_block_super+0x12/0x27
>        [<ffffffff8028a81f>] deactivate_super+0x4c/0x61
>        [<ffffffff8029f28b>] mntput_no_expire+0xed/0x120
>        [<ffffffff802a0d30>] sys_umount+0x312/0x327
>        [<ffffffff802223a2>] ia32_sysret+0x0/0xa
>        [<ffffffffffffffff>] 0xffffffffffffffff
  The problem is we call ext4_orphan_add() in ext4_ext_truncate() under
i_data_sem. I wonder why we didn't hit it earlier... In principle, there's
no reason why ext4_orphan_add() could not be called earlier. So the patch
below should help.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR

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