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Subject: Re: hfsplus_unlink...hfsplus_block_free: lockdep warning
From: Peter Zijlstra <peterz@infradead.org>
To: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: linux-kernel@vger.kernel.org, Roman Zippel <zippel@linux-m68k.org>
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Date: Thu, 28 Feb 2008 16:15:50 +0100
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On Thu, 2008-02-28 at 16:07 +0100, Stefan Richter wrote:
> Hi,
> 
> I got this with 2.6.25-rc3 when doing an rm -rf on a HFS+ filesystem:
> 
> 
> [ INFO: possible recursive locking detected ]
> 2.6.25-rc3 #6
> ---------------------------------------------
> rm/7564 is trying to acquire lock:
>  (&sb->s_type->i_mutex_key#8){--..}, at: [<ffffffff880fc4ba>] hfsplus_block_free+0x57/0x209 [hfsplus]
> 
> but task is already holding lock:
>  (&sb->s_type->i_mutex_key#8){--..}, at: [<ffffffff80284f1c>] vfs_unlink+0x41/0xb7
> 
> other info that might help us debug this:
> 2 locks held by rm/7564:
>  #0:  (&type->i_mutex_dir_key#5/1){--..}, at: [<ffffffff80286cac>] do_unlinkat+0x6c/0x154
>  #1:  (&sb->s_type->i_mutex_key#8){--..}, at: [<ffffffff80284f1c>] vfs_unlink+0x41/0xb7
> 
> stack backtrace:
> Pid: 7564, comm: rm Not tainted 2.6.25-rc3 #6
> 
> Call Trace:
>  [<ffffffff802497bb>] __lock_acquire+0x849/0xbd5
>  [<ffffffff880fc4ba>] :hfsplus:hfsplus_block_free+0x57/0x209
>  [<ffffffff80249efd>] lock_acquire+0x51/0x6c
>  [<ffffffff880fc4ba>] :hfsplus:hfsplus_block_free+0x57/0x209
>  [<ffffffff80246b71>] debug_mutex_lock_common+0x16/0x23
>  [<ffffffff80418eb0>] mutex_lock_nested+0xd9/0x268
>  [<ffffffff880fc4ba>] :hfsplus:hfsplus_block_free+0x57/0x209
>  [<ffffffff880f647f>] :hfsplus:hfsplus_free_extents+0x54/0x9b
>  [<ffffffff880f6a92>] :hfsplus:hfsplus_file_truncate+0xa4/0x2ce
>  [<ffffffff880f52de>] :hfsplus:hfsplus_delete_inode+0x57/0x5d
>  [<ffffffff880f77e6>] :hfsplus:hfsplus_unlink+0xd0/0x158
>  [<ffffffff80284f36>] vfs_unlink+0x5b/0xb7
>  [<ffffffff80286cf1>] do_unlinkat+0xb1/0x154
>  [<ffffffff80419e4c>] trace_hardirqs_on_thunk+0x35/0x3a
>  [<ffffffff80248b03>] trace_hardirqs_on+0xf3/0x117
>  [<ffffffff80419e4c>] trace_hardirqs_on_thunk+0x35/0x3a
>  [<ffffffff880fb4a5>] :hfsplus:hfsplus_uni2asc+0x251/0x29f
>  [<ffffffff8020b0bb>] system_call_after_swapgs+0x7b/0x80
> 
> 
> Is this merely a case for annotation?

Being utterly clueless on HFS, and not having had a look yet, I'd say
its genuine. Esp. since the i_mutex lock class is per filesystem type.

So HFS has internal lock ordering problems, its not interaction with
another filesystem - like we used to have with ext vs the pseudo
filesystems.