On Sat, Aug 04, 2012 at 12:59:31PM +0200, Sasha Levin wrote:                                                                              
> Hi all,                                                                                                                                 
>                                                                                                                                         
> While fuzzing with trinity inside a KVM tools guest, using latest -next kernel, I've stumbled on the dump below.                        
>                                                                                                                                         
> I think this is the result of commit 765927b2 ("switch dentry_open() to struct path, make it grab references itself").                  
>                                                                                                                                         
> [   62.090519] ======================================================                                                                   
> [   62.091016] [ INFO: possible circular locking dependency detected ]                                                                  
> [   62.091016] 3.6.0-rc1-next-20120803-sasha #544 Tainted: G        W                                                                   
> [   62.091016] -------------------------------------------------------                                                                  
> [   62.091016] trinity-child0/6077 is trying to acquire lock:                                                                           
> [   62.091016]  (&sb->s_type->i_mutex_key#14){+.+.+.}, at: [<ffffffff8127c074>] vfs_unlink+0x54/0x100                                   
> [   62.091016]                                                                                                                          
> [   62.091016] but task is already holding lock:                                                                                        
> sb_writers#8){.+.+.+}, at: [<ffffffff812900bf>] mnt_want_write+0x1f/0x50                                                                
                                                                                                                                          
I met the same problem and it's bisected down to:                                                                                         
                                                                                                                                          
commit eb04c28288bb0098d0e75d81ba2a575239de71d8                                                                                           
Author: Jan Kara <jack@suse.cz>                                                                                                           
Date:   Tue Jun 12 16:20:35 2012 +0200                                                                                                    
                                                                                                                                          
    fs: Add freezing handling to mnt_want_write() / mnt_drop_write()                                                                      
                                                                                                                                          
Thanks,                                                                                                                                   
Fengguang