[Ocfs2-devel] Ocfs2-devel Digest, Vol 167, Issue 20

[Guozhonghua]

> Message: 1
> Date: Fri, 12 Jan 2018 06:15:01 +0000
> From: Shichangkuo <shi.changkuo at h3c.com>
> Subject: Re: [Ocfs2-devel] [Ocfs2-dev] BUG: deadlock with umount and
> 	ocfs2 workqueue triggered by ocfs2rec thread
> To: Joseph Qi <jiangqi903 at gmail.com>, "zren at suse.com" <zren at suse.com>,
> 	"jack at suse.cz" <jack at suse.cz>
> Cc: "ocfs2-devel at oss.oracle.com" <ocfs2-devel at oss.oracle.com>
> Message-ID:
> 	<D1E4D02760513D4B90DC3B40FF32AF35E22EC513 at H3CMLB14-EX.srv.huawe
> i-3com.com>
> 
> Content-Type: text/plain; charset="gb2312"
> 
> Hi Joseph
>     Thanks for replying.
>     Umount will flush the ocfs2 workqueue in function
> ocfs2_truncate_log_shutdown and journal recovery is one work of ocfs2 wq.
> 
> Thanks
> Changkuo
> 

Umount 
  mngput
   cleanup_mnt 
 	 deactivate_super:   down_write the rw_semaphore:  down_write(&s->s_umount)
	    deactivate_locked_super
 		  kill_sb: kill_block_super
			generic_shutdown_super
				put_super : ocfs2_put_supe
					ocfs2_dismount_volume
						ocfs2_truncate_log_shutdown 
							flush_workqueue(osb->ocfs2_wq);
								ocfs2_finish_quota_recovery
									down_read(&sb->s_umount); 
									 Here retry down_read rw_semaphore; down read while holding write?  Try rw_semaphore twice, dead lock ?
	                                 The flush work queue of ocfs2_wq will be blocked, so as the umount ops.  

Thanks.