[RFC] WARNING: dev_open(xxx) called while suspended

[RFC] WARNING: dev_open(xxx) called while suspended

[Takahiro Yasui]

Hi,

I'm testing 'mirrored' log patch set and I'm annoyed with a following
warning message.
  WARNING: dev_open(xxx) called while suspended
Can I suppress it by lvm configuration or something?

This message is displayed whenever log type is switched.

# lvconvert -m1 --mirrorlog core vg00/lv00
  WARNING: dev_open(/dev/sdc) called while suspended
  WARNING: dev_open(/dev/sdf) called while suspended
  Logical volume lv00 converted.

# lvconvert -m1 --mirrorlog disk vg00/lv00
  WARNING: dev_open(/dev/sdf) called while suspended
  Logical volume lv00 converted.

I bisected and found that this WARNING was introduced by the following
patch, especially adding remote_commit_cached_metadata() function.

LVM2 ./WHATS_NEW daemons/clvmd/lvm-functions.c ...
https://www.redhat.com/archives/lvm-devel/2010-January/msg00006.html

+++ LVM2/lib/metadata/metadata.c	2010/01/05 16:09:34	1.308
@@ -2331,6 +2331,12 @@
 		}
 	}
 
+	/*
+	 * Instruct remote nodes to upgrade cached metadata.
+	 */
+	if (cache_updated)
+		remote_commit_cached_metadata(vg);
+

I appreciate your comments.

Thanks,
Taka

[RFC] WARNING: dev_open(xxx) called while suspended

[Alasdair G Kergon]

On Fri, Feb 19, 2010 at 11:20:09AM -0500, Takahiro Yasui wrote:
> warning message.
>   WARNING: dev_open(xxx) called while suspended
> Can I suppress it by lvm configuration or something?
 
No - if the message appears, it's means there's a bug that must be fixed:-)

Alasdair

[RFC] WARNING: dev_open(xxx) called while suspended

[Takahiro Yasui]

On 02/19/10 11:44, Alasdair G Kergon wrote:
> On Fri, Feb 19, 2010 at 11:20:09AM -0500, Takahiro Yasui wrote:
>> warning message.
>>   WARNING: dev_open(xxx) called while suspended
>> Can I suppress it by lvm configuration or something?
>  
> No - if the message appears, it's means there's a bug that must be fixed:-)

The rough sequence of lvconvert is

  1. construct new VG/LV data structure
  2. vg_write()
  3. suspend_lv()
      memlock_count++
  4. vg_commit()
      remove_commit_cached_metadata()  => Invalidate lvmcache

  5. resume_lv()
       _lv_resume()
         lv_from_lvid()
           fmt_from_vgname()
             label_read() => WARNING is displayed
      memlock_count--

By adding remove_commit_cached_metadata(), lvmcache is invalidated and
devices were scanned in resume_lv() with memlock_count != 0.

Can we move remove_commit_cached_metadata() just before memlock_count--?

Thanks,
Taka