[lvm-devel] [PATCH] libdm-iface: not output error message inside retry loops

[Liuhua Wang]

Hi Zdenek,

Thanks for your reply.

> It's in fact made 'noisy' intentionally - we normally should detect whether 
> retry makes sense - so  what are the conditions when you experience this 
> problem ?
> 
> Common scenario:
> 
> The major reason for retry is 'unpredictable'  udev event processing
> i.e. you run  'umount' -> fires watch-rule -> lvremove  could have failed - 
> retry fixes this problem.

 We first found this problem when we were testing lvcreate-usage.sh included in
 lvm2-2.02.120 package. The case always failed due to the following message:
  device-mapper: remove ioctl on (253:6) failed: Device or resource busy
 [ 0:01]   Node @TESTDIR@/dev/mapper/@PREFIX at vg-LV2-cow was not removed by udev. Falling back to direct node removal.

Then we tested more cases and found the problem occurs in the following cases:
   - lvremove/lvcreate a snap lv
   - lvremove/lvcreate a thin lv
   - lvremove/lvcreate a mirror lv
 
o Reproduce frequency:
   lvremove about 80%, lvcreate occurs occasionally 
  
With the patch I attached, the lvcreate-usage.sh will not fail due to the error message.

Regards,
Liuhua