[LVM2 PATCH 1/2] lvrename: add mirrored LV support

[LVM2 PATCH 1/2] lvrename: add mirrored LV support

[Jun'ichi Nomura]

Hi,

Currently, renaming is not supported for mirrored LVs:
# lvrename testvg/l testvg/newlv
  Mirrored LV, "l" cannot be renamed: Function not implemented

This patch enables mirrored LV renaming.

Mirrored LV contains "sub LV"s.
e.g. "lv0" contains "lv0_mimage_0", .., "lv0_mimage_n" and "lv0_mlog".
"_mimage" and "_mlog" are reserved words, so normal LVs never has
these in their names.
To rename mirrored LV, we have to rename those sub LVs accordingly.

The patch is tested on CVS head (pre 2.02.28) for the following cases:
  - normal LVs (linear, striped, snapshot) for regression check
  - mirrored LVs (-m2, -m1, --corelog for both active and inactive)

Example:

[Before renaming]
# lvs -a -o name
  LV
  l
  [l_mimage_0]
  [l_mimage_1]
  [l_mlog]
# dmsetup ls
testvg-l_mlog   (253, 9)
testvg-l_mimage_0       (253, 10)
testvg-l_mimage_1       (253, 11)
testvg-l        (253, 12)

# lvrename testvg/l testvg/newlv
  Renamed "l" to "newlv" in volume group "testvg"

[After renaming]
# lvs -a -o name
  LV
  newlv
  [newlv_mimage_0]
  [newlv_mimage_1]
  [newlv_mlog]
# dmsetup ls
testvg-newlv_mlog       (253, 9)
testvg-newlv_mimage_0   (253, 10)
testvg-newlv_mimage_1   (253, 11)
testvg-newlv    (253, 12)


Thanks,
-- 
Jun'ichi Nomura, NEC Corporation of America
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Re: [LVM2 PATCH 1/2] lvrename: add mirrored LV support

[Jonathan Brassow]

On Jul 27, 2007, at 10:32 AM, Jun'ichi Nomura wrote:

> -	if ((lv->status & MIRRORED) ||
> -	    (lv->status & MIRROR_LOG) ||
> -	    (lv->status & MIRROR_IMAGE)) {
> -		log_error("Mirrored LV, \"%s\" cannot be renamed: %s",
> -			  lv->name, strerror(ENOSYS));
> -		return 0;
> -	}
> -

I don't think you want to remove this wholesale.  Testing reveals  
that you are allowed to change a sub-lv name by itself, which is not  
something we want, I don't think.  Instead, leave the checks in for  
MIRROR_LOG and MIRROR_IMAGE.

  brassow

Re: [LVM2 PATCH 2/2] lvrename: add mirrored LV support

[Jun'ichi Nomura]

Hi Jon,

Thanks for testing and reviewing.

Jonathan Brassow wrote:
>> -    if ((lv->status & MIRRORED) ||
>> -        (lv->status & MIRROR_LOG) ||
>> -        (lv->status & MIRROR_IMAGE)) {
>> -        log_error("Mirrored LV, \"%s\" cannot be renamed: %s",
>> -              lv->name, strerror(ENOSYS));
>> -        return 0;
>> -    }
>> -
> 
> I don't think you want to remove this wholesale.  Testing reveals that
> you are allowed to change a sub-lv name by itself, which is not
> something we want, I don't think.  Instead, leave the checks in for
> MIRROR_LOG and MIRROR_IMAGE.

You are right.
I didn't intend to remove the limitation.

I fixed it and modified 2 other parts:
  - Removed "Failed on <LV name>" messages from _for_each_sublv(),
    as they have no useful information.
    Callback function is responsible to put necessary info about
    failure. Added a comment about it.
  - Changed _rename_sub_lv() to return success if it can't
    determine a new name for the sub LV.
    e.g. if "lv1" is a sub LV of "lv0", renaming "lv0" will
         success without changing "lv1".
    This situation won't happen with current LVM2 code.
    But if such LVs exist, I think expected behaviour is leaving
    them unchanged and renaming others as far as possible.

Revised patch is attached.
(and fixed subject to "2/2" as it should have been)

Thanks,
-- 
Jun'ichi Nomura, NEC Corporation of America
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