[QEUSTION] VG refresh: remove disk and reinsert disk, VG not refresh

[QEUSTION] VG refresh: remove disk and reinsert disk, VG not refresh

[Wu Guanghao]

We use LVM2.02.187 to create a logical volume on the disk,
and then remove the disk and reinsert it. When reading and
writing the logical volume, IO error occurred. But LVM2.02.181
version can be used normally.

If remove disk and reinsert disk, drive letter has changed.
Maybe /dev/sda -> /dev/sdc

LVM 2.02.181: (vg autoactivate and refresh)
# lsblk

/dev/sda (8:16)		/dev/sdc (8:32)
   |		---->      |
   |----vg-lv		   |----vg-lv

# dmsetup table

vg-lv: 0 20963328 linear 8:16 2048  ----->  vg-lv: 0 20963328 linear 8:32 2048


_pvscan_autoactivate
	|
	|----_pvscan_autoactivate_single
			|
			|----vg_refresh_visible
				  |
				  |----lv_refresh ( refresh lv table, change dm-target)



LVM 2.02.187 and later (vg autoactivate but not refresh)

#lsblk

/dev/sda (8:16)		/dev/sdc (8:32)
   |		---->      |
   |----vg-lv		   |---- nothing

#dmsetup table

vg-lv: 0 20963328 linear 8:16 2048 (not change, so read/write lv failed.)


_pvscan_autoactivate
	|
	|----_pvscan_autoactivate_single
			|
			|---- vg_refresh_visible ( skip, so lv not refresh)

and later version, _pvscan_autoactivate_single has deleted.


So I want to know how to add vg refresh function in the 2.02.187 and later to keep it the same as 2.02.181,
and why delete vg refresh function?

Thanks.

[QEUSTION] VG refresh: remove disk and reinsert disk, VG not refresh

[David Teigland]

On Mon, Nov 16, 2020 at 11:15:50AM +0800, Wu Guanghao wrote:
> So I want to know how to add vg refresh function in the 2.02.187 and
> later to keep it the same as 2.02.181, and why delete vg refresh
> function?

Sorry, I don't think I quite knew what a proper use of that looked like
when removing it.  All the cases I saw were unnecessary or were causing
problems.  The motivation was numerous problems reported about failed
activation during boot, some involving unwanted refreshes.  A better fix
might have found a way to preserve it in the stable branch.

If you're compiling your own lvm it would be simple to restore, enable the
if 0 section in pvscan.c.

More generally, refresh didn't fit correctly where it was implemented.  It
depended on lvmetad (now removed), and was not really related to
autoactivation.  If an automatic refresh feature is warranted, it should
be designed and implemented to stand on its own.

Dave

[QUESTION] VG refresh: remove disk and reinsert disk, VG not refresh

[Wu Guanghao]

Thank you for your answer, we will solve this problem in our own way.

? 2020/11/17 0:41, David Teigland ??:
> On Mon, Nov 16, 2020 at 11:15:50AM +0800, Wu Guanghao wrote:
>> So I want to know how to add vg refresh function in the 2.02.187 and
>> later to keep it the same as 2.02.181, and why delete vg refresh
>> function?
> 
> Sorry, I don't think I quite knew what a proper use of that looked like
> when removing it.  All the cases I saw were unnecessary or were causing
> problems.  The motivation was numerous problems reported about failed
> activation during boot, some involving unwanted refreshes.  A better fix
> might have found a way to preserve it in the stable branch.
> 
> If you're compiling your own lvm it would be simple to restore, enable the
> if 0 section in pvscan.c.
> 
> More generally, refresh didn't fit correctly where it was implemented.  It
> depended on lvmetad (now removed), and was not really related to
> autoactivation.  If an automatic refresh feature is warranted, it should
> be designed and implemented to stand on its own.
> 
> Dave
>