[linux-lvm] lvdisplay "open" field computing

[Zdenek Kabelac]

Dne 11. 07. 19 v 11:39 Simon ELBAZ napsal(a):
> Hi,
> 
> I have setup a Debian 10 VM to understand the issue.
> 
> root at sympa:~# uname -a
> Linux sympa 4.19.0-5-amd64 #1 SMP Debian 4.19.37-5 (2019-06-19) x86_64 GNU/Linux
> root at sympa:~# lvdisplay /dev/sympa-vg/swap_1
>    --- Logical volume ---
>    LV Path                /dev/sympa-vg/swap_1
>    LV Name                swap_1
>    VG Name                sympa-vg
>    LV UUID                1b59OW-M2yW-PuI1-QN5t-pN0w-6Akl-AnJnNh
>    LV Write Access        read/write
>    LV Creation host, time sympa, 2019-07-10 11:06:42 +0200
>    LV Status              available
>    # open                 2
>    LV Size                <1,99 GiB
>    Current LE             509
>    Segments               1
>    Allocation             inherit
>    Read ahead sectors     auto
>    - currently set to     256
>    Block device           254:1
> 
> root at sympa:~# lsof | grep "254,1"
> root at sympa:~# dmsetup info
> Name:              sympa--vg-swap_1
> State:             ACTIVE
> Read Ahead:        256
> Tables present:    LIVE
> Open count:        2
> Event number:      0
> Major, minor:      254, 1
> Number of targets: 1
> UUID: LVM-Imuz5YW2OXfsyO2ChOPPLI5flib9YlLi1b59OWM2yWPuI1QN5tpN0w6AklAnJnNh
> 
> Name:              sympa--vg-root
> State:             ACTIVE
> Read Ahead:        256
> Tables present:    LIVE
> Open count:        1
> Event number:      0
> Major, minor:      254, 0
> Number of targets: 1
> UUID: LVM-Imuz5YW2OXfsyO2ChOPPLI5flib9YlLiJMF1vN1e6TKmfV1rT0fvWJnpViu7BMw5
> 
> root at sympa:~# lsof | grep swap_1
> 
> root at sympa:~#
> 
> Could someone pls give me some hints to verify the "open" value ?
> 

Hi

Have you tried  'swapon -s' ?

 From the name I'd have guessed it's an active swapping device (so held open 
by kernel and not visible by user-space tools like lsof)

'swapoff' should close opened swapping device (in case you have enough free 
RAM to live without swap space)

Regards

Zdenek