Description of problem:
The target luks images by 'qemu-img convert' from raw/qcow2 images does not thin_provison, it will consume more time.


Version-Release number of selected component (if applicable):
qemu-kvm-3.1.0-22.module+el8.0.1+3032+a09688b9
kernel-4.18.0-80.el8
Local host(xfs): 
# df -T base.qcow2 
Filesystem                              Type 1K-blocks     Used Available Use% Mounted on
/dev/mapper/rhel_lenovo--sr630--02-home xfs  514894144 21243480 493650664   5% /home


How reproducible:
100%


Steps to Reproduce:

For source images with qcow2:

1. Create a source image
# qemu-img create -f qcow2 base.qcow2 5G
Formatting 'base.qcow2', fmt=qcow2 size=5368709120 cluster_size=65536 lazy_refcounts=off refcount_bits=16

# qemu-io -c 'write -P 1 0 1G' base.qcow2 
wrote 1073741824/1073741824 bytes at offset 0
1 GiB, 1 ops; 0:00:06.10 (167.722 MiB/sec and 0.1638 ops/sec)

# qemu-img info base.qcow2 
image: base.qcow2
file format: qcow2
virtual size: 5.0G (5368709120 bytes)
disk size: 1.0G
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false


2. Convert the image to luks
# qemu-img convert -f qcow2 -O luks --object secret,id=sec0,data=convert -o key-secret=sec0 base.qcow2 tgt.luks -p
    (100.00/100%)

3. Check the info of the target image
# qemu-img info tgt.luks 
image: tgt.luks
file format: luks
virtual size: 5.0G (5368709120 bytes)
disk size: 5.0G ------------------ fully allocated!!!
encrypted: yes
Format specific information:
    ivgen alg: plain64
    hash alg: sha256
    cipher alg: aes-256
    uuid: bba81fbd-c86c-4836-91cc-be18cec7a242
    cipher mode: xts
    slots:
        [0]:
            active: true
            iters: 1131882
            key offset: 4096
            stripes: 4000
        [1]:
            active: false
            key offset: 262144
        [2]:
            active: false
            key offset: 520192
        [3]:
            active: false
            key offset: 778240
        [4]:
            active: false
            key offset: 1036288
        [5]:
            active: false
            key offset: 1294336
        [6]:
            active: false
            key offset: 1552384
        [7]:
            active: false
            key offset: 1810432
    payload offset: 2068480
    master key iters: 282482



For source images with raw format:

1. Create a source image

# qemu-img create -f raw base.img 5G
Formatting 'base.img', fmt=raw size=5368709120

# qemu-io -c 'write -P 1 0 1g' base.img -f raw
wrote 1073741824/1073741824 bytes at offset 0
1 GiB, 1 ops; 0:00:05.90 (173.438 MiB/sec and 0.1694 ops/sec)

# qemu-img info base.img 
image: base.img
file format: raw
virtual size: 5.0G (5368709120 bytes)
disk size: 1.0G

2. Convert to luks image
# qemu-img convert -f raw -O luks --object secret,id=sec0,data=convert -o key-secret=sec0 base.img tgt_from_raw.luks -p
    (100.00/100%)

3. Check info of the target image
# qemu-img info tgt_from_raw.luks 
image: tgt_from_raw.luks
file format: luks
virtual size: 5.0G (5368709120 bytes)
disk size: 5.0G --------------------- Fully allocated!!!
encrypted: yes
Format specific information:
    ivgen alg: plain64
    hash alg: sha256
    cipher alg: aes-256
    uuid: 618fc503-0fcd-45a0-9d2c-ee7dace4bc4f
    cipher mode: xts
    slots:
        [0]:
            active: true
            iters: 1143734
            key offset: 4096
            stripes: 4000
        [1]:
            active: false
            key offset: 262144
        [2]:
            active: false
            key offset: 520192
        [3]:
            active: false
            key offset: 778240
        [4]:
            active: false
            key offset: 1036288
        [5]:
            active: false
            key offset: 1294336
        [6]:
            active: false
            key offset: 1552384
        [7]:
            active: false
            key offset: 1810432
    payload offset: 2068480
    master key iters: 285861
 


Actual results:
As above.


Expected results:
The target luks images should be thin_provisioned.


Additional info: