Cannot umount ploop device PLOOP_IOC_STOP: Device or resource busy

Hello!

We have mounted ploop file -
ploop list -a | grep "ploop40437"
ploop40437 /vz/temp_nfs_folder/backup_images/extracted_backup_80232_0b49e189-5ae2-482a-4697-7aec9e50a7f3

And cannot umount it -

ploop umount -d /dev/ploop40437
Unmounting device /dev/ploop40437
--- lsof /dev/ploop40437 output ---
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
ploop 65395 root 3u BLK 182,646992 0t0 30258 /dev/ploop40437
sh 78295 root 3r BLK 182,646992 0t0 30258 /dev/ploop40437
--- lsof finished ---
Error in ploop_stop (ploop.c:1025): PLOOP_IOC_STOP: Device or resource busy

ploop umount -d /dev/ploop40437
Unmounting device /dev/ploop40437
--- lsof /dev/ploop40437 output ---
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
ploop 360015 root 3r BLK 182,646992 0t0 30258 /dev/ploop40437
sh 385521 root 3r BLK 182,646992 0t0 30258 /dev/ploop40437
--- lsof finished ---
Error in ploop_stop (ploop.c:1025): PLOOP_IOC_STOP: Device or resource busy

Pids changed ever run umount. And we not see this process before/after ploop umount -

[root@evo17 ~]# lsof /dev/ploop40437
[root@evo17 ~]# lsof /dev/ploop40437p1
[root@evo17 ~]# fuser -l /dev/ploop40437
HUP INT QUIT ILL TRAP ABRT IOT BUS FPE KILL USR1 SEGV USR2 PIPE ALRM TERM
STKFLT CHLD CONT STOP TSTP TTIN TTOU URG XCPU XFSZ VTALRM PROF WINCH IO PWR SYS
UNUSED
[root@evo17 ~]# fuser -l /dev/ploop40437p1
HUP INT QUIT ILL TRAP ABRT IOT BUS FPE KILL USR1 SEGV USR2 PIPE ALRM TERM
STKFLT CHLD CONT STOP TSTP TTIN TTOU URG XCPU XFSZ VTALRM PROF WINCH IO PWR SYS
UNUSED
[root@evo17 ~]# fuser -l /vz/temp_nfs_folder/backup_images/extracted_backup_80232_0b49e189-5ae2-482a-4697-7aec9e50a7f3
HUP INT QUIT ILL TRAP ABRT IOT BUS FPE KILL USR1 SEGV USR2 PIPE ALRM TERM
STKFLT CHLD CONT STOP TSTP TTIN TTOU URG XCPU XFSZ VTALRM PROF WINCH IO PWR SYS
UNUSED
[root@evo17 ~]# lsof /vz/temp_nfs_folder/backup_images/extracted_backup_80232_0b49e189-5ae2-482a-4697-7aec9e50a7f3
[root@evo17 ~]#

Errors in dmesg when try umount -
[1734367.690320] stop ploop40437 failed (holders=1)
[1734368.191059] stop ploop40437 failed (holders=1)
[1734369.191808] __ratelimit: 1 callbacks suppressed
[1734369.191981] stop ploop40437 failed (holders=1)
[1734369.692409] stop ploop40437 failed (holders=1)
[1734370.192848] stop ploop40437 failed (holders=1)
[1734370.693286] stop ploop40437 failed (holders=1)
[1734371.193726] stop ploop40437 failed (holders=1)
[1734371.694135] stop ploop40437 failed (holders=1)
[1734372.194570] stop ploop40437 failed (holders=1)
[1734372.695004] stop ploop40437 failed (holders=1)
[1734373.196266] stop ploop40437 failed (holders=1)
[1734373.697464] stop ploop40437 failed (holders=1)
[1734374.698170] __ratelimit: 1 callbacks suppressed
[1734374.698348] stop ploop40437 failed (holders=1)
[1734375.198781] stop ploop40437 failed (holders=1)
[1734375.699232] stop ploop40437 failed (holders=1)
[1734376.199674] stop ploop40437 failed (holders=1)
[1734376.700111] stop ploop40437 failed (holders=1)
[1734377.200573] stop ploop40437 failed (holders=1)
[1734377.701014] stop ploop40437 failed (holders=1)
[1734378.202214] stop ploop40437 failed (holders=1)
[1734378.702653] stop ploop40437 failed (holders=1)
[1734379.203601] stop ploop40437 failed (holders=1)
[1734380.204302] __ratelimit: 1 callbacks suppressed
[1734380.204479] stop ploop40437 failed (holders=1)
[1734380.704915] stop ploop40437 failed (holders=1)
[1734381.205352] stop ploop40437 failed (holders=1)
[1734381.705790] stop ploop40437 failed (holders=1)
[1734382.206227] stop ploop40437 failed (holders=1)
[1734382.706663] stop ploop40437 failed (holders=1)
[1734383.207101] stop ploop40437 failed (holders=1)
[1734383.708358] stop ploop40437 failed (holders=1)
[1734384.208796] stop ploop40437 failed (holders=1)
[1734384.709234] stop ploop40437 failed (holders=1)
[1734385.710135] __ratelimit: 1 callbacks suppressed
[1734385.710310] stop ploop40437 failed (holders=1)