btrfs-progs v7.1
See https://btrfs.readthedocs.io for more information.

Performing full device TRIM /dev/loop1 (5.00GiB) ...
NOTE: default settings have changed in version 6.19 (supported since linux 6.1):
      - enable block-group-tree (-O bgt)

Label:              (null)
UUID:               52ac327e-dcaa-432f-8cd6-faa0a0e0cbfe
Node size:          4096
Sector size:        4096	(CPU page size: 4096)
Filesystem size:    5.00GiB
Block group profiles:
  Data:             single            8.00MiB
  Metadata:         DUP             256.00MiB
  System:           DUP               8.00MiB
SSD detected:       yes
Zoned device:       no
Features:           extref, skinny-metadata, no-holes, free-space-tree, block-group-tree
Checksum:           crc32c
Number of devices:  1
Devices:
   ID        SIZE  PATH      
    1     5.00GiB  /dev/loop1

Create subvolume '/mnt/scratch/S1'
Create readonly snapshot of '/mnt/scratch/S1' in '/mnt/scratch/S2'
S1 id 256 root level 3 files 100000
Delete subvolume 256 (no-commit): '/mnt/scratch/S1'
first run interrupted at drop key (4531) level 3
resume 0: drop key (0) level 0
WARNING: filesystem is now read-only
Waiting for 1 subvolume
_check_btrfs_filesystem: filesystem on /dev/loop1 is inconsistent
*** fsck.btrfs output ***
[1/8] checking log skipped (none written)
[2/8] checking root items
[3/8] checking extents
ref mismatch on [556228608 4096] extent item 1, found 2
tree extent[556228608, 4096] root 256 has no backref item in extent tree
backpointer mismatch on [556228608 4096]
ERROR: errors found in extent allocation tree or chunk allocation
[4/8] checking free space tree
[5/8] checking fs roots
[6/8] checking only csums items (without verifying data)
[7/8] checking root refs
[8/8] checking quota groups skipped (not enabled on this FS)
Opening filesystem to check...
Checking filesystem on /dev/loop1
UUID: 52ac327e-dcaa-432f-8cd6-faa0a0e0cbfe
found 657383424 bytes used, error(s) found
total csum bytes: 0
total tree bytes: 657383424
total fs tree bytes: 647462912
total extent tree bytes: 9859072
btree space waste bytes: 285705236
file data blocks allocated: 0
 referenced 0
*** end fsck.btrfs output
*** mount output ***
tmpfs on /run type tmpfs (rw,nosuid,nodev,size=1208880k,nr_inodes=819200,mode=755,inode64)
/dev/xvda1 on / type ext4 (rw,relatime,discard,errors=remount-ro,commit=30)
devtmpfs on /dev type devtmpfs (rw,nosuid,size=2988536k,nr_inodes=747134,mode=755,inode64)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev,inode64,usrquota)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=600,ptmxmode=000)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
cgroup2 on /sys/fs/cgroup type cgroup2 (rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot,memory_hugetlb_accounting)
none on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
configfs on /sys/kernel/config type configfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=42,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=9407)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,nr_inodes=1048576,inode64,usrquota)
mqueue on /dev/mqueue type mqueue (rw,nosuid,nodev,noexec,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,nosuid,nodev,noexec,relatime)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,nosuid,nodev,relatime,pagesize=2M)
tracefs on /sys/kernel/tracing type tracefs (rw,nosuid,nodev,noexec,relatime)
none on /run/credentials/systemd-journald.service type tmpfs (ro,nosuid,nodev,noexec,relatime,nosymfollow,size=1024k,nr_inodes=1024,mode=700,inode64,noswap)
fusectl on /sys/fs/fuse/connections type fusectl (rw,nosuid,nodev,noexec,relatime)
none on /run/credentials/systemd-resolved.service type tmpfs (ro,nosuid,nodev,noexec,relatime,nosymfollow,size=1024k,nr_inodes=1024,mode=700,inode64,noswap)
/dev/xvda13 on /boot type ext4 (rw,relatime)
/dev/xvda15 on /boot/efi type vfat (rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,nosuid,nodev,noexec,relatime)
none on /run/credentials/systemd-networkd.service type tmpfs (ro,nosuid,nodev,noexec,relatime,nosymfollow,size=1024k,nr_inodes=1024,mode=700,inode64,noswap)
none on /run/credentials/getty@tty1.service type tmpfs (ro,nosuid,nodev,noexec,relatime,nosymfollow,size=1024k,nr_inodes=1024,mode=700,inode64,noswap)
tmpfs on /run/user/1000 type tmpfs (rw,nosuid,nodev,relatime,size=604440k,nr_inodes=151110,mode=700,uid=1000,gid=1000,inode64)
none on /run/credentials/serial-getty@hvc0.service type tmpfs (ro,nosuid,nodev,noexec,relatime,nosymfollow,size=1024k,nr_inodes=1024,mode=700,inode64,noswap)
tmpfs on /mnt/ramimg type tmpfs (rw,relatime,size=3584000k,inode64)
none on /run/credentials/serial-getty@ttyS0.service type tmpfs (ro,nosuid,nodev,noexec,relatime,nosymfollow,size=1024k,nr_inodes=1024,mode=700,inode64,noswap)
*** end mount output
umount: /mnt/scratch: not mounted.