Backtrace

WARNING: CPU: 2 PID: 196225 at fs/btrfs/block-group.c:127 btrfs_put_block_group+0x77/0xb0
Modules linked in: snd_usb_audio snd_usbmidi_lib snd_rawmidi uinput vxlan ip6_udp_tunnel udp_tunnel rfcomm snd_seq_dummy snd_hrtimer br_netfilter bridge stp llc ip_set nfnetlink overlay bnep sunrpc vfat fat squashfs loop snd_soc_skl snd_soc_hdac_hda snd_hda_ext_core iTCO_wdt intel_pmc_bxt mei_pxp snd_soc_sst_ipc snd_soc_sst_dsp iTCO_vendor_support snd_soc_acpi_intel_match snd_soc_acpi snd_soc_core intel_tcc_cooling intel_rapl_msr x86_pkg_temp_thermal snd_compress mei_hdcp intel_powerclamp coretemp ac97_bus snd_pcm_dmaengine kvm_intel snd_hda_codec_hdmi kvm dell_laptop snd_ctl_led snd_hda_codec_realtek dell_smm_hwmon snd_hda_codec_generic iwlmvm snd_hda_intel snd_intel_dspcfg irqbypass snd_intel_sdw_acpi mac80211 snd_hda_codec rapl snd_hda_core intel_cstate wl(POE) snd_hwdep intel_uncore snd_seq snd_seq_device dell_wmi libarc4 ledtrig_audio wmi_bmof dell_smbios snd_pcm intel_wmi_thunderbolt dcdbas pcspkr dell_wmi_descriptor uvcvideo iwlwifi videobuf2_vmalloc videobuf2_memops
 btusb videobuf2_v4l2 videobuf2_common snd_timer btrtl videodev btbcm btintel snd i2c_i801 i2c_smbus soundcore bluetooth cfg80211 mc ecdh_generic rfkill processor_thermal_device_pci_legacy joydev processor_thermal_device processor_thermal_rfim processor_thermal_mbox processor_thermal_rapl mei_me intel_rapl_common mei idma64 intel_xhci_usb_role_switch intel_pch_thermal intel_soc_dts_iosf intel_hid sparse_keymap int3403_thermal int340x_thermal_zone int3400_thermal acpi_pad acpi_thermal_rel zram dm_crypt i915 r8152 mii rtsx_pci_sdmmc mmc_core hid_multitouch i2c_algo_bit crct10dif_pclmul crc32_pclmul crc32c_intel ttm ghash_clmulni_intel drm_kms_helper cec serio_raw nvme nvme_core drm rtsx_pci uas usb_storage i2c_hid_acpi i2c_hid wmi video pinctrl_sunrisepoint ipmi_devintf ipmi_msghandler fuse [last unloaded: ip_tables]
CPU: 2 PID: 196225 Comm: umount Tainted: P          IOE     5.16.8-100.fc34.x86_64 #1
Hardware name: Dell Inc. XPS 13 9350/0PWNCR, BIOS 1.13.0 02/10/2020
RIP: 0010:btrfs_put_block_group+0x77/0xb0
Code: 21 48 8b bd c0 00 00 00 e8 b6 cd db ff 48 8b bd 48 02 00 00 e8 aa cd db ff 48 89 ef 5d e9 a1 cd db ff 0f 0b eb db 0f 0b eb b1 <0f> 0b eb b4 0f 0b 48 8b 45 00 48 89 ee 48 8d b8 48 08 00 00 e8 10
RSP: 0000:ffff9fe04059bde8 EFLAGS: 00010206
RAX: 0000000000000001 RBX: ffff8ba9c3415000 RCX: 0000000000000000
RDX: 0000000000000001 RSI: 0000000000001000 RDI: ffff8ba97cab2800
RBP: ffff8ba97cab2800 R08: 0000000000000000 R09: 000000000033002e
R10: ffff8ba9c7ab7900 R11: 0000000000000002 R12: ffff8ba9c3415088
R13: ffff8ba9c3415098 R14: ffff8ba97cab28c8 R15: dead000000000100
FS:  00007f9a11d42c40(0000) GS:ffff8baa76d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0bdac4953c CR3: 0000000103f70001 CR4: 00000000003706e0
Call Trace:
 <TASK>
 btrfs_free_block_groups+0x215/0x380
 close_ctree+0x288/0x2b4
 generic_shutdown_super+0x74/0x120
 kill_anon_super+0x14/0x30
 btrfs_kill_super+0x12/0x20
 deactivate_locked_super+0x36/0xa0
 cleanup_mnt+0x131/0x190
 task_work_run+0x5c/0x90
 exit_to_user_mode_prepare+0x229/0x230
 syscall_exit_to_user_mode+0x18/0x40
 do_syscall_64+0x48/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f9a11f7135b
Code: 2b 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 90 f3 0f 1e fa 31 f6 e9 05 00 00 00 0f 1f 44 00 00 f3 0f 1e fa b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 8b 15 e9 2a 0c 00 f7 d8
RSP: 002b:00007fffe6378ba8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000558997e71f50 RCX: 00007f9a11f7135b
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000558997e71d60
RBP: 0000558997e71b30 R08: 0000000000000000 R09: 00007f9a12034a60
R10: 0000558997e729c0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000558997e71d60 R14: 0000558997e71c40 R15: 0000558997e71b30
 </TASK>