My snapshot script cleans old snapshots regularly. Whenever it deletes the oldest snapshot it also removes the snapshot from all assigned qgroups and deletes the default qgroup 0/<subvol-id>. The filesystem seems to operate normally afterwards and the snapshot is deleted, however my dmesg gets spammed with these: [ 3839.116726] ------------[ cut here ]------------ [ 3839.116742] WARNING: CPU: 0 PID: 136 at fs/btrfs/qgroup.c:1347 btrfs_delayed_qgroup_accounting+0x7c6/0xc00() [ 3839.116745] Modules linked in: ctr ccm btusb bluetooth x86_pkg_temp_thermal intel_powerclamp kvm_intel kvm arc4 crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 lrw iwldvm gf128mul glue_helper ablk_helper mac80211 cryptd snd_hda_codec_hdmi microcode snd_hda_codec_realtek snd_hda_codec_generic iwlwifi iTCO_wdt psmouse i2c_i801 cfg80211 iTCO_vendor_support snd_hda_intel snd_hda_controller sdhci_pci sdhci snd_hda_codec thinkpad_acpi mei_me snd_hwdep nvram mei snd_pcm [ 3839.116793] CPU: 0 PID: 136 Comm: btrfs-transacti Tainted: G W 3.16.0-rc5 #1 [ 3839.116796] Hardware name: LENOVO 2325CN9/2325CN9, BIOS G2ET92WW (2.52 ) 02/22/2013 [ 3839.116799] 0000000000000009 ffff880406aa7c88 ffffffff81758272 0000000000000000 [ 3839.116804] ffff880406aa7cc0 ffffffff81050b0d ffff8800aaca7d60 ffff880406cd1688 [ 3839.116808] 0000000000000000 ffff8803b2684a58 ffff880406c4f000 ffff880406aa7cd0 [ 3839.116813] Call Trace: [ 3839.116823] [<ffffffff81758272>] dump_stack+0x4d/0x6f [ 3839.116830] [<ffffffff81050b0d>] warn_slowpath_common+0x7d/0xa0 [ 3839.116836] [<ffffffff81050bea>] warn_slowpath_null+0x1a/0x20 [ 3839.116841] [<ffffffff8130b106>] btrfs_delayed_qgroup_accounting+0x7c6/0xc00 [ 3839.116847] [<ffffffff81299b0a>] btrfs_run_delayed_refs.part.65+0x20a/0x270 [ 3839.116850] [<ffffffff81299b87>] btrfs_run_delayed_refs+0x17/0x20 [ 3839.116856] [<ffffffff812a991e>] btrfs_commit_transaction+0x4e/0xa10 [ 3839.116861] [<ffffffff812a5c0d>] transaction_kthread+0x1ad/0x240 [ 3839.116866] [<ffffffff812a5a60>] ? btrfs_cleanup_transaction+0x580/0x580 [ 3839.116871] [<ffffffff81071f39>] kthread+0xc9/0xe0 [ 3839.116875] [<ffffffff81071e70>] ? kthread_create_on_node+0x180/0x180 [ 3839.116882] [<ffffffff817600fc>] ret_from_fork+0x7c/0xb0 [ 3839.116885] [<ffffffff81071e70>] ? kthread_create_on_node+0x180/0x180 [ 3839.116888] ---[ end trace 26e77b7600b78b16 ]---
This is a semi-automated bugzilla cleanup, report is against an old kernel version. If the problem still happens, please open a new bug. Thanks.