BTRFS related kernel backtrace on boot on 4.18.7 after blackout due to discharged battery

Hello!

On ThinkPad T520 after battery was discharged and machine just blacked out.

Is that some sign of regular consistency check / replay or something to investigate further?

I already scrubbed all data and there are no errors. Also btrfs device stats reports no errors. SMART status appears to be okay as well on both SSD.

[    4.524355] BTRFS info (device dm-4): disk space caching is enabled
[    4.524356] BTRFS info (device dm-4): has skinny extents
[    4.563950] BTRFS info (device dm-4): enabling ssd optimizations
[    5.463085] Console: switching to colour frame buffer device 240x67
[    5.492236] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device
[    5.882661] BTRFS info (device dm-3): disk space caching is enabled
[    5.882664] BTRFS info (device dm-3): has skinny extents
[    5.918579] SGI XFS with ACLs, security attributes, realtime, scrub, no debug enabled
[    5.927421] Adding 20971516k swap on /dev/mapper/sata-swap.  Priority:-2 extents:1 across:20971516k SSDsc
[    5.935051] XFS (sdb1): Mounting V5 Filesystem
[    5.935218] XFS (sda1): Mounting V5 Filesystem
[    5.961100] XFS (sda1): Ending clean mount
[    5.970857] BTRFS info (device dm-3): enabling ssd optimizations
[    5.972358] XFS (sdb1): Ending clean mount
[    5.975955] WARNING: CPU: 1 PID: 1104 at fs/inode.c:342 inc_nlink+0x28/0x30
[    5.978271] Modules linked in: xfs msr pktcdvd intel_rapl x86_pkg_temp_thermal intel_powerclamp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel snd_hda_codec_hdmi pcbc arc4 snd_hda_codec_conexant snd_hda_codec_generic iwldvm mac80211 iwlwifi aesni_intel snd_hda_intel snd_hda_codec aes_x86_64 crypto_simd cryptd snd_hda_core glue_helper intel_cstate snd_hwdep intel_rapl_perf snd_pcm pcspkr input_leds i915 sg cfg80211 snd_timer thinkpad_acpi nvram drm_kms_helper snd soundcore tpm_tis tpm_tis_core drm rfkill ac tpm i2c_algo_bit fb_sys_fops battery rng_core video syscopyarea sysfillrect sysimgblt button evdev sbs sbshc coretemp bfq hdaps(O) tp_smapi(O) thinkpad_ec(O) loop ecryptfs cbc sunrpc mcryptd sha256_ssse3 sha256_generic encrypted_keys ip_tables x_tables autofs4 dm_mod
[    5.990499]  btrfs xor zstd_decompress zstd_compress xxhash zlib_deflate raid6_pq libcrc32c crc32c_generic sr_mod cdrom sd_mod hid_lenovo hid_generic usbhid hid ahci libahci libata ehci_pci crc32c_intel psmouse i2c_i801 sdhci_pci cqhci lpc_ich sdhci ehci_hcd e1000e scsi_mod i2c_core mfd_core mmc_core usbcore usb_common thermal
[    5.990529] CPU: 1 PID: 1104 Comm: mount Tainted: G           O      4.18.7-tp520 #63
[    5.990532] Hardware name: LENOVO 42433WG/42433WG, BIOS 8AET69WW (1.49 ) 06/14/2018
[    6.000153] RIP: 0010:inc_nlink+0x28/0x30
[    6.000154] Code: 00 00 8b 47 48 85 c0 74 07 83 c0 01 89 47 48 c3 f6 87 a1 00 00 00 04 74 11 48 8b 47 28 f0 48 ff 88 98 04 00 00 8b 47 48 eb df <0f> 0b eb eb 0f 1f 40 00 41 54 8b 0d 70 3f aa 00 48 ba eb 83 b5 80
[    6.008573] RSP: 0018:ffffc90002283828 EFLAGS: 00010246
[    6.008575] RAX: 0000000000000000 RBX: ffff8804018bed58 RCX: 0000000000022261
[    6.008576] RDX: 0000000000022251 RSI: 0000000000000000 RDI: ffff8804018bed58
[    6.008577] RBP: ffffc90002283a50 R08: 000000000002a330 R09: ffffffffa02f3873
[    6.008578] R10: 30ffffffffffffff R11: 0000000000007763 R12: 0000000000000011
[    6.008579] R13: 0000000000003d5f R14: ffff880403e19800 R15: ffff88040a3c69a0
[    6.008580] FS:  00007f071598f100(0000) GS:ffff88041e240000(0000) knlGS:0000000000000000
[    6.008581] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    6.008589] CR2: 00007fda4fbf8218 CR3: 0000000403e42001 CR4: 00000000000606e0
[    6.008590] Call Trace:
[    6.008614]  replay_one_buffer+0x80e/0x890 [btrfs]
[    6.008632]  walk_up_log_tree+0x1dc/0x260 [btrfs]
[    6.046858]  walk_log_tree+0xaf/0x1e0 [btrfs]
[    6.046872]  btrfs_recover_log_trees+0x21c/0x410 [btrfs]
[    6.046885]  ? btree_read_extent_buffer_pages+0xcd/0x210 [btrfs]
[    6.055941]  ? fixup_inode_link_counts+0x170/0x170 [btrfs]
[    6.055953]  open_ctree+0x1a0d/0x1b60 [btrfs]
[    6.055965]  btrfs_mount_root+0x67b/0x760 [btrfs]
[    6.065039]  ? pcpu_alloc_area+0xdd/0x120
[    6.065040]  ? pcpu_next_unpop+0x32/0x40
[    6.065052]  mount_fs+0x36/0x162
[    6.065055]  vfs_kern_mount.part.34+0x4f/0x120
[    6.065064]  btrfs_mount+0x15f/0x890 [btrfs]
[    6.065067]  ? pcpu_cnt_pop_pages+0x40/0x50
[    6.065069]  ? pcpu_alloc_area+0xdd/0x120
[    6.065071]  ? pcpu_next_unpop+0x32/0x40
[    6.065073]  ? cpumask_next+0x16/0x20
[    6.065075]  ? pcpu_alloc+0x1c3/0x690
[    6.065078]  ? mount_fs+0x36/0x162
[    6.099840]  mount_fs+0x36/0x162
[    6.099843]  vfs_kern_mount.part.34+0x4f/0x120
[    6.099845]  do_mount+0x1f7/0xc80
[    6.099856]  ksys_mount+0xb5/0xd0
[    6.099859]  __x64_sys_mount+0x1c/0x20
[    6.099861]  do_syscall_64+0x43/0xd0
[    6.099864]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[    6.099866] RIP: 0033:0x7f0715b89a1a
[    6.099867] Code: 48 8b 0d 71 e4 0b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 3e e4 0b 00 f7 d8 64 89 01 48
[    6.123872] RSP: 002b:00007ffc0e3466a8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
[    6.131285] RAX: ffffffffffffffda RBX: 000055f3ed7ee9c0 RCX: 00007f0715b89a1a
[    6.131286] RDX: 000055f3ed7eebc0 RSI: 000055f3ed7eec40 RDI: 000055f3ed7ef900
[    6.131287] RBP: 00007f0715ecff04 R08: 000055f3ed7eec00 R09: 000055f3ed7eebc0
[    6.131288] R10: 00000000c0ed0400 R11: 0000000000000202 R12: 0000000000000000
[    6.131289] R13: 00000000c0ed0400 R14: 000055f3ed7ef900 R15: 000055f3ed7eebc0
[    6.131292] ---[ end trace bd5d30b2fea7fb77 ]---
[    6.251219] BTRFS info (device dm-3): checking UUID tree

Thanks,
--
Martin

On Fri, Oct 5, 2018 at 3:23 PM Martin Steigerwald

Quoted 5 lines

Hello!

On ThinkPad T520 after battery was discharged and machine just blacked out.

Quoted 2 lines

Is that some sign of regular consistency check / replay or something to investigate further?

I think it's harmless, if anything were messed up with link counts or mismatches between those and dir entries, fsck (btrfs check) should have reported something.
I'll dig a big further and remove the warning if it's really harmless.

Quoted 6 lines

I already scrubbed all data and there are no errors. Also btrfs device stats reports no errors. SMART status appears to be okay as well on both SSD.

[    4.524355] BTRFS info (device dm-4): disk space caching is

enabled [… backtrace …]