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#1 2025-07-13 17:53:24

860lacov
Member
Registered: 2020-05-02
Posts: 491

System failed to boot – Btrfs log tree error

Hi,

Today my system failed to boot with the following error:

BTRFS: error [...] failed to recover log tree
Failed to mount /sysroot

What I did:

    Mounted the root volume using:
    

    mount -o ro,rescue=all /dev/mapper/cryptroot /mnt

    Subvolumes were accessible, so I made a full backup using:
    

    rsync -aAX /mnt /external/backup

   
    Entered arch-chroot, ran:
    

    mkinitcpio -P

    → system still wouldn't boot

    Then I ran:
    

    btrfs check --repair /dev/mapper/cryptroot

    → log tree was cleared, system became mountable again

    After that I used:
    

    btrfs send -e /mnt/@ /mnt/@home | btrfs receive -e /external/snapshots

    → to create clean subvolume backups

Noticed:
btrfs check output before and after repair showed this difference:

Before: 747492561376 bytes used
After: 747492040704 bytes used

Current status:
System boots normally now and seems functional.
But I’m not sure if the filesystem is in a safe and consistent state long-term.

I'd appreciate any advice on whether everything looks OK.
Here are the outputs I've gathered:

$ sudo btrfs device stats /
[sudo] hasło użytkownika jm: 
[/dev/mapper/cryptroot].write_io_errs    0
[/dev/mapper/cryptroot].read_io_errs     0
[/dev/mapper/cryptroot].flush_io_errs    0
[/dev/mapper/cryptroot].corruption_errs  0
[/dev/mapper/cryptroot].generation_errs  0
$ sudo btrfs scrub status /
Total to scrub:   698.14GiB
Rate:             0.00B/s
Error summary:    no errors found
$ journalctl -p err..alert -b
lip 13 17:51:23 p14s systemd[1]: Failed to start Refresh Pacman mirrorlist with Reflector..
lip 13 17:56:21 p14s org_kde_powerdevil[1553]: Failed to find connector name for /dev/i2c-10, set_connector_for_businfo_using_edid at line 1236 in file i2c_bus_core.c.
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    I2C_Bus_Info at: 0x5572c96ba490
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Flags:                   I2C_BUS_EXISTS | I2C_BUS_ACCESSIBLE | I2C_BUS_PROBED | I2C_BUS_X50_EDID | I2C_BUS_SYSFS_KNOWN_RELIABLE
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Bus /dev/i2c-10 found:   true
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Bus /dev/i2c-10 probed:  true
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    errno for open:          OK(0): success
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    drm_connector_found_by:  DRM_CONNECTOR_NOT_CHECKED (0)
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    last_checked_asleep:       false
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Display connectors reported by /sys:
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Connector:    card1-HDMI-A-1
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       i2c_busno:    3
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       connector_id: 101
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       name:         (null)
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       enabled:      disabled
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       status:       disconnected
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       edid:         None
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Connector:    card1-DP-1
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       i2c_busno:    11
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       connector_id: 108
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       name:         (null)
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       enabled:      disabled
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       status:       disconnected
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       edid:         None
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Connector:    card1-DP-2
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       i2c_busno:    12
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       connector_id: 115
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       name:         (null)
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       enabled:      disabled
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       status:       disconnected
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       edid:         None
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Connector:    card1-DP-3
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       i2c_busno:    13
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       connector_id: 121
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       name:         (null)
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       enabled:      disabled
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       status:       disconnected
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       edid:         None
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Connector:    card1-DP-4
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       i2c_busno:    14
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       connector_id: 127
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       name:         (null)
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       enabled:      disabled
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       status:       disconnected
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       edid:         None
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Connector:    card1-DP-5
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       i2c_busno:    15
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       connector_id: 133
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       name:         (null)
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       enabled:      disabled
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       status:       disconnected
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       edid:         None
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Connector:    card1-DP-6
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       i2c_busno:    16
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       connector_id: 139
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       name:         (null)
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       enabled:      disabled
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       status:       disconnected
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       edid:         None
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Connector:    card1-eDP-1
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       i2c_busno:    2
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       connector_id: 93
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       name:         (null)
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       enabled:      enabled
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       status:       connected
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       edid:
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:         +0          +4          +8          +c            0   4   8   c
lip 13 17:56:21 p14s org_kde_powerdevil[1553]: +0000   00 ff ff ff ff ff ff 00 30 ae 3a 40 00 00 00 00   ........0.:@....
lip 13 17:56:21 p14s org_kde_powerdevil[1553]: +0010   00 1e 01 04 a5 1e 13 78 e3 78 bc a4 55 4c 9b 24   .......x.x..UL.$
lip 13 17:56:21 p14s org_kde_powerdevil[1553]: +0020   0d 4f 54 00 00 00 01 01 01 01 01 01 01 01 01 01   .OT.............
lip 13 17:56:21 p14s org_kde_powerdevil[1553]: +0030   01 01 01 01 01 01 35 3c 80 a0 70 b0 23 40 30 20   ......5<..p.#@0
lip 13 17:56:21 p14s org_kde_powerdevil[1553]: +0040   36 00 2e bd 10 00 00 18 00 00 00 fd 00 28 3c 4a   6............(<J
lip 13 17:56:21 p14s org_kde_powerdevil[1553]: +0050   4a 0f 01 0a 20 20 20 20 20 20 00 00 00 0f 00 d1   J...      ......
lip 13 17:56:21 p14s org_kde_powerdevil[1553]: +0060   0a 28 d1 0a 28 28 0a 04 0e 6f 04 14 00 00 00 fe   .(..((...o......
lip 13 17:56:21 p14s org_kde_powerdevil[1553]: +0070   00 4d 4e 45 30 30 37 4a 41 31 2d 31 0a 20 00 4d   .MNE007JA1-1. .M
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:    Connector:    card1-Writeback-1
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       i2c_busno:    -1
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       connector_id: 145
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       name:         (null)
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       enabled:      disabled
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       status:       unknown
lip 13 17:56:21 p14s org_kde_powerdevil[1553]:       edid:         None

I know that --repair could be dangerous, but after backing up the data I decided to give it a chance.
Not sure where else I should look for important signs of system issues — any advice is welcome

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#2 2025-07-13 18:36:29

topcat01
Member
Registered: 2019-09-17
Posts: 238

Re: System failed to boot – Btrfs log tree error

In future, when you you have a log tree error, which indicates that the filesystem is fine, but there was a problem replaying the last few journal log entries (unclean shutdown?), instead of --repair you can just clear the log tree (safe) using:

btrfs-rescue zero-log /dev/mapper/cryptroot

since we know that the log is the problem. Otherwise things should be fine.

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#3 2025-07-13 19:47:51

860lacov
Member
Registered: 2020-05-02
Posts: 491

Re: System failed to boot – Btrfs log tree error

topcat01 wrote:

In future, when you you have a log tree error, which indicates that the filesystem is fine, but there was a problem replaying the last few journal log entries (unclean shutdown?), instead of --repair you can just clear the log tree (safe) using:

btrfs-rescue zero-log /dev/mapper/cryptroot

since we know that the log is the problem. Otherwise things should be fine.

I use btrfs for many years.
Never had a problem before so I knew about snapshots, send | receive functionality etc.

Lesson learned. Thank you.

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#4 2025-07-29 14:05:23

darcmage
Member
Registered: 2021-07-22
Posts: 11

Re: System failed to boot – Btrfs log tree error

Apologies if this has already been addressed.

Increased reports since 6.15.3 of corruption within the log tree
Fedora KDE no longer booting, likely filesystem (BTRFS) corruption

Seems like it's still an issue with latest stable kernel. Has the cause been found?

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#5 2025-07-29 22:09:02

topcat01
Member
Registered: 2019-09-17
Posts: 238

Re: System failed to boot – Btrfs log tree error

Thanks for the links. Even though some new bugs may have been introduced, I think overall the new updates are a good thing. It just needs a bit more testing and time to settle. It seems the developer is already looking into it so fingers crossed.

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