btrfs-zero-log (8)

btrfs-zero-log <dev>

btrfs-zero-log will remove the log tree if log tree is corrupt, which will allow you to mount the filesystem again.

The common case where this happens has been fixed a long time ago, so it is unlikely that you will see this particular problem.

One can determine whether btrfs-zero-log is needed according to the kernel backtrace:

? replay_one_dir_item+0xb5/0xb5 [btrfs]
? walk_log_tree+0x9c/0x19d [btrfs]
? btrfs_read_fs_root_no_radix+0x169/0x1a1 [btrfs]
? btrfs_recover_log_trees+0x195/0x29c [btrfs]
? replay_one_dir_item+0xb5/0xb5 [btrfs]
? btree_read_extent_buffer_pages+0x76/0xbc [btrfs]
? open_ctree+0xff6/0x132c [btrfs]

If the errors are like above, then btrfs-zero-log should be used to clear the log and the filesystem may be mounted normally again.

Note

If you use btrfs as the root filesystem, you may want to include btrfs-zero-log into initramdisk if the log problems hits you often.

btrfs-zero-log will return 0 if no error happened. Other exit code means some problems happened.

mkfs.btrfs(8)