Cscrub

This is a tool to check btrfs checksums on whole filesystem.

Supported data profiles

• Single
• BTRFS_BLOCK_GROUP_RAID5
• BTRFS_BLOCK_GROUP_RAID6
• BTRFS_BLOCK_GROUP_RAID0
• BTRFS_BLOCK_GROUP_RAID1
• BTRFS_BLOCK_GROUP_DUP (slow)
• BTRFS_BLOCK_GROUP_RAID1C3
• BTRFS_BLOCK_GROUP_RAID1C4

Not supported raid10

Compilation

• install libaio(-dev)
• gcc -o cscrub -O2 -fopenmp -Wall -Wextra -pedantic -std=c11 *.c -lpthread -laio

Usage

cscrub /mount/point

Caveats

Dup profile checking is slow and seeky, as the code things the allocations are on different disks. Probably not worth fixing.

The code is subject to race conditions causing false positives on disk stripes that see new writes during operation.

Currently only checksum checking is implemented and other means have to be used for repair, like file rewrites. This feature could be added, but this would maybe require adding code to recheck failures for false positives using some more stable slow path. Checksums could be repaired by relocating the block group with balance, reading the file (if appropriate) or rewriting the file contents and using EXTENT_SAME ioctl to replace the broken data.

Big endian is not supported, adding support is trivial but would require at least testing.

Reporting bugs

Currently github is used to track bugs.

Unless the bug is quite obvious, attach at least output of

btrfs inspect-internal dump-tree -t 3 /dev/mapper/home