btrfs-cli 0.12.0

User-space command-line tool for inspecting and managing Btrfs filesystems
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134

use super::errors::{CheckError, CheckResults};
use btrfs_disk::{
    reader::{self, BlockReader},
    superblock::{ChecksumType, Superblock},
    tree::{KeyType, TreeBlock},
    util::btrfs_csum_data,
};
use std::io::{Read, Seek};

/// Header size in a btrfs tree block (bytes before item data area).
const HEADER_SIZE: usize = std::mem::size_of::<btrfs_disk::raw::btrfs_header>();

/// Check the checksum tree structure and optionally verify data checksums.
pub fn check_csums<R: Read + Seek>(
    reader: &mut BlockReader<R>,
    sb: &Superblock,
    csum_root: u64,
    verify_data: bool,
    results: &mut CheckResults,
) {
    let csum_size = sb.csum_type.size() as u64;
    let sectorsize = u64::from(sb.sectorsize);
    let mut total_csum_bytes = 0u64;
    let mut read_errors: Vec<(u64, String)> = Vec::new();

    let csum_type = sb.csum_type;
    let can_verify = verify_data && csum_type == ChecksumType::Crc32;

    if verify_data && !can_verify {
        eprintln!(
            "warning: --check-data-csum not supported for \
             checksum type {}, skipping data verification",
            sb.csum_type
        );
    }

    // Collect csum items for potential data verification.
    let mut csum_items: Vec<CsumEntry> = Vec::new();

    let mut visitor = |_raw: &[u8], block: &TreeBlock| {
        if let TreeBlock::Leaf { items, data, .. } = block {
            for item in items {
                if item.key.key_type != KeyType::ExtentCsum {
                    continue;
                }
                let start = HEADER_SIZE + item.offset as usize;
                let item_data = &data[start..][..item.size as usize];

                // Each csum item covers a contiguous range of sectors.
                // The key offset is the logical byte address of the first
                // sector. The item data contains one checksum per sector.
                let logical_start = item.key.offset;
                let num_csums = item_data.len() as u64 / csum_size;
                total_csum_bytes += item_data.len() as u64;

                if can_verify {
                    csum_items.push(CsumEntry {
                        logical_start,
                        num_csums,
                        sectorsize,
                        csum_data: item_data.to_vec(),
                        #[allow(clippy::cast_possible_truncation)] // csum_size always small
                        csum_size: csum_size as usize,
                    });
                }
            }
        }
    };

    let mut on_error = |logical: u64, err: &std::io::Error| {
        read_errors.push((logical, err.to_string()));
    };

    if let Err(e) = reader::tree_walk_tolerant(
        reader,
        csum_root,
        &mut visitor,
        &mut on_error,
    ) {
        results.report(CheckError::ReadError {
            logical: csum_root,
            detail: format!("csum tree root: {e}"),
        });
        return;
    }

    for (logical, detail) in read_errors {
        results.report(CheckError::ReadError { logical, detail });
    }

    results.total_csum_bytes = total_csum_bytes;

    // Verify data checksums if requested and supported.
    if can_verify {
        verify_data_csums(reader, &csum_items, results);
    }
}

struct CsumEntry {
    logical_start: u64,
    num_csums: u64,
    sectorsize: u64,
    csum_data: Vec<u8>,
    csum_size: usize,
}

fn verify_data_csums<R: Read + Seek>(
    reader: &mut BlockReader<R>,
    entries: &[CsumEntry],
    results: &mut CheckResults,
) {
    for entry in entries {
        for i in 0..entry.num_csums {
            let logical = entry.logical_start + i * entry.sectorsize;
            #[allow(clippy::cast_possible_truncation)] // index fits in usize
            let csum_off = (i as usize) * entry.csum_size;
            let stored = &entry.csum_data[csum_off..csum_off + entry.csum_size];

            #[allow(clippy::cast_possible_truncation)]
            // sectorsize fits in usize
            let Ok(data) = reader.read_data(logical, entry.sectorsize as usize)
            else {
                results.report(CheckError::CsumMismatch { logical });
                continue;
            };

            let computed = btrfs_csum_data(&data);
            let expected = u32::from_le_bytes(stored[..4].try_into().unwrap());
            if computed != expected {
                results.report(CheckError::CsumMismatch { logical });
            }
        }
    }
}