OXYGENHUB

Re-read a pinned file from the disk before calling its hash wrong ab3204b9974b

A mismatch drops the file's cached pages (posix_fadvise DONTNEED) and
hashes it again; when the disk's copy is right, a warning says the
cached copy was bad. earth-1 failed every job on the rust image for
three hours through one bad cached page while the file was intact.

closes #22
Author
Andy McCall @andymccall <[email protected]>
When
· 2026-10-02 20:23 UTC
Signature
✔ signed by Andy McCall
Hash
ab3204b9974bba7d93682a006d2d88fc713dd77052440e87687c16a344ae264c
Depends on
e0918b887850
Depended on by
nothing yet
In bookmarks
main newer-pipeline push-uses-login
In tags
v0.2.0 v0.3.0 v0.3.1 v0.4.0 v0.5.0 v0.5.1 v0.5.2 v0.5.3
Edits
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modified crates/flow/src/home.rs +31 −1
… 
97 unchanged lines
98 98 
        if self.verified.lock().unwrap().get(path) == Some(&stamp) {
99 99 
            return Ok(path.to_path_buf());
100 100 
        }
101 - 
        let got = hash_file(path)?;
101 + 
        let mut got = hash_file(path)?;
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        if got != blake3_hex {
103 + 
            // The read may have come from bad cached pages rather than the
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            // disk (oxygenflow#22: a RAM fault on Earth failed every job for
105 + 
            // hours while the file was intact): drop the file's pages and
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            // read it again from the disk before giving up.
107 + 
            drop_cached(path);
108 + 
            let again = hash_file(path)?;
109 + 
            if again == blake3_hex {
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                eprintln!(
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                    "warning: {} hashed {got} from the page cache but {again} from the disk: the cached copy was bad (check this machine's memory)",
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                    path.display()
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                );
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            }
115 + 
            got = again;
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        }
117 + 
        if got != blake3_hex {
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            bail!("{} has BLAKE3 {got}, but {blake3_hex} is pinned", path.display());
104 119 
        }
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        self.verified.lock().unwrap().insert(path.to_path_buf(), stamp);
106 121 
        Ok(path.to_path_buf())
122 + 
    }
123 + 
}
124 + 

    

  
    

      
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/// Ask the kernel to forget a file's cached pages, so the next read comes

    

  
    

      
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/// from the disk. Best effort: dirty pages and other platforms stay.

    

  
    

      
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fn drop_cached(path: &Path) {

    

  
    

      
      128
      +
      
    #[cfg(target_os = "linux")]

    

  
    

      
      129
      +
      
    if let Ok(f) = std::fs::File::open(path) {

    

  
    

      
      130
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        use std::os::fd::AsRawFd;

    

  
    

      
      131
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        // SAFETY: a valid descriptor; the advice only affects caching.

    

  
    

      
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        unsafe {

    

  
    

      
      133
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            libc::posix_fadvise(f.as_raw_fd(), 0, 0, libc::POSIX_FADV_DONTNEED);

    

  
    

      
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      +
      
        }

    

  
    

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    }

    

  
    

      
      136
      +
      
    #[cfg(not(target_os = "linux"))]

    

  
    

      
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    let _ = path;

    

  
    

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}

    

  
    

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pub fn hash_file(path: &Path) -> Result<String> {

    

  
    

      
      
      …
      
4 unchanged lines