Re: [pbs-devel] [PATCH v4 proxmox-backup 09/11] datastore: use u64 instead of usize for fidx writer content size

[Christian Ebner <c.ebner@proxmox.com>]

Not sure about these changes, maybe other devs have a stronger opinion 
on this one.

If we do want to adapt this, then IMHO this should however be done 
throughout the whole codebase, for the dynamic index as well.


On 1/23/26 4:43 PM, Robert Obkircher wrote:
> This is closer to what the file format supports.
> 
> Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
> ---
>   pbs-datastore/src/datastore.rs   |  6 +--
>   pbs-datastore/src/fixed_index.rs | 69 ++++++++++++++++----------------
>   src/api2/backup/environment.rs   |  6 +--
>   src/api2/backup/mod.rs           |  2 +-
>   4 files changed, 42 insertions(+), 41 deletions(-)
> 
> diff --git a/pbs-datastore/src/datastore.rs b/pbs-datastore/src/datastore.rs
> index 56dfce6e..8770d942 100644
> --- a/pbs-datastore/src/datastore.rs
> +++ b/pbs-datastore/src/datastore.rs
> @@ -695,11 +695,11 @@ impl DataStore {
>       pub fn create_fixed_writer<P: AsRef<Path>>(
>           &self,
>           filename: P,
> -        size: Option<usize>,
> -        chunk_size: usize,
> +        size: Option<u64>,
> +        chunk_size: u32,

question: is this intentionally set to u32 instead of u64 like for other 
chunk sizes in this patch? Should be consistent ...

>       ) -> Result<FixedIndexWriter, Error> {
>           let full_path = self.inner.chunk_store.relative_path(filename.as_ref());
> -        FixedIndexWriter::create(full_path, size, chunk_size)
> +        FixedIndexWriter::create(full_path, size, chunk_size.into())
>       }
>   
>       pub fn open_fixed_reader<P: AsRef<Path>>(
> diff --git a/pbs-datastore/src/fixed_index.rs b/pbs-datastore/src/fixed_index.rs
> index 056ae07b..c2888372 100644
> --- a/pbs-datastore/src/fixed_index.rs
> +++ b/pbs-datastore/src/fixed_index.rs
> @@ -214,8 +214,8 @@ pub struct FixedIndexWriter {
>       file: File,
>       filename: PathBuf,
>       tmp_filename: PathBuf,
> -    chunk_size: usize,
> -    size: usize,
> +    chunk_size: u64,
> +    size: u64,
>       index_length: usize,
>       index_capacity: usize,
>       index: *mut u8,
> @@ -248,8 +248,8 @@ impl FixedIndexWriter {
>       // Requires obtaining a shared chunk store lock beforehand
>       pub fn create(
>           full_path: impl Into<PathBuf>,
> -        known_size: Option<usize>,
> -        chunk_size: usize,
> +        known_size: Option<u64>,
> +        chunk_size: u64,
>       ) -> Result<Self, Error> {
>           let full_path = full_path.into();
>           let mut tmp_path = full_path.clone();
> @@ -287,10 +287,13 @@ impl FixedIndexWriter {
>   
>           file.write_all(&buffer)?;
>   
> -        let (index_length, index_capacity) = known_size
> -            .map(|s| s.div_ceil(chunk_size))
> -            .map(|len| (len, len))
> -            .unwrap_or((0, Self::INITIAL_CAPACITY));
> +        let (index_length, index_capacity) = match known_size {
> +            Some(s) => {
> +                let len = s.div_ceil(chunk_size).try_into()?;
> +                (len, len)
> +            }
> +            None => (0, Self::INITIAL_CAPACITY),
> +        };
>   
>           let index_size = index_capacity * 32;
>           nix::unistd::ftruncate(&file, (header_size + index_size) as i64)?;
> @@ -376,13 +379,13 @@ impl FixedIndexWriter {
>       /// The size also becomes fixed as soon as it is no longer divisible
>       /// by the block size, to ensure that only the last block can be
>       /// smaller.
> -    fn grow_to_size(&mut self, requested_size: usize) -> Result<(), Error> {
> +    fn grow_to_size(&mut self, requested_size: u64) -> Result<(), Error> {
>           if self.size < requested_size {
>               if !self.growable_size {
>                   bail!("refusing to resize from {} to {requested_size}", self.size);
>               }
> -            let new_len = requested_size.div_ceil(self.chunk_size);
> -            if new_len * self.chunk_size != requested_size {
> +            let new_len = requested_size.div_ceil(self.chunk_size).try_into()?;
> +            if new_len as u64 * self.chunk_size != requested_size {
>                   // not a full chunk, so this must be the last one
>                   self.growable_size = false;
>                   self.set_index_capacity_or_unmap(new_len)?;
> @@ -463,12 +466,10 @@ impl FixedIndexWriter {
>           Ok(index_csum)
>       }
>   
> -    fn check_chunk_alignment(&self, offset: usize, chunk_len: usize) -> Result<usize, Error> {
> -        if offset < chunk_len {
> +    fn check_chunk_alignment(&self, offset: u64, chunk_len: u64) -> Result<usize, Error> {
> +        let Some(pos) = offset.checked_sub(chunk_len) else {
>               bail!("got chunk with small offset ({} < {}", offset, chunk_len);
> -        }
> -
> -        let pos = offset - chunk_len;
> +        };
>   
>           if offset > self.size {
>               bail!("chunk data exceeds size ({} >= {})", offset, self.size);
> @@ -490,7 +491,7 @@ impl FixedIndexWriter {
>               bail!("got unaligned chunk (pos = {})", pos);
>           }
>   
> -        Ok(pos / self.chunk_size)
> +        Ok((pos / self.chunk_size) as usize)
>       }
>   
>       fn add_digest(&mut self, index: usize, digest: &[u8; 32]) -> Result<(), Error> {
> @@ -524,12 +525,12 @@ impl FixedIndexWriter {
>       /// If this writer has been created without a fixed size, the
>       /// index capacity and content size are increased automatically
>       /// until an incomplete chunk is encountered.
> -    pub fn add_chunk(&mut self, start: u64, size: u32, digest: &[u8; 32]) -> Result<(), Error> {
> -        let Some(end) = start.checked_add(size.into()) else {
> +    pub fn add_chunk(&mut self, start: u64, size: u64, digest: &[u8; 32]) -> Result<(), Error> {
> +        let Some(end) = start.checked_add(size) else {
>               bail!("add_chunk: start and size are too large: {start}+{size}");
>           };
> -        self.grow_to_size(end as usize)?;
> -        let idx = self.check_chunk_alignment(end as usize, size as usize)?;
> +        self.grow_to_size(end)?;
> +        let idx = self.check_chunk_alignment(end, size)?;
>           self.add_digest(idx, digest)
>       }
>   
> @@ -538,7 +539,7 @@ impl FixedIndexWriter {
>               bail!("reusing the index is only supported with known input size");
>           }
>   
> -        if self.chunk_size != reader.chunk_size {
> +        if Ok(self.chunk_size) != reader.chunk_size.try_into() {
>               bail!("can't reuse file with different chunk size");
>           }
>   
> @@ -560,7 +561,7 @@ mod tests {
>       use std::env;
>       use std::fs;
>   
> -    const CS: usize = 4096;
> +    const CS: u64 = 4096;
>   
>       #[test]
>       fn test_empty() {
> @@ -606,7 +607,7 @@ mod tests {
>   
>           let initial = FixedIndexWriter::INITIAL_CAPACITY;
>           let steps = [1, 2, initial, initial + 1, 5 * initial, 10 * initial + 1];
> -        let expected = test_data(steps.last().unwrap() * CS);
> +        let expected = test_data(*steps.last().unwrap() as u64 * CS);
>   
>           let mut begin = 0;
>           for chunk_count in steps {
> @@ -623,7 +624,7 @@ mod tests {
>           w.close().unwrap();
>           drop(w);
>   
> -        let size = expected.len() * CS;
> +        let size = expected.len() as u64 * CS;
>           check_with_reader(&path, size, &expected);
>           compare_to_known_size_writer(&path, size, &expected);
>       }
> @@ -634,7 +635,7 @@ mod tests {
>           let path = dir.join("test_grow_to_misaligned_size");
>           let mut w = FixedIndexWriter::create(&path, None, CS).unwrap();
>   
> -        let size = (FixedIndexWriter::INITIAL_CAPACITY + 42) * CS - 1; // last is not full
> +        let size = (FixedIndexWriter::INITIAL_CAPACITY as u64 + 42) * CS - 1; // last is not full
>           let expected = test_data(size);
>   
>           w.grow_to_size(size).unwrap();
> @@ -677,8 +678,8 @@ mod tests {
>       struct TestChunk {
>           digest: [u8; 32],
>           index: usize,
> -        size: usize,
> -        end: usize,
> +        size: u64,
> +        end: u64,
>       }
>   
>       impl TestChunk {
> @@ -691,7 +692,7 @@ mod tests {
>           }
>       }
>   
> -    fn test_data(size: usize) -> Vec<TestChunk> {
> +    fn test_data(size: u64) -> Vec<TestChunk> {
>           (0..size.div_ceil(CS))
>               .map(|index| {
>                   let mut digest = [0u8; 32];
> @@ -706,24 +707,24 @@ mod tests {
>                   };
>                   TestChunk {
>                       digest,
> -                    index,
> +                    index: index as usize,
>                       size,
> -                    end: index * CS + size,
> +                    end: index as u64 * CS + size,
>                   }
>               })
>               .collect()
>       }
>   
> -    fn check_with_reader(path: &Path, size: usize, chunks: &[TestChunk]) {
> +    fn check_with_reader(path: &Path, size: u64, chunks: &[TestChunk]) {
>           let reader = FixedIndexReader::open(path).unwrap();
> -        assert_eq!(size as u64, reader.index_bytes());
> +        assert_eq!(size, reader.index_bytes());
>           assert_eq!(chunks.len(), reader.index_count());
>           for c in chunks {
>               assert_eq!(&c.digest, reader.index_digest(c.index).unwrap());
>           }
>       }
>   
> -    fn compare_to_known_size_writer(file: &Path, size: usize, chunks: &[TestChunk]) {
> +    fn compare_to_known_size_writer(file: &Path, size: u64, chunks: &[TestChunk]) {
>           let mut path = file.to_path_buf();
>           path.set_extension("reference");
>           let mut w = FixedIndexWriter::create(&path, Some(size), CS).unwrap();
> diff --git a/src/api2/backup/environment.rs b/src/api2/backup/environment.rs
> index 04c5bf84..7d49d47c 100644
> --- a/src/api2/backup/environment.rs
> +++ b/src/api2/backup/environment.rs
> @@ -67,7 +67,7 @@ struct DynamicWriterState {
>   struct FixedWriterState {
>       name: String,
>       index: FixedIndexWriter,
> -    size: Option<usize>,
> +    size: Option<u64>,
>       chunk_size: u32,
>       chunk_count: u64,
>       small_chunk_count: usize, // allow 0..1 small chunks (last chunk may be smaller)
> @@ -349,7 +349,7 @@ impl BackupEnvironment {
>           &self,
>           index: FixedIndexWriter,
>           name: String,
> -        size: Option<usize>,
> +        size: Option<u64>,
>           chunk_size: u32,
>           incremental: bool,
>       ) -> Result<usize, Error> {
> @@ -442,7 +442,7 @@ impl BackupEnvironment {
>               );
>           }
>   
> -        data.index.add_chunk(offset, size, digest)?;
> +        data.index.add_chunk(offset, size.into(), digest)?;
>   
>           data.chunk_count += 1;
>   
> diff --git a/src/api2/backup/mod.rs b/src/api2/backup/mod.rs
> index c2822c18..54445efa 100644
> --- a/src/api2/backup/mod.rs
> +++ b/src/api2/backup/mod.rs
> @@ -480,7 +480,7 @@ fn create_fixed_index(
>       let env: &BackupEnvironment = rpcenv.as_ref();
>   
>       let name = required_string_param(&param, "archive-name")?.to_owned();
> -    let size = param["size"].as_u64().map(usize::try_from).transpose()?;
> +    let size = param["size"].as_u64();
>       let reuse_csum = param["reuse-csum"].as_str();
>   
>       let archive_name = name.clone();



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