[cache (rust)] Implement Pack for superblock

src/cache/superblock.rs

@@ -1,14 +1,19 @@
 use anyhow::{anyhow, Result};
+use byteorder::{LittleEndian, WriteBytesExt};
 use nom::{bytes::complete::*, number::complete::*, IResult};
+use std::io::Cursor;
 
+use crate::checksum::*;
 use crate::io_engine::*;
 
 //------------------------------------------
 
+pub const SPACE_MAP_ROOT_SIZE: usize = 128;
 pub const SUPERBLOCK_LOCATION: u64 = 0;
 
+const MAGIC: u64 = 0o6142003; // 0x18c403 in hex
 const POLICY_NAME_SIZE: usize = 16;
-const SPACE_MAP_ROOT_SIZE: usize = 128;
+const UUID_SIZE: usize = 16;
 
 //------------------------------------------
 
@@ -38,7 +43,6 @@ pub struct Superblock {
     pub discard_nr_blocks: u64,
 
     pub data_block_size: u32,
-    pub metadata_block_size: u32,
     pub cache_blocks: u32,
 
     pub compat_flags: u32,
@@ -71,7 +75,7 @@ fn unpack(data: &[u8]) -> IResult<&[u8], Superblock> {
     let (i, discard_nr_blocks) = le_u64(i)?;
 
     let (i, data_block_size) = le_u32(i)?;
-    let (i, metadata_block_size) = le_u32(i)?;
+    let (i, _metadata_block_size) = le_u32(i)?;
     let (i, cache_blocks) = le_u32(i)?;
 
     let (i, compat_flags) = le_u32(i)?;
@@ -115,7 +119,6 @@ fn unpack(data: &[u8]) -> IResult<&[u8], Superblock> {
             discard_block_size,
             discard_nr_blocks,
             data_block_size,
-            metadata_block_size,
             cache_blocks,
             compat_flags,
             compat_ro_flags,
@@ -139,3 +142,79 @@ pub fn read_superblock(engine: &dyn IoEngine, loc: u64) -> Result<Superblock> {
 }
 
 //------------------------------------------
+
+fn pack_superblock<W: WriteBytesExt>(sb: &Superblock, w: &mut W) -> Result<()> {
+    // checksum, which we don't know yet
+    w.write_u32::<LittleEndian>(0)?;
+
+    // flags
+    let mut flags: u32 = 0;
+    if sb.flags.clean_shutdown {
+        flags |= 0x1;
+    }
+    if sb.flags.needs_check {
+        flags |= 0x2;
+    }
+    w.write_u32::<LittleEndian>(flags)?;
+
+    w.write_u64::<LittleEndian>(sb.block)?;
+    w.write_all(&[0; UUID_SIZE])?;
+    w.write_u64::<LittleEndian>(MAGIC)?;
+    w.write_u32::<LittleEndian>(sb.version)?;
+
+    let mut policy_name = [0u8; POLICY_NAME_SIZE];
+    policy_name[..sb.policy_name.len()].copy_from_slice(&sb.policy_name[..]);
+    w.write_all(&policy_name)?;
+
+    w.write_u32::<LittleEndian>(sb.policy_hint_size)?;
+    w.write_all(&[0; SPACE_MAP_ROOT_SIZE])?; // metadata sm root
+    w.write_u64::<LittleEndian>(sb.mapping_root)?;
+    w.write_u64::<LittleEndian>(sb.hint_root)?;
+
+    w.write_u64::<LittleEndian>(sb.discard_root)?;
+    w.write_u64::<LittleEndian>(sb.discard_block_size)?;
+    w.write_u64::<LittleEndian>(sb.discard_nr_blocks)?;
+
+    w.write_u32::<LittleEndian>(sb.data_block_size)?;
+    // metadata block size
+    w.write_u32::<LittleEndian>((BLOCK_SIZE >> SECTOR_SHIFT) as u32)?;
+    w.write_u32::<LittleEndian>(sb.cache_blocks)?;
+
+    w.write_u32::<LittleEndian>(sb.compat_flags)?;
+    w.write_u32::<LittleEndian>(sb.compat_ro_flags)?;
+    w.write_u32::<LittleEndian>(sb.incompat_flags)?;
+
+    w.write_u32::<LittleEndian>(sb.read_hits)?;
+    w.write_u32::<LittleEndian>(sb.read_misses)?;
+    w.write_u32::<LittleEndian>(sb.write_hits)?;
+    w.write_u32::<LittleEndian>(sb.write_misses)?;
+
+    w.write_u32::<LittleEndian>(sb.policy_version[0])?;
+    w.write_u32::<LittleEndian>(sb.policy_version[1])?;
+    w.write_u32::<LittleEndian>(sb.policy_version[2])?;
+
+    if sb.dirty_root.is_some() {
+        w.write_u64::<LittleEndian>(sb.dirty_root.unwrap())?;
+    }
+
+    Ok(())
+}
+
+pub fn write_superblock(engine: &dyn IoEngine, _loc: u64, sb: &Superblock) -> Result<()> {
+    let b = Block::zeroed(SUPERBLOCK_LOCATION);
+
+    // pack the superblock
+    {
+        let mut cursor = Cursor::new(b.get_data());
+        pack_superblock(sb, &mut cursor)?;
+    }
+
+    // calculate the checksum
+    write_checksum(b.get_data(), BT::CACHE_SUPERBLOCK)?;
+
+    // write
+    engine.write(&b)?;
+    Ok(())
+}
+
+//------------------------------------------

src/io_engine.rs

@@ -17,6 +17,7 @@ use crate::file_utils;
 //------------------------------------------
 
 pub const BLOCK_SIZE: usize = 4096;
+pub const SECTOR_SHIFT: usize = 9;
 const ALIGN: usize = 4096;
 
 #[derive(Clone, Debug)]