Port and simplify raw-file-v2

Cargo.toml

@@ -110,6 +110,7 @@ tracing-subscriber = "0.3.18"
 twox-hash = "1.6.3"
 usdt = "0.5.0"
 uuid = { version = "1", features = [ "serde", "v4" ] }
+zerocopy = "0.7.32"
 
 # git
 dropshot = { git = "https://github.com/oxidecomputer/dropshot", branch = "main", features = [ "usdt-probes" ] }

downstairs/Cargo.toml

@@ -54,6 +54,7 @@ tracing-subscriber.workspace = true
 tracing.workspace = true
 usdt.workspace = true
 uuid.workspace = true
+zerocopy.workspace = true
 crucible-workspace-hack.workspace = true
 
 [dev-dependencies]

downstairs/src/extent.rs

@@ -141,6 +141,7 @@ pub const EXTENT_META_SQLITE: u32 = 1;
 ///
 /// See [`extent_inner_raw::RawInner`] for the implementation.
 pub const EXTENT_META_RAW: u32 = 2;
+pub const EXTENT_META_RAW_V2: u32 = 3;
 
 impl ExtentMeta {
     pub fn new(ext_version: u32) -> ExtentMeta {
@@ -445,6 +446,11 @@ impl Extent {
                             dir, def, number, read_only, log,
                         )?)
                     }
+                    EXTENT_META_RAW_V2 => {
+                        Box::new(extent_inner_raw_v2::RawInnerV2::open(
+                            dir, def, number, read_only, log,
+                        )?)
+                    }
                     i => {
                         return Err(CrucibleError::IoError(format!(
                             "raw extent {number} has unknown tag {i}"
@@ -507,9 +513,13 @@ impl Extent {
         remove_copy_cleanup_dir(dir, number)?;
 
         let inner: Box<dyn ExtentInner + Send + Sync> = match backend {
+            #[cfg(any(test, feature = "integration-tests"))]
             Backend::RawFile => {
                 Box::new(extent_inner_raw::RawInner::create(dir, def, number)?)
             }
+            Backend::RawFileV2 => Box::new(
+                extent_inner_raw_v2::RawInnerV2::create(dir, def, number)?,
+            ),
             #[cfg(any(test, feature = "integration-tests"))]
             Backend::SQLite => Box::new(
                 extent_inner_sqlite::SqliteInner::create(dir, def, number)?,