From 0cba3d1a88a2cce1b9bb71e3d5d80d324d4f8f3a Mon Sep 17 00:00:00 2001
From: Patrick Mooney <pmooney@pfmooney.com>
Date: Tue, 9 Jan 2024 23:01:33 -0600
Subject: [PATCH] Add crucible-mem backend

---
 bin/propolis-standalone/src/config.rs | 32 ++++++++++++++++++++++
 lib/propolis/src/block/crucible.rs    | 39 +++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/bin/propolis-standalone/src/config.rs b/bin/propolis-standalone/src/config.rs
index b448ba3f8..e0df2912e 100644
--- a/bin/propolis-standalone/src/config.rs
+++ b/bin/propolis-standalone/src/config.rs
@@ -81,6 +81,7 @@ pub fn block_backend(
             (be, creg)
         }
         "crucible" => create_crucible_backend(be, opts, log),
+        "crucible-mem" => create_crucible_mem_backend(be, opts, log),
         "mem-async" => {
             let parsed: MemAsyncConfig = opt_deser(&be.options).unwrap();
 
@@ -256,6 +257,25 @@ fn create_crucible_backend(
     (be, creg)
 }
 
+#[cfg(feature = "crucible")]
+fn create_crucible_mem_backend(
+    be: &propolis_standalone_config::BlockDevice,
+    opts: block::BackendOpts,
+    log: &slog::Logger,
+) -> (Arc<dyn block::Backend>, ChildRegister) {
+    #[derive(Deserialize)]
+    struct CrucibleMemConfig {
+        size: u64,
+    }
+    let parsed: CrucibleMemConfig = opt_deser(&be.options).unwrap();
+
+    let be = block::CrucibleBackend::create_mem(parsed.size, opts, log.clone())
+        .unwrap();
+    let creg =
+        ChildRegister::new(&be, Some(be.get_uuid().unwrap().to_string()));
+    (be, creg)
+}
+
 #[cfg(not(feature = "crucible"))]
 fn create_crucible_backend(
     _be: &propolis_standalone_config::BlockDevice,
@@ -267,3 +287,15 @@ fn create_crucible_backend(
            order to use the crucible block backend"
     );
 }
+
+#[cfg(not(feature = "crucible"))]
+fn create_crucible_mem_backend(
+    _be: &propolis_standalone_config::BlockDevice,
+    _opts: block::BackendOpts,
+    _log: &slog::Logger,
+) -> (Arc<dyn block::Backend>, ChildRegister) {
+    panic!(
+        "Rebuild propolis-standalone with 'crucible' feature enabled in \
+           order to use the crucible-mem block backend"
+    );
+}
diff --git a/lib/propolis/src/block/crucible.rs b/lib/propolis/src/block/crucible.rs
index c3bad7057..3a403e7e8 100644
--- a/lib/propolis/src/block/crucible.rs
+++ b/lib/propolis/src/block/crucible.rs
@@ -161,6 +161,45 @@ impl CrucibleBackend {
         }))
     }
 
+    /// Create Crucible backend using the in-memory volume backend, rather than
+    /// "real" Crucible downstairs instances.
+    pub fn create_mem(
+        size: u64,
+        opts: block::BackendOpts,
+        log: slog::Logger,
+    ) -> io::Result<Arc<Self>> {
+        let rt = tokio::runtime::Handle::current();
+        rt.block_on(async move {
+            let block_size = opts.block_size.ok_or_else(|| {
+                CrucibleError::GenericError(
+                    "block_size is required parameter".into(),
+                )
+            })? as u64;
+            // Allocate and construct the volume.
+            let mem_disk = Arc::new(crucible::InMemoryBlockIO::new(
+                Uuid::new_v4(),
+                block_size,
+                size as usize,
+            ));
+            let mut volume = Volume::new(block_size, log);
+            volume.add_subvolume(mem_disk).await?;
+
+            Ok(Arc::new(CrucibleBackend {
+                state: Arc::new(WorkerState {
+                    attachment: block::backend::Attachment::new(),
+                    volume,
+                    info: block::DeviceInfo {
+                        block_size: block_size as u32,
+                        total_size: size / block_size,
+                        read_only: opts.read_only.unwrap_or(false),
+                    },
+                    skip_flush: opts.skip_flush.unwrap_or(false),
+                }),
+            }))
+        })
+        .map_err(CrucibleError::into)
+    }
+
     // Communicate to Nexus that we can remove the read only parent for
     // the given volume id.
     async fn remove_read_only_parent(