Bump crucible and update APIs (#663)

Bump crucible, add read_bytes_uninit

Author: mkeeter

Cargo.lock

@@ -78,8 +78,8 @@ oximeter-producer = { git = "https://github.com/oxidecomputer/omicron", branch =
 oximeter = { git = "https://github.com/oxidecomputer/omicron", branch = "main" }
 
 # Crucible
-crucible = { git = "https://github.com/oxidecomputer/crucible", rev = "1c1574fb721f98f2df1b23e3fd27d83be018882e" }
-crucible-client-types = { git = "https://github.com/oxidecomputer/crucible", rev = "1c1574fb721f98f2df1b23e3fd27d83be018882e" }
+crucible = { git = "https://github.com/oxidecomputer/crucible", rev = "952c7d60d22be5198b892bec8d92f4291b9160c2" }
+crucible-client-types = { git = "https://github.com/oxidecomputer/crucible", rev = "952c7d60d22be5198b892bec8d92f4291b9160c2" }
 
 # External dependencies
 anyhow = "1.0"

Cargo.toml

@@ -391,17 +391,24 @@ async fn process_request(
             // to crucible
             let maps =
                 req.mappings(mem).ok_or_else(|| Error::BadGuestRegion)?;
-            let mut vec: Vec<u8> = vec![0; len];
+            let mut data = crucible::BytesMut::with_capacity(len);
             let mut nread = 0;
             for mapping in maps {
-                nread += mapping
-                    .read_bytes(&mut vec[nread..(nread + mapping.len())])?;
+                let n = mapping.read_bytes_uninit(
+                    &mut data.spare_capacity_mut()[..mapping.len()],
+                )?;
+                // `read_bytes` returns the number of bytes written, so we can
+                // expand our initialized area by this amount.
+                unsafe {
+                    data.set_len(data.len() + n);
+                }
+                nread += n;
             }
             if nread != len {
                 return Err(Error::CopyError(nread, len));
             }
 
-            let _ = block.write(off_blocks, crucible::Bytes::from(vec)).await?;
+            let _ = block.write(off_blocks, data).await?;
         }
         block::Operation::Flush => {
             if !skip_flush {

lib/propolis/src/block/crucible.rs

@@ -6,7 +6,7 @@
 
 use std::io::{Error, ErrorKind, Result};
 use std::marker::PhantomData;
-use std::mem::{size_of, size_of_val};
+use std::mem::{size_of, size_of_val, MaybeUninit};
 use std::ops::RangeInclusive;
 use std::os::unix::io::{AsRawFd, RawFd};
 use std::ptr::{copy_nonoverlapping, NonNull};
@@ -532,6 +532,21 @@ impl<'a> SubMapping<'a> {
         Ok(read_len)
     }
 
+    /// Reads a buffer of bytes from the mapping into an uninitialized region
+    ///
+    /// If `buf` is larger than the SubMapping, the read will be truncated to
+    /// length of the SubMapping.
+    ///
+    /// Returns the number of bytes read.
+    pub fn read_bytes_uninit(
+        &self,
+        buf: &mut [MaybeUninit<u8>],
+    ) -> Result<usize> {
+        let read_len = usize::min(buf.len(), self.len);
+        self.read_many(&mut buf[..read_len])?;
+        Ok(read_len)
+    }
+
     /// Pread from `file` into the mapping.
     pub fn pread(
         &self,