diff --git a/src/bin/thin_check.rs b/src/bin/thin_check.rs
index b7fbad9..f353f86 100644
--- a/src/bin/thin_check.rs
+++ b/src/bin/thin_check.rs
@@ -97,8 +97,7 @@ fn main() {
         report = Arc::new(mk_simple_report());
     }
 
-    if matches.is_present("SYNC_IO") &&
-    matches.is_present("ASYNC_IO") {
+    if matches.is_present("SYNC_IO") && matches.is_present("ASYNC_IO") {
         eprintln!("--sync-io and --async-io may not be used at the same time.");
         process::exit(1);
     }
diff --git a/src/cache/check.rs b/src/cache/check.rs
index 92895e1..265b505 100644
--- a/src/cache/check.rs
+++ b/src/cache/check.rs
@@ -1,13 +1,13 @@
 use anyhow::anyhow;
+use std::collections::*;
 use std::marker::PhantomData;
 use std::path::Path;
 use std::sync::{Arc, Mutex};
-use std::collections::*;
 
-use crate::io_engine::{AsyncIoEngine, IoEngine, SyncIoEngine};
 use crate::cache::hint::*;
 use crate::cache::mapping::*;
 use crate::cache::superblock::*;
+use crate::io_engine::{AsyncIoEngine, IoEngine, SyncIoEngine};
 use crate::pdata::array_walker::*;
 
 //------------------------------------------
@@ -112,19 +112,13 @@ fn mk_context(opts: &CacheCheckOptions) -> anyhow::Result<Context> {
     let engine: Arc<dyn IoEngine + Send + Sync>;
 
     if opts.async_io {
-        engine = Arc::new(AsyncIoEngine::new(
-            opts.dev,
-            MAX_CONCURRENT_IO,
-            false,
-        )?);
+        engine = Arc::new(AsyncIoEngine::new(opts.dev, MAX_CONCURRENT_IO, false)?);
     } else {
         let nr_threads = std::cmp::max(8, num_cpus::get() * 2);
         engine = Arc::new(SyncIoEngine::new(opts.dev, nr_threads, false)?);
     }
 
-    Ok(Context {
-        engine,
-    })
+    Ok(Context { engine })
 }
 
 pub fn check(opts: CacheCheckOptions) -> anyhow::Result<()> {
@@ -145,7 +139,7 @@ pub fn check(opts: CacheCheckOptions) -> anyhow::Result<()> {
         w.walk(c, sb.mapping_root)?;
 
         if sb.version >= 2 {
-           // TODO: check dirty bitset
+            // TODO: check dirty bitset
         }
     }
 
diff --git a/src/cache/hint.rs b/src/cache/hint.rs
index ef0d83f..ea7f2d3 100644
--- a/src/cache/hint.rs
+++ b/src/cache/hint.rs
@@ -1,6 +1,6 @@
 use nom::IResult;
-use std::marker::PhantomData;
 use std::convert::TryInto;
+use std::marker::PhantomData;
 
 use crate::pdata::unpack::*;
 
diff --git a/src/cache/mapping.rs b/src/cache/mapping.rs
index c18325a..4370937 100644
--- a/src/cache/mapping.rs
+++ b/src/cache/mapping.rs
@@ -1,5 +1,5 @@
-use nom::IResult;
 use nom::number::complete::*;
+use nom::IResult;
 
 use crate::pdata::unpack::*;
 
@@ -26,7 +26,6 @@ impl Mapping {
     }
 }
 
-
 impl Unpack for Mapping {
     fn disk_size() -> u32 {
         8
diff --git a/src/cache/xml.rs b/src/cache/xml.rs
index d39b057..e811b67 100644
--- a/src/cache/xml.rs
+++ b/src/cache/xml.rs
@@ -100,7 +100,8 @@ impl<W: Write> MetadataVisitor for XmlWriter<W> {
     }
 
     fn superblock_e(&mut self) -> Result<Visit> {
-        self.w.write_event(Event::End(BytesEnd::borrowed(b"superblock")))?;
+        self.w
+            .write_event(Event::End(BytesEnd::borrowed(b"superblock")))?;
         Ok(Visit::Continue)
     }
 
@@ -112,10 +113,11 @@ impl<W: Write> MetadataVisitor for XmlWriter<W> {
     }
 
     fn mappings_e(&mut self) -> Result<Visit> {
-        self.w.write_event(Event::End(BytesEnd::borrowed(b"mappings")))?;
+        self.w
+            .write_event(Event::End(BytesEnd::borrowed(b"mappings")))?;
         Ok(Visit::Continue)
     }
-        
+
     fn mapping(&mut self, m: &Map) -> Result<Visit> {
         let tag = b"map";
         let mut elem = BytesStart::owned(tag.to_vec(), tag.len());
@@ -132,12 +134,13 @@ impl<W: Write> MetadataVisitor for XmlWriter<W> {
         self.w.write_event(Event::Start(elem))?;
         Ok(Visit::Continue)
     }
-    
+
     fn hints_e(&mut self) -> Result<Visit> {
-        self.w.write_event(Event::End(BytesEnd::borrowed(b"hints")))?;
+        self.w
+            .write_event(Event::End(BytesEnd::borrowed(b"hints")))?;
         Ok(Visit::Continue)
     }
-    
+
     fn hint(&mut self, h: &Hint) -> Result<Visit> {
         let tag = b"hint";
         let mut elem = BytesStart::owned(tag.to_vec(), tag.len());
@@ -153,12 +156,13 @@ impl<W: Write> MetadataVisitor for XmlWriter<W> {
         self.w.write_event(Event::Start(elem))?;
         Ok(Visit::Continue)
     }
-    
+
     fn discards_e(&mut self) -> Result<Visit> {
-        self.w.write_event(Event::End(BytesEnd::borrowed(b"discards")))?;
+        self.w
+            .write_event(Event::End(BytesEnd::borrowed(b"discards")))?;
         Ok(Visit::Continue)
     }
-    
+
     fn discard(&mut self, d: &Discard) -> Result<Visit> {
         let tag = b"discard";
         let mut elem = BytesStart::owned(tag.to_vec(), tag.len());
@@ -172,4 +176,3 @@ impl<W: Write> MetadataVisitor for XmlWriter<W> {
         Ok(Visit::Continue)
     }
 }
-
diff --git a/src/checksum.rs b/src/checksum.rs
index edb5e0a..675e6da 100644
--- a/src/checksum.rs
+++ b/src/checksum.rs
@@ -55,9 +55,11 @@ pub fn write_checksum(buf: &mut [u8], kind: BT) -> Result<()> {
         NODE => BTREE_CSUM_XOR,
         BITMAP => BITMAP_CSUM_XOR,
         INDEX => INDEX_CSUM_XOR,
-        UNKNOWN => {return Err(anyhow!("Invalid block type"));}
+        UNKNOWN => {
+            return Err(anyhow!("Invalid block type"));
+        }
     };
-    
+
     let csum = checksum(buf) ^ salt;
     let mut out = std::io::Cursor::new(buf);
     out.write_u32::<LittleEndian>(csum)?;
diff --git a/src/pack/delta_list.rs b/src/pack/delta_list.rs
index bd14330..882e57d 100644
--- a/src/pack/delta_list.rs
+++ b/src/pack/delta_list.rs
@@ -12,7 +12,7 @@ use Delta::*;
 
 pub fn to_delta(ns: &[u64]) -> Vec<Delta> {
     use std::cmp::Ordering::*;
-    
+
     let mut ds = Vec::with_capacity(ns.len());
 
     if !ns.is_empty() {
@@ -31,10 +31,7 @@ pub fn to_delta(ns: &[u64]) -> Vec<Delta> {
                         count += 1;
                     }
                     count -= 1;
-                    ds.push(Neg {
-                        delta,
-                        count,
-                    });
+                    ds.push(Neg { delta, count });
                     base -= delta * count;
                 }
                 Equal => {
@@ -54,10 +51,7 @@ pub fn to_delta(ns: &[u64]) -> Vec<Delta> {
                         count += 1;
                     }
                     count -= 1;
-                    ds.push(Pos {
-                        delta,
-                        count,
-                    });
+                    ds.push(Pos { delta, count });
                     base += delta * count;
                 }
             }
diff --git a/src/pdata/array.rs b/src/pdata/array.rs
index d8299c2..b9e109d 100644
--- a/src/pdata/array.rs
+++ b/src/pdata/array.rs
@@ -21,12 +21,7 @@ impl Unpack for ArrayBlockEntry {
         let (i, n) = le_u64(i)?;
         let block = n;
 
-        Ok((
-            i,
-            ArrayBlockEntry {
-                block,
-            }
-        ))
+        Ok((i, ArrayBlockEntry { block }))
     }
 }
 
diff --git a/src/pdata/array_block.rs b/src/pdata/array_block.rs
index 0cf7069..50da5dd 100644
--- a/src/pdata/array_block.rs
+++ b/src/pdata/array_block.rs
@@ -33,7 +33,7 @@ impl Unpack for ArrayBlockHeader {
                 max_entries,
                 nr_entries,
                 value_size,
-                blocknr
+                blocknr,
             },
         ))
     }
@@ -54,17 +54,13 @@ fn convert_result<'a, V>(r: IResult<&'a [u8], V>) -> Result<(&'a [u8], V)> {
     r.map_err(|_| anyhow!("parse error"))
 }
 
-pub fn unpack_array_block<V: Unpack>(
-    data: &[u8],
-) -> Result<ArrayBlock<V>> {
+pub fn unpack_array_block<V: Unpack>(data: &[u8]) -> Result<ArrayBlock<V>> {
     // TODO: collect errors
-    let (i, header) = ArrayBlockHeader::unpack(data).map_err(|_e| anyhow!("Couldn't parse header"))?;
+    let (i, header) =
+        ArrayBlockHeader::unpack(data).map_err(|_e| anyhow!("Couldn't parse header"))?;
     let (_i, values) = convert_result(count(V::unpack, header.nr_entries as usize)(i))?;
 
-    Ok(ArrayBlock {
-        header,
-        values,
-    })
+    Ok(ArrayBlock { header, values })
 }
 
 //------------------------------------------
diff --git a/src/pdata/array_walker.rs b/src/pdata/array_walker.rs
index e8287b1..6aabc82 100644
--- a/src/pdata/array_walker.rs
+++ b/src/pdata/array_walker.rs
@@ -11,16 +11,12 @@ use crate::pdata::unpack::*;
 
 pub struct ArrayWalker {
     engine: Arc<dyn IoEngine + Send + Sync>,
-    ignore_non_fatal: bool
+    ignore_non_fatal: bool,
 }
 
 // FIXME: define another Result type for array visiting?
 pub trait ArrayBlockVisitor<V: Unpack> {
-    fn visit(
-        &self,
-        index: u64,
-        v: V,
-    ) -> anyhow::Result<()>;
+    fn visit(&self, index: u64, v: V) -> anyhow::Result<()>;
 }
 
 struct BlockValueVisitor<V> {
@@ -39,14 +35,12 @@ impl<V: Unpack + Copy> BlockValueVisitor<V> {
         }
     }
 
-    pub fn visit_array_block(
-        &self,
-        index: u64,
-        array_block: ArrayBlock<V>,
-    ) {
+    pub fn visit_array_block(&self, index: u64, array_block: ArrayBlock<V>) {
         let begin = index * u64::from(array_block.header.nr_entries);
         for i in 0..array_block.header.nr_entries {
-            self.array_block_visitor.visit(begin + u64::from(i), array_block.values[i as usize]).unwrap();
+            self.array_block_visitor
+                .visit(begin + u64::from(i), array_block.values[i as usize])
+                .unwrap();
         }
     }
 }
@@ -63,7 +57,10 @@ impl<V: Unpack + Copy> NodeVisitor<ArrayBlockEntry> for BlockValueVisitor<V> {
     ) -> Result<()> {
         for n in 0..keys.len() {
             let index = keys[n];
-            let b = self.engine.read(values[n].block).map_err(|_| io_err(path))?;
+            let b = self
+                .engine
+                .read(values[n].block)
+                .map_err(|_| io_err(path))?;
             let array_block = unpack_array_block::<V>(b.get_data()).map_err(|_| io_err(path))?;
             self.visit_array_block(index, array_block);
         }
diff --git a/src/pdata/btree_builder.rs b/src/pdata/btree_builder.rs
index d11e9f4..93242bc 100644
--- a/src/pdata/btree_builder.rs
+++ b/src/pdata/btree_builder.rs
@@ -24,9 +24,15 @@ pub trait RefCounter<Value> {
 pub struct NoopRC {}
 
 impl<Value> RefCounter<Value> for NoopRC {
-    fn get(&self, _v: &Value) -> Result<u32> {Ok(0)}
-    fn inc(&mut self, _v: &Value) -> Result<()> {Ok(())}
-    fn dec(&mut self, _v: &Value) -> Result<()> {Ok(())}
+    fn get(&self, _v: &Value) -> Result<u32> {
+        Ok(0)
+    }
+    fn inc(&mut self, _v: &Value) -> Result<()> {
+        Ok(())
+    }
+    fn dec(&mut self, _v: &Value) -> Result<()> {
+        Ok(())
+    }
 }
 
 /// Wraps a space map up to become a RefCounter.
@@ -150,11 +156,7 @@ fn write_node_<V: Unpack + Pack>(w: &mut WriteBatcher, mut node: Node<V>) -> Res
 /// decide if it produces internal or leaf nodes.
 pub trait NodeIO<V: Unpack + Pack> {
     fn write(&self, w: &mut WriteBatcher, keys: Vec<u64>, values: Vec<V>) -> Result<WriteResult>;
-    fn read(
-        &self,
-        w: &mut WriteBatcher,
-        block: u64,
-    ) -> Result<(Vec<u64>, Vec<V>)>;
+    fn read(&self, w: &mut WriteBatcher, block: u64) -> Result<(Vec<u64>, Vec<V>)>;
 }
 
 pub struct LeafIO {}
@@ -178,11 +180,7 @@ impl<V: Unpack + Pack> NodeIO<V> for LeafIO {
         write_node_(w, node)
     }
 
-    fn read(
-        &self,
-        w: &mut WriteBatcher,
-        block: u64,
-    ) -> Result<(Vec<u64>, Vec<V>)> {
+    fn read(&self, w: &mut WriteBatcher, block: u64) -> Result<(Vec<u64>, Vec<V>)> {
         let b = w.read(block)?;
         let path = Vec::new();
         match unpack_node::<V>(&path, b.get_data(), true, true)? {
@@ -215,11 +213,7 @@ impl NodeIO<u64> for InternalIO {
         write_node_(w, node)
     }
 
-    fn read(
-        &self,
-        w: &mut WriteBatcher,
-        block: u64,
-    ) -> Result<(Vec<u64>, Vec<u64>)> {
+    fn read(&self, w: &mut WriteBatcher, block: u64) -> Result<(Vec<u64>, Vec<u64>)> {
         let b = w.read(block)?;
         let path = Vec::new();
         match unpack_node::<u64>(&path, b.get_data(), true, true)? {
@@ -261,10 +255,7 @@ pub struct NodeSummary {
 
 impl<'a, V: Pack + Unpack + Clone> NodeBuilder<V> {
     /// Create a new NodeBuilder
-    pub fn new(
-        nio: Box<dyn NodeIO<V>>,
-        value_rc: Box<dyn RefCounter<V>>,
-    ) -> Self {
+    pub fn new(nio: Box<dyn NodeIO<V>>, value_rc: Box<dyn RefCounter<V>>) -> Self {
         NodeBuilder {
             nio,
             value_rc,
@@ -356,7 +347,7 @@ impl<'a, V: Pack + Unpack + Clone> NodeBuilder<V> {
         if self.nodes.len() == 0 {
             self.emit_empty_leaf(w)?
         }
-        
+
         Ok(self.nodes)
     }
 
@@ -460,14 +451,9 @@ pub struct Builder<V: Unpack + Pack> {
 }
 
 impl<V: Unpack + Pack + Clone> Builder<V> {
-    pub fn new(
-        value_rc: Box<dyn RefCounter<V>>,
-    ) -> Builder<V> {
+    pub fn new(value_rc: Box<dyn RefCounter<V>>) -> Builder<V> {
         Builder {
-            leaf_builder: NodeBuilder::new(
-                Box::new(LeafIO {}),
-                value_rc,
-            ),
+            leaf_builder: NodeBuilder::new(Box::new(LeafIO {}), value_rc),
         }
     }
 
@@ -487,9 +473,7 @@ impl<V: Unpack + Pack + Clone> Builder<V> {
         while nodes.len() > 1 {
             let mut builder = NodeBuilder::new(
                 Box::new(InternalIO {}),
-                Box::new(SMRefCounter {
-                    sm: w.sm.clone(),
-                }),
+                Box::new(SMRefCounter { sm: w.sm.clone() }),
             );
 
             for n in nodes {
@@ -505,4 +489,3 @@ impl<V: Unpack + Pack + Clone> Builder<V> {
 }
 
 //------------------------------------------
-
diff --git a/src/pdata/mod.rs b/src/pdata/mod.rs
index 70d5d39..d277f7d 100644
--- a/src/pdata/mod.rs
+++ b/src/pdata/mod.rs
@@ -3,10 +3,9 @@ pub mod array_block;
 pub mod array_walker;
 pub mod btree;
 pub mod btree_builder;
-pub mod btree_merge;
 pub mod btree_leaf_walker;
+pub mod btree_merge;
 pub mod btree_walker;
 pub mod space_map;
 pub mod space_map_disk;
 pub mod unpack;
-
diff --git a/src/pdata/space_map_disk.rs b/src/pdata/space_map_disk.rs
index b89de29..da2301e 100644
--- a/src/pdata/space_map_disk.rs
+++ b/src/pdata/space_map_disk.rs
@@ -1,8 +1,8 @@
 use anyhow::{anyhow, Result};
 use byteorder::{LittleEndian, WriteBytesExt};
 use nom::{number::complete::*, IResult};
-use std::io::Cursor;
 use std::collections::BTreeMap;
+use std::io::Cursor;
 
 use crate::checksum;
 use crate::io_engine::*;
@@ -299,7 +299,7 @@ pub fn write_common(w: &mut WriteBatcher, sm: &dyn SpaceMap) -> Result<(Vec<Inde
 
 pub fn write_disk_sm(w: &mut WriteBatcher, sm: &dyn SpaceMap) -> Result<SMRoot> {
     let (index_entries, ref_count_root) = write_common(w, sm)?;
-  
+
     let mut index_builder: Builder<IndexEntry> = Builder::new(Box::new(NoopRC {}));
     for (i, ie) in index_entries.iter().enumerate() {
         index_builder.push_value(w, i as u64, *ie)?;
@@ -340,7 +340,7 @@ fn adjust_counts(w: &mut WriteBatcher, ie: &IndexEntry, allocs: &[u64]) -> Resul
         if bitmap.entries[*a as usize] == Small(0) {
             nr_free -= 1;
         }
-        
+
         bitmap.entries[*a as usize] = Small(1);
     }
 
@@ -350,7 +350,7 @@ fn adjust_counts(w: &mut WriteBatcher, ie: &IndexEntry, allocs: &[u64]) -> Resul
     w.write(bitmap_block, checksum::BT::BITMAP)?;
 
     // Return the adjusted index entry
-    Ok  (IndexEntry {
+    Ok(IndexEntry {
         blocknr: ie.blocknr,
         nr_free,
         none_free_before: first_free,
@@ -381,7 +381,7 @@ pub fn write_metadata_sm(w: &mut WriteBatcher, sm: &dyn SpaceMap) -> Result<SMRo
     // Write out the metadata index
     let metadata_index = MetadataIndex {
         blocknr: bitmap_root.loc,
-        indexes
+        indexes,
     };
     let mut cur = Cursor::new(bitmap_root.get_data());
     metadata_index.pack(&mut cur)?;
diff --git a/src/pdata/unpack.rs b/src/pdata/unpack.rs
index 6596c2b..9cdf164 100644
--- a/src/pdata/unpack.rs
+++ b/src/pdata/unpack.rs
@@ -1,6 +1,6 @@
 use anyhow::{anyhow, Result};
-use nom::{number::complete::*, IResult};
 use byteorder::{LittleEndian, WriteBytesExt};
+use nom::{number::complete::*, IResult};
 
 //------------------------------------------
 
diff --git a/src/report.rs b/src/report.rs
index e105fd5..3ace60f 100644
--- a/src/report.rs
+++ b/src/report.rs
@@ -59,7 +59,7 @@ impl Report {
         let mut inner = self.inner.lock().unwrap();
         inner.set_sub_title(txt)
     }
-    
+
     pub fn progress(&self, percent: u8) {
         let mut inner = self.inner.lock().unwrap();
         inner.progress(percent)
@@ -133,7 +133,7 @@ impl ReportInner for PBInner {
 
 pub fn mk_progress_bar_report() -> Report {
     Report::new(Box::new(PBInner {
-                        title: "".to_string(),
+        title: "".to_string(),
         bar: ProgressBar::new(100),
     }))
 }
diff --git a/src/shrink/copier.rs b/src/shrink/copier.rs
index 1be1f2a..7e29181 100644
--- a/src/shrink/copier.rs
+++ b/src/shrink/copier.rs
@@ -1,7 +1,7 @@
 use anyhow::Result;
 use std::fs::OpenOptions;
+use std::io::{Read, Seek, SeekFrom, Write};
 use std::path::Path;
-use std::io::{Seek, SeekFrom, Write, Read};
 //use std::os::unix::fs::OpenOptionsExt;
 
 pub type Sector = u64;
@@ -13,7 +13,6 @@ pub struct Region {
     pub len: Sector,
 }
 
-
 fn copy_step<W>(file: &mut W, src_byte: u64, dest_byte: u64, len: usize) -> Result<()>
 where
     W: Write + Seek + Read,
@@ -38,7 +37,12 @@ where
     let mut written = 0;
     while written != len_bytes {
         let step = u64::min(len_bytes - written, MAX_BYTES);
-        copy_step(file, src_bytes + written, dest_bytes + written, step as usize)?;
+        copy_step(
+            file,
+            src_bytes + written,
+            dest_bytes + written,
+            step as usize,
+        )?;
         written += step;
     }
     Ok(())
diff --git a/src/thin/dump.rs b/src/thin/dump.rs
index f12a57a..db89b6e 100644
--- a/src/thin/dump.rs
+++ b/src/thin/dump.rs
@@ -298,7 +298,7 @@ fn find_shared_nodes(
         }
     }
 
-/*
+    /*
     // FIXME: why?!!
     // we're not interested in leaves (roots will get re-added later).
     {
@@ -620,7 +620,7 @@ pub fn dump(opts: ThinDumpOptions) -> Result<()> {
     let sb = read_superblock(ctx.engine.as_ref(), SUPERBLOCK_LOCATION)?;
     let md = build_metadata(&ctx, &sb)?;
 
-/*
+    /*
     ctx.report
         .set_title("Optimising metadata to improve leaf packing");
     let md = optimise_metadata(md)?;
diff --git a/src/thin/superblock.rs b/src/thin/superblock.rs
index 3b29b5c..db7074c 100644
--- a/src/thin/superblock.rs
+++ b/src/thin/superblock.rs
@@ -4,8 +4,8 @@ use nom::{bytes::complete::*, number::complete::*, IResult};
 use std::fmt;
 use std::io::Cursor;
 
-use crate::io_engine::*;
 use crate::checksum::*;
+use crate::io_engine::*;
 
 //----------------------------------------
 
@@ -116,14 +116,14 @@ fn pack_superblock<W: WriteBytesExt>(sb: &Superblock, w: &mut W) -> Result<()> {
     w.write_u32::<LittleEndian>(sb.time)?;
     w.write_u64::<LittleEndian>(sb.transaction_id)?;
     w.write_u64::<LittleEndian>(sb.metadata_snap)?;
-    w.write_all(&vec![0; SPACE_MAP_ROOT_SIZE])?;   // data sm root
-    w.write_all(&vec![0; SPACE_MAP_ROOT_SIZE])?;   // metadata sm root
+    w.write_all(&vec![0; SPACE_MAP_ROOT_SIZE])?; // data sm root
+    w.write_all(&vec![0; SPACE_MAP_ROOT_SIZE])?; // metadata sm root
     w.write_u64::<LittleEndian>(sb.mapping_root)?;
     w.write_u64::<LittleEndian>(sb.details_root)?;
     w.write_u32::<LittleEndian>(sb.data_block_size)?;
     w.write_u32::<LittleEndian>(BLOCK_SIZE as u32)?;
     w.write_u64::<LittleEndian>(sb.nr_metadata_blocks)?;
-    
+
     Ok(())
 }
 
@@ -138,7 +138,7 @@ pub fn write_superblock(engine: &dyn IoEngine, _loc: u64, sb: &Superblock) -> Re
 
     // calculate the checksum
     write_checksum(b.get_data(), BT::SUPERBLOCK)?;
-    
+
     // write
     engine.write(&b)?;
     Ok(())
diff --git a/src/thin/xml.rs b/src/thin/xml.rs
index a15df16..0cdf7b4 100644
--- a/src/thin/xml.rs
+++ b/src/thin/xml.rs
@@ -262,16 +262,14 @@ fn parse_superblock(e: &BytesStart) -> Result<Superblock> {
 
 fn parse_def(e: &BytesStart, tag: &str) -> Result<String> {
     let mut name: Option<String> = None;
-    
+
     for a in e.attributes() {
         let kv = a.unwrap();
         match kv.key {
             b"name" => {
                 name = Some(string_val(&kv));
-            },
-            _ => {
-                return bad_attr(tag, kv.key)
             }
+            _ => return bad_attr(tag, kv.key),
         }
     }
 
diff --git a/src/write_batcher.rs b/src/write_batcher.rs
index 3256b91..b911be5 100644
--- a/src/write_batcher.rs
+++ b/src/write_batcher.rs
@@ -74,7 +74,9 @@ impl WriteBatcher {
             }
         }
 
-        self.engine.read(blocknr).map_err(|_| anyhow!("read block error"))
+        self.engine
+            .read(blocknr)
+            .map_err(|_| anyhow!("read block error"))
     }
 
     pub fn flush_(&mut self, queue: Vec<Block>) -> Result<()> {
diff --git a/tests/cache_check.rs b/tests/cache_check.rs
index 3fb9668..8d92e5d 100644
--- a/tests/cache_check.rs
+++ b/tests/cache_check.rs
@@ -1,11 +1,11 @@
 use anyhow::Result;
-use thinp::version::TOOLS_VERSION;
 use duct::cmd;
+use thinp::version::TOOLS_VERSION;
 
 mod common;
 
-use common::*;
 use common::test_dir::*;
+use common::*;
 
 //------------------------------------------
 
@@ -88,7 +88,7 @@ fn failing_q() -> Result<()> {
     assert_eq!(output.stderr.len(), 0);
     Ok(())
 }
-    
+
 #[test]
 fn failing_quiet() -> Result<()> {
     let mut td = TestDir::new()?;
diff --git a/tests/common/cache_xml_generator.rs b/tests/common/cache_xml_generator.rs
index d9e558e..f7ebcdb 100644
--- a/tests/common/cache_xml_generator.rs
+++ b/tests/common/cache_xml_generator.rs
@@ -1,4 +1,4 @@
-use anyhow::{Result};
+use anyhow::Result;
 use rand::prelude::*;
 use std::collections::HashSet;
 use std::fs::OpenOptions;
diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index b139090..f9caffd 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -4,14 +4,14 @@ use anyhow::Result;
 use duct::{cmd, Expression};
 use std::fs::OpenOptions;
 use std::io::{Read, Write};
-use std::path::{PathBuf};
+use std::path::PathBuf;
 use std::str::from_utf8;
 use thinp::file_utils;
 use thinp::io_engine::*;
 
-pub mod thin_xml_generator;
 pub mod cache_xml_generator;
 pub mod test_dir;
+pub mod thin_xml_generator;
 
 use crate::common::thin_xml_generator::{write_xml, SingleThinS};
 use test_dir::TestDir;
@@ -273,7 +273,12 @@ pub fn set_needs_check(md: &PathBuf) -> Result<()> {
     Ok(())
 }
 
-pub fn generate_metadata_leaks(md: &PathBuf, nr_blocks: u64, expected: u32, actual: u32) -> Result<()> {
+pub fn generate_metadata_leaks(
+    md: &PathBuf,
+    nr_blocks: u64,
+    expected: u32,
+    actual: u32,
+) -> Result<()> {
     let output = thin_generate_damage!(
         "-o",
         &md,
@@ -318,4 +323,3 @@ where
     assert_eq!(csum, md5(p)?);
     Ok(())
 }
-
diff --git a/tests/thin_delta.rs b/tests/thin_delta.rs
index 2bc840c..458a307 100644
--- a/tests/thin_delta.rs
+++ b/tests/thin_delta.rs
@@ -2,8 +2,8 @@ use anyhow::Result;
 use thinp::version::TOOLS_VERSION;
 
 mod common;
-use common::*;
 use common::test_dir::*;
+use common::*;
 
 //------------------------------------------
 
@@ -68,4 +68,3 @@ fn dev_unspecified() -> Result<()> {
     assert!(stderr.contains("No input device provided"));
     Ok(())
 }
-
diff --git a/tests/thin_dump.rs b/tests/thin_dump.rs
index d2e58a9..90b4298 100644
--- a/tests/thin_dump.rs
+++ b/tests/thin_dump.rs
@@ -1,12 +1,12 @@
 use anyhow::Result;
-use thinp::file_utils;
 use std::fs::OpenOptions;
-use std::io::{Write};
+use std::io::Write;
 use std::str::from_utf8;
+use thinp::file_utils;
 
 mod common;
-use common::*;
 use common::test_dir::*;
+use common::*;
 
 //------------------------------------------
 
@@ -27,7 +27,11 @@ fn dump_restore_cycle() -> Result<()> {
     let output = thin_dump!(&md).run()?;
 
     let xml = td.mk_path("meta.xml");
-    let mut file = OpenOptions::new().read(false).write(true).create(true).open(&xml)?;
+    let mut file = OpenOptions::new()
+        .read(false)
+        .write(true)
+        .create(true)
+        .open(&xml)?;
     file.write_all(&output.stdout[0..])?;
     drop(file);
 
@@ -63,7 +67,7 @@ fn override_something(flag: &str, value: &str, pattern: &str) -> Result<()> {
 
 #[test]
 fn override_transaction_id() -> Result<()> {
-     override_something("--transaction-id", "2345", "transaction=\"2345\"")
+    override_something("--transaction-id", "2345", "transaction=\"2345\"")
 }
 
 #[test]
@@ -80,13 +84,26 @@ fn override_nr_data_blocks() -> Result<()> {
 fn repair_superblock() -> Result<()> {
     let mut td = TestDir::new()?;
     let md = mk_valid_md(&mut td)?;
-    let before = thin_dump!("--transaction-id=5", "--data-block-size=128", "--nr-data-blocks=4096000", &md).run()?;
+    let before = thin_dump!(
+        "--transaction-id=5",
+        "--data-block-size=128",
+        "--nr-data-blocks=4096000",
+        &md
+    )
+    .run()?;
     damage_superblock(&md)?;
 
-    let after = thin_dump!("--repair", "--transaction-id=5", "--data-block-size=128", "--nr-data-blocks=4096000", &md).run()?;
+    let after = thin_dump!(
+        "--repair",
+        "--transaction-id=5",
+        "--data-block-size=128",
+        "--nr-data-blocks=4096000",
+        &md
+    )
+    .run()?;
     assert_eq!(after.stderr.len(), 0);
     assert_eq!(before.stdout, after.stdout);
-    
+
     Ok(())
 }
 
@@ -95,7 +112,12 @@ fn missing_transaction_id() -> Result<()> {
     let mut td = TestDir::new()?;
     let md = mk_valid_md(&mut td)?;
     damage_superblock(&md)?;
-    let stderr = run_fail(thin_dump!("--repair", "--data-block-size=128", "--nr-data-blocks=4096000", &md))?;
+    let stderr = run_fail(thin_dump!(
+        "--repair",
+        "--data-block-size=128",
+        "--nr-data-blocks=4096000",
+        &md
+    ))?;
     assert!(stderr.contains("transaction id"));
     Ok(())
 }
@@ -105,7 +127,12 @@ fn missing_data_block_size() -> Result<()> {
     let mut td = TestDir::new()?;
     let md = mk_valid_md(&mut td)?;
     damage_superblock(&md)?;
-    let stderr = run_fail(thin_dump!("--repair", "--transaction-id=5", "--nr-data-blocks=4096000", &md))?;
+    let stderr = run_fail(thin_dump!(
+        "--repair",
+        "--transaction-id=5",
+        "--nr-data-blocks=4096000",
+        &md
+    ))?;
     assert!(stderr.contains("data block size"));
     Ok(())
 }
@@ -115,7 +142,12 @@ fn missing_nr_data_blocks() -> Result<()> {
     let mut td = TestDir::new()?;
     let md = mk_valid_md(&mut td)?;
     damage_superblock(&md)?;
-    let stderr = run_fail(thin_dump!("--repair", "--transaction-id=5", "--data-block-size=128", &md))?;
+    let stderr = run_fail(thin_dump!(
+        "--repair",
+        "--transaction-id=5",
+        "--data-block-size=128",
+        &md
+    ))?;
     assert!(stderr.contains("nr data blocks"));
     Ok(())
 }
diff --git a/tests/thin_metadata_pack.rs b/tests/thin_metadata_pack.rs
index 4abd045..131cc95 100644
--- a/tests/thin_metadata_pack.rs
+++ b/tests/thin_metadata_pack.rs
@@ -2,8 +2,8 @@ use anyhow::Result;
 use thinp::version::TOOLS_VERSION;
 
 mod common;
-use common::*;
 use common::test_dir::*;
+use common::*;
 
 //------------------------------------------
 
diff --git a/tests/thin_metadata_unpack.rs b/tests/thin_metadata_unpack.rs
index 26ddfce..33d3f0c 100644
--- a/tests/thin_metadata_unpack.rs
+++ b/tests/thin_metadata_unpack.rs
@@ -2,8 +2,8 @@ use anyhow::Result;
 use thinp::version::TOOLS_VERSION;
 
 mod common;
-use common::*;
 use common::test_dir::*;
+use common::*;
 
 //------------------------------------------
 
diff --git a/tests/thin_repair.rs b/tests/thin_repair.rs
index 98ded1f..19f7969 100644
--- a/tests/thin_repair.rs
+++ b/tests/thin_repair.rs
@@ -3,8 +3,8 @@ use std::str::from_utf8;
 use thinp::version::TOOLS_VERSION;
 
 mod common;
-use common::*;
 use common::test_dir::*;
+use common::*;
 
 //------------------------------------------
 
@@ -132,8 +132,7 @@ fn superblock_succeeds() -> Result<()> {
     Ok(())
 }
 
-fn missing_thing(flag1: &str, flag2: &str, pattern: &str) -> Result<()>
-{
+fn missing_thing(flag1: &str, flag2: &str, pattern: &str) -> Result<()> {
     let mut td = TestDir::new()?;
     let md1 = mk_valid_md(&mut td)?;
     damage_superblock(&md1)?;
@@ -145,15 +144,27 @@ fn missing_thing(flag1: &str, flag2: &str, pattern: &str) -> Result<()>
 
 #[test]
 fn missing_transaction_id() -> Result<()> {
-    missing_thing("--data-block-size=128", "--nr-data-blocks=4096000", "transaction id")
+    missing_thing(
+        "--data-block-size=128",
+        "--nr-data-blocks=4096000",
+        "transaction id",
+    )
 }
 
 #[test]
 fn missing_data_block_size() -> Result<()> {
-    missing_thing("--transaction-id=5", "--nr-data-blocks=4096000", "data block size")
+    missing_thing(
+        "--transaction-id=5",
+        "--nr-data-blocks=4096000",
+        "data block size",
+    )
 }
 
 #[test]
 fn missing_nr_data_blocks() -> Result<()> {
-    missing_thing("--transaction-id=5", "--data-block-size=128", "nr data blocks")
+    missing_thing(
+        "--transaction-id=5",
+        "--data-block-size=128",
+        "nr data blocks",
+    )
 }
diff --git a/tests/thin_restore.rs b/tests/thin_restore.rs
index 62f78dd..c8efa45 100644
--- a/tests/thin_restore.rs
+++ b/tests/thin_restore.rs
@@ -4,8 +4,8 @@ use thinp::file_utils;
 use thinp::version::TOOLS_VERSION;
 
 mod common;
-use common::*;
 use common::test_dir::*;
+use common::*;
 
 //------------------------------------------
 
diff --git a/tests/thin_rmap.rs b/tests/thin_rmap.rs
index 1a932a2..3797edf 100644
--- a/tests/thin_rmap.rs
+++ b/tests/thin_rmap.rs
@@ -2,8 +2,8 @@ use anyhow::Result;
 use thinp::version::TOOLS_VERSION;
 
 mod common;
-use common::*;
 use common::test_dir::*;
+use common::*;
 
 //------------------------------------------
 
@@ -54,7 +54,16 @@ fn valid_region_format_should_pass() -> Result<()> {
 
 #[test]
 fn invalid_regions_should_fail() -> Result<()> {
-    let invalid_regions = ["23,7890", "23..six", "found..7890", "89..88", "89..89", "89..", "", "89...99"];
+    let invalid_regions = [
+        "23,7890",
+        "23..six",
+        "found..7890",
+        "89..88",
+        "89..89",
+        "89..",
+        "",
+        "89...99",
+    ];
     for r in &invalid_regions {
         let mut td = TestDir::new()?;
         let md = mk_valid_md(&mut td)?;
diff --git a/tests/thin_shrink.rs b/tests/thin_shrink.rs
index 6bed874..e796dfd 100644
--- a/tests/thin_shrink.rs
+++ b/tests/thin_shrink.rs
@@ -3,16 +3,14 @@ use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
 use rand::prelude::*;
 use std::fs::OpenOptions;
 use std::io::{Cursor, Read, Seek, SeekFrom, Write};
-use std::path::{Path};
+use std::path::Path;
 
 use thinp::file_utils;
 use thinp::thin::xml::{self, Visit};
 
 mod common;
 use common::test_dir::*;
-use common::thin_xml_generator::{
-    write_xml, EmptyPoolS, FragmentedS, SingleThinS, SnapS, XmlGen
-};
+use common::thin_xml_generator::{write_xml, EmptyPoolS, FragmentedS, SingleThinS, SnapS, XmlGen};
 
 //------------------------------------