Small pageserver cleanups (#4657)

## Problem

I was reading the code of the page server today and found these minor
things that I thought could be cleaned up.

## Summary of changes

* remove a redundant indentation layer and continue in the flushing loop
* use the builtin `PartialEq` check instead of hand-rolling a `range_eq`
function
* Add a missing `>` to a prominent doc comment

pageserver/src/tenant/layer_map.rs

@@ -60,7 +60,6 @@ use utils::lsn::Lsn;
 use historic_layer_coverage::BufferedHistoricLayerCoverage;
 pub use historic_layer_coverage::LayerKey;
 
-use super::storage_layer::range_eq;
 use super::storage_layer::PersistentLayerDesc;
 
 ///
@@ -365,7 +364,7 @@ impl LayerMap {
     }
 
     pub fn is_l0(layer: &PersistentLayerDesc) -> bool {
-        range_eq(&layer.get_key_range(), &(Key::MIN..Key::MAX))
+        layer.get_key_range() == (Key::MIN..Key::MAX)
     }
 
     /// This function determines which layers are counted in `count_deltas`:
@@ -397,7 +396,7 @@ impl LayerMap {
         }
 
         // Case 2
-        if range_eq(partition_range, &(Key::MIN..Key::MAX)) {
+        if partition_range == &(Key::MIN..Key::MAX) {
             return true;
         }
 

pageserver/src/tenant/storage_layer.rs

@@ -54,13 +54,6 @@ where
     }
 }
 
-pub fn range_eq<T>(a: &Range<T>, b: &Range<T>) -> bool
-where
-    T: PartialEq<T>,
-{
-    a.start == b.start && a.end == b.end
-}
-
 /// Struct used to communicate across calls to 'get_value_reconstruct_data'.
 ///
 /// Before first call, you can fill in 'page_img' if you have an older cached

pageserver/src/tenant/storage_layer/delta_layer.rs

@@ -10,7 +10,7 @@
 //! The delta files are stored in timelines/<timeline_id> directory.  Currently,
 //! there are no subdirectories, and each delta file is named like this:
 //!
-//!    <key start>-<key end>__<start LSN>-<end LSN
+//!    <key start>-<key end>__<start LSN>-<end LSN>
 //!
 //! For example:
 //!

pageserver/src/tenant/timeline.rs

@@ -2808,14 +2808,10 @@ impl Timeline {
                     layers.frozen_layers.front().cloned()
                     // drop 'layers' lock to allow concurrent reads and writes
                 };
-                if let Some(layer_to_flush) = layer_to_flush {
-                    if let Err(err) = self.flush_frozen_layer(layer_to_flush, ctx).await {
-                        error!("could not flush frozen layer: {err:?}");
-                        break Err(err);
-                    }
-                    continue;
-                } else {
-                    break Ok(());
+                let Some(layer_to_flush) = layer_to_flush else { break Ok(()) };
+                if let Err(err) = self.flush_frozen_layer(layer_to_flush, ctx).await {
+                    error!("could not flush frozen layer: {err:?}");
+                    break Err(err);
                 }
             };
             // Notify any listeners that we're done

pageserver/src/walredo.rs

@@ -175,8 +175,8 @@ impl WalRedoManager for PostgresRedoManager {
         let mut img = base_img.map(|p| p.1);
         let mut batch_neon = can_apply_in_neon(&records[0].1);
         let mut batch_start = 0;
-        for i in 1..records.len() {
-            let rec_neon = can_apply_in_neon(&records[i].1);
+        for (i, record) in records.iter().enumerate().skip(1) {
+            let rec_neon = can_apply_in_neon(&record.1);
 
             if rec_neon != batch_neon {
                 let result = if batch_neon {