From 302a58e8ea80a6aa63396e39650d71bc99e15057 Mon Sep 17 00:00:00 2001
From: Joonas Koivunen <joonas@neon.tech>
Date: Tue, 29 Aug 2023 11:55:08 +0300
Subject: [PATCH] image/deltalayer: shuffle comments around

---
 pageserver/src/tenant/storage_layer/delta_layer.rs | 14 ++++----------
 pageserver/src/tenant/storage_layer/image_layer.rs | 14 ++++----------
 2 files changed, 8 insertions(+), 20 deletions(-)

diff --git a/pageserver/src/tenant/storage_layer/delta_layer.rs b/pageserver/src/tenant/storage_layer/delta_layer.rs
index 7f195b7d59..4e53e91a05 100644
--- a/pageserver/src/tenant/storage_layer/delta_layer.rs
+++ b/pageserver/src/tenant/storage_layer/delta_layer.rs
@@ -179,20 +179,12 @@ impl DeltaKey {
     }
 }
 
-/// DeltaLayer is the in-memory data structure associated with an on-disk delta
-/// file.
-///
-/// We keep a DeltaLayer in memory for each file, in the LayerMap. If a layer
-/// is in "loaded" state, we have a copy of the index in memory, in 'inner'.
-/// Otherwise the struct is just a placeholder for a file that exists on disk,
-/// and it needs to be loaded before using it in queries.
+/// This is used only from `pagectl`. Within pageserver, all layers are
+/// [`crate::tenant::storage_layer::Layer`], which can hold a [`DeltaLayerInner`].
 pub struct DeltaLayer {
     path: PathBuf,
-
     pub desc: PersistentLayerDesc,
-
     access_stats: LayerAccessStats,
-
     inner: OnceCell<Arc<DeltaLayerInner>>,
 }
 
@@ -209,6 +201,8 @@ impl std::fmt::Debug for DeltaLayer {
     }
 }
 
+/// `DeltaLayerInner` is the in-memory data structure associated with an on-disk delta
+/// file.
 pub struct DeltaLayerInner {
     // values copied from summary
     index_start_blk: u32,
diff --git a/pageserver/src/tenant/storage_layer/image_layer.rs b/pageserver/src/tenant/storage_layer/image_layer.rs
index 54261c95a3..6445d96987 100644
--- a/pageserver/src/tenant/storage_layer/image_layer.rs
+++ b/pageserver/src/tenant/storage_layer/image_layer.rs
@@ -117,22 +117,14 @@ impl Summary {
     }
 }
 
-/// ImageLayer is the in-memory data structure associated with an on-disk image
-/// file.
-///
-/// We keep an ImageLayer in memory for each file, in the LayerMap. If a layer
-/// is in "loaded" state, we have a copy of the index in memory, in 'inner'.
-/// Otherwise the struct is just a placeholder for a file that exists on disk,
-/// and it needs to be loaded before using it in queries.
+/// This is used only from `pagectl`. Within pageserver, all layers are
+/// [`crate::tenant::storage_layer::Layer`], which can hold an [`ImageLayerInner`].
 pub struct ImageLayer {
     path: PathBuf,
-
     pub desc: PersistentLayerDesc,
     // This entry contains an image of all pages as of this LSN, should be the same as desc.lsn
     pub lsn: Lsn,
-
     access_stats: LayerAccessStats,
-
     inner: OnceCell<ImageLayerInner>,
 }
 
@@ -149,6 +141,8 @@ impl std::fmt::Debug for ImageLayer {
     }
 }
 
+/// ImageLayer is the in-memory data structure associated with an on-disk image
+/// file.
 pub struct ImageLayerInner {
     // values copied from summary
     index_start_blk: u32,