Add comments in ch6

easy-fs/src/block_cache.rs

@@ -3,11 +3,15 @@ use alloc::collections::VecDeque;
 use alloc::sync::Arc;
 use lazy_static::*;
 use spin::Mutex;
-
+/// Cached block inside memory
 pub struct BlockCache {
+    /// cached block data
     cache: [u8; BLOCK_SZ],
+    /// underlying block id
     block_id: usize,
+    /// underlying block device
     block_device: Arc<dyn BlockDevice>,
+    /// whether the block is dirty
     modified: bool,
 }
 
@@ -23,7 +27,7 @@ impl BlockCache {
             modified: false,
         }
     }
-
+    /// Get the address of an offset inside the cached block data
     fn addr_of_offset(&self, offset: usize) -> usize {
         &self.cache[offset] as *const _ as usize
     }
@@ -70,7 +74,7 @@ impl Drop for BlockCache {
         self.sync()
     }
 }
-
+/// Use a block cache of 16 blocks
 const BLOCK_CACHE_SIZE: usize = 16;
 
 pub struct BlockCacheManager {
@@ -118,10 +122,11 @@ impl BlockCacheManager {
 }
 
 lazy_static! {
+    /// The global block cache manager
     pub static ref BLOCK_CACHE_MANAGER: Mutex<BlockCacheManager> =
         Mutex::new(BlockCacheManager::new());
 }
-
+/// Get the block cache corresponding to the given block id and block device
 pub fn get_block_cache(
     block_id: usize,
     block_device: Arc<dyn BlockDevice>,
@@ -130,7 +135,7 @@ pub fn get_block_cache(
         .lock()
         .get_block_cache(block_id, block_device)
 }
-
+/// Sync all block cache to block device
 pub fn block_cache_sync_all() {
     let manager = BLOCK_CACHE_MANAGER.lock();
     for (_, cache) in manager.queue.iter() {