Add cache to AtaBlockDevice (#396)

* Add cache to AtaBlockDevice * Add methods for cached blocks * Rename cache index to hash * Add ATA_CACHE_SIZE * Refactor code
vinc · Aug 25, 2022 · d965a72 · d965a72
1 parent ec1fff6
commit d965a72
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Showing 2 changed files with 45 additions and 8 deletions.
diff --git a/src/sys/fs/block.rs b/src/sys/fs/block.rs
@@ -42,7 +42,7 @@ impl Block {
 
     pub fn read(addr: u32) -> Self {
         let mut buf = [0; super::BLOCK_SIZE];
-        if let Some(ref block_device) = *super::block_device::BLOCK_DEVICE.lock() {
+        if let Some(ref mut block_device) = *super::block_device::BLOCK_DEVICE.lock() {
             if block_device.read(addr, &mut buf).is_err() {
                 debug!("MFS: could not read block {:#x}", addr);
             }

diff --git a/src/sys/fs/block_device.rs b/src/sys/fs/block_device.rs
@@ -16,14 +16,14 @@ pub enum BlockDevice {
 }
 
 pub trait BlockDeviceIO {
-    fn read(&self, addr: u32, buf: &mut [u8]) -> Result<(), ()>;
+    fn read(&mut self, addr: u32, buf: &mut [u8]) -> Result<(), ()>;
     fn write(&mut self, addr: u32, buf: &[u8]) -> Result<(), ()>;
     fn block_size(&self) -> usize;
     fn block_count(&self) -> usize;
 }
 
 impl BlockDeviceIO for BlockDevice {
-    fn read(&self, addr: u32, buf: &mut [u8]) -> Result<(), ()> {
+    fn read(&mut self, addr: u32, buf: &mut [u8]) -> Result<(), ()> {
         match self {
             BlockDevice::Mem(dev) => dev.read(addr, buf),
             BlockDevice::Ata(dev) => dev.read(addr, buf),
@@ -70,7 +70,7 @@ impl MemBlockDevice {
 }
 
 impl BlockDeviceIO for MemBlockDevice {
-    fn read(&self, block_index: u32, buf: &mut [u8]) -> Result<(), ()> {
+    fn read(&mut self, block_index: u32, buf: &mut [u8]) -> Result<(), ()> {
         // TODO: check for overflow
         buf[..].clone_from_slice(&self.dev[block_index as usize][..]);
         Ok(())
@@ -107,15 +107,19 @@ pub fn format_mem() {
     }
 }
 
+const ATA_CACHE_SIZE: usize = 1024;
+
 #[derive(Clone)]
 pub struct AtaBlockDevice {
+    cache: [Option<(u32, Vec<u8>)>; ATA_CACHE_SIZE],
     dev: sys::ata::Drive
 }
 
 impl AtaBlockDevice {
     pub fn new(bus: u8, dsk: u8) -> Option<Self> {
         sys::ata::Drive::open(bus, dsk).map(|dev| {
-            Self { dev }
+            let cache = [(); ATA_CACHE_SIZE].map(|_| None);
+            Self { dev, cache }
         })
     }
 
@@ -124,15 +128,48 @@ impl AtaBlockDevice {
         self.block_size() * self.block_count()
     }
     */
+
+    fn hash(&self, block_addr: u32) -> usize {
+        (block_addr as usize) % self.cache.len()
+    }
+
+    fn cached_block(&self, block_addr: u32) -> Option<&[u8]> {
+        let h = self.hash(block_addr);
+        if let Some((cached_addr, cached_buf)) = &self.cache[h] {
+            if block_addr == *cached_addr {
+                return Some(cached_buf);
+            }
+        }
+        None
+    }
+
+    fn set_cached_block(&mut self, block_addr: u32, buf: &[u8]) {
+        let h = self.hash(block_addr);
+        self.cache[h] = Some((block_addr, buf.to_vec()));
+    }
+
+    fn unset_cached_block(&mut self, block_addr: u32) {
+        let h = self.hash(block_addr);
+        self.cache[h] = None;
+    }
 }
 
 impl BlockDeviceIO for AtaBlockDevice {
-    fn read(&self, block_addr: u32, buf: &mut [u8]) -> Result<(), ()> {
-        sys::ata::read(self.dev.bus, self.dev.dsk, block_addr, buf)
+    fn read(&mut self, block_addr: u32, buf: &mut [u8]) -> Result<(), ()> {
+        if let Some(cached) = self.cached_block(block_addr) {
+            buf.copy_from_slice(cached);
+            return Ok(());
+        }
+
+        sys::ata::read(self.dev.bus, self.dev.dsk, block_addr, buf)?;
+        self.set_cached_block(block_addr, buf);
+        Ok(())
     }
 
     fn write(&mut self, block_addr: u32, buf: &[u8]) -> Result<(), ()> {
-        sys::ata::write(self.dev.bus, self.dev.dsk, block_addr, buf)
+        sys::ata::write(self.dev.bus, self.dev.dsk, block_addr, buf)?;
+        self.unset_cached_block(block_addr);
+        Ok(())
     }
 
     fn block_size(&self) -> usize {