From 692f1fb91fb781eafe68ce30cc1ebd56ba8d3f86 Mon Sep 17 00:00:00 2001
From: sbosse <sbosse@uni-bremen.de>
Date: Mon, 14 Oct 2024 23:07:50 +0200
Subject: [PATCH] Mon 14 Oct 23:06:38 CEST 2024

---
 kernel/bcache.c | 224 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 224 insertions(+)
 create mode 100644 kernel/bcache.c

diff --git a/kernel/bcache.c b/kernel/bcache.c
new file mode 100644
index 0000000..acc8d7d
--- /dev/null
+++ b/kernel/bcache.c
@@ -0,0 +1,224 @@
+/*
+Copyright (C) 2015-2019 The University of Notre Dame
+This software is distributed under the GNU General Public License.
+See the file LICENSE for details.
+*/
+
+#include "bcache.h"
+#include "list.h"
+#include "page.h"
+#include "kmalloc.h"
+#include "string.h"
+#include "kernel/error.h"
+
+struct bcache_entry {
+	struct list_node node;
+	struct device *device;
+	int block;
+	int dirty;
+	char *data;
+};
+
+static struct list cache = LIST_INIT;
+static struct bcache_stats stats = {0};
+static int max_cache_size = 100;
+
+struct bcache_entry * bcache_entry_create( struct device *device, int block )
+{
+	struct bcache_entry *e = kmalloc(sizeof(*e));
+	if(!e) return 0;
+
+	e->device = device;
+	e->block = block;
+	e->data = page_alloc(1);
+	if(!e->data) {
+		kfree(e);
+		return 0;
+	}
+
+	return e;
+
+}
+
+void bcache_entry_delete( struct bcache_entry *e )
+{
+	if(e) {
+		if(e->data) page_free(e->data);
+		kfree(e);
+	}
+}
+
+void bcache_entry_clean( struct bcache_entry *e )
+{
+	if(e->dirty) {
+		device_write(e->device,e->data,1,e->block);
+		// XXX How to deal with failure here?
+		e->dirty = 0;
+		stats.writebacks++;
+	}
+
+}
+
+void bcache_trim()
+{
+	struct bcache_entry *e;
+
+	while(list_size(&cache)>max_cache_size) {
+		e = (struct bcache_entry *) list_pop_tail(&cache);
+		bcache_entry_clean(e);
+		bcache_entry_delete(e);
+	}
+}
+
+struct bcache_entry * bcache_find( struct device *device, int block )
+{
+	struct list_node *n;
+	struct bcache_entry *e;
+
+	for(n=cache.head;n;n=n->next) {
+		e = (struct bcache_entry *)n;
+		if(e->device==device && e->block==block) {
+			return e;
+		}
+	}
+
+	return 0;
+}
+
+struct bcache_entry * bcache_find_or_create( struct device *device, int block, int *was_a_hit )
+{
+	struct bcache_entry *e = bcache_find(device,block);
+	if(e) {
+		*was_a_hit = 1;
+	} else {
+		*was_a_hit = 0;
+		e = bcache_entry_create(device,block);
+		if(!e) return 0;
+		list_push_head(&cache,&e->node);
+	}
+
+	bcache_trim();
+
+	return e;
+}
+
+int bcache_read_block( struct device *device, char *data, int block )
+{
+	int hit=0;
+	int result;
+
+	struct bcache_entry *e = bcache_find_or_create(device,block,&hit);
+	if(!e) return KERROR_OUT_OF_MEMORY;
+
+	if(hit) {
+		stats.read_hits++;
+		result = 1;
+	} else {
+		stats.read_misses++;
+		result = device_read(device,e->data,1,block);
+	}
+
+	if(result>0) {
+		memcpy(data,e->data,device_block_size(device));
+	} else {
+		list_remove(&e->node);
+		bcache_entry_delete(e);
+	}
+
+	return result;
+}
+
+int bcache_read( struct device *device, char *data, int blocks, int offset )
+{
+	int i,r;
+	int count = 0;
+	int bs = device_block_size(device);
+
+	for(i=0;i<blocks;i++) {
+		r = bcache_read_block(device,&data[i*bs],offset+i);
+		if(r<1) break;
+		count++;
+	}
+
+	if(count>0) {
+		return count;
+	} else {
+		return r;
+	}
+}
+
+
+int bcache_write_block( struct device *device, const char *data, int block )
+{
+	int hit;
+
+	struct bcache_entry *e = bcache_find_or_create(device,block,&hit);
+	if(!e) return KERROR_OUT_OF_MEMORY;
+
+	if(hit) {
+		stats.write_hits++;
+	} else {
+		stats.write_misses++;
+	}
+
+	memcpy(e->data,data,device_block_size(device));
+	e->dirty = 1;
+
+	return 1;
+}
+
+int bcache_write( struct device *device, const char *data, int blocks, int offset )
+{
+	int i,r;
+	int count = 0;
+	int bs = device_block_size(device);
+
+	for(i=0;i<blocks;i++) {
+		r = bcache_write_block(device,&data[i*bs],offset+i);
+		if(r<1) break;
+		count++;
+	}
+
+	if(count>0) {
+		return count;
+	} else {
+		return r;
+	}
+}
+
+
+void bcache_flush_block( struct device *device, int block )
+{
+	struct bcache_entry *e;
+	e = bcache_find(device,block);
+	if(e) bcache_entry_clean(e);
+}
+
+void bcache_flush_device( struct device *device )
+{
+	struct list_node *n;
+	struct bcache_entry *e;
+
+	for(n=cache.head;n;n=n->next) {
+		e = (struct bcache_entry *) n;
+		if(e->device==device) {
+			bcache_entry_clean(e);
+		}
+	}
+}
+
+void bcache_flush_all()
+{
+	struct list_node *n;
+	struct bcache_entry *e;
+
+	for(n=cache.head;n;n=n->next) {
+		e = (struct bcache_entry *) n;
+		bcache_entry_clean(e);
+	}
+}
+
+void bcache_get_stats( struct bcache_stats *s )
+{
+	memcpy(s,&stats,sizeof(*s));
+}