1 files changed, 142 insertions, 0 deletions
diff --git a/vm/vm_object.c b/vm/vm_object.c
new file mode 100644
index 00000000..874b26f5
--- /dev/null
+++ b/vm/vm_object.c
@@ -0,0 +1,142 @@
+/*
+ * Copyright (c) 2017 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * This implementation is based on the paper "A lockless pagecache in Linux"
+ * by Nick Piggin. It allows looking up pages without contention on VM objects.
+ */
+
+#include <assert.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <kern/init.h>
+#include <kern/llsync.h>
+#include <kern/mutex.h>
+#include <kern/rdxtree.h>
+#include <vm/vm_object.h>
+#include <vm/vm_page.h>
+#include <machine/page.h>
+
+void __init
+vm_object_setup(void)
+{
+}
+
+void __init
+vm_object_init(struct vm_object *object, uint64_t size)
+{
+    assert(vm_page_aligned(size));
+
+    mutex_init(&object->lock);
+    rdxtree_init(&object->pages, 0);
+    object->size = size;
+    object->nr_pages = 0;
+}
+
+int
+vm_object_insert(struct vm_object *object, struct vm_page *page,
+                 uint64_t offset)
+{
+    int error;
+
+    assert(vm_page_aligned(offset));
+
+    /*
+     * The page may have no references. Add one before publishing
+     * so that concurrent lookups succeed.
+     */
+    vm_page_ref(page);
+
+    mutex_lock(&object->lock);
+
+    if (offset >= object->size) {
+        error = ERROR_INVAL;
+        goto error;
+    }
+
+    error = rdxtree_insert(&object->pages, vm_page_atop(offset), page);
+
+    if (error) {
+        goto error;
+    }
+
+    vm_page_link(page, object, offset);
+    object->nr_pages++;
+    assert(object->nr_pages != 0);
+
+    mutex_unlock(&object->lock);
+
+    return 0;
+
+error:
+    mutex_unlock(&object->lock);
+
+    vm_page_unref(page);
+
+    return error;
+}
+
+void
+vm_object_remove(struct vm_object *object, uint64_t start, uint64_t end)
+{
+    struct vm_page *page;
+    uint64_t offset;
+
+    assert(vm_page_aligned(start));
+    assert(vm_page_aligned(end));
+    assert(start <= end);
+
+    mutex_lock(&object->lock);
+
+    for (offset = start; offset < end; offset += PAGE_SIZE) {
+        page = rdxtree_remove(&object->pages, vm_page_atop(offset));
+
+        if (page == NULL) {
+            continue;
+        }
+
+        vm_page_unlink(page);
+        vm_page_unref(page);
+        assert(object->nr_pages != 0);
+        object->nr_pages--;
+    }
+
+    mutex_unlock(&object->lock);
+}
+
+struct vm_page *
+vm_object_lookup(struct vm_object *object, uint64_t offset)
+{
+    struct vm_page *page;
+    int error;
+
+    llsync_read_enter();
+
+    do {
+        page = rdxtree_lookup(&object->pages, vm_page_atop(offset));
+
+        if (page == NULL) {
+            break;
+        }
+
+        error = vm_page_tryref(page);
+    } while (error);
+
+    llsync_read_exit();
+
+    return page;
+}