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/*
* 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>
struct vm_object vm_object_kernel_object;
static int __init
vm_object_setup(void)
{
return 0;
}
INIT_OP_DEFINE(vm_object_setup,
INIT_OP_DEP(mutex_setup, true),
INIT_OP_DEP(rdxtree_setup, true),
INIT_OP_DEP(vm_page_setup, true));
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_btop(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_btop(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_btop(offset));
if (page == NULL) {
break;
}
error = vm_page_tryref(page);
} while (error);
llsync_read_exit();
return page;
}
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