/*
 * Copyright 2007, Axel Dörfler, axeld@pinc-software.de. All rights reserved.
 * Distributed under the terms of the MIT License.
 */


#include "PageCacheLocker.h"

#include <vm/VMCache.h>


bool
PageCacheLocker::_IgnorePage(vm_page* page)
{
        if (page->busy || page->State() == PAGE_STATE_WIRED
                || page->State() == PAGE_STATE_FREE || page->State() == PAGE_STATE_CLEAR
                || page->State() == PAGE_STATE_UNUSED || page->WiredCount() > 0)
                return true;

        return false;
}


bool
PageCacheLocker::Lock(vm_page* page, bool dontWait)
{
        if (_IgnorePage(page))
                return false;

        // Grab a reference to this cache.
        VMCache* cache = vm_cache_acquire_locked_page_cache(page, dontWait);
        if (cache == NULL)
                return false;

        if (_IgnorePage(page)) {
                cache->ReleaseRefAndUnlock();
                return false;
        }

        fPage = page;
        return true;
}


void
PageCacheLocker::Unlock()
{
        if (fPage == NULL)
                return;

        fPage->Cache()->ReleaseRefAndUnlock();

        fPage = NULL;
}