Function dfs_page_lookup

components/dfs/dfs_v2/src/dfs_pcache.c:1480–1542

* @brief Look up a page in the cache and load it if not found * * This function searches for a page at the specified position in the file's address space. * If the page isn't found, it preloads multiple pages (RT_PAGECACHE_PRELOAD count) next to the requested position. * It also triggers garbage collection when the cache reaches certain thresholds. * * @param[in] file Pointer to the file str

 *         NULL if the page couldn't be found or loaded
 */
static struct dfs_page *dfs_page_lookup(struct dfs_file *file, off_t pos)
{
    struct dfs_page *page = RT_NULL;
    struct dfs_aspace *aspace = file->vnode->aspace;

    dfs_aspace_lock(aspace);
    page = dfs_page_search(aspace, pos);
    if (!page)
    {
        int count = RT_PAGECACHE_PRELOAD;
        struct dfs_page *tmp = RT_NULL;
        off_t fpos = pos / ARCH_PAGE_SIZE * ARCH_PAGE_SIZE;

        do
        {
            page = dfs_aspace_load_page(file, fpos);
            if (page)
            {
                if (tmp == RT_NULL)
                {
                    tmp = page;
                }
                else
                {
                    dfs_page_release(page);
                }
            }
            else
            {
                break;
            }

            fpos += ARCH_PAGE_SIZE;
            page = dfs_page_search(aspace, fpos);
            if (page)
            {
                dfs_page_release(page);
            }
            count --;

        } while (count && page == RT_NULL);

        page = tmp;
        if (page)
        {
            dfs_aspace_unlock(aspace);

            if (rt_atomic_load(&(__pcache.pages_count)) >= RT_PAGECACHE_COUNT)
            {
                dfs_pcache_limit_check();
            }
            else if (rt_atomic_load(&(__pcache.pages_count)) >= RT_PAGECACHE_COUNT * RT_PAGECACHE_GC_WORK_LEVEL / 100)
            {
                dfs_pcache_mq_work(PCACHE_MQ_GC);
            }

            return page;
        }