[GFS2] Fail over to readpage for stuffed files

 *    the page lock and the glock) and return having done no I/O. Its

 *    obviously not something we'd want to do on too regular a basis.

 *    Any I/O we ignore at this time will be done via readpage later.

 * 2. We have to handle stuffed files here too.

 * 2. We don't handle stuffed files here we let readpage do the honours.

 * 3. mpage_readpages() does most of the heavy lifting in the common case.

 * 4. gfs2_get_block() is relied upon to set BH_Boundary in the right places.

 * 5. We use LM_FLAG_TRY_1CB here, effectively we then have lock-ahead as

	struct gfs2_inode *ip = GFS2_I(inode);

	struct gfs2_sbd *sdp = GFS2_SB(inode);

	struct gfs2_holder gh;

	unsigned page_idx;

	int ret;

	int ret = 0;

	int do_unlock = 0;

	if (likely(file != &gfs2_internal_file_sentinel)) {

			goto out_unlock;

	}

skip_lock:

	if (gfs2_is_stuffed(ip)) {

		struct pagevec lru_pvec;

		pagevec_init(&lru_pvec, 0);

		for (page_idx = 0; page_idx < nr_pages; page_idx++) {

			struct page *page = list_entry(pages->prev, struct page, lru);

			prefetchw(&page->flags);

			list_del(&page->lru);

			if (!add_to_page_cache(page, mapping,

					       page->index, GFP_KERNEL)) {

				ret = stuffed_readpage(ip, page);

				unlock_page(page);

				if (!pagevec_add(&lru_pvec, page))

					 __pagevec_lru_add(&lru_pvec);

			} else {

				page_cache_release(page);

			}

		}

		pagevec_lru_add(&lru_pvec);

		ret = 0;

	} else {

		/* What we really want to do .... */

	if (!gfs2_is_stuffed(ip))

		ret = mpage_readpages(mapping, pages, nr_pages, gfs2_get_block);

	}

	if (do_unlock) {

		gfs2_glock_dq_m(1, &gh);