GFS2: Optimise writepage for metadata

#include "util.h"

#include "ops_address.h"

static int aspace_get_block(struct inode *inode, sector_t lblock,

			    struct buffer_head *bh_result, int create)

static int gfs2_aspace_writepage(struct page *page, struct writeback_control *wbc)

{

	gfs2_assert_warn(inode->i_sb->s_fs_info, 0);

	return -EOPNOTSUPP;

	int err;

	struct buffer_head *bh, *head;

	int nr_underway = 0;

	int write_op = (1 << BIO_RW_META) | ((wbc->sync_mode == WB_SYNC_ALL ?

			WRITE_SYNC_PLUG : WRITE));

	BUG_ON(!PageLocked(page));

	BUG_ON(!page_has_buffers(page));

	head = page_buffers(page);

	bh = head;

	do {

		if (!buffer_mapped(bh))

			continue;

		/*

		 * If it's a fully non-blocking write attempt and we cannot

		 * lock the buffer then redirty the page.  Note that this can

		 * potentially cause a busy-wait loop from pdflush and kswapd

		 * activity, but those code paths have their own higher-level

		 * throttling.

		 */

		if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {

			lock_buffer(bh);

		} else if (!trylock_buffer(bh)) {

			redirty_page_for_writepage(wbc, page);

			continue;

		}

		if (test_clear_buffer_dirty(bh)) {

			mark_buffer_async_write(bh);

		} else {

			unlock_buffer(bh);

		}

	} while ((bh = bh->b_this_page) != head);

static int gfs2_aspace_writepage(struct page *page,

				 struct writeback_control *wbc)

{

	return block_write_full_page(page, aspace_get_block, wbc);

	/*

	 * The page and its buffers are protected by PageWriteback(), so we can

	 * drop the bh refcounts early.

	 */

	BUG_ON(PageWriteback(page));

	set_page_writeback(page);

	do {

		struct buffer_head *next = bh->b_this_page;

		if (buffer_async_write(bh)) {

			submit_bh(write_op, bh);

			nr_underway++;

		}

		bh = next;

	} while (bh != head);

	unlock_page(page);

	err = 0;

	if (nr_underway == 0)

		end_page_writeback(page);

	return err;

}

static const struct address_space_operations aspace_aops = {