GFS2: Fix incorrect invalidation for DIO/buffered I/O

{

	struct file *file = iocb->ki_filp;

	struct inode *inode = file->f_mapping->host;

	struct address_space *mapping = inode->i_mapping;

	struct gfs2_inode *ip = GFS2_I(inode);

	struct gfs2_holder gh;

	int rv;

	if (rv != 1)

		goto out; /* dio not valid, fall back to buffered i/o */

	/*

	 * Now since we are holding a deferred (CW) lock at this point, you

	 * might be wondering why this is ever needed. There is a case however

	 * where we've granted a deferred local lock against a cached exclusive

	 * glock. That is ok provided all granted local locks are deferred, but

	 * it also means that it is possible to encounter pages which are

	 * cached and possibly also mapped. So here we check for that and sort

	 * them out ahead of the dio. The glock state machine will take care of

	 * everything else.

	 *

	 * If in fact the cached glock state (gl->gl_state) is deferred (CW) in

	 * the first place, mapping->nr_pages will always be zero.

	 */

	if (mapping->nrpages) {

		loff_t lstart = offset & (PAGE_CACHE_SIZE - 1);

		loff_t len = iov_length(iov, nr_segs);

		loff_t end = PAGE_ALIGN(offset + len) - 1;

		rv = 0;

		if (len == 0)

			goto out;

		if (test_and_clear_bit(GIF_SW_PAGED, &ip->i_flags))

			unmap_shared_mapping_range(ip->i_inode.i_mapping, offset, len);

		rv = filemap_write_and_wait_range(mapping, lstart, end);

		if (rv)

			return rv;

		truncate_inode_pages_range(mapping, lstart, end);

	}

	rv = __blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,

				  offset, nr_segs, gfs2_get_block_direct,

				  NULL, NULL, 0);