dax: use sb_issue_zerout instead of calling dax_clear_sectors

dax_clear_sectors() cannot handle poisoned blocks.  These must be
zeroed using the BIO interface instead.  Convert ext2 and XFS to use
only sb_issue_zerout().

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
[vishal: Also remove the dax_clear_sectors function entirely]
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

fs/xfs/xfs_bmap_util.c

@@ -72,18 +72,11 @@ xfs_zero_extent(
 	struct xfs_mount *mp = ip->i_mount;
 	xfs_daddr_t	sector = xfs_fsb_to_db(ip, start_fsb);
 	sector_t	block = XFS_BB_TO_FSBT(mp, sector);
-	ssize_t		size = XFS_FSB_TO_B(mp, count_fsb);
-
-	if (IS_DAX(VFS_I(ip)))
-		return dax_clear_sectors(xfs_find_bdev_for_inode(VFS_I(ip)),
-				sector, size);
-
-	/*
-	 * let the block layer decide on the fastest method of
-	 * implementing the zeroing.
-	 */
-	return sb_issue_zeroout(mp->m_super, block, count_fsb, GFP_NOFS);
 
+	return blkdev_issue_zeroout(xfs_find_bdev_for_inode(VFS_I(ip)),
+		block << (mp->m_super->s_blocksize_bits - 9),
+		count_fsb << (mp->m_super->s_blocksize_bits - 9),
+		GFP_NOFS, true);
 }
 
 /*