xfs: fix the multi-segment log buffer format

Per Dave Chinner suggestion, this patch:
 1) Corrects the detection of whether a multi-segment buffer is
    still tracking data.
 2) Clears all the buffer log formats for a multi-segment buffer.

Signed-off-by: Mark Tinguely <tinguely@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
index f7510bf..3edf5db 100644
--- a/fs/xfs/xfs_trans_buf.c
+++ b/fs/xfs/xfs_trans_buf.c
@@ -643,6 +643,7 @@
 	xfs_buf_t	*bp)
 {
 	xfs_buf_log_item_t	*bip = bp->b_fspriv;
+	int			i;
 
 	ASSERT(bp->b_transp == tp);
 	ASSERT(bip != NULL);
@@ -670,8 +671,10 @@
 	bip->bli_flags &= ~(XFS_BLI_INODE_BUF | XFS_BLI_LOGGED | XFS_BLI_DIRTY);
 	bip->__bli_format.blf_flags &= ~XFS_BLF_INODE_BUF;
 	bip->__bli_format.blf_flags |= XFS_BLF_CANCEL;
-	memset((char *)(bip->__bli_format.blf_data_map), 0,
-	      (bip->__bli_format.blf_map_size * sizeof(uint)));
+	for (i = 0; i < bip->bli_format_count; i++) {
+		memset(bip->bli_formats[i].blf_data_map, 0,
+		       (bip->bli_formats[i].blf_map_size * sizeof(uint)));
+	}
 	bip->bli_item.li_desc->lid_flags |= XFS_LID_DIRTY;
 	tp->t_flags |= XFS_TRANS_DIRTY;
 }