1 files changed, 20 insertions, 8 deletions

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index edaab05a93e0..f43bc5f18a35 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -1717,17 +1717,29 @@ static int ocfs2_do_truncate(struct ocfs2_super *osb,
 
                         ocfs2_remove_from_cache(inode, eb_bh);
 
-                        BUG_ON(eb->h_suballoc_slot);
                         BUG_ON(el->l_recs[0].e_clusters);
                         BUG_ON(el->l_recs[0].e_cpos);
                         BUG_ON(el->l_recs[0].e_blkno);
-                        status = ocfs2_free_extent_block(handle,
-                                                         tc->tc_ext_alloc_inode,
-                                                         tc->tc_ext_alloc_bh,
-                                                         eb);
-                        if (status < 0) {
-                                mlog_errno(status);
-                                goto bail;
+                        if (eb->h_suballoc_slot == 0) {
+                                /*
+                                 * This code only understands how to
+                                 * lock the suballocator in slot 0,
+                                 * which is fine because allocation is
+                                 * only ever done out of that
+                                 * suballocator too. A future version
+                                 * might change that however, so avoid
+                                 * a free if we don't know how to
+                                 * handle it. This way an fs incompat
+                                 * bit will not be necessary.
+                                 */
+                                status = ocfs2_free_extent_block(handle,
+                                                                 tc->tc_ext_alloc_inode,
+                                                                 tc->tc_ext_alloc_bh,
+                                                                 eb);
+                                if (status < 0) {
+                                        mlog_errno(status);
+                                        goto bail;
+                                }
                         }
                 }
                 brelse(eb_bh);