On Wed, May 25, 2011 at 5:07 AM, Ted Ts'o [off-list ref] wrote:

On Mon, May 23, 2011 at 05:30:57PM +0800, Yongqiang Yang wrote:

quoted

@@ -982,20 +997,13 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,

                      err = -EIO;
                      goto cleanup;
              }
-             while (path[i].p_idx <= EXT_MAX_INDEX(path[i].p_hdr)) {
-                     ext_debug("%d: move %d:%llu in new index %llu\n", i,
-                                     le32_to_cpu(path[i].p_idx->ei_block),
-                                     ext4_idx_pblock(path[i].p_idx),
-                                     newblock);
-                     /*memmove(++fidx, path[i].p_idx++,
-                                     sizeof(struct ext4_extent_idx));
-                     neh->eh_entries++;
-                     BUG_ON(neh->eh_entries > neh->eh_max);*/
-                     path[i].p_idx++;
-                     m++;
-             }
+             /* start copy indexes */
+             m = EXT_MAX_INDEX(path[i].p_hdr) - path[i].p_idx++;
+             ext_debug("cur 0x%p, last 0x%p\n", path[i].p_idx,
+                             EXT_MAX_INDEX(path[i].p_hdr));
+             ext4_ext_show_move(inode, path, newblock, i);
              if (m) {
-                     memmove(++fidx, path[i].p_idx - m,
+                     memmove(++fidx, path[i].p_idx,
                              sizeof(struct ext4_extent_idx) * m);
                      le16_add_cpu(&neh->eh_entries, m);
              }

Hi Ted,

Thank you for your review.  I had looked at this case.

So the old code mutates path[i].p_idx, where as your new code doesn't.

path[i]p_idx is mutated to EXT_MAX_INDEX(path[i].p_hdr) + 1, it is
meaningless.  ext4_ext_split() is used only by
ext4_ext_create_new_leaf() which drops the path after ext4_ext_split()
returns, so the path[i].p_idx is no longer used.

The one thing that scares me is that ext4_ext_insert_index() is passed
&path[at], the function preferences path[at].p_idx.

ext4_ext_split() insert k indexes, where k = depth - at -1, starting
from depth - 1 to depth - 1 - k + 1 = depth - k = at + 1.

So old code does not mutate depth[at].p_idx.

I had tested the patch with fsx.  I am not sure if this test is
enough.  If you want more tests, I can do it.

Thanks,
Yongqiang.

Have you looked at this case?

                                       - Ted

-- 
Best Wishes
Yongqiang Yang
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