admin edit pages could loop

[hailin]

This is to continue #11018.

Display_page_row() in wp-admin/includes/template.php could loop forever, causing wp-admin/edit-pages.php not able to load at all.

We should break the loop and fix the pages dynamically when this happens.

westi suggested breaking the loop in _get_post_ancestors.

This patch breaks the loop right in display_page_row, and we've been running this patch on a live site for a week now and verified that it's working correctly.

_get_post_ancestors as we have the same bug there and then we can call that and use count() to get the depth we are at.

When there is a loop, we probably can not use count since it will return infinity.
We need to break out somehow, and return a dummy value such as 9999. Not sure it's going to be pretty.

correct patch

Attached the right patch.

_get_post_ancestors has the following comment:
The post parent will be an ancestor and the parent of the post

• parent will be an ancestor. There will only be two ancestors at the most.

Based on the above comment, _get_post_ancestors doesn't have loop issue, and it appears that it was designed to have only two ancestors.

Therefore, the correct way to break pages loop is in display_page_row.

Related: #10277

Related to #12443?

Handled in [15758].