[FS#579] Rename failure when file both in rom and overlay in mvebu / wrt3200acm, due to kernel 4.9 or ubi?

[LEDE Bugs]

The following task has a new comment added:

FS#579 - Rename failure when file both in rom and overlay in mvebu / wrt3200acm, due to kernel 4.9 or ubi? 
User who did this - Hannu Nyman (hnyman)

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r3509-2374549916 kernel 4.4 : rename works ok.
r3510-2bf9ea6a31 kernel 4.9 : fails to rename

I compiled the last commit where mvebu is with kernel 4.4 and rename works normally. The next commit bumping mvebu to 4.9 makes rename to fail. So this bug came with kernel 4.9.

I have no idea if this is restricted to mvebu or if this concerns all 4.9 targets (using ubifs?).

Supposedly kernel 4.9 supports ubifs rename "built-in", so the patches for that (052-...) were dropped from LEDE's generic patches-4.9

Linux kernel's ubifs rename support commits have been committed on 2016-10-02:
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/log/fs/ubifs?h=linux-4.9.y

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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=579#comment2029