UBIFS corruptions - update

[Manfred Spraul]

Hi Richard,

as promised I tried to add backtrace support to my mtdram modification.

I don't like the result, the workflow is way to complex (good old 
ksymoops, ...)

Just dump_stack(), and then retain the output from dmesg would be simple 
and more efficient.

Thus I have abandoned the patch.


What I have are the results:

- chk_fs corruptions: With 4.15-rc2, the issue still exists.

The corruptions start when the background worker thread erases a page:

1st instance:

https://sourceforge.net/projects/calculix-rpm/files/ubifs-2/11_xattr/image-3754.bin/download

https://sourceforge.net/projects/calculix-rpm/files/ubifs-2/11_xattr/rec-syms-3753.txt/download

2nd instance:

https://sourceforge.net/projects/calculix-rpm/files/ubifs-2/11_xattr/image-5311.bin/download


- the garbage_collect_leb issue:

The issue happens during ubifs_tnc_end_commit(), called by sync().

I'm not sure about the root cause: Should ubifs_check_node() skip the 
index LEB? Or should the nodes never cross a page boundary?

https://sourceforge.net/projects/calculix-rpm/files/ubifs-2/11_xattr/image-167836.bin/download

https://sourceforge.net/projects/calculix-rpm/files/ubifs-2/11_xattr/rec-syms-167837.txt/download

https://sourceforge.net/projects/calculix-rpm/files/ubifs-2/11_xattr/r-167836.txt/download


Without xattr, the garbage_collect_leb issue did not happen, I tested 
around 40.000 images.


@Richard: Is there something where I could support? I fear more data 
would just cause confusion.

For me, there appears to be two reproducible issues:

- garbage_collect_leb: Fairly rare

- Failure with chk_fs enabled. Easy to reproduce, more common.


--

     Manfred