Re: UBIFS file-system corruption (missing inode) after power-cut on 4.14.96

[Lars Persson <lists@xxxxxxx>]

On Tue, Mar 26, 2019 at 10:21 AM Lars Persson <lists@xxxxxxx> wrote:
>
> On Thu, Mar 21, 2019 at 11:02 AM Lars Persson <lists@xxxxxxx> wrote:
> >
> > The missing inode is always triggered on those two particular files
> > emotiond.conf and tampering.conf that share the same write pattern at startup:
> >
> >  cp file file.tmp
> >  echo some data > file.tmp
> >  mv file.tmp file
> >  fsync file
> >
>
> A closer look at that script shows that the atomic file update part
> was bypassed. It only performs a chown operation on that file.
> That simple chown will trigger an overlayfs copyup operation.
>
> With a proper unmount after the system has finished writing to /etc I
> cannot reproduce any corruption. An unclean shutdown triggers
> corruption in about 1/3 of the attempts, also when I cut power tens of
> seconds after the problematic script has executed.

OK I think I have found the bug.

Commit 32fe905c17f0 ("Fix O_TMPFILE corner case in ubifs_link()")
tried to fix the use of O_TMPFILE by removing an inode from the orphan
list when it is relinked.

Unfortunately the removal never gets committed to flash because the
removal of an orphan does not trigger a commit. The condition for
committing is that new_orphans > 0, but in our case it is zero after
the call to ubifs_delete_orphan().

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