Re: [PATCH 1/3] iomap: don't resubmit an ioend after ->writeback_submit() failed

[Andrea Parri <parri.andrea@gmail.com>]

> Do you have a reproducer for this using some kind of error injection?

Yes.  xfs_reflink_convert_cow() is the only in-tree way
xfs_writeback_submit() can fail, so I added a boot param that forces
it to return -EIO, reflinked a file, dirtied several widely
separated CoW regions so writeback has to submit more than one
ioend, and let background writeback run under the fault injector.

On the unfixed kernel this reliably hits "list_add double add" in
__list_add_valid_or_report(), from the stale ioend's second
bio_endio() landing in xfs_end_bio() and relinking it into
ip->i_ioend_list. With the fix applied, writeback just fails cleanly
and there's no corruption.  Happy to describe the harness in more
detail if useful, it's throwaway boot-param/script scaffolding, not
something I'd want to send as-is.


> Overly long line here.

Fixed, will rewrap that comment for v2.

Thanks!
  Andrea