[PATCHSET 2/2] xfs: LLM-inspired iunlink repair bug fixes

Hi all,

These bugfixes got started as part of a series of assorted bug fixes.
However, in writing a test case to exercise weird corruption scenarios
I discovered a few more fixes, so I decided to collect them all in a
targeted series.

If you're going to start using this code, I strongly recommend pulling
from my git trees, which are linked below.

With a bit of luck, this should all go splendidly.
Comments and questions are, as always, welcome.

--D

kernel git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfs-linux.git/log/?h=llm-fixes-iunlink
---
Commits in this patchset:
 * xfs: hoist per-bucket unlinked list check to helper
 * xfs: don't livelock in scrub on a circular unlinked list
 * xfs: don't walk off the end of a null sc->sa.agi_bp in AGI repair
 * xfs: load next_agino from the correct xfarray in xrep_iunlink_relink_prev
 * xfs: pass runtime errors from xrep_iunlink_mark_ondisk_rec up to callers
 * xfs: check xfarray iteration errors when committing unlinked inode lists
 * xfs: fix allocated inodes that show up in the unlinked list
 * xfs: fix another iunlink infinite loop bug in online fsck
 * xfs: set the prev pointer when reinserting an inode on the unlinked list
---
 fs/xfs/scrub/trace.h           |    2 +
 fs/xfs/scrub/agheader.c        |   94 ++++++++++++++++++++++++++--------
 fs/xfs/scrub/agheader_repair.c |  110 +++++++++++++++++++++++++++++++++++-----
 3 files changed, 170 insertions(+), 36 deletions(-)