[PATCH 4/5] xfs: report nonexistent parents as a filesystem corruption

From: Darrick J. Wong <[email protected]>

LOLLM noticed that when the directory tree scrubber tries to walk up a
parent pointer but the parent inumber doesn't point to an allocated
inode, we allow the EINVAL/ENOENT error code to bubble up to userspace.
That's not right, we should be reporting that as a cross-referencing
error so that someone runs the parent pointer checker.

Also add a termination check to xchk_dirpath_step_up because it's a loop
body function.

Cc: <[email protected]> # v6.10
Fixes: 928b721a11789a ("xfs: teach online scrub to find directory tree structure problems")
Signed-off-by: "Darrick J. Wong" <[email protected]>
Assisted-by: LOLLM # finding obvious bugs
---
 fs/xfs/scrub/trace.h   |   33 +++++++++++++++++++++++++++++++++
 fs/xfs/scrub/dirtree.c |   30 ++++++++++++++++++++++++++++--
 2 files changed, 61 insertions(+), 2 deletions(-)


diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index 362c6d39e9f580..0f5adc293962fa 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -1706,6 +1706,39 @@ DEFINE_EVENT(xchk_dirtree_class, name, \
 DEFINE_XCHK_DIRTREE_EVENT(xchk_dirtree_create_path);
 DEFINE_XCHK_DIRTREE_EVENT(xchk_dirpath_walk_upwards);
 
+TRACE_EVENT(xchk_dirpath_badino,
+	TP_PROTO(struct xfs_scrub *sc, unsigned int path_nr,
+		unsigned int step_nr, const struct xfs_name *name,
+		const struct xfs_parent_rec *pptr),
+	TP_ARGS(sc, path_nr, step_nr, name, pptr),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(unsigned int, path_nr)
+		__field(unsigned int, step_nr)
+		__field(xfs_ino_t, parent_ino)
+		__field(unsigned int, parent_gen)
+		__field(unsigned int, namelen)
+		__dynamic_array(char, name, name->len)
+	),
+	TP_fast_assign(
+		__entry->dev = sc->mp->m_super->s_dev;
+		__entry->path_nr = path_nr;
+		__entry->step_nr = step_nr;
+		__entry->parent_ino = be64_to_cpu(pptr->p_ino);
+		__entry->parent_gen = be32_to_cpu(pptr->p_gen);
+		__entry->namelen = name->len;
+		memcpy(__get_str(name), name->name, name->len);
+	),
+	TP_printk("dev %d:%d path %u step %u parent_ino 0x%llx parent_gen 0x%x name '%.*s'",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->path_nr,
+		  __entry->step_nr,
+		  __entry->parent_ino,
+		  __entry->parent_gen,
+		  __entry->namelen,
+		  __get_str(name))
+);
+
 DECLARE_EVENT_CLASS(xchk_dirpath_class,
 	TP_PROTO(struct xfs_scrub *sc, struct xfs_inode *ip,
 		 unsigned int path_nr, unsigned int step_nr,
diff --git a/fs/xfs/scrub/dirtree.c b/fs/xfs/scrub/dirtree.c
index b2cf6e5439d915..717cbac2956238 100644
--- a/fs/xfs/scrub/dirtree.c
+++ b/fs/xfs/scrub/dirtree.c
@@ -368,12 +368,38 @@ xchk_dirpath_step_up(
 	struct xfs_inode	*dp;
 	xfs_ino_t		parent_ino = be64_to_cpu(dl->pptr_rec.p_ino);
 	unsigned int		lock_mode;
-	int			error;
+	int			error = 0;
+
+	if (xchk_should_terminate(sc, &error))
+		return error;
 
 	/* Grab and lock the parent directory. */
 	error = xchk_iget(sc, parent_ino, &dp);
-	if (error)
+	switch (error) {
+	case -EINVAL:
+	case -ENOENT:
+		mutex_lock(&dl->lock);
+
+		if (dl->stale) {
+			/* live update detected a change in this path */
+			error = -ESTALE;
+		} else {
+			/* inode doesn't exist, path invalid */
+			error = -EFSCORRUPTED;
+
+			trace_xchk_dirpath_badino(dl->sc, path->path_nr,
+					path->nr_steps, &dl->xname,
+					&dl->pptr_rec);
+		}
+
+		mutex_unlock(&dl->lock);
 		return error;
+	case 0:
+		/* keep going */
+		break;
+	default:
+		return error;
+	}
 
 	lock_mode = xfs_ilock_attr_map_shared(dp);
 	mutex_lock(&dl->lock);