xfs: pass runtime errors from xrep_iunlink_mark_ondisk_rec up to callers

LOLLM points out that the only error that xrep_iunlink_mark_ondisk_rec
returns is ENOMEM, but we ignore that, and can end up writing a garbage
AGI based on incomplete information.  We shouldn't do that, though here
we must be screen out EFSCORRUPTED/EFSBASDCRC because we haven't
checked the inobt yet.

Cc: stable@vger.kernel.org # v6.10
Fixes: ab97f4b1c0 ("xfs: repair AGI unlinked inode bucket lists")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Assisted-by: LOLLM # finding obvious bugs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

fs/xfs/scrub/agheader_repair.c

@@ -1309,7 +1309,7 @@ xrep_iunlink_mark_ondisk_rec(
  * iunlink_bmp.   We haven't checked the inobt yet, so we don't error out if
  * the btree is corrupt.
  */
-STATIC void
+STATIC int
 xrep_iunlink_mark_ondisk(
 	struct xrep_agi		*ragi)
 {
@@ -1321,6 +1321,14 @@ xrep_iunlink_mark_ondisk(
 	cur = xfs_inobt_init_cursor(sc->sa.pag, sc->tp, agi_bp);
 	error = xfs_btree_query_all(cur, xrep_iunlink_mark_ondisk_rec, ragi);
 	xfs_btree_del_cursor(cur, error);
+
+	/*
+	 * Don't proceed if we couldn't set a bit in the bitmap.  All other
+	 * errors we ignore because we haven't actually checked the inobt yet.
+	 */
+	if (error == -ENOMEM)
+		return -ENOMEM;
+	return 0;
 }
 
 /*
@@ -1508,7 +1516,9 @@ xrep_iunlink_rebuild_buckets(
 	 * If there are ondisk inodes that are unlinked and are not been loaded
 	 * into cache, record them in iunlink_bmp.
 	 */
-	xrep_iunlink_mark_ondisk(ragi);
+	error = xrep_iunlink_mark_ondisk(ragi);
+	if (error)
+		return error;
 
 	/*
 	 * Walk each iunlink bucket to (re)construct as much of the incore list