xfs: make AGFL repair function avoid crosslinked blocks

Teach the AGFL repair function to check each block of the proposed AGFL
against the rmap btree.  If the rmapbt finds any mappings that are not
OWN_AG, strike that block from the list.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/scrub/agheader_repair.c

@@ -442,12 +442,18 @@ xrep_agf(
 /* AGFL */
 
 struct xrep_agfl {
+	/* Bitmap of alleged AGFL blocks that we're not going to add. */
+	struct xbitmap		crossed;
+
 	/* Bitmap of other OWN_AG metadata blocks. */
 	struct xbitmap		agmetablocks;
 
 	/* Bitmap of free space. */
 	struct xbitmap		*freesp;
 
+	/* rmapbt cursor for finding crosslinked blocks */
+	struct xfs_btree_cur	*rmap_cur;
+
 	struct xfs_scrub	*sc;
 };
 
@@ -477,6 +483,41 @@ xrep_agfl_walk_rmap(
 	return xbitmap_set_btcur_path(&ra->agmetablocks, cur);
 }
 
+/* Strike out the blocks that are cross-linked according to the rmapbt. */
+STATIC int
+xrep_agfl_check_extent(
+	struct xrep_agfl	*ra,
+	uint64_t		start,
+	uint64_t		len)
+{
+	xfs_agblock_t		agbno = XFS_FSB_TO_AGBNO(ra->sc->mp, start);
+	xfs_agblock_t		last_agbno = agbno + len - 1;
+	int			error;
+
+	ASSERT(XFS_FSB_TO_AGNO(ra->sc->mp, start) == ra->sc->sa.pag->pag_agno);
+
+	while (agbno <= last_agbno) {
+		bool		other_owners;
+
+		error = xfs_rmap_has_other_keys(ra->rmap_cur, agbno, 1,
+				&XFS_RMAP_OINFO_AG, &other_owners);
+		if (error)
+			return error;
+
+		if (other_owners) {
+			error = xbitmap_set(&ra->crossed, agbno, 1);
+			if (error)
+				return error;
+		}
+
+		if (xchk_should_terminate(ra->sc, &error))
+			return error;
+		agbno++;
+	}
+
+	return 0;
+}
+
 /*
  * Map out all the non-AGFL OWN_AG space in this AG so that we can deduce
  * which blocks belong to the AGFL.
@@ -496,44 +537,58 @@ xrep_agfl_collect_blocks(
 	struct xrep_agfl	ra;
 	struct xfs_mount	*mp = sc->mp;
 	struct xfs_btree_cur	*cur;
+	struct xbitmap_range	*br, *n;
 	int			error;
 
 	ra.sc = sc;
 	ra.freesp = agfl_extents;
 	xbitmap_init(&ra.agmetablocks);
+	xbitmap_init(&ra.crossed);
 
 	/* Find all space used by the free space btrees & rmapbt. */
 	cur = xfs_rmapbt_init_cursor(mp, sc->tp, agf_bp, sc->sa.pag);
 	error = xfs_rmap_query_all(cur, xrep_agfl_walk_rmap, &ra);
-	if (error)
-		goto err;
 	xfs_btree_del_cursor(cur, error);
+	if (error)
+		goto out_bmp;
 
 	/* Find all blocks currently being used by the bnobt. */
 	cur = xfs_allocbt_init_cursor(mp, sc->tp, agf_bp,
 			sc->sa.pag, XFS_BTNUM_BNO);
 	error = xbitmap_set_btblocks(&ra.agmetablocks, cur);
-	if (error)
-		goto err;
 	xfs_btree_del_cursor(cur, error);
+	if (error)
+		goto out_bmp;
 
 	/* Find all blocks currently being used by the cntbt. */
 	cur = xfs_allocbt_init_cursor(mp, sc->tp, agf_bp,
 			sc->sa.pag, XFS_BTNUM_CNT);
 	error = xbitmap_set_btblocks(&ra.agmetablocks, cur);
-	if (error)
-		goto err;
-
 	xfs_btree_del_cursor(cur, error);
+	if (error)
+		goto out_bmp;
 
 	/*
 	 * Drop the freesp meta blocks that are in use by btrees.
 	 * The remaining blocks /should/ be AGFL blocks.
 	 */
 	error = xbitmap_disunion(agfl_extents, &ra.agmetablocks);
-	xbitmap_destroy(&ra.agmetablocks);
 	if (error)
-		return error;
+		goto out_bmp;
+
+	/* Strike out the blocks that are cross-linked. */
+	ra.rmap_cur = xfs_rmapbt_init_cursor(mp, sc->tp, agf_bp, sc->sa.pag);
+	for_each_xbitmap_extent(br, n, agfl_extents) {
+		error = xrep_agfl_check_extent(&ra, br->start, br->len);
+		if (error)
+			break;
+	}
+	xfs_btree_del_cursor(ra.rmap_cur, error);
+	if (error)
+		goto out_bmp;
+	error = xbitmap_disunion(agfl_extents, &ra.crossed);
+	if (error)
+		goto out_bmp;
 
 	/*
 	 * Calculate the new AGFL size.  If we found more blocks than fit in
@@ -541,11 +596,10 @@ xrep_agfl_collect_blocks(
 	 */
 	*flcount = min_t(uint64_t, xbitmap_hweight(agfl_extents),
 			 xfs_agfl_size(mp));
-	return 0;
 
-err:
+out_bmp:
+	xbitmap_destroy(&ra.crossed);
 	xbitmap_destroy(&ra.agmetablocks);
-	xfs_btree_del_cursor(cur, error);
 	return error;
 }