[PATCH 4/4] xfs: make AGFL repair function avoid crosslinked blocks

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

From: Darrick J. Wong <djwong@xxxxxxxxxx>

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@xxxxxxxxxx>
---
 fs/xfs/scrub/agheader_repair.c |   78 ++++++++++++++++++++++++++++++++++------
 1 file changed, 66 insertions(+), 12 deletions(-)


diff --git a/fs/xfs/scrub/agheader_repair.c b/fs/xfs/scrub/agheader_repair.c
index 2e75ff9b5b2e..82ceb60ea5fc 100644
--- a/fs/xfs/scrub/agheader_repair.c
+++ b/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;
 }