On 08/11/2018 08:35 AM, Darrick J. Wong wrote:
From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
In xrep_findroot_block, if we find a candidate root block with sibling
pointers or sibling blocks on the same tree level, we should not return
that block as a tree root because root blocks cannot have siblings.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
fs/xfs/scrub/repair.c | 47 +++++++++++++++++++++++++++++++++++++++++------
1 file changed, 41 insertions(+), 6 deletions(-)
diff --git a/fs/xfs/scrub/repair.c b/fs/xfs/scrub/repair.c
index 17cf48564390..42d8c798ce7d 100644
--- a/fs/xfs/scrub/repair.c
+++ b/fs/xfs/scrub/repair.c
@@ -690,6 +690,7 @@ xrep_findroot_block(
struct xfs_buf *bp;
struct xfs_btree_block *btblock;
xfs_daddr_t daddr;
+ int block_level;
int error;
daddr = XFS_AGB_TO_DADDR(mp, ri->sc->sa.agno, agbno);
@@ -727,17 +728,51 @@ xrep_findroot_block(
goto out;
bp->b_ops = fab->buf_ops;
- /* Ignore this block if it's lower in the tree than we've seen. */
- if (fab->root != NULLAGBLOCK &&
- xfs_btree_get_level(btblock) < fab->height)
- goto out;
-
/* Make sure we pass the verifiers. */
bp->b_ops->verify_read(bp);
if (bp->b_error)
goto out;
+
+ /* If we've recorded a root candidate... */
+ block_level = xfs_btree_get_level(btblock);
+ if (fab->root != NULLAGBLOCK) {
+ /*
+ * ...and this no-sibling root block candidate has the same
+ * level as the recorded candidate, there's no way we're going
+ * to accept any candidates at this tree level. Stash a root
+ * block of zero because the height is still valid, but no
+ * AG btree can root at agblock 0. Callers should verify the
+ * root agbno with xfs_verify_agbno...
+ */
+ if (block_level + 1 == fab->height) {
+ fab->root = 0;
+ goto out;
+ }
+
+ /*
+ * ...and this no-sibling root block is lower in the tree than
+ * the recorded root block candidate, just ignore it. There's
+ * still a strong chance that something is wrong with the btree
+ * itself, but that's not what we're fixing right now.
+ */
+ if (block_level < fab->height)
+ goto out;
+ }
+
+ /*
+ * Root blocks can't have siblings. This level can't be the root, so
+ * record the tree height (but not the ag block pointer) to force us to
+ * look for a higher level in the tree.
+ */
+ if (btblock->bb_u.s.bb_leftsib != cpu_to_be32(NULLAGBLOCK) ||
+ btblock->bb_u.s.bb_rightsib != cpu_to_be32(NULLAGBLOCK)) {
+ fab->root = 0;
+ fab->height = block_level + 1;
+ goto out;
+ }
+
fab->root = agbno;
- fab->height = xfs_btree_get_level(btblock) + 1;
+ fab->height = block_level + 1;
*found_it = true;
trace_xrep_findroot_block(mp, ri->sc->sa.agno, agbno,
Looks ok, thank you for the comments!
Reviewed-by: Allison Henderson <allison.henderson@xxxxxxxxxx>
