Re: [PATCH 1/4] xfs: xrep_findroot_block should reject root blocks with siblings
From: Brian Foster <hidden>
Date: 2018-08-09 15:33:31
On Tue, Aug 07, 2018 at 08:57:06PM -0700, Darrick J. Wong wrote:
quoted hunk ↗ jump to hunk
From: Darrick J. Wong <redacted> 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 <redacted> --- fs/xfs/scrub/repair.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)diff --git a/fs/xfs/scrub/repair.c b/fs/xfs/scrub/repair.c index 85b048b341a0..6c199e2ebb81 100644 --- a/fs/xfs/scrub/repair.c +++ b/fs/xfs/scrub/repair.c@@ -727,6 +727,23 @@ xrep_findroot_block( bp->b_ops->verify_read(bp); if (bp->b_error) goto out; + + /* Root blocks can't have siblings. */ + if (btblock->bb_u.s.bb_leftsib != cpu_to_be32(NULLAGBLOCK) || + btblock->bb_u.s.bb_rightsib != cpu_to_be32(NULLAGBLOCK)) + goto out; + + /* + * If we find a second block at this level, ignore this level because + * it can't possibly be a root level. Maybe we'll find a higher level, + * or maybe the rmap information is garbage. + */ + if (fab->root != NULLAGBLOCK && + fab->height == xfs_btree_get_level(btblock) + 1) { + fab->root = NULLAGBLOCK; + goto out; + }
Ok, but is this enough? Won't resetting fab->root like this mean that we'd just reassign it to the next block we find at this level? I'm wondering if we should maintain ->height independently and anticipate that (height == <valid> && root == NULLAGBLOCK) means we couldn't find a valid root. That may also allow for more efficient height filtering during the query. Brian
+ fab->root = agbno; fab->height = xfs_btree_get_level(btblock) + 1; *found_it = true; -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html