Btrfs: kill BUG_ON in do_relocation
While updating btree, we try to push items between sibling nodes/leaves in order to keep height as low as possible. But we don't memset the original places with zero when pushing items so that we could end up leaving stale content in nodes/leaves. One may read the above stale content by increasing btree blocks' @nritems. One case I've come across is that in fs tree, a leaf has two parent nodes, hence running balance ends up with processing this leaf with two parent nodes, but it can only reach the valid parent node through btrfs_search_slot, so it'd be like, do_relocation for P in all parent nodes of block A: if !P->eb: btrfs_search_slot(key); --> get path from P to A. if lowest: BUG_ON(A->bytenr != bytenr of A recorded in P); btrfs_cow_block(P, A); --> change A's bytenr in P. After btrfs_cow_block, P has the new bytenr of A, but with the same @key, we get the same path again, and get panic by BUG_ON. Note that this is only happening in a corrupted fs, for a regular fs in which we have correct @nritems so that we won't read stale content in any case. Reviewed-by:Josef Bacik <jbacik@fb.com> Signed-off-by:
Liu Bo <bo.li.liu@oracle.com> Signed-off-by:
David Sterba <dsterba@suse.com>
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