On 2019/2/19 上午12:58, fdman...@kernel.org wrote: > From: Filipe Manana <fdman...@suse.com> > > When there is a kind of corruption in an extent buffer such that its first > key does not match the key at the respective parent slot, one of two things > happens:
Isn't that handled by read_tree_block() already?
Thanks,
Qu
>
> 1) When assertions are enabled, we effectively hit a BUG_ON() which
> requires rebooting the machine later. This also does not tell any
> information about which extent buffer is affected, from which root,
> the expected and found keys, etc.
>
> 2) When assertions are disabled, we just ignore the mismatch and assume
> everything is ok, which can potentially lead to all sorts of unexpected
> problems later after a tree search (in the worst case, could lead to
> further silent corruption).
>
> So improve this by always checking if the first key of an extent buffer is
> what it's supposed to be, when doing a key search at key_search(), and
> report and return an appropriate error. The overhead is just comparing one
> key, which is minimal and is anyway just done in a special case where we
> skip the more expensive binary search (the binary search in the parent
> node returned 0, exact key match).
>
> Signed-off-by: Filipe Manana <fdman...@suse.com>
> ---
> fs/btrfs/ctree.c | 38 +++++++++++++++++---------------------
> 1 file changed, 17 insertions(+), 21 deletions(-)
>
> diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> index 5b9f602fb9e2..a0bd0278208d 100644
> --- a/fs/btrfs/ctree.c
> +++ b/fs/btrfs/ctree.c
> @@ -2529,35 +2529,31 @@ setup_nodes_for_search(struct btrfs_trans_handle
> *trans,
> return ret;
> }
>
> -static void key_search_validate(struct extent_buffer *b,
> - const struct btrfs_key *key,
> - int level)
> -{
> -#ifdef CONFIG_BTRFS_ASSERT
> - struct btrfs_disk_key disk_key;
> -
> - btrfs_cpu_key_to_disk(&disk_key, key);
> -
> - if (level == 0)
> - ASSERT(!memcmp_extent_buffer(b, &disk_key,
> - offsetof(struct btrfs_leaf, items[0].key),
> - sizeof(disk_key)));
> - else
> - ASSERT(!memcmp_extent_buffer(b, &disk_key,
> - offsetof(struct btrfs_node, ptrs[0].key),
> - sizeof(disk_key)));
> -#endif
> -}
> -
> static int key_search(struct extent_buffer *b, const struct btrfs_key *key,
> int level, int *prev_cmp, int *slot)
> {
> + struct btrfs_key found_key;
> +
> if (*prev_cmp != 0) {
> *prev_cmp = btrfs_bin_search(b, key, level, slot);
> return *prev_cmp;
> }
>
> - key_search_validate(b, key, level);
> + if (level == 0)
> + btrfs_item_key_to_cpu(b, &found_key, 0);
> + else
> + btrfs_node_key_to_cpu(b, &found_key, 0);
> +
> + if (btrfs_comp_cpu_keys(&found_key, key) != 0) {
> + btrfs_crit(b->fs_info,
> +"unexpected first key for extent buffer: bytenr=%llu level=%d root=%llu
> expected key=(%llu %u %llu) found key=(%llu %u %llu)",
> + btrfs_header_bytenr(b), level, btrfs_header_owner(b),
> + key->objectid, key->type, key->offset,
> + found_key.objectid, found_key.type,
> + found_key.offset);
> + return -EUCLEAN;
> + }
> +
> *slot = 0;
>
> return 0;
>
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