On Tue, Feb 19, 2019 at 12:26 PM Qu Wenruo <quwenruo.bt...@gmx.com> wrote: > > > > On 2019/2/19 下午7:59, Filipe Manana wrote: > > On Tue, Feb 19, 2019 at 12:54 AM Qu Wenruo <quwenruo.bt...@gmx.com> wrote: > >> > >> > >> > >> 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? > > > > It is, but only at the time we read a node/leaf from disk. > > By doing the check here we can actually catch other types of bugs and > > memory corruption. > > Although when memory corruption happens it's more concerning than > mismatch keys. > > > > > To be honest I missed that since this is motivated by a report on > > older kernel (SLE12 SP3). > > So I still find it useful to have due to the reason pointed above, > > however I'm not against simply removing the check from key_search(). > > Removing the check looks good to me. > Especially since we're going to have mandatory write time tree checker, > it should be mostly fine.
Looks reasonable. Sent as https://patchwork.kernel.org/patch/10821851/ and replaces the patch from this thread. > > Thanks, > Qu > > > > >> 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; > >>> > >> >
