On 2018/11/16 下午4:13, Nikolay Borisov wrote:
>
>
> On 16.11.18 г. 9:54 ч., Qu Wenruo wrote:
>> The only location is the following code:
>>
>> int level = path->lowest_level + 1;
>> BUG_ON(path->lowest_level + 1 >= BTRFS_MAX_LEVEL);
>> while(level < BTRFS_MAX_LEVEL) {
>> slot = path->slots[level] + 1;
>> ...
>> }
>> path->slots[level] = slot;
>>
>> Again, it's the stupid compiler needs some hint for the fact that
>> we will always enter the while loop for at least once, thus @slot should
>> always be initialized.
>>
>> Fix it by assign level after the BUG_ON(), so the stupid compiler knows
>> we will always go into the while loop.
>>
>> Signed-off-by: Qu Wenruo <w...@suse.com>
>
> I don't get this warning on gcc 7.3. Also from your changelog it's not
> really clear what the compiler is confused about.
My gcc 8.2.1 reports it with "make W=1"
I'll just update the commit message with the original report:
ctree.c: In function 'btrfs_next_sibling_tree_block':
ctree.c:2990:21: warning: 'slot' may be used uninitialized in this
function [-Wmaybe-uninitialized]
path->slots[level] = slot;
~~~~~~~~~~~~~~~~~~~^~~~~~
Thanks,
Qu
>
> Codewise lgtm:
>
> Reviewed-by: Nikolay Borisov <nbori...@suse.com>
>
>> ---
>> ctree.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/ctree.c b/ctree.c
>> index 46e2ccedc0bf..9c9cb0dfdbf2 100644
>> --- a/ctree.c
>> +++ b/ctree.c
>> @@ -2961,11 +2961,12 @@ int btrfs_next_sibling_tree_block(struct
>> btrfs_fs_info *fs_info,
>> struct btrfs_path *path)
>> {
>> int slot;
>> - int level = path->lowest_level + 1;
>> + int level;
>> struct extent_buffer *c;
>> struct extent_buffer *next = NULL;
>>
>> BUG_ON(path->lowest_level + 1 >= BTRFS_MAX_LEVEL);
>> + level = path->lowest_level + 1;
>> while(level < BTRFS_MAX_LEVEL) {
>> if (!path->nodes[level])
>> return 1;
>>
