Re: [PATCH] btrfs: Fix passing 0 to ERR_PTR in btrfs_search_dir_index_item()

[Yue Haibing <yuehaibing@huawei.com>]

On 2024/10/22 14:37, Johannes Thumshirn wrote:
> On 22.10.24 05:22, Yue Haibing wrote:
>> On 2024/10/21 16:25, Johannes Thumshirn wrote:
>>> On 19.10.24 11:07, Yue Haibing wrote:
>>>> Return NULL instead of passing to ERR_PTR while ret is zero, this fix
>>>> smatch warnings:
>>>>
>>>> fs/btrfs/dir-item.c:353
>>>>    btrfs_search_dir_index_item() warn: passing zero to 'ERR_PTR'
>>>>
>>>> Fixes: 9dcbe16fccbb ("btrfs: use btrfs_for_each_slot in btrfs_search_dir_index_item")
>>>> Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
>>>> ---
>>>>    fs/btrfs/dir-item.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
>>>> index 001c0c2f872c..cdb30ec7366a 100644
>>>> --- a/fs/btrfs/dir-item.c
>>>> +++ b/fs/btrfs/dir-item.c
>>>> @@ -350,7 +350,7 @@ btrfs_search_dir_index_item(struct btrfs_root *root, struct btrfs_path *path,
>>>>    	if (ret > 0)
>>>>    		ret = 0;
>>>>    
>>>> -	return ERR_PTR(ret);
>>>> +	return ret ? ERR_PTR(ret) : NULL;
>>>>    }
>>>>    
>>>>    struct btrfs_dir_item *btrfs_lookup_xattr(struct btrfs_trans_handle *trans,
>>>
>>> The only caller to this is in btrfs_unlink_subvol(), which does the
>>> following:
>>>
>>>
>>>                    di = btrfs_search_dir_index_item(root, path, dir_ino,
>>> 						  &fname.disk_name);
>>>                    if (IS_ERR_OR_NULL(di)) {
>>>                            if (!di)
>>>                                    ret = -ENOENT;
>>>                            else
>>>                                    ret = PTR_ERR(di);
>>>                            btrfs_abort_transaction(trans, ret);
>>>                            goto out;
>>>                    }
>>>
>>> to do:
>>>
>>> diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
>>> index d3093eba54a5..e755228d909a 100644
>>> --- a/fs/btrfs/dir-item.c
>>> +++ b/fs/btrfs/dir-item.c
>>> @@ -345,10 +345,7 @@ btrfs_search_dir_index_item(struct btrfs_root
>>> *root, struct btrfs_path *path,
>>>                           return di;
>>>           }
>>>           /* Adjust return code if the key was not found in the next leaf. */
>>
>>
>> ret is output variable of btrfs_for_each_slot, that return value can be 0, if a
>> valid slot was found, 1 if there were no more leaves, and < 0 if there was an
>> error.
>>
> 
> Yes.
> 
>>> -       if (ret > 0)
>>> -               ret = 0;
>>> -
>>> -       return ERR_PTR(ret);
>>> +       return ERR_PTR(-ENOENT);
>>
>> This overwrite other ret code, which expecting return to upstream caller
> 
> Right for ret < 0, but for ret >= 0 we set it to 0 and then do return 
> (void*)0 a.k.a. return NULL.
> 
>>
>>>    }
>>>
>>>    struct btrfs_dir_item *btrfs_lookup_xattr(struct btrfs_trans_handle
>>> *trans,
>>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
>>> index 35f89d14c110..00602634db3a 100644
>>> --- a/fs/btrfs/inode.c
>>> +++ b/fs/btrfs/inode.c
>>> @@ -4337,11 +4337,8 @@ static int btrfs_unlink_subvol(struct
>>> btrfs_trans_handle *trans,
>>>            */
>>>           if (btrfs_ino(inode) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID) {
>>>                   di = btrfs_search_dir_index_item(root, path, dir_ino,
>>> &fname.disk_name);
>>> -               if (IS_ERR_OR_NULL(di)) {
>>> -                       if (!di)
>>> -                               ret = -ENOENT;
> 
> 
> and then set it to ENOENT if it is NULL. So it should be
> 
> if (ret >= 0)
> 	ret = -ENOENT;
> return ERR_PTR(-ENOENT);

Here should be
return ERR_PTR(ret);

Will rework and send v2, thanks!
> 
> and in the caller
> 
> if (IS_ERR(di)) {
> 	ret = PTR_ERR(di);
> 	btrfs_abort_transaction(...);
> 	break;
> }
> 
>