On 2018/8/12 11:10 PM, Jens Axboe wrote:
> On 8/10/18 10:49 PM, Coly Li wrote:
>> On 2018/8/11 2:19 AM, Jens Axboe wrote:
>>> On 8/10/18 9:45 AM, Coly Li wrote:
>>>> Commit ea8c5356d390 ("bcache: set max writeback rate when I/O request
>>>> is idle") changes struct bch_ratelimit member rate from uint32_t to
>>>> atomic_long_t and uses atomic_long_set() in drivers/md/bcache/sysfs.c
>>>> to set new writeback rate, after the input is converted from memory
>>>> buf to long int by sysfs_strtoul_clamp().
>>>>
>>>> The above change has a problem because there is an implicit return
>>>> inside sysfs_strtoul_clamp() so the following atomic_long_set()
>>>> won't be called. This error is detected by 0day system with following
>>>> snipped smatch warnings:
>>>>
>>>> drivers/md/bcache/sysfs.c:271 __cached_dev_store() error: uninitialized
>>>> symbol 'v'.
>>>> 270 sysfs_strtoul_clamp(writeback_rate, v, 1, INT_MAX);
>>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>> @271 atomic_long_set(&dc->writeback_rate.rate, v);
>>>>
>>>> This patch fixes the above error by using strtoul_safe_clamp() to
>>>> convert the input buffer into a long int type result.
>>>>
>>>> Fixes: Commit ea8c5356d390 ("bcache: set max writeback rate when I/O request is idle")
>>>> Signed-off-by: Coly Li <colyli@xxxxxxx>
>>>> Cc: stable@xxxxxxxxxxxxxxx #4.16+
>>>> Cc: Kai Krakow <kai@xxxxxxxxxxx>
>>>> Cc: Stefan Priebe <s.priebe@xxxxxxxxxxxx>
>>>
>>
>> Hi Jens,
>>
>>> You don't need to CC stable for this, the commit isn't in a released kernel
>>> yet. In fact, it's not even in Linus's tree, it's just queued up for 4.19.
>>>
>>
>> What I thought was, Commit ea8c5356d390 ("bcache: set max writeback rate
>> when I/O request is idle") is a stable fix, so this patch should go into
>> stable as well. Otherwise the stable kernel cannot manually set
>> writeback_rate via sysfs interface.
>
> It's not necessary when new patch is correctly marked as fixing one that
> is going to stable.
>
Copied. Thanks for the hint.
Coly Li
