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.
> Also, the fixes line should be:
>
> Fixes: ea8c5356d390 ("bcache: set max writeback rate when I/O request is idle")
>
> (no Commit). I missed that on some of your earlier commits.
Copied, keep in mind for next time.
>
> Applied with those edits, and some wording changes.
>
Thanks for your help !
Coly Li
