Re: [PATCH] fs: ratelimit __find_get_block_slow() failure message.

[Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>]

On 2019/01/11 19:40, Dmitry Vyukov wrote:
> On Fri, Jan 11, 2019 at 11:28 AM Tetsuo Handa
> <penguin-kernel@i-love.sakura.ne.jp> wrote:
>>
>> On 2019/01/11 19:19, Dmitry Vyukov wrote:
>>>> @@ -200,6 +200,7 @@ void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
>>>>         struct buffer_head *head;
>>>>         struct page *page;
>>>>         int all_mapped = 1;
>>>> +       static unsigned long last;
>>>
>>> /\/\/\/\/\/\
>>>
>>> We will have to re-fix this when we start testing with KTSAN, data
>>> race detector.
>>
>> What's wrong? This race is harmless.
> 
> How did you arrive to the conclusion that it is harmless?
> There is only one relevant standard covering this, which is the C
> language standard, and it is very clear on this -- this has Undefined
> Behavior, that is the same as, for example, reading/writing random
> pointers.
> 
> Check out this on how any race that you might think is benign can be
> badly miscompiled and lead to arbitrary program behavior:
> https://software.intel.com/en-us/blogs/2013/01/06/benign-data-races-what-could-possibly-go-wrong
> 

This is a "static" variable. In the Linux kernel's world,
"static" variable is automatically initialized to 0.

I just want to avoid bloated logs like https://syzkaller.appspot.com/text?tag=CrashLog&x=11f4a5e8c00000 .