Re: [PATCH] md: protect read mddev->recovery in md_sync_action()

[Chen Cheng <chenchneg33@gmail.com>]

在 2026/6/27 18:46, Abd-Alrhman Masalkhi 写道:
> On Sat, Jun 27, 2026 at 18:29 +0800, Chen Cheng wrote:
>> From: Chen Cheng <chencheng@fnnas.com>
>>
>> md_sync_action() read mddev->recovery in lockless path, use READ_ONCE()
>> instead of u64 plain read.
>>
> unisgned long is not always u64...
> I can not see what it fixes, is this just to silence KCSAN? If so,
> please say so in the commit message.

I need to find KCSAN report , I lost this one, but I think it's easy to 
find locklessly path to call md_sync_action(), so. READ_ONCE is need.

> 
>> Fixes: e792a4c2156a3 ("md: add new helpers for sync_action")
>>
>> Signed-off-by: Chen Cheng <chencheng@fnnas.com>
>> ---
>>   drivers/md/md.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index c5c50640b684..f4415c1a79d9 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -5074,11 +5074,11 @@ static enum sync_action md_get_active_sync_action(struct mddev *mddev)
>>   	return is_recover ? ACTION_RECOVER : ACTION_IDLE;
>>   }
>>   
>>   enum sync_action md_sync_action(struct mddev *mddev)
>>   {
>> -	unsigned long recovery = mddev->recovery;
>> +	unsigned long recovery = READ_ONCE(mddev->recovery);
>>   	enum sync_action active_action;
>>   
>>   	/*
>>   	 * frozen has the highest priority, means running sync_thread will be
>>   	 * stopped immediately, and no new sync_thread can start.
>> -- 
>> 2.54.0
>>
>