Hi, John

在 2022/08/30 3:53, John Stoffel 写道:

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"Yu" == Yu Kuai [off-list ref] writes:

Yu> From: Yu Kuai [off-list ref]
Yu> 'conf->barrier' is protected by 'conf->resync_lock', reading
Yu> 'conf->barrier' without holding the lock is wrong.

Yu> Signed-off-by: Yu Kuai [off-list ref]
Yu> ---
Yu>  drivers/md/raid10.c | 2 +-
Yu>  1 file changed, 1 insertion(+), 1 deletion(-)

Yu> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
Yu> index 9117fcdee1be..b70c207f7932 100644
Yu> --- a/drivers/md/raid10.c
Yu> +++ b/drivers/md/raid10.c
Yu> @@ -930,8 +930,8 @@ static void flush_pending_writes(struct r10conf *conf)
  
Yu>  static void raise_barrier(struct r10conf *conf, int force)
Yu>  {
Yu> -	BUG_ON(force && !conf->barrier);
Yu>  	spin_lock_irq(&conf->resync_lock);
Yu> +	BUG_ON(force && !conf->barrier);

I don't like this BUG_ON() at all, why are you crashing the system
here instead of just doing a simple WARN_ONCE() instead?  Is there
anything the user can do to get into this situation on their own, or
does it really signify a logic error in the code?  If so, why are you
killing the system?

I'm not sure why to use the BUG_ON() here. I just noticed that
'conf->barrier' is read without holding 'resync_lock', and BUG_ON() can
be triggered false positive.

Thanks,
Kuai

  
Yu>  	/* Wait until no block IO is waiting (unless 'force') */
Yu>  	wait_event_lock_irq(conf->wait_barrier, force || !conf->nr_waiting,
Yu> --
Yu> 2.31.1


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