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

[Chen Cheng]

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@xxxxxxxxx>
> >
> > 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@xxxxxxxxx>
> > ---
> >   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