Re: [PATCH -next v4] staging: fwserial: Switch to kfree_rcu() API

[Dan Carpenter <dan.carpenter@oracle.com>]

On Mon, Sep 19, 2022 at 05:43:33PM +0800, shangxiaojing wrote:
> 
> On 2022/9/19 17:11, Greg KH wrote:
> > On Mon, Sep 19, 2022 at 05:10:56PM +0800, Shang XiaoJing wrote:
> > > Instead of invoking a synchronize_rcu() to free a pointer after a grace
> > > period, we can directly make use of a new API that does the same but in
> > > a more efficient way.
> > > 
> > > Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
> > > ---
> > > Changelog:
> > > v3: the first version of the PATCH
> > > v1: v3 resent as v1
> > > v2: use kfree_rcu() instead of kvfree_rcu() for clarity
> > > v4: resend v2 as v4 to avoid versioning confusion
> > > ---
> > >   drivers/staging/fwserial/fwserial.c | 3 +--
> > >   1 file changed, 1 insertion(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/staging/fwserial/fwserial.c b/drivers/staging/fwserial/fwserial.c
> > > index 81b06d88ed0d..8d2b4ed1f39e 100644
> > > --- a/drivers/staging/fwserial/fwserial.c
> > > +++ b/drivers/staging/fwserial/fwserial.c
> > > @@ -2117,8 +2117,7 @@ static void fwserial_remove_peer(struct fwtty_peer *peer)
> > >   	if (port)
> > >   		fwserial_release_port(port, true);
> > > -	synchronize_rcu();
> > > -	kfree(peer);
> > > +	kfree_rcu(peer);
> 
> The kfree_rcu(peer) should be kfree_rcu(peer, rcu), due to the rcu_head
> member named rcu in fwtty_peer.

Oh, huh.  What happens if you don't pas the "rcu" parameter?  I see
there is a similar instance in ext4_apply_quota_options().

		kfree_rcu(qname);

regards,
dan carpenter