linux-kernel - Re: [PATCH 07/13] RDMA/rxe: Rename kfree_rcu() to kfree_rcu

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Message-ID: <20230310005529.GA339498@google.com>
Date:   Fri, 10 Mar 2023 00:55:29 +0000
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Uladzislau Rezki <urezki@...il.com>
Cc:     Zhu Yanjun <zyjzyj2000@...il.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>, linux-rdma@...r.kernel.org,
        Bob Pearson <rpearsonhpe@...il.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>,
        Jens Axboe <axboe@...nel.dk>,
        Philipp Reisner <philipp.reisner@...bit.com>,
        Bryan Tan <bryantan@...are.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Ariel Levkovich <lariel@...dia.com>,
        Theodore Ts'o <tytso@....edu>, Julian Anastasov <ja@....bg>
Subject: Re: [PATCH 07/13] RDMA/rxe: Rename kfree_rcu() to
 kfree_rcu_mightsleep()

On Thu, Mar 09, 2023 at 03:13:08PM +0100, Uladzislau Rezki wrote:
> > On Wed, Feb 01, 2023 at 04:08:13PM +0100, Uladzislau Rezki (Sony) wrote:
> > > The kfree_rcu()'s single argument name is deprecated therefore
> > > rename it to kfree_rcu_mightsleep() variant. The goal is explicitly
> > > underline that it is for sleepable contexts.
> > > 
> > > Please check the RXE driver in a way that a single argument can
> > > be used. Briefly looking at it and rcu_head should be embed to
> > > free an obj over RCU-core. The context might be atomic.
> > > 
> > > Cc: Bob Pearson <rpearsonhpe@...il.com>
> > > Cc: Jason Gunthorpe <jgg@...dia.com>
> > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> > > ---
> > >  drivers/infiniband/sw/rxe/rxe_pool.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > Could you please add you reviwed-by or Acked-by tags so we can bring
> > our series with renaming for the next merge window?
> > 
> > Thanks!
> > 
> __rxe_cleanup() can be called in two contexts, sleepable and not.
> Therefore usage of a single argument of the kvfree_rcu() is not correct
> here.
> 
> Could you please fix and check your driver? If my above statement
> is not correct, please provide Acked-by or Reviwed-by tags to the
> path that is in question.
> 
> Otherwise please add an rcu_head in your data to free objects over
> kvfree_rcu() using double argument API.
> 
> Could you please support?

Also this one needs renaming? It came in because of the commit in 6.3-rc1:
72a03627443d ("RDMA/rxe: Remove rxe_alloc()")

It could be squashed into this patch itself since it is infiniband related.

Paul noticed that this breaks dropping the old API on -next, so it is
blocking the renaming.

---8<-----------------------

diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
index b10aa1580a64..ae3a100e18fb 100644
--- a/drivers/infiniband/sw/rxe/rxe_mr.c
+++ b/drivers/infiniband/sw/rxe/rxe_mr.c
@@ -731,7 +731,7 @@ int rxe_dereg_mr(struct ib_mr *ibmr, struct ib_udata *udata)
 		return -EINVAL;
 
 	rxe_cleanup(mr);
-	kfree_rcu(mr);
+	kfree_rcu_mightsleep(mr);
 	return 0;
 }