[rds-devel] [PATCH net-next v5 2/2] net/rds: Delegate fan-out to a background worker

[Allison Henderson]

On Wed, 2026-02-25 at 17:33 +0100, Fernando Fernandez Mancera wrote:
> On 2/23/26 11:19 PM, Allison Henderson wrote:
> > From: Gerd Rausch <gerd.rausch at oracle.com>
> > 
> > Delegate fan-out to a background worker in order to allow
> > kernel_getpeername() to acquire a lock on the socket.
> > 
> > This has become necessary since the introduction of
> > commit "9dfc685e0262d ("inet: remove races in inet{6}_getname()")
> > 
> > The socket is already locked in the context that
> > "kernel_getpeername" used to get called by either
> > rds_tcp_recv_path" or "tcp_v{4,6}_rcv",
> > and therefore causing a deadlock.
> > 
> > Luckily, the fan-out need not happen in-context nor fast,
> > so we can easily just do the same in a background worker.
> > 
> > Also, while we're doing this, we get rid of the unused
> > struct members "t_conn_w", "t_send_w", "t_down_w" & "t_recv_w".
> > 
> > The fan-out work and the shutdown worker (cp_down_w) are both
> > queued on the same ordered workqueue (cp0->cp_wq), so they
> > cannot execute concurrently.  We only need cancel_work_sync()
> > in rds_tcp_conn_free() and rds_tcp_conn_path_connect() because
> > those run from outside the ordered workqueue.
> > 
> > Signed-off-by: Gerd Rausch <gerd.rausch at oracle.com>
> > Signed-off-by: Allison Henderson <achender at kernel.org>
> > ---
> >   net/rds/tcp.c         |  3 +++
> >   net/rds/tcp.h         |  7 ++----
> >   net/rds/tcp_connect.c |  2 ++
> >   net/rds/tcp_listen.c  | 54 +++++++++++++++++++++++++++++++------------
> >   4 files changed, 46 insertions(+), 20 deletions(-)
> > 
> 
> Isn't this change kind of dangerous since 021fd0f87004 ("net/rds: fix 
> recursive lock in rds_tcp_conn_slots_available") [1]?. Why is 
> kernel_getpeername() needed as only the peer source port is required for 
> the operation?

Thanks for the catch.  You're right, I missed that your fix would displace both patches.  I will drop this series for
now.  Thank you!

Allison

> 
> Thanks,
> Fernando.