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[174.3.196.123]) by smtp.gmail.com with ESMTPSA id v13-v6sm838020wrq.43.2018.06.12.13.33.26 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Jun 2018 13:33:26 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.86_2) (envelope-from ) id 1fSpyk-00077r-AU; Tue, 12 Jun 2018 14:33:22 -0600 Date: Tue, 12 Jun 2018 14:33:22 -0600 From: Jason Gunthorpe To: Matthew Wilcox Cc: hans.westgaard.ry@oracle.com, Doug Ledford , Matthew Wilcox , linux-rdma@vger.kernel.org, =?utf-8?B?SMOla29u?= Bugge , Parav Pandit , Jack Morgenstein , Pravin Shedge , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] IB/mad: Use IDR for agent IDs Message-ID: <20180612203322.GG6314@ziepe.ca> References: <20180608174218.32455-1-willy@infradead.org> <20180608174218.32455-3-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180608174218.32455-3-willy@infradead.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 08, 2018 at 10:42:18AM -0700, Matthew Wilcox wrote: > From: Matthew Wilcox > > Allocate agent IDs from a global IDR instead of an atomic variable. > This eliminates the possibility of reusing an ID which is already in > use after 4 billion registrations, and we can also limit the assigned > ID to be less than 2^24, which fixes a bug in the mlx4 device. > > We look up the agent under protection of the RCU lock, which means we > have to free the agent using kfree_rcu, and only increment the reference > counter if it is not 0. > > Signed-off-by: Matthew Wilcox > drivers/infiniband/core/mad.c | 78 ++++++++++++++++++------------ > drivers/infiniband/core/mad_priv.h | 7 +-- > include/linux/idr.h | 9 ++++ > 3 files changed, 59 insertions(+), 35 deletions(-) > > diff --git a/drivers/infiniband/core/mad.c b/drivers/infiniband/core/mad.c > index 68f4dda916c8..62384a3dd3ec 100644 > +++ b/drivers/infiniband/core/mad.c > @@ -38,6 +38,7 @@ > #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > > #include > +#include > #include > #include > #include > @@ -58,8 +59,8 @@ MODULE_PARM_DESC(send_queue_size, "Size of send queue in number of work requests > module_param_named(recv_queue_size, mad_recvq_size, int, 0444); > MODULE_PARM_DESC(recv_queue_size, "Size of receive queue in number of work requests"); > > +static DEFINE_IDR(ib_mad_clients); > static struct list_head ib_mad_port_list; > -static atomic_t ib_mad_client_id = ATOMIC_INIT(0); > > /* Port list lock */ > static DEFINE_SPINLOCK(ib_mad_port_list_lock); > @@ -377,13 +378,24 @@ struct ib_mad_agent *ib_register_mad_agent(struct ib_device *device, > goto error4; > } > > - spin_lock_irq(&port_priv->reg_lock); > - mad_agent_priv->agent.hi_tid = atomic_inc_return(&ib_mad_client_id); > + idr_preload(GFP_KERNEL); > + idr_lock(&ib_mad_clients); > + ret2 = idr_alloc_cyclic(&ib_mad_clients, mad_agent_priv, 0, > + (1 << 24), GFP_ATOMIC); I like this series, my only concern is this magic number here, at the very least it deserves a big comment explaining why it exists.. Let me see if I can get someone to give it some test time, I assume you haven't been able to test it it? > diff --git a/include/linux/idr.h b/include/linux/idr.h > index e856f4e0ab35..bef0df8600e2 100644 > +++ b/include/linux/idr.h > @@ -81,6 +81,15 @@ static inline void idr_set_cursor(struct idr *idr, unsigned int val) > WRITE_ONCE(idr->idr_next, val); > } > > +#define idr_lock(idr) xa_lock(&(idr)->idr_rt) > +#define idr_unlock(idr) xa_unlock(&(idr)->idr_rt) > +#define idr_lock_irq(idr) xa_lock_irq(&(idr)->idr_rt) > +#define idr_unlock_irq(idr) xa_unlock_irq(&(idr)->idr_rt) > +#define idr_lock_irqsave(idr, flags) \ > + xa_lock_irqsave(&(idr)->idr_rt, flags) > +#define idr_unlock_irqrestore(idr, flags) \ > + xa_unlock_irqrestore(&(idr)->idr_rt, flags) > + And you are Ok to take these through the rdma tree? Thanks, Jason