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Date: Thu, 7 Jun 2018 15:37:50 +0000
From: Matthew Wilcox <mawilcox@...rosoft.com>
To: Hans Westgaard Ry <hans.westgaard.ry@...cle.com>,
Doug Ledford <dledford@...hat.com>,
Jason Gunthorpe <jgg@...pe.ca>,
Hakon Bugge <haakon.bugge@...cle.com>,
Parav Pandit <parav@...lanox.com>,
Jack Morgenstein <jackm@....mellanox.co.il>,
Pravin Shedge <pravin.shedge4linux@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Jeff Layton <jlayton@...nel.org>,
Wei Wang <wei.w.wang@...el.com>,
Chris Mi <chrism@...lanox.com>,
Eric Biggers <ebiggers@...gle.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Mel Gorman <mgorman@...hsingularity.net>,
"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 2/2] IB/mad: Use ID allocator routines to allocate
agent number
Why do you need the ID to increment like this? Why can't you just use a unique ID?
> -----Original Message-----
> From: Hans Westgaard Ry [mailto:hans.westgaard.ry@...cle.com]
> Sent: Thursday, June 7, 2018 7:15 AM
> To: Doug Ledford <dledford@...hat.com>; Jason Gunthorpe <jgg@...pe.ca>;
> Hakon Bugge <haakon.bugge@...cle.com>; Parav Pandit
> <parav@...lanox.com>; Jack Morgenstein <jackm@....mellanox.co.il>; Pravin
> Shedge <pravin.shedge4linux@...il.com>; Matthew Wilcox
> <mawilcox@...rosoft.com>; Andrew Morton <akpm@...ux-foundation.org>;
> Jeff Layton <jlayton@...nel.org>; Wei Wang <wei.w.wang@...el.com>; Chris
> Mi <chrism@...lanox.com>; Eric Biggers <ebiggers@...gle.com>; Rasmus
> Villemoes <linux@...musvillemoes.dk>; Mel Gorman
> <mgorman@...hsingularity.net>; linux-rdma@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: [PATCH v3 2/2] IB/mad: Use ID allocator routines to allocate agent
> number
>
> The agent TID is a 64 bit value split in two dwords. The least
> significant dword is the TID running counter. The most significant
> dword is the agent number. In the CX-3 shared port model, the mlx4
> driver uses the most significant byte of the agent number to store the
> slave number, making agent numbers greater and equal to 2^24 (3 bytes)
> unusable. The current codebase uses a variable which is incremented
> atomically for each new agent number giving too large agent numbers
> over time. The IDA set of functions are used instead of the simple
> counter approach. This allows re-use of agent numbers.
>
> The signature of the bug is a MAD layer that stops working and the
> console is flooded with messages like:
> mlx4_ib: egress mad has non-null tid msb:1 class:4 slave:0
>
> Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@...cle.com>
> ---
> drivers/infiniband/core/mad.c | 25 +++++++++++++++++++++----
> 1 file changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/infiniband/core/mad.c b/drivers/infiniband/core/mad.c
> index b28452a55a08..c01a2d63ffa2 100644
> --- a/drivers/infiniband/core/mad.c
> +++ b/drivers/infiniband/core/mad.c
> @@ -41,6 +41,7 @@
> #include <linux/slab.h>
> #include <linux/module.h>
> #include <linux/security.h>
> +#include <linux/idr.h>
> #include <rdma/ib_cache.h>
>
> #include "mad_priv.h"
> @@ -59,8 +60,7 @@ 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 struct list_head ib_mad_port_list;
> -static atomic_t ib_mad_client_id = ATOMIC_INIT(0);
> -
> +static DEFINE_IDA(ib_mad_client_ids);
> /* Port list lock */
> static DEFINE_SPINLOCK(ib_mad_port_list_lock);
>
> @@ -212,7 +212,7 @@ struct ib_mad_agent *ib_register_mad_agent(struct
> ib_device *device,
> int ret2, qpn;
> unsigned long flags;
> u8 mgmt_class, vclass;
> -
> + u32 ib_mad_client_id;
> /* Validate parameters */
> qpn = get_spl_qp_index(qp_type);
> if (qpn == -1) {
> @@ -375,9 +375,19 @@ struct ib_mad_agent *ib_register_mad_agent(struct
> ib_device *device,
> ret = ERR_PTR(ret2);
> goto error4;
> }
> + ib_mad_client_id = ida_simple_get_cyclic(&ib_mad_client_ids,
> + 1,
> + BIT(24) - 1,
> + GFP_KERNEL);
> + if (ib_mad_client_id < 0) {
> + pr_err("Couldn't allocate agent tid; errcode: %#x\n",
> + ib_mad_client_id);
> + ret = ERR_PTR(ib_mad_client_id);
> + goto error4;
> + }
> + mad_agent_priv->agent.hi_tid = ib_mad_client_id;
>
> spin_lock_irqsave(&port_priv->reg_lock, flags);
> - mad_agent_priv->agent.hi_tid =
> atomic_inc_return(&ib_mad_client_id);
>
> /*
> * Make sure MAD registration (if supplied)
> @@ -428,6 +438,8 @@ struct ib_mad_agent *ib_register_mad_agent(struct
> ib_device *device,
> error5:
> spin_unlock_irqrestore(&port_priv->reg_lock, flags);
> ib_mad_agent_security_cleanup(&mad_agent_priv->agent);
> + ida_simple_remove(&ib_mad_client_ids, ib_mad_client_id);
> +
> error4:
> kfree(reg_req);
> error3:
> @@ -576,6 +588,7 @@ static void unregister_mad_agent(struct
> ib_mad_agent_private *mad_agent_priv)
> {
> struct ib_mad_port_private *port_priv;
> unsigned long flags;
> + u32 ib_mad_client_id;
>
> /* Note that we could still be handling received MADs */
>
> @@ -587,6 +600,8 @@ static void unregister_mad_agent(struct
> ib_mad_agent_private *mad_agent_priv)
> port_priv = mad_agent_priv->qp_info->port_priv;
> cancel_delayed_work(&mad_agent_priv->timed_work);
>
> + ib_mad_client_id = mad_agent_priv->agent.hi_tid;
> +
> spin_lock_irqsave(&port_priv->reg_lock, flags);
> remove_mad_reg_req(mad_agent_priv);
> list_del(&mad_agent_priv->agent_list);
> @@ -602,6 +617,7 @@ static void unregister_mad_agent(struct
> ib_mad_agent_private *mad_agent_priv)
>
> kfree(mad_agent_priv->reg_req);
> kfree(mad_agent_priv);
> + ida_simple_remove(&ib_mad_client_ids, ib_mad_client_id);
> }
>
> static void unregister_mad_snoop(struct ib_mad_snoop_private
> *mad_snoop_priv)
> @@ -3347,4 +3363,5 @@ int ib_mad_init(void)
> void ib_mad_cleanup(void)
> {
> ib_unregister_client(&mad_client);
> + ida_destroy(&ib_mad_client_ids);
> }
> --
> 2.14.3
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