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Commit ea819867 authored by Zach Brown's avatar Zach Brown Committed by Andy Grover
Browse files

RDS/IB: protect the list of IB devices 



The RDS IB device list wasn't protected by any locking.  Traversal in
both the get_mr and FMR flushing paths could race with additon and
removal.

List manipulation is done with RCU primatives and is protected by the
write side of a rwsem.  The list traversal in the get_mr fast path is
protected by a rcu read critical section.  The FMR list traversal is
more problematic because it can block while traversing the list.  We
protect this with the read side of the rwsem.

Signed-off-by: default avatarZach Brown <zach.brown@oracle.com>
parent 1bde04a6

net/rds/ib.c

+20 −7
Original line number Diff line number Diff line
@@ -53,6 +53,12 @@ MODULE_PARM_DESC(fmr_message_size, " Max size of a RDMA transfer"); 
module_param(rds_ib_retry_count, int, 0444);

MODULE_PARM_DESC(rds_ib_retry_count, " Number of hw retries before reporting an error");



/*

 * we have a clumsy combination of RCU and a rwsem protecting this list

 * because it is used both in the get_mr fast path and while blocking in

 * the FMR flushing path.

 */

DECLARE_RWSEM(rds_ib_devices_lock);

struct list_head rds_ib_devices;



/* NOTE: if also grabbing ibdev lock, grab this first */
@@ -171,7 +177,10 @@ void rds_ib_add_one(struct ib_device *device) 


	INIT_LIST_HEAD(&rds_ibdev->ipaddr_list);

	INIT_LIST_HEAD(&rds_ibdev->conn_list);

	list_add_tail(&rds_ibdev->list, &rds_ib_devices);



	down_write(&rds_ib_devices_lock);

	list_add_tail_rcu(&rds_ibdev->list, &rds_ib_devices);

	up_write(&rds_ib_devices_lock);

	atomic_inc(&rds_ibdev->refcount);



	ib_set_client_data(device, &rds_ib_client, rds_ibdev);
@@ -230,16 +239,20 @@ void rds_ib_remove_one(struct ib_device *device) 


	rds_ib_dev_shutdown(rds_ibdev);



	/* stop connection attempts from getting a reference to this device. */

	ib_set_client_data(device, &rds_ib_client, NULL);



	down_write(&rds_ib_devices_lock);

	list_del_rcu(&rds_ibdev->list);

	up_write(&rds_ib_devices_lock);



	/*

	 * prevent future connection attempts from getting a reference to this

	 * device and wait for currently racing connection attempts to finish

	 * getting their reference

	 * This synchronize rcu is waiting for readers of both the ib

	 * client data and the devices list to finish before we drop

	 * both of those references.

	 */

	ib_set_client_data(device, &rds_ib_client, NULL);

	synchronize_rcu();

	rds_ib_dev_put(rds_ibdev);



	list_del(&rds_ibdev->list);

	rds_ib_dev_put(rds_ibdev);

}

net/rds/ib.h

+1 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 


#define RDS_IB_RECYCLE_BATCH_COUNT	32



extern struct rw_semaphore rds_ib_devices_lock;

extern struct list_head rds_ib_devices;



/*

net/rds/ib_rdma.c

+5 −3
Original line number Diff line number Diff line
@@ -94,8 +94,8 @@ static struct rds_ib_device *rds_ib_get_device(__be32 ipaddr) 
	struct rds_ib_device *rds_ibdev;

	struct rds_ib_ipaddr *i_ipaddr;



	list_for_each_entry(rds_ibdev, &rds_ib_devices, list) {

	rcu_read_lock();

	list_for_each_entry_rcu(rds_ibdev, &rds_ib_devices, list) {

		list_for_each_entry_rcu(i_ipaddr, &rds_ibdev->ipaddr_list, list) {

			if (i_ipaddr->ipaddr == ipaddr) {

				atomic_inc(&rds_ibdev->refcount);
@@ -103,8 +103,8 @@ static struct rds_ib_device *rds_ib_get_device(__be32 ipaddr) 
				return rds_ibdev;

			}

		}

		rcu_read_unlock();

	}

	rcu_read_unlock();



	return NULL;

}
@@ -761,12 +761,14 @@ void rds_ib_flush_mrs(void) 
{

	struct rds_ib_device *rds_ibdev;



	down_read(&rds_ib_devices_lock);

	list_for_each_entry(rds_ibdev, &rds_ib_devices, list) {

		struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;



		if (pool)

			rds_ib_flush_mr_pool(pool, 0, NULL);

	}

	up_read(&rds_ib_devices_lock);

}



void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents,