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: Zach Brown <zach.brown@oracle.com>
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Родитель
1bde04a63d
Коммит
ea819867b7
29
net/rds/ib.c
29
net/rds/ib.c
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@ -53,6 +53,12 @@ MODULE_PARM_DESC(fmr_message_size, " Max size of a RDMA transfer");
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module_param(rds_ib_retry_count, int, 0444);
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MODULE_PARM_DESC(rds_ib_retry_count, " Number of hw retries before reporting an error");
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/*
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* we have a clumsy combination of RCU and a rwsem protecting this list
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* because it is used both in the get_mr fast path and while blocking in
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* the FMR flushing path.
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*/
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DECLARE_RWSEM(rds_ib_devices_lock);
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struct list_head rds_ib_devices;
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/* NOTE: if also grabbing ibdev lock, grab this first */
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@ -171,7 +177,10 @@ void rds_ib_add_one(struct ib_device *device)
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INIT_LIST_HEAD(&rds_ibdev->ipaddr_list);
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INIT_LIST_HEAD(&rds_ibdev->conn_list);
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list_add_tail(&rds_ibdev->list, &rds_ib_devices);
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down_write(&rds_ib_devices_lock);
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list_add_tail_rcu(&rds_ibdev->list, &rds_ib_devices);
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up_write(&rds_ib_devices_lock);
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atomic_inc(&rds_ibdev->refcount);
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ib_set_client_data(device, &rds_ib_client, rds_ibdev);
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@ -230,16 +239,20 @@ void rds_ib_remove_one(struct ib_device *device)
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rds_ib_dev_shutdown(rds_ibdev);
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/*
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* prevent future connection attempts from getting a reference to this
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* device and wait for currently racing connection attempts to finish
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* getting their reference
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*/
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/* stop connection attempts from getting a reference to this device. */
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ib_set_client_data(device, &rds_ib_client, NULL);
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down_write(&rds_ib_devices_lock);
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list_del_rcu(&rds_ibdev->list);
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up_write(&rds_ib_devices_lock);
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/*
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* This synchronize rcu is waiting for readers of both the ib
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* client data and the devices list to finish before we drop
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* both of those references.
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*/
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synchronize_rcu();
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rds_ib_dev_put(rds_ibdev);
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list_del(&rds_ibdev->list);
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rds_ib_dev_put(rds_ibdev);
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}
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@ -23,6 +23,7 @@
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#define RDS_IB_RECYCLE_BATCH_COUNT 32
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extern struct rw_semaphore rds_ib_devices_lock;
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extern struct list_head rds_ib_devices;
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/*
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@ -94,8 +94,8 @@ static struct rds_ib_device *rds_ib_get_device(__be32 ipaddr)
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struct rds_ib_device *rds_ibdev;
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struct rds_ib_ipaddr *i_ipaddr;
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list_for_each_entry(rds_ibdev, &rds_ib_devices, list) {
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rcu_read_lock();
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rcu_read_lock();
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list_for_each_entry_rcu(rds_ibdev, &rds_ib_devices, list) {
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list_for_each_entry_rcu(i_ipaddr, &rds_ibdev->ipaddr_list, list) {
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if (i_ipaddr->ipaddr == ipaddr) {
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atomic_inc(&rds_ibdev->refcount);
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@ -103,8 +103,8 @@ static struct rds_ib_device *rds_ib_get_device(__be32 ipaddr)
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return rds_ibdev;
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}
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}
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rcu_read_unlock();
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}
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rcu_read_unlock();
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return NULL;
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}
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@ -761,12 +761,14 @@ void rds_ib_flush_mrs(void)
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{
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struct rds_ib_device *rds_ibdev;
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down_read(&rds_ib_devices_lock);
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list_for_each_entry(rds_ibdev, &rds_ib_devices, list) {
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struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;
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if (pool)
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rds_ib_flush_mr_pool(pool, 0, NULL);
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}
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up_read(&rds_ib_devices_lock);
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}
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void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents,
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