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isert-scst: Fix race condition between login request and scst teardown flow

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On scst teardown we call rdma_disconnect() on all connections.
this moves the qps to error state and flushes all the wc, including
the drain wc which will results in kref_put of the connection.

In a race condition with the connection request, we might be only in
the init stage of the ref, and calling kref_put will result in refcount
0 and freeing the connection while establishing it.

Call the first kref_get before rdma_accept() to prevent this race.

Signed-off-by: Ariel Nahum <arieln@mellanox.com>
Signed-off-by: Yan Burman <yanb@mellanox.com>


git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@6486 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Bart Van Assche
2015-08-27 17:53:32 +00:00
parent 3732ee39f8
commit 175463ca84
1 changed files with 8 additions and 1 deletions
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9
iscsi-scst/kernel/isert-scst/iser_rdma.c
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@@ -1345,6 +1345,8 @@ static int isert_cm_conn_req_handler(struct rdma_cm_id *cm_id,
tgt_conn_param.private_data = &cm_hdr;
cm_hdr.flags = ISER_ZBVA_NOT_SUPPORTED | ISER_SEND_W_INV_NOT_SUPPORTED;
kref_get(&isert_conn->kref);
err = rdma_accept(cm_id, &tgt_conn_param);
if (unlikely(err)) {
pr_err("Failed to accept conn request, err:%d\n", err);
@@ -1422,7 +1424,6 @@ static int isert_cm_connect_handler(struct rdma_cm_id *cm_id,
if (unlikely(ret))
goto out;
kref_get(&isert_conn->kref);
kref_get(&isert_conn->kref);
/* notify upper layer */
ret = isert_conn_established(&isert_conn->iscsi,
@@ -1592,6 +1593,12 @@ static int isert_cm_evt_handler(struct rdma_cm_id *cm_id,
isert_conn = cm_id->qp->qp_context;
set_bit(ISERT_CONNECTION_ABORTED, &isert_conn->flags);
/*
* reaching here must be with the isert_conn refcount of 2,
* one from the init and one from the connect request,
* thus it is safe to deref directly before the sched_conn_closed
*/
isert_conn_free(isert_conn);
isert_sched_conn_closed(isert_conn);
err = 0;
}