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RDMA/ucma: Discard all events for new connections until accepted 

After reporting a new connection request to user space, the rdma_ucm
will discard subsequent events until the user has associated a user
space idenfier with the kernel cm_id.  This is needed to avoid
reporting a reject/disconnect event to the user for a request that
they may not have processed.

The user space identifier is set once the user tries to accept the
connection request.  However, the following race exists in ucma_accept():

	ctx->uid = cmd.uid;
	<events may be reported now>
	ret = rdma_accept(ctx->cm_id, ...);

Once ctx->uid has been set, new events may be reported to the user.
While the above mentioned race is avoided, there is an issue that the
user _may_ receive a reject/disconnect event if rdma_accept() fails,
depending on when the event is processed.  To simplify the use of
rdma_accept(), discard all events unless rdma_accept() succeeds.

This problem was discovered based on questions from Roland Dreier
<roland@purestorage.com>.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
This commit is contained in:
Sean Hefty 2012-01-10 23:53:41 +00:00 committed by Roland Dreier
parent dcd6c92267
commit 9ced69ca52
1 changed files with 4 additions and 1 deletions
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5
drivers/infiniband/core/ucma.c
View File

@ -808,9 +808,12 @@ static ssize_t ucma_accept(struct ucma_file *file, const char __user *inbuf,
return PTR_ERR(ctx);
if (cmd.conn_param.valid) {
ctx->uid = cmd.uid;
ucma_copy_conn_param(&conn_param, &cmd.conn_param);
mutex_lock(&file->mut);
ret = rdma_accept(ctx->cm_id, &conn_param);
if (!ret)
ctx->uid = cmd.uid;
mutex_unlock(&file->mut);
} else
ret = rdma_accept(ctx->cm_id, NULL);