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Commit e2f34e26 authored by Chuck Lever's avatar Chuck Lever Committed by Anna Schumaker
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xprtrdma: Yet another double DMA-unmap 



While chasing yet another set of DMAR fault reports, I noticed that
the frwr recycler conflates whether or not an MR has been DMA
unmapped with frwr->fr_state. Actually the two have only an indirect
relationship. It's in fact impossible to guess reliably whether the
MR has been DMA unmapped based on its fr_state field, especially as
the surrounding code and its assumptions have changed over time.

A better approach is to track the DMA mapping status explicitly so
that the recycler is less brittle to unexpected situations, and
attempts to DMA-unmap a second time are prevented.

Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org # v4.20
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent 594d1644

net/sunrpc/xprtrdma/frwr_ops.c

+4 −2
Original line number Diff line number Diff line
@@ -117,15 +117,15 @@ static void 
frwr_mr_recycle_worker(struct work_struct *work)

{

	struct rpcrdma_mr *mr = container_of(work, struct rpcrdma_mr, mr_recycle);

	enum rpcrdma_frwr_state state = mr->frwr.fr_state;

	struct rpcrdma_xprt *r_xprt = mr->mr_xprt;



	trace_xprtrdma_mr_recycle(mr);



	if (state != FRWR_FLUSHED_LI) {

	if (mr->mr_dir != DMA_NONE) {

		trace_xprtrdma_mr_unmap(mr);

		ib_dma_unmap_sg(r_xprt->rx_ia.ri_device,

				mr->mr_sg, mr->mr_nents, mr->mr_dir);

		mr->mr_dir = DMA_NONE;

	}



	spin_lock(&r_xprt->rx_buf.rb_mrlock);
@@ -150,6 +150,8 @@ frwr_op_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mr *mr) 
	if (!mr->mr_sg)

		goto out_list_err;



	frwr->fr_state = FRWR_IS_INVALID;

	mr->mr_dir = DMA_NONE;

	INIT_LIST_HEAD(&mr->mr_list);

	INIT_WORK(&mr->mr_recycle, frwr_mr_recycle_worker);

	sg_init_table(mr->mr_sg, depth);

net/sunrpc/xprtrdma/verbs.c

+6 −3
Original line number Diff line number Diff line
@@ -1329,9 +1329,12 @@ rpcrdma_mr_unmap_and_put(struct rpcrdma_mr *mr) 
{

	struct rpcrdma_xprt *r_xprt = mr->mr_xprt;



	if (mr->mr_dir != DMA_NONE) {

		trace_xprtrdma_mr_unmap(mr);

		ib_dma_unmap_sg(r_xprt->rx_ia.ri_device,

				mr->mr_sg, mr->mr_nents, mr->mr_dir);

		mr->mr_dir = DMA_NONE;

	}

	__rpcrdma_mr_put(&r_xprt->rx_buf, mr);

}