IB: Add a QP creation flag to use GFP_NOIO allocations

This addresses a problem where NFS client writes over IPoIB connected
mode may deadlock on memory allocation/writeback.

The problem is not directly memory reclamation.  There is an indirect
dependency between network filesystems writing back pages and
ipoib_cm_tx_init() due to how a kworker is used.  Page reclaim cannot
make forward progress until ipoib_cm_tx_init() succeeds and it is
stuck in page reclaim itself waiting for network transmission.
Ordinarily this situation may be avoided by having the caller use
GFP_NOFS but ipoib_cm_tx_init() does not have that information.

To address this, take a general approach and add a new QP creation
flag that tells the low-level hardware driver to use GFP_NOIO for the
memory allocations related to the new QP.

Use the new flag in the ipoib connected mode path, and if the driver
doesn't support it, re-issue the QP creation without the flag.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/ulp/ipoib/ipoib_cm.c

@@ -1030,10 +1030,20 @@ static struct ib_qp *ipoib_cm_create_tx_qp(struct net_device *dev, struct ipoib_
 		.cap.max_send_sge	= 1,
 		.sq_sig_type		= IB_SIGNAL_ALL_WR,
 		.qp_type		= IB_QPT_RC,
-		.qp_context		= tx
+		.qp_context		= tx,
+		.create_flags		= IB_QP_CREATE_USE_GFP_NOIO
 	};
 
-	return ib_create_qp(priv->pd, &attr);
+	struct ib_qp *tx_qp;
+
+	tx_qp = ib_create_qp(priv->pd, &attr);
+	if (PTR_ERR(tx_qp) == -EINVAL) {
+		ipoib_warn(priv, "can't use GFP_NOIO for QPs on device %s, using GFP_KERNEL\n",
+			   priv->ca->name);
+		attr.create_flags &= ~IB_QP_CREATE_USE_GFP_NOIO;
+		tx_qp = ib_create_qp(priv->pd, &attr);
+	}
+	return tx_qp;
 }
 
 static int ipoib_cm_send_req(struct net_device *dev,
@@ -1104,12 +1114,14 @@ static int ipoib_cm_tx_init(struct ipoib_cm_tx *p, u32 qpn,
 	struct ipoib_dev_priv *priv = netdev_priv(p->dev);
 	int ret;
 
-	p->tx_ring = vzalloc(ipoib_sendq_size * sizeof *p->tx_ring);
+	p->tx_ring = __vmalloc(ipoib_sendq_size * sizeof *p->tx_ring,
+			       GFP_NOIO, PAGE_KERNEL);
 	if (!p->tx_ring) {
 		ipoib_warn(priv, "failed to allocate tx ring\n");
 		ret = -ENOMEM;
 		goto err_tx;
 	}
+	memset(p->tx_ring, 0, ipoib_sendq_size * sizeof *p->tx_ring);
 
 	p->qp = ipoib_cm_create_tx_qp(p->dev, p);
 	if (IS_ERR(p->qp)) {

include/rdma/ib_verbs.h

@@ -783,6 +783,7 @@ enum ib_qp_create_flags {
 	IB_QP_CREATE_BLOCK_MULTICAST_LOOPBACK	= 1 << 1,
 	IB_QP_CREATE_NETIF_QP			= 1 << 5,
 	IB_QP_CREATE_SIGNATURE_EN		= 1 << 6,
+	IB_QP_CREATE_USE_GFP_NOIO		= 1 << 7,
 	/* reserve bits 26-31 for low level drivers' internal use */
 	IB_QP_CREATE_RESERVED_START		= 1 << 26,
 	IB_QP_CREATE_RESERVED_END		= 1 << 31,