path: root/net/sunrpc/xprtrdma/frwr_ops.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2015, 2017 Oracle.  All rights reserved.
 * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
 */

/* Lightweight memory registration using Fast Registration Work
 * Requests (FRWR).
 *
 * FRWR features ordered asynchronous registration and invalidation
 * of arbitrarily-sized memory regions. This is the fastest and safest
 * but most complex memory registration mode.
 */

/* Normal operation
 *
 * A Memory Region is prepared for RDMA Read or Write using a FAST_REG
 * Work Request (frwr_map). When the RDMA operation is finished, this
 * Memory Region is invalidated using a LOCAL_INV Work Request
 * (frwr_unmap_async and frwr_unmap_sync).
 *
 * Typically FAST_REG Work Requests are not signaled, and neither are
 * RDMA Send Work Requests (with the exception of signaling occasionally
 * to prevent provider work queue overflows). This greatly reduces HCA
 * interrupt workload.
 */

/* Transport recovery
 *
 * frwr_map and frwr_unmap_* cannot run at the same time the transport
 * connect worker is running. The connect worker holds the transport
 * send lock, just as ->send_request does. This prevents frwr_map and
 * the connect worker from running concurrently. When a connection is
 * closed, the Receive completion queue is drained before the allowing
 * the connect worker to get control. This prevents frwr_unmap and the
 * connect worker from running concurrently.
 *
 * When the underlying transport disconnects, MRs that are in flight
 * are flushed and are likely unusable. Thus all flushed MRs are
 * destroyed. New MRs are created on demand.
 */

#include <linux/sunrpc/rpc_rdma.h>
#include <linux/sunrpc/svc_rdma.h>

#include "xprt_rdma.h"
#include <trace/events/rpcrdma.h>

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
# define RPCDBG_FACILITY	RPCDBG_TRANS
#endif

/**
 * frwr_is_supported - Check if device supports FRWR
 * @device: interface adapter to check
 *
 * Returns true if device supports FRWR, otherwise false
 */
bool frwr_is_supported(struct ib_device *device)
{
	struct ib_device_attr *attrs = &device->attrs;

	if (!(attrs->device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS))
		goto out_not_supported;
	if (attrs->max_fast_reg_page_list_len == 0)
		goto out_not_supported;
	return true;

out_not_supported:
	pr_info("rpcrdma: 'frwr' mode is not supported by device %s\n",
		device->name);
	return false;
}

/**
 * frwr_release_mr - Destroy one MR
 * @mr: MR allocated by frwr_init_mr
 *
 */
void frwr_release_mr(struct rpcrdma_mr *mr)
{
	int rc;

	rc = ib_dereg_mr(mr->frwr.fr_mr);
	if (rc)
		trace_xprtrdma_frwr_dereg(mr, rc);
	kfree(mr->mr_sg);
	kfree(mr);
}

static void frwr_mr_recycle(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr *mr)
{
	trace_xprtrdma_mr_recycle(mr);

	if (mr->mr_dir != DMA_NONE) {
		trace_xprtrdma_mr_unmap(mr);
		ib_dma_unmap_sg(r_xprt->rx_ia.ri_id->device,
				mr->mr_sg, mr->mr_nents, mr->mr_dir);
		mr->mr_dir = DMA_NONE;
	}

	spin_lock(&r_xprt->rx_buf.rb_lock);
	list_del(&mr->mr_all);
	r_xprt->rx_stats.mrs_recycled++;
	spin_unlock(&r_xprt->rx_buf.rb_lock);

	frwr_release_mr(mr);
}

/* MRs are dynamically allocated, so simply clean up and release the MR.
 * A replacement MR will subsequently be allocated on demand.
 */
static void
frwr_mr_recycle_worker(struct work_struct *work)
{
	struct rpcrdma_mr *mr = container_of(work, struct rpcrdma_mr,
					     mr_recycle);

	frwr_mr_recycle(mr->mr_xprt, mr);
}

/* frwr_recycle - Discard MRs
 * @req: request to reset
 *
 * Used after a reconnect. These MRs could be in flight, we can't
 * tell. Safe thing to do is release them.
 */
void frwr_recycle(struct rpcrdma_req *req)
{
	struct rpcrdma_mr *mr;

	while ((mr = rpcrdma_mr_pop(&req->rl_registered)))
		frwr_mr_recycle(mr->mr_xprt, mr);
}

/* frwr_reset - Place MRs back on the free list
 * @req: request to reset
 *
 * Used after a failed marshal. For FRWR, this means the MRs
 * don't have to be fully released and recreated.
 *
 * NB: This is safe only as long as none of @req's MRs are
 * involved with an ongoing asynchronous FAST_REG or LOCAL_INV
 * Work Request.
 */
void frwr_reset(struct rpcrdma_req *req)
{
	struct rpcrdma_mr *mr;

	while ((mr = rpcrdma_mr_pop(&req->rl_registered)))
		rpcrdma_mr_put(mr);
}

/**
 * frwr_init_mr - Initialize one MR
 * @ia: interface adapter
 * @mr: generic MR to prepare for FRWR
 *
 * Returns zero if successful. Otherwise a negative errno
 * is returned.
 */
int frwr_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mr *mr)
{
	unsigned int depth = ia->ri_max_frwr_depth;
	struct scatterlist *sg;
	struct ib_mr *frmr;
	int rc;

	/* NB: ib_alloc_mr and device drivers typically allocate
	 *     memory with GFP_KERNEL.
	 */
	frmr = ib_alloc_mr(ia->ri_pd, ia->ri_mrtype, depth);
	if (IS_ERR(frmr))
		goto out_mr_err;

	sg = kcalloc(depth, sizeof(*sg), GFP_NOFS);
	if (!sg)
		goto out_list_err;

	mr->frwr.fr_mr = frmr;
	mr->mr_dir = DMA_NONE;
	INIT_LIST_HEAD(&mr->mr_list);
	INIT_WORK(&mr->mr_recycle, frwr_mr_recycle_worker);
	init_completion(&mr->frwr.fr_linv_done);

	sg_init_table(sg, depth);
	mr->mr_sg = sg;
	return 0;

out_mr_err:
	rc = PTR_ERR(frmr);
	trace_xprtrdma_frwr_alloc(mr, rc);
	return rc;

out_list_err:
	ib_dereg_mr(frmr);
	return -ENOMEM;
}

/**
 * frwr_open - Prepare an endpoint for use with FRWR
 * @ia: interface adapter this endpoint will use
 * @ep: endpoint to prepare
 *
 * On success, sets:
 *	ep->rep_attr.cap.max_send_wr
 *	ep->rep_attr.cap.max_recv_wr
 *	ep->rep_max_requests
 *	ia->ri_max_segs
 *
 * And these FRWR-related fields:
 *	ia->ri_max_frwr_depth
 *	ia->ri_mrtype
 *
 * On failure, a negative errno is returned.
 */
int frwr_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep)
{
	struct ib_device_attr *attrs = &ia->ri_id->device->attrs;
	int max_qp_wr, depth, delta;

	ia->ri_mrtype = IB_MR_TYPE_MEM_REG;
	if (attrs->device_cap_flags & IB_DEVICE_SG_GAPS_REG)
		ia->ri_mrtype = IB_MR_TYPE_SG_GAPS;

	/* Quirk: Some devices advertise a large max_fast_reg_page_list_len
	 * capability, but perform optimally when the MRs are not larger
	 * than a page.
	 */
	if (attrs->max_sge_rd > 1)
		ia->ri_max_frwr_depth = attrs->max_sge_rd;
	else
		ia->ri_max_frwr_depth = attrs->max_fast_reg_page_list_len;
	if (ia->ri_max_frwr_depth > RPCRDMA_MAX_DATA_SEGS)
		ia->ri_max_frwr_depth = RPCRDMA_MAX_DATA_SEGS;
	dprintk("RPC:       %s: max FR page list depth = %u\n",
		__func__, ia->ri_max_frwr_depth);

	/* Add room for frwr register and invalidate WRs.
	 * 1. FRWR reg WR for head
	 * 2. FRWR invalidate WR for head
	 * 3. N FRWR reg WRs for pagelist
	 * 4. N FRWR invalidate WRs for pagelist
	 * 5. FRWR reg WR for tail
	 * 6. FRWR invalidate WR for tail
	 * 7. The RDMA_SEND WR
	 */
	depth = 7;

	/* Calculate N if the device max FRWR depth is smaller than
	 * RPCRDMA_MAX_DATA_SEGS.
	 */
	if (ia->ri_max_frwr_depth < RPCRDMA_MAX_DATA_SEGS) {
		delta = RPCRDMA_MAX_DATA_SEGS - ia->ri_max_frwr_depth;
		do {
			depth += 2; /* FRWR reg + invalidate */
			delta -= ia->ri_max_frwr_depth;
		} while (delta > 0);
	}

	max_qp_wr = ia->ri_id->device->attrs.max_qp_wr;
	max_qp_wr -= RPCRDMA_BACKWARD_WRS;
	max_qp_wr -= 1;
	if (max_qp_wr < RPCRDMA_MIN_SLOT_TABLE)
		return -ENOMEM;
	if (ep->rep_max_requests > max_qp_wr)
		ep->rep_max_requests = max_qp_wr;
	ep->rep_attr.cap.max_send_wr = ep->rep_max_requests * depth;
	if (ep->rep_attr.cap.max_send_wr > max_qp_wr) {
		ep->rep_max_requests = max_qp_wr / depth;
		if (!<