net/sunrpc/xprtrdma/fmr_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 Memory Regions (FMR).
 * Referred to sometimes as MTHCAFMR mode.
 *
 * FMR uses synchronous memory registration and deregistration.
 * FMR registration is known to be fast, but FMR deregistration
 * can take tens of usecs to complete.
 */

/* Normal operation
 *
 * A Memory Region is prepared for RDMA READ or WRITE using the
 * ib_map_phys_fmr verb (fmr_op_map). When the RDMA operation is
 * finished, the Memory Region is unmapped using the ib_unmap_fmr
 * verb (fmr_op_unmap).
 */

#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

/* Maximum scatter/gather per FMR */
#define RPCRDMA_MAX_FMR_SGES	(64)

/* Access mode of externally registered pages */
enum {
	RPCRDMA_FMR_ACCESS_FLAGS	= IB_ACCESS_REMOTE_WRITE |
					  IB_ACCESS_REMOTE_READ,
};

bool
fmr_is_supported(struct rpcrdma_ia *ia)
{
	if (!ia->ri_device->alloc_fmr) {
		pr_info("rpcrdma: 'fmr' mode is not supported by device %s\n",
			ia->ri_device->name);
		return false;
	}
	return true;
}

static int
fmr_op_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mr *mr)
{
	static struct ib_fmr_attr fmr_attr = {
		.max_pages	= RPCRDMA_MAX_FMR_SGES,
		.max_maps	= 1,
		.page_shift	= PAGE_SHIFT
	};

	mr->fmr.fm_physaddrs = kcalloc(RPCRDMA_MAX_FMR_SGES,
				       sizeof(u64), GFP_KERNEL);
	if (!mr->fmr.fm_physaddrs)
		goto out_free;

	mr->mr_sg = kcalloc(RPCRDMA_MAX_FMR_SGES,
			    sizeof(*mr->mr_sg), GFP_KERNEL);
	if (!mr->mr_sg)
		goto out_free;

	sg_init_table(mr->mr_sg, RPCRDMA_MAX_FMR_SGES);

	mr->fmr.fm_mr = ib_alloc_fmr(ia->ri_pd, RPCRDMA_FMR_ACCESS_FLAGS,
				     &fmr_attr);
	if (IS_ERR(mr->fmr.fm_mr))
		goto out_fmr_err;

	INIT_LIST_HEAD(&mr->mr_list);
	return 0;

out_fmr_err:
	dprintk("RPC:       %s: ib_alloc_fmr returned %ld\n", __func__,
		PTR_ERR(mr->fmr.fm_mr));

out_free:
	kfree(mr->mr_sg);
	kfree(mr->fmr.fm_physaddrs);
	return -ENOMEM;
}

static int
__fmr_unmap(struct rpcrdma_mr *mr)
{
	LIST_HEAD(l);
	int rc;

	list_add(&mr->fmr.fm_mr->list, &l);
	rc = ib_unmap_fmr(&l);
	list_del(&mr->fmr.fm_mr->list);
	return rc;
}

static void
fmr_op_release_mr(struct rpcrdma_mr *mr)
{
	LIST_HEAD(unmap_list);
	int rc;

	kfree(mr->fmr.fm_physaddrs);
	kfree(mr->mr_sg);

	/* In case this one was left mapped, try to unmap it
	 * to prevent dealloc_fmr from failing with EBUSY
	 */
	rc = __fmr_unmap(mr);
	if (rc)
		pr_err("rpcrdma: final ib_unmap_fmr for %p failed %i\n",
		       mr, rc);

	rc = ib_dealloc_fmr(mr->fmr.fm_mr);
	if (rc)
		pr_err("rpcrdma: final ib_dealloc_fmr for %p returned %i\n",
		       mr, rc);

	kfree(mr);
}

/* Reset of a single FMR.
 */
static void
fmr_op_recover_mr(struct rpcrdma_mr *mr)
{
	struct rpcrdma_xprt *r_xprt = mr->mr_xprt;
	int rc;

	/* ORDER: invalidate first */
	rc = __fmr_unmap(mr);
	if (rc)
		goto out_release;

	/* ORDER: then DMA unmap */
	rpcrdma_mr_unmap_and_put(mr);

	r_xprt->rx_stats.mrs_recovered++;
	return;

out_release:
	pr_err("rpcrdma: FMR reset failed (%d), %p released\n", rc, mr);
	r_xprt->rx_stats.mrs_orphaned++;

	trace_xprtrdma_dma_unmap(mr);
	ib_dma_unmap_sg(r_xprt->rx_ia.ri_device,
			mr->mr_sg, mr->mr_nents, mr->mr_dir);

	spin_lock(&r_xprt->rx_buf.rb_mrlock);
	list_del(&mr->mr_all);
	spin_unlock(&r_xprt->rx_buf.rb_mrlock);

	fmr_op_release_mr(mr);
}

/* On success, sets:
 *	ep->rep_attr.cap.max_send_wr
 *	ep->rep_attr.cap.max_recv_wr
 *	cdata->max_requests
 *	ia->ri_max_segs
 */
static int
fmr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
	    struct rpcrdma_create_data_internal *cdata)
{
	int max_qp_wr;

	max_qp_wr = ia->ri_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 (cdata->max_requests > max_qp_wr)
		cdata->max_requests = max_qp_wr;
	ep->rep_attr.cap.max_send_wr = cdata->max_requests;
	ep->rep_attr.cap.max_send_wr += RPCRDMA_BACKWARD_WRS;
	ep->rep_attr.cap.max_send_wr += 1; /* for ib_drain_sq */
	ep->rep_attr.cap.max_recv_wr = cdata->max_requests;
	ep->rep_attr.cap.max_recv_wr += RPCRDMA_BACKWARD_WRS;
	ep->rep_attr.cap.max_recv_wr += 1; /* for ib_drain_rq */

	ia->ri_max_segs = max_t(unsigned int, 1, RPCRDMA_MAX_DATA_SEGS /
				RPCRDMA_MAX_FMR_SGES);
	return 0;
}

/* FMR mode conveys up to 64 pages of payload per chunk segment.
 */
static size_t
fmr_op_maxpages(struct rpcrdma_xprt *r_xprt)
{
	return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
		     RPCRDMA_MAX_HDR_SEGS * RPCRDMA_MAX_FMR_SGES);
}

/* Use the ib_map_phys_fmr() verb to register a memory region
 * for remote access via RDMA READ or RDMA WRITE.
 */
static struct rpcrdma_mr_seg *
fmr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
	   int nsegs, bool writing, struct rpcrdma_mr **out)
{
	struct rpcrdma_mr_seg *seg1 = seg;
	int len, pageoff, i, rc;
	struct rpcrdma_mr *mr;
	u64 *dma_pages;

	mr = rpcrdma_mr_get(r_xprt);
	if (!mr)
		return ERR_PTR(-EAGAIN);

	pageoff = offset_in_page(seg1->mr_offset);
	seg1->mr_offset -= pageoff;	/* start of page */
	seg1->mr_len += pageoff;
	len = -pageoff;
	if (nsegs > RPCRDMA_MAX_FMR_SGES)
		nsegs = RPCRDMA_MAX_FMR_SGES;
	for (i = 0; i < nsegs;) {
		if (seg->mr_page)
			sg_set_page(&mr->mr_sg[i],
				    seg->mr_page,
				    seg->mr_len,
				    offset_in_page(seg->mr_offset));
		else
			sg_set_buf(&mr->mr_sg[i], seg->mr_offset,
				   seg->mr_len);
		len += seg->mr_len;
		++seg;
		++i;
		/* Check for holes */
		if ((i < nsegs && offset_in_page(seg->mr_offset)) ||
		    offset_in_page((seg-1)->mr_offset + (seg-1)->mr_len))
			break;
	}
	mr->mr_dir = rpcrdma_data_dir(writing);

	mr->mr_nents = ib_dma_map_sg(r_xprt->rx_ia.ri_device,
				     mr->mr_sg, i, mr->mr_dir);
	if (!mr->mr_nents)
		goto out_dmamap_err;
	trace_xprtrdma_dma_map(mr);

	for (i = 0, dma_pages = mr->fmr.fm_physaddrs; i < mr->mr_nents; i++)
		dma_pages[i] = sg_dma_address(&mr->mr_sg[i]);
	rc = ib_map_phys_fmr(mr->fmr.fm_mr, dma_pages, mr->mr_nents,
			     dma_pages[0]);
	if (rc)
		goto out_maperr;

	mr->mr_handle = mr->fmr.fm_mr->rkey;
	mr->mr_length = len;
	mr->mr_offset = dma_pages[0] + pageoff;

	*out = mr;
	return seg;

out_dmamap_err:
	pr_err("rpcrdma: failed to DMA map sg %p sg_nents %d\n",
	       mr->mr_sg, i);
	rpcrdma_mr_put(mr);
	return ERR_PTR(-EIO);

out_maperr:
	pr_err("rpcrdma: ib_map_phys_fmr %u@0x%llx+%i (%d) status %i\n",
	       len, (unsigned long long)dma_pages[0],
	       pageoff, mr->mr_nents, rc);
	rpcrdma_mr_unmap_and_put(mr);
	return ERR_PTR(-EIO);
}

/* Post Send WR containing the RPC Call message.
 */
static int
fmr_op_send(struct rpcrdma_ia *ia, struct rpcrdma_req *req)
{
	return ib_post_send(ia->ri_id->qp, &req->rl_sendctx->sc_wr, NULL);
}

/* Invalidate all memory regions that were registered for "req".
 *
 * Sleeps until it is safe for the host CPU to access the
 * previously mapped memory regions.
 *
 * Caller ensures that @mrs is not empty before the call. This
 * function empties the list.
 */
static void
fmr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct list_head *mrs)
{
	struct rpcrdma_mr *mr;
	LIST_HEAD(unmap_list);
	int rc;

	/* ORDER: Invalidate all of the req's MRs first
	 *
	 * ib_unmap_fmr() is slow, so use a single call instead
	 * of one call per mapped FMR.
	 */
	list_for_each_entry(mr, mrs, mr_list) {
		dprintk("RPC:       %s: unmapping fmr %p\n",
			__func__, &mr->fmr);
		trace_xprtrdma_localinv(mr);
		list_add_tail(&mr->fmr.fm_mr->list, &unmap_list);
	}
	r_xprt->rx_stats.local_inv_needed++;
	rc = ib_unmap_fmr(&unmap_list);
	if (rc)
		goto out_reset;

	/* ORDER: Now DMA unmap all of the req's MRs, and return
	 * them to the free MW list.
	 */
	while (!list_empty(mrs)) {
		mr = rpcrdma_mr_pop(mrs);
		list_del(&mr->fmr.fm_mr->list);
		rpcrdma_mr_unmap_and_put(mr);
	}

	return;

out_reset:
	pr_err("rpcrdma: ib_unmap_fmr failed (%i)\n", rc);

	while (!list_empty(mrs)) {
		mr = rpcrdma_mr_pop(mrs);
		list_del(&mr->fmr.fm_mr->list);
		fmr_op_recover_mr(mr);
	}
}

const struct rpcrdma_memreg_ops rpcrdma_fmr_memreg_ops = {
	.ro_map				= fmr_op_map,
	.ro_send			= fmr_op_send,
	.ro_unmap_sync			= fmr_op_unmap_sync,
	.ro_recover_mr			= fmr_op_recover_mr,
	.ro_open			= fmr_op_open,
	.ro_maxpages			= fmr_op_maxpages,
	.ro_init_mr			= fmr_op_init_mr,
	.ro_release_mr			= fmr_op_release_mr,
	.ro_displayname			= "fmr",
	.ro_send_w_inv_ok		= 0,
};