net/sunrpc/xprtrdma/frwr_ops.c - kernel/msm-4.19 - Gitiles

 /*
  * Copyright (c) 2015 Oracle.  All rights reserved.
  * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
  */

 /* Lightweight memory registration using Fast Registration Work
  * Requests (FRWR). Also referred to sometimes as FRMR mode.
  *
  * FRWR features ordered asynchronous registration and deregistration
  * 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 (frmr_op_map). When the RDMA operation is finished, this
  * Memory Region is invalidated using a LOCAL_INV Work Request
  * (frmr_op_unmap).
  *
  * Typically these 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.
  *
  * As an optimization, frwr_op_unmap marks MRs INVALID before the
  * LOCAL_INV WR is posted. If posting succeeds, the MR is placed on
  * rb_mws immediately so that no work (like managing a linked list
  * under a spinlock) is needed in the completion upcall.
  *
  * But this means that frwr_op_map() can occasionally encounter an MR
  * that is INVALID but the LOCAL_INV WR has not completed. Work Queue
  * ordering prevents a subsequent FAST_REG WR from executing against
  * that MR while it is still being invalidated.
  */

 /* Transport recovery
  *
  * ->op_map and the transport connect worker cannot run at the same
  * time, but ->op_unmap can fire while the transport connect worker
  * is running. Thus MR recovery is handled in ->op_map, to guarantee
  * that recovered MRs are owned by a sending RPC, and not one where
  * ->op_unmap could fire at the same time transport reconnect is
  * being done.
  *
  * When the underlying transport disconnects, MRs are left in one of
  * three states:
  *
  * INVALID:	The MR was not in use before the QP entered ERROR state.
  *		(Or, the LOCAL_INV WR has not completed or flushed yet).
  *
  * STALE:	The MR was being registered or unregistered when the QP
  *		entered ERROR state, and the pending WR was flushed.
  *
  * VALID:	The MR was registered before the QP entered ERROR state.
  *
  * When frwr_op_map encounters STALE and VALID MRs, they are recovered
  * with ib_dereg_mr and then are re-initialized. Beause MR recovery
  * allocates fresh resources, it is deferred to a workqueue, and the
  * recovered MRs are placed back on the rb_mws list when recovery is
  * complete. frwr_op_map allocates another MR for the current RPC while
  * the broken MR is reset.
  *
  * To ensure that frwr_op_map doesn't encounter an MR that is marked
  * INVALID but that is about to be flushed due to a previous transport
  * disconnect, the transport connect worker attempts to drain all
  * pending send queue WRs before the transport is reconnected.
  */

 #include <linux/sunrpc/rpc_rdma.h>

 #include "xprt_rdma.h"

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

 bool
 frwr_is_supported(struct rpcrdma_ia *ia)
 {
 	struct ib_device_attr *attrs = &ia->ri_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",
 		ia->ri_device->name);
 	return false;
 }

 static int
 frwr_op_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mw *r)
 {
 	unsigned int depth = ia->ri_max_frmr_depth;
 	struct rpcrdma_frmr *f = &r->frmr;
 	int rc;

 	f->fr_mr = ib_alloc_mr(ia->ri_pd, IB_MR_TYPE_MEM_REG, depth);
 	if (IS_ERR(f->fr_mr))
 		goto out_mr_err;

 	r->mw_sg = kcalloc(depth, sizeof(*r->mw_sg), GFP_KERNEL);
 	if (!r->mw_sg)
 		goto out_list_err;

 	sg_init_table(r->mw_sg, depth);
 	init_completion(&f->fr_linv_done);
 	return 0;

 out_mr_err:
 	rc = PTR_ERR(f->fr_mr);
 	dprintk("RPC:       %s: ib_alloc_mr status %i\n",
 		__func__, rc);
 	return rc;

 out_list_err:
 	rc = -ENOMEM;
 	dprintk("RPC:       %s: sg allocation failure\n",
 		__func__);
 	ib_dereg_mr(f->fr_mr);
 	return rc;
 }

 static void
 frwr_op_release_mr(struct rpcrdma_mw *r)
 {
 	int rc;

 	/* Ensure MW is not on any rl_registered list */
 	if (!list_empty(&r->mw_list))
 		list_del(&r->mw_list);

 	rc = ib_dereg_mr(r->frmr.fr_mr);
 	if (rc)
 		pr_err("rpcrdma: final ib_dereg_mr for %p returned %i\n",
 		       r, rc);
 	kfree(r->mw_sg);
 	kfree(r);
 }

 static int
 __frwr_reset_mr(struct rpcrdma_ia *ia, struct rpcrdma_mw *r)
 {
 	struct rpcrdma_frmr *f = &r->frmr;
 	int rc;

 	rc = ib_dereg_mr(f->fr_mr);
 	if (rc) {
 		pr_warn("rpcrdma: ib_dereg_mr status %d, frwr %p orphaned\n",
 			rc, r);
 		return rc;
 	}

 	f->fr_mr = ib_alloc_mr(ia->ri_pd, IB_MR_TYPE_MEM_REG,
 			       ia->ri_max_frmr_depth);
 	if (IS_ERR(f->fr_mr)) {
 		pr_warn("rpcrdma: ib_alloc_mr status %ld, frwr %p orphaned\n",
 			PTR_ERR(f->fr_mr), r);
 		return PTR_ERR(f->fr_mr);
 	}

 	dprintk("RPC:       %s: recovered FRMR %p\n", __func__, f);
 	f->fr_state = FRMR_IS_INVALID;
 	return 0;
 }

 /* Reset of a single FRMR. Generate a fresh rkey by replacing the MR.
  *
  * There's no recovery if this fails. The FRMR is abandoned, but
  * remains in rb_all. It will be cleaned up when the transport is
  * destroyed.
  */
 static void
 frwr_op_recover_mr(struct rpcrdma_mw *mw)
 {
 	struct rpcrdma_xprt *r_xprt = mw->mw_xprt;
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
 	int rc;

 	rc = __frwr_reset_mr(ia, mw);
 	ib_dma_unmap_sg(ia->ri_device, mw->mw_sg, mw->mw_nents, mw->mw_dir);
 	if (rc)
 		goto out_release;

 	rpcrdma_put_mw(r_xprt, mw);
 	r_xprt->rx_stats.mrs_recovered++;
 	return;

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

 	spin_lock(&r_xprt->rx_buf.rb_mwlock);
 	list_del(&mw->mw_all);
 	spin_unlock(&r_xprt->rx_buf.rb_mwlock);

 	frwr_op_release_mr(mw);
 }

 static int
 frwr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
 	     struct rpcrdma_create_data_internal *cdata)
 {
 	int depth, delta;

 	ia->ri_max_frmr_depth =
 			min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
 			      ia->ri_device->attrs.max_fast_reg_page_list_len);
 	dprintk("RPC:       %s: device's max FR page list len = %u\n",
 		__func__, ia->ri_max_frmr_depth);

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

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

 	ep->rep_attr.cap.max_send_wr *= depth;
 	if (ep->rep_attr.cap.max_send_wr > ia->ri_device->attrs.max_qp_wr) {
 		cdata->max_requests = ia->ri_device->attrs.max_qp_wr / depth;
 		if (!cdata->max_requests)
 			return -EINVAL;
 		ep->rep_attr.cap.max_send_wr = cdata->max_requests *
 					       depth;
 	}

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

 /* FRWR mode conveys a list of pages per chunk segment. The
  * maximum length of that list is the FRWR page list depth.
  */
 static size_t
 frwr_op_maxpages(struct rpcrdma_xprt *r_xprt)
 {
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;

 	return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
 		     RPCRDMA_MAX_HDR_SEGS * ia->ri_max_frmr_depth);
 }

 static void
 __frwr_sendcompletion_flush(struct ib_wc *wc, struct rpcrdma_frmr *frmr,
 			    const char *wr)
 {
 	frmr->fr_state = FRMR_IS_STALE;
 	if (wc->status != IB_WC_WR_FLUSH_ERR)
 		pr_err("rpcrdma: %s: %s (%u/0x%x)\n",
 		       wr, ib_wc_status_msg(wc->status),
 		       wc->status, wc->vendor_err);
 }

 /**
  * frwr_wc_fastreg - Invoked by RDMA provider for each polled FastReg WC
  * @cq:	completion queue (ignored)
  * @wc:	completed WR
  *
  */
 static void
 frwr_wc_fastreg(struct ib_cq *cq, struct ib_wc *wc)
 {
 	struct rpcrdma_frmr *frmr;
 	struct ib_cqe *cqe;

 	/* WARNING: Only wr_cqe and status are reliable at this point */
 	if (wc->status != IB_WC_SUCCESS) {
 		cqe = wc->wr_cqe;
 		frmr = container_of(cqe, struct rpcrdma_frmr, fr_cqe);
 		__frwr_sendcompletion_flush(wc, frmr, "fastreg");
 	}
 }

 /**
  * frwr_wc_localinv - Invoked by RDMA provider for each polled LocalInv WC
  * @cq:	completion queue (ignored)
  * @wc:	completed WR
  *
  */
 static void
 frwr_wc_localinv(struct ib_cq *cq, struct ib_wc *wc)
 {
 	struct rpcrdma_frmr *frmr;
 	struct ib_cqe *cqe;

 	/* WARNING: Only wr_cqe and status are reliable at this point */
 	if (wc->status != IB_WC_SUCCESS) {
 		cqe = wc->wr_cqe;
 		frmr = container_of(cqe, struct rpcrdma_frmr, fr_cqe);
 		__frwr_sendcompletion_flush(wc, frmr, "localinv");
 	}
 }

 /**
  * frwr_wc_localinv - Invoked by RDMA provider for each polled LocalInv WC
  * @cq:	completion queue (ignored)
  * @wc:	completed WR
  *
  * Awaken anyone waiting for an MR to finish being fenced.
  */
 static void
 frwr_wc_localinv_wake(struct ib_cq *cq, struct ib_wc *wc)
 {
 	struct rpcrdma_frmr *frmr;
 	struct ib_cqe *cqe;

 	/* WARNING: Only wr_cqe and status are reliable at this point */
 	cqe = wc->wr_cqe;
 	frmr = container_of(cqe, struct rpcrdma_frmr, fr_cqe);
 	if (wc->status != IB_WC_SUCCESS)
 		__frwr_sendcompletion_flush(wc, frmr, "localinv");
 	complete(&frmr->fr_linv_done);
 }

 /* Post a REG_MR Work Request to register a memory region
  * for remote access via RDMA READ or RDMA WRITE.
  */
 static int
 frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 	    int nsegs, bool writing, struct rpcrdma_mw **out)
 {
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
 	struct rpcrdma_mw *mw;
 	struct rpcrdma_frmr *frmr;
 	struct ib_mr *mr;
 	struct ib_reg_wr *reg_wr;
 	struct ib_send_wr *bad_wr;
 	int rc, i, n, dma_nents;
 	u8 key;

 	mw = NULL;
 	do {
 		if (mw)
 			rpcrdma_defer_mr_recovery(mw);
 		mw = rpcrdma_get_mw(r_xprt);
 		if (!mw)
 			return -ENOBUFS;
 	} while (mw->frmr.fr_state != FRMR_IS_INVALID);
 	frmr = &mw->frmr;
 	frmr->fr_state = FRMR_IS_VALID;
 	mr = frmr->fr_mr;
 	reg_wr = &frmr->fr_regwr;

 	if (nsegs > ia->ri_max_frmr_depth)
 		nsegs = ia->ri_max_frmr_depth;
 	for (i = 0; i < nsegs;) {
 		if (seg->mr_page)
 			sg_set_page(&mw->mw_sg[i],
 				    seg->mr_page,
 				    seg->mr_len,
 				    offset_in_page(seg->mr_offset));
 		else
 			sg_set_buf(&mw->mw_sg[i], seg->mr_offset,
 				   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;
 	}
 	mw->mw_nents = i;
 	mw->mw_dir = rpcrdma_data_dir(writing);
 	if (i == 0)
 		goto out_dmamap_err;

 	dma_nents = ib_dma_map_sg(ia->ri_device,
 				  mw->mw_sg, mw->mw_nents, mw->mw_dir);
 	if (!dma_nents)
 		goto out_dmamap_err;

 	n = ib_map_mr_sg(mr, mw->mw_sg, mw->mw_nents, NULL, PAGE_SIZE);
 	if (unlikely(n != mw->mw_nents))
 		goto out_mapmr_err;

 	dprintk("RPC:       %s: Using frmr %p to map %u segments (%u bytes)\n",
 		__func__, frmr, mw->mw_nents, mr->length);

 	key = (u8)(mr->rkey & 0x000000FF);
 	ib_update_fast_reg_key(mr, ++key);

 	reg_wr->wr.next = NULL;
 	reg_wr->wr.opcode = IB_WR_REG_MR;
 	frmr->fr_cqe.done = frwr_wc_fastreg;
 	reg_wr->wr.wr_cqe = &frmr->fr_cqe;
 	reg_wr->wr.num_sge = 0;
 	reg_wr->wr.send_flags = 0;
 	reg_wr->mr = mr;
 	reg_wr->key = mr->rkey;
 	reg_wr->access = writing ?
 			 IB_ACCESS_REMOTE_WRITE | IB_ACCESS_LOCAL_WRITE :
 			 IB_ACCESS_REMOTE_READ;

 	DECR_CQCOUNT(&r_xprt->rx_ep);
 	rc = ib_post_send(ia->ri_id->qp, &reg_wr->wr, &bad_wr);
 	if (rc)
 		goto out_senderr;

 	mw->mw_handle = mr->rkey;
 	mw->mw_length = mr->length;
 	mw->mw_offset = mr->iova;

 	*out = mw;
 	return mw->mw_nents;

 out_dmamap_err:
 	pr_err("rpcrdma: failed to dma map sg %p sg_nents %u\n",
 	       mw->mw_sg, mw->mw_nents);
 	rpcrdma_defer_mr_recovery(mw);
 	return -EIO;

 out_mapmr_err:
 	pr_err("rpcrdma: failed to map mr %p (%u/%u)\n",
 	       frmr->fr_mr, n, mw->mw_nents);
 	rpcrdma_defer_mr_recovery(mw);
 	return -EIO;

 out_senderr:
 	pr_err("rpcrdma: FRMR registration ib_post_send returned %i\n", rc);
 	rpcrdma_defer_mr_recovery(mw);
 	return -ENOTCONN;
 }

 static struct ib_send_wr *
 __frwr_prepare_linv_wr(struct rpcrdma_mw *mw)
 {
 	struct rpcrdma_frmr *f = &mw->frmr;
 	struct ib_send_wr *invalidate_wr;

 	dprintk("RPC:       %s: invalidating frmr %p\n", __func__, f);

 	f->fr_state = FRMR_IS_INVALID;
 	invalidate_wr = &f->fr_invwr;

 	memset(invalidate_wr, 0, sizeof(*invalidate_wr));
 	f->fr_cqe.done = frwr_wc_localinv;
 	invalidate_wr->wr_cqe = &f->fr_cqe;
 	invalidate_wr->opcode = IB_WR_LOCAL_INV;
 	invalidate_wr->ex.invalidate_rkey = f->fr_mr->rkey;

 	return invalidate_wr;
 }

 /* 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 req->rl_registered is not empty.
  */
 static void
 frwr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 {
 	struct ib_send_wr *invalidate_wrs, *pos, *prev, *bad_wr;
 	struct rpcrdma_rep *rep = req->rl_reply;
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
 	struct rpcrdma_mw *mw, *tmp;
 	struct rpcrdma_frmr *f;
 	int rc;

 	dprintk("RPC:       %s: req %p\n", __func__, req);

 	/* ORDER: Invalidate all of the req's MRs first
 	 *
 	 * Chain the LOCAL_INV Work Requests and post them with
 	 * a single ib_post_send() call.
 	 */
 	f = NULL;
 	invalidate_wrs = pos = prev = NULL;
 	list_for_each_entry(mw, &req->rl_registered, mw_list) {
 		if ((rep->rr_wc_flags & IB_WC_WITH_INVALIDATE) &&
 		    (mw->mw_handle == rep->rr_inv_rkey)) {
 			mw->frmr.fr_state = FRMR_IS_INVALID;
 			continue;
 		}

 		pos = __frwr_prepare_linv_wr(mw);

 		if (!invalidate_wrs)
 			invalidate_wrs = pos;
 		else
 			prev->next = pos;
 		prev = pos;
 		f = &mw->frmr;
 	}
 	if (!f)
 		goto unmap;

 	/* Strong send queue ordering guarantees that when the
 	 * last WR in the chain completes, all WRs in the chain
 	 * are complete.
 	 */
 	f->fr_invwr.send_flags = IB_SEND_SIGNALED;
 	f->fr_cqe.done = frwr_wc_localinv_wake;
 	reinit_completion(&f->fr_linv_done);
 	INIT_CQCOUNT(&r_xprt->rx_ep);

 	/* Transport disconnect drains the receive CQ before it
 	 * replaces the QP. The RPC reply handler won't call us
 	 * unless ri_id->qp is a valid pointer.
 	 */
 	r_xprt->rx_stats.local_inv_needed++;
 	rc = ib_post_send(ia->ri_id->qp, invalidate_wrs, &bad_wr);
 	if (rc)
 		goto reset_mrs;

 	wait_for_completion(&f->fr_linv_done);

 	/* ORDER: Now DMA unmap all of the req's MRs, and return
 	 * them to the free MW list.
 	 */
 unmap:
 	list_for_each_entry_safe(mw, tmp, &req->rl_registered, mw_list) {
 		dprintk("RPC:       %s: unmapping frmr %p\n",
 			__func__, &mw->frmr);
 		list_del_init(&mw->mw_list);
 		ib_dma_unmap_sg(ia->ri_device,
 				mw->mw_sg, mw->mw_nents, mw->mw_dir);
 		rpcrdma_put_mw(r_xprt, mw);
 	}
 	return;

 reset_mrs:
 	pr_err("rpcrdma: FRMR invalidate ib_post_send returned %i\n", rc);
 	rdma_disconnect(ia->ri_id);

 	/* Find and reset the MRs in the LOCAL_INV WRs that did not
 	 * get posted. This is synchronous, and slow.
 	 */
 	list_for_each_entry(mw, &req->rl_registered, mw_list) {
 		f = &mw->frmr;
 		if (mw->frmr.fr_mr->rkey == bad_wr->ex.invalidate_rkey) {
 			__frwr_reset_mr(ia, mw);
 			bad_wr = bad_wr->next;
 		}
 	}
 	goto unmap;
 }

 /* Use a slow, safe mechanism to invalidate all memory regions
  * that were registered for "req".
  */
 static void
 frwr_op_unmap_safe(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 		   bool sync)
 {
 	struct rpcrdma_mw *mw;

 	while (!list_empty(&req->rl_registered)) {
 		mw = list_first_entry(&req->rl_registered,
 				      struct rpcrdma_mw, mw_list);
 		list_del_init(&mw->mw_list);

 		if (sync)
 			frwr_op_recover_mr(mw);
 		else
 			rpcrdma_defer_mr_recovery(mw);
 	}
 }

 const struct rpcrdma_memreg_ops rpcrdma_frwr_memreg_ops = {
 	.ro_map				= frwr_op_map,
 	.ro_unmap_sync			= frwr_op_unmap_sync,
 	.ro_unmap_safe			= frwr_op_unmap_safe,
 	.ro_recover_mr			= frwr_op_recover_mr,
 	.ro_open			= frwr_op_open,
 	.ro_maxpages			= frwr_op_maxpages,
 	.ro_init_mr			= frwr_op_init_mr,
 	.ro_release_mr			= frwr_op_release_mr,
 	.ro_displayname			= "frwr",
 	.ro_send_w_inv_ok		= RPCRDMA_CMP_F_SND_W_INV_OK,
 };
	/*
	* Copyright (c) 2015 Oracle. All rights reserved.
	* Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
	*/

	/* Lightweight memory registration using Fast Registration Work
	* Requests (FRWR). Also referred to sometimes as FRMR mode.
	*
	* FRWR features ordered asynchronous registration and deregistration
	* 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 (frmr_op_map). When the RDMA operation is finished, this
	* Memory Region is invalidated using a LOCAL_INV Work Request
	* (frmr_op_unmap).
	*
	* Typically these 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.
	*
	* As an optimization, frwr_op_unmap marks MRs INVALID before the
	* LOCAL_INV WR is posted. If posting succeeds, the MR is placed on
	* rb_mws immediately so that no work (like managing a linked list
	* under a spinlock) is needed in the completion upcall.
	*
	* But this means that frwr_op_map() can occasionally encounter an MR
	* that is INVALID but the LOCAL_INV WR has not completed. Work Queue
	* ordering prevents a subsequent FAST_REG WR from executing against
	* that MR while it is still being invalidated.
	*/

	/* Transport recovery
	*
	* ->op_map and the transport connect worker cannot run at the same
	* time, but ->op_unmap can fire while the transport connect worker
	* is running. Thus MR recovery is handled in ->op_map, to guarantee
	* that recovered MRs are owned by a sending RPC, and not one where
	* ->op_unmap could fire at the same time transport reconnect is
	* being done.
	*
	* When the underlying transport disconnects, MRs are left in one of
	* three states:
	*
	* INVALID: The MR was not in use before the QP entered ERROR state.
	* (Or, the LOCAL_INV WR has not completed or flushed yet).
	*
	* STALE: The MR was being registered or unregistered when the QP
	* entered ERROR state, and the pending WR was flushed.
	*
	* VALID: The MR was registered before the QP entered ERROR state.
	*
	* When frwr_op_map encounters STALE and VALID MRs, they are recovered
	* with ib_dereg_mr and then are re-initialized. Beause MR recovery
	* allocates fresh resources, it is deferred to a workqueue, and the
	* recovered MRs are placed back on the rb_mws list when recovery is
	* complete. frwr_op_map allocates another MR for the current RPC while
	* the broken MR is reset.
	*
	* To ensure that frwr_op_map doesn't encounter an MR that is marked
	* INVALID but that is about to be flushed due to a previous transport
	* disconnect, the transport connect worker attempts to drain all
	* pending send queue WRs before the transport is reconnected.
	*/

	#include <linux/sunrpc/rpc_rdma.h>

	#include "xprt_rdma.h"

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

	bool
	frwr_is_supported(struct rpcrdma_ia *ia)
	{
	struct ib_device_attr *attrs = &ia->ri_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",
	ia->ri_device->name);
	return false;
	}

	static int
	frwr_op_init_mr(struct rpcrdma_ia ia, struct rpcrdma_mw r)
	{
	unsigned int depth = ia->ri_max_frmr_depth;
	struct rpcrdma_frmr *f = &r->frmr;
	int rc;

	f->fr_mr = ib_alloc_mr(ia->ri_pd, IB_MR_TYPE_MEM_REG, depth);
	if (IS_ERR(f->fr_mr))
	goto out_mr_err;

	r->mw_sg = kcalloc(depth, sizeof(*r->mw_sg), GFP_KERNEL);
	if (!r->mw_sg)
	goto out_list_err;

	sg_init_table(r->mw_sg, depth);
	init_completion(&f->fr_linv_done);
	return 0;

	out_mr_err:
	rc = PTR_ERR(f->fr_mr);
	dprintk("RPC: %s: ib_alloc_mr status %i\n",
	__func__, rc);
	return rc;

	out_list_err:
	rc = -ENOMEM;
	dprintk("RPC: %s: sg allocation failure\n",
	__func__);
	ib_dereg_mr(f->fr_mr);
	return rc;
	}

	static void
	frwr_op_release_mr(struct rpcrdma_mw *r)
	{
	int rc;

	/* Ensure MW is not on any rl_registered list */
	if (!list_empty(&r->mw_list))
	list_del(&r->mw_list);

	rc = ib_dereg_mr(r->frmr.fr_mr);
	if (rc)
	pr_err("rpcrdma: final ib_dereg_mr for %p returned %i\n",
	r, rc);
	kfree(r->mw_sg);
	kfree(r);
	}

	static int
	__frwr_reset_mr(struct rpcrdma_ia ia, struct rpcrdma_mw r)
	{
	struct rpcrdma_frmr *f = &r->frmr;
	int rc;

	rc = ib_dereg_mr(f->fr_mr);
	if (rc) {
	pr_warn("rpcrdma: ib_dereg_mr status %d, frwr %p orphaned\n",
	rc, r);
	return rc;
	}

	f->fr_mr = ib_alloc_mr(ia->ri_pd, IB_MR_TYPE_MEM_REG,
	ia->ri_max_frmr_depth);
	if (IS_ERR(f->fr_mr)) {
	pr_warn("rpcrdma: ib_alloc_mr status %ld, frwr %p orphaned\n",
	PTR_ERR(f->fr_mr), r);
	return PTR_ERR(f->fr_mr);
	}

	dprintk("RPC: %s: recovered FRMR %p\n", __func__, f);
	f->fr_state = FRMR_IS_INVALID;
	return 0;
	}

	/* Reset of a single FRMR. Generate a fresh rkey by replacing the MR.
	*
	* There's no recovery if this fails. The FRMR is abandoned, but
	* remains in rb_all. It will be cleaned up when the transport is
	* destroyed.
	*/
	static void
	frwr_op_recover_mr(struct rpcrdma_mw *mw)
	{
	struct rpcrdma_xprt *r_xprt = mw->mw_xprt;
	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
	int rc;

	rc = __frwr_reset_mr(ia, mw);
	ib_dma_unmap_sg(ia->ri_device, mw->mw_sg, mw->mw_nents, mw->mw_dir);
	if (rc)
	goto out_release;

	rpcrdma_put_mw(r_xprt, mw);
	r_xprt->rx_stats.mrs_recovered++;
	return;

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

	spin_lock(&r_xprt->rx_buf.rb_mwlock);
	list_del(&mw->mw_all);
	spin_unlock(&r_xprt->rx_buf.rb_mwlock);

	frwr_op_release_mr(mw);
	}

	static int
	frwr_op_open(struct rpcrdma_ia ia, struct rpcrdma_ep ep,
	struct rpcrdma_create_data_internal *cdata)
	{
	int depth, delta;

	ia->ri_max_frmr_depth =
	min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
	ia->ri_device->attrs.max_fast_reg_page_list_len);
	dprintk("RPC: %s: device's max FR page list len = %u\n",
	__func__, ia->ri_max_frmr_depth);

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

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

	ep->rep_attr.cap.max_send_wr *= depth;
	if (ep->rep_attr.cap.max_send_wr > ia->ri_device->attrs.max_qp_wr) {
	cdata->max_requests = ia->ri_device->attrs.max_qp_wr / depth;
	if (!cdata->max_requests)
	return -EINVAL;
	ep->rep_attr.cap.max_send_wr = cdata->max_requests *
	depth;
	}

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

	/* FRWR mode conveys a list of pages per chunk segment. The
	* maximum length of that list is the FRWR page list depth.
	*/
	static size_t
	frwr_op_maxpages(struct rpcrdma_xprt *r_xprt)
	{
	struct rpcrdma_ia *ia = &r_xprt->rx_ia;

	return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
	RPCRDMA_MAX_HDR_SEGS * ia->ri_max_frmr_depth);
	}

	static void
	__frwr_sendcompletion_flush(struct ib_wc wc, struct rpcrdma_frmr frmr,
	const char *wr)
	{
	frmr->fr_state = FRMR_IS_STALE;
	if (wc->status != IB_WC_WR_FLUSH_ERR)
	pr_err("rpcrdma: %s: %s (%u/0x%x)\n",
	wr, ib_wc_status_msg(wc->status),
	wc->status, wc->vendor_err);
	}

	/**
	* frwr_wc_fastreg - Invoked by RDMA provider for each polled FastReg WC
	* @cq: completion queue (ignored)
	* @wc: completed WR
	*
	*/
	static void
	frwr_wc_fastreg(struct ib_cq cq, struct ib_wc wc)
	{
	struct rpcrdma_frmr *frmr;
	struct ib_cqe *cqe;

	/* WARNING: Only wr_cqe and status are reliable at this point */
	if (wc->status != IB_WC_SUCCESS) {
	cqe = wc->wr_cqe;
	frmr = container_of(cqe, struct rpcrdma_frmr, fr_cqe);
	__frwr_sendcompletion_flush(wc, frmr, "fastreg");
	}
	}

	/**
	* frwr_wc_localinv - Invoked by RDMA provider for each polled LocalInv WC
	* @cq: completion queue (ignored)
	* @wc: completed WR
	*
	*/
	static void
	frwr_wc_localinv(struct ib_cq cq, struct ib_wc wc)
	{
	struct rpcrdma_frmr *frmr;
	struct ib_cqe *cqe;

	/* WARNING: Only wr_cqe and status are reliable at this point */
	if (wc->status != IB_WC_SUCCESS) {
	cqe = wc->wr_cqe;
	frmr = container_of(cqe, struct rpcrdma_frmr, fr_cqe);
	__frwr_sendcompletion_flush(wc, frmr, "localinv");
	}
	}

	/**
	* frwr_wc_localinv - Invoked by RDMA provider for each polled LocalInv WC
	* @cq: completion queue (ignored)
	* @wc: completed WR
	*
	* Awaken anyone waiting for an MR to finish being fenced.
	*/
	static void
	frwr_wc_localinv_wake(struct ib_cq cq, struct ib_wc wc)
	{
	struct rpcrdma_frmr *frmr;
	struct ib_cqe *cqe;

	/* WARNING: Only wr_cqe and status are reliable at this point */
	cqe = wc->wr_cqe;
	frmr = container_of(cqe, struct rpcrdma_frmr, fr_cqe);
	if (wc->status != IB_WC_SUCCESS)
	__frwr_sendcompletion_flush(wc, frmr, "localinv");
	complete(&frmr->fr_linv_done);
	}

	/* Post a REG_MR Work Request to register a memory region
	* for remote access via RDMA READ or RDMA WRITE.
	*/
	static int
	frwr_op_map(struct rpcrdma_xprt r_xprt, struct rpcrdma_mr_seg seg,
	int nsegs, bool writing, struct rpcrdma_mw **out)
	{
	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
	struct rpcrdma_mw *mw;
	struct rpcrdma_frmr *frmr;
	struct ib_mr *mr;
	struct ib_reg_wr *reg_wr;
	struct ib_send_wr *bad_wr;
	int rc, i, n, dma_nents;
	u8 key;

	mw = NULL;
	do {
	if (mw)
	rpcrdma_defer_mr_recovery(mw);
	mw = rpcrdma_get_mw(r_xprt);
	if (!mw)
	return -ENOBUFS;
	} while (mw->frmr.fr_state != FRMR_IS_INVALID);
	frmr = &mw->frmr;
	frmr->fr_state = FRMR_IS_VALID;
	mr = frmr->fr_mr;
	reg_wr = &frmr->fr_regwr;

	if (nsegs > ia->ri_max_frmr_depth)
	nsegs = ia->ri_max_frmr_depth;
	for (i = 0; i < nsegs;) {
	if (seg->mr_page)
	sg_set_page(&mw->mw_sg[i],
	seg->mr_page,
	seg->mr_len,
	offset_in_page(seg->mr_offset));
	else
	sg_set_buf(&mw->mw_sg[i], seg->mr_offset,
	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;
	}
	mw->mw_nents = i;
	mw->mw_dir = rpcrdma_data_dir(writing);
	if (i == 0)
	goto out_dmamap_err;

	dma_nents = ib_dma_map_sg(ia->ri_device,
	mw->mw_sg, mw->mw_nents, mw->mw_dir);
	if (!dma_nents)
	goto out_dmamap_err;

	n = ib_map_mr_sg(mr, mw->mw_sg, mw->mw_nents, NULL, PAGE_SIZE);
	if (unlikely(n != mw->mw_nents))
	goto out_mapmr_err;

	dprintk("RPC: %s: Using frmr %p to map %u segments (%u bytes)\n",
	__func__, frmr, mw->mw_nents, mr->length);

	key = (u8)(mr->rkey & 0x000000FF);
	ib_update_fast_reg_key(mr, ++key);

	reg_wr->wr.next = NULL;
	reg_wr->wr.opcode = IB_WR_REG_MR;
	frmr->fr_cqe.done = frwr_wc_fastreg;
	reg_wr->wr.wr_cqe = &frmr->fr_cqe;
	reg_wr->wr.num_sge = 0;
	reg_wr->wr.send_flags = 0;
	reg_wr->mr = mr;
	reg_wr->key = mr->rkey;
	reg_wr->access = writing ?
	IB_ACCESS_REMOTE_WRITE \| IB_ACCESS_LOCAL_WRITE :
	IB_ACCESS_REMOTE_READ;

	DECR_CQCOUNT(&r_xprt->rx_ep);
	rc = ib_post_send(ia->ri_id->qp, &reg_wr->wr, &bad_wr);
	if (rc)
	goto out_senderr;

	mw->mw_handle = mr->rkey;
	mw->mw_length = mr->length;
	mw->mw_offset = mr->iova;

	*out = mw;
	return mw->mw_nents;

	out_dmamap_err:
	pr_err("rpcrdma: failed to dma map sg %p sg_nents %u\n",
	mw->mw_sg, mw->mw_nents);
	rpcrdma_defer_mr_recovery(mw);
	return -EIO;

	out_mapmr_err:
	pr_err("rpcrdma: failed to map mr %p (%u/%u)\n",
	frmr->fr_mr, n, mw->mw_nents);
	rpcrdma_defer_mr_recovery(mw);
	return -EIO;

	out_senderr:
	pr_err("rpcrdma: FRMR registration ib_post_send returned %i\n", rc);
	rpcrdma_defer_mr_recovery(mw);
	return -ENOTCONN;
	}

	static struct ib_send_wr *
	__frwr_prepare_linv_wr(struct rpcrdma_mw *mw)
	{
	struct rpcrdma_frmr *f = &mw->frmr;
	struct ib_send_wr *invalidate_wr;

	dprintk("RPC: %s: invalidating frmr %p\n", __func__, f);

	f->fr_state = FRMR_IS_INVALID;
	invalidate_wr = &f->fr_invwr;

	memset(invalidate_wr, 0, sizeof(*invalidate_wr));
	f->fr_cqe.done = frwr_wc_localinv;
	invalidate_wr->wr_cqe = &f->fr_cqe;
	invalidate_wr->opcode = IB_WR_LOCAL_INV;
	invalidate_wr->ex.invalidate_rkey = f->fr_mr->rkey;

	return invalidate_wr;
	}

	/* 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 req->rl_registered is not empty.
	*/
	static void
	frwr_op_unmap_sync(struct rpcrdma_xprt r_xprt, struct rpcrdma_req req)
	{
	struct ib_send_wr invalidate_wrs, pos, prev, bad_wr;
	struct rpcrdma_rep *rep = req->rl_reply;
	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
	struct rpcrdma_mw mw, tmp;
	struct rpcrdma_frmr *f;
	int rc;

	dprintk("RPC: %s: req %p\n", __func__, req);

	/* ORDER: Invalidate all of the req's MRs first
	*
	* Chain the LOCAL_INV Work Requests and post them with
	* a single ib_post_send() call.
	*/
	f = NULL;
	invalidate_wrs = pos = prev = NULL;
	list_for_each_entry(mw, &req->rl_registered, mw_list) {
	if ((rep->rr_wc_flags & IB_WC_WITH_INVALIDATE) &&
	(mw->mw_handle == rep->rr_inv_rkey)) {
	mw->frmr.fr_state = FRMR_IS_INVALID;
	continue;
	}

	pos = __frwr_prepare_linv_wr(mw);

	if (!invalidate_wrs)
	invalidate_wrs = pos;
	else
	prev->next = pos;
	prev = pos;
	f = &mw->frmr;
	}
	if (!f)
	goto unmap;

	/* Strong send queue ordering guarantees that when the
	* last WR in the chain completes, all WRs in the chain
	* are complete.
	*/
	f->fr_invwr.send_flags = IB_SEND_SIGNALED;
	f->fr_cqe.done = frwr_wc_localinv_wake;
	reinit_completion(&f->fr_linv_done);
	INIT_CQCOUNT(&r_xprt->rx_ep);

	/* Transport disconnect drains the receive CQ before it
	* replaces the QP. The RPC reply handler won't call us
	* unless ri_id->qp is a valid pointer.
	*/
	r_xprt->rx_stats.local_inv_needed++;
	rc = ib_post_send(ia->ri_id->qp, invalidate_wrs, &bad_wr);
	if (rc)
	goto reset_mrs;

	wait_for_completion(&f->fr_linv_done);

	/* ORDER: Now DMA unmap all of the req's MRs, and return
	* them to the free MW list.
	*/
	unmap:
	list_for_each_entry_safe(mw, tmp, &req->rl_registered, mw_list) {
	dprintk("RPC: %s: unmapping frmr %p\n",
	__func__, &mw->frmr);
	list_del_init(&mw->mw_list);
	ib_dma_unmap_sg(ia->ri_device,
	mw->mw_sg, mw->mw_nents, mw->mw_dir);
	rpcrdma_put_mw(r_xprt, mw);
	}
	return;

	reset_mrs:
	pr_err("rpcrdma: FRMR invalidate ib_post_send returned %i\n", rc);
	rdma_disconnect(ia->ri_id);

	/* Find and reset the MRs in the LOCAL_INV WRs that did not
	* get posted. This is synchronous, and slow.
	*/
	list_for_each_entry(mw, &req->rl_registered, mw_list) {
	f = &mw->frmr;
	if (mw->frmr.fr_mr->rkey == bad_wr->ex.invalidate_rkey) {
	__frwr_reset_mr(ia, mw);
	bad_wr = bad_wr->next;
	}
	}
	goto unmap;
	}

	/* Use a slow, safe mechanism to invalidate all memory regions
	* that were registered for "req".
	*/
	static void
	frwr_op_unmap_safe(struct rpcrdma_xprt r_xprt, struct rpcrdma_req req,
	bool sync)
	{
	struct rpcrdma_mw *mw;

	while (!list_empty(&req->rl_registered)) {
	mw = list_first_entry(&req->rl_registered,
	struct rpcrdma_mw, mw_list);
	list_del_init(&mw->mw_list);

	if (sync)
	frwr_op_recover_mr(mw);
	else
	rpcrdma_defer_mr_recovery(mw);
	}
	}

	const struct rpcrdma_memreg_ops rpcrdma_frwr_memreg_ops = {
	.ro_map = frwr_op_map,
	.ro_unmap_sync = frwr_op_unmap_sync,
	.ro_unmap_safe = frwr_op_unmap_safe,
	.ro_recover_mr = frwr_op_recover_mr,
	.ro_open = frwr_op_open,
	.ro_maxpages = frwr_op_maxpages,
	.ro_init_mr = frwr_op_init_mr,
	.ro_release_mr = frwr_op_release_mr,
	.ro_displayname = "frwr",
	.ro_send_w_inv_ok = RPCRDMA_CMP_F_SND_W_INV_OK,
	};