text: // SPDX-License-Identifier: GPL-2.0
  /*
   * 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
   * four states:
   *
   * INVALID:	The MR was not in use before the QP entered ERROR state.
   *
   * VALID:	The MR was registered before the QP entered ERROR state.
   *
   * FLUSHED_FR:	The MR was being registered when the QP entered ERROR
   *		state, and the pending WR was flushed.
   *
   * FLUSHED_LI:	The MR was being invalidated when the QP entered ERROR
   *		state, and the pending WR was flushed.
   *
   * When frwr_op_map encounters FLUSHED and VALID MRs, they are recovered
   * with ib_dereg_mr and then are re-initialized. Because 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, ia->ri_mrtype, 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, ia->ri_mrtype,
  			       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.
   */
  static void
  frwr_op_recover_mr(struct rpcrdma_mw *mw)
  {
  	enum rpcrdma_frmr_state state = mw->frmr.fr_state;
  	struct rpcrdma_xprt *r_xprt = mw->mw_xprt;
  	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
  	int rc;
  
  	rc = __frwr_reset_mr(ia, mw);
  	if (state != FRMR_FLUSHED_LI)
  		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)
  {
  	struct ib_device_attr *attrs = &ia->ri_device->attrs;
  	int 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;
  
  	ia->ri_max_frmr_depth =
  			min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
  			      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 > attrs->max_qp_wr) {
  		cdata->max_requests = 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, const char *wr)
  {
  	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 a flushed 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);
  		frmr->fr_state = FRMR_FLUSHED_FR;
  		__frwr_sendcompletion_flush(wc, "fastreg");
  	}
  }
  
  /**
   * frwr_wc_localinv - Invoked by RDMA provider for a flushed 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);
  		frmr->fr_state = FRMR_FLUSHED_LI;
  		__frwr_sendcompletion_flush(wc, "localinv");
  	}
  }
  
  /**
   * frwr_wc_localinv_wake - Invoked by RDMA provider for a signaled 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) {
  		frmr->fr_state = FRMR_FLUSHED_LI;
  		__frwr_sendcompletion_flush(wc, "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 struct rpcrdma_mr_seg *
  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;
  	bool holes_ok = ia->ri_mrtype == IB_MR_TYPE_SG_GAPS;
  	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;
  	u8 key;
  
  	mw = NULL;
  	do {
  		if (mw)
  			rpcrdma_defer_mr_recovery(mw);
  		mw = rpcrdma_get_mw(r_xprt);
  		if (!mw)
  			return ERR_PTR(-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;
  		if (holes_ok)
  			continue;
  		if ((i < nsegs && offset_in_page(seg->mr_offset)) ||
  		    offset_in_page((seg-1)->mr_offset + (seg-1)->mr_len))
  			break;
  	}
  	mw->mw_dir = rpcrdma_data_dir(writing);
  
  	mw->mw_nents = ib_dma_map_sg(ia->ri_device, mw->mw_sg, i, mw->mw_dir);
  	if (!mw->mw_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 (%llu 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;
  
  	rpcrdma_set_signaled(&r_xprt->rx_ep, &reg_wr->wr);
  	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 seg;
  
  out_dmamap_err:
  	pr_err("rpcrdma: failed to DMA map sg %p sg_nents %d\n",
  	       mw->mw_sg, i);
  	frmr->fr_state = FRMR_IS_INVALID;
  	rpcrdma_put_mw(r_xprt, mw);
  	return ERR_PTR(-EIO);
  
  out_mapmr_err:
  	pr_err("rpcrdma: failed to map mr %p (%d/%d)\n",
  	       frmr->fr_mr, n, mw->mw_nents);
  	rpcrdma_defer_mr_recovery(mw);
  	return ERR_PTR(-EIO);
  
  out_senderr:
  	pr_err("rpcrdma: FRMR registration ib_post_send returned %i\n", rc);
  	rpcrdma_defer_mr_recovery(mw);
  	return ERR_PTR(-ENOTCONN);
  }
  
  /* 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 @mws is not empty before the call. This
   * function empties the list.
   */
  static void
  frwr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct list_head *mws)
  {
  	struct ib_send_wr *first, **prev, *last, *bad_wr;
  	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
  	struct rpcrdma_frmr *f;
  	struct rpcrdma_mw *mw;
  	int count, rc;
  
  	/* ORDER: Invalidate all of the MRs first
  	 *
  	 * Chain the LOCAL_INV Work Requests and post them with
  	 * a single ib_post_send() call.
  	 */
  	f = NULL;
  	count = 0;
  	prev = &first;
  	list_for_each_entry(mw, mws, mw_list) {
  		mw->frmr.fr_state = FRMR_IS_INVALID;
  
  		if (mw->mw_flags & RPCRDMA_MW_F_RI)
  			continue;
  
  		f = &mw->frmr;
  		dprintk("RPC:       %s: invalidating frmr %p\n",
  			__func__, f);
  
  		f->fr_cqe.done = frwr_wc_localinv;
  		last = &f->fr_invwr;
  		memset(last, 0, sizeof(*last));
  		last->wr_cqe = &f->fr_cqe;
  		last->opcode = IB_WR_LOCAL_INV;
  		last->ex.invalidate_rkey = mw->mw_handle;
  		count++;
  
  		*prev = last;
  		prev = &last->next;
  	}
  	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.
  	 */
  	last->send_flags = IB_SEND_SIGNALED;
  	f->fr_cqe.done = frwr_wc_localinv_wake;
  	reinit_completion(&f->fr_linv_done);
  
  	/* Initialize CQ count, since there is always a signaled
  	 * WR being posted here.  The new cqcount depends on how
  	 * many SQEs are about to be consumed.
  	 */
  	rpcrdma_init_cqcount(&r_xprt->rx_ep, count);
  
  	/* 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++;
  	bad_wr = NULL;
  	rc = ib_post_send(ia->ri_id->qp, first, &bad_wr);
  	if (bad_wr != first)
  		wait_for_completion(&f->fr_linv_done);
  	if (rc)
  		goto reset_mrs;
  
  	/* ORDER: Now DMA unmap all of the MRs, and return
  	 * them to the free MW list.
  	 */
  unmap:
  	while (!list_empty(mws)) {
  		mw = rpcrdma_pop_mw(mws);
  		dprintk("RPC:       %s: DMA unmapping frmr %p\n",
  			__func__, &mw->frmr);
  		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);
  
  	/* Find and reset the MRs in the LOCAL_INV WRs that did not
  	 * get posted.
  	 */
  	rpcrdma_init_cqcount(&r_xprt->rx_ep, -count);
  	while (bad_wr) {
  		f = container_of(bad_wr, struct rpcrdma_frmr,
  				 fr_invwr);
  		mw = container_of(f, struct rpcrdma_mw, frmr);
  
  		__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 = rpcrdma_pop_mw(&req->rl_registered);
  		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,
  };
  