/*
   * Copyright (c) 2015 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).
   */
  
  /* Transport recovery
   *
   * After a transport reconnect, fmr_op_map re-uses the MR already
   * allocated for the RPC, but generates a fresh rkey then maps the
   * MR again. This process is synchronous.
   */
  
  #include "xprt_rdma.h"
  
  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  # define RPCDBG_FACILITY	RPCDBG_TRANS
  #endif
  
  /* Maximum scatter/gather per FMR */
  #define RPCRDMA_MAX_FMR_SGES	(64)
  
  static int
  fmr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
  	    struct rpcrdma_create_data_internal *cdata)
  {
  	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_segments(r_xprt) * RPCRDMA_MAX_FMR_SGES);
  }
  
  static int
  fmr_op_init(struct rpcrdma_xprt *r_xprt)
  {
  	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
  	int mr_access_flags = IB_ACCESS_REMOTE_WRITE | IB_ACCESS_REMOTE_READ;
  	struct ib_fmr_attr fmr_attr = {
  		.max_pages	= RPCRDMA_MAX_FMR_SGES,
  		.max_maps	= 1,
  		.page_shift	= PAGE_SHIFT
  	};
  	struct ib_pd *pd = r_xprt->rx_ia.ri_pd;
  	struct rpcrdma_mw *r;
  	int i, rc;
  
  	spin_lock_init(&buf->rb_mwlock);
  	INIT_LIST_HEAD(&buf->rb_mws);
  	INIT_LIST_HEAD(&buf->rb_all);
  
  	i = max_t(int, RPCRDMA_MAX_DATA_SEGS / RPCRDMA_MAX_FMR_SGES, 1);
  	i += 2;				/* head + tail */
  	i *= buf->rb_max_requests;	/* one set for each RPC slot */
  	dprintk("RPC:       %s: initalizing %d FMRs
  ", __func__, i);
  
  	rc = -ENOMEM;
  	while (i--) {
  		r = kzalloc(sizeof(*r), GFP_KERNEL);
  		if (!r)
  			goto out;
  
  		r->r.fmr.physaddrs = kmalloc(RPCRDMA_MAX_FMR_SGES *
  					     sizeof(u64), GFP_KERNEL);
  		if (!r->r.fmr.physaddrs)
  			goto out_free;
  
  		r->r.fmr.fmr = ib_alloc_fmr(pd, mr_access_flags, &fmr_attr);
  		if (IS_ERR(r->r.fmr.fmr))
  			goto out_fmr_err;
  
  		list_add(&r->mw_list, &buf->rb_mws);
  		list_add(&r->mw_all, &buf->rb_all);
  	}
  	return 0;
  
  out_fmr_err:
  	rc = PTR_ERR(r->r.fmr.fmr);
  	dprintk("RPC:       %s: ib_alloc_fmr status %i
  ", __func__, rc);
  	kfree(r->r.fmr.physaddrs);
  out_free:
  	kfree(r);
  out:
  	return rc;
  }
  
  static int
  __fmr_unmap(struct rpcrdma_mw *r)
  {
  	LIST_HEAD(l);
  
  	list_add(&r->r.fmr.fmr->list, &l);
  	return ib_unmap_fmr(&l);
  }
  
  /* Use the ib_map_phys_fmr() verb to register a memory region
   * for remote access via RDMA READ or RDMA WRITE.
   */
  static int
  fmr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
  	   int nsegs, bool writing)
  {
  	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
  	struct ib_device *device = ia->ri_device;
  	enum dma_data_direction direction = rpcrdma_data_dir(writing);
  	struct rpcrdma_mr_seg *seg1 = seg;
  	int len, pageoff, i, rc;
  	struct rpcrdma_mw *mw;
  
  	mw = seg1->rl_mw;
  	seg1->rl_mw = NULL;
  	if (!mw) {
  		mw = rpcrdma_get_mw(r_xprt);
  		if (!mw)
  			return -ENOMEM;
  	} else {
  		/* this is a retransmit; generate a fresh rkey */
  		rc = __fmr_unmap(mw);
  		if (rc)
  			return rc;
  	}
  
  	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;) {
  		rpcrdma_map_one(device, seg, direction);
  		mw->r.fmr.physaddrs[i] = seg->mr_dma;
  		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;
  	}
  
  	rc = ib_map_phys_fmr(mw->r.fmr.fmr, mw->r.fmr.physaddrs,
  			     i, seg1->mr_dma);
  	if (rc)
  		goto out_maperr;
  
  	seg1->rl_mw = mw;
  	seg1->mr_rkey = mw->r.fmr.fmr->rkey;
  	seg1->mr_base = seg1->mr_dma + pageoff;
  	seg1->mr_nsegs = i;
  	seg1->mr_len = len;
  	return i;
  
  out_maperr:
  	dprintk("RPC:       %s: ib_map_phys_fmr %u@0x%llx+%i (%d) status %i
  ",
  		__func__, len, (unsigned long long)seg1->mr_dma,
  		pageoff, i, rc);
  	while (i--)
  		rpcrdma_unmap_one(device, --seg);
  	return rc;
  }
  
  /* Use the ib_unmap_fmr() verb to prevent further remote
   * access via RDMA READ or RDMA WRITE.
   */
  static int
  fmr_op_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg)
  {
  	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
  	struct rpcrdma_mr_seg *seg1 = seg;
  	struct rpcrdma_mw *mw = seg1->rl_mw;
  	int rc, nsegs = seg->mr_nsegs;
  
  	dprintk("RPC:       %s: FMR %p
  ", __func__, mw);
  
  	seg1->rl_mw = NULL;
  	while (seg1->mr_nsegs--)
  		rpcrdma_unmap_one(ia->ri_device, seg++);
  	rc = __fmr_unmap(mw);
  	if (rc)
  		goto out_err;
  	rpcrdma_put_mw(r_xprt, mw);
  	return nsegs;
  
  out_err:
  	/* The FMR is abandoned, but remains in rb_all. fmr_op_destroy
  	 * will attempt to release it when the transport is destroyed.
  	 */
  	dprintk("RPC:       %s: ib_unmap_fmr status %i
  ", __func__, rc);
  	return nsegs;
  }
  
  static void
  fmr_op_destroy(struct rpcrdma_buffer *buf)
  {
  	struct rpcrdma_mw *r;
  	int rc;
  
  	while (!list_empty(&buf->rb_all)) {
  		r = list_entry(buf->rb_all.next, struct rpcrdma_mw, mw_all);
  		list_del(&r->mw_all);
  		kfree(r->r.fmr.physaddrs);
  
  		rc = ib_dealloc_fmr(r->r.fmr.fmr);
  		if (rc)
  			dprintk("RPC:       %s: ib_dealloc_fmr failed %i
  ",
  				__func__, rc);
  
  		kfree(r);
  	}
  }
  
  const struct rpcrdma_memreg_ops rpcrdma_fmr_memreg_ops = {
  	.ro_map				= fmr_op_map,
  	.ro_unmap			= fmr_op_unmap,
  	.ro_open			= fmr_op_open,
  	.ro_maxpages			= fmr_op_maxpages,
  	.ro_init			= fmr_op_init,
  	.ro_destroy			= fmr_op_destroy,
  	.ro_displayname			= "fmr",
  };