1 // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
3 * Copyright (c) 2016-2018 Oracle. All rights reserved.
4 * Copyright (c) 2014 Open Grid Computing, Inc. All rights reserved.
5 * Copyright (c) 2005-2006 Network Appliance, Inc. All rights reserved.
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42 * Author: Tom Tucker <tom@opengridcomputing.com>
47 * The main entry point is svc_rdma_sendto. This is called by the
48 * RPC server when an RPC Reply is ready to be transmitted to a client.
50 * The passed-in svc_rqst contains a struct xdr_buf which holds an
51 * XDR-encoded RPC Reply message. sendto must construct the RPC-over-RDMA
52 * transport header, post all Write WRs needed for this Reply, then post
53 * a Send WR conveying the transport header and the RPC message itself to
56 * svc_rdma_sendto must fully transmit the Reply before returning, as
57 * the svc_rqst will be recycled as soon as sendto returns. Remaining
58 * resources referred to by the svc_rqst are also recycled at that time.
59 * Therefore any resources that must remain longer must be detached
60 * from the svc_rqst and released later.
64 * The I/O that performs Reply transmission is asynchronous, and may
65 * complete well after sendto returns. Thus pages under I/O must be
66 * removed from the svc_rqst before sendto returns.
68 * The logic here depends on Send Queue and completion ordering. Since
69 * the Send WR is always posted last, it will always complete last. Thus
70 * when it completes, it is guaranteed that all previous Write WRs have
73 * Write WRs are constructed and posted. Each Write segment gets its own
74 * svc_rdma_rw_ctxt, allowing the Write completion handler to find and
75 * DMA-unmap the pages under I/O for that Write segment. The Write
76 * completion handler does not release any pages.
78 * When the Send WR is constructed, it also gets its own svc_rdma_send_ctxt.
79 * The ownership of all of the Reply's pages are transferred into that
80 * ctxt, the Send WR is posted, and sendto returns.
82 * The svc_rdma_send_ctxt is presented when the Send WR completes. The
83 * Send completion handler finally releases the Reply's pages.
85 * This mechanism also assumes that completions on the transport's Send
86 * Completion Queue do not run in parallel. Otherwise a Write completion
87 * and Send completion running at the same time could release pages that
88 * are still DMA-mapped.
92 * - If the Send WR is posted successfully, it will either complete
93 * successfully, or get flushed. Either way, the Send completion
94 * handler releases the Reply's pages.
95 * - If the Send WR cannot be not posted, the forward path releases
98 * This handles the case, without the use of page reference counting,
99 * where two different Write segments send portions of the same page.
102 #include <linux/spinlock.h>
103 #include <asm/unaligned.h>
105 #include <rdma/ib_verbs.h>
106 #include <rdma/rdma_cm.h>
108 #include <linux/sunrpc/debug.h>
109 #include <linux/sunrpc/rpc_rdma.h>
110 #include <linux/sunrpc/svc_rdma.h>
112 #include "xprt_rdma.h"
113 #include <trace/events/rpcrdma.h>
115 #define RPCDBG_FACILITY RPCDBG_SVCXPRT
117 static void svc_rdma_wc_send(struct ib_cq *cq, struct ib_wc *wc);
119 static inline struct svc_rdma_send_ctxt *
120 svc_rdma_next_send_ctxt(struct list_head *list)
122 return list_first_entry_or_null(list, struct svc_rdma_send_ctxt,
126 static struct svc_rdma_send_ctxt *
127 svc_rdma_send_ctxt_alloc(struct svcxprt_rdma *rdma)
129 struct svc_rdma_send_ctxt *ctxt;
135 size = sizeof(*ctxt);
136 size += rdma->sc_max_send_sges * sizeof(struct ib_sge);
137 ctxt = kmalloc(size, GFP_KERNEL);
140 buffer = kmalloc(rdma->sc_max_req_size, GFP_KERNEL);
143 addr = ib_dma_map_single(rdma->sc_pd->device, buffer,
144 rdma->sc_max_req_size, DMA_TO_DEVICE);
145 if (ib_dma_mapping_error(rdma->sc_pd->device, addr))
148 ctxt->sc_send_wr.next = NULL;
149 ctxt->sc_send_wr.wr_cqe = &ctxt->sc_cqe;
150 ctxt->sc_send_wr.sg_list = ctxt->sc_sges;
151 ctxt->sc_send_wr.send_flags = IB_SEND_SIGNALED;
152 ctxt->sc_cqe.done = svc_rdma_wc_send;
153 ctxt->sc_xprt_buf = buffer;
154 ctxt->sc_sges[0].addr = addr;
156 for (i = 0; i < rdma->sc_max_send_sges; i++)
157 ctxt->sc_sges[i].lkey = rdma->sc_pd->local_dma_lkey;
169 * svc_rdma_send_ctxts_destroy - Release all send_ctxt's for an xprt
170 * @rdma: svcxprt_rdma being torn down
173 void svc_rdma_send_ctxts_destroy(struct svcxprt_rdma *rdma)
175 struct svc_rdma_send_ctxt *ctxt;
177 while ((ctxt = svc_rdma_next_send_ctxt(&rdma->sc_send_ctxts))) {
178 list_del(&ctxt->sc_list);
179 ib_dma_unmap_single(rdma->sc_pd->device,
180 ctxt->sc_sges[0].addr,
181 rdma->sc_max_req_size,
183 kfree(ctxt->sc_xprt_buf);
189 * svc_rdma_send_ctxt_get - Get a free send_ctxt
190 * @rdma: controlling svcxprt_rdma
192 * Returns a ready-to-use send_ctxt, or NULL if none are
193 * available and a fresh one cannot be allocated.
195 struct svc_rdma_send_ctxt *svc_rdma_send_ctxt_get(struct svcxprt_rdma *rdma)
197 struct svc_rdma_send_ctxt *ctxt;
199 spin_lock(&rdma->sc_send_lock);
200 ctxt = svc_rdma_next_send_ctxt(&rdma->sc_send_ctxts);
203 list_del(&ctxt->sc_list);
204 spin_unlock(&rdma->sc_send_lock);
207 ctxt->sc_send_wr.num_sge = 0;
208 ctxt->sc_cur_sge_no = 0;
209 ctxt->sc_page_count = 0;
213 spin_unlock(&rdma->sc_send_lock);
214 ctxt = svc_rdma_send_ctxt_alloc(rdma);
221 * svc_rdma_send_ctxt_put - Return send_ctxt to free list
222 * @rdma: controlling svcxprt_rdma
223 * @ctxt: object to return to the free list
225 * Pages left in sc_pages are DMA unmapped and released.
227 void svc_rdma_send_ctxt_put(struct svcxprt_rdma *rdma,
228 struct svc_rdma_send_ctxt *ctxt)
230 struct ib_device *device = rdma->sc_cm_id->device;
233 /* The first SGE contains the transport header, which
234 * remains mapped until @ctxt is destroyed.
236 for (i = 1; i < ctxt->sc_send_wr.num_sge; i++)
237 ib_dma_unmap_page(device,
238 ctxt->sc_sges[i].addr,
239 ctxt->sc_sges[i].length,
242 for (i = 0; i < ctxt->sc_page_count; ++i)
243 put_page(ctxt->sc_pages[i]);
245 spin_lock(&rdma->sc_send_lock);
246 list_add(&ctxt->sc_list, &rdma->sc_send_ctxts);
247 spin_unlock(&rdma->sc_send_lock);
251 * svc_rdma_wc_send - Invoked by RDMA provider for each polled Send WC
252 * @cq: Completion Queue context
253 * @wc: Work Completion object
255 * NB: The svc_xprt/svcxprt_rdma is pinned whenever it's possible that
256 * the Send completion handler could be running.
258 static void svc_rdma_wc_send(struct ib_cq *cq, struct ib_wc *wc)
260 struct svcxprt_rdma *rdma = cq->cq_context;
261 struct ib_cqe *cqe = wc->wr_cqe;
262 struct svc_rdma_send_ctxt *ctxt;
264 trace_svcrdma_wc_send(wc);
266 atomic_inc(&rdma->sc_sq_avail);
267 wake_up(&rdma->sc_send_wait);
269 ctxt = container_of(cqe, struct svc_rdma_send_ctxt, sc_cqe);
270 svc_rdma_send_ctxt_put(rdma, ctxt);
272 if (unlikely(wc->status != IB_WC_SUCCESS)) {
273 set_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags);
274 svc_xprt_enqueue(&rdma->sc_xprt);
275 if (wc->status != IB_WC_WR_FLUSH_ERR)
276 pr_err("svcrdma: Send: %s (%u/0x%x)\n",
277 ib_wc_status_msg(wc->status),
278 wc->status, wc->vendor_err);
281 svc_xprt_put(&rdma->sc_xprt);
285 * svc_rdma_send - Post a single Send WR
286 * @rdma: transport on which to post the WR
287 * @wr: prepared Send WR to post
289 * Returns zero the Send WR was posted successfully. Otherwise, a
290 * negative errno is returned.
292 int svc_rdma_send(struct svcxprt_rdma *rdma, struct ib_send_wr *wr)
294 struct ib_send_wr *bad_wr;
299 /* If the SQ is full, wait until an SQ entry is available */
301 if ((atomic_dec_return(&rdma->sc_sq_avail) < 0)) {
302 atomic_inc(&rdma_stat_sq_starve);
303 trace_svcrdma_sq_full(rdma);
304 atomic_inc(&rdma->sc_sq_avail);
305 wait_event(rdma->sc_send_wait,
306 atomic_read(&rdma->sc_sq_avail) > 1);
307 if (test_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags))
309 trace_svcrdma_sq_retry(rdma);
313 svc_xprt_get(&rdma->sc_xprt);
314 ret = ib_post_send(rdma->sc_qp, wr, &bad_wr);
315 trace_svcrdma_post_send(wr, ret);
317 set_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags);
318 svc_xprt_put(&rdma->sc_xprt);
319 wake_up(&rdma->sc_send_wait);
326 static u32 xdr_padsize(u32 len)
328 return (len & 3) ? (4 - (len & 3)) : 0;
331 /* Returns length of transport header, in bytes.
333 static unsigned int svc_rdma_reply_hdr_len(__be32 *rdma_resp)
340 /* RPC-over-RDMA V1 replies never have a Read list. */
341 p += rpcrdma_fixed_maxsz + 1;
343 /* Skip Write list. */
344 while (*p++ != xdr_zero) {
345 nsegs = be32_to_cpup(p++);
346 p += nsegs * rpcrdma_segment_maxsz;
349 /* Skip Reply chunk. */
350 if (*p++ != xdr_zero) {
351 nsegs = be32_to_cpup(p++);
352 p += nsegs * rpcrdma_segment_maxsz;
355 return (unsigned long)p - (unsigned long)rdma_resp;
358 /* One Write chunk is copied from Call transport header to Reply
359 * transport header. Each segment's length field is updated to
360 * reflect number of bytes consumed in the segment.
362 * Returns number of segments in this chunk.
364 static unsigned int xdr_encode_write_chunk(__be32 *dst, __be32 *src,
365 unsigned int remaining)
367 unsigned int i, nsegs;
370 /* Write list discriminator */
373 /* number of segments in this chunk */
374 nsegs = be32_to_cpup(src);
377 for (i = nsegs; i; i--) {
378 /* segment's RDMA handle */
381 /* bytes returned in this segment */
382 seg_len = be32_to_cpu(*src);
383 if (remaining >= seg_len) {
384 /* entire segment was consumed */
386 remaining -= seg_len;
388 /* segment only partly filled */
389 *dst = cpu_to_be32(remaining);
394 /* segment's RDMA offset */
402 /* The client provided a Write list in the Call message. Fill in
403 * the segments in the first Write chunk in the Reply's transport
404 * header with the number of bytes consumed in each segment.
405 * Remaining chunks are returned unused.
408 * - Client has provided only one Write chunk
410 static void svc_rdma_xdr_encode_write_list(__be32 *rdma_resp, __be32 *wr_ch,
411 unsigned int consumed)
416 /* RPC-over-RDMA V1 replies never have a Read list. */
417 p = rdma_resp + rpcrdma_fixed_maxsz + 1;
420 while (*q != xdr_zero) {
421 nsegs = xdr_encode_write_chunk(p, q, consumed);
422 q += 2 + nsegs * rpcrdma_segment_maxsz;
423 p += 2 + nsegs * rpcrdma_segment_maxsz;
427 /* Terminate Write list */
430 /* Reply chunk discriminator; may be replaced later */
434 /* The client provided a Reply chunk in the Call message. Fill in
435 * the segments in the Reply chunk in the Reply message with the
436 * number of bytes consumed in each segment.
439 * - Reply can always fit in the provided Reply chunk
441 static void svc_rdma_xdr_encode_reply_chunk(__be32 *rdma_resp, __be32 *rp_ch,
442 unsigned int consumed)
446 /* Find the Reply chunk in the Reply's xprt header.
447 * RPC-over-RDMA V1 replies never have a Read list.
449 p = rdma_resp + rpcrdma_fixed_maxsz + 1;
451 /* Skip past Write list */
452 while (*p++ != xdr_zero)
453 p += 1 + be32_to_cpup(p) * rpcrdma_segment_maxsz;
455 xdr_encode_write_chunk(p, rp_ch, consumed);
458 /* Parse the RPC Call's transport header.
460 static void svc_rdma_get_write_arrays(__be32 *rdma_argp,
461 __be32 **write, __be32 **reply)
465 p = rdma_argp + rpcrdma_fixed_maxsz;
468 while (*p++ != xdr_zero)
472 if (*p != xdr_zero) {
474 while (*p++ != xdr_zero)
475 p += 1 + be32_to_cpu(*p) * 4;
488 /* RPC-over-RDMA Version One private extension: Remote Invalidation.
489 * Responder's choice: requester signals it can handle Send With
490 * Invalidate, and responder chooses one rkey to invalidate.
492 * Find a candidate rkey to invalidate when sending a reply. Picks the
493 * first R_key it finds in the chunk lists.
495 * Returns zero if RPC's chunk lists are empty.
497 static u32 svc_rdma_get_inv_rkey(__be32 *rdma_argp,
498 __be32 *wr_lst, __be32 *rp_ch)
502 p = rdma_argp + rpcrdma_fixed_maxsz;
505 else if (wr_lst && be32_to_cpup(wr_lst + 1))
507 else if (rp_ch && be32_to_cpup(rp_ch + 1))
511 return be32_to_cpup(p);
514 static int svc_rdma_dma_map_page(struct svcxprt_rdma *rdma,
515 struct svc_rdma_send_ctxt *ctxt,
517 unsigned long offset,
520 struct ib_device *dev = rdma->sc_cm_id->device;
523 dma_addr = ib_dma_map_page(dev, page, offset, len, DMA_TO_DEVICE);
524 if (ib_dma_mapping_error(dev, dma_addr))
527 ctxt->sc_sges[ctxt->sc_cur_sge_no].addr = dma_addr;
528 ctxt->sc_sges[ctxt->sc_cur_sge_no].length = len;
529 ctxt->sc_send_wr.num_sge++;
533 trace_svcrdma_dma_map_page(rdma, page);
537 /* ib_dma_map_page() is used here because svc_rdma_dma_unmap()
538 * handles DMA-unmap and it uses ib_dma_unmap_page() exclusively.
540 static int svc_rdma_dma_map_buf(struct svcxprt_rdma *rdma,
541 struct svc_rdma_send_ctxt *ctxt,
545 return svc_rdma_dma_map_page(rdma, ctxt, virt_to_page(base),
546 offset_in_page(base), len);
550 * svc_rdma_sync_reply_hdr - DMA sync the transport header buffer
551 * @rdma: controlling transport
552 * @ctxt: send_ctxt for the Send WR
553 * @len: length of transport header
556 void svc_rdma_sync_reply_hdr(struct svcxprt_rdma *rdma,
557 struct svc_rdma_send_ctxt *ctxt,
560 ctxt->sc_sges[0].length = len;
561 ctxt->sc_send_wr.num_sge++;
562 ib_dma_sync_single_for_device(rdma->sc_pd->device,
563 ctxt->sc_sges[0].addr, len,
567 /* svc_rdma_map_reply_msg - Map the buffer holding RPC message
568 * @rdma: controlling transport
569 * @ctxt: send_ctxt for the Send WR
570 * @xdr: prepared xdr_buf containing RPC message
571 * @wr_lst: pointer to Call header's Write list, or NULL
573 * Load the xdr_buf into the ctxt's sge array, and DMA map each
574 * element as it is added.
576 * Returns zero on success, or a negative errno on failure.
578 int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
579 struct svc_rdma_send_ctxt *ctxt,
580 struct xdr_buf *xdr, __be32 *wr_lst)
582 unsigned int len, remaining;
583 unsigned long page_off;
584 struct page **ppages;
589 if (++ctxt->sc_cur_sge_no >= rdma->sc_max_send_sges)
591 ret = svc_rdma_dma_map_buf(rdma, ctxt,
592 xdr->head[0].iov_base,
593 xdr->head[0].iov_len);
597 /* If a Write chunk is present, the xdr_buf's page list
598 * is not included inline. However the Upper Layer may
599 * have added XDR padding in the tail buffer, and that
600 * should not be included inline.
603 base = xdr->tail[0].iov_base;
604 len = xdr->tail[0].iov_len;
605 xdr_pad = xdr_padsize(xdr->page_len);
607 if (len && xdr_pad) {
615 ppages = xdr->pages + (xdr->page_base >> PAGE_SHIFT);
616 page_off = xdr->page_base & ~PAGE_MASK;
617 remaining = xdr->page_len;
619 len = min_t(u32, PAGE_SIZE - page_off, remaining);
621 if (++ctxt->sc_cur_sge_no >= rdma->sc_max_send_sges)
623 ret = svc_rdma_dma_map_page(rdma, ctxt, *ppages++,
632 base = xdr->tail[0].iov_base;
633 len = xdr->tail[0].iov_len;
636 if (++ctxt->sc_cur_sge_no >= rdma->sc_max_send_sges)
638 ret = svc_rdma_dma_map_buf(rdma, ctxt, base, len);
646 /* The svc_rqst and all resources it owns are released as soon as
647 * svc_rdma_sendto returns. Transfer pages under I/O to the ctxt
648 * so they are released by the Send completion handler.
650 static void svc_rdma_save_io_pages(struct svc_rqst *rqstp,
651 struct svc_rdma_send_ctxt *ctxt)
653 int i, pages = rqstp->rq_next_page - rqstp->rq_respages;
655 ctxt->sc_page_count += pages;
656 for (i = 0; i < pages; i++) {
657 ctxt->sc_pages[i] = rqstp->rq_respages[i];
658 rqstp->rq_respages[i] = NULL;
661 /* Prevent svc_xprt_release from releasing pages in rq_pages */
662 rqstp->rq_next_page = rqstp->rq_respages;
665 /* Prepare the portion of the RPC Reply that will be transmitted
666 * via RDMA Send. The RPC-over-RDMA transport header is prepared
667 * in sc_sges[0], and the RPC xdr_buf is prepared in following sges.
669 * Depending on whether a Write list or Reply chunk is present,
670 * the server may send all, a portion of, or none of the xdr_buf.
671 * In the latter case, only the transport header (sc_sges[0]) is
674 * RDMA Send is the last step of transmitting an RPC reply. Pages
675 * involved in the earlier RDMA Writes are here transferred out
676 * of the rqstp and into the ctxt's page array. These pages are
677 * DMA unmapped by each Write completion, but the subsequent Send
678 * completion finally releases these pages.
681 * - The Reply's transport header will never be larger than a page.
683 static int svc_rdma_send_reply_msg(struct svcxprt_rdma *rdma,
684 struct svc_rdma_send_ctxt *ctxt,
686 struct svc_rqst *rqstp,
687 __be32 *wr_lst, __be32 *rp_ch)
692 ret = svc_rdma_map_reply_msg(rdma, ctxt,
693 &rqstp->rq_res, wr_lst);
698 svc_rdma_save_io_pages(rqstp, ctxt);
700 ctxt->sc_send_wr.opcode = IB_WR_SEND;
701 if (rdma->sc_snd_w_inv) {
702 ctxt->sc_send_wr.ex.invalidate_rkey =
703 svc_rdma_get_inv_rkey(rdma_argp, wr_lst, rp_ch);
704 if (ctxt->sc_send_wr.ex.invalidate_rkey)
705 ctxt->sc_send_wr.opcode = IB_WR_SEND_WITH_INV;
707 dprintk("svcrdma: posting Send WR with %u sge(s)\n",
708 ctxt->sc_send_wr.num_sge);
709 return svc_rdma_send(rdma, &ctxt->sc_send_wr);
712 /* Given the client-provided Write and Reply chunks, the server was not
713 * able to form a complete reply. Return an RDMA_ERROR message so the
714 * client can retire this RPC transaction. As above, the Send completion
715 * routine releases payload pages that were part of a previous RDMA Write.
717 * Remote Invalidation is skipped for simplicity.
719 static int svc_rdma_send_error_msg(struct svcxprt_rdma *rdma,
720 struct svc_rdma_send_ctxt *ctxt,
721 struct svc_rqst *rqstp)
726 p = ctxt->sc_xprt_buf;
727 trace_svcrdma_err_chunk(*p);
731 svc_rdma_sync_reply_hdr(rdma, ctxt, RPCRDMA_HDRLEN_ERR);
733 svc_rdma_save_io_pages(rqstp, ctxt);
735 ctxt->sc_send_wr.opcode = IB_WR_SEND;
736 ret = svc_rdma_send(rdma, &ctxt->sc_send_wr);
738 svc_rdma_send_ctxt_put(rdma, ctxt);
745 void svc_rdma_prep_reply_hdr(struct svc_rqst *rqstp)
750 * svc_rdma_sendto - Transmit an RPC reply
751 * @rqstp: processed RPC request, reply XDR already in ::rq_res
753 * Any resources still associated with @rqstp are released upon return.
754 * If no reply message was possible, the connection is closed.
757 * %0 if an RPC reply has been successfully posted,
758 * %-ENOMEM if a resource shortage occurred (connection is lost),
759 * %-ENOTCONN if posting failed (connection is lost).
761 int svc_rdma_sendto(struct svc_rqst *rqstp)
763 struct svc_xprt *xprt = rqstp->rq_xprt;
764 struct svcxprt_rdma *rdma =
765 container_of(xprt, struct svcxprt_rdma, sc_xprt);
766 struct svc_rdma_recv_ctxt *rctxt = rqstp->rq_xprt_ctxt;
767 __be32 *p, *rdma_argp, *rdma_resp, *wr_lst, *rp_ch;
768 struct xdr_buf *xdr = &rqstp->rq_res;
769 struct svc_rdma_send_ctxt *sctxt;
772 rdma_argp = rctxt->rc_recv_buf;
773 svc_rdma_get_write_arrays(rdma_argp, &wr_lst, &rp_ch);
775 /* Create the RDMA response header. xprt->xpt_mutex,
776 * acquired in svc_send(), serializes RPC replies. The
777 * code path below that inserts the credit grant value
778 * into each transport header runs only inside this
782 sctxt = svc_rdma_send_ctxt_get(rdma);
785 rdma_resp = sctxt->sc_xprt_buf;
789 *p++ = *(rdma_argp + 1);
790 *p++ = rdma->sc_fc_credits;
791 *p++ = rp_ch ? rdma_nomsg : rdma_msg;
793 /* Start with empty chunks */
799 /* XXX: Presume the client sent only one Write chunk */
800 ret = svc_rdma_send_write_chunk(rdma, wr_lst, xdr);
803 svc_rdma_xdr_encode_write_list(rdma_resp, wr_lst, ret);
806 ret = svc_rdma_send_reply_chunk(rdma, rp_ch, wr_lst, xdr);
809 svc_rdma_xdr_encode_reply_chunk(rdma_resp, rp_ch, ret);
812 svc_rdma_sync_reply_hdr(rdma, sctxt, svc_rdma_reply_hdr_len(rdma_resp));
813 ret = svc_rdma_send_reply_msg(rdma, sctxt, rdma_argp, rqstp,
820 rqstp->rq_xprt_ctxt = NULL;
821 svc_rdma_recv_ctxt_put(rdma, rctxt);
825 if (ret != -E2BIG && ret != -EINVAL)
828 ret = svc_rdma_send_error_msg(rdma, sctxt, rqstp);
835 svc_rdma_send_ctxt_put(rdma, sctxt);
837 trace_svcrdma_send_failed(rqstp, ret);
838 set_bit(XPT_CLOSE, &xprt->xpt_flags);