secondary.c revision 207371
1/*-
2 * Copyright (c) 2009-2010 The FreeBSD Foundation
3 * All rights reserved.
4 *
5 * This software was developed by Pawel Jakub Dawidek under sponsorship from
6 * the FreeBSD Foundation.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD: head/sbin/hastd/secondary.c 207371 2010-04-29 15:36:32Z pjd $");
32
33#include <sys/param.h>
34#include <sys/time.h>
35#include <sys/bio.h>
36#include <sys/disk.h>
37#include <sys/stat.h>
38
39#include <assert.h>
40#include <err.h>
41#include <errno.h>
42#include <fcntl.h>
43#include <libgeom.h>
44#include <pthread.h>
45#include <stdint.h>
46#include <stdio.h>
47#include <string.h>
48#include <sysexits.h>
49#include <unistd.h>
50
51#include <activemap.h>
52#include <nv.h>
53#include <pjdlog.h>
54
55#include "control.h"
56#include "hast.h"
57#include "hast_proto.h"
58#include "hastd.h"
59#include "metadata.h"
60#include "proto.h"
61#include "subr.h"
62#include "synch.h"
63
64struct hio {
65	uint64_t 	 hio_seq;
66	int	 	 hio_error;
67	struct nv	*hio_nv;
68	void		*hio_data;
69	uint8_t		 hio_cmd;
70	uint64_t	 hio_offset;
71	uint64_t	 hio_length;
72	TAILQ_ENTRY(hio) hio_next;
73};
74
75/*
76 * Free list holds unused structures. When free list is empty, we have to wait
77 * until some in-progress requests are freed.
78 */
79static TAILQ_HEAD(, hio) hio_free_list;
80static pthread_mutex_t hio_free_list_lock;
81static pthread_cond_t hio_free_list_cond;
82/*
83 * Disk thread (the one that do I/O requests) takes requests from this list.
84 */
85static TAILQ_HEAD(, hio) hio_disk_list;
86static pthread_mutex_t hio_disk_list_lock;
87static pthread_cond_t hio_disk_list_cond;
88/*
89 * There is one recv list for every component, although local components don't
90 * use recv lists as local requests are done synchronously.
91 */
92static TAILQ_HEAD(, hio) hio_send_list;
93static pthread_mutex_t hio_send_list_lock;
94static pthread_cond_t hio_send_list_cond;
95
96/*
97 * Maximum number of outstanding I/O requests.
98 */
99#define	HAST_HIO_MAX	256
100
101static void *recv_thread(void *arg);
102static void *disk_thread(void *arg);
103static void *send_thread(void *arg);
104
105static void
106init_environment(void)
107{
108	struct hio *hio;
109	unsigned int ii;
110
111	/*
112	 * Initialize lists, their locks and theirs condition variables.
113	 */
114	TAILQ_INIT(&hio_free_list);
115	mtx_init(&hio_free_list_lock);
116	cv_init(&hio_free_list_cond);
117	TAILQ_INIT(&hio_disk_list);
118	mtx_init(&hio_disk_list_lock);
119	cv_init(&hio_disk_list_cond);
120	TAILQ_INIT(&hio_send_list);
121	mtx_init(&hio_send_list_lock);
122	cv_init(&hio_send_list_cond);
123
124	/*
125	 * Allocate requests pool and initialize requests.
126	 */
127	for (ii = 0; ii < HAST_HIO_MAX; ii++) {
128		hio = malloc(sizeof(*hio));
129		if (hio == NULL) {
130			errx(EX_TEMPFAIL, "cannot allocate %zu bytes of memory "
131			    "for hio request", sizeof(*hio));
132		}
133		hio->hio_error = 0;
134		hio->hio_data = malloc(MAXPHYS);
135		if (hio->hio_data == NULL) {
136			errx(EX_TEMPFAIL, "cannot allocate %zu bytes of memory "
137			    "for gctl_data", (size_t)MAXPHYS);
138		}
139		TAILQ_INSERT_HEAD(&hio_free_list, hio, hio_next);
140	}
141}
142
143static void
144init_local(struct hast_resource *res)
145{
146
147	if (metadata_read(res, true) < 0)
148		exit(EX_NOINPUT);
149}
150
151static void
152init_remote(struct hast_resource *res, struct nv *nvin)
153{
154	uint64_t resuid;
155	struct nv *nvout;
156	unsigned char *map;
157	size_t mapsize;
158
159	map = NULL;
160	mapsize = 0;
161	nvout = nv_alloc();
162	nv_add_int64(nvout, (int64_t)res->hr_datasize, "datasize");
163	nv_add_int32(nvout, (int32_t)res->hr_extentsize, "extentsize");
164	resuid = nv_get_uint64(nvin, "resuid");
165	res->hr_primary_localcnt = nv_get_uint64(nvin, "localcnt");
166	res->hr_primary_remotecnt = nv_get_uint64(nvin, "remotecnt");
167	nv_add_uint64(nvout, res->hr_secondary_localcnt, "localcnt");
168	nv_add_uint64(nvout, res->hr_secondary_remotecnt, "remotecnt");
169	mapsize = activemap_calc_ondisk_size(res->hr_local_mediasize -
170	    METADATA_SIZE, res->hr_extentsize, res->hr_local_sectorsize);
171	map = malloc(mapsize);
172	if (map == NULL) {
173		pjdlog_exitx(EX_TEMPFAIL,
174		    "Unable to allocate memory (%zu bytes) for activemap.",
175		    mapsize);
176	}
177	nv_add_uint32(nvout, (uint32_t)mapsize, "mapsize");
178	/*
179	 * When we work as primary and secondary is missing we will increase
180	 * localcnt in our metadata. When secondary is connected and synced
181	 * we make localcnt be equal to remotecnt, which means nodes are more
182	 * or less in sync.
183	 * Split-brain condition is when both nodes are not able to communicate
184	 * and are both configured as primary nodes. In turn, they can both
185	 * make incompatible changes to the data and we have to detect that.
186	 * Under split-brain condition we will increase our localcnt on first
187	 * write and remote node will increase its localcnt on first write.
188	 * When we connect we can see that primary's localcnt is greater than
189	 * our remotecnt (primary was modified while we weren't watching) and
190	 * our localcnt is greater than primary's remotecnt (we were modified
191	 * while primary wasn't watching).
192	 * There are many possible combinations which are all gathered below.
193	 * Don't pay too much attention to exact numbers, the more important
194	 * is to compare them. We compare secondary's local with primary's
195	 * remote and secondary's remote with primary's local.
196	 * Note that every case where primary's localcnt is smaller than
197	 * secondary's remotecnt and where secondary's localcnt is smaller than
198	 * primary's remotecnt should be impossible in practise. We will perform
199	 * full synchronization then. Those cases are marked with an asterisk.
200	 * Regular synchronization means that only extents marked as dirty are
201	 * synchronized (regular synchronization).
202	 *
203	 * SECONDARY METADATA PRIMARY METADATA
204	 * local=3 remote=3   local=2 remote=2*  ?! Full sync from secondary.
205	 * local=3 remote=3   local=2 remote=3*  ?! Full sync from primary.
206	 * local=3 remote=3   local=2 remote=4*  ?! Full sync from primary.
207	 * local=3 remote=3   local=3 remote=2   Primary is out-of-date,
208	 *                                       regular sync from secondary.
209	 * local=3 remote=3   local=3 remote=3   Regular sync just in case.
210	 * local=3 remote=3   local=3 remote=4*  ?! Full sync from primary.
211	 * local=3 remote=3   local=4 remote=2   Split-brain condition.
212	 * local=3 remote=3   local=4 remote=3   Secondary out-of-date,
213	 *                                       regular sync from primary.
214	 * local=3 remote=3   local=4 remote=4*  ?! Full sync from primary.
215	 */
216	if (res->hr_resuid == 0) {
217		/*
218		 * Provider is used for the first time. Initialize everything.
219		 */
220		assert(res->hr_secondary_localcnt == 0);
221		res->hr_resuid = resuid;
222		if (metadata_write(res) < 0)
223			exit(EX_NOINPUT);
224		memset(map, 0xff, mapsize);
225		nv_add_uint8(nvout, HAST_SYNCSRC_PRIMARY, "syncsrc");
226	} else if (
227	    /* Is primary is out-of-date? */
228	    (res->hr_secondary_localcnt > res->hr_primary_remotecnt &&
229	     res->hr_secondary_remotecnt == res->hr_primary_localcnt) ||
230	    /* Node are more or less in sync? */
231	    (res->hr_secondary_localcnt == res->hr_primary_remotecnt &&
232	     res->hr_secondary_remotecnt == res->hr_primary_localcnt) ||
233	    /* Is secondary is out-of-date? */
234	    (res->hr_secondary_localcnt == res->hr_primary_remotecnt &&
235	     res->hr_secondary_remotecnt < res->hr_primary_localcnt)) {
236		/*
237		 * Nodes are more or less in sync or one of the nodes is
238		 * out-of-date.
239		 * It doesn't matter at this point which one, we just have to
240		 * send out local bitmap to the remote node.
241		 */
242		if (pread(res->hr_localfd, map, mapsize, METADATA_SIZE) !=
243		    (ssize_t)mapsize) {
244			pjdlog_exit(LOG_ERR, "Unable to read activemap");
245		}
246		if (res->hr_secondary_localcnt > res->hr_primary_remotecnt &&
247		     res->hr_secondary_remotecnt == res->hr_primary_localcnt) {
248			/* Primary is out-of-date, sync from secondary. */
249			nv_add_uint8(nvout, HAST_SYNCSRC_SECONDARY, "syncsrc");
250		} else {
251			/*
252			 * Secondary is out-of-date or counts match.
253			 * Sync from primary.
254			 */
255			nv_add_uint8(nvout, HAST_SYNCSRC_PRIMARY, "syncsrc");
256		}
257	} else if (res->hr_secondary_localcnt > res->hr_primary_remotecnt &&
258	     res->hr_primary_localcnt > res->hr_secondary_remotecnt) {
259		/*
260		 * Not good, we have split-brain condition.
261		 */
262		pjdlog_error("Split-brain detected, exiting.");
263		nv_add_string(nvout, "Split-brain condition!", "errmsg");
264		free(map);
265		map = NULL;
266		mapsize = 0;
267	} else /* if (res->hr_secondary_localcnt < res->hr_primary_remotecnt ||
268	    res->hr_primary_localcnt < res->hr_secondary_remotecnt) */ {
269		/*
270		 * This should never happen in practise, but we will perform
271		 * full synchronization.
272		 */
273		assert(res->hr_secondary_localcnt < res->hr_primary_remotecnt ||
274		    res->hr_primary_localcnt < res->hr_secondary_remotecnt);
275		mapsize = activemap_calc_ondisk_size(res->hr_local_mediasize -
276		    METADATA_SIZE, res->hr_extentsize,
277		    res->hr_local_sectorsize);
278		memset(map, 0xff, mapsize);
279		if (res->hr_secondary_localcnt > res->hr_primary_remotecnt) {
280			/* In this one of five cases sync from secondary. */
281			nv_add_uint8(nvout, HAST_SYNCSRC_SECONDARY, "syncsrc");
282		} else {
283			/* For the rest four cases sync from primary. */
284			nv_add_uint8(nvout, HAST_SYNCSRC_PRIMARY, "syncsrc");
285		}
286		pjdlog_warning("This should never happen, asking for full synchronization (primary(local=%ju, remote=%ju), secondary(local=%ju, remote=%ju)).",
287		    (uintmax_t)res->hr_primary_localcnt,
288		    (uintmax_t)res->hr_primary_remotecnt,
289		    (uintmax_t)res->hr_secondary_localcnt,
290		    (uintmax_t)res->hr_secondary_remotecnt);
291	}
292	if (hast_proto_send(res, res->hr_remotein, nvout, map, mapsize) < 0) {
293		pjdlog_errno(LOG_WARNING, "Unable to send activemap to %s",
294		    res->hr_remoteaddr);
295		nv_free(nvout);
296		exit(EX_TEMPFAIL);
297	}
298	if (res->hr_secondary_localcnt > res->hr_primary_remotecnt &&
299	     res->hr_primary_localcnt > res->hr_secondary_remotecnt) {
300		/* Exit on split-brain. */
301		exit(EX_CONFIG);
302	}
303}
304
305void
306hastd_secondary(struct hast_resource *res, struct nv *nvin)
307{
308	pthread_t td;
309	pid_t pid;
310	int error;
311
312	/*
313	 * Create communication channel between parent and child.
314	 */
315	if (proto_client("socketpair://", &res->hr_ctrl) < 0) {
316		KEEP_ERRNO((void)pidfile_remove(pfh));
317		pjdlog_exit(EX_OSERR,
318		    "Unable to create control sockets between parent and child");
319	}
320
321	pid = fork();
322	if (pid < 0) {
323		KEEP_ERRNO((void)pidfile_remove(pfh));
324		pjdlog_exit(EX_OSERR, "Unable to fork");
325	}
326
327	if (pid > 0) {
328		/* This is parent. */
329		proto_close(res->hr_remotein);
330		res->hr_remotein = NULL;
331		proto_close(res->hr_remoteout);
332		res->hr_remoteout = NULL;
333		res->hr_workerpid = pid;
334		return;
335	}
336	(void)pidfile_close(pfh);
337
338	setproctitle("%s (secondary)", res->hr_name);
339
340	/* Error in setting timeout is not critical, but why should it fail? */
341	if (proto_timeout(res->hr_remotein, 0) < 0)
342		pjdlog_errno(LOG_WARNING, "Unable to set connection timeout");
343	if (proto_timeout(res->hr_remoteout, res->hr_timeout) < 0)
344		pjdlog_errno(LOG_WARNING, "Unable to set connection timeout");
345
346	init_local(res);
347	init_remote(res, nvin);
348	init_environment();
349
350	error = pthread_create(&td, NULL, recv_thread, res);
351	assert(error == 0);
352	error = pthread_create(&td, NULL, disk_thread, res);
353	assert(error == 0);
354	error = pthread_create(&td, NULL, send_thread, res);
355	assert(error == 0);
356	(void)ctrl_thread(res);
357}
358
359static void
360reqlog(int loglevel, int debuglevel, int error, struct hio *hio, const char *fmt, ...)
361{
362	char msg[1024];
363	va_list ap;
364	int len;
365
366	va_start(ap, fmt);
367	len = vsnprintf(msg, sizeof(msg), fmt, ap);
368	va_end(ap);
369	if ((size_t)len < sizeof(msg)) {
370		switch (hio->hio_cmd) {
371		case HIO_READ:
372			(void)snprintf(msg + len, sizeof(msg) - len,
373			    "READ(%ju, %ju).", (uintmax_t)hio->hio_offset,
374			    (uintmax_t)hio->hio_length);
375			break;
376		case HIO_DELETE:
377			(void)snprintf(msg + len, sizeof(msg) - len,
378			    "DELETE(%ju, %ju).", (uintmax_t)hio->hio_offset,
379			    (uintmax_t)hio->hio_length);
380			break;
381		case HIO_FLUSH:
382			(void)snprintf(msg + len, sizeof(msg) - len, "FLUSH.");
383			break;
384		case HIO_WRITE:
385			(void)snprintf(msg + len, sizeof(msg) - len,
386			    "WRITE(%ju, %ju).", (uintmax_t)hio->hio_offset,
387			    (uintmax_t)hio->hio_length);
388			break;
389		default:
390			(void)snprintf(msg + len, sizeof(msg) - len,
391			    "UNKNOWN(%u).", (unsigned int)hio->hio_cmd);
392			break;
393		}
394	}
395	pjdlog_common(loglevel, debuglevel, error, "%s", msg);
396}
397
398static int
399requnpack(struct hast_resource *res, struct hio *hio)
400{
401
402	hio->hio_cmd = nv_get_uint8(hio->hio_nv, "cmd");
403	if (hio->hio_cmd == 0) {
404		pjdlog_error("Header contains no 'cmd' field.");
405		hio->hio_error = EINVAL;
406		goto end;
407	}
408	switch (hio->hio_cmd) {
409	case HIO_READ:
410	case HIO_WRITE:
411	case HIO_DELETE:
412		hio->hio_offset = nv_get_uint64(hio->hio_nv, "offset");
413		if (nv_error(hio->hio_nv) != 0) {
414			pjdlog_error("Header is missing 'offset' field.");
415			hio->hio_error = EINVAL;
416			goto end;
417		}
418		hio->hio_length = nv_get_uint64(hio->hio_nv, "length");
419		if (nv_error(hio->hio_nv) != 0) {
420			pjdlog_error("Header is missing 'length' field.");
421			hio->hio_error = EINVAL;
422			goto end;
423		}
424		if (hio->hio_length == 0) {
425			pjdlog_error("Data length is zero.");
426			hio->hio_error = EINVAL;
427			goto end;
428		}
429		if (hio->hio_length > MAXPHYS) {
430			pjdlog_error("Data length is too large (%ju > %ju).",
431			    (uintmax_t)hio->hio_length, (uintmax_t)MAXPHYS);
432			hio->hio_error = EINVAL;
433			goto end;
434		}
435		if ((hio->hio_offset % res->hr_local_sectorsize) != 0) {
436			pjdlog_error("Offset %ju is not multiple of sector size.",
437			    (uintmax_t)hio->hio_offset);
438			hio->hio_error = EINVAL;
439			goto end;
440		}
441		if ((hio->hio_length % res->hr_local_sectorsize) != 0) {
442			pjdlog_error("Length %ju is not multiple of sector size.",
443			    (uintmax_t)hio->hio_length);
444			hio->hio_error = EINVAL;
445			goto end;
446		}
447		if (hio->hio_offset + hio->hio_length >
448		    (uint64_t)res->hr_datasize) {
449			pjdlog_error("Data offset is too large (%ju > %ju).",
450			    (uintmax_t)(hio->hio_offset + hio->hio_length),
451			    (uintmax_t)res->hr_datasize);
452			hio->hio_error = EINVAL;
453			goto end;
454		}
455		break;
456	default:
457		pjdlog_error("Header contains invalid 'cmd' (%hhu).",
458		    hio->hio_cmd);
459		hio->hio_error = EINVAL;
460		goto end;
461	}
462	hio->hio_error = 0;
463end:
464	return (hio->hio_error);
465}
466
467/*
468 * Thread receives requests from the primary node.
469 */
470static void *
471recv_thread(void *arg)
472{
473	struct hast_resource *res = arg;
474	struct hio *hio;
475	bool wakeup;
476
477	for (;;) {
478		pjdlog_debug(2, "recv: Taking free request.");
479		mtx_lock(&hio_free_list_lock);
480		while ((hio = TAILQ_FIRST(&hio_free_list)) == NULL) {
481			pjdlog_debug(2, "recv: No free requests, waiting.");
482			cv_wait(&hio_free_list_cond, &hio_free_list_lock);
483		}
484		TAILQ_REMOVE(&hio_free_list, hio, hio_next);
485		mtx_unlock(&hio_free_list_lock);
486		pjdlog_debug(2, "recv: (%p) Got request.", hio);
487		if (hast_proto_recv_hdr(res->hr_remotein, &hio->hio_nv) < 0) {
488			pjdlog_exit(EX_TEMPFAIL,
489			    "Unable to receive request header");
490		}
491		if (requnpack(res, hio) != 0)
492			goto send_queue;
493		reqlog(LOG_DEBUG, 2, -1, hio,
494		    "recv: (%p) Got request header: ", hio);
495		if (hio->hio_cmd == HIO_WRITE) {
496			if (hast_proto_recv_data(res, res->hr_remotein,
497			    hio->hio_nv, hio->hio_data, MAXPHYS) < 0) {
498				pjdlog_exit(EX_TEMPFAIL,
499				    "Unable to receive reply data");
500			}
501		}
502		pjdlog_debug(2, "recv: (%p) Moving request to the disk queue.",
503		    hio);
504		mtx_lock(&hio_disk_list_lock);
505		wakeup = TAILQ_EMPTY(&hio_disk_list);
506		TAILQ_INSERT_TAIL(&hio_disk_list, hio, hio_next);
507		mtx_unlock(&hio_disk_list_lock);
508		if (wakeup)
509			cv_signal(&hio_disk_list_cond);
510		continue;
511send_queue:
512		pjdlog_debug(2, "recv: (%p) Moving request to the send queue.",
513		    hio);
514		mtx_lock(&hio_send_list_lock);
515		wakeup = TAILQ_EMPTY(&hio_send_list);
516		TAILQ_INSERT_TAIL(&hio_send_list, hio, hio_next);
517		mtx_unlock(&hio_send_list_lock);
518		if (wakeup)
519			cv_signal(&hio_send_list_cond);
520	}
521	/* NOTREACHED */
522	return (NULL);
523}
524
525/*
526 * Thread reads from or writes to local component and also handles DELETE and
527 * FLUSH requests.
528 */
529static void *
530disk_thread(void *arg)
531{
532	struct hast_resource *res = arg;
533	struct hio *hio;
534	ssize_t ret;
535	bool clear_activemap, wakeup;
536
537	clear_activemap = true;
538
539	for (;;) {
540		pjdlog_debug(2, "disk: Taking request.");
541		mtx_lock(&hio_disk_list_lock);
542		while ((hio = TAILQ_FIRST(&hio_disk_list)) == NULL) {
543			pjdlog_debug(2, "disk: No requests, waiting.");
544			cv_wait(&hio_disk_list_cond, &hio_disk_list_lock);
545		}
546		TAILQ_REMOVE(&hio_disk_list, hio, hio_next);
547		mtx_unlock(&hio_disk_list_lock);
548		while (clear_activemap) {
549			unsigned char *map;
550			size_t mapsize;
551
552			/*
553			 * When first request is received, it means that primary
554			 * already received our activemap, merged it and stored
555			 * locally. We can now safely clear our activemap.
556			 */
557			mapsize =
558			    activemap_calc_ondisk_size(res->hr_local_mediasize -
559			    METADATA_SIZE, res->hr_extentsize,
560			    res->hr_local_sectorsize);
561			map = calloc(1, mapsize);
562			if (map == NULL) {
563				pjdlog_warning("Unable to allocate memory to clear local activemap.");
564				break;
565			}
566			if (pwrite(res->hr_localfd, map, mapsize,
567			    METADATA_SIZE) != (ssize_t)mapsize) {
568				pjdlog_errno(LOG_WARNING,
569				    "Unable to store cleared activemap");
570				free(map);
571				break;
572			}
573			free(map);
574			clear_activemap = false;
575			pjdlog_debug(1, "Local activemap cleared.");
576		}
577		reqlog(LOG_DEBUG, 2, -1, hio, "disk: (%p) Got request: ", hio);
578		/* Handle the actual request. */
579		switch (hio->hio_cmd) {
580		case HIO_READ:
581			ret = pread(res->hr_localfd, hio->hio_data,
582			    hio->hio_length,
583			    hio->hio_offset + res->hr_localoff);
584			if (ret < 0)
585				hio->hio_error = errno;
586			else if (ret != (int64_t)hio->hio_length)
587				hio->hio_error = EIO;
588			else
589				hio->hio_error = 0;
590			break;
591		case HIO_WRITE:
592			ret = pwrite(res->hr_localfd, hio->hio_data,
593			    hio->hio_length,
594			    hio->hio_offset + res->hr_localoff);
595			if (ret < 0)
596				hio->hio_error = errno;
597			else if (ret != (int64_t)hio->hio_length)
598				hio->hio_error = EIO;
599			else
600				hio->hio_error = 0;
601			break;
602		case HIO_DELETE:
603			ret = g_delete(res->hr_localfd,
604			    hio->hio_offset + res->hr_localoff,
605			    hio->hio_length);
606			if (ret < 0)
607				hio->hio_error = errno;
608			else
609				hio->hio_error = 0;
610			break;
611		case HIO_FLUSH:
612			ret = g_flush(res->hr_localfd);
613			if (ret < 0)
614				hio->hio_error = errno;
615			else
616				hio->hio_error = 0;
617			break;
618		}
619		if (hio->hio_error != 0) {
620			reqlog(LOG_ERR, 0, hio->hio_error, hio,
621			    "Request failed: ");
622		}
623		pjdlog_debug(2, "disk: (%p) Moving request to the send queue.",
624		    hio);
625		mtx_lock(&hio_send_list_lock);
626		wakeup = TAILQ_EMPTY(&hio_send_list);
627		TAILQ_INSERT_TAIL(&hio_send_list, hio, hio_next);
628		mtx_unlock(&hio_send_list_lock);
629		if (wakeup)
630			cv_signal(&hio_send_list_cond);
631	}
632	/* NOTREACHED */
633	return (NULL);
634}
635
636/*
637 * Thread sends requests back to primary node.
638 */
639static void *
640send_thread(void *arg)
641{
642	struct hast_resource *res = arg;
643	struct nv *nvout;
644	struct hio *hio;
645	void *data;
646	size_t length;
647	bool wakeup;
648
649	for (;;) {
650		pjdlog_debug(2, "send: Taking request.");
651		mtx_lock(&hio_send_list_lock);
652		while ((hio = TAILQ_FIRST(&hio_send_list)) == NULL) {
653			pjdlog_debug(2, "send: No requests, waiting.");
654			cv_wait(&hio_send_list_cond, &hio_send_list_lock);
655		}
656		TAILQ_REMOVE(&hio_send_list, hio, hio_next);
657		mtx_unlock(&hio_send_list_lock);
658		reqlog(LOG_DEBUG, 2, -1, hio, "send: (%p) Got request: ", hio);
659		nvout = nv_alloc();
660		/* Copy sequence number. */
661		nv_add_uint64(nvout, nv_get_uint64(hio->hio_nv, "seq"), "seq");
662		switch (hio->hio_cmd) {
663		case HIO_READ:
664			if (hio->hio_error == 0) {
665				data = hio->hio_data;
666				length = hio->hio_length;
667				break;
668			}
669			/*
670			 * We send no data in case of an error.
671			 */
672			/* FALLTHROUGH */
673		case HIO_DELETE:
674		case HIO_FLUSH:
675		case HIO_WRITE:
676			data = NULL;
677			length = 0;
678			break;
679		default:
680			abort();
681			break;
682		}
683		if (hio->hio_error != 0)
684			nv_add_int16(nvout, hio->hio_error, "error");
685		if (hast_proto_send(res, res->hr_remoteout, nvout, data,
686		    length) < 0) {
687			pjdlog_exit(EX_TEMPFAIL, "Unable to send reply.");
688		}
689		nv_free(nvout);
690		pjdlog_debug(2, "disk: (%p) Moving request to the free queue.",
691		    hio);
692		nv_free(hio->hio_nv);
693		hio->hio_error = 0;
694		mtx_lock(&hio_free_list_lock);
695		wakeup = TAILQ_EMPTY(&hio_free_list);
696		TAILQ_INSERT_TAIL(&hio_free_list, hio, hio_next);
697		mtx_unlock(&hio_free_list_lock);
698		if (wakeup)
699			cv_signal(&hio_free_list_cond);
700	}
701	/* NOTREACHED */
702	return (NULL);
703}
704