1 /*
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 2022 Tomohiro Kusumi <tkusumi@netbsd.org>
5  * Copyright (c) 2011-2022 The DragonFly Project.  All rights reserved.
6  *
7  * This code is derived from software contributed to The DragonFly Project
8  * by Matthew Dillon <dillon@dragonflybsd.org>
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  *
14  * 1. Redistributions of source code must retain the above copyright
15  *    notice, this list of conditions and the following disclaimer.
16  * 2. Redistributions in binary form must reproduce the above copyright
17  *    notice, this list of conditions and the following disclaimer in
18  *    the documentation and/or other materials provided with the
19  *    distribution.
20  * 3. Neither the name of The DragonFly Project nor the names of its
21  *    contributors may be used to endorse or promote products derived
22  *    from this software without specific, prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
25  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
26  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
27  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
28  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
29  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
30  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
31  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
32  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
33  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
34  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35  * SUCH DAMAGE.
36  */
37 /*
38  * This module implements the hammer2 helper thread API, including
39  * the frontend/backend XOP API.
40  */
41 #include "hammer2.h"
42 
43 #define H2XOPDESCRIPTOR(label)					\
44 	hammer2_xop_desc_t hammer2_##label##_desc = {		\
45 		.storage_func = hammer2_xop_##label,		\
46 		.id = #label					\
47 	}
48 
49 H2XOPDESCRIPTOR(ipcluster);
50 H2XOPDESCRIPTOR(readdir);
51 H2XOPDESCRIPTOR(nresolve);
52 H2XOPDESCRIPTOR(unlink);
53 H2XOPDESCRIPTOR(nrename);
54 H2XOPDESCRIPTOR(scanlhc);
55 H2XOPDESCRIPTOR(scanall);
56 H2XOPDESCRIPTOR(lookup);
57 H2XOPDESCRIPTOR(delete);
58 H2XOPDESCRIPTOR(inode_mkdirent);
59 H2XOPDESCRIPTOR(inode_create);
60 H2XOPDESCRIPTOR(inode_create_det);
61 H2XOPDESCRIPTOR(inode_create_ins);
62 H2XOPDESCRIPTOR(inode_destroy);
63 H2XOPDESCRIPTOR(inode_chain_sync);
64 H2XOPDESCRIPTOR(inode_unlinkall);
65 H2XOPDESCRIPTOR(inode_connect);
66 H2XOPDESCRIPTOR(inode_flush);
67 H2XOPDESCRIPTOR(strategy_read);
68 H2XOPDESCRIPTOR(strategy_write);
69 
70 //struct objcache *cache_xops;
71 static struct thread dummy_td;
72 struct thread *curthread = &dummy_td;
73 
74 /*
75  * Set flags and wakeup any waiters.
76  *
77  * WARNING! During teardown (thr) can disappear the instant our cmpset
78  *	    succeeds.
79  */
80 void
81 hammer2_thr_signal(hammer2_thread_t *thr, uint32_t flags)
82 {
83 	uint32_t oflags;
84 	uint32_t nflags;
85 
86 	for (;;) {
87 		oflags = thr->flags;
88 		cpu_ccfence();
89 		nflags = (oflags | flags) & ~HAMMER2_THREAD_WAITING;
90 
91 		if (oflags & HAMMER2_THREAD_WAITING) {
92 			if (atomic_cmpset_int(&thr->flags, oflags, nflags)) {
93 				wakeup(&thr->flags);
94 				break;
95 			}
96 		} else {
97 			if (atomic_cmpset_int(&thr->flags, oflags, nflags))
98 				break;
99 		}
100 	}
101 }
102 
103 /*
104  * Set and clear flags and wakeup any waiters.
105  *
106  * WARNING! During teardown (thr) can disappear the instant our cmpset
107  *	    succeeds.
108  */
109 void
110 hammer2_thr_signal2(hammer2_thread_t *thr, uint32_t posflags, uint32_t negflags)
111 {
112 	uint32_t oflags;
113 	uint32_t nflags;
114 
115 	for (;;) {
116 		oflags = thr->flags;
117 		cpu_ccfence();
118 		nflags = (oflags | posflags) &
119 			~(negflags | HAMMER2_THREAD_WAITING);
120 		if (oflags & HAMMER2_THREAD_WAITING) {
121 			if (atomic_cmpset_int(&thr->flags, oflags, nflags)) {
122 				wakeup(&thr->flags);
123 				break;
124 			}
125 		} else {
126 			if (atomic_cmpset_int(&thr->flags, oflags, nflags))
127 				break;
128 		}
129 	}
130 }
131 
132 /*
133  * Wait until all the bits in flags are set.
134  *
135  * WARNING! During teardown (thr) can disappear the instant our cmpset
136  *	    succeeds.
137  */
138 void
139 hammer2_thr_wait(hammer2_thread_t *thr, uint32_t flags)
140 {
141 	uint32_t oflags;
142 	uint32_t nflags;
143 
144 	for (;;) {
145 		oflags = thr->flags;
146 		cpu_ccfence();
147 		if ((oflags & flags) == flags)
148 			break;
149 		nflags = oflags | HAMMER2_THREAD_WAITING;
150 		tsleep_interlock(&thr->flags, 0);
151 		if (atomic_cmpset_int(&thr->flags, oflags, nflags)) {
152 			tsleep(&thr->flags, PINTERLOCKED, "h2twait", hz*60);
153 		}
154 	}
155 }
156 
157 /*
158  * Wait until any of the bits in flags are set, with timeout.
159  *
160  * WARNING! During teardown (thr) can disappear the instant our cmpset
161  *	    succeeds.
162  */
163 int
164 hammer2_thr_wait_any(hammer2_thread_t *thr, uint32_t flags, int timo)
165 {
166 	uint32_t oflags;
167 	uint32_t nflags;
168 	int error;
169 
170 	error = 0;
171 	for (;;) {
172 		oflags = thr->flags;
173 		cpu_ccfence();
174 		if (oflags & flags)
175 			break;
176 		nflags = oflags | HAMMER2_THREAD_WAITING;
177 		tsleep_interlock(&thr->flags, 0);
178 		if (atomic_cmpset_int(&thr->flags, oflags, nflags)) {
179 			error = tsleep(&thr->flags, PINTERLOCKED,
180 				       "h2twait", timo);
181 		}
182 		if (error == ETIMEDOUT) {
183 			error = HAMMER2_ERROR_ETIMEDOUT;
184 			break;
185 		}
186 	}
187 	return error;
188 }
189 
190 /*
191  * Wait until the bits in flags are clear.
192  *
193  * WARNING! During teardown (thr) can disappear the instant our cmpset
194  *	    succeeds.
195  */
196 void
197 hammer2_thr_wait_neg(hammer2_thread_t *thr, uint32_t flags)
198 {
199 	uint32_t oflags;
200 	uint32_t nflags;
201 
202 	for (;;) {
203 		oflags = thr->flags;
204 		cpu_ccfence();
205 		if ((oflags & flags) == 0)
206 			break;
207 		nflags = oflags | HAMMER2_THREAD_WAITING;
208 		tsleep_interlock(&thr->flags, 0);
209 		if (atomic_cmpset_int(&thr->flags, oflags, nflags)) {
210 			tsleep(&thr->flags, PINTERLOCKED, "h2twait", hz*60);
211 		}
212 	}
213 }
214 
215 /*
216  * Initialize the supplied thread structure, starting the specified
217  * thread.
218  *
219  * NOTE: thr structure can be retained across mounts and unmounts for this
220  *	 pmp, so make sure the flags are in a sane state.
221  */
222 void
223 hammer2_thr_create(hammer2_thread_t *thr, hammer2_pfs_t *pmp,
224 		   hammer2_dev_t *hmp,
225 		   const char *id, int clindex, int repidx,
226 		   void (*func)(void *arg))
227 {
228 	thr->pmp = pmp;		/* xop helpers */
229 	thr->hmp = hmp;		/* bulkfree */
230 	thr->clindex = clindex;
231 	thr->repidx = repidx;
232 	TAILQ_INIT(&thr->xopq);
233 	atomic_clear_int(&thr->flags, HAMMER2_THREAD_STOP |
234 				      HAMMER2_THREAD_STOPPED |
235 				      HAMMER2_THREAD_FREEZE |
236 				      HAMMER2_THREAD_FROZEN);
237 	if (thr->scratch == NULL)
238 		thr->scratch = kmalloc(MAXPHYS, M_HAMMER2, M_WAITOK | M_ZERO);
239 #if 0
240 	if (repidx >= 0) {
241 		lwkt_create(func, thr, &thr->td, NULL, 0, repidx % ncpus,
242 			    "%s-%s.%02d", id, pmp->pfs_names[clindex], repidx);
243 	} else if (pmp) {
244 		lwkt_create(func, thr, &thr->td, NULL, 0, -1,
245 			    "%s-%s", id, pmp->pfs_names[clindex]);
246 	} else {
247 		lwkt_create(func, thr, &thr->td, NULL, 0, -1, "%s", id);
248 	}
249 #else
250 	thr->td = &dummy_td;
251 #endif
252 }
253 
254 /*
255  * Terminate a thread.  This function will silently return if the thread
256  * was never initialized or has already been deleted.
257  *
258  * This is accomplished by setting the STOP flag and waiting for the td
259  * structure to become NULL.
260  */
261 void
262 hammer2_thr_delete(hammer2_thread_t *thr)
263 {
264 	if (thr->td == NULL)
265 		return;
266 	hammer2_thr_signal(thr, HAMMER2_THREAD_STOP);
267 	/* Don't wait, there's no such thread in makefs */
268 	//hammer2_thr_wait(thr, HAMMER2_THREAD_STOPPED);
269 	thr->pmp = NULL;
270 	if (thr->scratch) {
271 		kfree(thr->scratch, M_HAMMER2);
272 		thr->scratch = NULL;
273 	}
274 	KKASSERT(TAILQ_EMPTY(&thr->xopq));
275 }
276 
277 /*
278  * Asynchronous remaster request.  Ask the synchronization thread to
279  * start over soon (as if it were frozen and unfrozen, but without waiting).
280  * The thread always recalculates mastership relationships when restarting.
281  */
282 void
283 hammer2_thr_remaster(hammer2_thread_t *thr)
284 {
285 	if (thr->td == NULL)
286 		return;
287 	hammer2_thr_signal(thr, HAMMER2_THREAD_REMASTER);
288 }
289 
290 void
291 hammer2_thr_freeze_async(hammer2_thread_t *thr)
292 {
293 	hammer2_thr_signal(thr, HAMMER2_THREAD_FREEZE);
294 }
295 
296 void
297 hammer2_thr_freeze(hammer2_thread_t *thr)
298 {
299 	if (thr->td == NULL)
300 		return;
301 	hammer2_thr_signal(thr, HAMMER2_THREAD_FREEZE);
302 	hammer2_thr_wait(thr, HAMMER2_THREAD_FROZEN);
303 }
304 
305 void
306 hammer2_thr_unfreeze(hammer2_thread_t *thr)
307 {
308 	if (thr->td == NULL)
309 		return;
310 	hammer2_thr_signal(thr, HAMMER2_THREAD_UNFREEZE);
311 	hammer2_thr_wait_neg(thr, HAMMER2_THREAD_FROZEN);
312 }
313 
314 int
315 hammer2_thr_break(hammer2_thread_t *thr)
316 {
317 	if (thr->flags & (HAMMER2_THREAD_STOP |
318 			  HAMMER2_THREAD_REMASTER |
319 			  HAMMER2_THREAD_FREEZE)) {
320 		return 1;
321 	}
322 	return 0;
323 }
324 
325 /****************************************************************************
326  *			    HAMMER2 XOPS API	 			    *
327  ****************************************************************************/
328 
329 /*
330  * Allocate or reallocate XOP FIFO.  This doesn't exist in sys/vfs/hammer2
331  * where XOP is handled by dedicated kernel threads and when FIFO stalls
332  * threads wait for frontend to collect results.
333  */
334 static void
335 hammer2_xop_fifo_alloc(hammer2_xop_fifo_t *fifo, size_t nmemb)
336 {
337 	size_t size;
338 
339 	/* Assert nmemb requirements. */
340 	KKASSERT((nmemb & (nmemb - 1)) == 0);
341 	KKASSERT(nmemb >= HAMMER2_XOPFIFO);
342 
343 	/* malloc or realloc fifo array. */
344 	size = nmemb * sizeof(hammer2_chain_t *);
345 	if (!fifo->array)
346 		fifo->array = kmalloc(size, M_HAMMER2, M_WAITOK | M_ZERO);
347 	else
348 		fifo->array = krealloc(fifo->array, size, M_HAMMER2,
349 		    M_WAITOK | M_ZERO);
350 	KKASSERT(fifo->array);
351 
352 	/* malloc or realloc fifo errors. */
353 	size = nmemb * sizeof(int);
354 	if (!fifo->errors)
355 		fifo->errors = kmalloc(size, M_HAMMER2, M_WAITOK | M_ZERO);
356 	else
357 		fifo->errors = krealloc(fifo->errors, size, M_HAMMER2,
358 		    M_WAITOK | M_ZERO);
359 	KKASSERT(fifo->errors);
360 }
361 
362 /*
363  * Allocate a XOP request.
364  *
365  * Once allocated a XOP request can be started, collected, and retired,
366  * and can be retired early if desired.
367  *
368  * NOTE: Fifo indices might not be zero but ri == wi on objcache_get().
369  */
370 void *
371 hammer2_xop_alloc(hammer2_inode_t *ip, int flags)
372 {
373 	hammer2_xop_t *xop;
374 
375 	xop = ecalloc(1, sizeof(*xop));
376 	KKASSERT(xop->head.cluster.array[0].chain == NULL);
377 
378 	xop->head.ip1 = ip;
379 	xop->head.desc = NULL;
380 	xop->head.flags = flags;
381 	xop->head.state = 0;
382 	xop->head.error = 0;
383 	xop->head.collect_key = 0;
384 	xop->head.focus_dio = NULL;
385 
386 	if (flags & HAMMER2_XOP_MODIFYING)
387 		xop->head.mtid = hammer2_trans_sub(ip->pmp);
388 	else
389 		xop->head.mtid = 0;
390 
391 	xop->head.cluster.nchains = ip->cluster.nchains;
392 	xop->head.cluster.pmp = ip->pmp;
393 	xop->head.cluster.flags = HAMMER2_CLUSTER_LOCKED;
394 
395 	/*
396 	 * run_mask - Active thread (or frontend) associated with XOP
397 	 */
398 	xop->head.run_mask = HAMMER2_XOPMASK_VOP;
399 
400 	hammer2_xop_fifo_t *fifo = &xop->head.collect[0];
401 	xop->head.fifo_size = HAMMER2_XOPFIFO;
402 	hammer2_xop_fifo_alloc(fifo, xop->head.fifo_size);
403 
404 	hammer2_inode_ref(ip);
405 
406 	return xop;
407 }
408 
409 void
410 hammer2_xop_setname(hammer2_xop_head_t *xop, const char *name, size_t name_len)
411 {
412 	xop->name1 = kmalloc(name_len + 1, M_HAMMER2, M_WAITOK | M_ZERO);
413 	xop->name1_len = name_len;
414 	bcopy(name, xop->name1, name_len);
415 }
416 
417 void
418 hammer2_xop_setname2(hammer2_xop_head_t *xop, const char *name, size_t name_len)
419 {
420 	xop->name2 = kmalloc(name_len + 1, M_HAMMER2, M_WAITOK | M_ZERO);
421 	xop->name2_len = name_len;
422 	bcopy(name, xop->name2, name_len);
423 }
424 
425 size_t
426 hammer2_xop_setname_inum(hammer2_xop_head_t *xop, hammer2_key_t inum)
427 {
428 	const size_t name_len = 18;
429 
430 	xop->name1 = kmalloc(name_len + 1, M_HAMMER2, M_WAITOK | M_ZERO);
431 	xop->name1_len = name_len;
432 	ksnprintf(xop->name1, name_len + 1, "0x%016jx", (intmax_t)inum);
433 
434 	return name_len;
435 }
436 
437 
438 void
439 hammer2_xop_setip2(hammer2_xop_head_t *xop, hammer2_inode_t *ip2)
440 {
441 	xop->ip2 = ip2;
442 	hammer2_inode_ref(ip2);
443 }
444 
445 void
446 hammer2_xop_setip3(hammer2_xop_head_t *xop, hammer2_inode_t *ip3)
447 {
448 	xop->ip3 = ip3;
449 	hammer2_inode_ref(ip3);
450 }
451 
452 void
453 hammer2_xop_setip4(hammer2_xop_head_t *xop, hammer2_inode_t *ip4)
454 {
455 	xop->ip4 = ip4;
456 	hammer2_inode_ref(ip4);
457 }
458 
459 void
460 hammer2_xop_reinit(hammer2_xop_head_t *xop)
461 {
462 	xop->state = 0;
463 	xop->error = 0;
464 	xop->collect_key = 0;
465 	xop->run_mask = HAMMER2_XOPMASK_VOP;
466 }
467 
468 /*
469  * A mounted PFS needs Xops threads to support frontend operations.
470  */
471 void
472 hammer2_xop_helper_create(hammer2_pfs_t *pmp)
473 {
474 	int i;
475 	int j;
476 
477 	lockmgr(&pmp->lock, LK_EXCLUSIVE);
478 	pmp->has_xop_threads = 1;
479 
480 	pmp->xop_groups = kmalloc(hammer2_xop_nthreads *
481 				  sizeof(hammer2_xop_group_t),
482 				  M_HAMMER2, M_WAITOK | M_ZERO);
483 	for (i = 0; i < pmp->iroot->cluster.nchains; ++i) {
484 		for (j = 0; j < hammer2_xop_nthreads; ++j) {
485 			if (pmp->xop_groups[j].thrs[i].td)
486 				continue;
487 			hammer2_thr_create(&pmp->xop_groups[j].thrs[i],
488 					   pmp, NULL,
489 					   "h2xop", i, j,
490 					   hammer2_primary_xops_thread);
491 		}
492 	}
493 	lockmgr(&pmp->lock, LK_RELEASE);
494 }
495 
496 void
497 hammer2_xop_helper_cleanup(hammer2_pfs_t *pmp)
498 {
499 	int i;
500 	int j;
501 
502 	if (pmp->xop_groups == NULL) {
503 		KKASSERT(pmp->has_xop_threads == 0);
504 		return;
505 	}
506 
507 	for (i = 0; i < pmp->pfs_nmasters; ++i) {
508 		for (j = 0; j < hammer2_xop_nthreads; ++j) {
509 			if (pmp->xop_groups[j].thrs[i].td)
510 				hammer2_thr_delete(&pmp->xop_groups[j].thrs[i]);
511 		}
512 	}
513 	pmp->has_xop_threads = 0;
514 	kfree(pmp->xop_groups, M_HAMMER2);
515 	pmp->xop_groups = NULL;
516 }
517 
518 /*
519  * Start a XOP request, queueing it to all nodes in the cluster to
520  * execute the cluster op.
521  *
522  * XXX optimize single-target case.
523  */
524 void
525 hammer2_xop_start_except(hammer2_xop_head_t *xop, hammer2_xop_desc_t *desc,
526 			 int notidx)
527 {
528 	hammer2_inode_t *ip1;
529 	hammer2_pfs_t *pmp;
530 	hammer2_thread_t *thr;
531 	int i;
532 	int ng;
533 	int nchains;
534 
535 	ip1 = xop->ip1;
536 	pmp = ip1->pmp;
537 	if (pmp->has_xop_threads == 0)
538 		hammer2_xop_helper_create(pmp);
539 
540 	/*
541 	 * The sequencer assigns a worker thread to the XOP.
542 	 *
543 	 * (1) The worker threads are partitioned into two sets, one for
544 	 *     NON-STRATEGY XOPs, and the other for STRATEGY XOPs.  This
545 	 *     guarantees that strategy calls will always be able to make
546 	 *     progress and will not deadlock against non-strategy calls.
547 	 *
548 	 * (2) If clustered, non-strategy operations to the same inode must
549 	 *     be serialized.  This is to avoid confusion when issuing
550 	 *     modifying operations because a XOP completes the instant a
551 	 *     quorum is reached.
552 	 *
553 	 * TODO - RENAME fails here because it is potentially modifying
554 	 *	  three different inodes, but we triple-lock the inodes
555 	 *	  involved so it shouldn't create a sequencing schism.
556 	 */
557 	if (xop->flags & HAMMER2_XOP_STRATEGY) {
558 		/*
559 		 * Use worker space 0 associated with the current cpu
560 		 * for strategy ops.
561 		 */
562 		/*
563 		hammer2_xop_strategy_t *xopst;
564 		u_int which;
565 
566 		xopst = &((hammer2_xop_t *)xop)->xop_strategy;
567 		which = ((unsigned int)ip1->ihash +
568 			 ((unsigned int)xopst->lbase >> HAMMER2_PBUFRADIX)) %
569 			hammer2_xop_sgroups;
570 		ng = mycpu->gd_cpuid % hammer2_xop_mod +
571 		     hammer2_xop_mod * which;
572 		*/
573 		ng = 0;
574 	} else if (hammer2_spread_workers == 0 && ip1->cluster.nchains == 1) {
575 		/*
576 		 * For now try to keep the work on the same cpu to reduce
577 		 * IPI overhead.  Several threads are assigned to each cpu,
578 		 * don't be very smart and select the one to use based on
579 		 * the inode hash.
580 		 */
581 		/*
582 		u_int which;
583 
584 		which = (unsigned int)ip1->ihash % hammer2_xop_xgroups;
585 		ng = mycpu->gd_cpuid % hammer2_xop_mod +
586 		     (which * hammer2_xop_mod) +
587 		     hammer2_xop_xbase;
588 		*/
589 		ng = 0;
590 	} else {
591 		/*
592 		 * Hash based on inode only, must serialize inode to same
593 		 * thread regardless of current cpu.
594 		 */
595 		/*
596 		ng = (unsigned int)ip1->ihash %
597 		     (hammer2_xop_mod * hammer2_xop_xgroups) +
598 		     hammer2_xop_xbase;
599 		*/
600 		ng = 0;
601 	}
602 	xop->desc = desc;
603 
604 	/*
605 	 * The instant xop is queued another thread can pick it off.  In the
606 	 * case of asynchronous ops, another thread might even finish and
607 	 * deallocate it.
608 	 */
609 	hammer2_spin_ex(&pmp->xop_spin);
610 	nchains = ip1->cluster.nchains;
611 	for (i = 0; i < nchains; ++i) {
612 		/*
613 		 * XXX ip1->cluster.array* not stable here.  This temporary
614 		 *     hack fixes basic issues in target XOPs which need to
615 		 *     obtain a starting chain from the inode but does not
616 		 *     address possible races against inode updates which
617 		 *     might NULL-out a chain.
618 		 */
619 		if (i != notidx && ip1->cluster.array[i].chain) {
620 			thr = &pmp->xop_groups[ng].thrs[i];
621 			atomic_set_64(&xop->run_mask, 1LLU << i);
622 			atomic_set_64(&xop->chk_mask, 1LLU << i);
623 			xop->collect[i].thr = thr;
624 			TAILQ_INSERT_TAIL(&thr->xopq, xop, collect[i].entry);
625 		}
626 	}
627 	hammer2_spin_unex(&pmp->xop_spin);
628 	/* xop can become invalid at this point */
629 
630 	/*
631 	 * Each thread has its own xopq
632 	 */
633 	for (i = 0; i < nchains; ++i) {
634 		if (i != notidx) {
635 			thr = &pmp->xop_groups[ng].thrs[i];
636 			hammer2_thr_signal(thr, HAMMER2_THREAD_XOPQ);
637 			hammer2_primary_xops_thread(thr);
638 		}
639 	}
640 }
641 
642 void
643 hammer2_xop_start(hammer2_xop_head_t *xop, hammer2_xop_desc_t *desc)
644 {
645 	hammer2_xop_start_except(xop, desc, -1);
646 }
647 
648 /*
649  * Retire a XOP.  Used by both the VOP frontend and by the XOP backend.
650  */
651 void
652 hammer2_xop_retire(hammer2_xop_head_t *xop, uint64_t mask)
653 {
654 	hammer2_chain_t *chain;
655 	uint64_t nmask;
656 	int i;
657 
658 	/*
659 	 * Remove the frontend collector or remove a backend feeder.
660 	 *
661 	 * When removing the frontend we must wakeup any backend feeders
662 	 * who are waiting for FIFO space.
663 	 *
664 	 * When removing the last backend feeder we must wakeup any waiting
665 	 * frontend.
666 	 */
667 	KKASSERT(xop->run_mask & mask);
668 	nmask = atomic_fetchadd_64(&xop->run_mask,
669 				   -mask + HAMMER2_XOPMASK_FEED);
670 
671 	/*
672 	 * More than one entity left
673 	 */
674 	if ((nmask & HAMMER2_XOPMASK_ALLDONE) != mask) {
675 		/*
676 		 * Frontend terminating, wakeup any backends waiting on
677 		 * fifo full.
678 		 *
679 		 * NOTE!!! The xop can get ripped out from under us at
680 		 *	   this point, so do not reference it again.
681 		 *	   The wakeup(xop) doesn't touch the xop and
682 		 *	   is ok.
683 		 */
684 		if (mask == HAMMER2_XOPMASK_VOP) {
685 			if (nmask & HAMMER2_XOPMASK_FIFOW)
686 				wakeup(xop);
687 		}
688 
689 		/*
690 		 * Wakeup frontend if the last backend is terminating.
691 		 */
692 		nmask -= mask;
693 		if ((nmask & HAMMER2_XOPMASK_ALLDONE) == HAMMER2_XOPMASK_VOP) {
694 			if (nmask & HAMMER2_XOPMASK_WAIT)
695 				wakeup(xop);
696 		}
697 
698 		return;
699 	}
700 	/* else nobody else left, we can ignore FIFOW */
701 
702 	/*
703 	 * All collectors are gone, we can cleanup and dispose of the XOP.
704 	 * Note that this can wind up being a frontend OR a backend.
705 	 * Pending chains are locked shared and not owned by any thread.
706 	 *
707 	 * Cleanup the collection cluster.
708 	 */
709 	for (i = 0; i < xop->cluster.nchains; ++i) {
710 		xop->cluster.array[i].flags = 0;
711 		chain = xop->cluster.array[i].chain;
712 		if (chain) {
713 			xop->cluster.array[i].chain = NULL;
714 			hammer2_chain_drop_unhold(chain);
715 		}
716 	}
717 
718 	/*
719 	 * Cleanup the fifos.  Since we are the only entity left on this
720 	 * xop we don't have to worry about fifo flow control, and one
721 	 * lfence() will do the job.
722 	 */
723 	cpu_lfence();
724 	mask = xop->chk_mask;
725 	for (i = 0; mask && i < HAMMER2_MAXCLUSTER; ++i) {
726 		hammer2_xop_fifo_t *fifo = &xop->collect[i];
727 		while (fifo->ri != fifo->wi) {
728 			chain = fifo->array[fifo->ri & fifo_mask(xop)];
729 			if (chain)
730 				hammer2_chain_drop_unhold(chain);
731 			++fifo->ri;
732 		}
733 		mask &= ~(1U << i);
734 	}
735 
736 	/*
737 	 * The inode is only held at this point, simply drop it.
738 	 */
739 	if (xop->ip1) {
740 		hammer2_inode_drop(xop->ip1);
741 		xop->ip1 = NULL;
742 	}
743 	if (xop->ip2) {
744 		hammer2_inode_drop(xop->ip2);
745 		xop->ip2 = NULL;
746 	}
747 	if (xop->ip3) {
748 		hammer2_inode_drop(xop->ip3);
749 		xop->ip3 = NULL;
750 	}
751 	if (xop->ip4) {
752 		hammer2_inode_drop(xop->ip4);
753 		xop->ip4 = NULL;
754 	}
755 	if (xop->name1) {
756 		kfree(xop->name1, M_HAMMER2);
757 		xop->name1 = NULL;
758 		xop->name1_len = 0;
759 	}
760 	if (xop->name2) {
761 		kfree(xop->name2, M_HAMMER2);
762 		xop->name2 = NULL;
763 		xop->name2_len = 0;
764 	}
765 
766 	free(xop);
767 }
768 
769 /*
770  * (Backend) Returns non-zero if the frontend is still attached.
771  */
772 int
773 hammer2_xop_active(hammer2_xop_head_t *xop)
774 {
775 	if (xop->run_mask & HAMMER2_XOPMASK_VOP)
776 		return 1;
777 	else
778 		return 0;
779 }
780 
781 /*
782  * (Backend) Feed chain data through the cluster validator and back to
783  * the frontend.  Chains are fed from multiple nodes concurrently
784  * and pipelined via per-node FIFOs in the XOP.
785  *
786  * The chain must be locked (either shared or exclusive).  The caller may
787  * unlock and drop the chain on return.  This function will add an extra
788  * ref and hold the chain's data for the pass-back.
789  *
790  * No xop lock is needed because we are only manipulating fields under
791  * our direct control.
792  *
793  * Returns 0 on success and a hammer2 error code if sync is permanently
794  * lost.  The caller retains a ref on the chain but by convention
795  * the lock is typically inherited by the xop (caller loses lock).
796  *
797  * Returns non-zero on error.  In this situation the caller retains a
798  * ref on the chain but loses the lock (we unlock here).
799  */
800 int
801 hammer2_xop_feed(hammer2_xop_head_t *xop, hammer2_chain_t *chain,
802 		 int clindex, int error)
803 {
804 	hammer2_xop_fifo_t *fifo;
805 	uint64_t mask;
806 
807 	/*
808 	 * Early termination (typicaly of xop_readir)
809 	 */
810 	if (hammer2_xop_active(xop) == 0) {
811 		error = HAMMER2_ERROR_ABORTED;
812 		goto done;
813 	}
814 
815 	/*
816 	 * Multi-threaded entry into the XOP collector.  We own the
817 	 * fifo->wi for our clindex.
818 	 */
819 	fifo = &xop->collect[clindex];
820 
821 	if (fifo->ri == fifo->wi - HAMMER2_XOPFIFO)
822 		lwkt_yield();
823 	while (fifo->ri == fifo->wi - xop->fifo_size) {
824 		atomic_set_int(&fifo->flags, HAMMER2_XOP_FIFO_STALL);
825 		mask = xop->run_mask;
826 		if ((mask & HAMMER2_XOPMASK_VOP) == 0) {
827 			error = HAMMER2_ERROR_ABORTED;
828 			goto done;
829 		}
830 		xop->fifo_size *= 2;
831 		hammer2_xop_fifo_alloc(fifo, xop->fifo_size);
832 	}
833 	atomic_clear_int(&fifo->flags, HAMMER2_XOP_FIFO_STALL);
834 	if (chain)
835 		hammer2_chain_ref_hold(chain);
836 	if (error == 0 && chain)
837 		error = chain->error;
838 	fifo->errors[fifo->wi & fifo_mask(xop)] = error;
839 	fifo->array[fifo->wi & fifo_mask(xop)] = chain;
840 	cpu_sfence();
841 	++fifo->wi;
842 
843 	mask = atomic_fetchadd_64(&xop->run_mask, HAMMER2_XOPMASK_FEED);
844 	if (mask & HAMMER2_XOPMASK_WAIT) {
845 		atomic_clear_64(&xop->run_mask, HAMMER2_XOPMASK_WAIT);
846 		wakeup(xop);
847 	}
848 	error = 0;
849 
850 	/*
851 	 * Cleanup.  If no error
852 	 * occurred the fifo inherits the lock and gains an additional ref.
853 	 *
854 	 * The caller's ref remains in both cases.
855 	 */
856 done:
857 	return error;
858 }
859 
860 /*
861  * (Frontend) collect a response from a running cluster op.
862  *
863  * Responses are fed from all appropriate nodes concurrently
864  * and collected into a cohesive response >= collect_key.
865  *
866  * The collector will return the instant quorum or other requirements
867  * are met, even if some nodes get behind or become non-responsive.
868  *
869  * HAMMER2_XOP_COLLECT_NOWAIT	- Used to 'poll' a completed collection,
870  *				  usually called synchronously from the
871  *				  node XOPs for the strategy code to
872  *				  fake the frontend collection and complete
873  *				  the BIO as soon as possible.
874  *
875  * Returns 0 on success plus a filled out xop->cluster structure.
876  * Return ENOENT on normal termination.
877  * Otherwise return an error.
878  *
879  * WARNING! If the xop returns a cluster with a non-NULL focus, note that
880  *	    none of the chains in the cluster (or the focus) are either
881  *	    locked or I/O synchronized with the cpu.  hammer2_xop_gdata()
882  *	    and hammer2_xop_pdata() must be used to safely access the focus
883  *	    chain's content.
884  *
885  *	    The frontend can make certain assumptions based on higher-level
886  *	    locking done by the frontend, but data integrity absolutely
887  *	    requires using the gdata/pdata API.
888  */
889 int
890 hammer2_xop_collect(hammer2_xop_head_t *xop, int flags)
891 {
892 	hammer2_xop_fifo_t *fifo;
893 	hammer2_chain_t *chain;
894 	hammer2_key_t lokey;
895 	uint64_t mask;
896 	int error;
897 	int keynull;
898 	int adv;		/* advance the element */
899 	int i;
900 
901 loop:
902 	/*
903 	 * First loop tries to advance pieces of the cluster which
904 	 * are out of sync.
905 	 */
906 	lokey = HAMMER2_KEY_MAX;
907 	keynull = HAMMER2_CHECK_NULL;
908 	mask = xop->run_mask;
909 	cpu_lfence();
910 
911 	for (i = 0; i < xop->cluster.nchains; ++i) {
912 		chain = xop->cluster.array[i].chain;
913 		if (chain == NULL) {
914 			adv = 1;
915 		} else if (chain->bref.key < xop->collect_key) {
916 			adv = 1;
917 		} else {
918 			keynull &= ~HAMMER2_CHECK_NULL;
919 			if (lokey > chain->bref.key)
920 				lokey = chain->bref.key;
921 			adv = 0;
922 		}
923 		if (adv == 0)
924 			continue;
925 
926 		/*
927 		 * Advance element if possible, advanced element may be NULL.
928 		 */
929 		if (chain)
930 			hammer2_chain_drop_unhold(chain);
931 
932 		fifo = &xop->collect[i];
933 		if (fifo->ri != fifo->wi) {
934 			cpu_lfence();
935 			chain = fifo->array[fifo->ri & fifo_mask(xop)];
936 			error = fifo->errors[fifo->ri & fifo_mask(xop)];
937 			++fifo->ri;
938 			xop->cluster.array[i].chain = chain;
939 			xop->cluster.array[i].error = error;
940 			if (chain == NULL) {
941 				/* XXX */
942 				xop->cluster.array[i].flags |=
943 							HAMMER2_CITEM_NULL;
944 			}
945 			if (fifo->wi - fifo->ri <= HAMMER2_XOPFIFO / 2) {
946 				if (fifo->flags & HAMMER2_XOP_FIFO_STALL) {
947 					atomic_clear_int(&fifo->flags,
948 						    HAMMER2_XOP_FIFO_STALL);
949 					wakeup(xop);
950 					lwkt_yield();
951 				}
952 			}
953 			--i;		/* loop on same index */
954 		} else {
955 			/*
956 			 * Retain CITEM_NULL flag.  If set just repeat EOF.
957 			 * If not, the NULL,0 combination indicates an
958 			 * operation in-progress.
959 			 */
960 			xop->cluster.array[i].chain = NULL;
961 			/* retain any CITEM_NULL setting */
962 		}
963 	}
964 
965 	/*
966 	 * Determine whether the lowest collected key meets clustering
967 	 * requirements.  Returns HAMMER2_ERROR_*:
968 	 *
969 	 * 0	 	 - key valid, cluster can be returned.
970 	 *
971 	 * ENOENT	 - normal end of scan, return ENOENT.
972 	 *
973 	 * ESRCH	 - sufficient elements collected, quorum agreement
974 	 *		   that lokey is not a valid element and should be
975 	 *		   skipped.
976 	 *
977 	 * EDEADLK	 - sufficient elements collected, no quorum agreement
978 	 *		   (and no agreement possible).  In this situation a
979 	 *		   repair is needed, for now we loop.
980 	 *
981 	 * EINPROGRESS	 - insufficient elements collected to resolve, wait
982 	 *		   for event and loop.
983 	 *
984 	 * EIO		 - IO error or CRC check error from hammer2_cluster_check()
985 	 */
986 	if ((flags & HAMMER2_XOP_COLLECT_WAITALL) &&
987 	    (mask & HAMMER2_XOPMASK_ALLDONE) != HAMMER2_XOPMASK_VOP) {
988 		error = HAMMER2_ERROR_EINPROGRESS;
989 	} else {
990 		error = hammer2_cluster_check(&xop->cluster, lokey, keynull);
991 	}
992 	if (error == HAMMER2_ERROR_EINPROGRESS) {
993 		if (flags & HAMMER2_XOP_COLLECT_NOWAIT)
994 			goto done;
995 		tsleep_interlock(xop, 0);
996 		if (atomic_cmpset_64(&xop->run_mask,
997 				     mask, mask | HAMMER2_XOPMASK_WAIT)) {
998 			tsleep(xop, PINTERLOCKED, "h2coll", hz*60);
999 		}
1000 		goto loop;
1001 	}
1002 	if (error == HAMMER2_ERROR_ESRCH) {
1003 		if (lokey != HAMMER2_KEY_MAX) {
1004 			xop->collect_key = lokey + 1;
1005 			goto loop;
1006 		}
1007 		error = HAMMER2_ERROR_ENOENT;
1008 	}
1009 	if (error == HAMMER2_ERROR_EDEADLK) {
1010 		kprintf("hammer2: no quorum possible lokey %016jx\n",
1011 			lokey);
1012 		if (lokey != HAMMER2_KEY_MAX) {
1013 			xop->collect_key = lokey + 1;
1014 			goto loop;
1015 		}
1016 		error = HAMMER2_ERROR_ENOENT;
1017 	}
1018 	if (lokey == HAMMER2_KEY_MAX)
1019 		xop->collect_key = lokey;
1020 	else
1021 		xop->collect_key = lokey + 1;
1022 done:
1023 	return error;
1024 }
1025 
1026 /*
1027  * N x M processing threads are available to handle XOPs, N per cluster
1028  * index x M cluster nodes.
1029  *
1030  * Locate and return the next runnable xop, or NULL if no xops are
1031  * present or none of the xops are currently runnable (for various reasons).
1032  * The xop is left on the queue and serves to block other dependent xops
1033  * from being run.
1034  *
1035  * Dependent xops will not be returned.
1036  *
1037  * Sets HAMMER2_XOP_FIFO_RUN on the returned xop or returns NULL.
1038  *
1039  * NOTE! Xops run concurrently for each cluster index.
1040  */
1041 #define XOP_HASH_SIZE	16
1042 #define XOP_HASH_MASK	(XOP_HASH_SIZE - 1)
1043 
1044 static __inline
1045 int
1046 xop_testhash(hammer2_thread_t *thr, hammer2_inode_t *ip, uint32_t *hash)
1047 {
1048 	uint32_t mask;
1049 	int hv;
1050 
1051 	hv = (int)((uintptr_t)ip + (uintptr_t)thr) / sizeof(hammer2_inode_t);
1052 	mask = 1U << (hv & 31);
1053 	hv >>= 5;
1054 
1055 	return ((int)(hash[hv & XOP_HASH_MASK] & mask));
1056 }
1057 
1058 static __inline
1059 void
1060 xop_sethash(hammer2_thread_t *thr, hammer2_inode_t *ip, uint32_t *hash)
1061 {
1062 	uint32_t mask;
1063 	int hv;
1064 
1065 	hv = (int)((uintptr_t)ip + (uintptr_t)thr) / sizeof(hammer2_inode_t);
1066 	mask = 1U << (hv & 31);
1067 	hv >>= 5;
1068 
1069 	hash[hv & XOP_HASH_MASK] |= mask;
1070 }
1071 
1072 static
1073 hammer2_xop_head_t *
1074 hammer2_xop_next(hammer2_thread_t *thr)
1075 {
1076 	hammer2_pfs_t *pmp = thr->pmp;
1077 	int clindex = thr->clindex;
1078 	uint32_t hash[XOP_HASH_SIZE] = { 0 };
1079 	hammer2_xop_head_t *xop;
1080 
1081 	hammer2_spin_ex(&pmp->xop_spin);
1082 	TAILQ_FOREACH(xop, &thr->xopq, collect[clindex].entry) {
1083 		/*
1084 		 * Check dependency
1085 		 */
1086 		if (xop_testhash(thr, xop->ip1, hash) ||
1087 		    (xop->ip2 && xop_testhash(thr, xop->ip2, hash)) ||
1088 		    (xop->ip3 && xop_testhash(thr, xop->ip3, hash)) ||
1089 		    (xop->ip4 && xop_testhash(thr, xop->ip4, hash)))
1090 		{
1091 			continue;
1092 		}
1093 		xop_sethash(thr, xop->ip1, hash);
1094 		if (xop->ip2)
1095 			xop_sethash(thr, xop->ip2, hash);
1096 		if (xop->ip3)
1097 			xop_sethash(thr, xop->ip3, hash);
1098 		if (xop->ip4)
1099 			xop_sethash(thr, xop->ip4, hash);
1100 
1101 		/*
1102 		 * Check already running
1103 		 */
1104 		if (xop->collect[clindex].flags & HAMMER2_XOP_FIFO_RUN)
1105 			continue;
1106 
1107 		/*
1108 		 * Found a good one, return it.
1109 		 */
1110 		atomic_set_int(&xop->collect[clindex].flags,
1111 			       HAMMER2_XOP_FIFO_RUN);
1112 		break;
1113 	}
1114 	hammer2_spin_unex(&pmp->xop_spin);
1115 
1116 	return xop;
1117 }
1118 
1119 /*
1120  * Remove the completed XOP from the queue, clear HAMMER2_XOP_FIFO_RUN.
1121  *
1122  * NOTE! Xops run concurrently for each cluster index.
1123  */
1124 static
1125 void
1126 hammer2_xop_dequeue(hammer2_thread_t *thr, hammer2_xop_head_t *xop)
1127 {
1128 	hammer2_pfs_t *pmp = thr->pmp;
1129 	int clindex = thr->clindex;
1130 
1131 	hammer2_spin_ex(&pmp->xop_spin);
1132 	TAILQ_REMOVE(&thr->xopq, xop, collect[clindex].entry);
1133 	atomic_clear_int(&xop->collect[clindex].flags,
1134 			 HAMMER2_XOP_FIFO_RUN);
1135 	hammer2_spin_unex(&pmp->xop_spin);
1136 	if (TAILQ_FIRST(&thr->xopq))
1137 		hammer2_thr_signal(thr, HAMMER2_THREAD_XOPQ);
1138 }
1139 
1140 /*
1141  * Primary management thread for xops support.  Each node has several such
1142  * threads which replicate front-end operations on cluster nodes.
1143  *
1144  * XOPS thread node operations, allowing the function to focus on a single
1145  * node in the cluster after validating the operation with the cluster.
1146  * This is primarily what prevents dead or stalled nodes from stalling
1147  * the front-end.
1148  */
1149 void
1150 hammer2_primary_xops_thread(void *arg)
1151 {
1152 	hammer2_thread_t *thr = arg;
1153 	hammer2_xop_head_t *xop;
1154 	uint64_t mask;
1155 	uint32_t flags;
1156 	uint32_t nflags;
1157 
1158 	mask = 1LLU << thr->clindex;
1159 
1160 	for (;;) {
1161 		flags = thr->flags;
1162 
1163 		/*
1164 		 * Handle stop request
1165 		 */
1166 		if (flags & HAMMER2_THREAD_STOP)
1167 			break;
1168 
1169 		/*
1170 		 * Handle freeze request
1171 		 */
1172 		if (flags & HAMMER2_THREAD_FREEZE) {
1173 			hammer2_thr_signal2(thr, HAMMER2_THREAD_FROZEN,
1174 						 HAMMER2_THREAD_FREEZE);
1175 			continue;
1176 		}
1177 
1178 		if (flags & HAMMER2_THREAD_UNFREEZE) {
1179 			hammer2_thr_signal2(thr, 0,
1180 						 HAMMER2_THREAD_FROZEN |
1181 						 HAMMER2_THREAD_UNFREEZE);
1182 			continue;
1183 		}
1184 
1185 		/*
1186 		 * Force idle if frozen until unfrozen or stopped.
1187 		 */
1188 		if (flags & HAMMER2_THREAD_FROZEN) {
1189 			hammer2_thr_wait_any(thr,
1190 					     HAMMER2_THREAD_UNFREEZE |
1191 					     HAMMER2_THREAD_STOP,
1192 					     0);
1193 			continue;
1194 		}
1195 
1196 		/*
1197 		 * Reset state on REMASTER request
1198 		 */
1199 		if (flags & HAMMER2_THREAD_REMASTER) {
1200 			hammer2_thr_signal2(thr, 0, HAMMER2_THREAD_REMASTER);
1201 			/* reset state here */
1202 			continue;
1203 		}
1204 
1205 		/*
1206 		 * Process requests.  Each request can be multi-queued.
1207 		 *
1208 		 * If we get behind and the frontend VOP is no longer active,
1209 		 * we retire the request without processing it.  The callback
1210 		 * may also abort processing if the frontend VOP becomes
1211 		 * inactive.
1212 		 */
1213 		if (flags & HAMMER2_THREAD_XOPQ) {
1214 			nflags = flags & ~HAMMER2_THREAD_XOPQ;
1215 			if (!atomic_cmpset_int(&thr->flags, flags, nflags))
1216 				continue;
1217 			flags = nflags;
1218 			/* fall through */
1219 		}
1220 		while ((xop = hammer2_xop_next(thr)) != NULL) {
1221 			if (hammer2_xop_active(xop)) {
1222 				xop->desc->storage_func((hammer2_xop_t *)xop,
1223 							thr->scratch,
1224 							thr->clindex);
1225 				hammer2_xop_dequeue(thr, xop);
1226 				hammer2_xop_retire(xop, mask);
1227 			} else {
1228 				hammer2_xop_feed(xop, NULL, thr->clindex,
1229 						 ECONNABORTED);
1230 				hammer2_xop_dequeue(thr, xop);
1231 				hammer2_xop_retire(xop, mask);
1232 			}
1233 		}
1234 
1235 		/* Don't wait, this is a XOP caller thread in makefs */
1236 		break;
1237 
1238 		/*
1239 		 * Wait for event, interlock using THREAD_WAITING and
1240 		 * THREAD_SIGNAL.
1241 		 *
1242 		 * For robustness poll on a 30-second interval, but nominally
1243 		 * expect to be woken up.
1244 		 */
1245 		nflags = flags | HAMMER2_THREAD_WAITING;
1246 
1247 		tsleep_interlock(&thr->flags, 0);
1248 		if (atomic_cmpset_int(&thr->flags, flags, nflags)) {
1249 			tsleep(&thr->flags, PINTERLOCKED, "h2idle", hz*30);
1250 		}
1251 	}
1252 
1253 #if 0
1254 	/*
1255 	 * Cleanup / termination
1256 	 */
1257 	while ((xop = TAILQ_FIRST(&thr->xopq)) != NULL) {
1258 		kprintf("hammer2_thread: aborting xop %s\n", xop->desc->id);
1259 		TAILQ_REMOVE(&thr->xopq, xop,
1260 			     collect[thr->clindex].entry);
1261 		hammer2_xop_retire(xop, mask);
1262 	}
1263 #endif
1264 	thr->td = NULL;
1265 	hammer2_thr_signal(thr, HAMMER2_THREAD_STOPPED);
1266 	/* thr structure can go invalid after this point */
1267 }
1268