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("$FreeBSD$");
32
33#include <sys/param.h>	/* powerof2() */
34#include <sys/queue.h>
35
36#include <bitstring.h>
37#include <errno.h>
38#include <stdint.h>
39#include <stdio.h>
40#include <stdlib.h>
41#include <string.h>
42
43#include <pjdlog.h>
44
45#include "activemap.h"
46
47#ifndef	PJDLOG_ASSERT
48#include <assert.h>
49#define	PJDLOG_ASSERT(...)	assert(__VA_ARGS__)
50#endif
51
52#define	ACTIVEMAP_MAGIC	0xac71e4
53struct activemap {
54	int		 am_magic;	/* Magic value. */
55	off_t		 am_mediasize;	/* Media size in bytes. */
56	uint32_t	 am_extentsize;	/* Extent size in bytes,
57					   must be power of 2. */
58	uint8_t		 am_extentshift;/* 2 ^ extentbits == extentsize */
59	int		 am_nextents;	/* Number of extents. */
60	size_t		 am_mapsize;	/* Bitmap size in bytes. */
61	uint16_t	*am_memtab;	/* An array that holds number of pending
62					   writes per extent. */
63	bitstr_t	*am_diskmap;	/* On-disk bitmap of dirty extents. */
64	bitstr_t	*am_memmap;	/* In-memory bitmap of dirty extents. */
65	size_t		 am_diskmapsize; /* Map size rounded up to sector size. */
66	uint64_t	 am_ndirty;	/* Number of dirty regions. */
67	bitstr_t	*am_syncmap;	/* Bitmap of extents to sync. */
68	off_t		 am_syncoff;	/* Next synchronization offset. */
69	TAILQ_HEAD(skeepdirty, keepdirty) am_keepdirty; /* List of extents that
70					   we keep dirty to reduce bitmap
71					   updates. */
72	int		 am_nkeepdirty;	/* Number of am_keepdirty elements. */
73	int		 am_nkeepdirty_limit; /* Maximum number of am_keepdirty
74					         elements. */
75};
76
77struct keepdirty {
78	int	kd_extent;
79	TAILQ_ENTRY(keepdirty) kd_next;
80};
81
82/*
83 * Helper function taken from sys/systm.h to calculate extentshift.
84 */
85static uint32_t
86bitcount32(uint32_t x)
87{
88
89	x = (x & 0x55555555) + ((x & 0xaaaaaaaa) >> 1);
90	x = (x & 0x33333333) + ((x & 0xcccccccc) >> 2);
91	x = (x + (x >> 4)) & 0x0f0f0f0f;
92	x = (x + (x >> 8));
93	x = (x + (x >> 16)) & 0x000000ff;
94	return (x);
95}
96
97static __inline int
98off2ext(const struct activemap *amp, off_t offset)
99{
100	int extent;
101
102	PJDLOG_ASSERT(offset >= 0 && offset < amp->am_mediasize);
103	extent = (offset >> amp->am_extentshift);
104	PJDLOG_ASSERT(extent >= 0 && extent < amp->am_nextents);
105	return (extent);
106}
107
108static __inline off_t
109ext2off(const struct activemap *amp, int extent)
110{
111	off_t offset;
112
113	PJDLOG_ASSERT(extent >= 0 && extent < amp->am_nextents);
114	offset = ((off_t)extent << amp->am_extentshift);
115	PJDLOG_ASSERT(offset >= 0 && offset < amp->am_mediasize);
116	return (offset);
117}
118
119/*
120 * Function calculates number of requests needed to synchronize the given
121 * extent.
122 */
123static __inline int
124ext2reqs(const struct activemap *amp, int ext)
125{
126	off_t left;
127
128	if (ext < amp->am_nextents - 1)
129		return (((amp->am_extentsize - 1) / MAXPHYS) + 1);
130
131	PJDLOG_ASSERT(ext == amp->am_nextents - 1);
132	left = amp->am_mediasize % amp->am_extentsize;
133	if (left == 0)
134		left = amp->am_extentsize;
135	return (((left - 1) / MAXPHYS) + 1);
136}
137
138/*
139 * Initialize activemap structure and allocate memory for internal needs.
140 * Function returns 0 on success and -1 if any of the allocations failed.
141 */
142int
143activemap_init(struct activemap **ampp, uint64_t mediasize, uint32_t extentsize,
144    uint32_t sectorsize, uint32_t keepdirty)
145{
146	struct activemap *amp;
147
148	PJDLOG_ASSERT(ampp != NULL);
149	PJDLOG_ASSERT(mediasize > 0);
150	PJDLOG_ASSERT(extentsize > 0);
151	PJDLOG_ASSERT(powerof2(extentsize));
152	PJDLOG_ASSERT(sectorsize > 0);
153	PJDLOG_ASSERT(powerof2(sectorsize));
154	PJDLOG_ASSERT(keepdirty > 0);
155
156	amp = malloc(sizeof(*amp));
157	if (amp == NULL)
158		return (-1);
159
160	amp->am_mediasize = mediasize;
161	amp->am_nkeepdirty_limit = keepdirty;
162	amp->am_extentsize = extentsize;
163	amp->am_extentshift = bitcount32(extentsize - 1);
164	amp->am_nextents = ((mediasize - 1) / extentsize) + 1;
165	amp->am_mapsize = sizeof(bitstr_t) * bitstr_size(amp->am_nextents);
166	amp->am_diskmapsize = roundup2(amp->am_mapsize, sectorsize);
167	amp->am_ndirty = 0;
168	amp->am_syncoff = -2;
169	TAILQ_INIT(&amp->am_keepdirty);
170	amp->am_nkeepdirty = 0;
171
172	amp->am_memtab = calloc(amp->am_nextents, sizeof(amp->am_memtab[0]));
173	amp->am_diskmap = calloc(1, amp->am_diskmapsize);
174	amp->am_memmap = bit_alloc(amp->am_nextents);
175	amp->am_syncmap = bit_alloc(amp->am_nextents);
176
177	/*
178	 * Check to see if any of the allocations above failed.
179	 */
180	if (amp->am_memtab == NULL || amp->am_diskmap == NULL ||
181	    amp->am_memmap == NULL || amp->am_syncmap == NULL) {
182		if (amp->am_memtab != NULL)
183			free(amp->am_memtab);
184		if (amp->am_diskmap != NULL)
185			free(amp->am_diskmap);
186		if (amp->am_memmap != NULL)
187			free(amp->am_memmap);
188		if (amp->am_syncmap != NULL)
189			free(amp->am_syncmap);
190		amp->am_magic = 0;
191		free(amp);
192		errno = ENOMEM;
193		return (-1);
194	}
195
196	amp->am_magic = ACTIVEMAP_MAGIC;
197	*ampp = amp;
198
199	return (0);
200}
201
202static struct keepdirty *
203keepdirty_find(struct activemap *amp, int extent)
204{
205	struct keepdirty *kd;
206
207	TAILQ_FOREACH(kd, &amp->am_keepdirty, kd_next) {
208		if (kd->kd_extent == extent)
209			break;
210	}
211	return (kd);
212}
213
214static bool
215keepdirty_add(struct activemap *amp, int extent)
216{
217	struct keepdirty *kd;
218
219	kd = keepdirty_find(amp, extent);
220	if (kd != NULL) {
221		/*
222		 * Only move element at the beginning.
223		 */
224		TAILQ_REMOVE(&amp->am_keepdirty, kd, kd_next);
225		TAILQ_INSERT_HEAD(&amp->am_keepdirty, kd, kd_next);
226		return (false);
227	}
228	/*
229	 * Add new element, but first remove the most unused one if
230	 * we have too many.
231	 */
232	if (amp->am_nkeepdirty >= amp->am_nkeepdirty_limit) {
233		kd = TAILQ_LAST(&amp->am_keepdirty, skeepdirty);
234		PJDLOG_ASSERT(kd != NULL);
235		TAILQ_REMOVE(&amp->am_keepdirty, kd, kd_next);
236		amp->am_nkeepdirty--;
237		PJDLOG_ASSERT(amp->am_nkeepdirty > 0);
238	}
239	if (kd == NULL)
240		kd = malloc(sizeof(*kd));
241	/* We can ignore allocation failure. */
242	if (kd != NULL) {
243		kd->kd_extent = extent;
244		amp->am_nkeepdirty++;
245		TAILQ_INSERT_HEAD(&amp->am_keepdirty, kd, kd_next);
246	}
247
248	return (true);
249}
250
251static void
252keepdirty_fill(struct activemap *amp)
253{
254	struct keepdirty *kd;
255
256	TAILQ_FOREACH(kd, &amp->am_keepdirty, kd_next)
257		bit_set(amp->am_diskmap, kd->kd_extent);
258}
259
260static void
261keepdirty_free(struct activemap *amp)
262{
263	struct keepdirty *kd;
264
265	while ((kd = TAILQ_FIRST(&amp->am_keepdirty)) != NULL) {
266		TAILQ_REMOVE(&amp->am_keepdirty, kd, kd_next);
267		amp->am_nkeepdirty--;
268		free(kd);
269	}
270	PJDLOG_ASSERT(amp->am_nkeepdirty == 0);
271}
272
273/*
274 * Function frees resources allocated by activemap_init() function.
275 */
276void
277activemap_free(struct activemap *amp)
278{
279
280	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
281
282	amp->am_magic = 0;
283
284	keepdirty_free(amp);
285	free(amp->am_memtab);
286	free(amp->am_diskmap);
287	free(amp->am_memmap);
288	free(amp->am_syncmap);
289}
290
291/*
292 * Function should be called before we handle write requests. It updates
293 * internal structures and returns true if on-disk metadata should be updated.
294 */
295bool
296activemap_write_start(struct activemap *amp, off_t offset, off_t length)
297{
298	bool modified;
299	off_t end;
300	int ext;
301
302	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
303	PJDLOG_ASSERT(length > 0);
304
305	modified = false;
306	end = offset + length - 1;
307
308	for (ext = off2ext(amp, offset); ext <= off2ext(amp, end); ext++) {
309		/*
310		 * If the number of pending writes is increased from 0,
311		 * we have to mark the extent as dirty also in on-disk bitmap.
312		 * By returning true we inform the caller that on-disk bitmap
313		 * was modified and has to be flushed to disk.
314		 */
315		if (amp->am_memtab[ext]++ == 0) {
316			PJDLOG_ASSERT(!bit_test(amp->am_memmap, ext));
317			bit_set(amp->am_memmap, ext);
318			amp->am_ndirty++;
319		}
320		if (keepdirty_add(amp, ext))
321			modified = true;
322	}
323
324	return (modified);
325}
326
327/*
328 * Function should be called after receiving write confirmation. It updates
329 * internal structures and returns true if on-disk metadata should be updated.
330 */
331bool
332activemap_write_complete(struct activemap *amp, off_t offset, off_t length)
333{
334	bool modified;
335	off_t end;
336	int ext;
337
338	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
339	PJDLOG_ASSERT(length > 0);
340
341	modified = false;
342	end = offset + length - 1;
343
344	for (ext = off2ext(amp, offset); ext <= off2ext(amp, end); ext++) {
345		/*
346		 * If the number of pending writes goes down to 0, we have to
347		 * mark the extent as clean also in on-disk bitmap.
348		 * By returning true we inform the caller that on-disk bitmap
349		 * was modified and has to be flushed to disk.
350		 */
351		PJDLOG_ASSERT(amp->am_memtab[ext] > 0);
352		PJDLOG_ASSERT(bit_test(amp->am_memmap, ext));
353		if (--amp->am_memtab[ext] == 0) {
354			bit_clear(amp->am_memmap, ext);
355			amp->am_ndirty--;
356			if (keepdirty_find(amp, ext) == NULL)
357				modified = true;
358		}
359	}
360
361	return (modified);
362}
363
364/*
365 * Function should be called after finishing synchronization of one extent.
366 * It returns true if on-disk metadata should be updated.
367 */
368bool
369activemap_extent_complete(struct activemap *amp, int extent)
370{
371	bool modified;
372	int reqs;
373
374	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
375	PJDLOG_ASSERT(extent >= 0 && extent < amp->am_nextents);
376
377	modified = false;
378
379	reqs = ext2reqs(amp, extent);
380	PJDLOG_ASSERT(amp->am_memtab[extent] >= reqs);
381	amp->am_memtab[extent] -= reqs;
382	PJDLOG_ASSERT(bit_test(amp->am_memmap, extent));
383	if (amp->am_memtab[extent] == 0) {
384		bit_clear(amp->am_memmap, extent);
385		amp->am_ndirty--;
386		modified = true;
387	}
388
389	return (modified);
390}
391
392/*
393 * Function returns number of dirty regions.
394 */
395uint64_t
396activemap_ndirty(const struct activemap *amp)
397{
398
399	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
400
401	return (amp->am_ndirty);
402}
403
404/*
405 * Function compare on-disk bitmap and in-memory bitmap and returns true if
406 * they differ and should be flushed to the disk.
407 */
408bool
409activemap_differ(const struct activemap *amp)
410{
411
412	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
413
414	return (memcmp(amp->am_diskmap, amp->am_memmap,
415	    amp->am_mapsize) != 0);
416}
417
418/*
419 * Function returns number of bytes used by bitmap.
420 */
421size_t
422activemap_size(const struct activemap *amp)
423{
424
425	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
426
427	return (amp->am_mapsize);
428}
429
430/*
431 * Function returns number of bytes needed for storing on-disk bitmap.
432 * This is the same as activemap_size(), but rounded up to sector size.
433 */
434size_t
435activemap_ondisk_size(const struct activemap *amp)
436{
437
438	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
439
440	return (amp->am_diskmapsize);
441}
442
443/*
444 * Function copies the given buffer read from disk to the internal bitmap.
445 */
446void
447activemap_copyin(struct activemap *amp, const unsigned char *buf, size_t size)
448{
449	int ext;
450
451	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
452	PJDLOG_ASSERT(size >= amp->am_mapsize);
453
454	memcpy(amp->am_diskmap, buf, amp->am_mapsize);
455	memcpy(amp->am_memmap, buf, amp->am_mapsize);
456	memcpy(amp->am_syncmap, buf, amp->am_mapsize);
457
458	bit_ffs(amp->am_memmap, amp->am_nextents, &ext);
459	if (ext == -1) {
460		/* There are no dirty extents, so we can leave now. */
461		return;
462	}
463	/*
464	 * Set synchronization offset to the first dirty extent.
465	 */
466	activemap_sync_rewind(amp);
467	/*
468	 * We have dirty extents and we want them to stay that way until
469	 * we synchronize, so we set number of pending writes to number
470	 * of requests needed to synchronize one extent.
471	 */
472	amp->am_ndirty = 0;
473	for (; ext < amp->am_nextents; ext++) {
474		if (bit_test(amp->am_memmap, ext)) {
475			amp->am_memtab[ext] = ext2reqs(amp, ext);
476			amp->am_ndirty++;
477		}
478	}
479}
480
481/*
482 * Function merges the given bitmap with existing one.
483 */
484void
485activemap_merge(struct activemap *amp, const unsigned char *buf, size_t size)
486{
487	bitstr_t *remmap = __DECONST(bitstr_t *, buf);
488	int ext;
489
490	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
491	PJDLOG_ASSERT(size >= amp->am_mapsize);
492
493	bit_ffs(remmap, amp->am_nextents, &ext);
494	if (ext == -1) {
495		/* There are no dirty extents, so we can leave now. */
496		return;
497	}
498	/*
499	 * We have dirty extents and we want them to stay that way until
500	 * we synchronize, so we set number of pending writes to number
501	 * of requests needed to synchronize one extent.
502	 */
503	for (; ext < amp->am_nextents; ext++) {
504		/* Local extent already dirty. */
505		if (bit_test(amp->am_syncmap, ext))
506			continue;
507		/* Remote extent isn't dirty. */
508		if (!bit_test(remmap, ext))
509			continue;
510		bit_set(amp->am_syncmap, ext);
511		bit_set(amp->am_memmap, ext);
512		bit_set(amp->am_diskmap, ext);
513		if (amp->am_memtab[ext] == 0)
514			amp->am_ndirty++;
515		amp->am_memtab[ext] = ext2reqs(amp, ext);
516	}
517	/*
518	 * Set synchronization offset to the first dirty extent.
519	 */
520	activemap_sync_rewind(amp);
521}
522
523/*
524 * Function returns pointer to internal bitmap that should be written to disk.
525 */
526const unsigned char *
527activemap_bitmap(struct activemap *amp, size_t *sizep)
528{
529
530	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
531
532	if (sizep != NULL)
533		*sizep = amp->am_diskmapsize;
534	memcpy(amp->am_diskmap, amp->am_memmap, amp->am_mapsize);
535	keepdirty_fill(amp);
536	return ((const unsigned char *)amp->am_diskmap);
537}
538
539/*
540 * Function calculates size needed to store bitmap on disk.
541 */
542size_t
543activemap_calc_ondisk_size(uint64_t mediasize, uint32_t extentsize,
544    uint32_t sectorsize)
545{
546	uint64_t nextents, mapsize;
547
548	PJDLOG_ASSERT(mediasize > 0);
549	PJDLOG_ASSERT(extentsize > 0);
550	PJDLOG_ASSERT(powerof2(extentsize));
551	PJDLOG_ASSERT(sectorsize > 0);
552	PJDLOG_ASSERT(powerof2(sectorsize));
553
554	nextents = ((mediasize - 1) / extentsize) + 1;
555	mapsize = sizeof(bitstr_t) * bitstr_size(nextents);
556	return (roundup2(mapsize, sectorsize));
557}
558
559/*
560 * Set synchronization offset to the first dirty extent.
561 */
562void
563activemap_sync_rewind(struct activemap *amp)
564{
565	int ext;
566
567	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
568
569	bit_ffs(amp->am_syncmap, amp->am_nextents, &ext);
570	if (ext == -1) {
571		/* There are no extents to synchronize. */
572		amp->am_syncoff = -2;
573		return;
574	}
575	/*
576	 * Mark that we want to start synchronization from the beginning.
577	 */
578	amp->am_syncoff = -1;
579}
580
581/*
582 * Return next offset of where we should synchronize.
583 */
584off_t
585activemap_sync_offset(struct activemap *amp, off_t *lengthp, int *syncextp)
586{
587	off_t syncoff, left;
588	int ext;
589
590	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
591	PJDLOG_ASSERT(lengthp != NULL);
592	PJDLOG_ASSERT(syncextp != NULL);
593
594	*syncextp = -1;
595
596	if (amp->am_syncoff == -2)
597		return (-1);
598
599	if (amp->am_syncoff >= 0 &&
600	    (amp->am_syncoff + MAXPHYS >= amp->am_mediasize ||
601	     off2ext(amp, amp->am_syncoff) !=
602	     off2ext(amp, amp->am_syncoff + MAXPHYS))) {
603		/*
604		 * We are about to change extent, so mark previous one as clean.
605		 */
606		ext = off2ext(amp, amp->am_syncoff);
607		bit_clear(amp->am_syncmap, ext);
608		*syncextp = ext;
609		amp->am_syncoff = -1;
610	}
611
612	if (amp->am_syncoff == -1) {
613		/*
614		 * Let's find first extent to synchronize.
615		 */
616		bit_ffs(amp->am_syncmap, amp->am_nextents, &ext);
617		if (ext == -1) {
618			amp->am_syncoff = -2;
619			return (-1);
620		}
621		amp->am_syncoff = ext2off(amp, ext);
622	} else {
623		/*
624		 * We don't change extent, so just increase offset.
625		 */
626		amp->am_syncoff += MAXPHYS;
627		if (amp->am_syncoff >= amp->am_mediasize) {
628			amp->am_syncoff = -2;
629			return (-1);
630		}
631	}
632
633	syncoff = amp->am_syncoff;
634	left = ext2off(amp, off2ext(amp, syncoff)) +
635	    amp->am_extentsize - syncoff;
636	if (syncoff + left > amp->am_mediasize)
637		left = amp->am_mediasize - syncoff;
638	if (left > MAXPHYS)
639		left = MAXPHYS;
640
641	PJDLOG_ASSERT(left >= 0 && left <= MAXPHYS);
642	PJDLOG_ASSERT(syncoff >= 0 && syncoff < amp->am_mediasize);
643	PJDLOG_ASSERT(syncoff + left >= 0 &&
644	    syncoff + left <= amp->am_mediasize);
645
646	*lengthp = left;
647	return (syncoff);
648}
649
650/*
651 * Mark extent(s) containing the given region for synchronization.
652 * Most likely one of the components is unavailable.
653 */
654bool
655activemap_need_sync(struct activemap *amp, off_t offset, off_t length)
656{
657	bool modified;
658	off_t end;
659	int ext;
660
661	PJDLOG_ASSERT(amp->am_magic == ACTIVEMAP_MAGIC);
662
663	modified = false;
664	end = offset + length - 1;
665
666	for (ext = off2ext(amp, offset); ext <= off2ext(amp, end); ext++) {
667		if (bit_test(amp->am_syncmap, ext)) {
668			/* Already marked for synchronization. */
669			PJDLOG_ASSERT(bit_test(amp->am_memmap, ext));
670			continue;
671		}
672		bit_set(amp->am_syncmap, ext);
673		if (!bit_test(amp->am_memmap, ext)) {
674			bit_set(amp->am_memmap, ext);
675			amp->am_ndirty++;
676		}
677		amp->am_memtab[ext] += ext2reqs(amp, ext);
678		modified = true;
679	}
680
681	return (modified);
682}
683
684void
685activemap_dump(const struct activemap *amp)
686{
687	int bit;
688
689	printf("M: ");
690	for (bit = 0; bit < amp->am_nextents; bit++)
691		printf("%d", bit_test(amp->am_memmap, bit) ? 1 : 0);
692	printf("\n");
693	printf("D: ");
694	for (bit = 0; bit < amp->am_nextents; bit++)
695		printf("%d", bit_test(amp->am_diskmap, bit) ? 1 : 0);
696	printf("\n");
697	printf("S: ");
698	for (bit = 0; bit < amp->am_nextents; bit++)
699		printf("%d", bit_test(amp->am_syncmap, bit) ? 1 : 0);
700	printf("\n");
701}
702