xref: /dragonfly/sys/vfs/hammer2/hammer2_freemap.c (revision 17183580)
1 /*
2  * Copyright (c) 2011-2018 The DragonFly Project.  All rights reserved.
3  *
4  * This code is derived from software contributed to The DragonFly Project
5  * by Matthew Dillon <dillon@dragonflybsd.org>
6  * by Venkatesh Srinivas <vsrinivas@dragonflybsd.org>
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  *
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in
16  *    the documentation and/or other materials provided with the
17  *    distribution.
18  * 3. Neither the name of The DragonFly Project nor the names of its
19  *    contributors may be used to endorse or promote products derived
20  *    from this software without specific, prior written permission.
21  *
22  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
23  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
24  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
25  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
26  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
27  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
28  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
29  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
30  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
31  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
32  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.
34  */
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/kernel.h>
38 #include <sys/proc.h>
39 #include <sys/mount.h>
40 
41 #include "hammer2.h"
42 
43 #define FREEMAP_DEBUG	0
44 
45 struct hammer2_fiterate {
46 	hammer2_off_t	bpref;
47 	hammer2_off_t	bnext;
48 	int		loops;
49 	int		relaxed;
50 };
51 
52 typedef struct hammer2_fiterate hammer2_fiterate_t;
53 
54 static int hammer2_freemap_try_alloc(hammer2_chain_t **parentp,
55 			hammer2_blockref_t *bref, int radix,
56 			hammer2_fiterate_t *iter, hammer2_tid_t mtid);
57 static void hammer2_freemap_init(hammer2_dev_t *hmp,
58 			hammer2_key_t key, hammer2_chain_t *chain);
59 static int hammer2_bmap_alloc(hammer2_dev_t *hmp,
60 			hammer2_bmap_data_t *bmap, uint16_t class,
61 			int n, int sub_key, int radix, hammer2_key_t *basep);
62 static int hammer2_freemap_iterate(hammer2_chain_t **parentp,
63 			hammer2_chain_t **chainp,
64 			hammer2_fiterate_t *iter);
65 
66 /*
67  * Calculate the device offset for the specified FREEMAP_NODE or FREEMAP_LEAF
68  * bref.  Return a combined media offset and physical size radix.  Freemap
69  * chains use fixed storage offsets in the 4MB reserved area at the
70  * beginning of each 1GB zone.
71  *
72  * Rotate between eight possibilities.  Theoretically this means we have seven
73  * good freemaps in case of a crash which we can use as a base for the fixup
74  * scan at mount-time.
75  */
76 static
77 int
78 hammer2_freemap_reserve(hammer2_chain_t *chain, int radix)
79 {
80 	hammer2_blockref_t *bref = &chain->bref;
81 	hammer2_off_t off;
82 	int index;
83 	int index_inc;
84 	size_t bytes;
85 
86 	/*
87 	 * Physical allocation size.
88 	 */
89 	bytes = (size_t)1 << radix;
90 
91 	/*
92 	 * Calculate block selection index 0..7 of current block.  If this
93 	 * is the first allocation of the block (verses a modification of an
94 	 * existing block), we use index 0, otherwise we use the next rotating
95 	 * index.
96 	 */
97 	if ((bref->data_off & ~HAMMER2_OFF_MASK_RADIX) == 0) {
98 		index = 0;
99 	} else {
100 		off = bref->data_off & ~HAMMER2_OFF_MASK_RADIX &
101 		      HAMMER2_SEGMASK;
102 		off = off / HAMMER2_PBUFSIZE;
103 		KKASSERT(off >= HAMMER2_ZONE_FREEMAP_00 &&
104 			 off < HAMMER2_ZONE_FREEMAP_END);
105 		index = (int)(off - HAMMER2_ZONE_FREEMAP_00) /
106 			HAMMER2_ZONE_FREEMAP_INC;
107 		KKASSERT(index >= 0 && index < HAMMER2_NFREEMAPS);
108 		if (++index == HAMMER2_NFREEMAPS)
109 			index = 0;
110 	}
111 
112 	/*
113 	 * Calculate the block offset of the reserved block.  This will
114 	 * point into the 4MB reserved area at the base of the appropriate
115 	 * 2GB zone, once added to the FREEMAP_x selection above.
116 	 */
117 	index_inc = index * HAMMER2_ZONE_FREEMAP_INC;
118 
119 	switch(bref->keybits) {
120 	/* case HAMMER2_FREEMAP_LEVEL6_RADIX: not applicable */
121 	case HAMMER2_FREEMAP_LEVEL5_RADIX:	/* 4EB */
122 		KKASSERT(bref->type == HAMMER2_BREF_TYPE_FREEMAP_NODE);
123 		KKASSERT(bytes == HAMMER2_FREEMAP_LEVELN_PSIZE);
124 		off = H2FMBASE(bref->key, HAMMER2_FREEMAP_LEVEL5_RADIX) +
125 		      (index_inc + HAMMER2_ZONE_FREEMAP_00 +
126 		       HAMMER2_ZONEFM_LEVEL5) * HAMMER2_PBUFSIZE;
127 		break;
128 	case HAMMER2_FREEMAP_LEVEL4_RADIX:	/* 16PB */
129 		KKASSERT(bref->type == HAMMER2_BREF_TYPE_FREEMAP_NODE);
130 		KKASSERT(bytes == HAMMER2_FREEMAP_LEVELN_PSIZE);
131 		off = H2FMBASE(bref->key, HAMMER2_FREEMAP_LEVEL4_RADIX) +
132 		      (index_inc + HAMMER2_ZONE_FREEMAP_00 +
133 		       HAMMER2_ZONEFM_LEVEL4) * HAMMER2_PBUFSIZE;
134 		break;
135 	case HAMMER2_FREEMAP_LEVEL3_RADIX:	/* 64TB */
136 		KKASSERT(bref->type == HAMMER2_BREF_TYPE_FREEMAP_NODE);
137 		KKASSERT(bytes == HAMMER2_FREEMAP_LEVELN_PSIZE);
138 		off = H2FMBASE(bref->key, HAMMER2_FREEMAP_LEVEL3_RADIX) +
139 		      (index_inc + HAMMER2_ZONE_FREEMAP_00 +
140 		       HAMMER2_ZONEFM_LEVEL3) * HAMMER2_PBUFSIZE;
141 		break;
142 	case HAMMER2_FREEMAP_LEVEL2_RADIX:	/* 256GB */
143 		KKASSERT(bref->type == HAMMER2_BREF_TYPE_FREEMAP_NODE);
144 		KKASSERT(bytes == HAMMER2_FREEMAP_LEVELN_PSIZE);
145 		off = H2FMBASE(bref->key, HAMMER2_FREEMAP_LEVEL2_RADIX) +
146 		      (index_inc + HAMMER2_ZONE_FREEMAP_00 +
147 		       HAMMER2_ZONEFM_LEVEL2) * HAMMER2_PBUFSIZE;
148 		break;
149 	case HAMMER2_FREEMAP_LEVEL1_RADIX:	/* 1GB */
150 		KKASSERT(bref->type == HAMMER2_BREF_TYPE_FREEMAP_LEAF);
151 		KKASSERT(bytes == HAMMER2_FREEMAP_LEVELN_PSIZE);
152 		off = H2FMBASE(bref->key, HAMMER2_FREEMAP_LEVEL1_RADIX) +
153 		      (index_inc + HAMMER2_ZONE_FREEMAP_00 +
154 		       HAMMER2_ZONEFM_LEVEL1) * HAMMER2_PBUFSIZE;
155 		break;
156 	default:
157 		panic("freemap: bad radix(2) %p %d\n", bref, bref->keybits);
158 		/* NOT REACHED */
159 		off = (hammer2_off_t)-1;
160 		break;
161 	}
162 	bref->data_off = off | radix;
163 #if FREEMAP_DEBUG
164 	kprintf("FREEMAP BLOCK TYPE %d %016jx/%d DATA_OFF=%016jx\n",
165 		bref->type, bref->key, bref->keybits, bref->data_off);
166 #endif
167 	return (0);
168 }
169 
170 /*
171  * Normal freemap allocator
172  *
173  * Use available hints to allocate space using the freemap.  Create missing
174  * freemap infrastructure on-the-fly as needed (including marking initial
175  * allocations using the iterator as allocated, instantiating new 2GB zones,
176  * and dealing with the end-of-media edge case).
177  *
178  * bpref is only used as a heuristic to determine locality of reference.
179  *
180  * This function is a NOP if bytes is 0.
181  */
182 int
183 hammer2_freemap_alloc(hammer2_chain_t *chain, size_t bytes)
184 {
185 	hammer2_dev_t *hmp = chain->hmp;
186 	hammer2_blockref_t *bref = &chain->bref;
187 	hammer2_chain_t *parent;
188 	hammer2_tid_t mtid;
189 	int radix;
190 	int error;
191 	unsigned int hindex;
192 	hammer2_fiterate_t iter;
193 
194 	/*
195 	 * If allocating or downsizing to zero we just get rid of whatever
196 	 * data_off we had.
197 	 */
198 	if (bytes == 0) {
199 		chain->bref.data_off = 0;
200 		return 0;
201 	}
202 
203 	KKASSERT(hmp->spmp);
204 	mtid = hammer2_trans_sub(hmp->spmp);
205 
206 	/*
207 	 * Validate the allocation size.  It must be a power of 2.
208 	 *
209 	 * For now require that the caller be aware of the minimum
210 	 * allocation (1K).
211 	 */
212 	radix = hammer2_getradix(bytes);
213 	KKASSERT((size_t)1 << radix == bytes);
214 
215 	if (bref->type == HAMMER2_BREF_TYPE_FREEMAP_NODE ||
216 	    bref->type == HAMMER2_BREF_TYPE_FREEMAP_LEAF) {
217 		/*
218 		 * Freemap blocks themselves are assigned from the reserve
219 		 * area, not allocated from the freemap.
220 		 */
221 		error = hammer2_freemap_reserve(chain, radix);
222 
223 		return error;
224 	}
225 
226 	KKASSERT(bytes >= HAMMER2_ALLOC_MIN && bytes <= HAMMER2_ALLOC_MAX);
227 
228 	/*
229 	 * Heuristic tracking index.  We would like one for each distinct
230 	 * bref type if possible.  heur_freemap[] has room for two classes
231 	 * for each type.  At a minimum we have to break-up our heuristic
232 	 * by device block sizes.
233 	 */
234 	hindex = HAMMER2_PBUFRADIX - HAMMER2_LBUFRADIX;
235 	KKASSERT(hindex < HAMMER2_FREEMAP_HEUR_NRADIX);
236 	hindex += bref->type * HAMMER2_FREEMAP_HEUR_NRADIX;
237 	hindex &= HAMMER2_FREEMAP_HEUR_TYPES * HAMMER2_FREEMAP_HEUR_NRADIX - 1;
238 	KKASSERT(hindex < HAMMER2_FREEMAP_HEUR_SIZE);
239 
240 	iter.bpref = hmp->heur_freemap[hindex];
241 	iter.relaxed = hmp->freemap_relaxed;
242 
243 	/*
244 	 * Make sure bpref is in-bounds.  It's ok if bpref covers a zone's
245 	 * reserved area, the try code will iterate past it.
246 	 */
247 	if (iter.bpref > hmp->total_size)
248 		iter.bpref = hmp->total_size - 1;
249 
250 	/*
251 	 * Iterate the freemap looking for free space before and after.
252 	 */
253 	parent = &hmp->fchain;
254 	hammer2_chain_ref(parent);
255 	hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS);
256 	error = HAMMER2_ERROR_EAGAIN;
257 	iter.bnext = iter.bpref;
258 	iter.loops = 0;
259 
260 	while (error == HAMMER2_ERROR_EAGAIN) {
261 		error = hammer2_freemap_try_alloc(&parent, bref, radix,
262 						  &iter, mtid);
263 	}
264 	hmp->freemap_relaxed |= iter.relaxed;	/* heuristical, SMP race ok */
265 	hmp->heur_freemap[hindex] = iter.bnext;
266 	hammer2_chain_unlock(parent);
267 	hammer2_chain_drop(parent);
268 
269 	return (error);
270 }
271 
272 static int
273 hammer2_freemap_try_alloc(hammer2_chain_t **parentp,
274 			  hammer2_blockref_t *bref, int radix,
275 			  hammer2_fiterate_t *iter, hammer2_tid_t mtid)
276 {
277 	hammer2_dev_t *hmp = (*parentp)->hmp;
278 	hammer2_off_t l0size;
279 	hammer2_off_t l1size;
280 	hammer2_off_t l1mask;
281 	hammer2_key_t key_dummy;
282 	hammer2_chain_t *chain;
283 	hammer2_off_t key;
284 	size_t bytes;
285 	uint16_t class;
286 	int error;
287 
288 	/*
289 	 * Calculate the number of bytes being allocated.
290 	 */
291 	bytes = (size_t)1 << radix;
292 	class = (bref->type << 8) | HAMMER2_PBUFRADIX;
293 
294 	/*
295 	 * Lookup the level1 freemap chain, creating and initializing one
296 	 * if necessary.  Intermediate levels will be created automatically
297 	 * when necessary by hammer2_chain_create().
298 	 */
299 	key = H2FMBASE(iter->bnext, HAMMER2_FREEMAP_LEVEL1_RADIX);
300 	l0size = HAMMER2_FREEMAP_LEVEL0_SIZE;
301 	l1size = HAMMER2_FREEMAP_LEVEL1_SIZE;
302 	l1mask = l1size - 1;
303 
304 	chain = hammer2_chain_lookup(parentp, &key_dummy, key, key + l1mask,
305 				     &error,
306 				     HAMMER2_LOOKUP_ALWAYS |
307 				     HAMMER2_LOOKUP_MATCHIND);
308 
309 	if (chain == NULL) {
310 		/*
311 		 * Create the missing leaf, be sure to initialize
312 		 * the auxillary freemap tracking information in
313 		 * the bref.check.freemap structure.
314 		 */
315 #if 0
316 		kprintf("freemap create L1 @ %016jx bpref %016jx\n",
317 			key, iter->bpref);
318 #endif
319 		error = hammer2_chain_create(parentp, &chain, NULL, hmp->spmp,
320 				     HAMMER2_METH_DEFAULT,
321 				     key, HAMMER2_FREEMAP_LEVEL1_RADIX,
322 				     HAMMER2_BREF_TYPE_FREEMAP_LEAF,
323 				     HAMMER2_FREEMAP_LEVELN_PSIZE,
324 				     mtid, 0, 0);
325 		KKASSERT(error == 0);
326 		if (error == 0) {
327 			hammer2_chain_modify(chain, mtid, 0, 0);
328 			bzero(&chain->data->bmdata[0],
329 			      HAMMER2_FREEMAP_LEVELN_PSIZE);
330 			chain->bref.check.freemap.bigmask = (uint32_t)-1;
331 			chain->bref.check.freemap.avail = l1size;
332 			/* bref.methods should already be inherited */
333 
334 			hammer2_freemap_init(hmp, key, chain);
335 		}
336 	} else if (chain->error) {
337 		/*
338 		 * Error during lookup.
339 		 */
340 		kprintf("hammer2_freemap_try_alloc: %016jx: error %s\n",
341 			(intmax_t)bref->data_off,
342 			hammer2_error_str(chain->error));
343 		error = HAMMER2_ERROR_EIO;
344 	} else if ((chain->bref.check.freemap.bigmask &
345 		   ((size_t)1 << radix)) == 0) {
346 		/*
347 		 * Already flagged as not having enough space
348 		 */
349 		error = HAMMER2_ERROR_ENOSPC;
350 	} else {
351 		/*
352 		 * Modify existing chain to setup for adjustment.
353 		 */
354 		hammer2_chain_modify(chain, mtid, 0, 0);
355 	}
356 
357 	/*
358 	 * Scan 4MB entries.
359 	 */
360 	if (error == 0) {
361 		hammer2_bmap_data_t *bmap;
362 		hammer2_key_t base_key;
363 		int count;
364 		int start;
365 		int n;
366 
367 		KKASSERT(chain->bref.type == HAMMER2_BREF_TYPE_FREEMAP_LEAF);
368 		start = (int)((iter->bnext - key) >>
369 			      HAMMER2_FREEMAP_LEVEL0_RADIX);
370 		KKASSERT(start >= 0 && start < HAMMER2_FREEMAP_COUNT);
371 		hammer2_chain_modify(chain, mtid, 0, 0);
372 
373 		error = HAMMER2_ERROR_ENOSPC;
374 		for (count = 0; count < HAMMER2_FREEMAP_COUNT; ++count) {
375 			int availchk;
376 
377 			if (start + count >= HAMMER2_FREEMAP_COUNT &&
378 			    start - count < 0) {
379 				break;
380 			}
381 
382 			/*
383 			 * Calculate bmap pointer from thart starting index
384 			 * forwards.
385 			 *
386 			 * NOTE: bmap pointer is invalid if n >= FREEMAP_COUNT.
387 			 */
388 			n = start + count;
389 			bmap = &chain->data->bmdata[n];
390 
391 			if (n >= HAMMER2_FREEMAP_COUNT) {
392 				availchk = 0;
393 			} else if (bmap->avail) {
394 				availchk = 1;
395 			} else if (radix < HAMMER2_FREEMAP_BLOCK_RADIX &&
396 			          (bmap->linear & HAMMER2_FREEMAP_BLOCK_MASK)) {
397 				availchk = 1;
398 			} else {
399 				availchk = 0;
400 			}
401 
402 			/*
403 			 * Try to allocate from a matching freemap class
404 			 * superblock.  If we are in relaxed mode we allocate
405 			 * from any freemap class superblock.
406 			 */
407 			if (availchk &&
408 			    (bmap->class == 0 || bmap->class == class ||
409 			     iter->relaxed)) {
410 				base_key = key + n * l0size;
411 				error = hammer2_bmap_alloc(hmp, bmap,
412 							   class, n,
413 							   (int)bref->key,
414 							   radix,
415 							   &base_key);
416 				if (error != HAMMER2_ERROR_ENOSPC) {
417 					key = base_key;
418 					break;
419 				}
420 			}
421 
422 			/*
423 			 * Calculate bmap pointer from the starting index
424 			 * backwards (locality).
425 			 *
426 			 * Must recalculate after potentially having called
427 			 * hammer2_bmap_alloc() above in case chain was
428 			 * reallocated.
429 			 *
430 			 * NOTE: bmap pointer is invalid if n < 0.
431 			 */
432 			n = start - count;
433 			bmap = &chain->data->bmdata[n];
434 			if (n < 0) {
435 				availchk = 0;
436 			} else if (bmap->avail) {
437 				availchk = 1;
438 			} else if (radix < HAMMER2_FREEMAP_BLOCK_RADIX &&
439 			          (bmap->linear & HAMMER2_FREEMAP_BLOCK_MASK)) {
440 				availchk = 1;
441 			} else {
442 				availchk = 0;
443 			}
444 
445 			/*
446 			 * Try to allocate from a matching freemap class
447 			 * superblock.  If we are in relaxed mode we allocate
448 			 * from any freemap class superblock.
449 			 */
450 			if (availchk &&
451 			    (bmap->class == 0 || bmap->class == class ||
452 			    iter->relaxed)) {
453 				base_key = key + n * l0size;
454 				error = hammer2_bmap_alloc(hmp, bmap,
455 							   class, n,
456 							   (int)bref->key,
457 							   radix,
458 							   &base_key);
459 				if (error != HAMMER2_ERROR_ENOSPC) {
460 					key = base_key;
461 					break;
462 				}
463 			}
464 		}
465 
466 		/*
467 		 * We only know for sure that we can clear the bitmap bit
468 		 * if we scanned the entire array (start == 0) in relaxed
469 		 * mode.
470 		 */
471 		if (error == HAMMER2_ERROR_ENOSPC &&
472 		    start == 0 &&
473 		    iter->relaxed)
474 		{
475 			chain->bref.check.freemap.bigmask &=
476 				(uint32_t)~((size_t)1 << radix);
477 		}
478 		/* XXX also scan down from original count */
479 	}
480 
481 	if (error == 0) {
482 		/*
483 		 * Assert validity.  Must be beyond the static allocator used
484 		 * by newfs_hammer2 (and thus also beyond the aux area),
485 		 * not go past the volume size, and must not be in the
486 		 * reserved segment area for a zone.
487 		 */
488 		KKASSERT(key >= hmp->voldata.allocator_beg &&
489 			 key + bytes <= hmp->total_size);
490 		KKASSERT((key & HAMMER2_ZONE_MASK64) >= HAMMER2_ZONE_SEG);
491 		bref->data_off = key | radix;
492 
493 		/*
494 		 * Record dedupability.  The dedup bits are cleared
495 		 * when bulkfree transitions the freemap from 11->10,
496 		 * and asserted to be clear on the 10->00 transition.
497 		 *
498 		 * We must record the bitmask with the chain locked
499 		 * at the time we set the allocation bits to avoid
500 		 * racing a bulkfree.
501 		 */
502 		if (bref->type == HAMMER2_BREF_TYPE_DATA)
503 			hammer2_io_dedup_set(hmp, bref);
504 #if 0
505 		kprintf("alloc cp=%p %016jx %016jx using %016jx\n",
506 			chain,
507 			bref->key, bref->data_off, chain->bref.data_off);
508 #endif
509 	} else if (error == HAMMER2_ERROR_ENOSPC) {
510 		/*
511 		 * Return EAGAIN with next iteration in iter->bnext, or
512 		 * return ENOSPC if the allocation map has been exhausted.
513 		 */
514 		error = hammer2_freemap_iterate(parentp, &chain, iter);
515 	}
516 
517 	/*
518 	 * Cleanup
519 	 */
520 	if (chain) {
521 		hammer2_chain_unlock(chain);
522 		hammer2_chain_drop(chain);
523 	}
524 	return (error);
525 }
526 
527 /*
528  * Allocate (1<<radix) bytes from the bmap whos base data offset is (*basep).
529  *
530  * If the linear iterator is mid-block we use it directly (the bitmap should
531  * already be marked allocated), otherwise we search for a block in the
532  * bitmap that fits the allocation request.
533  *
534  * A partial bitmap allocation sets the minimum bitmap granularity (16KB)
535  * to fully allocated and adjusts the linear allocator to allow the
536  * remaining space to be allocated.
537  *
538  * sub_key is the lower 32 bits of the chain->bref.key for the chain whos
539  * bref is being allocated.  If the radix represents an allocation >= 16KB
540  * (aka HAMMER2_FREEMAP_BLOCK_RADIX) we try to use this key to select the
541  * blocks directly out of the bmap.
542  */
543 static
544 int
545 hammer2_bmap_alloc(hammer2_dev_t *hmp, hammer2_bmap_data_t *bmap,
546 		   uint16_t class, int n, int sub_key,
547 		   int radix, hammer2_key_t *basep)
548 {
549 	size_t size;
550 	size_t bgsize;
551 	int bmradix;
552 	hammer2_bitmap_t bmmask;
553 	int offset;
554 	int i;
555 	int j;
556 
557 	/*
558 	 * Take into account 2-bits per block when calculating bmradix.
559 	 */
560 	size = (size_t)1 << radix;
561 
562 	if (radix <= HAMMER2_FREEMAP_BLOCK_RADIX) {
563 		bmradix = 2;
564 		/* (16K) 2 bits per allocation block */
565 	} else {
566 		bmradix = (hammer2_bitmap_t)2 <<
567 			  (radix - HAMMER2_FREEMAP_BLOCK_RADIX);
568 		/* (32K-64K) 4, 8 bits per allocation block */
569 	}
570 
571 	/*
572 	 * Use the linear iterator to pack small allocations, otherwise
573 	 * fall-back to finding a free 16KB chunk.  The linear iterator
574 	 * is only valid when *NOT* on a freemap chunking boundary (16KB).
575 	 * If it is the bitmap must be scanned.  It can become invalid
576 	 * once we pack to the boundary.  We adjust it after a bitmap
577 	 * allocation only for sub-16KB allocations (so the perfectly good
578 	 * previous value can still be used for fragments when 16KB+
579 	 * allocations are made inbetween fragmentary allocations).
580 	 *
581 	 * Beware of hardware artifacts when bmradix == 64 (intermediate
582 	 * result can wind up being '1' instead of '0' if hardware masks
583 	 * bit-count & 63).
584 	 *
585 	 * NOTE: j needs to be even in the j= calculation.  As an artifact
586 	 *	 of the /2 division, our bitmask has to clear bit 0.
587 	 *
588 	 * NOTE: TODO this can leave little unallocatable fragments lying
589 	 *	 around.
590 	 */
591 	if (((uint32_t)bmap->linear & HAMMER2_FREEMAP_BLOCK_MASK) + size <=
592 	    HAMMER2_FREEMAP_BLOCK_SIZE &&
593 	    (bmap->linear & HAMMER2_FREEMAP_BLOCK_MASK) &&
594 	    bmap->linear < HAMMER2_SEGSIZE) {
595 		/*
596 		 * Use linear iterator if it is not block-aligned to avoid
597 		 * wasting space.
598 		 *
599 		 * Calculate the bitmapq[] index (i) and calculate the
600 		 * shift count within the 64-bit bitmapq[] entry.
601 		 *
602 		 * The freemap block size is 16KB, but each bitmap
603 		 * entry is two bits so use a little trick to get
604 		 * a (j) shift of 0, 2, 4, ... 62 in 16KB chunks.
605 		 */
606 		KKASSERT(bmap->linear >= 0 &&
607 			 bmap->linear + size <= HAMMER2_SEGSIZE &&
608 			 (bmap->linear & (HAMMER2_ALLOC_MIN - 1)) == 0);
609 		offset = bmap->linear;
610 		i = offset / (HAMMER2_SEGSIZE / HAMMER2_BMAP_ELEMENTS);
611 		j = (offset / (HAMMER2_FREEMAP_BLOCK_SIZE / 2)) & 62;
612 		bmmask = (bmradix == HAMMER2_BMAP_BITS_PER_ELEMENT) ?
613 			 HAMMER2_BMAP_ALLONES :
614 			 ((hammer2_bitmap_t)1 << bmradix) - 1;
615 		bmmask <<= j;
616 		bmap->linear = offset + size;
617 	} else {
618 		/*
619 		 * Try to index a starting point based on sub_key.  This
620 		 * attempts to restore sequential block ordering on-disk
621 		 * whenever possible, even if data is committed out of
622 		 * order.
623 		 *
624 		 * i - Index bitmapq[], full data range represented is
625 		 *     HAMMER2_BMAP_SIZE.
626 		 *
627 		 * j - Index within bitmapq[i], full data range represented is
628 		 *     HAMMER2_BMAP_INDEX_SIZE.
629 		 *
630 		 * WARNING!
631 		 */
632 		i = -1;
633 		j = -1;
634 
635 		switch(class >> 8) {
636 		case HAMMER2_BREF_TYPE_DATA:
637 			if (radix >= HAMMER2_FREEMAP_BLOCK_RADIX) {
638 				i = (sub_key & HAMMER2_BMAP_MASK) /
639 				    (HAMMER2_BMAP_SIZE / HAMMER2_BMAP_ELEMENTS);
640 				j = (sub_key & HAMMER2_BMAP_INDEX_MASK) /
641 				    (HAMMER2_BMAP_INDEX_SIZE /
642 				     HAMMER2_BMAP_BLOCKS_PER_ELEMENT);
643 				j = j * 2;
644 			}
645 			break;
646 		case HAMMER2_BREF_TYPE_INODE:
647 			break;
648 		default:
649 			break;
650 		}
651 		if (i >= 0) {
652 			KKASSERT(i < HAMMER2_BMAP_ELEMENTS &&
653 				 j < 2 * HAMMER2_BMAP_BLOCKS_PER_ELEMENT);
654 			KKASSERT(j + bmradix <= HAMMER2_BMAP_BITS_PER_ELEMENT);
655 			bmmask = (bmradix == HAMMER2_BMAP_BITS_PER_ELEMENT) ?
656 				 HAMMER2_BMAP_ALLONES :
657 				 ((hammer2_bitmap_t)1 << bmradix) - 1;
658 			bmmask <<= j;
659 
660 			if ((bmap->bitmapq[i] & bmmask) == 0)
661 				goto success;
662 		}
663 
664 		/*
665 		 * General element scan.
666 		 *
667 		 * WARNING: (j) is iterating a bit index (by 2's)
668 		 */
669 		for (i = 0; i < HAMMER2_BMAP_ELEMENTS; ++i) {
670 			bmmask = (bmradix == HAMMER2_BMAP_BITS_PER_ELEMENT) ?
671 				 HAMMER2_BMAP_ALLONES :
672 				 ((hammer2_bitmap_t)1 << bmradix) - 1;
673 			for (j = 0;
674 			     j < HAMMER2_BMAP_BITS_PER_ELEMENT;
675 			     j += bmradix) {
676 				if ((bmap->bitmapq[i] & bmmask) == 0)
677 					goto success;
678 				bmmask <<= bmradix;
679 			}
680 		}
681 		/*fragments might remain*/
682 		/*KKASSERT(bmap->avail == 0);*/
683 		return (HAMMER2_ERROR_ENOSPC);
684 success:
685 		offset = i * (HAMMER2_SEGSIZE / HAMMER2_BMAP_ELEMENTS) +
686 			 (j * (HAMMER2_FREEMAP_BLOCK_SIZE / 2));
687 		if (size & HAMMER2_FREEMAP_BLOCK_MASK)
688 			bmap->linear = offset + size;
689 	}
690 
691 	/* 8 x (64/2) -> 256 x 16K -> 4MB */
692 	KKASSERT(i >= 0 && i < HAMMER2_BMAP_ELEMENTS);
693 
694 	/*
695 	 * Optimize the buffer cache to avoid unnecessary read-before-write
696 	 * operations.
697 	 *
698 	 * The device block size could be larger than the allocation size
699 	 * so the actual bitmap test is somewhat more involved.  We have
700 	 * to use a compatible buffer size for this operation.
701 	 */
702 	if ((bmap->bitmapq[i] & bmmask) == 0 &&
703 	    HAMMER2_PBUFSIZE != size) {
704 		size_t psize = HAMMER2_PBUFSIZE;
705 		hammer2_off_t pmask = (hammer2_off_t)psize - 1;
706 		int pbmradix = (hammer2_bitmap_t)2 <<
707 					(HAMMER2_PBUFRADIX -
708 			       HAMMER2_FREEMAP_BLOCK_RADIX);
709 		hammer2_bitmap_t pbmmask;
710 		int pradix = hammer2_getradix(psize);
711 
712 		pbmmask = (pbmradix == HAMMER2_BMAP_BITS_PER_ELEMENT) ?
713 			HAMMER2_BMAP_ALLONES :
714 			((hammer2_bitmap_t)1 << pbmradix) - 1;
715 		while ((pbmmask & bmmask) == 0)
716 			pbmmask <<= pbmradix;
717 
718 #if 0
719 		kprintf("%016jx mask %016jx %016jx %016jx (%zd/%zd)\n",
720 			*basep + offset, bmap->bitmapq[i],
721 			pbmmask, bmmask, size, psize);
722 #endif
723 
724 		if ((bmap->bitmapq[i] & pbmmask) == 0) {
725 			hammer2_io_t *dio;
726 
727 			hammer2_io_newnz(hmp, class >> 8,
728 					(*basep + (offset & ~pmask)) |
729 					pradix, psize, &dio);
730 			hammer2_io_putblk(&dio);
731 		}
732 	}
733 
734 #if 0
735 	/*
736 	 * When initializing a new inode segment also attempt to initialize
737 	 * an adjacent segment.  Be careful not to index beyond the array
738 	 * bounds.
739 	 *
740 	 * We do this to try to localize inode accesses to improve
741 	 * directory scan rates.  XXX doesn't improve scan rates.
742 	 */
743 	if (size == HAMMER2_INODE_BYTES) {
744 		if (n & 1) {
745 			if (bmap[-1].radix == 0 && bmap[-1].avail)
746 				bmap[-1].radix = radix;
747 		} else {
748 			if (bmap[1].radix == 0 && bmap[1].avail)
749 				bmap[1].radix = radix;
750 		}
751 	}
752 #endif
753 	/*
754 	 * Calculate the bitmap-granular change in bgsize for the volume
755 	 * header.  We cannot use the fine-grained change here because
756 	 * the bulkfree code can't undo it.  If the bitmap element is already
757 	 * marked allocated it has already been accounted for.
758 	 */
759 	if (radix < HAMMER2_FREEMAP_BLOCK_RADIX) {
760 		if (bmap->bitmapq[i] & bmmask)
761 			bgsize = 0;
762 		else
763 			bgsize = HAMMER2_FREEMAP_BLOCK_SIZE;
764 	} else {
765 		bgsize = size;
766 	}
767 
768 	/*
769 	 * Adjust the bitmap, set the class (it might have been 0),
770 	 * and available bytes, update the allocation offset (*basep)
771 	 * from the L0 base to the actual offset.
772 	 *
773 	 * Do not override the class if doing a relaxed class allocation.
774 	 *
775 	 * avail must reflect the bitmap-granular availability.  The allocator
776 	 * tests will also check the linear iterator.
777 	 */
778 	bmap->bitmapq[i] |= bmmask;
779 	if (bmap->class == 0)
780 		bmap->class = class;
781 	bmap->avail -= bgsize;
782 	*basep += offset;
783 
784 	/*
785 	 * Adjust the volume header's allocator_free parameter.  This
786 	 * parameter has to be fixed up by bulkfree which has no way to
787 	 * figure out sub-16K chunking, so it must be adjusted by the
788 	 * bitmap-granular size.
789 	 */
790 	if (bgsize) {
791 		hammer2_voldata_lock(hmp);
792 		hammer2_voldata_modify(hmp);
793 		hmp->voldata.allocator_free -= bgsize;
794 		hammer2_voldata_unlock(hmp);
795 	}
796 
797 	return(0);
798 }
799 
800 /*
801  * Initialize a freemap for the storage area (in bytes) that begins at (key).
802  */
803 static
804 void
805 hammer2_freemap_init(hammer2_dev_t *hmp, hammer2_key_t key,
806 		     hammer2_chain_t *chain)
807 {
808 	hammer2_off_t lokey;
809 	hammer2_off_t hikey;
810 	hammer2_bmap_data_t *bmap;
811 	int count;
812 
813 	/*
814 	 * Calculate the portion of the 1GB map that should be initialized
815 	 * as free.  Portions below or after will be initialized as allocated.
816 	 * SEGMASK-align the areas so we don't have to worry about sub-scans
817 	 * or endianess when using memset.
818 	 *
819 	 * WARNING! It is possible for lokey to be larger than hikey if the
820 	 *	    entire 2GB segment is within the static allocation.
821 	 */
822 	/*
823 	 * (1) Ensure that all statically allocated space from newfs_hammer2
824 	 *     is marked allocated, and take it up to the level1 base for
825 	 *     this key.
826 	 */
827 	lokey = (hmp->voldata.allocator_beg + HAMMER2_SEGMASK64) &
828 		~HAMMER2_SEGMASK64;
829 	if (lokey < H2FMBASE(key, HAMMER2_FREEMAP_LEVEL1_RADIX))
830 		lokey = H2FMBASE(key, HAMMER2_FREEMAP_LEVEL1_RADIX);
831 
832 	/*
833 	 * (2) Ensure that the reserved area is marked allocated (typically
834 	 *     the first 4MB of each 2GB area being represented).  Since
835 	 *     each LEAF represents 1GB of storage and the zone is 2GB, we
836 	 *     have to adjust lowkey upward every other LEAF sequentially.
837 	 */
838 	if (lokey < H2FMZONEBASE(key) + HAMMER2_ZONE_SEG64)
839 		lokey = H2FMZONEBASE(key) + HAMMER2_ZONE_SEG64;
840 
841 	/*
842 	 * (3) Ensure that any trailing space at the end-of-volume is marked
843 	 *     allocated.
844 	 */
845 	hikey = key + HAMMER2_FREEMAP_LEVEL1_SIZE;
846 	if (hikey > hmp->total_size) {
847 		hikey = hmp->total_size & ~HAMMER2_SEGMASK64;
848 	}
849 
850 	/*
851 	 * Heuristic highest possible value
852 	 */
853 	chain->bref.check.freemap.avail = HAMMER2_FREEMAP_LEVEL1_SIZE;
854 	bmap = &chain->data->bmdata[0];
855 
856 	/*
857 	 * Initialize bitmap (bzero'd by caller)
858 	 */
859 	for (count = 0; count < HAMMER2_FREEMAP_COUNT; ++count) {
860 		if (key < lokey || key >= hikey) {
861 			memset(bmap->bitmapq, -1,
862 			       sizeof(bmap->bitmapq));
863 			bmap->avail = 0;
864 			bmap->linear = HAMMER2_SEGSIZE;
865 			chain->bref.check.freemap.avail -=
866 				HAMMER2_FREEMAP_LEVEL0_SIZE;
867 		} else {
868 			bmap->avail = HAMMER2_FREEMAP_LEVEL0_SIZE;
869 		}
870 		key += HAMMER2_FREEMAP_LEVEL0_SIZE;
871 		++bmap;
872 	}
873 }
874 
875 /*
876  * The current Level 1 freemap has been exhausted, iterate to the next
877  * one, return ENOSPC if no freemaps remain.
878  *
879  * At least two loops are required.  If we are not in relaxed mode and
880  * we run out of storage we enter relaxed mode and do a third loop.
881  * The relaxed mode is recorded back in the hmp so once we enter the mode
882  * we remain relaxed until stuff begins to get freed and only do 2 loops.
883  *
884  * XXX this should rotate back to the beginning to handle freed-up space
885  * XXX or use intermediate entries to locate free space. TODO
886  */
887 static int
888 hammer2_freemap_iterate(hammer2_chain_t **parentp, hammer2_chain_t **chainp,
889 			hammer2_fiterate_t *iter)
890 {
891 	hammer2_dev_t *hmp = (*parentp)->hmp;
892 
893 	iter->bnext &= ~HAMMER2_FREEMAP_LEVEL1_MASK;
894 	iter->bnext += HAMMER2_FREEMAP_LEVEL1_SIZE;
895 	if (iter->bnext >= hmp->total_size) {
896 		iter->bnext = 0;
897 		if (++iter->loops >= 2) {
898 			if (iter->relaxed == 0)
899 				iter->relaxed = 1;
900 			else
901 				return (HAMMER2_ERROR_ENOSPC);
902 		}
903 	}
904 	return(HAMMER2_ERROR_EAGAIN);
905 }
906 
907 /*
908  * Adjust the bit-pattern for data in the freemap bitmap according to
909  * (how).  This code is called from on-mount recovery to fixup (mark
910  * as allocated) blocks whos freemap upates might not have been committed
911  * in the last crash and is used by the bulk freemap scan to stage frees.
912  *
913  * WARNING! Cannot be called with a empty-data bref (radix == 0).
914  *
915  * XXX currently disabled when how == 0 (the normal real-time case).  At
916  * the moment we depend on the bulk freescan to actually free blocks.  It
917  * will still call this routine with a non-zero how to stage possible frees
918  * and to do the actual free.
919  */
920 void
921 hammer2_freemap_adjust(hammer2_dev_t *hmp, hammer2_blockref_t *bref,
922 		       int how)
923 {
924 	hammer2_off_t data_off = bref->data_off;
925 	hammer2_chain_t *chain;
926 	hammer2_chain_t *parent;
927 	hammer2_bmap_data_t *bmap;
928 	hammer2_key_t key;
929 	hammer2_key_t key_dummy;
930 	hammer2_off_t l1size;
931 	hammer2_off_t l1mask;
932 	hammer2_tid_t mtid;
933 	hammer2_bitmap_t *bitmap;
934 	const hammer2_bitmap_t bmmask00 = 0;
935 	//hammer2_bitmap_t bmmask01;
936 	//hammer2_bitmap_t bmmask10;
937 	hammer2_bitmap_t bmmask11;
938 	size_t bytes;
939 	uint16_t class;
940 	int radix;
941 	int start;
942 	int count;
943 	int modified = 0;
944 	int error;
945 	size_t bgsize = 0;
946 
947 	KKASSERT(how == HAMMER2_FREEMAP_DORECOVER);
948 
949 	KKASSERT(hmp->spmp);
950 	mtid = hammer2_trans_sub(hmp->spmp);
951 
952 	radix = (int)data_off & HAMMER2_OFF_MASK_RADIX;
953 	KKASSERT(radix != 0);
954 	data_off &= ~HAMMER2_OFF_MASK_RADIX;
955 	KKASSERT(radix <= HAMMER2_RADIX_MAX);
956 
957 	if (radix)
958 		bytes = (size_t)1 << radix;
959 	else
960 		bytes = 0;
961 	class = (bref->type << 8) | HAMMER2_PBUFRADIX;
962 
963 	/*
964 	 * We can't adjust the freemap for data allocations made by
965 	 * newfs_hammer2.
966 	 */
967 	if (data_off < hmp->voldata.allocator_beg)
968 		return;
969 
970 	KKASSERT((data_off & HAMMER2_ZONE_MASK64) >= HAMMER2_ZONE_SEG);
971 
972 	/*
973 	 * Lookup the level1 freemap chain.  The chain must exist.
974 	 */
975 	key = H2FMBASE(data_off, HAMMER2_FREEMAP_LEVEL1_RADIX);
976 	l1size = HAMMER2_FREEMAP_LEVEL1_SIZE;
977 	l1mask = l1size - 1;
978 
979 	parent = &hmp->fchain;
980 	hammer2_chain_ref(parent);
981 	hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS);
982 
983 	chain = hammer2_chain_lookup(&parent, &key_dummy, key, key + l1mask,
984 				     &error,
985 				     HAMMER2_LOOKUP_ALWAYS |
986 				     HAMMER2_LOOKUP_MATCHIND);
987 
988 	/*
989 	 * Stop early if we are trying to free something but no leaf exists.
990 	 */
991 	if (chain == NULL && how != HAMMER2_FREEMAP_DORECOVER) {
992 		kprintf("hammer2_freemap_adjust: %016jx: no chain\n",
993 			(intmax_t)bref->data_off);
994 		goto done;
995 	}
996 	if (chain->error) {
997 		kprintf("hammer2_freemap_adjust: %016jx: error %s\n",
998 			(intmax_t)bref->data_off,
999 			hammer2_error_str(chain->error));
1000 		hammer2_chain_unlock(chain);
1001 		hammer2_chain_drop(chain);
1002 		chain = NULL;
1003 		goto done;
1004 	}
1005 
1006 	/*
1007 	 * Create any missing leaf(s) if we are doing a recovery (marking
1008 	 * the block(s) as being allocated instead of being freed).  Be sure
1009 	 * to initialize the auxillary freemap tracking info in the
1010 	 * bref.check.freemap structure.
1011 	 */
1012 	if (chain == NULL && how == HAMMER2_FREEMAP_DORECOVER) {
1013 		error = hammer2_chain_create(&parent, &chain, NULL, hmp->spmp,
1014 				     HAMMER2_METH_DEFAULT,
1015 				     key, HAMMER2_FREEMAP_LEVEL1_RADIX,
1016 				     HAMMER2_BREF_TYPE_FREEMAP_LEAF,
1017 				     HAMMER2_FREEMAP_LEVELN_PSIZE,
1018 				     mtid, 0, 0);
1019 
1020 		if (hammer2_debug & 0x0040) {
1021 			kprintf("fixup create chain %p %016jx:%d\n",
1022 				chain, chain->bref.key, chain->bref.keybits);
1023 		}
1024 
1025 		if (error == 0) {
1026 			error = hammer2_chain_modify(chain, mtid, 0, 0);
1027 			KKASSERT(error == 0);
1028 			bzero(&chain->data->bmdata[0],
1029 			      HAMMER2_FREEMAP_LEVELN_PSIZE);
1030 			chain->bref.check.freemap.bigmask = (uint32_t)-1;
1031 			chain->bref.check.freemap.avail = l1size;
1032 			/* bref.methods should already be inherited */
1033 
1034 			hammer2_freemap_init(hmp, key, chain);
1035 		}
1036 		/* XXX handle error */
1037 	}
1038 
1039 #if FREEMAP_DEBUG
1040 	kprintf("FREEMAP ADJUST TYPE %d %016jx/%d DATA_OFF=%016jx\n",
1041 		chain->bref.type, chain->bref.key,
1042 		chain->bref.keybits, chain->bref.data_off);
1043 #endif
1044 
1045 	/*
1046 	 * Calculate the bitmask (runs in 2-bit pairs).
1047 	 */
1048 	start = ((int)(data_off >> HAMMER2_FREEMAP_BLOCK_RADIX) & 15) * 2;
1049 	//bmmask01 = (hammer2_bitmap_t)1 << start;
1050 	//bmmask10 = (hammer2_bitmap_t)2 << start;
1051 	bmmask11 = (hammer2_bitmap_t)3 << start;
1052 
1053 	/*
1054 	 * Fixup the bitmap.  Partial blocks cannot be fully freed unless
1055 	 * a bulk scan is able to roll them up.
1056 	 */
1057 	if (radix < HAMMER2_FREEMAP_BLOCK_RADIX) {
1058 		count = 1;
1059 #if 0
1060 		if (how == HAMMER2_FREEMAP_DOREALFREE)
1061 			how = HAMMER2_FREEMAP_DOMAYFREE;
1062 #endif
1063 	} else {
1064 		count = 1 << (radix - HAMMER2_FREEMAP_BLOCK_RADIX);
1065 	}
1066 
1067 	/*
1068 	 * [re]load the bmap and bitmap pointers.  Each bmap entry covers
1069 	 * a 4MB swath.  The bmap itself (LEVEL1) covers 2GB.
1070 	 *
1071 	 * Be sure to reset the linear iterator to ensure that the adjustment
1072 	 * is not ignored.
1073 	 */
1074 again:
1075 	bmap = &chain->data->bmdata[(int)(data_off >> HAMMER2_SEGRADIX) &
1076 				    (HAMMER2_FREEMAP_COUNT - 1)];
1077 	bitmap = &bmap->bitmapq[(int)(data_off >> (HAMMER2_SEGRADIX - 3)) & 7];
1078 
1079 	if (modified)
1080 		bmap->linear = 0;
1081 
1082 	while (count) {
1083 		KKASSERT(bmmask11);
1084 		if (how == HAMMER2_FREEMAP_DORECOVER) {
1085 			/*
1086 			 * Recovery request, mark as allocated.
1087 			 */
1088 			if ((*bitmap & bmmask11) != bmmask11) {
1089 				if (modified == 0) {
1090 					hammer2_chain_modify(chain, mtid, 0, 0);
1091 					modified = 1;
1092 					goto again;
1093 				}
1094 				if ((*bitmap & bmmask11) == bmmask00) {
1095 					bmap->avail -=
1096 						HAMMER2_FREEMAP_BLOCK_SIZE;
1097 					bgsize += HAMMER2_FREEMAP_BLOCK_SIZE;
1098 				}
1099 				if (bmap->class == 0)
1100 					bmap->class = class;
1101 				*bitmap |= bmmask11;
1102 				if (hammer2_debug & 0x0040) {
1103 					kprintf("hammer2_freemap_adjust: "
1104 						"fixup type=%02x "
1105 						"block=%016jx/%zd\n",
1106 						bref->type, data_off, bytes);
1107 				}
1108 			} else {
1109 				/*
1110 				kprintf("hammer2_freemap_adjust:  good "
1111 					"type=%02x block=%016jx/%zd\n",
1112 					bref->type, data_off, bytes);
1113 				*/
1114 			}
1115 		}
1116 #if 0
1117 		/*
1118 		 * XXX this stuff doesn't work, avail is miscalculated and
1119 		 * code 10 means something else now.
1120 		 */
1121 		else if ((*bitmap & bmmask11) == bmmask11) {
1122 			/*
1123 			 * Mayfree/Realfree request and bitmap is currently
1124 			 * marked as being fully allocated.
1125 			 */
1126 			if (!modified) {
1127 				hammer2_chain_modify(chain, 0);
1128 				modified = 1;
1129 				goto again;
1130 			}
1131 			if (how == HAMMER2_FREEMAP_DOREALFREE)
1132 				*bitmap &= ~bmmask11;
1133 			else
1134 				*bitmap = (*bitmap & ~bmmask11) | bmmask10;
1135 		} else if ((*bitmap & bmmask11) == bmmask10) {
1136 			/*
1137 			 * Mayfree/Realfree request and bitmap is currently
1138 			 * marked as being possibly freeable.
1139 			 */
1140 			if (how == HAMMER2_FREEMAP_DOREALFREE) {
1141 				if (!modified) {
1142 					hammer2_chain_modify(chain, 0);
1143 					modified = 1;
1144 					goto again;
1145 				}
1146 				*bitmap &= ~bmmask11;
1147 			}
1148 		} else {
1149 			/*
1150 			 * 01 - Not implemented, currently illegal state
1151 			 * 00 - Not allocated at all, illegal free.
1152 			 */
1153 			panic("hammer2_freemap_adjust: "
1154 			      "Illegal state %08x(%08x)",
1155 			      *bitmap, *bitmap & bmmask11);
1156 		}
1157 #endif
1158 		--count;
1159 		//bmmask01 <<= 2;
1160 		//bmmask10 <<= 2;
1161 		bmmask11 <<= 2;
1162 	}
1163 #if 0
1164 #if HAMMER2_BMAP_ELEMENTS != 8
1165 #error "hammer2_freemap.c: HAMMER2_BMAP_ELEMENTS expected to be 8"
1166 #endif
1167 	if (how == HAMMER2_FREEMAP_DOREALFREE && modified) {
1168 		bmap->avail += 1 << radix;
1169 		KKASSERT(bmap->avail <= HAMMER2_SEGSIZE);
1170 		if (bmap->avail == HAMMER2_SEGSIZE &&
1171 		    bmap->bitmapq[0] == 0 &&
1172 		    bmap->bitmapq[1] == 0 &&
1173 		    bmap->bitmapq[2] == 0 &&
1174 		    bmap->bitmapq[3] == 0 &&
1175 		    bmap->bitmapq[4] == 0 &&
1176 		    bmap->bitmapq[5] == 0 &&
1177 		    bmap->bitmapq[6] == 0 &&
1178 		    bmap->bitmapq[7] == 0) {
1179 			key = H2FMBASE(data_off, HAMMER2_FREEMAP_LEVEL0_RADIX);
1180 			kprintf("Freeseg %016jx\n", (intmax_t)key);
1181 			bmap->class = 0;
1182 		}
1183 	}
1184 #endif
1185 
1186 	/*
1187 	 * chain->bref.check.freemap.bigmask (XXX)
1188 	 *
1189 	 * Setting bigmask is a hint to the allocation code that there might
1190 	 * be something allocatable.  We also set this in recovery... it
1191 	 * doesn't hurt and we might want to use the hint for other validation
1192 	 * operations later on.
1193 	 *
1194 	 * We could calculate the largest possible allocation and set the
1195 	 * radixes that could fit, but its easier just to set bigmask to -1.
1196 	 */
1197 	if (modified) {
1198 		chain->bref.check.freemap.bigmask = -1;
1199 		hmp->freemap_relaxed = 0;	/* reset heuristic */
1200 	}
1201 
1202 	hammer2_chain_unlock(chain);
1203 	hammer2_chain_drop(chain);
1204 done:
1205 	hammer2_chain_unlock(parent);
1206 	hammer2_chain_drop(parent);
1207 
1208 	if (bgsize) {
1209 		hammer2_voldata_lock(hmp);
1210 		hammer2_voldata_modify(hmp);
1211 		hmp->voldata.allocator_free -= bgsize;
1212 		hammer2_voldata_unlock(hmp);
1213 	}
1214 }
1215 
1216 /*
1217  * Validate the freemap, in three stages.
1218  *
1219  * stage-1	ALLOCATED     -> POSSIBLY FREE
1220  *		POSSIBLY FREE -> POSSIBLY FREE (type corrected)
1221  *
1222  *	This transitions bitmap entries from ALLOCATED to POSSIBLY FREE.
1223  *	The POSSIBLY FREE state does not mean that a block is actually free
1224  *	and may be transitioned back to ALLOCATED in stage-2.
1225  *
1226  *	This is typically done during normal filesystem operations when
1227  *	something is deleted or a block is replaced.
1228  *
1229  *	This is done by bulkfree in-bulk after a memory-bounded meta-data
1230  *	scan to try to determine what might be freeable.
1231  *
1232  *	This can be done unconditionally through a freemap scan when the
1233  *	intention is to brute-force recover the proper state of the freemap.
1234  *
1235  * stage-2	POSSIBLY FREE -> ALLOCATED	(scan metadata topology)
1236  *
1237  *	This is done by bulkfree during a meta-data scan to ensure that
1238  *	all blocks still actually allocated by the filesystem are marked
1239  *	as such.
1240  *
1241  *	NOTE! Live filesystem transitions to POSSIBLY FREE can occur while
1242  *	      the bulkfree stage-2 and stage-3 is running.  The live filesystem
1243  *	      will use the alternative POSSIBLY FREE type (2) to prevent
1244  *	      stage-3 from improperly transitioning unvetted possibly-free
1245  *	      blocks to FREE.
1246  *
1247  * stage-3	POSSIBLY FREE (type 1) -> FREE	(scan freemap)
1248  *
1249  *	This is done by bulkfree to finalize POSSIBLY FREE states.
1250  *
1251  */
1252