xref: /openbmc/linux/fs/ocfs2/reservations.c (revision b830f94f)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /* -*- mode: c; c-basic-offset: 8; -*-
3  * vim: noexpandtab sw=8 ts=8 sts=0:
4  *
5  * reservations.c
6  *
7  * Allocation reservations implementation
8  *
9  * Some code borrowed from fs/ext3/balloc.c and is:
10  *
11  * Copyright (C) 1992, 1993, 1994, 1995
12  * Remy Card (card@masi.ibp.fr)
13  * Laboratoire MASI - Institut Blaise Pascal
14  * Universite Pierre et Marie Curie (Paris VI)
15  *
16  * The rest is copyright (C) 2010 Novell.  All rights reserved.
17  */
18 
19 #include <linux/fs.h>
20 #include <linux/types.h>
21 #include <linux/highmem.h>
22 #include <linux/bitops.h>
23 #include <linux/list.h>
24 
25 #include <cluster/masklog.h>
26 
27 #include "ocfs2.h"
28 #include "ocfs2_trace.h"
29 
30 #ifdef CONFIG_OCFS2_DEBUG_FS
31 #define OCFS2_CHECK_RESERVATIONS
32 #endif
33 
34 static DEFINE_SPINLOCK(resv_lock);
35 
36 #define	OCFS2_MIN_RESV_WINDOW_BITS	8
37 #define	OCFS2_MAX_RESV_WINDOW_BITS	1024
38 
39 int ocfs2_dir_resv_allowed(struct ocfs2_super *osb)
40 {
41 	return (osb->osb_resv_level && osb->osb_dir_resv_level);
42 }
43 
44 static unsigned int ocfs2_resv_window_bits(struct ocfs2_reservation_map *resmap,
45 					   struct ocfs2_alloc_reservation *resv)
46 {
47 	struct ocfs2_super *osb = resmap->m_osb;
48 	unsigned int bits;
49 
50 	if (!(resv->r_flags & OCFS2_RESV_FLAG_DIR)) {
51 		/* 8, 16, 32, 64, 128, 256, 512, 1024 */
52 		bits = 4 << osb->osb_resv_level;
53 	} else {
54 		bits = 4 << osb->osb_dir_resv_level;
55 	}
56 	return bits;
57 }
58 
59 static inline unsigned int ocfs2_resv_end(struct ocfs2_alloc_reservation *resv)
60 {
61 	if (resv->r_len)
62 		return resv->r_start + resv->r_len - 1;
63 	return resv->r_start;
64 }
65 
66 static inline int ocfs2_resv_empty(struct ocfs2_alloc_reservation *resv)
67 {
68 	return !!(resv->r_len == 0);
69 }
70 
71 static inline int ocfs2_resmap_disabled(struct ocfs2_reservation_map *resmap)
72 {
73 	if (resmap->m_osb->osb_resv_level == 0)
74 		return 1;
75 	return 0;
76 }
77 
78 static void ocfs2_dump_resv(struct ocfs2_reservation_map *resmap)
79 {
80 	struct ocfs2_super *osb = resmap->m_osb;
81 	struct rb_node *node;
82 	struct ocfs2_alloc_reservation *resv;
83 	int i = 0;
84 
85 	mlog(ML_NOTICE, "Dumping resmap for device %s. Bitmap length: %u\n",
86 	     osb->dev_str, resmap->m_bitmap_len);
87 
88 	node = rb_first(&resmap->m_reservations);
89 	while (node) {
90 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
91 
92 		mlog(ML_NOTICE, "start: %u\tend: %u\tlen: %u\tlast_start: %u"
93 		     "\tlast_len: %u\n", resv->r_start,
94 		     ocfs2_resv_end(resv), resv->r_len, resv->r_last_start,
95 		     resv->r_last_len);
96 
97 		node = rb_next(node);
98 		i++;
99 	}
100 
101 	mlog(ML_NOTICE, "%d reservations found. LRU follows\n", i);
102 
103 	i = 0;
104 	list_for_each_entry(resv, &resmap->m_lru, r_lru) {
105 		mlog(ML_NOTICE, "LRU(%d) start: %u\tend: %u\tlen: %u\t"
106 		     "last_start: %u\tlast_len: %u\n", i, resv->r_start,
107 		     ocfs2_resv_end(resv), resv->r_len, resv->r_last_start,
108 		     resv->r_last_len);
109 
110 		i++;
111 	}
112 }
113 
114 #ifdef OCFS2_CHECK_RESERVATIONS
115 static int ocfs2_validate_resmap_bits(struct ocfs2_reservation_map *resmap,
116 				      int i,
117 				      struct ocfs2_alloc_reservation *resv)
118 {
119 	char *disk_bitmap = resmap->m_disk_bitmap;
120 	unsigned int start = resv->r_start;
121 	unsigned int end = ocfs2_resv_end(resv);
122 
123 	while (start <= end) {
124 		if (ocfs2_test_bit(start, disk_bitmap)) {
125 			mlog(ML_ERROR,
126 			     "reservation %d covers an allocated area "
127 			     "starting at bit %u!\n", i, start);
128 			return 1;
129 		}
130 
131 		start++;
132 	}
133 	return 0;
134 }
135 
136 static void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
137 {
138 	unsigned int off = 0;
139 	int i = 0;
140 	struct rb_node *node;
141 	struct ocfs2_alloc_reservation *resv;
142 
143 	node = rb_first(&resmap->m_reservations);
144 	while (node) {
145 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
146 
147 		if (i > 0 && resv->r_start <= off) {
148 			mlog(ML_ERROR, "reservation %d has bad start off!\n",
149 			     i);
150 			goto bad;
151 		}
152 
153 		if (resv->r_len == 0) {
154 			mlog(ML_ERROR, "reservation %d has no length!\n",
155 			     i);
156 			goto bad;
157 		}
158 
159 		if (resv->r_start > ocfs2_resv_end(resv)) {
160 			mlog(ML_ERROR, "reservation %d has invalid range!\n",
161 			     i);
162 			goto bad;
163 		}
164 
165 		if (ocfs2_resv_end(resv) >= resmap->m_bitmap_len) {
166 			mlog(ML_ERROR, "reservation %d extends past bitmap!\n",
167 			     i);
168 			goto bad;
169 		}
170 
171 		if (ocfs2_validate_resmap_bits(resmap, i, resv))
172 			goto bad;
173 
174 		off = ocfs2_resv_end(resv);
175 		node = rb_next(node);
176 
177 		i++;
178 	}
179 	return;
180 
181 bad:
182 	ocfs2_dump_resv(resmap);
183 	BUG();
184 }
185 #else
186 static inline void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
187 {
188 
189 }
190 #endif
191 
192 void ocfs2_resv_init_once(struct ocfs2_alloc_reservation *resv)
193 {
194 	memset(resv, 0, sizeof(*resv));
195 	INIT_LIST_HEAD(&resv->r_lru);
196 }
197 
198 void ocfs2_resv_set_type(struct ocfs2_alloc_reservation *resv,
199 			 unsigned int flags)
200 {
201 	BUG_ON(flags & ~OCFS2_RESV_TYPES);
202 
203 	resv->r_flags |= flags;
204 }
205 
206 int ocfs2_resmap_init(struct ocfs2_super *osb,
207 		      struct ocfs2_reservation_map *resmap)
208 {
209 	memset(resmap, 0, sizeof(*resmap));
210 
211 	resmap->m_osb = osb;
212 	resmap->m_reservations = RB_ROOT;
213 	/* m_bitmap_len is initialized to zero by the above memset. */
214 	INIT_LIST_HEAD(&resmap->m_lru);
215 
216 	return 0;
217 }
218 
219 static void ocfs2_resv_mark_lru(struct ocfs2_reservation_map *resmap,
220 				struct ocfs2_alloc_reservation *resv)
221 {
222 	assert_spin_locked(&resv_lock);
223 
224 	if (!list_empty(&resv->r_lru))
225 		list_del_init(&resv->r_lru);
226 
227 	list_add_tail(&resv->r_lru, &resmap->m_lru);
228 }
229 
230 static void __ocfs2_resv_trunc(struct ocfs2_alloc_reservation *resv)
231 {
232 	resv->r_len = 0;
233 	resv->r_start = 0;
234 }
235 
236 static void ocfs2_resv_remove(struct ocfs2_reservation_map *resmap,
237 			      struct ocfs2_alloc_reservation *resv)
238 {
239 	if (resv->r_flags & OCFS2_RESV_FLAG_INUSE) {
240 		list_del_init(&resv->r_lru);
241 		rb_erase(&resv->r_node, &resmap->m_reservations);
242 		resv->r_flags &= ~OCFS2_RESV_FLAG_INUSE;
243 	}
244 }
245 
246 static void __ocfs2_resv_discard(struct ocfs2_reservation_map *resmap,
247 				 struct ocfs2_alloc_reservation *resv)
248 {
249 	assert_spin_locked(&resv_lock);
250 
251 	__ocfs2_resv_trunc(resv);
252 	/*
253 	 * last_len and last_start no longer make sense if
254 	 * we're changing the range of our allocations.
255 	 */
256 	resv->r_last_len = resv->r_last_start = 0;
257 
258 	ocfs2_resv_remove(resmap, resv);
259 }
260 
261 /* does nothing if 'resv' is null */
262 void ocfs2_resv_discard(struct ocfs2_reservation_map *resmap,
263 			struct ocfs2_alloc_reservation *resv)
264 {
265 	if (resv) {
266 		spin_lock(&resv_lock);
267 		__ocfs2_resv_discard(resmap, resv);
268 		spin_unlock(&resv_lock);
269 	}
270 }
271 
272 static void ocfs2_resmap_clear_all_resv(struct ocfs2_reservation_map *resmap)
273 {
274 	struct rb_node *node;
275 	struct ocfs2_alloc_reservation *resv;
276 
277 	assert_spin_locked(&resv_lock);
278 
279 	while ((node = rb_last(&resmap->m_reservations)) != NULL) {
280 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
281 
282 		__ocfs2_resv_discard(resmap, resv);
283 	}
284 }
285 
286 void ocfs2_resmap_restart(struct ocfs2_reservation_map *resmap,
287 			  unsigned int clen, char *disk_bitmap)
288 {
289 	if (ocfs2_resmap_disabled(resmap))
290 		return;
291 
292 	spin_lock(&resv_lock);
293 
294 	ocfs2_resmap_clear_all_resv(resmap);
295 	resmap->m_bitmap_len = clen;
296 	resmap->m_disk_bitmap = disk_bitmap;
297 
298 	spin_unlock(&resv_lock);
299 }
300 
301 void ocfs2_resmap_uninit(struct ocfs2_reservation_map *resmap)
302 {
303 	/* Does nothing for now. Keep this around for API symmetry */
304 }
305 
306 static void ocfs2_resv_insert(struct ocfs2_reservation_map *resmap,
307 			      struct ocfs2_alloc_reservation *new)
308 {
309 	struct rb_root *root = &resmap->m_reservations;
310 	struct rb_node *parent = NULL;
311 	struct rb_node **p = &root->rb_node;
312 	struct ocfs2_alloc_reservation *tmp;
313 
314 	assert_spin_locked(&resv_lock);
315 
316 	trace_ocfs2_resv_insert(new->r_start, new->r_len);
317 
318 	while (*p) {
319 		parent = *p;
320 
321 		tmp = rb_entry(parent, struct ocfs2_alloc_reservation, r_node);
322 
323 		if (new->r_start < tmp->r_start) {
324 			p = &(*p)->rb_left;
325 
326 			/*
327 			 * This is a good place to check for
328 			 * overlapping reservations.
329 			 */
330 			BUG_ON(ocfs2_resv_end(new) >= tmp->r_start);
331 		} else if (new->r_start > ocfs2_resv_end(tmp)) {
332 			p = &(*p)->rb_right;
333 		} else {
334 			/* This should never happen! */
335 			mlog(ML_ERROR, "Duplicate reservation window!\n");
336 			BUG();
337 		}
338 	}
339 
340 	rb_link_node(&new->r_node, parent, p);
341 	rb_insert_color(&new->r_node, root);
342 	new->r_flags |= OCFS2_RESV_FLAG_INUSE;
343 
344 	ocfs2_resv_mark_lru(resmap, new);
345 
346 	ocfs2_check_resmap(resmap);
347 }
348 
349 /**
350  * ocfs2_find_resv_lhs() - find the window which contains goal
351  * @resmap: reservation map to search
352  * @goal: which bit to search for
353  *
354  * If a window containing that goal is not found, we return the window
355  * which comes before goal. Returns NULL on empty rbtree or no window
356  * before goal.
357  */
358 static struct ocfs2_alloc_reservation *
359 ocfs2_find_resv_lhs(struct ocfs2_reservation_map *resmap, unsigned int goal)
360 {
361 	struct ocfs2_alloc_reservation *resv = NULL;
362 	struct ocfs2_alloc_reservation *prev_resv = NULL;
363 	struct rb_node *node = resmap->m_reservations.rb_node;
364 
365 	assert_spin_locked(&resv_lock);
366 
367 	if (!node)
368 		return NULL;
369 
370 	node = rb_first(&resmap->m_reservations);
371 	while (node) {
372 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
373 
374 		if (resv->r_start <= goal && ocfs2_resv_end(resv) >= goal)
375 			break;
376 
377 		/* Check if we overshot the reservation just before goal? */
378 		if (resv->r_start > goal) {
379 			resv = prev_resv;
380 			break;
381 		}
382 
383 		prev_resv = resv;
384 		node = rb_next(node);
385 	}
386 
387 	return resv;
388 }
389 
390 /*
391  * We are given a range within the bitmap, which corresponds to a gap
392  * inside the reservations tree (search_start, search_len). The range
393  * can be anything from the whole bitmap, to a gap between
394  * reservations.
395  *
396  * The start value of *rstart is insignificant.
397  *
398  * This function searches the bitmap range starting at search_start
399  * with length search_len for a set of contiguous free bits. We try
400  * to find up to 'wanted' bits, but can sometimes return less.
401  *
402  * Returns the length of allocation, 0 if no free bits are found.
403  *
404  * *cstart and *clen will also be populated with the result.
405  */
406 static int ocfs2_resmap_find_free_bits(struct ocfs2_reservation_map *resmap,
407 				       unsigned int wanted,
408 				       unsigned int search_start,
409 				       unsigned int search_len,
410 				       unsigned int *rstart,
411 				       unsigned int *rlen)
412 {
413 	void *bitmap = resmap->m_disk_bitmap;
414 	unsigned int best_start, best_len = 0;
415 	int offset, start, found;
416 
417 	trace_ocfs2_resmap_find_free_bits_begin(search_start, search_len,
418 						wanted, resmap->m_bitmap_len);
419 
420 	found = best_start = best_len = 0;
421 
422 	start = search_start;
423 	while ((offset = ocfs2_find_next_zero_bit(bitmap, resmap->m_bitmap_len,
424 						 start)) != -1) {
425 		/* Search reached end of the region */
426 		if (offset >= (search_start + search_len))
427 			break;
428 
429 		if (offset == start) {
430 			/* we found a zero */
431 			found++;
432 			/* move start to the next bit to test */
433 			start++;
434 		} else {
435 			/* got a zero after some ones */
436 			found = 1;
437 			start = offset + 1;
438 		}
439 		if (found > best_len) {
440 			best_len = found;
441 			best_start = start - found;
442 		}
443 
444 		if (found >= wanted)
445 			break;
446 	}
447 
448 	if (best_len == 0)
449 		return 0;
450 
451 	if (best_len >= wanted)
452 		best_len = wanted;
453 
454 	*rlen = best_len;
455 	*rstart = best_start;
456 
457 	trace_ocfs2_resmap_find_free_bits_end(best_start, best_len);
458 
459 	return *rlen;
460 }
461 
462 static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
463 				     struct ocfs2_alloc_reservation *resv,
464 				     unsigned int goal, unsigned int wanted)
465 {
466 	struct rb_root *root = &resmap->m_reservations;
467 	unsigned int gap_start, gap_end, gap_len;
468 	struct ocfs2_alloc_reservation *prev_resv, *next_resv;
469 	struct rb_node *prev, *next;
470 	unsigned int cstart, clen;
471 	unsigned int best_start = 0, best_len = 0;
472 
473 	/*
474 	 * Nasty cases to consider:
475 	 *
476 	 * - rbtree is empty
477 	 * - our window should be first in all reservations
478 	 * - our window should be last in all reservations
479 	 * - need to make sure we don't go past end of bitmap
480 	 */
481 	trace_ocfs2_resv_find_window_begin(resv->r_start, ocfs2_resv_end(resv),
482 					   goal, wanted, RB_EMPTY_ROOT(root));
483 
484 	assert_spin_locked(&resv_lock);
485 
486 	if (RB_EMPTY_ROOT(root)) {
487 		/*
488 		 * Easiest case - empty tree. We can just take
489 		 * whatever window of free bits we want.
490 		 */
491 		clen = ocfs2_resmap_find_free_bits(resmap, wanted, goal,
492 						   resmap->m_bitmap_len - goal,
493 						   &cstart, &clen);
494 
495 		/*
496 		 * This should never happen - the local alloc window
497 		 * will always have free bits when we're called.
498 		 */
499 		BUG_ON(goal == 0 && clen == 0);
500 
501 		if (clen == 0)
502 			return;
503 
504 		resv->r_start = cstart;
505 		resv->r_len = clen;
506 
507 		ocfs2_resv_insert(resmap, resv);
508 		return;
509 	}
510 
511 	prev_resv = ocfs2_find_resv_lhs(resmap, goal);
512 
513 	if (prev_resv == NULL) {
514 		/*
515 		 * A NULL here means that the search code couldn't
516 		 * find a window that starts before goal.
517 		 *
518 		 * However, we can take the first window after goal,
519 		 * which is also by definition, the leftmost window in
520 		 * the entire tree. If we can find free bits in the
521 		 * gap between goal and the LHS window, then the
522 		 * reservation can safely be placed there.
523 		 *
524 		 * Otherwise we fall back to a linear search, checking
525 		 * the gaps in between windows for a place to
526 		 * allocate.
527 		 */
528 
529 		next = rb_first(root);
530 		next_resv = rb_entry(next, struct ocfs2_alloc_reservation,
531 				     r_node);
532 
533 		/*
534 		 * The search should never return such a window. (see
535 		 * comment above
536 		 */
537 		if (next_resv->r_start <= goal) {
538 			mlog(ML_ERROR, "goal: %u next_resv: start %u len %u\n",
539 			     goal, next_resv->r_start, next_resv->r_len);
540 			ocfs2_dump_resv(resmap);
541 			BUG();
542 		}
543 
544 		clen = ocfs2_resmap_find_free_bits(resmap, wanted, goal,
545 						   next_resv->r_start - goal,
546 						   &cstart, &clen);
547 		if (clen) {
548 			best_len = clen;
549 			best_start = cstart;
550 			if (best_len == wanted)
551 				goto out_insert;
552 		}
553 
554 		prev_resv = next_resv;
555 		next_resv = NULL;
556 	}
557 
558 	trace_ocfs2_resv_find_window_prev(prev_resv->r_start,
559 					  ocfs2_resv_end(prev_resv));
560 
561 	prev = &prev_resv->r_node;
562 
563 	/* Now we do a linear search for a window, starting at 'prev_rsv' */
564 	while (1) {
565 		next = rb_next(prev);
566 		if (next) {
567 			next_resv = rb_entry(next,
568 					     struct ocfs2_alloc_reservation,
569 					     r_node);
570 
571 			gap_start = ocfs2_resv_end(prev_resv) + 1;
572 			gap_end = next_resv->r_start - 1;
573 			gap_len = gap_end - gap_start + 1;
574 		} else {
575 			/*
576 			 * We're at the rightmost edge of the
577 			 * tree. See if a reservation between this
578 			 * window and the end of the bitmap will work.
579 			 */
580 			gap_start = ocfs2_resv_end(prev_resv) + 1;
581 			gap_len = resmap->m_bitmap_len - gap_start;
582 			gap_end = resmap->m_bitmap_len - 1;
583 		}
584 
585 		trace_ocfs2_resv_find_window_next(next ? next_resv->r_start: -1,
586 					next ? ocfs2_resv_end(next_resv) : -1);
587 		/*
588 		 * No need to check this gap if we have already found
589 		 * a larger region of free bits.
590 		 */
591 		if (gap_len <= best_len)
592 			goto next_resv;
593 
594 		clen = ocfs2_resmap_find_free_bits(resmap, wanted, gap_start,
595 						   gap_len, &cstart, &clen);
596 		if (clen == wanted) {
597 			best_len = clen;
598 			best_start = cstart;
599 			goto out_insert;
600 		} else if (clen > best_len) {
601 			best_len = clen;
602 			best_start = cstart;
603 		}
604 
605 next_resv:
606 		if (!next)
607 			break;
608 
609 		prev = next;
610 		prev_resv = rb_entry(prev, struct ocfs2_alloc_reservation,
611 				     r_node);
612 	}
613 
614 out_insert:
615 	if (best_len) {
616 		resv->r_start = best_start;
617 		resv->r_len = best_len;
618 		ocfs2_resv_insert(resmap, resv);
619 	}
620 }
621 
622 static void ocfs2_cannibalize_resv(struct ocfs2_reservation_map *resmap,
623 				   struct ocfs2_alloc_reservation *resv,
624 				   unsigned int wanted)
625 {
626 	struct ocfs2_alloc_reservation *lru_resv;
627 	int tmpwindow = !!(resv->r_flags & OCFS2_RESV_FLAG_TMP);
628 	unsigned int min_bits;
629 
630 	if (!tmpwindow)
631 		min_bits = ocfs2_resv_window_bits(resmap, resv) >> 1;
632 	else
633 		min_bits = wanted; /* We at know the temp window will use all
634 				    * of these bits */
635 
636 	/*
637 	 * Take the first reservation off the LRU as our 'target'. We
638 	 * don't try to be smart about it. There might be a case for
639 	 * searching based on size but I don't have enough data to be
640 	 * sure. --Mark (3/16/2010)
641 	 */
642 	lru_resv = list_first_entry(&resmap->m_lru,
643 				    struct ocfs2_alloc_reservation, r_lru);
644 
645 	trace_ocfs2_cannibalize_resv_begin(lru_resv->r_start,
646 					   lru_resv->r_len,
647 					   ocfs2_resv_end(lru_resv));
648 
649 	/*
650 	 * Cannibalize (some or all) of the target reservation and
651 	 * feed it to the current window.
652 	 */
653 	if (lru_resv->r_len <= min_bits) {
654 		/*
655 		 * Discard completely if size is less than or equal to a
656 		 * reasonable threshold - 50% of window bits for non temporary
657 		 * windows.
658 		 */
659 		resv->r_start = lru_resv->r_start;
660 		resv->r_len = lru_resv->r_len;
661 
662 		__ocfs2_resv_discard(resmap, lru_resv);
663 	} else {
664 		unsigned int shrink;
665 		if (tmpwindow)
666 			shrink = min_bits;
667 		else
668 			shrink = lru_resv->r_len / 2;
669 
670 		lru_resv->r_len -= shrink;
671 
672 		resv->r_start = ocfs2_resv_end(lru_resv) + 1;
673 		resv->r_len = shrink;
674 	}
675 
676 	trace_ocfs2_cannibalize_resv_end(resv->r_start, ocfs2_resv_end(resv),
677 					 resv->r_len, resv->r_last_start,
678 					 resv->r_last_len);
679 
680 	ocfs2_resv_insert(resmap, resv);
681 }
682 
683 static void ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
684 				   struct ocfs2_alloc_reservation *resv,
685 				   unsigned int wanted)
686 {
687 	unsigned int goal = 0;
688 
689 	BUG_ON(!ocfs2_resv_empty(resv));
690 
691 	/*
692 	 * Begin by trying to get a window as close to the previous
693 	 * one as possible. Using the most recent allocation as a
694 	 * start goal makes sense.
695 	 */
696 	if (resv->r_last_len) {
697 		goal = resv->r_last_start + resv->r_last_len;
698 		if (goal >= resmap->m_bitmap_len)
699 			goal = 0;
700 	}
701 
702 	__ocfs2_resv_find_window(resmap, resv, goal, wanted);
703 
704 	/* Search from last alloc didn't work, try once more from beginning. */
705 	if (ocfs2_resv_empty(resv) && goal != 0)
706 		__ocfs2_resv_find_window(resmap, resv, 0, wanted);
707 
708 	if (ocfs2_resv_empty(resv)) {
709 		/*
710 		 * Still empty? Pull oldest one off the LRU, remove it from
711 		 * tree, put this one in it's place.
712 		 */
713 		ocfs2_cannibalize_resv(resmap, resv, wanted);
714 	}
715 
716 	BUG_ON(ocfs2_resv_empty(resv));
717 }
718 
719 int ocfs2_resmap_resv_bits(struct ocfs2_reservation_map *resmap,
720 			   struct ocfs2_alloc_reservation *resv,
721 			   int *cstart, int *clen)
722 {
723 	if (resv == NULL || ocfs2_resmap_disabled(resmap))
724 		return -ENOSPC;
725 
726 	spin_lock(&resv_lock);
727 
728 	if (ocfs2_resv_empty(resv)) {
729 		/*
730 		 * We don't want to over-allocate for temporary
731 		 * windows. Otherwise, we run the risk of fragmenting the
732 		 * allocation space.
733 		 */
734 		unsigned int wanted = ocfs2_resv_window_bits(resmap, resv);
735 
736 		if ((resv->r_flags & OCFS2_RESV_FLAG_TMP) || wanted < *clen)
737 			wanted = *clen;
738 
739 		/*
740 		 * Try to get a window here. If it works, we must fall
741 		 * through and test the bitmap . This avoids some
742 		 * ping-ponging of windows due to non-reserved space
743 		 * being allocation before we initialize a window for
744 		 * that inode.
745 		 */
746 		ocfs2_resv_find_window(resmap, resv, wanted);
747 		trace_ocfs2_resmap_resv_bits(resv->r_start, resv->r_len);
748 	}
749 
750 	BUG_ON(ocfs2_resv_empty(resv));
751 
752 	*cstart = resv->r_start;
753 	*clen = resv->r_len;
754 
755 	spin_unlock(&resv_lock);
756 	return 0;
757 }
758 
759 static void
760 	ocfs2_adjust_resv_from_alloc(struct ocfs2_reservation_map *resmap,
761 				     struct ocfs2_alloc_reservation *resv,
762 				     unsigned int start, unsigned int end)
763 {
764 	unsigned int rhs = 0;
765 	unsigned int old_end = ocfs2_resv_end(resv);
766 
767 	BUG_ON(start != resv->r_start || old_end < end);
768 
769 	/*
770 	 * Completely used? We can remove it then.
771 	 */
772 	if (old_end == end) {
773 		__ocfs2_resv_discard(resmap, resv);
774 		return;
775 	}
776 
777 	rhs = old_end - end;
778 
779 	/*
780 	 * This should have been trapped above.
781 	 */
782 	BUG_ON(rhs == 0);
783 
784 	resv->r_start = end + 1;
785 	resv->r_len = old_end - resv->r_start + 1;
786 }
787 
788 void ocfs2_resmap_claimed_bits(struct ocfs2_reservation_map *resmap,
789 			       struct ocfs2_alloc_reservation *resv,
790 			       u32 cstart, u32 clen)
791 {
792 	unsigned int cend = cstart + clen - 1;
793 
794 	if (resmap == NULL || ocfs2_resmap_disabled(resmap))
795 		return;
796 
797 	if (resv == NULL)
798 		return;
799 
800 	BUG_ON(cstart != resv->r_start);
801 
802 	spin_lock(&resv_lock);
803 
804 	trace_ocfs2_resmap_claimed_bits_begin(cstart, cend, clen, resv->r_start,
805 					      ocfs2_resv_end(resv), resv->r_len,
806 					      resv->r_last_start,
807 					      resv->r_last_len);
808 
809 	BUG_ON(cstart < resv->r_start);
810 	BUG_ON(cstart > ocfs2_resv_end(resv));
811 	BUG_ON(cend > ocfs2_resv_end(resv));
812 
813 	ocfs2_adjust_resv_from_alloc(resmap, resv, cstart, cend);
814 	resv->r_last_start = cstart;
815 	resv->r_last_len = clen;
816 
817 	/*
818 	 * May have been discarded above from
819 	 * ocfs2_adjust_resv_from_alloc().
820 	 */
821 	if (!ocfs2_resv_empty(resv))
822 		ocfs2_resv_mark_lru(resmap, resv);
823 
824 	trace_ocfs2_resmap_claimed_bits_end(resv->r_start, ocfs2_resv_end(resv),
825 					    resv->r_len, resv->r_last_start,
826 					    resv->r_last_len);
827 
828 	ocfs2_check_resmap(resmap);
829 
830 	spin_unlock(&resv_lock);
831 }
832