xref: /openbmc/linux/fs/ocfs2/reservations.c (revision ed4bc189)
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 int ocfs2_dir_resv_allowed(struct ocfs2_super *osb)
37 {
38 	return (osb->osb_resv_level && osb->osb_dir_resv_level);
39 }
40 
41 static unsigned int ocfs2_resv_window_bits(struct ocfs2_reservation_map *resmap,
42 					   struct ocfs2_alloc_reservation *resv)
43 {
44 	struct ocfs2_super *osb = resmap->m_osb;
45 	unsigned int bits;
46 
47 	if (!(resv->r_flags & OCFS2_RESV_FLAG_DIR)) {
48 		/* 8, 16, 32, 64, 128, 256, 512, 1024 */
49 		bits = 4 << osb->osb_resv_level;
50 	} else {
51 		bits = 4 << osb->osb_dir_resv_level;
52 	}
53 	return bits;
54 }
55 
56 static inline unsigned int ocfs2_resv_end(struct ocfs2_alloc_reservation *resv)
57 {
58 	if (resv->r_len)
59 		return resv->r_start + resv->r_len - 1;
60 	return resv->r_start;
61 }
62 
63 static inline int ocfs2_resv_empty(struct ocfs2_alloc_reservation *resv)
64 {
65 	return !!(resv->r_len == 0);
66 }
67 
68 static inline int ocfs2_resmap_disabled(struct ocfs2_reservation_map *resmap)
69 {
70 	if (resmap->m_osb->osb_resv_level == 0)
71 		return 1;
72 	return 0;
73 }
74 
75 static void ocfs2_dump_resv(struct ocfs2_reservation_map *resmap)
76 {
77 	struct ocfs2_super *osb = resmap->m_osb;
78 	struct rb_node *node;
79 	struct ocfs2_alloc_reservation *resv;
80 	int i = 0;
81 
82 	mlog(ML_NOTICE, "Dumping resmap for device %s. Bitmap length: %u\n",
83 	     osb->dev_str, resmap->m_bitmap_len);
84 
85 	node = rb_first(&resmap->m_reservations);
86 	while (node) {
87 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
88 
89 		mlog(ML_NOTICE, "start: %u\tend: %u\tlen: %u\tlast_start: %u"
90 		     "\tlast_len: %u\n", resv->r_start,
91 		     ocfs2_resv_end(resv), resv->r_len, resv->r_last_start,
92 		     resv->r_last_len);
93 
94 		node = rb_next(node);
95 		i++;
96 	}
97 
98 	mlog(ML_NOTICE, "%d reservations found. LRU follows\n", i);
99 
100 	i = 0;
101 	list_for_each_entry(resv, &resmap->m_lru, r_lru) {
102 		mlog(ML_NOTICE, "LRU(%d) start: %u\tend: %u\tlen: %u\t"
103 		     "last_start: %u\tlast_len: %u\n", i, resv->r_start,
104 		     ocfs2_resv_end(resv), resv->r_len, resv->r_last_start,
105 		     resv->r_last_len);
106 
107 		i++;
108 	}
109 }
110 
111 #ifdef OCFS2_CHECK_RESERVATIONS
112 static int ocfs2_validate_resmap_bits(struct ocfs2_reservation_map *resmap,
113 				      int i,
114 				      struct ocfs2_alloc_reservation *resv)
115 {
116 	char *disk_bitmap = resmap->m_disk_bitmap;
117 	unsigned int start = resv->r_start;
118 	unsigned int end = ocfs2_resv_end(resv);
119 
120 	while (start <= end) {
121 		if (ocfs2_test_bit(start, disk_bitmap)) {
122 			mlog(ML_ERROR,
123 			     "reservation %d covers an allocated area "
124 			     "starting at bit %u!\n", i, start);
125 			return 1;
126 		}
127 
128 		start++;
129 	}
130 	return 0;
131 }
132 
133 static void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
134 {
135 	unsigned int off = 0;
136 	int i = 0;
137 	struct rb_node *node;
138 	struct ocfs2_alloc_reservation *resv;
139 
140 	node = rb_first(&resmap->m_reservations);
141 	while (node) {
142 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
143 
144 		if (i > 0 && resv->r_start <= off) {
145 			mlog(ML_ERROR, "reservation %d has bad start off!\n",
146 			     i);
147 			goto bad;
148 		}
149 
150 		if (resv->r_len == 0) {
151 			mlog(ML_ERROR, "reservation %d has no length!\n",
152 			     i);
153 			goto bad;
154 		}
155 
156 		if (resv->r_start > ocfs2_resv_end(resv)) {
157 			mlog(ML_ERROR, "reservation %d has invalid range!\n",
158 			     i);
159 			goto bad;
160 		}
161 
162 		if (ocfs2_resv_end(resv) >= resmap->m_bitmap_len) {
163 			mlog(ML_ERROR, "reservation %d extends past bitmap!\n",
164 			     i);
165 			goto bad;
166 		}
167 
168 		if (ocfs2_validate_resmap_bits(resmap, i, resv))
169 			goto bad;
170 
171 		off = ocfs2_resv_end(resv);
172 		node = rb_next(node);
173 
174 		i++;
175 	}
176 	return;
177 
178 bad:
179 	ocfs2_dump_resv(resmap);
180 	BUG();
181 }
182 #else
183 static inline void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
184 {
185 
186 }
187 #endif
188 
189 void ocfs2_resv_init_once(struct ocfs2_alloc_reservation *resv)
190 {
191 	memset(resv, 0, sizeof(*resv));
192 	INIT_LIST_HEAD(&resv->r_lru);
193 }
194 
195 void ocfs2_resv_set_type(struct ocfs2_alloc_reservation *resv,
196 			 unsigned int flags)
197 {
198 	BUG_ON(flags & ~OCFS2_RESV_TYPES);
199 
200 	resv->r_flags |= flags;
201 }
202 
203 int ocfs2_resmap_init(struct ocfs2_super *osb,
204 		      struct ocfs2_reservation_map *resmap)
205 {
206 	memset(resmap, 0, sizeof(*resmap));
207 
208 	resmap->m_osb = osb;
209 	resmap->m_reservations = RB_ROOT;
210 	/* m_bitmap_len is initialized to zero by the above memset. */
211 	INIT_LIST_HEAD(&resmap->m_lru);
212 
213 	return 0;
214 }
215 
216 static void ocfs2_resv_mark_lru(struct ocfs2_reservation_map *resmap,
217 				struct ocfs2_alloc_reservation *resv)
218 {
219 	assert_spin_locked(&resv_lock);
220 
221 	if (!list_empty(&resv->r_lru))
222 		list_del_init(&resv->r_lru);
223 
224 	list_add_tail(&resv->r_lru, &resmap->m_lru);
225 }
226 
227 static void __ocfs2_resv_trunc(struct ocfs2_alloc_reservation *resv)
228 {
229 	resv->r_len = 0;
230 	resv->r_start = 0;
231 }
232 
233 static void ocfs2_resv_remove(struct ocfs2_reservation_map *resmap,
234 			      struct ocfs2_alloc_reservation *resv)
235 {
236 	if (resv->r_flags & OCFS2_RESV_FLAG_INUSE) {
237 		list_del_init(&resv->r_lru);
238 		rb_erase(&resv->r_node, &resmap->m_reservations);
239 		resv->r_flags &= ~OCFS2_RESV_FLAG_INUSE;
240 	}
241 }
242 
243 static void __ocfs2_resv_discard(struct ocfs2_reservation_map *resmap,
244 				 struct ocfs2_alloc_reservation *resv)
245 {
246 	assert_spin_locked(&resv_lock);
247 
248 	__ocfs2_resv_trunc(resv);
249 	/*
250 	 * last_len and last_start no longer make sense if
251 	 * we're changing the range of our allocations.
252 	 */
253 	resv->r_last_len = resv->r_last_start = 0;
254 
255 	ocfs2_resv_remove(resmap, resv);
256 }
257 
258 /* does nothing if 'resv' is null */
259 void ocfs2_resv_discard(struct ocfs2_reservation_map *resmap,
260 			struct ocfs2_alloc_reservation *resv)
261 {
262 	if (resv) {
263 		spin_lock(&resv_lock);
264 		__ocfs2_resv_discard(resmap, resv);
265 		spin_unlock(&resv_lock);
266 	}
267 }
268 
269 static void ocfs2_resmap_clear_all_resv(struct ocfs2_reservation_map *resmap)
270 {
271 	struct rb_node *node;
272 	struct ocfs2_alloc_reservation *resv;
273 
274 	assert_spin_locked(&resv_lock);
275 
276 	while ((node = rb_last(&resmap->m_reservations)) != NULL) {
277 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
278 
279 		__ocfs2_resv_discard(resmap, resv);
280 	}
281 }
282 
283 void ocfs2_resmap_restart(struct ocfs2_reservation_map *resmap,
284 			  unsigned int clen, char *disk_bitmap)
285 {
286 	if (ocfs2_resmap_disabled(resmap))
287 		return;
288 
289 	spin_lock(&resv_lock);
290 
291 	ocfs2_resmap_clear_all_resv(resmap);
292 	resmap->m_bitmap_len = clen;
293 	resmap->m_disk_bitmap = disk_bitmap;
294 
295 	spin_unlock(&resv_lock);
296 }
297 
298 void ocfs2_resmap_uninit(struct ocfs2_reservation_map *resmap)
299 {
300 	/* Does nothing for now. Keep this around for API symmetry */
301 }
302 
303 static void ocfs2_resv_insert(struct ocfs2_reservation_map *resmap,
304 			      struct ocfs2_alloc_reservation *new)
305 {
306 	struct rb_root *root = &resmap->m_reservations;
307 	struct rb_node *parent = NULL;
308 	struct rb_node **p = &root->rb_node;
309 	struct ocfs2_alloc_reservation *tmp;
310 
311 	assert_spin_locked(&resv_lock);
312 
313 	trace_ocfs2_resv_insert(new->r_start, new->r_len);
314 
315 	while (*p) {
316 		parent = *p;
317 
318 		tmp = rb_entry(parent, struct ocfs2_alloc_reservation, r_node);
319 
320 		if (new->r_start < tmp->r_start) {
321 			p = &(*p)->rb_left;
322 
323 			/*
324 			 * This is a good place to check for
325 			 * overlapping reservations.
326 			 */
327 			BUG_ON(ocfs2_resv_end(new) >= tmp->r_start);
328 		} else if (new->r_start > ocfs2_resv_end(tmp)) {
329 			p = &(*p)->rb_right;
330 		} else {
331 			/* This should never happen! */
332 			mlog(ML_ERROR, "Duplicate reservation window!\n");
333 			BUG();
334 		}
335 	}
336 
337 	rb_link_node(&new->r_node, parent, p);
338 	rb_insert_color(&new->r_node, root);
339 	new->r_flags |= OCFS2_RESV_FLAG_INUSE;
340 
341 	ocfs2_resv_mark_lru(resmap, new);
342 
343 	ocfs2_check_resmap(resmap);
344 }
345 
346 /**
347  * ocfs2_find_resv_lhs() - find the window which contains goal
348  * @resmap: reservation map to search
349  * @goal: which bit to search for
350  *
351  * If a window containing that goal is not found, we return the window
352  * which comes before goal. Returns NULL on empty rbtree or no window
353  * before goal.
354  */
355 static struct ocfs2_alloc_reservation *
356 ocfs2_find_resv_lhs(struct ocfs2_reservation_map *resmap, unsigned int goal)
357 {
358 	struct ocfs2_alloc_reservation *resv = NULL;
359 	struct ocfs2_alloc_reservation *prev_resv = NULL;
360 	struct rb_node *node = resmap->m_reservations.rb_node;
361 
362 	assert_spin_locked(&resv_lock);
363 
364 	if (!node)
365 		return NULL;
366 
367 	node = rb_first(&resmap->m_reservations);
368 	while (node) {
369 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
370 
371 		if (resv->r_start <= goal && ocfs2_resv_end(resv) >= goal)
372 			break;
373 
374 		/* Check if we overshot the reservation just before goal? */
375 		if (resv->r_start > goal) {
376 			resv = prev_resv;
377 			break;
378 		}
379 
380 		prev_resv = resv;
381 		node = rb_next(node);
382 	}
383 
384 	return resv;
385 }
386 
387 /*
388  * We are given a range within the bitmap, which corresponds to a gap
389  * inside the reservations tree (search_start, search_len). The range
390  * can be anything from the whole bitmap, to a gap between
391  * reservations.
392  *
393  * The start value of *rstart is insignificant.
394  *
395  * This function searches the bitmap range starting at search_start
396  * with length search_len for a set of contiguous free bits. We try
397  * to find up to 'wanted' bits, but can sometimes return less.
398  *
399  * Returns the length of allocation, 0 if no free bits are found.
400  *
401  * *cstart and *clen will also be populated with the result.
402  */
403 static int ocfs2_resmap_find_free_bits(struct ocfs2_reservation_map *resmap,
404 				       unsigned int wanted,
405 				       unsigned int search_start,
406 				       unsigned int search_len,
407 				       unsigned int *rstart,
408 				       unsigned int *rlen)
409 {
410 	void *bitmap = resmap->m_disk_bitmap;
411 	unsigned int best_start, best_len = 0;
412 	int offset, start, found;
413 
414 	trace_ocfs2_resmap_find_free_bits_begin(search_start, search_len,
415 						wanted, resmap->m_bitmap_len);
416 
417 	found = best_start = best_len = 0;
418 
419 	start = search_start;
420 	while ((offset = ocfs2_find_next_zero_bit(bitmap, resmap->m_bitmap_len,
421 						 start)) != -1) {
422 		/* Search reached end of the region */
423 		if (offset >= (search_start + search_len))
424 			break;
425 
426 		if (offset == start) {
427 			/* we found a zero */
428 			found++;
429 			/* move start to the next bit to test */
430 			start++;
431 		} else {
432 			/* got a zero after some ones */
433 			found = 1;
434 			start = offset + 1;
435 		}
436 		if (found > best_len) {
437 			best_len = found;
438 			best_start = start - found;
439 		}
440 
441 		if (found >= wanted)
442 			break;
443 	}
444 
445 	if (best_len == 0)
446 		return 0;
447 
448 	if (best_len >= wanted)
449 		best_len = wanted;
450 
451 	*rlen = best_len;
452 	*rstart = best_start;
453 
454 	trace_ocfs2_resmap_find_free_bits_end(best_start, best_len);
455 
456 	return *rlen;
457 }
458 
459 static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
460 				     struct ocfs2_alloc_reservation *resv,
461 				     unsigned int goal, unsigned int wanted)
462 {
463 	struct rb_root *root = &resmap->m_reservations;
464 	unsigned int gap_start, gap_end, gap_len;
465 	struct ocfs2_alloc_reservation *prev_resv, *next_resv;
466 	struct rb_node *prev, *next;
467 	unsigned int cstart, clen;
468 	unsigned int best_start = 0, best_len = 0;
469 
470 	/*
471 	 * Nasty cases to consider:
472 	 *
473 	 * - rbtree is empty
474 	 * - our window should be first in all reservations
475 	 * - our window should be last in all reservations
476 	 * - need to make sure we don't go past end of bitmap
477 	 */
478 	trace_ocfs2_resv_find_window_begin(resv->r_start, ocfs2_resv_end(resv),
479 					   goal, wanted, RB_EMPTY_ROOT(root));
480 
481 	assert_spin_locked(&resv_lock);
482 
483 	if (RB_EMPTY_ROOT(root)) {
484 		/*
485 		 * Easiest case - empty tree. We can just take
486 		 * whatever window of free bits we want.
487 		 */
488 		clen = ocfs2_resmap_find_free_bits(resmap, wanted, goal,
489 						   resmap->m_bitmap_len - goal,
490 						   &cstart, &clen);
491 
492 		/*
493 		 * This should never happen - the local alloc window
494 		 * will always have free bits when we're called.
495 		 */
496 		BUG_ON(goal == 0 && clen == 0);
497 
498 		if (clen == 0)
499 			return;
500 
501 		resv->r_start = cstart;
502 		resv->r_len = clen;
503 
504 		ocfs2_resv_insert(resmap, resv);
505 		return;
506 	}
507 
508 	prev_resv = ocfs2_find_resv_lhs(resmap, goal);
509 
510 	if (prev_resv == NULL) {
511 		/*
512 		 * A NULL here means that the search code couldn't
513 		 * find a window that starts before goal.
514 		 *
515 		 * However, we can take the first window after goal,
516 		 * which is also by definition, the leftmost window in
517 		 * the entire tree. If we can find free bits in the
518 		 * gap between goal and the LHS window, then the
519 		 * reservation can safely be placed there.
520 		 *
521 		 * Otherwise we fall back to a linear search, checking
522 		 * the gaps in between windows for a place to
523 		 * allocate.
524 		 */
525 
526 		next = rb_first(root);
527 		next_resv = rb_entry(next, struct ocfs2_alloc_reservation,
528 				     r_node);
529 
530 		/*
531 		 * The search should never return such a window. (see
532 		 * comment above
533 		 */
534 		if (next_resv->r_start <= goal) {
535 			mlog(ML_ERROR, "goal: %u next_resv: start %u len %u\n",
536 			     goal, next_resv->r_start, next_resv->r_len);
537 			ocfs2_dump_resv(resmap);
538 			BUG();
539 		}
540 
541 		clen = ocfs2_resmap_find_free_bits(resmap, wanted, goal,
542 						   next_resv->r_start - goal,
543 						   &cstart, &clen);
544 		if (clen) {
545 			best_len = clen;
546 			best_start = cstart;
547 			if (best_len == wanted)
548 				goto out_insert;
549 		}
550 
551 		prev_resv = next_resv;
552 		next_resv = NULL;
553 	}
554 
555 	trace_ocfs2_resv_find_window_prev(prev_resv->r_start,
556 					  ocfs2_resv_end(prev_resv));
557 
558 	prev = &prev_resv->r_node;
559 
560 	/* Now we do a linear search for a window, starting at 'prev_rsv' */
561 	while (1) {
562 		next = rb_next(prev);
563 		if (next) {
564 			next_resv = rb_entry(next,
565 					     struct ocfs2_alloc_reservation,
566 					     r_node);
567 
568 			gap_start = ocfs2_resv_end(prev_resv) + 1;
569 			gap_end = next_resv->r_start - 1;
570 			gap_len = gap_end - gap_start + 1;
571 		} else {
572 			/*
573 			 * We're at the rightmost edge of the
574 			 * tree. See if a reservation between this
575 			 * window and the end of the bitmap will work.
576 			 */
577 			gap_start = ocfs2_resv_end(prev_resv) + 1;
578 			gap_len = resmap->m_bitmap_len - gap_start;
579 			gap_end = resmap->m_bitmap_len - 1;
580 		}
581 
582 		trace_ocfs2_resv_find_window_next(next ? next_resv->r_start: -1,
583 					next ? ocfs2_resv_end(next_resv) : -1);
584 		/*
585 		 * No need to check this gap if we have already found
586 		 * a larger region of free bits.
587 		 */
588 		if (gap_len <= best_len)
589 			goto next_resv;
590 
591 		clen = ocfs2_resmap_find_free_bits(resmap, wanted, gap_start,
592 						   gap_len, &cstart, &clen);
593 		if (clen == wanted) {
594 			best_len = clen;
595 			best_start = cstart;
596 			goto out_insert;
597 		} else if (clen > best_len) {
598 			best_len = clen;
599 			best_start = cstart;
600 		}
601 
602 next_resv:
603 		if (!next)
604 			break;
605 
606 		prev = next;
607 		prev_resv = rb_entry(prev, struct ocfs2_alloc_reservation,
608 				     r_node);
609 	}
610 
611 out_insert:
612 	if (best_len) {
613 		resv->r_start = best_start;
614 		resv->r_len = best_len;
615 		ocfs2_resv_insert(resmap, resv);
616 	}
617 }
618 
619 static void ocfs2_cannibalize_resv(struct ocfs2_reservation_map *resmap,
620 				   struct ocfs2_alloc_reservation *resv,
621 				   unsigned int wanted)
622 {
623 	struct ocfs2_alloc_reservation *lru_resv;
624 	int tmpwindow = !!(resv->r_flags & OCFS2_RESV_FLAG_TMP);
625 	unsigned int min_bits;
626 
627 	if (!tmpwindow)
628 		min_bits = ocfs2_resv_window_bits(resmap, resv) >> 1;
629 	else
630 		min_bits = wanted; /* We at know the temp window will use all
631 				    * of these bits */
632 
633 	/*
634 	 * Take the first reservation off the LRU as our 'target'. We
635 	 * don't try to be smart about it. There might be a case for
636 	 * searching based on size but I don't have enough data to be
637 	 * sure. --Mark (3/16/2010)
638 	 */
639 	lru_resv = list_first_entry(&resmap->m_lru,
640 				    struct ocfs2_alloc_reservation, r_lru);
641 
642 	trace_ocfs2_cannibalize_resv_begin(lru_resv->r_start,
643 					   lru_resv->r_len,
644 					   ocfs2_resv_end(lru_resv));
645 
646 	/*
647 	 * Cannibalize (some or all) of the target reservation and
648 	 * feed it to the current window.
649 	 */
650 	if (lru_resv->r_len <= min_bits) {
651 		/*
652 		 * Discard completely if size is less than or equal to a
653 		 * reasonable threshold - 50% of window bits for non temporary
654 		 * windows.
655 		 */
656 		resv->r_start = lru_resv->r_start;
657 		resv->r_len = lru_resv->r_len;
658 
659 		__ocfs2_resv_discard(resmap, lru_resv);
660 	} else {
661 		unsigned int shrink;
662 		if (tmpwindow)
663 			shrink = min_bits;
664 		else
665 			shrink = lru_resv->r_len / 2;
666 
667 		lru_resv->r_len -= shrink;
668 
669 		resv->r_start = ocfs2_resv_end(lru_resv) + 1;
670 		resv->r_len = shrink;
671 	}
672 
673 	trace_ocfs2_cannibalize_resv_end(resv->r_start, ocfs2_resv_end(resv),
674 					 resv->r_len, resv->r_last_start,
675 					 resv->r_last_len);
676 
677 	ocfs2_resv_insert(resmap, resv);
678 }
679 
680 static void ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
681 				   struct ocfs2_alloc_reservation *resv,
682 				   unsigned int wanted)
683 {
684 	unsigned int goal = 0;
685 
686 	BUG_ON(!ocfs2_resv_empty(resv));
687 
688 	/*
689 	 * Begin by trying to get a window as close to the previous
690 	 * one as possible. Using the most recent allocation as a
691 	 * start goal makes sense.
692 	 */
693 	if (resv->r_last_len) {
694 		goal = resv->r_last_start + resv->r_last_len;
695 		if (goal >= resmap->m_bitmap_len)
696 			goal = 0;
697 	}
698 
699 	__ocfs2_resv_find_window(resmap, resv, goal, wanted);
700 
701 	/* Search from last alloc didn't work, try once more from beginning. */
702 	if (ocfs2_resv_empty(resv) && goal != 0)
703 		__ocfs2_resv_find_window(resmap, resv, 0, wanted);
704 
705 	if (ocfs2_resv_empty(resv)) {
706 		/*
707 		 * Still empty? Pull oldest one off the LRU, remove it from
708 		 * tree, put this one in it's place.
709 		 */
710 		ocfs2_cannibalize_resv(resmap, resv, wanted);
711 	}
712 
713 	BUG_ON(ocfs2_resv_empty(resv));
714 }
715 
716 int ocfs2_resmap_resv_bits(struct ocfs2_reservation_map *resmap,
717 			   struct ocfs2_alloc_reservation *resv,
718 			   int *cstart, int *clen)
719 {
720 	if (resv == NULL || ocfs2_resmap_disabled(resmap))
721 		return -ENOSPC;
722 
723 	spin_lock(&resv_lock);
724 
725 	if (ocfs2_resv_empty(resv)) {
726 		/*
727 		 * We don't want to over-allocate for temporary
728 		 * windows. Otherwise, we run the risk of fragmenting the
729 		 * allocation space.
730 		 */
731 		unsigned int wanted = ocfs2_resv_window_bits(resmap, resv);
732 
733 		if ((resv->r_flags & OCFS2_RESV_FLAG_TMP) || wanted < *clen)
734 			wanted = *clen;
735 
736 		/*
737 		 * Try to get a window here. If it works, we must fall
738 		 * through and test the bitmap . This avoids some
739 		 * ping-ponging of windows due to non-reserved space
740 		 * being allocation before we initialize a window for
741 		 * that inode.
742 		 */
743 		ocfs2_resv_find_window(resmap, resv, wanted);
744 		trace_ocfs2_resmap_resv_bits(resv->r_start, resv->r_len);
745 	}
746 
747 	BUG_ON(ocfs2_resv_empty(resv));
748 
749 	*cstart = resv->r_start;
750 	*clen = resv->r_len;
751 
752 	spin_unlock(&resv_lock);
753 	return 0;
754 }
755 
756 static void
757 	ocfs2_adjust_resv_from_alloc(struct ocfs2_reservation_map *resmap,
758 				     struct ocfs2_alloc_reservation *resv,
759 				     unsigned int start, unsigned int end)
760 {
761 	unsigned int rhs = 0;
762 	unsigned int old_end = ocfs2_resv_end(resv);
763 
764 	BUG_ON(start != resv->r_start || old_end < end);
765 
766 	/*
767 	 * Completely used? We can remove it then.
768 	 */
769 	if (old_end == end) {
770 		__ocfs2_resv_discard(resmap, resv);
771 		return;
772 	}
773 
774 	rhs = old_end - end;
775 
776 	/*
777 	 * This should have been trapped above.
778 	 */
779 	BUG_ON(rhs == 0);
780 
781 	resv->r_start = end + 1;
782 	resv->r_len = old_end - resv->r_start + 1;
783 }
784 
785 void ocfs2_resmap_claimed_bits(struct ocfs2_reservation_map *resmap,
786 			       struct ocfs2_alloc_reservation *resv,
787 			       u32 cstart, u32 clen)
788 {
789 	unsigned int cend = cstart + clen - 1;
790 
791 	if (resmap == NULL || ocfs2_resmap_disabled(resmap))
792 		return;
793 
794 	if (resv == NULL)
795 		return;
796 
797 	BUG_ON(cstart != resv->r_start);
798 
799 	spin_lock(&resv_lock);
800 
801 	trace_ocfs2_resmap_claimed_bits_begin(cstart, cend, clen, resv->r_start,
802 					      ocfs2_resv_end(resv), resv->r_len,
803 					      resv->r_last_start,
804 					      resv->r_last_len);
805 
806 	BUG_ON(cstart < resv->r_start);
807 	BUG_ON(cstart > ocfs2_resv_end(resv));
808 	BUG_ON(cend > ocfs2_resv_end(resv));
809 
810 	ocfs2_adjust_resv_from_alloc(resmap, resv, cstart, cend);
811 	resv->r_last_start = cstart;
812 	resv->r_last_len = clen;
813 
814 	/*
815 	 * May have been discarded above from
816 	 * ocfs2_adjust_resv_from_alloc().
817 	 */
818 	if (!ocfs2_resv_empty(resv))
819 		ocfs2_resv_mark_lru(resmap, resv);
820 
821 	trace_ocfs2_resmap_claimed_bits_end(resv->r_start, ocfs2_resv_end(resv),
822 					    resv->r_len, resv->r_last_start,
823 					    resv->r_last_len);
824 
825 	ocfs2_check_resmap(resmap);
826 
827 	spin_unlock(&resv_lock);
828 }
829