1 /* -*- mode: c; c-basic-offset: 8; -*-
2  * vim: noexpandtab sw=8 ts=8 sts=0:
3  *
4  * reservations.c
5  *
6  * Allocation reservations implementation
7  *
8  * Some code borrowed from fs/ext3/balloc.c and is:
9  *
10  * Copyright (C) 1992, 1993, 1994, 1995
11  * Remy Card (card@masi.ibp.fr)
12  * Laboratoire MASI - Institut Blaise Pascal
13  * Universite Pierre et Marie Curie (Paris VI)
14  *
15  * The rest is copyright (C) 2010 Novell.  All rights reserved.
16  *
17  * This program is free software; you can redistribute it and/or
18  * modify it under the terms of the GNU General Public
19  * License version 2 as published by the Free Software Foundation.
20  *
21  * This program is distributed in the hope that it will be useful,
22  * but WITHOUT ANY WARRANTY; without even the implied warranty of
23  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
24  * General Public License for more details.
25  */
26 
27 #include <linux/fs.h>
28 #include <linux/types.h>
29 #include <linux/highmem.h>
30 #include <linux/bitops.h>
31 #include <linux/list.h>
32 
33 #include <cluster/masklog.h>
34 
35 #include "ocfs2.h"
36 #include "ocfs2_trace.h"
37 
38 #ifdef CONFIG_OCFS2_DEBUG_FS
39 #define OCFS2_CHECK_RESERVATIONS
40 #endif
41 
42 static DEFINE_SPINLOCK(resv_lock);
43 
44 #define	OCFS2_MIN_RESV_WINDOW_BITS	8
45 #define	OCFS2_MAX_RESV_WINDOW_BITS	1024
46 
ocfs2_dir_resv_allowed(struct ocfs2_super * osb)47 int ocfs2_dir_resv_allowed(struct ocfs2_super *osb)
48 {
49 	return (osb->osb_resv_level && osb->osb_dir_resv_level);
50 }
51 
ocfs2_resv_window_bits(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv)52 static unsigned int ocfs2_resv_window_bits(struct ocfs2_reservation_map *resmap,
53 					   struct ocfs2_alloc_reservation *resv)
54 {
55 	struct ocfs2_super *osb = resmap->m_osb;
56 	unsigned int bits;
57 
58 	if (!(resv->r_flags & OCFS2_RESV_FLAG_DIR)) {
59 		/* 8, 16, 32, 64, 128, 256, 512, 1024 */
60 		bits = 4 << osb->osb_resv_level;
61 	} else {
62 		bits = 4 << osb->osb_dir_resv_level;
63 	}
64 	return bits;
65 }
66 
ocfs2_resv_end(struct ocfs2_alloc_reservation * resv)67 static inline unsigned int ocfs2_resv_end(struct ocfs2_alloc_reservation *resv)
68 {
69 	if (resv->r_len)
70 		return resv->r_start + resv->r_len - 1;
71 	return resv->r_start;
72 }
73 
ocfs2_resv_empty(struct ocfs2_alloc_reservation * resv)74 static inline int ocfs2_resv_empty(struct ocfs2_alloc_reservation *resv)
75 {
76 	return !!(resv->r_len == 0);
77 }
78 
ocfs2_resmap_disabled(struct ocfs2_reservation_map * resmap)79 static inline int ocfs2_resmap_disabled(struct ocfs2_reservation_map *resmap)
80 {
81 	if (resmap->m_osb->osb_resv_level == 0)
82 		return 1;
83 	return 0;
84 }
85 
ocfs2_dump_resv(struct ocfs2_reservation_map * resmap)86 static void ocfs2_dump_resv(struct ocfs2_reservation_map *resmap)
87 {
88 	struct ocfs2_super *osb = resmap->m_osb;
89 	struct rb_node *node;
90 	struct ocfs2_alloc_reservation *resv;
91 	int i = 0;
92 
93 	mlog(ML_NOTICE, "Dumping resmap for device %s. Bitmap length: %u\n",
94 	     osb->dev_str, resmap->m_bitmap_len);
95 
96 	node = rb_first(&resmap->m_reservations);
97 	while (node) {
98 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
99 
100 		mlog(ML_NOTICE, "start: %u\tend: %u\tlen: %u\tlast_start: %u"
101 		     "\tlast_len: %u\n", resv->r_start,
102 		     ocfs2_resv_end(resv), resv->r_len, resv->r_last_start,
103 		     resv->r_last_len);
104 
105 		node = rb_next(node);
106 		i++;
107 	}
108 
109 	mlog(ML_NOTICE, "%d reservations found. LRU follows\n", i);
110 
111 	i = 0;
112 	list_for_each_entry(resv, &resmap->m_lru, r_lru) {
113 		mlog(ML_NOTICE, "LRU(%d) start: %u\tend: %u\tlen: %u\t"
114 		     "last_start: %u\tlast_len: %u\n", i, resv->r_start,
115 		     ocfs2_resv_end(resv), resv->r_len, resv->r_last_start,
116 		     resv->r_last_len);
117 
118 		i++;
119 	}
120 }
121 
122 #ifdef OCFS2_CHECK_RESERVATIONS
ocfs2_validate_resmap_bits(struct ocfs2_reservation_map * resmap,int i,struct ocfs2_alloc_reservation * resv)123 static int ocfs2_validate_resmap_bits(struct ocfs2_reservation_map *resmap,
124 				      int i,
125 				      struct ocfs2_alloc_reservation *resv)
126 {
127 	char *disk_bitmap = resmap->m_disk_bitmap;
128 	unsigned int start = resv->r_start;
129 	unsigned int end = ocfs2_resv_end(resv);
130 
131 	while (start <= end) {
132 		if (ocfs2_test_bit(start, disk_bitmap)) {
133 			mlog(ML_ERROR,
134 			     "reservation %d covers an allocated area "
135 			     "starting at bit %u!\n", i, start);
136 			return 1;
137 		}
138 
139 		start++;
140 	}
141 	return 0;
142 }
143 
ocfs2_check_resmap(struct ocfs2_reservation_map * resmap)144 static void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
145 {
146 	unsigned int off = 0;
147 	int i = 0;
148 	struct rb_node *node;
149 	struct ocfs2_alloc_reservation *resv;
150 
151 	node = rb_first(&resmap->m_reservations);
152 	while (node) {
153 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
154 
155 		if (i > 0 && resv->r_start <= off) {
156 			mlog(ML_ERROR, "reservation %d has bad start off!\n",
157 			     i);
158 			goto bad;
159 		}
160 
161 		if (resv->r_len == 0) {
162 			mlog(ML_ERROR, "reservation %d has no length!\n",
163 			     i);
164 			goto bad;
165 		}
166 
167 		if (resv->r_start > ocfs2_resv_end(resv)) {
168 			mlog(ML_ERROR, "reservation %d has invalid range!\n",
169 			     i);
170 			goto bad;
171 		}
172 
173 		if (ocfs2_resv_end(resv) >= resmap->m_bitmap_len) {
174 			mlog(ML_ERROR, "reservation %d extends past bitmap!\n",
175 			     i);
176 			goto bad;
177 		}
178 
179 		if (ocfs2_validate_resmap_bits(resmap, i, resv))
180 			goto bad;
181 
182 		off = ocfs2_resv_end(resv);
183 		node = rb_next(node);
184 
185 		i++;
186 	}
187 	return;
188 
189 bad:
190 	ocfs2_dump_resv(resmap);
191 	BUG();
192 }
193 #else
ocfs2_check_resmap(struct ocfs2_reservation_map * resmap)194 static inline void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
195 {
196 
197 }
198 #endif
199 
ocfs2_resv_init_once(struct ocfs2_alloc_reservation * resv)200 void ocfs2_resv_init_once(struct ocfs2_alloc_reservation *resv)
201 {
202 	memset(resv, 0, sizeof(*resv));
203 	INIT_LIST_HEAD(&resv->r_lru);
204 }
205 
ocfs2_resv_set_type(struct ocfs2_alloc_reservation * resv,unsigned int flags)206 void ocfs2_resv_set_type(struct ocfs2_alloc_reservation *resv,
207 			 unsigned int flags)
208 {
209 	BUG_ON(flags & ~OCFS2_RESV_TYPES);
210 
211 	resv->r_flags |= flags;
212 }
213 
ocfs2_resmap_init(struct ocfs2_super * osb,struct ocfs2_reservation_map * resmap)214 int ocfs2_resmap_init(struct ocfs2_super *osb,
215 		      struct ocfs2_reservation_map *resmap)
216 {
217 	memset(resmap, 0, sizeof(*resmap));
218 
219 	resmap->m_osb = osb;
220 	resmap->m_reservations = RB_ROOT;
221 	/* m_bitmap_len is initialized to zero by the above memset. */
222 	INIT_LIST_HEAD(&resmap->m_lru);
223 
224 	return 0;
225 }
226 
ocfs2_resv_mark_lru(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv)227 static void ocfs2_resv_mark_lru(struct ocfs2_reservation_map *resmap,
228 				struct ocfs2_alloc_reservation *resv)
229 {
230 	assert_spin_locked(&resv_lock);
231 
232 	if (!list_empty(&resv->r_lru))
233 		list_del_init(&resv->r_lru);
234 
235 	list_add_tail(&resv->r_lru, &resmap->m_lru);
236 }
237 
__ocfs2_resv_trunc(struct ocfs2_alloc_reservation * resv)238 static void __ocfs2_resv_trunc(struct ocfs2_alloc_reservation *resv)
239 {
240 	resv->r_len = 0;
241 	resv->r_start = 0;
242 }
243 
ocfs2_resv_remove(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv)244 static void ocfs2_resv_remove(struct ocfs2_reservation_map *resmap,
245 			      struct ocfs2_alloc_reservation *resv)
246 {
247 	if (resv->r_flags & OCFS2_RESV_FLAG_INUSE) {
248 		list_del_init(&resv->r_lru);
249 		rb_erase(&resv->r_node, &resmap->m_reservations);
250 		resv->r_flags &= ~OCFS2_RESV_FLAG_INUSE;
251 	}
252 }
253 
__ocfs2_resv_discard(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv)254 static void __ocfs2_resv_discard(struct ocfs2_reservation_map *resmap,
255 				 struct ocfs2_alloc_reservation *resv)
256 {
257 	assert_spin_locked(&resv_lock);
258 
259 	__ocfs2_resv_trunc(resv);
260 	/*
261 	 * last_len and last_start no longer make sense if
262 	 * we're changing the range of our allocations.
263 	 */
264 	resv->r_last_len = resv->r_last_start = 0;
265 
266 	ocfs2_resv_remove(resmap, resv);
267 }
268 
269 /* does nothing if 'resv' is null */
ocfs2_resv_discard(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv)270 void ocfs2_resv_discard(struct ocfs2_reservation_map *resmap,
271 			struct ocfs2_alloc_reservation *resv)
272 {
273 	if (resv) {
274 		spin_lock(&resv_lock);
275 		__ocfs2_resv_discard(resmap, resv);
276 		spin_unlock(&resv_lock);
277 	}
278 }
279 
ocfs2_resmap_clear_all_resv(struct ocfs2_reservation_map * resmap)280 static void ocfs2_resmap_clear_all_resv(struct ocfs2_reservation_map *resmap)
281 {
282 	struct rb_node *node;
283 	struct ocfs2_alloc_reservation *resv;
284 
285 	assert_spin_locked(&resv_lock);
286 
287 	while ((node = rb_last(&resmap->m_reservations)) != NULL) {
288 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
289 
290 		__ocfs2_resv_discard(resmap, resv);
291 	}
292 }
293 
ocfs2_resmap_restart(struct ocfs2_reservation_map * resmap,unsigned int clen,char * disk_bitmap)294 void ocfs2_resmap_restart(struct ocfs2_reservation_map *resmap,
295 			  unsigned int clen, char *disk_bitmap)
296 {
297 	if (ocfs2_resmap_disabled(resmap))
298 		return;
299 
300 	spin_lock(&resv_lock);
301 
302 	ocfs2_resmap_clear_all_resv(resmap);
303 	resmap->m_bitmap_len = clen;
304 	resmap->m_disk_bitmap = disk_bitmap;
305 
306 	spin_unlock(&resv_lock);
307 }
308 
ocfs2_resmap_uninit(struct ocfs2_reservation_map * resmap)309 void ocfs2_resmap_uninit(struct ocfs2_reservation_map *resmap)
310 {
311 	/* Does nothing for now. Keep this around for API symmetry */
312 }
313 
ocfs2_resv_insert(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * new)314 static void ocfs2_resv_insert(struct ocfs2_reservation_map *resmap,
315 			      struct ocfs2_alloc_reservation *new)
316 {
317 	struct rb_root *root = &resmap->m_reservations;
318 	struct rb_node *parent = NULL;
319 	struct rb_node **p = &root->rb_node;
320 	struct ocfs2_alloc_reservation *tmp;
321 
322 	assert_spin_locked(&resv_lock);
323 
324 	trace_ocfs2_resv_insert(new->r_start, new->r_len);
325 
326 	while (*p) {
327 		parent = *p;
328 
329 		tmp = rb_entry(parent, struct ocfs2_alloc_reservation, r_node);
330 
331 		if (new->r_start < tmp->r_start) {
332 			p = &(*p)->rb_left;
333 
334 			/*
335 			 * This is a good place to check for
336 			 * overlapping reservations.
337 			 */
338 			BUG_ON(ocfs2_resv_end(new) >= tmp->r_start);
339 		} else if (new->r_start > ocfs2_resv_end(tmp)) {
340 			p = &(*p)->rb_right;
341 		} else {
342 			/* This should never happen! */
343 			mlog(ML_ERROR, "Duplicate reservation window!\n");
344 			BUG();
345 		}
346 	}
347 
348 	rb_link_node(&new->r_node, parent, p);
349 	rb_insert_color(&new->r_node, root);
350 	new->r_flags |= OCFS2_RESV_FLAG_INUSE;
351 
352 	ocfs2_resv_mark_lru(resmap, new);
353 
354 	ocfs2_check_resmap(resmap);
355 }
356 
357 /**
358  * ocfs2_find_resv_lhs() - find the window which contains goal
359  * @resmap: reservation map to search
360  * @goal: which bit to search for
361  *
362  * If a window containing that goal is not found, we return the window
363  * which comes before goal. Returns NULL on empty rbtree or no window
364  * before goal.
365  */
366 static struct ocfs2_alloc_reservation *
ocfs2_find_resv_lhs(struct ocfs2_reservation_map * resmap,unsigned int goal)367 ocfs2_find_resv_lhs(struct ocfs2_reservation_map *resmap, unsigned int goal)
368 {
369 	struct ocfs2_alloc_reservation *resv = NULL;
370 	struct ocfs2_alloc_reservation *prev_resv = NULL;
371 	struct rb_node *node = resmap->m_reservations.rb_node;
372 
373 	assert_spin_locked(&resv_lock);
374 
375 	if (!node)
376 		return NULL;
377 
378 	node = rb_first(&resmap->m_reservations);
379 	while (node) {
380 		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);
381 
382 		if (resv->r_start <= goal && ocfs2_resv_end(resv) >= goal)
383 			break;
384 
385 		/* Check if we overshot the reservation just before goal? */
386 		if (resv->r_start > goal) {
387 			resv = prev_resv;
388 			break;
389 		}
390 
391 		prev_resv = resv;
392 		node = rb_next(node);
393 	}
394 
395 	return resv;
396 }
397 
398 /*
399  * We are given a range within the bitmap, which corresponds to a gap
400  * inside the reservations tree (search_start, search_len). The range
401  * can be anything from the whole bitmap, to a gap between
402  * reservations.
403  *
404  * The start value of *rstart is insignificant.
405  *
406  * This function searches the bitmap range starting at search_start
407  * with length search_len for a set of contiguous free bits. We try
408  * to find up to 'wanted' bits, but can sometimes return less.
409  *
410  * Returns the length of allocation, 0 if no free bits are found.
411  *
412  * *cstart and *clen will also be populated with the result.
413  */
ocfs2_resmap_find_free_bits(struct ocfs2_reservation_map * resmap,unsigned int wanted,unsigned int search_start,unsigned int search_len,unsigned int * rstart,unsigned int * rlen)414 static int ocfs2_resmap_find_free_bits(struct ocfs2_reservation_map *resmap,
415 				       unsigned int wanted,
416 				       unsigned int search_start,
417 				       unsigned int search_len,
418 				       unsigned int *rstart,
419 				       unsigned int *rlen)
420 {
421 	void *bitmap = resmap->m_disk_bitmap;
422 	unsigned int best_start, best_len = 0;
423 	int offset, start, found;
424 
425 	trace_ocfs2_resmap_find_free_bits_begin(search_start, search_len,
426 						wanted, resmap->m_bitmap_len);
427 
428 	found = best_start = best_len = 0;
429 
430 	start = search_start;
431 	while ((offset = ocfs2_find_next_zero_bit(bitmap, resmap->m_bitmap_len,
432 						 start)) != -1) {
433 		/* Search reached end of the region */
434 		if (offset >= (search_start + search_len))
435 			break;
436 
437 		if (offset == start) {
438 			/* we found a zero */
439 			found++;
440 			/* move start to the next bit to test */
441 			start++;
442 		} else {
443 			/* got a zero after some ones */
444 			found = 1;
445 			start = offset + 1;
446 		}
447 		if (found > best_len) {
448 			best_len = found;
449 			best_start = start - found;
450 		}
451 
452 		if (found >= wanted)
453 			break;
454 	}
455 
456 	if (best_len == 0)
457 		return 0;
458 
459 	if (best_len >= wanted)
460 		best_len = wanted;
461 
462 	*rlen = best_len;
463 	*rstart = best_start;
464 
465 	trace_ocfs2_resmap_find_free_bits_end(best_start, best_len);
466 
467 	return *rlen;
468 }
469 
__ocfs2_resv_find_window(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv,unsigned int goal,unsigned int wanted)470 static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
471 				     struct ocfs2_alloc_reservation *resv,
472 				     unsigned int goal, unsigned int wanted)
473 {
474 	struct rb_root *root = &resmap->m_reservations;
475 	unsigned int gap_start, gap_end, gap_len;
476 	struct ocfs2_alloc_reservation *prev_resv, *next_resv;
477 	struct rb_node *prev, *next;
478 	unsigned int cstart, clen;
479 	unsigned int best_start = 0, best_len = 0;
480 
481 	/*
482 	 * Nasty cases to consider:
483 	 *
484 	 * - rbtree is empty
485 	 * - our window should be first in all reservations
486 	 * - our window should be last in all reservations
487 	 * - need to make sure we don't go past end of bitmap
488 	 */
489 	trace_ocfs2_resv_find_window_begin(resv->r_start, ocfs2_resv_end(resv),
490 					   goal, wanted, RB_EMPTY_ROOT(root));
491 
492 	assert_spin_locked(&resv_lock);
493 
494 	if (RB_EMPTY_ROOT(root)) {
495 		/*
496 		 * Easiest case - empty tree. We can just take
497 		 * whatever window of free bits we want.
498 		 */
499 		clen = ocfs2_resmap_find_free_bits(resmap, wanted, goal,
500 						   resmap->m_bitmap_len - goal,
501 						   &cstart, &clen);
502 
503 		/*
504 		 * This should never happen - the local alloc window
505 		 * will always have free bits when we're called.
506 		 */
507 		BUG_ON(goal == 0 && clen == 0);
508 
509 		if (clen == 0)
510 			return;
511 
512 		resv->r_start = cstart;
513 		resv->r_len = clen;
514 
515 		ocfs2_resv_insert(resmap, resv);
516 		return;
517 	}
518 
519 	prev_resv = ocfs2_find_resv_lhs(resmap, goal);
520 
521 	if (prev_resv == NULL) {
522 		/*
523 		 * A NULL here means that the search code couldn't
524 		 * find a window that starts before goal.
525 		 *
526 		 * However, we can take the first window after goal,
527 		 * which is also by definition, the leftmost window in
528 		 * the entire tree. If we can find free bits in the
529 		 * gap between goal and the LHS window, then the
530 		 * reservation can safely be placed there.
531 		 *
532 		 * Otherwise we fall back to a linear search, checking
533 		 * the gaps in between windows for a place to
534 		 * allocate.
535 		 */
536 
537 		next = rb_first(root);
538 		next_resv = rb_entry(next, struct ocfs2_alloc_reservation,
539 				     r_node);
540 
541 		/*
542 		 * The search should never return such a window. (see
543 		 * comment above
544 		 */
545 		if (next_resv->r_start <= goal) {
546 			mlog(ML_ERROR, "goal: %u next_resv: start %u len %u\n",
547 			     goal, next_resv->r_start, next_resv->r_len);
548 			ocfs2_dump_resv(resmap);
549 			BUG();
550 		}
551 
552 		clen = ocfs2_resmap_find_free_bits(resmap, wanted, goal,
553 						   next_resv->r_start - goal,
554 						   &cstart, &clen);
555 		if (clen) {
556 			best_len = clen;
557 			best_start = cstart;
558 			if (best_len == wanted)
559 				goto out_insert;
560 		}
561 
562 		prev_resv = next_resv;
563 		next_resv = NULL;
564 	}
565 
566 	trace_ocfs2_resv_find_window_prev(prev_resv->r_start,
567 					  ocfs2_resv_end(prev_resv));
568 
569 	prev = &prev_resv->r_node;
570 
571 	/* Now we do a linear search for a window, starting at 'prev_rsv' */
572 	while (1) {
573 		next = rb_next(prev);
574 		if (next) {
575 			next_resv = rb_entry(next,
576 					     struct ocfs2_alloc_reservation,
577 					     r_node);
578 
579 			gap_start = ocfs2_resv_end(prev_resv) + 1;
580 			gap_end = next_resv->r_start - 1;
581 			gap_len = gap_end - gap_start + 1;
582 		} else {
583 			/*
584 			 * We're at the rightmost edge of the
585 			 * tree. See if a reservation between this
586 			 * window and the end of the bitmap will work.
587 			 */
588 			gap_start = ocfs2_resv_end(prev_resv) + 1;
589 			gap_len = resmap->m_bitmap_len - gap_start;
590 			gap_end = resmap->m_bitmap_len - 1;
591 		}
592 
593 		trace_ocfs2_resv_find_window_next(next ? next_resv->r_start: -1,
594 					next ? ocfs2_resv_end(next_resv) : -1);
595 		/*
596 		 * No need to check this gap if we have already found
597 		 * a larger region of free bits.
598 		 */
599 		if (gap_len <= best_len)
600 			goto next_resv;
601 
602 		clen = ocfs2_resmap_find_free_bits(resmap, wanted, gap_start,
603 						   gap_len, &cstart, &clen);
604 		if (clen == wanted) {
605 			best_len = clen;
606 			best_start = cstart;
607 			goto out_insert;
608 		} else if (clen > best_len) {
609 			best_len = clen;
610 			best_start = cstart;
611 		}
612 
613 next_resv:
614 		if (!next)
615 			break;
616 
617 		prev = next;
618 		prev_resv = rb_entry(prev, struct ocfs2_alloc_reservation,
619 				     r_node);
620 	}
621 
622 out_insert:
623 	if (best_len) {
624 		resv->r_start = best_start;
625 		resv->r_len = best_len;
626 		ocfs2_resv_insert(resmap, resv);
627 	}
628 }
629 
ocfs2_cannibalize_resv(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv,unsigned int wanted)630 static void ocfs2_cannibalize_resv(struct ocfs2_reservation_map *resmap,
631 				   struct ocfs2_alloc_reservation *resv,
632 				   unsigned int wanted)
633 {
634 	struct ocfs2_alloc_reservation *lru_resv;
635 	int tmpwindow = !!(resv->r_flags & OCFS2_RESV_FLAG_TMP);
636 	unsigned int min_bits;
637 
638 	if (!tmpwindow)
639 		min_bits = ocfs2_resv_window_bits(resmap, resv) >> 1;
640 	else
641 		min_bits = wanted; /* We at know the temp window will use all
642 				    * of these bits */
643 
644 	/*
645 	 * Take the first reservation off the LRU as our 'target'. We
646 	 * don't try to be smart about it. There might be a case for
647 	 * searching based on size but I don't have enough data to be
648 	 * sure. --Mark (3/16/2010)
649 	 */
650 	lru_resv = list_first_entry(&resmap->m_lru,
651 				    struct ocfs2_alloc_reservation, r_lru);
652 
653 	trace_ocfs2_cannibalize_resv_begin(lru_resv->r_start,
654 					   lru_resv->r_len,
655 					   ocfs2_resv_end(lru_resv));
656 
657 	/*
658 	 * Cannibalize (some or all) of the target reservation and
659 	 * feed it to the current window.
660 	 */
661 	if (lru_resv->r_len <= min_bits) {
662 		/*
663 		 * Discard completely if size is less than or equal to a
664 		 * reasonable threshold - 50% of window bits for non temporary
665 		 * windows.
666 		 */
667 		resv->r_start = lru_resv->r_start;
668 		resv->r_len = lru_resv->r_len;
669 
670 		__ocfs2_resv_discard(resmap, lru_resv);
671 	} else {
672 		unsigned int shrink;
673 		if (tmpwindow)
674 			shrink = min_bits;
675 		else
676 			shrink = lru_resv->r_len / 2;
677 
678 		lru_resv->r_len -= shrink;
679 
680 		resv->r_start = ocfs2_resv_end(lru_resv) + 1;
681 		resv->r_len = shrink;
682 	}
683 
684 	trace_ocfs2_cannibalize_resv_end(resv->r_start, ocfs2_resv_end(resv),
685 					 resv->r_len, resv->r_last_start,
686 					 resv->r_last_len);
687 
688 	ocfs2_resv_insert(resmap, resv);
689 }
690 
ocfs2_resv_find_window(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv,unsigned int wanted)691 static void ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
692 				   struct ocfs2_alloc_reservation *resv,
693 				   unsigned int wanted)
694 {
695 	unsigned int goal = 0;
696 
697 	BUG_ON(!ocfs2_resv_empty(resv));
698 
699 	/*
700 	 * Begin by trying to get a window as close to the previous
701 	 * one as possible. Using the most recent allocation as a
702 	 * start goal makes sense.
703 	 */
704 	if (resv->r_last_len) {
705 		goal = resv->r_last_start + resv->r_last_len;
706 		if (goal >= resmap->m_bitmap_len)
707 			goal = 0;
708 	}
709 
710 	__ocfs2_resv_find_window(resmap, resv, goal, wanted);
711 
712 	/* Search from last alloc didn't work, try once more from beginning. */
713 	if (ocfs2_resv_empty(resv) && goal != 0)
714 		__ocfs2_resv_find_window(resmap, resv, 0, wanted);
715 
716 	if (ocfs2_resv_empty(resv)) {
717 		/*
718 		 * Still empty? Pull oldest one off the LRU, remove it from
719 		 * tree, put this one in it's place.
720 		 */
721 		ocfs2_cannibalize_resv(resmap, resv, wanted);
722 	}
723 
724 	BUG_ON(ocfs2_resv_empty(resv));
725 }
726 
ocfs2_resmap_resv_bits(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv,int * cstart,int * clen)727 int ocfs2_resmap_resv_bits(struct ocfs2_reservation_map *resmap,
728 			   struct ocfs2_alloc_reservation *resv,
729 			   int *cstart, int *clen)
730 {
731 	if (resv == NULL || ocfs2_resmap_disabled(resmap))
732 		return -ENOSPC;
733 
734 	spin_lock(&resv_lock);
735 
736 	if (ocfs2_resv_empty(resv)) {
737 		/*
738 		 * We don't want to over-allocate for temporary
739 		 * windows. Otherwise, we run the risk of fragmenting the
740 		 * allocation space.
741 		 */
742 		unsigned int wanted = ocfs2_resv_window_bits(resmap, resv);
743 
744 		if ((resv->r_flags & OCFS2_RESV_FLAG_TMP) || wanted < *clen)
745 			wanted = *clen;
746 
747 		/*
748 		 * Try to get a window here. If it works, we must fall
749 		 * through and test the bitmap . This avoids some
750 		 * ping-ponging of windows due to non-reserved space
751 		 * being allocation before we initialize a window for
752 		 * that inode.
753 		 */
754 		ocfs2_resv_find_window(resmap, resv, wanted);
755 		trace_ocfs2_resmap_resv_bits(resv->r_start, resv->r_len);
756 	}
757 
758 	BUG_ON(ocfs2_resv_empty(resv));
759 
760 	*cstart = resv->r_start;
761 	*clen = resv->r_len;
762 
763 	spin_unlock(&resv_lock);
764 	return 0;
765 }
766 
767 static void
ocfs2_adjust_resv_from_alloc(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv,unsigned int start,unsigned int end)768 	ocfs2_adjust_resv_from_alloc(struct ocfs2_reservation_map *resmap,
769 				     struct ocfs2_alloc_reservation *resv,
770 				     unsigned int start, unsigned int end)
771 {
772 	unsigned int rhs = 0;
773 	unsigned int old_end = ocfs2_resv_end(resv);
774 
775 	BUG_ON(start != resv->r_start || old_end < end);
776 
777 	/*
778 	 * Completely used? We can remove it then.
779 	 */
780 	if (old_end == end) {
781 		__ocfs2_resv_discard(resmap, resv);
782 		return;
783 	}
784 
785 	rhs = old_end - end;
786 
787 	/*
788 	 * This should have been trapped above.
789 	 */
790 	BUG_ON(rhs == 0);
791 
792 	resv->r_start = end + 1;
793 	resv->r_len = old_end - resv->r_start + 1;
794 }
795 
ocfs2_resmap_claimed_bits(struct ocfs2_reservation_map * resmap,struct ocfs2_alloc_reservation * resv,u32 cstart,u32 clen)796 void ocfs2_resmap_claimed_bits(struct ocfs2_reservation_map *resmap,
797 			       struct ocfs2_alloc_reservation *resv,
798 			       u32 cstart, u32 clen)
799 {
800 	unsigned int cend = cstart + clen - 1;
801 
802 	if (resmap == NULL || ocfs2_resmap_disabled(resmap))
803 		return;
804 
805 	if (resv == NULL)
806 		return;
807 
808 	BUG_ON(cstart != resv->r_start);
809 
810 	spin_lock(&resv_lock);
811 
812 	trace_ocfs2_resmap_claimed_bits_begin(cstart, cend, clen, resv->r_start,
813 					      ocfs2_resv_end(resv), resv->r_len,
814 					      resv->r_last_start,
815 					      resv->r_last_len);
816 
817 	BUG_ON(cstart < resv->r_start);
818 	BUG_ON(cstart > ocfs2_resv_end(resv));
819 	BUG_ON(cend > ocfs2_resv_end(resv));
820 
821 	ocfs2_adjust_resv_from_alloc(resmap, resv, cstart, cend);
822 	resv->r_last_start = cstart;
823 	resv->r_last_len = clen;
824 
825 	/*
826 	 * May have been discarded above from
827 	 * ocfs2_adjust_resv_from_alloc().
828 	 */
829 	if (!ocfs2_resv_empty(resv))
830 		ocfs2_resv_mark_lru(resmap, resv);
831 
832 	trace_ocfs2_resmap_claimed_bits_end(resv->r_start, ocfs2_resv_end(resv),
833 					    resv->r_len, resv->r_last_start,
834 					    resv->r_last_len);
835 
836 	ocfs2_check_resmap(resmap);
837 
838 	spin_unlock(&resv_lock);
839 }
840