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Linux/fs/ocfs2/reservations.c

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  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 DEFINE_SPINLOCK(resv_lock);
 43 
 44 #define OCFS2_MIN_RESV_WINDOW_BITS      8
 45 #define OCFS2_MAX_RESV_WINDOW_BITS      1024
 46 
 47 int ocfs2_dir_resv_allowed(struct ocfs2_super *osb)
 48 {
 49         return (osb->osb_resv_level && osb->osb_dir_resv_level);
 50 }
 51 
 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 
 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 
 74 static inline int ocfs2_resv_empty(struct ocfs2_alloc_reservation *resv)
 75 {
 76         return !!(resv->r_len == 0);
 77 }
 78 
 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 
 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
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 
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
194 static inline void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
195 {
196 
197 }
198 #endif
199 
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 
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 
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 
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 
238 static void __ocfs2_resv_trunc(struct ocfs2_alloc_reservation *resv)
239 {
240         resv->r_len = 0;
241         resv->r_start = 0;
242 }
243 
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 
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 */
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 
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 
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 
309 void ocfs2_resmap_uninit(struct ocfs2_reservation_map *resmap)
310 {
311         /* Does nothing for now. Keep this around for API symmetry */
312 }
313 
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 *
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  */
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 
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 
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 
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 
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
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 
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 

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