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
  42DEFINE_SPINLOCK(resv_lock);
  43
  44#define OCFS2_MIN_RESV_WINDOW_BITS      8
  45#define OCFS2_MAX_RESV_WINDOW_BITS      1024
  46
  47int ocfs2_dir_resv_allowed(struct ocfs2_super *osb)
  48{
  49        return (osb->osb_resv_level && osb->osb_dir_resv_level);
  50}
  51
  52static 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
  67static 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
  74static inline int ocfs2_resv_empty(struct ocfs2_alloc_reservation *resv)
  75{
  76        return !!(resv->r_len == 0);
  77}
  78
  79static 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
  86static 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
 123static 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
 144static 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
 189bad:
 190        ocfs2_dump_resv(resmap);
 191        BUG();
 192}
 193#else
 194static inline void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
 195{
 196
 197}
 198#endif
 199
 200void 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
 206void 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
 214int 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
 227static 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
 238static void __ocfs2_resv_trunc(struct ocfs2_alloc_reservation *resv)
 239{
 240        resv->r_len = 0;
 241        resv->r_start = 0;
 242}
 243
 244static 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
 254static 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 */
 270void 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
 280static 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
 294void 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
 309void ocfs2_resmap_uninit(struct ocfs2_reservation_map *resmap)
 310{
 311        /* Does nothing for now. Keep this around for API symmetry */
 312}
 313
 314static 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 */
 366static struct ocfs2_alloc_reservation *
 367ocfs2_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 */
 414static 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
 470static 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
 613next_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
 622out_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
 630static 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
 691static 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
 727int 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
 767static 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
 796void 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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