linux/fs/ext2/balloc.c
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   1/*
   2 *  linux/fs/ext2/balloc.c
   3 *
   4 * Copyright (C) 1992, 1993, 1994, 1995
   5 * Remy Card (card@masi.ibp.fr)
   6 * Laboratoire MASI - Institut Blaise Pascal
   7 * Universite Pierre et Marie Curie (Paris VI)
   8 *
   9 *  Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
  10 *  Big-endian to little-endian byte-swapping/bitmaps by
  11 *        David S. Miller (davem@caip.rutgers.edu), 1995
  12 */
  13
  14#include "ext2.h"
  15#include <linux/quotaops.h>
  16#include <linux/slab.h>
  17#include <linux/sched.h>
  18#include <linux/buffer_head.h>
  19#include <linux/capability.h>
  20
  21/*
  22 * balloc.c contains the blocks allocation and deallocation routines
  23 */
  24
  25/*
  26 * The free blocks are managed by bitmaps.  A file system contains several
  27 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
  28 * block for inodes, N blocks for the inode table and data blocks.
  29 *
  30 * The file system contains group descriptors which are located after the
  31 * super block.  Each descriptor contains the number of the bitmap block and
  32 * the free blocks count in the block.  The descriptors are loaded in memory
  33 * when a file system is mounted (see ext2_fill_super).
  34 */
  35
  36
  37#define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
  38
  39struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
  40                                             unsigned int block_group,
  41                                             struct buffer_head ** bh)
  42{
  43        unsigned long group_desc;
  44        unsigned long offset;
  45        struct ext2_group_desc * desc;
  46        struct ext2_sb_info *sbi = EXT2_SB(sb);
  47
  48        if (block_group >= sbi->s_groups_count) {
  49                ext2_error (sb, "ext2_get_group_desc",
  50                            "block_group >= groups_count - "
  51                            "block_group = %d, groups_count = %lu",
  52                            block_group, sbi->s_groups_count);
  53
  54                return NULL;
  55        }
  56
  57        group_desc = block_group >> EXT2_DESC_PER_BLOCK_BITS(sb);
  58        offset = block_group & (EXT2_DESC_PER_BLOCK(sb) - 1);
  59        if (!sbi->s_group_desc[group_desc]) {
  60                ext2_error (sb, "ext2_get_group_desc",
  61                            "Group descriptor not loaded - "
  62                            "block_group = %d, group_desc = %lu, desc = %lu",
  63                             block_group, group_desc, offset);
  64                return NULL;
  65        }
  66
  67        desc = (struct ext2_group_desc *) sbi->s_group_desc[group_desc]->b_data;
  68        if (bh)
  69                *bh = sbi->s_group_desc[group_desc];
  70        return desc + offset;
  71}
  72
  73static int ext2_valid_block_bitmap(struct super_block *sb,
  74                                        struct ext2_group_desc *desc,
  75                                        unsigned int block_group,
  76                                        struct buffer_head *bh)
  77{
  78        ext2_grpblk_t offset;
  79        ext2_grpblk_t next_zero_bit;
  80        ext2_fsblk_t bitmap_blk;
  81        ext2_fsblk_t group_first_block;
  82
  83        group_first_block = ext2_group_first_block_no(sb, block_group);
  84
  85        /* check whether block bitmap block number is set */
  86        bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
  87        offset = bitmap_blk - group_first_block;
  88        if (!ext2_test_bit(offset, bh->b_data))
  89                /* bad block bitmap */
  90                goto err_out;
  91
  92        /* check whether the inode bitmap block number is set */
  93        bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
  94        offset = bitmap_blk - group_first_block;
  95        if (!ext2_test_bit(offset, bh->b_data))
  96                /* bad block bitmap */
  97                goto err_out;
  98
  99        /* check whether the inode table block number is set */
 100        bitmap_blk = le32_to_cpu(desc->bg_inode_table);
 101        offset = bitmap_blk - group_first_block;
 102        next_zero_bit = ext2_find_next_zero_bit(bh->b_data,
 103                                offset + EXT2_SB(sb)->s_itb_per_group,
 104                                offset);
 105        if (next_zero_bit >= offset + EXT2_SB(sb)->s_itb_per_group)
 106                /* good bitmap for inode tables */
 107                return 1;
 108
 109err_out:
 110        ext2_error(sb, __func__,
 111                        "Invalid block bitmap - "
 112                        "block_group = %d, block = %lu",
 113                        block_group, bitmap_blk);
 114        return 0;
 115}
 116
 117/*
 118 * Read the bitmap for a given block_group,and validate the
 119 * bits for block/inode/inode tables are set in the bitmaps
 120 *
 121 * Return buffer_head on success or NULL in case of failure.
 122 */
 123static struct buffer_head *
 124read_block_bitmap(struct super_block *sb, unsigned int block_group)
 125{
 126        struct ext2_group_desc * desc;
 127        struct buffer_head * bh = NULL;
 128        ext2_fsblk_t bitmap_blk;
 129
 130        desc = ext2_get_group_desc(sb, block_group, NULL);
 131        if (!desc)
 132                return NULL;
 133        bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
 134        bh = sb_getblk(sb, bitmap_blk);
 135        if (unlikely(!bh)) {
 136                ext2_error(sb, __func__,
 137                            "Cannot read block bitmap - "
 138                            "block_group = %d, block_bitmap = %u",
 139                            block_group, le32_to_cpu(desc->bg_block_bitmap));
 140                return NULL;
 141        }
 142        if (likely(bh_uptodate_or_lock(bh)))
 143                return bh;
 144
 145        if (bh_submit_read(bh) < 0) {
 146                brelse(bh);
 147                ext2_error(sb, __func__,
 148                            "Cannot read block bitmap - "
 149                            "block_group = %d, block_bitmap = %u",
 150                            block_group, le32_to_cpu(desc->bg_block_bitmap));
 151                return NULL;
 152        }
 153
 154        ext2_valid_block_bitmap(sb, desc, block_group, bh);
 155        /*
 156         * file system mounted not to panic on error, continue with corrupt
 157         * bitmap
 158         */
 159        return bh;
 160}
 161
 162static void release_blocks(struct super_block *sb, int count)
 163{
 164        if (count) {
 165                struct ext2_sb_info *sbi = EXT2_SB(sb);
 166
 167                percpu_counter_add(&sbi->s_freeblocks_counter, count);
 168        }
 169}
 170
 171static void group_adjust_blocks(struct super_block *sb, int group_no,
 172        struct ext2_group_desc *desc, struct buffer_head *bh, int count)
 173{
 174        if (count) {
 175                struct ext2_sb_info *sbi = EXT2_SB(sb);
 176                unsigned free_blocks;
 177
 178                spin_lock(sb_bgl_lock(sbi, group_no));
 179                free_blocks = le16_to_cpu(desc->bg_free_blocks_count);
 180                desc->bg_free_blocks_count = cpu_to_le16(free_blocks + count);
 181                spin_unlock(sb_bgl_lock(sbi, group_no));
 182                mark_buffer_dirty(bh);
 183        }
 184}
 185
 186/*
 187 * The reservation window structure operations
 188 * --------------------------------------------
 189 * Operations include:
 190 * dump, find, add, remove, is_empty, find_next_reservable_window, etc.
 191 *
 192 * We use a red-black tree to represent per-filesystem reservation
 193 * windows.
 194 *
 195 */
 196
 197/**
 198 * __rsv_window_dump() -- Dump the filesystem block allocation reservation map
 199 * @rb_root:            root of per-filesystem reservation rb tree
 200 * @verbose:            verbose mode
 201 * @fn:                 function which wishes to dump the reservation map
 202 *
 203 * If verbose is turned on, it will print the whole block reservation
 204 * windows(start, end). Otherwise, it will only print out the "bad" windows,
 205 * those windows that overlap with their immediate neighbors.
 206 */
 207#if 1
 208static void __rsv_window_dump(struct rb_root *root, int verbose,
 209                              const char *fn)
 210{
 211        struct rb_node *n;
 212        struct ext2_reserve_window_node *rsv, *prev;
 213        int bad;
 214
 215restart:
 216        n = rb_first(root);
 217        bad = 0;
 218        prev = NULL;
 219
 220        printk("Block Allocation Reservation Windows Map (%s):\n", fn);
 221        while (n) {
 222                rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
 223                if (verbose)
 224                        printk("reservation window 0x%p "
 225                                "start: %lu, end: %lu\n",
 226                                rsv, rsv->rsv_start, rsv->rsv_end);
 227                if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) {
 228                        printk("Bad reservation %p (start >= end)\n",
 229                               rsv);
 230                        bad = 1;
 231                }
 232                if (prev && prev->rsv_end >= rsv->rsv_start) {
 233                        printk("Bad reservation %p (prev->end >= start)\n",
 234                               rsv);
 235                        bad = 1;
 236                }
 237                if (bad) {
 238                        if (!verbose) {
 239                                printk("Restarting reservation walk in verbose mode\n");
 240                                verbose = 1;
 241                                goto restart;
 242                        }
 243                }
 244                n = rb_next(n);
 245                prev = rsv;
 246        }
 247        printk("Window map complete.\n");
 248        BUG_ON(bad);
 249}
 250#define rsv_window_dump(root, verbose) \
 251        __rsv_window_dump((root), (verbose), __func__)
 252#else
 253#define rsv_window_dump(root, verbose) do {} while (0)
 254#endif
 255
 256/**
 257 * goal_in_my_reservation()
 258 * @rsv:                inode's reservation window
 259 * @grp_goal:           given goal block relative to the allocation block group
 260 * @group:              the current allocation block group
 261 * @sb:                 filesystem super block
 262 *
 263 * Test if the given goal block (group relative) is within the file's
 264 * own block reservation window range.
 265 *
 266 * If the reservation window is outside the goal allocation group, return 0;
 267 * grp_goal (given goal block) could be -1, which means no specific
 268 * goal block. In this case, always return 1.
 269 * If the goal block is within the reservation window, return 1;
 270 * otherwise, return 0;
 271 */
 272static int
 273goal_in_my_reservation(struct ext2_reserve_window *rsv, ext2_grpblk_t grp_goal,
 274                        unsigned int group, struct super_block * sb)
 275{
 276        ext2_fsblk_t group_first_block, group_last_block;
 277
 278        group_first_block = ext2_group_first_block_no(sb, group);
 279        group_last_block = group_first_block + EXT2_BLOCKS_PER_GROUP(sb) - 1;
 280
 281        if ((rsv->_rsv_start > group_last_block) ||
 282            (rsv->_rsv_end < group_first_block))
 283                return 0;
 284        if ((grp_goal >= 0) && ((grp_goal + group_first_block < rsv->_rsv_start)
 285                || (grp_goal + group_first_block > rsv->_rsv_end)))
 286                return 0;
 287        return 1;
 288}
 289
 290/**
 291 * search_reserve_window()
 292 * @rb_root:            root of reservation tree
 293 * @goal:               target allocation block
 294 *
 295 * Find the reserved window which includes the goal, or the previous one
 296 * if the goal is not in any window.
 297 * Returns NULL if there are no windows or if all windows start after the goal.
 298 */
 299static struct ext2_reserve_window_node *
 300search_reserve_window(struct rb_root *root, ext2_fsblk_t goal)
 301{
 302        struct rb_node *n = root->rb_node;
 303        struct ext2_reserve_window_node *rsv;
 304
 305        if (!n)
 306                return NULL;
 307
 308        do {
 309                rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
 310
 311                if (goal < rsv->rsv_start)
 312                        n = n->rb_left;
 313                else if (goal > rsv->rsv_end)
 314                        n = n->rb_right;
 315                else
 316                        return rsv;
 317        } while (n);
 318        /*
 319         * We've fallen off the end of the tree: the goal wasn't inside
 320         * any particular node.  OK, the previous node must be to one
 321         * side of the interval containing the goal.  If it's the RHS,
 322         * we need to back up one.
 323         */
 324        if (rsv->rsv_start > goal) {
 325                n = rb_prev(&rsv->rsv_node);
 326                rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
 327        }
 328        return rsv;
 329}
 330
 331/*
 332 * ext2_rsv_window_add() -- Insert a window to the block reservation rb tree.
 333 * @sb:                 super block
 334 * @rsv:                reservation window to add
 335 *
 336 * Must be called with rsv_lock held.
 337 */
 338void ext2_rsv_window_add(struct super_block *sb,
 339                    struct ext2_reserve_window_node *rsv)
 340{
 341        struct rb_root *root = &EXT2_SB(sb)->s_rsv_window_root;
 342        struct rb_node *node = &rsv->rsv_node;
 343        ext2_fsblk_t start = rsv->rsv_start;
 344
 345        struct rb_node ** p = &root->rb_node;
 346        struct rb_node * parent = NULL;
 347        struct ext2_reserve_window_node *this;
 348
 349        while (*p)
 350        {
 351                parent = *p;
 352                this = rb_entry(parent, struct ext2_reserve_window_node, rsv_node);
 353
 354                if (start < this->rsv_start)
 355                        p = &(*p)->rb_left;
 356                else if (start > this->rsv_end)
 357                        p = &(*p)->rb_right;
 358                else {
 359                        rsv_window_dump(root, 1);
 360                        BUG();
 361                }
 362        }
 363
 364        rb_link_node(node, parent, p);
 365        rb_insert_color(node, root);
 366}
 367
 368/**
 369 * rsv_window_remove() -- unlink a window from the reservation rb tree
 370 * @sb:                 super block
 371 * @rsv:                reservation window to remove
 372 *
 373 * Mark the block reservation window as not allocated, and unlink it
 374 * from the filesystem reservation window rb tree. Must be called with
 375 * rsv_lock held.
 376 */
 377static void rsv_window_remove(struct super_block *sb,
 378                              struct ext2_reserve_window_node *rsv)
 379{
 380        rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
 381        rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
 382        rsv->rsv_alloc_hit = 0;
 383        rb_erase(&rsv->rsv_node, &EXT2_SB(sb)->s_rsv_window_root);
 384}
 385
 386/*
 387 * rsv_is_empty() -- Check if the reservation window is allocated.
 388 * @rsv:                given reservation window to check
 389 *
 390 * returns 1 if the end block is EXT2_RESERVE_WINDOW_NOT_ALLOCATED.
 391 */
 392static inline int rsv_is_empty(struct ext2_reserve_window *rsv)
 393{
 394        /* a valid reservation end block could not be 0 */
 395        return (rsv->_rsv_end == EXT2_RESERVE_WINDOW_NOT_ALLOCATED);
 396}
 397
 398/**
 399 * ext2_init_block_alloc_info()
 400 * @inode:              file inode structure
 401 *
 402 * Allocate and initialize the  reservation window structure, and
 403 * link the window to the ext2 inode structure at last
 404 *
 405 * The reservation window structure is only dynamically allocated
 406 * and linked to ext2 inode the first time the open file
 407 * needs a new block. So, before every ext2_new_block(s) call, for
 408 * regular files, we should check whether the reservation window
 409 * structure exists or not. In the latter case, this function is called.
 410 * Fail to do so will result in block reservation being turned off for that
 411 * open file.
 412 *
 413 * This function is called from ext2_get_blocks_handle(), also called
 414 * when setting the reservation window size through ioctl before the file
 415 * is open for write (needs block allocation).
 416 *
 417 * Needs truncate_mutex protection prior to calling this function.
 418 */
 419void ext2_init_block_alloc_info(struct inode *inode)
 420{
 421        struct ext2_inode_info *ei = EXT2_I(inode);
 422        struct ext2_block_alloc_info *block_i;
 423        struct super_block *sb = inode->i_sb;
 424
 425        block_i = kmalloc(sizeof(*block_i), GFP_NOFS);
 426        if (block_i) {
 427                struct ext2_reserve_window_node *rsv = &block_i->rsv_window_node;
 428
 429                rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
 430                rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
 431
 432                /*
 433                 * if filesystem is mounted with NORESERVATION, the goal
 434                 * reservation window size is set to zero to indicate
 435                 * block reservation is off
 436                 */
 437                if (!test_opt(sb, RESERVATION))
 438                        rsv->rsv_goal_size = 0;
 439                else
 440                        rsv->rsv_goal_size = EXT2_DEFAULT_RESERVE_BLOCKS;
 441                rsv->rsv_alloc_hit = 0;
 442                block_i->last_alloc_logical_block = 0;
 443                block_i->last_alloc_physical_block = 0;
 444        }
 445        ei->i_block_alloc_info = block_i;
 446}
 447
 448/**
 449 * ext2_discard_reservation()
 450 * @inode:              inode
 451 *
 452 * Discard(free) block reservation window on last file close, or truncate
 453 * or at last iput().
 454 *
 455 * It is being called in three cases:
 456 *      ext2_release_file(): last writer closes the file
 457 *      ext2_clear_inode(): last iput(), when nobody links to this file.
 458 *      ext2_truncate(): when the block indirect map is about to change.
 459 */
 460void ext2_discard_reservation(struct inode *inode)
 461{
 462        struct ext2_inode_info *ei = EXT2_I(inode);
 463        struct ext2_block_alloc_info *block_i = ei->i_block_alloc_info;
 464        struct ext2_reserve_window_node *rsv;
 465        spinlock_t *rsv_lock = &EXT2_SB(inode->i_sb)->s_rsv_window_lock;
 466
 467        if (!block_i)
 468                return;
 469
 470        rsv = &block_i->rsv_window_node;
 471        if (!rsv_is_empty(&rsv->rsv_window)) {
 472                spin_lock(rsv_lock);
 473                if (!rsv_is_empty(&rsv->rsv_window))
 474                        rsv_window_remove(inode->i_sb, rsv);
 475                spin_unlock(rsv_lock);
 476        }
 477}
 478
 479/**
 480 * ext2_free_blocks() -- Free given blocks and update quota and i_blocks
 481 * @inode:              inode
 482 * @block:              start physcial block to free
 483 * @count:              number of blocks to free
 484 */
 485void ext2_free_blocks (struct inode * inode, unsigned long block,
 486                       unsigned long count)
 487{
 488        struct buffer_head *bitmap_bh = NULL;
 489        struct buffer_head * bh2;
 490        unsigned long block_group;
 491        unsigned long bit;
 492        unsigned long i;
 493        unsigned long overflow;
 494        struct super_block * sb = inode->i_sb;
 495        struct ext2_sb_info * sbi = EXT2_SB(sb);
 496        struct ext2_group_desc * desc;
 497        struct ext2_super_block * es = sbi->s_es;
 498        unsigned freed = 0, group_freed;
 499
 500        if (block < le32_to_cpu(es->s_first_data_block) ||
 501            block + count < block ||
 502            block + count > le32_to_cpu(es->s_blocks_count)) {
 503                ext2_error (sb, "ext2_free_blocks",
 504                            "Freeing blocks not in datazone - "
 505                            "block = %lu, count = %lu", block, count);
 506                goto error_return;
 507        }
 508
 509        ext2_debug ("freeing block(s) %lu-%lu\n", block, block + count - 1);
 510
 511do_more:
 512        overflow = 0;
 513        block_group = (block - le32_to_cpu(es->s_first_data_block)) /
 514                      EXT2_BLOCKS_PER_GROUP(sb);
 515        bit = (block - le32_to_cpu(es->s_first_data_block)) %
 516                      EXT2_BLOCKS_PER_GROUP(sb);
 517        /*
 518         * Check to see if we are freeing blocks across a group
 519         * boundary.
 520         */
 521        if (bit + count > EXT2_BLOCKS_PER_GROUP(sb)) {
 522                overflow = bit + count - EXT2_BLOCKS_PER_GROUP(sb);
 523                count -= overflow;
 524        }
 525        brelse(bitmap_bh);
 526        bitmap_bh = read_block_bitmap(sb, block_group);
 527        if (!bitmap_bh)
 528                goto error_return;
 529
 530        desc = ext2_get_group_desc (sb, block_group, &bh2);
 531        if (!desc)
 532                goto error_return;
 533
 534        if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
 535            in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
 536            in_range (block, le32_to_cpu(desc->bg_inode_table),
 537                      sbi->s_itb_per_group) ||
 538            in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table),
 539                      sbi->s_itb_per_group)) {
 540                ext2_error (sb, "ext2_free_blocks",
 541                            "Freeing blocks in system zones - "
 542                            "Block = %lu, count = %lu",
 543                            block, count);
 544                goto error_return;
 545        }
 546
 547        for (i = 0, group_freed = 0; i < count; i++) {
 548                if (!ext2_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
 549                                                bit + i, bitmap_bh->b_data)) {
 550                        ext2_error(sb, __func__,
 551                                "bit already cleared for block %lu", block + i);
 552                } else {
 553                        group_freed++;
 554                }
 555        }
 556
 557        mark_buffer_dirty(bitmap_bh);
 558        if (sb->s_flags & MS_SYNCHRONOUS)
 559                sync_dirty_buffer(bitmap_bh);
 560
 561        group_adjust_blocks(sb, block_group, desc, bh2, group_freed);
 562        freed += group_freed;
 563
 564        if (overflow) {
 565                block += count;
 566                count = overflow;
 567                goto do_more;
 568        }
 569error_return:
 570        brelse(bitmap_bh);
 571        release_blocks(sb, freed);
 572        dquot_free_block_nodirty(inode, freed);
 573}
 574
 575/**
 576 * bitmap_search_next_usable_block()
 577 * @start:              the starting block (group relative) of the search
 578 * @bh:                 bufferhead contains the block group bitmap
 579 * @maxblocks:          the ending block (group relative) of the reservation
 580 *
 581 * The bitmap search --- search forward through the actual bitmap on disk until
 582 * we find a bit free.
 583 */
 584static ext2_grpblk_t
 585bitmap_search_next_usable_block(ext2_grpblk_t start, struct buffer_head *bh,
 586                                        ext2_grpblk_t maxblocks)
 587{
 588        ext2_grpblk_t next;
 589
 590        next = ext2_find_next_zero_bit(bh->b_data, maxblocks, start);
 591        if (next >= maxblocks)
 592                return -1;
 593        return next;
 594}
 595
 596/**
 597 * find_next_usable_block()
 598 * @start:              the starting block (group relative) to find next
 599 *                      allocatable block in bitmap.
 600 * @bh:                 bufferhead contains the block group bitmap
 601 * @maxblocks:          the ending block (group relative) for the search
 602 *
 603 * Find an allocatable block in a bitmap.  We perform the "most
 604 * appropriate allocation" algorithm of looking for a free block near
 605 * the initial goal; then for a free byte somewhere in the bitmap;
 606 * then for any free bit in the bitmap.
 607 */
 608static ext2_grpblk_t
 609find_next_usable_block(int start, struct buffer_head *bh, int maxblocks)
 610{
 611        ext2_grpblk_t here, next;
 612        char *p, *r;
 613
 614        if (start > 0) {
 615                /*
 616                 * The goal was occupied; search forward for a free 
 617                 * block within the next XX blocks.
 618                 *
 619                 * end_goal is more or less random, but it has to be
 620                 * less than EXT2_BLOCKS_PER_GROUP. Aligning up to the
 621                 * next 64-bit boundary is simple..
 622                 */
 623                ext2_grpblk_t end_goal = (start + 63) & ~63;
 624                if (end_goal > maxblocks)
 625                        end_goal = maxblocks;
 626                here = ext2_find_next_zero_bit(bh->b_data, end_goal, start);
 627                if (here < end_goal)
 628                        return here;
 629                ext2_debug("Bit not found near goal\n");
 630        }
 631
 632        here = start;
 633        if (here < 0)
 634                here = 0;
 635
 636        p = ((char *)bh->b_data) + (here >> 3);
 637        r = memscan(p, 0, ((maxblocks + 7) >> 3) - (here >> 3));
 638        next = (r - ((char *)bh->b_data)) << 3;
 639
 640        if (next < maxblocks && next >= here)
 641                return next;
 642
 643        here = bitmap_search_next_usable_block(here, bh, maxblocks);
 644        return here;
 645}
 646
 647/**
 648 * ext2_try_to_allocate()
 649 * @sb:                 superblock
 650 * @group:              given allocation block group
 651 * @bitmap_bh:          bufferhead holds the block bitmap
 652 * @grp_goal:           given target block within the group
 653 * @count:              target number of blocks to allocate
 654 * @my_rsv:             reservation window
 655 *
 656 * Attempt to allocate blocks within a give range. Set the range of allocation
 657 * first, then find the first free bit(s) from the bitmap (within the range),
 658 * and at last, allocate the blocks by claiming the found free bit as allocated.
 659 *
 660 * To set the range of this allocation:
 661 *      if there is a reservation window, only try to allocate block(s)
 662 *      from the file's own reservation window;
 663 *      Otherwise, the allocation range starts from the give goal block,
 664 *      ends at the block group's last block.
 665 *
 666 * If we failed to allocate the desired block then we may end up crossing to a
 667 * new bitmap.
 668 */
 669static int
 670ext2_try_to_allocate(struct super_block *sb, int group,
 671                        struct buffer_head *bitmap_bh, ext2_grpblk_t grp_goal,
 672                        unsigned long *count,
 673                        struct ext2_reserve_window *my_rsv)
 674{
 675        ext2_fsblk_t group_first_block;
 676        ext2_grpblk_t start, end;
 677        unsigned long num = 0;
 678
 679        /* we do allocation within the reservation window if we have a window */
 680        if (my_rsv) {
 681                group_first_block = ext2_group_first_block_no(sb, group);
 682                if (my_rsv->_rsv_start >= group_first_block)
 683                        start = my_rsv->_rsv_start - group_first_block;
 684                else
 685                        /* reservation window cross group boundary */
 686                        start = 0;
 687                end = my_rsv->_rsv_end - group_first_block + 1;
 688                if (end > EXT2_BLOCKS_PER_GROUP(sb))
 689                        /* reservation window crosses group boundary */
 690                        end = EXT2_BLOCKS_PER_GROUP(sb);
 691                if ((start <= grp_goal) && (grp_goal < end))
 692                        start = grp_goal;
 693                else
 694                        grp_goal = -1;
 695        } else {
 696                if (grp_goal > 0)
 697                        start = grp_goal;
 698                else
 699                        start = 0;
 700                end = EXT2_BLOCKS_PER_GROUP(sb);
 701        }
 702
 703        BUG_ON(start > EXT2_BLOCKS_PER_GROUP(sb));
 704
 705repeat:
 706        if (grp_goal < 0) {
 707                grp_goal = find_next_usable_block(start, bitmap_bh, end);
 708                if (grp_goal < 0)
 709                        goto fail_access;
 710                if (!my_rsv) {
 711                        int i;
 712
 713                        for (i = 0; i < 7 && grp_goal > start &&
 714                                        !ext2_test_bit(grp_goal - 1,
 715                                                        bitmap_bh->b_data);
 716                                        i++, grp_goal--)
 717                                ;
 718                }
 719        }
 720        start = grp_goal;
 721
 722        if (ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group), grp_goal,
 723                                                        bitmap_bh->b_data)) {
 724                /*
 725                 * The block was allocated by another thread, or it was
 726                 * allocated and then freed by another thread
 727                 */
 728                start++;
 729                grp_goal++;
 730                if (start >= end)
 731                        goto fail_access;
 732                goto repeat;
 733        }
 734        num++;
 735        grp_goal++;
 736        while (num < *count && grp_goal < end
 737                && !ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group),
 738                                        grp_goal, bitmap_bh->b_data)) {
 739                num++;
 740                grp_goal++;
 741        }
 742        *count = num;
 743        return grp_goal - num;
 744fail_access:
 745        *count = num;
 746        return -1;
 747}
 748
 749/**
 750 *      find_next_reservable_window():
 751 *              find a reservable space within the given range.
 752 *              It does not allocate the reservation window for now:
 753 *              alloc_new_reservation() will do the work later.
 754 *
 755 *      @search_head: the head of the searching list;
 756 *              This is not necessarily the list head of the whole filesystem
 757 *
 758 *              We have both head and start_block to assist the search
 759 *              for the reservable space. The list starts from head,
 760 *              but we will shift to the place where start_block is,
 761 *              then start from there, when looking for a reservable space.
 762 *
 763 *      @size: the target new reservation window size
 764 *
 765 *      @group_first_block: the first block we consider to start
 766 *                      the real search from
 767 *
 768 *      @last_block:
 769 *              the maximum block number that our goal reservable space
 770 *              could start from. This is normally the last block in this
 771 *              group. The search will end when we found the start of next
 772 *              possible reservable space is out of this boundary.
 773 *              This could handle the cross boundary reservation window
 774 *              request.
 775 *
 776 *      basically we search from the given range, rather than the whole
 777 *      reservation double linked list, (start_block, last_block)
 778 *      to find a free region that is of my size and has not
 779 *      been reserved.
 780 *
 781 */
 782static int find_next_reservable_window(
 783                                struct ext2_reserve_window_node *search_head,
 784                                struct ext2_reserve_window_node *my_rsv,
 785                                struct super_block * sb,
 786                                ext2_fsblk_t start_block,
 787                                ext2_fsblk_t last_block)
 788{
 789        struct rb_node *next;
 790        struct ext2_reserve_window_node *rsv, *prev;
 791        ext2_fsblk_t cur;
 792        int size = my_rsv->rsv_goal_size;
 793
 794        /* TODO: make the start of the reservation window byte-aligned */
 795        /* cur = *start_block & ~7;*/
 796        cur = start_block;
 797        rsv = search_head;
 798        if (!rsv)
 799                return -1;
 800
 801        while (1) {
 802                if (cur <= rsv->rsv_end)
 803                        cur = rsv->rsv_end + 1;
 804
 805                /* TODO?
 806                 * in the case we could not find a reservable space
 807                 * that is what is expected, during the re-search, we could
 808                 * remember what's the largest reservable space we could have
 809                 * and return that one.
 810                 *
 811                 * For now it will fail if we could not find the reservable
 812                 * space with expected-size (or more)...
 813                 */
 814                if (cur > last_block)
 815                        return -1;              /* fail */
 816
 817                prev = rsv;
 818                next = rb_next(&rsv->rsv_node);
 819                rsv = rb_entry(next,struct ext2_reserve_window_node,rsv_node);
 820
 821                /*
 822                 * Reached the last reservation, we can just append to the
 823                 * previous one.
 824                 */
 825                if (!next)
 826                        break;
 827
 828                if (cur + size <= rsv->rsv_start) {
 829                        /*
 830                         * Found a reserveable space big enough.  We could
 831                         * have a reservation across the group boundary here
 832                         */
 833                        break;
 834                }
 835        }
 836        /*
 837         * we come here either :
 838         * when we reach the end of the whole list,
 839         * and there is empty reservable space after last entry in the list.
 840         * append it to the end of the list.
 841         *
 842         * or we found one reservable space in the middle of the list,
 843         * return the reservation window that we could append to.
 844         * succeed.
 845         */
 846
 847        if ((prev != my_rsv) && (!rsv_is_empty(&my_rsv->rsv_window)))
 848                rsv_window_remove(sb, my_rsv);
 849
 850        /*
 851         * Let's book the whole available window for now.  We will check the
 852         * disk bitmap later and then, if there are free blocks then we adjust
 853         * the window size if it's larger than requested.
 854         * Otherwise, we will remove this node from the tree next time
 855         * call find_next_reservable_window.
 856         */
 857        my_rsv->rsv_start = cur;
 858        my_rsv->rsv_end = cur + size - 1;
 859        my_rsv->rsv_alloc_hit = 0;
 860
 861        if (prev != my_rsv)
 862                ext2_rsv_window_add(sb, my_rsv);
 863
 864        return 0;
 865}
 866
 867/**
 868 *      alloc_new_reservation()--allocate a new reservation window
 869 *
 870 *              To make a new reservation, we search part of the filesystem
 871 *              reservation list (the list that inside the group). We try to
 872 *              allocate a new reservation window near the allocation goal,
 873 *              or the beginning of the group, if there is no goal.
 874 *
 875 *              We first find a reservable space after the goal, then from
 876 *              there, we check the bitmap for the first free block after
 877 *              it. If there is no free block until the end of group, then the
 878 *              whole group is full, we failed. Otherwise, check if the free
 879 *              block is inside the expected reservable space, if so, we
 880 *              succeed.
 881 *              If the first free block is outside the reservable space, then
 882 *              start from the first free block, we search for next available
 883 *              space, and go on.
 884 *
 885 *      on succeed, a new reservation will be found and inserted into the list
 886 *      It contains at least one free block, and it does not overlap with other
 887 *      reservation windows.
 888 *
 889 *      failed: we failed to find a reservation window in this group
 890 *
 891 *      @rsv: the reservation
 892 *
 893 *      @grp_goal: The goal (group-relative).  It is where the search for a
 894 *              free reservable space should start from.
 895 *              if we have a goal(goal >0 ), then start from there,
 896 *              no goal(goal = -1), we start from the first block
 897 *              of the group.
 898 *
 899 *      @sb: the super block
 900 *      @group: the group we are trying to allocate in
 901 *      @bitmap_bh: the block group block bitmap
 902 *
 903 */
 904static int alloc_new_reservation(struct ext2_reserve_window_node *my_rsv,
 905                ext2_grpblk_t grp_goal, struct super_block *sb,
 906                unsigned int group, struct buffer_head *bitmap_bh)
 907{
 908        struct ext2_reserve_window_node *search_head;
 909        ext2_fsblk_t group_first_block, group_end_block, start_block;
 910        ext2_grpblk_t first_free_block;
 911        struct rb_root *fs_rsv_root = &EXT2_SB(sb)->s_rsv_window_root;
 912        unsigned long size;
 913        int ret;
 914        spinlock_t *rsv_lock = &EXT2_SB(sb)->s_rsv_window_lock;
 915
 916        group_first_block = ext2_group_first_block_no(sb, group);
 917        group_end_block = group_first_block + (EXT2_BLOCKS_PER_GROUP(sb) - 1);
 918
 919        if (grp_goal < 0)
 920                start_block = group_first_block;
 921        else
 922                start_block = grp_goal + group_first_block;
 923
 924        size = my_rsv->rsv_goal_size;
 925
 926        if (!rsv_is_empty(&my_rsv->rsv_window)) {
 927                /*
 928                 * if the old reservation is cross group boundary
 929                 * and if the goal is inside the old reservation window,
 930                 * we will come here when we just failed to allocate from
 931                 * the first part of the window. We still have another part
 932                 * that belongs to the next group. In this case, there is no
 933                 * point to discard our window and try to allocate a new one
 934                 * in this group(which will fail). we should
 935                 * keep the reservation window, just simply move on.
 936                 *
 937                 * Maybe we could shift the start block of the reservation
 938                 * window to the first block of next group.
 939                 */
 940
 941                if ((my_rsv->rsv_start <= group_end_block) &&
 942                                (my_rsv->rsv_end > group_end_block) &&
 943                                (start_block >= my_rsv->rsv_start))
 944                        return -1;
 945
 946                if ((my_rsv->rsv_alloc_hit >
 947                     (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) {
 948                        /*
 949                         * if the previously allocation hit ratio is
 950                         * greater than 1/2, then we double the size of
 951                         * the reservation window the next time,
 952                         * otherwise we keep the same size window
 953                         */
 954                        size = size * 2;
 955                        if (size > EXT2_MAX_RESERVE_BLOCKS)
 956                                size = EXT2_MAX_RESERVE_BLOCKS;
 957                        my_rsv->rsv_goal_size= size;
 958                }
 959        }
 960
 961        spin_lock(rsv_lock);
 962        /*
 963         * shift the search start to the window near the goal block
 964         */
 965        search_head = search_reserve_window(fs_rsv_root, start_block);
 966
 967        /*
 968         * find_next_reservable_window() simply finds a reservable window
 969         * inside the given range(start_block, group_end_block).
 970         *
 971         * To make sure the reservation window has a free bit inside it, we
 972         * need to check the bitmap after we found a reservable window.
 973         */
 974retry:
 975        ret = find_next_reservable_window(search_head, my_rsv, sb,
 976                                                start_block, group_end_block);
 977
 978        if (ret == -1) {
 979                if (!rsv_is_empty(&my_rsv->rsv_window))
 980                        rsv_window_remove(sb, my_rsv);
 981                spin_unlock(rsv_lock);
 982                return -1;
 983        }
 984
 985        /*
 986         * On success, find_next_reservable_window() returns the
 987         * reservation window where there is a reservable space after it.
 988         * Before we reserve this reservable space, we need
 989         * to make sure there is at least a free block inside this region.
 990         *
 991         * Search the first free bit on the block bitmap.  Search starts from
 992         * the start block of the reservable space we just found.
 993         */
 994        spin_unlock(rsv_lock);
 995        first_free_block = bitmap_search_next_usable_block(
 996                        my_rsv->rsv_start - group_first_block,
 997                        bitmap_bh, group_end_block - group_first_block + 1);
 998
 999        if (first_free_block < 0) {
1000                /*
1001                 * no free block left on the bitmap, no point
1002                 * to reserve the space. return failed.
1003                 */
1004                spin_lock(rsv_lock);
1005                if (!rsv_is_empty(&my_rsv->rsv_window))
1006                        rsv_window_remove(sb, my_rsv);
1007                spin_unlock(rsv_lock);
1008                return -1;              /* failed */
1009        }
1010
1011        start_block = first_free_block + group_first_block;
1012        /*
1013         * check if the first free block is within the
1014         * free space we just reserved
1015         */
1016        if (start_block >= my_rsv->rsv_start && start_block <= my_rsv->rsv_end)
1017                return 0;               /* success */
1018        /*
1019         * if the first free bit we found is out of the reservable space
1020         * continue search for next reservable space,
1021         * start from where the free block is,
1022         * we also shift the list head to where we stopped last time
1023         */
1024        search_head = my_rsv;
1025        spin_lock(rsv_lock);
1026        goto retry;
1027}
1028
1029/**
1030 * try_to_extend_reservation()
1031 * @my_rsv:             given reservation window
1032 * @sb:                 super block
1033 * @size:               the delta to extend
1034 *
1035 * Attempt to expand the reservation window large enough to have
1036 * required number of free blocks
1037 *
1038 * Since ext2_try_to_allocate() will always allocate blocks within
1039 * the reservation window range, if the window size is too small,
1040 * multiple blocks allocation has to stop at the end of the reservation
1041 * window. To make this more efficient, given the total number of
1042 * blocks needed and the current size of the window, we try to
1043 * expand the reservation window size if necessary on a best-effort
1044 * basis before ext2_new_blocks() tries to allocate blocks.
1045 */
1046static void try_to_extend_reservation(struct ext2_reserve_window_node *my_rsv,
1047                        struct super_block *sb, int size)
1048{
1049        struct ext2_reserve_window_node *next_rsv;
1050        struct rb_node *next;
1051        spinlock_t *rsv_lock = &EXT2_SB(sb)->s_rsv_window_lock;
1052
1053        if (!spin_trylock(rsv_lock))
1054                return;
1055
1056        next = rb_next(&my_rsv->rsv_node);
1057
1058        if (!next)
1059                my_rsv->rsv_end += size;
1060        else {
1061                next_rsv = rb_entry(next, struct ext2_reserve_window_node, rsv_node);
1062
1063                if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size)
1064                        my_rsv->rsv_end += size;
1065                else
1066                        my_rsv->rsv_end = next_rsv->rsv_start - 1;
1067        }
1068        spin_unlock(rsv_lock);
1069}
1070
1071/**
1072 * ext2_try_to_allocate_with_rsv()
1073 * @sb:                 superblock
1074 * @group:              given allocation block group
1075 * @bitmap_bh:          bufferhead holds the block bitmap
1076 * @grp_goal:           given target block within the group
1077 * @count:              target number of blocks to allocate
1078 * @my_rsv:             reservation window
1079 *
1080 * This is the main function used to allocate a new block and its reservation
1081 * window.
1082 *
1083 * Each time when a new block allocation is need, first try to allocate from
1084 * its own reservation.  If it does not have a reservation window, instead of
1085 * looking for a free bit on bitmap first, then look up the reservation list to
1086 * see if it is inside somebody else's reservation window, we try to allocate a
1087 * reservation window for it starting from the goal first. Then do the block
1088 * allocation within the reservation window.
1089 *
1090 * This will avoid keeping on searching the reservation list again and
1091 * again when somebody is looking for a free block (without
1092 * reservation), and there are lots of free blocks, but they are all
1093 * being reserved.
1094 *
1095 * We use a red-black tree for the per-filesystem reservation list.
1096 */
1097static ext2_grpblk_t
1098ext2_try_to_allocate_with_rsv(struct super_block *sb, unsigned int group,
1099                        struct buffer_head *bitmap_bh, ext2_grpblk_t grp_goal,
1100                        struct ext2_reserve_window_node * my_rsv,
1101                        unsigned long *count)
1102{
1103        ext2_fsblk_t group_first_block, group_last_block;
1104        ext2_grpblk_t ret = 0;
1105        unsigned long num = *count;
1106
1107        /*
1108         * we don't deal with reservation when
1109         * filesystem is mounted without reservation
1110         * or the file is not a regular file
1111         * or last attempt to allocate a block with reservation turned on failed
1112         */
1113        if (my_rsv == NULL) {
1114                return ext2_try_to_allocate(sb, group, bitmap_bh,
1115                                                grp_goal, count, NULL);
1116        }
1117        /*
1118         * grp_goal is a group relative block number (if there is a goal)
1119         * 0 <= grp_goal < EXT2_BLOCKS_PER_GROUP(sb)
1120         * first block is a filesystem wide block number
1121         * first block is the block number of the first block in this group
1122         */
1123        group_first_block = ext2_group_first_block_no(sb, group);
1124        group_last_block = group_first_block + (EXT2_BLOCKS_PER_GROUP(sb) - 1);
1125
1126        /*
1127         * Basically we will allocate a new block from inode's reservation
1128         * window.
1129         *
1130         * We need to allocate a new reservation window, if:
1131         * a) inode does not have a reservation window; or
1132         * b) last attempt to allocate a block from existing reservation
1133         *    failed; or
1134         * c) we come here with a goal and with a reservation window
1135         *
1136         * We do not need to allocate a new reservation window if we come here
1137         * at the beginning with a goal and the goal is inside the window, or
1138         * we don't have a goal but already have a reservation window.
1139         * then we could go to allocate from the reservation window directly.
1140         */
1141        while (1) {
1142                if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
1143                        !goal_in_my_reservation(&my_rsv->rsv_window,
1144                                                grp_goal, group, sb)) {
1145                        if (my_rsv->rsv_goal_size < *count)
1146                                my_rsv->rsv_goal_size = *count;
1147                        ret = alloc_new_reservation(my_rsv, grp_goal, sb,
1148                                                        group, bitmap_bh);
1149                        if (ret < 0)
1150                                break;                  /* failed */
1151
1152                        if (!goal_in_my_reservation(&my_rsv->rsv_window,
1153                                                        grp_goal, group, sb))
1154                                grp_goal = -1;
1155                } else if (grp_goal >= 0) {
1156                        int curr = my_rsv->rsv_end -
1157                                        (grp_goal + group_first_block) + 1;
1158
1159                        if (curr < *count)
1160                                try_to_extend_reservation(my_rsv, sb,
1161                                                        *count - curr);
1162                }
1163
1164                if ((my_rsv->rsv_start > group_last_block) ||
1165                                (my_rsv->rsv_end < group_first_block)) {
1166                        rsv_window_dump(&EXT2_SB(sb)->s_rsv_window_root, 1);
1167                        BUG();
1168                }
1169                ret = ext2_try_to_allocate(sb, group, bitmap_bh, grp_goal,
1170                                           &num, &my_rsv->rsv_window);
1171                if (ret >= 0) {
1172                        my_rsv->rsv_alloc_hit += num;
1173                        *count = num;
1174                        break;                          /* succeed */
1175                }
1176                num = *count;
1177        }
1178        return ret;
1179}
1180
1181/**
1182 * ext2_has_free_blocks()
1183 * @sbi:                in-core super block structure.
1184 *
1185 * Check if filesystem has at least 1 free block available for allocation.
1186 */
1187static int ext2_has_free_blocks(struct ext2_sb_info *sbi)
1188{
1189        ext2_fsblk_t free_blocks, root_blocks;
1190
1191        free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
1192        root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
1193        if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
1194                !uid_eq(sbi->s_resuid, current_fsuid()) &&
1195                (gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) ||
1196                 !in_group_p (sbi->s_resgid))) {
1197                return 0;
1198        }
1199        return 1;
1200}
1201
1202/*
1203 * ext2_new_blocks() -- core block(s) allocation function
1204 * @inode:              file inode
1205 * @goal:               given target block(filesystem wide)
1206 * @count:              target number of blocks to allocate
1207 * @errp:               error code
1208 *
1209 * ext2_new_blocks uses a goal block to assist allocation.  If the goal is
1210 * free, or there is a free block within 32 blocks of the goal, that block
1211 * is allocated.  Otherwise a forward search is made for a free block; within 
1212 * each block group the search first looks for an entire free byte in the block
1213 * bitmap, and then for any free bit if that fails.
1214 * This function also updates quota and i_blocks field.
1215 */
1216ext2_fsblk_t ext2_new_blocks(struct inode *inode, ext2_fsblk_t goal,
1217                    unsigned long *count, int *errp)
1218{
1219        struct buffer_head *bitmap_bh = NULL;
1220        struct buffer_head *gdp_bh;
1221        int group_no;
1222        int goal_group;
1223        ext2_grpblk_t grp_target_blk;   /* blockgroup relative goal block */
1224        ext2_grpblk_t grp_alloc_blk;    /* blockgroup-relative allocated block*/
1225        ext2_fsblk_t ret_block;         /* filesyetem-wide allocated block */
1226        int bgi;                        /* blockgroup iteration index */
1227        int performed_allocation = 0;
1228        ext2_grpblk_t free_blocks;      /* number of free blocks in a group */
1229        struct super_block *sb;
1230        struct ext2_group_desc *gdp;
1231        struct ext2_super_block *es;
1232        struct ext2_sb_info *sbi;
1233        struct ext2_reserve_window_node *my_rsv = NULL;
1234        struct ext2_block_alloc_info *block_i;
1235        unsigned short windowsz = 0;
1236        unsigned long ngroups;
1237        unsigned long num = *count;
1238        int ret;
1239
1240        *errp = -ENOSPC;
1241        sb = inode->i_sb;
1242        if (!sb) {
1243                printk("ext2_new_blocks: nonexistent device");
1244                return 0;
1245        }
1246
1247        /*
1248         * Check quota for allocation of this block.
1249         */
1250        ret = dquot_alloc_block(inode, num);
1251        if (ret) {
1252                *errp = ret;
1253                return 0;
1254        }
1255
1256        sbi = EXT2_SB(sb);
1257        es = EXT2_SB(sb)->s_es;
1258        ext2_debug("goal=%lu.\n", goal);
1259        /*
1260         * Allocate a block from reservation only when
1261         * filesystem is mounted with reservation(default,-o reservation), and
1262         * it's a regular file, and
1263         * the desired window size is greater than 0 (One could use ioctl
1264         * command EXT2_IOC_SETRSVSZ to set the window size to 0 to turn off
1265         * reservation on that particular file)
1266         */
1267        block_i = EXT2_I(inode)->i_block_alloc_info;
1268        if (block_i) {
1269                windowsz = block_i->rsv_window_node.rsv_goal_size;
1270                if (windowsz > 0)
1271                        my_rsv = &block_i->rsv_window_node;
1272        }
1273
1274        if (!ext2_has_free_blocks(sbi)) {
1275                *errp = -ENOSPC;
1276                goto out;
1277        }
1278
1279        /*
1280         * First, test whether the goal block is free.
1281         */
1282        if (goal < le32_to_cpu(es->s_first_data_block) ||
1283            goal >= le32_to_cpu(es->s_blocks_count))
1284                goal = le32_to_cpu(es->s_first_data_block);
1285        group_no = (goal - le32_to_cpu(es->s_first_data_block)) /
1286                        EXT2_BLOCKS_PER_GROUP(sb);
1287        goal_group = group_no;
1288retry_alloc:
1289        gdp = ext2_get_group_desc(sb, group_no, &gdp_bh);
1290        if (!gdp)
1291                goto io_error;
1292
1293        free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
1294        /*
1295         * if there is not enough free blocks to make a new resevation
1296         * turn off reservation for this allocation
1297         */
1298        if (my_rsv && (free_blocks < windowsz)
1299                && (free_blocks > 0)
1300                && (rsv_is_empty(&my_rsv->rsv_window)))
1301                my_rsv = NULL;
1302
1303        if (free_blocks > 0) {
1304                grp_target_blk = ((goal - le32_to_cpu(es->s_first_data_block)) %
1305                                EXT2_BLOCKS_PER_GROUP(sb));
1306                bitmap_bh = read_block_bitmap(sb, group_no);
1307                if (!bitmap_bh)
1308                        goto io_error;
1309                grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
1310                                        bitmap_bh, grp_target_blk,
1311                                        my_rsv, &num);
1312                if (grp_alloc_blk >= 0)
1313                        goto allocated;
1314        }
1315
1316        ngroups = EXT2_SB(sb)->s_groups_count;
1317        smp_rmb();
1318
1319        /*
1320         * Now search the rest of the groups.  We assume that
1321         * group_no and gdp correctly point to the last group visited.
1322         */
1323        for (bgi = 0; bgi < ngroups; bgi++) {
1324                group_no++;
1325                if (group_no >= ngroups)
1326                        group_no = 0;
1327                gdp = ext2_get_group_desc(sb, group_no, &gdp_bh);
1328                if (!gdp)
1329                        goto io_error;
1330
1331                free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
1332                /*
1333                 * skip this group (and avoid loading bitmap) if there
1334                 * are no free blocks
1335                 */
1336                if (!free_blocks)
1337                        continue;
1338                /*
1339                 * skip this group if the number of
1340                 * free blocks is less than half of the reservation
1341                 * window size.
1342                 */
1343                if (my_rsv && (free_blocks <= (windowsz/2)))
1344                        continue;
1345
1346                brelse(bitmap_bh);
1347                bitmap_bh = read_block_bitmap(sb, group_no);
1348                if (!bitmap_bh)
1349                        goto io_error;
1350                /*
1351                 * try to allocate block(s) from this group, without a goal(-1).
1352                 */
1353                grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
1354                                        bitmap_bh, -1, my_rsv, &num);
1355                if (grp_alloc_blk >= 0)
1356                        goto allocated;
1357        }
1358        /*
1359         * We may end up a bogus earlier ENOSPC error due to
1360         * filesystem is "full" of reservations, but
1361         * there maybe indeed free blocks available on disk
1362         * In this case, we just forget about the reservations
1363         * just do block allocation as without reservations.
1364         */
1365        if (my_rsv) {
1366                my_rsv = NULL;
1367                windowsz = 0;
1368                group_no = goal_group;
1369                goto retry_alloc;
1370        }
1371        /* No space left on the device */
1372        *errp = -ENOSPC;
1373        goto out;
1374
1375allocated:
1376
1377        ext2_debug("using block group %d(%d)\n",
1378                        group_no, gdp->bg_free_blocks_count);
1379
1380        ret_block = grp_alloc_blk + ext2_group_first_block_no(sb, group_no);
1381
1382        if (in_range(le32_to_cpu(gdp->bg_block_bitmap), ret_block, num) ||
1383            in_range(le32_to_cpu(gdp->bg_inode_bitmap), ret_block, num) ||
1384            in_range(ret_block, le32_to_cpu(gdp->bg_inode_table),
1385                      EXT2_SB(sb)->s_itb_per_group) ||
1386            in_range(ret_block + num - 1, le32_to_cpu(gdp->bg_inode_table),
1387                      EXT2_SB(sb)->s_itb_per_group)) {
1388                ext2_error(sb, "ext2_new_blocks",
1389                            "Allocating block in system zone - "
1390                            "blocks from "E2FSBLK", length %lu",
1391                            ret_block, num);
1392                /*
1393                 * ext2_try_to_allocate marked the blocks we allocated as in
1394                 * use.  So we may want to selectively mark some of the blocks
1395                 * as free
1396                 */
1397                goto retry_alloc;
1398        }
1399
1400        performed_allocation = 1;
1401
1402        if (ret_block + num - 1 >= le32_to_cpu(es->s_blocks_count)) {
1403                ext2_error(sb, "ext2_new_blocks",
1404                            "block("E2FSBLK") >= blocks count(%d) - "
1405                            "block_group = %d, es == %p ", ret_block,
1406                        le32_to_cpu(es->s_blocks_count), group_no, es);
1407                goto out;
1408        }
1409
1410        group_adjust_blocks(sb, group_no, gdp, gdp_bh, -num);
1411        percpu_counter_sub(&sbi->s_freeblocks_counter, num);
1412
1413        mark_buffer_dirty(bitmap_bh);
1414        if (sb->s_flags & MS_SYNCHRONOUS)
1415                sync_dirty_buffer(bitmap_bh);
1416
1417        *errp = 0;
1418        brelse(bitmap_bh);
1419        dquot_free_block_nodirty(inode, *count-num);
1420        mark_inode_dirty(inode);
1421        *count = num;
1422        return ret_block;
1423
1424io_error:
1425        *errp = -EIO;
1426out:
1427        /*
1428         * Undo the block allocation
1429         */
1430        if (!performed_allocation) {
1431                dquot_free_block_nodirty(inode, *count);
1432                mark_inode_dirty(inode);
1433        }
1434        brelse(bitmap_bh);
1435        return 0;
1436}
1437
1438ext2_fsblk_t ext2_new_block(struct inode *inode, unsigned long goal, int *errp)
1439{
1440        unsigned long count = 1;
1441
1442        return ext2_new_blocks(inode, goal, &count, errp);
1443}
1444
1445#ifdef EXT2FS_DEBUG
1446
1447unsigned long ext2_count_free(struct buffer_head *map, unsigned int numchars)
1448{
1449        return numchars * BITS_PER_BYTE - memweight(map->b_data, numchars);
1450}
1451
1452#endif  /*  EXT2FS_DEBUG  */
1453
1454unsigned long ext2_count_free_blocks (struct super_block * sb)
1455{
1456        struct ext2_group_desc * desc;
1457        unsigned long desc_count = 0;
1458        int i;
1459#ifdef EXT2FS_DEBUG
1460        unsigned long bitmap_count, x;
1461        struct ext2_super_block *es;
1462
1463        es = EXT2_SB(sb)->s_es;
1464        desc_count = 0;
1465        bitmap_count = 0;
1466        desc = NULL;
1467        for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
1468                struct buffer_head *bitmap_bh;
1469                desc = ext2_get_group_desc (sb, i, NULL);
1470                if (!desc)
1471                        continue;
1472                desc_count += le16_to_cpu(desc->bg_free_blocks_count);
1473                bitmap_bh = read_block_bitmap(sb, i);
1474                if (!bitmap_bh)
1475                        continue;
1476                
1477                x = ext2_count_free(bitmap_bh, sb->s_blocksize);
1478                printk ("group %d: stored = %d, counted = %lu\n",
1479                        i, le16_to_cpu(desc->bg_free_blocks_count), x);
1480                bitmap_count += x;
1481                brelse(bitmap_bh);
1482        }
1483        printk("ext2_count_free_blocks: stored = %lu, computed = %lu, %lu\n",
1484                (long)le32_to_cpu(es->s_free_blocks_count),
1485                desc_count, bitmap_count);
1486        return bitmap_count;
1487#else
1488        for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
1489                desc = ext2_get_group_desc (sb, i, NULL);
1490                if (!desc)
1491                        continue;
1492                desc_count += le16_to_cpu(desc->bg_free_blocks_count);
1493        }
1494        return desc_count;
1495#endif
1496}
1497
1498static inline int test_root(int a, int b)
1499{
1500        int num = b;
1501
1502        while (a > num)
1503                num *= b;
1504        return num == a;
1505}
1506
1507static int ext2_group_sparse(int group)
1508{
1509        if (group <= 1)
1510                return 1;
1511        return (test_root(group, 3) || test_root(group, 5) ||
1512                test_root(group, 7));
1513}
1514
1515/**
1516 *      ext2_bg_has_super - number of blocks used by the superblock in group
1517 *      @sb: superblock for filesystem
1518 *      @group: group number to check
1519 *
1520 *      Return the number of blocks used by the superblock (primary or backup)
1521 *      in this group.  Currently this will be only 0 or 1.
1522 */
1523int ext2_bg_has_super(struct super_block *sb, int group)
1524{
1525        if (EXT2_HAS_RO_COMPAT_FEATURE(sb,EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
1526            !ext2_group_sparse(group))
1527                return 0;
1528        return 1;
1529}
1530
1531/**
1532 *      ext2_bg_num_gdb - number of blocks used by the group table in group
1533 *      @sb: superblock for filesystem
1534 *      @group: group number to check
1535 *
1536 *      Return the number of blocks used by the group descriptor table
1537 *      (primary or backup) in this group.  In the future there may be a
1538 *      different number of descriptor blocks in each group.
1539 */
1540unsigned long ext2_bg_num_gdb(struct super_block *sb, int group)
1541{
1542        return ext2_bg_has_super(sb, group) ? EXT2_SB(sb)->s_gdb_count : 0;
1543}
1544
1545
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