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/*

 *  linux/fs/ext2/balloc.c

 *

 * Copyright (C) 1992, 1993, 1994, 1995

 * Remy Card (card@masi.ibp.fr)

 * Laboratoire MASI - Institut Blaise Pascal

 * Universite Pierre et Marie Curie (Paris VI)

 *

 *  Enhanced block allocation by Stephen Tweedie (sct@dcs.ed.ac.uk), 1993

 *  Big-endian to little-endian byte-swapping/bitmaps by

 *        David S. Miller (davem@caip.rutgers.edu), 1995

 */

/*

 * balloc.c contains the blocks allocation and deallocation routines

 */

/*

 * The free blocks are managed by bitmaps.  A file system contains several

 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap

 * block for inodes, N blocks for the inode table and data blocks.

 *

 * The file system contains group descriptors which are located after the

 * super block.  Each descriptor contains the number of the bitmap block and

 * the free blocks count in the block.  The descriptors are loaded in memory

 * when a file system is mounted (see ext2_read_super).

 */

#include <linux/fs.h>

#include <linux/ext2_fs.h>

#include <linux/stat.h>

#include <linux/sched.h>

#include <linux/string.h>

#include <linux/locks.h>

#include <asm/bitops.h>

#include <asm/byteorder.h>

#define in_range(b, first, len)         ((b) >= (first) && (b) <= (first) + (len) - 1)

static struct ext2_group_desc * get_group_desc (struct super_block * sb,

                                                unsigned int block_group,

                                                struct buffer_head ** bh)

{

        unsigned long group_desc;

        unsigned long desc;

        struct ext2_group_desc * gdp;

        /*

         * This panic should never trigger on a bad filesystem: the caller

         * should have verified the block/group number already.

         */

        if (block_group >= sb->u.ext2_sb.s_groups_count)

                ext2_panic (sb, "get_group_desc",

                            "block_group >= groups_count - "

                            "block_group = %d, groups_count = %lu",

                            block_group, sb->u.ext2_sb.s_groups_count);

        group_desc = block_group / EXT2_DESC_PER_BLOCK(sb);

        desc = block_group % EXT2_DESC_PER_BLOCK(sb);

        if (!sb->u.ext2_sb.s_group_desc[group_desc])

                ext2_panic (sb, "get_group_desc",

                            "Group descriptor not loaded - "

                            "block_group = %d, group_desc = %lu, desc = %lu",

                             block_group, group_desc, desc);

        gdp = (struct ext2_group_desc *)

              sb->u.ext2_sb.s_group_desc[group_desc]->b_data;

        if (bh)

                *bh = sb->u.ext2_sb.s_group_desc[group_desc];

        return gdp + desc;

}

/*

 * Read the bitmap for a given block_group, reading into the specified

 * slot in the superblock's bitmap cache.

 *

 * Return >=0 on success or a -ve error code.

 */

static int read_block_bitmap (struct super_block * sb,

                              unsigned int block_group,

                              unsigned long bitmap_nr)

{

        struct ext2_group_desc * gdp;

        struct buffer_head * bh;

        int retval = 0;

        gdp = get_group_desc (sb, block_group, NULL);

        bh = bread (sb->s_dev, swab32(gdp->bg_block_bitmap), sb->s_blocksize);

        if (!bh) {

                ext2_error (sb, "read_block_bitmap",

                            "Cannot read block bitmap - "

                            "block_group = %d, block_bitmap = %lu",

                            block_group, (unsigned long) swab32(gdp->bg_block_bitmap));

                retval = -EIO;

        }

        /*

         * On IO error, just leave a zero in the superblock's block pointer for

         * this group.  The IO will be retried next time.

         */

        sb->u.ext2_sb.s_block_bitmap_number[bitmap_nr] = block_group;

        sb->u.ext2_sb.s_block_bitmap[bitmap_nr] = bh;

        return retval;

}

/*

 * load_block_bitmap loads the block bitmap for a blocks group

 *

 * It maintains a cache for the last bitmaps loaded.  This cache is managed

 * with a LRU algorithm.

 *

 * Notes:

 * 1/ There is one cache per mounted file system.

 * 2/ If the file system contains less than EXT2_MAX_GROUP_LOADED groups,

 *    this function reads the bitmap without maintaining a LRU cache.

 *

 * Return the slot used to store the bitmap, or a -ve error code.

 */

static int load__block_bitmap (struct super_block * sb,

                               unsigned int block_group)

{

        int i, j, retval = 0;

        unsigned long block_bitmap_number;

        struct buffer_head * block_bitmap;

        if (block_group >= sb->u.ext2_sb.s_groups_count)

                ext2_panic (sb, "load_block_bitmap",

                            "block_group >= groups_count - "

                            "block_group = %d, groups_count = %lu",

                            block_group, sb->u.ext2_sb.s_groups_count);

        if (sb->u.ext2_sb.s_groups_count <= EXT2_MAX_GROUP_LOADED) {

                if (sb->u.ext2_sb.s_block_bitmap[block_group]) {

                        if (sb->u.ext2_sb.s_block_bitmap_number[block_group] !=

                            block_group)

                                ext2_panic (sb, "load_block_bitmap",

                                            "block_group != block_bitmap_number");

                        else

                                return block_group;

                } else {

                        retval = read_block_bitmap (sb, block_group, block_group);

                        if (retval < 0)

                                return retval;

                        return block_group;

                }

        }

        for (i = 0; i < sb->u.ext2_sb.s_loaded_block_bitmaps &&

                    sb->u.ext2_sb.s_block_bitmap_number[i] != block_group; i++)

                ;

        if (i < sb->u.ext2_sb.s_loaded_block_bitmaps &&

            sb->u.ext2_sb.s_block_bitmap_number[i] == block_group) {

                block_bitmap_number = sb->u.ext2_sb.s_block_bitmap_number[i];

                block_bitmap = sb->u.ext2_sb.s_block_bitmap[i];

                for (j = i; j > 0; j--) {

                        sb->u.ext2_sb.s_block_bitmap_number[j] =

                                sb->u.ext2_sb.s_block_bitmap_number[j - 1];

                        sb->u.ext2_sb.s_block_bitmap[j] =

                                sb->u.ext2_sb.s_block_bitmap[j - 1];

                }

                sb->u.ext2_sb.s_block_bitmap_number[0] = block_bitmap_number;

                sb->u.ext2_sb.s_block_bitmap[0] = block_bitmap;

                /*

                 * There's still one special case here --- if block_bitmap == 0

                 * then our last attempt to read the bitmap failed and we have

                 * just ended up caching that failure.  Try again to read it.

                 */

                if (!block_bitmap)

                        retval = read_block_bitmap (sb, block_group, 0);

        } else {

                if (sb->u.ext2_sb.s_loaded_block_bitmaps < EXT2_MAX_GROUP_LOADED)

                        sb->u.ext2_sb.s_loaded_block_bitmaps++;

                else

                        brelse (sb->u.ext2_sb.s_block_bitmap[EXT2_MAX_GROUP_LOADED - 1]);

                for (j = sb->u.ext2_sb.s_loaded_block_bitmaps - 1; j > 0;  j--) {

                        sb->u.ext2_sb.s_block_bitmap_number[j] =

                                sb->u.ext2_sb.s_block_bitmap_number[j - 1];

                        sb->u.ext2_sb.s_block_bitmap[j] =

                                sb->u.ext2_sb.s_block_bitmap[j - 1];

                }

                retval = read_block_bitmap (sb, block_group, 0);

        }

        return retval;

}

/*

 * Load the block bitmap for a given block group.  First of all do a couple

 * of fast lookups for common cases and then pass the request onto the guts

 * of the bitmap loader.

 *

 * Return the slot number of the group in the superblock bitmap cache's on

 * success, or a -ve error code.

 *

 * There is still one inconsistancy here --- if the number of groups in this

 * filesystems is <= EXT2_MAX_GROUP_LOADED, then we have no way of

 * differentiating between a group for which we have never performed a bitmap

 * IO request, and a group for which the last bitmap read request failed.

 */

static inline int load_block_bitmap (struct super_block * sb,

                                     unsigned int block_group)

{

        int slot;

        /*

         * Do the lookup for the slot.  First of all, check if we're asking

         * for the same slot as last time, and did we succeed that last time?

         */

        if (sb->u.ext2_sb.s_loaded_block_bitmaps > 0 &&

            sb->u.ext2_sb.s_block_bitmap_number[0] == block_group &&

            sb->u.ext2_sb.s_block_bitmap[block_group]) {

                slot = 0;

        }

        /*

         * Or can we do a fast lookup based on a loaded group on a filesystem

         * small enough to be mapped directly into the superblock?

         */

        else if (sb->u.ext2_sb.s_groups_count <= EXT2_MAX_GROUP_LOADED &&

                 sb->u.ext2_sb.s_block_bitmap_number[block_group] == block_group &&

                 sb->u.ext2_sb.s_block_bitmap[block_group]) {

                slot = block_group;

        }

        /*

         * If not, then do a full lookup for this block group.

         */

        else {

                slot = load__block_bitmap (sb, block_group);

        }

        /*

         * <0 means we just got an error

         */

        if (slot < 0)

                return slot;

        /*

         * If it's a valid slot, we may still have cached a previous IO error,

         * in which case the bh in the superblock cache will be zero.

         */

        if (!sb->u.ext2_sb.s_block_bitmap[slot])

                return -EIO;

        /*

         * Must have been read in OK to get this far.

         */

        return slot;

}

void ext2_free_blocks (const struct inode * inode, unsigned long block,

                       unsigned long count)

{

        struct buffer_head * bh;

        struct buffer_head * bh2;

        unsigned long block_group;

        unsigned long bit;

        unsigned long i;

        int bitmap_nr;

        struct super_block * sb;

        struct ext2_group_desc * gdp;

        struct ext2_super_block * es;

        sb = inode->i_sb;

        if (!sb) {

                printk ("ext2_free_blocks: nonexistent device");

                return;

        }

        lock_super (sb);

        es = sb->u.ext2_sb.s_es;

        if (block < swab32(es->s_first_data_block) ||

            (block + count) > swab32(es->s_blocks_count)) {

                ext2_error (sb, "ext2_free_blocks",

                            "Freeing blocks not in datazone - "

                            "block = %lu, count = %lu", block, count);

                unlock_super (sb);

                return;

        }

        ext2_debug ("freeing block %lu\n", block);

        block_group = (block - swab32(es->s_first_data_block)) /

                      EXT2_BLOCKS_PER_GROUP(sb);

        bit = (block - swab32(es->s_first_data_block)) % EXT2_BLOCKS_PER_GROUP(sb);

        if (bit + count > EXT2_BLOCKS_PER_GROUP(sb)) {

                ext2_error (sb, "ext2_free_blocks",

                            "Freeing blocks across group boundary - "

                            "Block = %lu, count = %lu",

                            block, count);

                unlock_super (sb);

                return;

        }

        bitmap_nr = load_block_bitmap (sb, block_group);

        if (bitmap_nr < 0)

                goto error_return;

        bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];

        gdp = get_group_desc (sb, block_group, &bh2);

        if (test_opt (sb, CHECK_STRICT) &&

            (in_range (swab32(gdp->bg_block_bitmap), block, count) ||

             in_range (swab32(gdp->bg_inode_bitmap), block, count) ||

             in_range (block, swab32(gdp->bg_inode_table),

                       sb->u.ext2_sb.s_itb_per_group) ||

             in_range (block + count - 1, swab32(gdp->bg_inode_table),

                       sb->u.ext2_sb.s_itb_per_group))) {

                ext2_error (sb, "ext2_free_blocks",

                            "Freeing blocks in system zones - "

                            "Block = %lu, count = %lu",

                            block, count);

                unlock_super (sb);

                return;

        }

        for (i = 0; i < count; i++) {

                if (!__ext2_clear_bit (bit + i, bh->b_data))

                        ext2_warning (sb, "ext2_free_blocks",

                                      "bit already cleared for block %lu",

                                      block);

                else {

                        if (sb->dq_op)

                                sb->dq_op->free_block(inode, fs_to_dq_blocks(1, sb->s_blocksize));

                        gdp->bg_free_blocks_count =

                                swab16(swab16(gdp->bg_free_blocks_count)+1);

                        es->s_free_blocks_count =

                                swab32(swab32(es->s_free_blocks_count)+1);

                }

        }

        mark_buffer_dirty(bh2, 1);

        mark_buffer_dirty(sb->u.ext2_sb.s_sbh, 1);

        mark_buffer_dirty(bh, 1);

        if (sb->s_flags & MS_SYNCHRONOUS) {

                ll_rw_block (WRITE, 1, &bh);

                wait_on_buffer (bh);

        }

        sb->s_dirt = 1;

error_return:

        unlock_super (sb);

        return;

}

/*

 * ext2_new_block uses a goal block to assist allocation.  If the goal is

 * free, or there is a free block within 32 blocks of the goal, that block

 * is allocated.  Otherwise a forward search is made for a free block; within

 * each block group the search first looks for an entire free byte in the block

 * bitmap, and then for any free bit if that fails.

 */

int ext2_new_block (const struct inode * inode, unsigned long goal,

                    u32 * prealloc_count, u32 * prealloc_block, int * err)

{

        struct buffer_head * bh;

        struct buffer_head * bh2;

        char * p, * r;

        int i, j, k, tmp;

        int bitmap_nr;

        struct super_block * sb;

        struct ext2_group_desc * gdp;

        struct ext2_super_block * es;

        *err = -ENOSPC;

#ifdef EXT2FS_DEBUG

        static int goal_hits = 0, goal_attempts = 0;

#endif

        sb = inode->i_sb;

        if (!sb) {

                printk ("ext2_new_block: nonexistent device");

                return 0;

        }

        lock_super (sb);

        es = sb->u.ext2_sb.s_es;

        if (swab32(es->s_free_blocks_count) <= swab32(es->s_r_blocks_count) &&

            (!fsuser() && (sb->u.ext2_sb.s_resuid != current->fsuid) &&

             (sb->u.ext2_sb.s_resgid == 0 ||

              !in_group_p (sb->u.ext2_sb.s_resgid)))) {

                unlock_super (sb);

                return 0;

        }

        ext2_debug ("goal=%lu.\n", goal);

repeat:

        /*

         * First, test whether the goal block is free.

         */

        if (goal < swab32(es->s_first_data_block) || goal >= swab32(es->s_blocks_count))

                goal = swab32(es->s_first_data_block);

        i = (goal - swab32(es->s_first_data_block)) / EXT2_BLOCKS_PER_GROUP(sb);

        gdp = get_group_desc (sb, i, &bh2);

        if (swab16(gdp->bg_free_blocks_count) > 0) {

                j = ((goal - swab32(es->s_first_data_block)) % EXT2_BLOCKS_PER_GROUP(sb));

#ifdef EXT2FS_DEBUG

                if (j)

                        goal_attempts++;

#endif

                bitmap_nr = load_block_bitmap (sb, i);

                if (bitmap_nr < 0) {

                        *err = -EIO;

                        unlock_super (sb);

                        return 0;

                }

                bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];

                ext2_debug ("goal is at %d:%d.\n", i, j);

                if (!__ext2_test_bit(j, bh->b_data)) {

#ifdef EXT2FS_DEBUG

                        goal_hits++;

                        ext2_debug ("goal bit allocated.\n");

#endif

                        goto got_block;

                }

                if (j) {

                        /*

                         * The goal was occupied; search forward for a free

                         * block within the next XX blocks.

                         *

                         * end_goal is more or less random, but it has to be

                         * less than EXT2_BLOCKS_PER_GROUP. Aligning up to the

                         * next 64-bit boundary is simple..

                         */

                        int end_goal = (j + 63) & ~63;

                        j = __ext2_find_next_zero_bit(bh->b_data, end_goal, j);

                        if (j < end_goal)

                                goto got_block;

                }

                ext2_debug ("Bit not found near goal\n");

                /*

                 * There has been no free block found in the near vicinity

                 * of the goal: do a search forward through the block groups,

                 * searching in each group first for an entire free byte in

                 * the bitmap and then for any free bit.

                 *

                 * Search first in the remainder of the current group; then,

                 * cyclicly search through the rest of the groups.

                 */

                p = ((char *) bh->b_data) + (j >> 3);

                r = memscan(p, 0, (EXT2_BLOCKS_PER_GROUP(sb) - j + 7) >> 3);

                k = (r - ((char *) bh->b_data)) << 3;

                if (k < EXT2_BLOCKS_PER_GROUP(sb)) {

                        j = k;

                        goto search_back;

                }

                k = __ext2_find_next_zero_bit ((unsigned long *) bh->b_data,

                                        EXT2_BLOCKS_PER_GROUP(sb),

                                        j);

                if (k < EXT2_BLOCKS_PER_GROUP(sb)) {

                        j = k;

                        goto got_block;

                }

        }

        ext2_debug ("Bit not found in block group %d.\n", i);

        /*

         * Now search the rest of the groups.  We assume that

         * i and gdp correctly point to the last group visited.

         */

        for (k = 0; k < sb->u.ext2_sb.s_groups_count; k++) {

                i++;

                if (i >= sb->u.ext2_sb.s_groups_count)

                        i = 0;

                gdp = get_group_desc (sb, i, &bh2);

                if (swab16(gdp->bg_free_blocks_count) > 0)

                        break;

        }

        if (k >= sb->u.ext2_sb.s_groups_count) {

                unlock_super (sb);

                return 0;

        }

        bitmap_nr = load_block_bitmap (sb, i);

        if (bitmap_nr < 0) {

                *err = -EIO;

                unlock_super (sb);

                return 0;

        }

        bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];

        r = memscan(bh->b_data, 0, EXT2_BLOCKS_PER_GROUP(sb) >> 3);

        j = (r - bh->b_data) << 3;

        if (j < EXT2_BLOCKS_PER_GROUP(sb))

                goto search_back;

        else

                j = __ext2_find_first_zero_bit ((unsigned long *) bh->b_data,

                                         EXT2_BLOCKS_PER_GROUP(sb));

        if (j >= EXT2_BLOCKS_PER_GROUP(sb)) {

                ext2_error (sb, "ext2_new_block",

                            "Free blocks count corrupted for block group %d", i);

                unlock_super (sb);

                return 0;

        }

search_back:

        /*

         * We have succeeded in finding a free byte in the block

         * bitmap.  Now search backwards up to 7 bits to find the

         * start of this group of free blocks.

         */

        for (k = 0; k < 7 && j > 0 && !__ext2_test_bit (j - 1, bh->b_data); k++, j--);

got_block:

        ext2_debug ("using block group %d(%d)\n", i, gdp->bg_free_blocks_count);

        /*

         * Check quota for allocation of this block.

         */

        if (sb->dq_op)

                if (sb->dq_op->alloc_block (inode, fs_to_dq_blocks(1, sb->s_blocksize))) {

                        unlock_super (sb);

                        *err = -EDQUOT;

                        return 0;

                }

        tmp = j + i * EXT2_BLOCKS_PER_GROUP(sb) + swab32(es->s_first_data_block);

        if (test_opt (sb, CHECK_STRICT) &&

            (tmp == swab32(gdp->bg_block_bitmap) ||

             tmp == swab32(gdp->bg_inode_bitmap) ||

             in_range (tmp, swab32(gdp->bg_inode_table), sb->u.ext2_sb.s_itb_per_group))) {

                ext2_error (sb, "ext2_new_block",

                            "Allocating block in system zone - "

                            "block = %u", tmp);

                unlock_super (sb);

                *err = -EIO;

                return 0;

        }

        if (__ext2_set_bit (j, bh->b_data)) {

                ext2_warning (sb, "ext2_new_block",

                              "bit already set for block %d", j);

                if (sb->dq_op)

                        sb->dq_op->free_block(inode, fs_to_dq_blocks(1, sb->s_blocksize));

                goto repeat;

        }

        ext2_debug ("found bit %d\n", j);

        /*

         * Do block preallocation now if required.

         */

#ifdef EXT2_PREALLOCATE

        if (prealloc_block) {

                *prealloc_count = 0;

                *prealloc_block = tmp + 1;

                for (k = 1;

                     k < 8 && (j + k) < EXT2_BLOCKS_PER_GROUP(sb); k++) {

                        if (sb->dq_op)

                                if (sb->dq_op->alloc_block(inode, fs_to_dq_blocks(1, sb->s_blocksize)))

                                        break;

                        if (__ext2_set_bit (j + k, bh->b_data)) {

                                if (sb->dq_op)

                                        sb->dq_op->free_block(inode, fs_to_dq_blocks(1, sb->s_blocksize));

                                break;

                        }

                        (*prealloc_count)++;

                }

                gdp->bg_free_blocks_count =

                        swab16(swab16(gdp->bg_free_blocks_count) -

                               *prealloc_count);

                es->s_free_blocks_count =

                        swab32(swab32(es->s_free_blocks_count) -

                               *prealloc_count);

                ext2_debug ("Preallocated a further %lu bits.\n",

                            *prealloc_count);

        }

#endif

        j = tmp;

        mark_buffer_dirty(bh, 1);

        if (sb->s_flags & MS_SYNCHRONOUS) {

                ll_rw_block (WRITE, 1, &bh);

                wait_on_buffer (bh);

        }

        if (j >= swab32(es->s_blocks_count)) {

                ext2_error (sb, "ext2_new_block",

                            "block >= blocks count - "

                            "block_group = %d, block=%d", i, j);

                unlock_super (sb);

                return 0;

        }

        if (!(bh = getblk (sb->s_dev, j, sb->s_blocksize))) {

                ext2_error (sb, "ext2_new_block", "cannot get block %d", j);

                unlock_super (sb);

                return 0;

        }

        memset(bh->b_data, 0, sb->s_blocksize);

        mark_buffer_uptodate(bh, 1);

        mark_buffer_dirty(bh, 1);

        brelse (bh);

        ext2_debug ("allocating block %d. "

                    "Goal hits %d of %d.\n", j, goal_hits, goal_attempts);

        gdp->bg_free_blocks_count = swab16(swab16(gdp->bg_free_blocks_count) - 1);

        mark_buffer_dirty(bh2, 1);

        es->s_free_blocks_count = swab32(swab32(es->s_free_blocks_count) - 1);

        mark_buffer_dirty(sb->u.ext2_sb.s_sbh, 1);

        sb->s_dirt = 1;

        unlock_super (sb);

        *err = 0;

        return j;

}

unsigned long ext2_count_free_blocks (struct super_block * sb)

{

#ifdef EXT2FS_DEBUG

        struct ext2_super_block * es;

        unsigned long desc_count, bitmap_count, x;

        int bitmap_nr;

        struct ext2_group_desc * gdp;

        int i;

        lock_super (sb);

        es = sb->u.ext2_sb.s_es;

        desc_count = 0;

        bitmap_count = 0;

        gdp = NULL;

        for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++) {

                gdp = get_group_desc (sb, i, NULL);

                desc_count += swab16(gdp->bg_free_blocks_count);

                bitmap_nr = load_block_bitmap (sb, i);

                if (bitmap_nr < 0)

                        continue;

                x = ext2_count_free (sb->u.ext2_sb.s_block_bitmap[bitmap_nr],

                                     sb->s_blocksize);

                printk ("group %d: stored = %d, counted = %lu\n",

                        i, swab16(gdp->bg_free_blocks_count), x);

                bitmap_count += x;

        }

        printk("ext2_count_free_blocks: stored = %lu, computed = %lu, %lu\n",

               swab32(es->s_free_blocks_count), desc_count, bitmap_count);

        unlock_super (sb);

        return bitmap_count;

#else

        return swab32(sb->u.ext2_sb.s_es->s_free_blocks_count);

#endif

}