initial commit with v2.6.9

[linux-2.6.9-moxart.git] / fs / ext3 / balloc.c

/*
 *  linux/fs/ext3/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@redhat.com), 1993
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 */

#include <linux/config.h>
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd.h>
#include <linux/ext3_fs.h>
#include <linux/ext3_jbd.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>

/*
 * 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 ext3_read_super).
 */


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

struct ext3_group_desc * ext3_get_group_desc(struct super_block * sb,
                                             unsigned int block_group,
                                             struct buffer_head ** bh)
{
        unsigned long group_desc;
        unsigned long desc;
        struct ext3_group_desc * gdp;

        if (block_group >= EXT3_SB(sb)->s_groups_count) {
                ext3_error (sb, "ext3_get_group_desc",
                            "block_group >= groups_count - "
                            "block_group = %d, groups_count = %lu",
                            block_group, EXT3_SB(sb)->s_groups_count);

                return NULL;
        }

        group_desc = block_group / EXT3_DESC_PER_BLOCK(sb);
        desc = block_group % EXT3_DESC_PER_BLOCK(sb);
        if (!EXT3_SB(sb)->s_group_desc[group_desc]) {
                ext3_error (sb, "ext3_get_group_desc",
                            "Group descriptor not loaded - "
                            "block_group = %d, group_desc = %lu, desc = %lu",
                             block_group, group_desc, desc);
                return NULL;
        }

        gdp = (struct ext3_group_desc *) 
              EXT3_SB(sb)->s_group_desc[group_desc]->b_data;
        if (bh)
                *bh = EXT3_SB(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 buffer_head on success or NULL in case of failure.
 */
static struct buffer_head *
read_block_bitmap(struct super_block *sb, unsigned int block_group)
{
        struct ext3_group_desc * desc;
        struct buffer_head * bh = NULL;

        desc = ext3_get_group_desc (sb, block_group, NULL);
        if (!desc)
                goto error_out;
        bh = sb_bread(sb, le32_to_cpu(desc->bg_block_bitmap));
        if (!bh)
                ext3_error (sb, "read_block_bitmap",
                            "Cannot read block bitmap - "
                            "block_group = %d, block_bitmap = %u",
                            block_group, le32_to_cpu(desc->bg_block_bitmap));
error_out:
        return bh;
}

/* Free given blocks, update quota and i_blocks field */
void ext3_free_blocks (handle_t *handle, struct inode * inode,
                        unsigned long block, unsigned long count)
{
        struct buffer_head *bitmap_bh = NULL;
        struct buffer_head *gd_bh;
        unsigned long block_group;
        unsigned long bit;
        unsigned long i;
        unsigned long overflow;
        struct super_block * sb;
        struct ext3_group_desc * gdp;
        struct ext3_super_block * es;
        struct ext3_sb_info *sbi;
        int err = 0, ret;
        int dquot_freed_blocks = 0;

        sb = inode->i_sb;
        if (!sb) {
                printk ("ext3_free_blocks: nonexistent device");
                return;
        }
        sbi = EXT3_SB(sb);
        es = EXT3_SB(sb)->s_es;
        if (block < le32_to_cpu(es->s_first_data_block) ||
            block + count < block ||
            block + count > le32_to_cpu(es->s_blocks_count)) {
                ext3_error (sb, "ext3_free_blocks",
                            "Freeing blocks not in datazone - "
                            "block = %lu, count = %lu", block, count);
                goto error_return;
        }

        ext3_debug ("freeing block %lu\n", block);

do_more:
        overflow = 0;
        block_group = (block - le32_to_cpu(es->s_first_data_block)) /
                      EXT3_BLOCKS_PER_GROUP(sb);
        bit = (block - le32_to_cpu(es->s_first_data_block)) %
                      EXT3_BLOCKS_PER_GROUP(sb);
        /*
         * Check to see if we are freeing blocks across a group
         * boundary.
         */
        if (bit + count > EXT3_BLOCKS_PER_GROUP(sb)) {
                overflow = bit + count - EXT3_BLOCKS_PER_GROUP(sb);
                count -= overflow;
        }
        brelse(bitmap_bh);
        bitmap_bh = read_block_bitmap(sb, block_group);
        if (!bitmap_bh)
                goto error_return;
        gdp = ext3_get_group_desc (sb, block_group, &gd_bh);
        if (!gdp)
                goto error_return;

        if (in_range (le32_to_cpu(gdp->bg_block_bitmap), block, count) ||
            in_range (le32_to_cpu(gdp->bg_inode_bitmap), block, count) ||
            in_range (block, le32_to_cpu(gdp->bg_inode_table),
                      EXT3_SB(sb)->s_itb_per_group) ||
            in_range (block + count - 1, le32_to_cpu(gdp->bg_inode_table),
                      EXT3_SB(sb)->s_itb_per_group))
                ext3_error (sb, "ext3_free_blocks",
                            "Freeing blocks in system zones - "
                            "Block = %lu, count = %lu",
                            block, count);

        /*
         * We are about to start releasing blocks in the bitmap,
         * so we need undo access.
         */
        /* @@@ check errors */
        BUFFER_TRACE(bitmap_bh, "getting undo access");
        err = ext3_journal_get_undo_access(handle, bitmap_bh, NULL);
        if (err)
                goto error_return;

        /*
         * We are about to modify some metadata.  Call the journal APIs
         * to unshare ->b_data if a currently-committing transaction is
         * using it
         */
        BUFFER_TRACE(gd_bh, "get_write_access");
        err = ext3_journal_get_write_access(handle, gd_bh);
        if (err)
                goto error_return;

        jbd_lock_bh_state(bitmap_bh);

        for (i = 0; i < count; i++) {
                /*
                 * An HJ special.  This is expensive...
                 */
#ifdef CONFIG_JBD_DEBUG
                jbd_unlock_bh_state(bitmap_bh);
                {
                        struct buffer_head *debug_bh;
                        debug_bh = sb_find_get_block(sb, block + i);
                        if (debug_bh) {
                                BUFFER_TRACE(debug_bh, "Deleted!");
                                if (!bh2jh(bitmap_bh)->b_committed_data)
                                        BUFFER_TRACE(debug_bh,
                                                "No commited data in bitmap");
                                BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap");
                                __brelse(debug_bh);
                        }
                }
                jbd_lock_bh_state(bitmap_bh);
#endif
                /* @@@ This prevents newly-allocated data from being
                 * freed and then reallocated within the same
                 * transaction. 
                 * 
                 * Ideally we would want to allow that to happen, but to
                 * do so requires making journal_forget() capable of
                 * revoking the queued write of a data block, which
                 * implies blocking on the journal lock.  *forget()
                 * cannot block due to truncate races.
                 *
                 * Eventually we can fix this by making journal_forget()
                 * return a status indicating whether or not it was able
                 * to revoke the buffer.  On successful revoke, it is
                 * safe not to set the allocation bit in the committed
                 * bitmap, because we know that there is no outstanding
                 * activity on the buffer any more and so it is safe to
                 * reallocate it.  
                 */
                BUFFER_TRACE(bitmap_bh, "set in b_committed_data");
                J_ASSERT_BH(bitmap_bh,
                                bh2jh(bitmap_bh)->b_committed_data != NULL);
                ext3_set_bit_atomic(sb_bgl_lock(sbi, block_group), bit + i,
                                bh2jh(bitmap_bh)->b_committed_data);

                /*
                 * We clear the bit in the bitmap after setting the committed
                 * data bit, because this is the reverse order to that which
                 * the allocator uses.
                 */
                BUFFER_TRACE(bitmap_bh, "clear bit");
                if (!ext3_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
                                                bit + i, bitmap_bh->b_data)) {
                        jbd_unlock_bh_state(bitmap_bh);
                        ext3_error(sb, __FUNCTION__,
                                "bit already cleared for block %lu", block + i);
                        jbd_lock_bh_state(bitmap_bh);
                        BUFFER_TRACE(bitmap_bh, "bit already cleared");
                } else {
                        dquot_freed_blocks++;
                }
        }
        jbd_unlock_bh_state(bitmap_bh);

        spin_lock(sb_bgl_lock(sbi, block_group));
        gdp->bg_free_blocks_count =
                cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count) +
                        dquot_freed_blocks);
        spin_unlock(sb_bgl_lock(sbi, block_group));
        percpu_counter_mod(&sbi->s_freeblocks_counter, count);

        /* We dirtied the bitmap block */
        BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
        err = ext3_journal_dirty_metadata(handle, bitmap_bh);

        /* And the group descriptor block */
        BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
        ret = ext3_journal_dirty_metadata(handle, gd_bh);
        if (!err) err = ret;

        if (overflow && !err) {
                block += count;
                count = overflow;
                goto do_more;
        }
        sb->s_dirt = 1;
error_return:
        brelse(bitmap_bh);
        ext3_std_error(sb, err);
        if (dquot_freed_blocks)
                DQUOT_FREE_BLOCK(inode, dquot_freed_blocks);
        return;
}

/*
 * For ext3 allocations, we must not reuse any blocks which are
 * allocated in the bitmap buffer's "last committed data" copy.  This
 * prevents deletes from freeing up the page for reuse until we have
 * committed the delete transaction.
 *
 * If we didn't do this, then deleting something and reallocating it as
 * data would allow the old block to be overwritten before the
 * transaction committed (because we force data to disk before commit).
 * This would lead to corruption if we crashed between overwriting the
 * data and committing the delete. 
 *
 * @@@ We may want to make this allocation behaviour conditional on
 * data-writes at some point, and disable it for metadata allocations or
 * sync-data inodes.
 */
static inline int ext3_test_allocatable(int nr, struct buffer_head *bh)
{
        int ret;
        struct journal_head *jh = bh2jh(bh);

        if (ext3_test_bit(nr, bh->b_data))
                return 0;

        jbd_lock_bh_state(bh);
        if (!jh->b_committed_data)
                ret = 1;
        else
                ret = !ext3_test_bit(nr, jh->b_committed_data);
        jbd_unlock_bh_state(bh);
        return ret;
}

/*
 * Find an allocatable block in a bitmap.  We honour both the bitmap and
 * its last-committed copy (if that exists), and perform the "most
 * appropriate allocation" algorithm of looking for a free block near
 * the initial goal; then for a free byte somewhere in the bitmap; then
 * for any free bit in the bitmap.
 */
static int
find_next_usable_block(int start, struct buffer_head *bh, int maxblocks)
{
        int here, next;
        char *p, *r;
        struct journal_head *jh = bh2jh(bh);

        if (start > 0) {
                /*
                 * 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 EXT3_BLOCKS_PER_GROUP. Aligning up to the
                 * next 64-bit boundary is simple..
                 */
                int end_goal = (start + 63) & ~63;
                here = ext3_find_next_zero_bit(bh->b_data, end_goal, start);
                if (here < end_goal && ext3_test_allocatable(here, bh))
                        return here;
                ext3_debug("Bit not found near goal\n");
        }

        here = start;
        if (here < 0)
                here = 0;

        p = ((char *)bh->b_data) + (here >> 3);
        r = memscan(p, 0, (maxblocks - here + 7) >> 3);
        next = (r - ((char *)bh->b_data)) << 3;

        if (next < maxblocks && ext3_test_allocatable(next, bh))
                return next;

        /*
         * The bitmap search --- search forward alternately through the actual
         * bitmap and the last-committed copy until we find a bit free in
         * both
         */
        while (here < maxblocks) {
                next = ext3_find_next_zero_bit(bh->b_data, maxblocks, here);
                if (next >= maxblocks)
                        return -1;
                if (ext3_test_allocatable(next, bh))
                        return next;
                jbd_lock_bh_state(bh);
                if (jh->b_committed_data)
                        here = ext3_find_next_zero_bit(jh->b_committed_data,
                                                        maxblocks, next);
                jbd_unlock_bh_state(bh);
        }
        return -1;
}

/*
 * We think we can allocate this block in this bitmap.  Try to set the bit.
 * If that succeeds then check that nobody has allocated and then freed the
 * block since we saw that is was not marked in b_committed_data.  If it _was_
 * allocated and freed then clear the bit in the bitmap again and return
 * zero (failure).
 */
static inline int
claim_block(spinlock_t *lock, int block, struct buffer_head *bh)
{
        struct journal_head *jh = bh2jh(bh);
        int ret;

        if (ext3_set_bit_atomic(lock, block, bh->b_data))
                return 0;
        jbd_lock_bh_state(bh);
        if (jh->b_committed_data && ext3_test_bit(block,jh->b_committed_data)) {
                ext3_clear_bit_atomic(lock, block, bh->b_data);
                ret = 0;
        } else {
                ret = 1;
        }
        jbd_unlock_bh_state(bh);
        return ret;
}

/*
 * If we failed to allocate the desired block then we may end up crossing to a
 * new bitmap.  In that case we must release write access to the old one via
 * ext3_journal_release_buffer(), else we'll run out of credits.
 */
static int
ext3_try_to_allocate(struct super_block *sb, handle_t *handle, int group,
                struct buffer_head *bitmap_bh, int goal, int *errp)
{
        int i;
        int fatal;
        int credits = 0;

        *errp = 0;

        /*
         * Make sure we use undo access for the bitmap, because it is critical
         * that we do the frozen_data COW on bitmap buffers in all cases even
         * if the buffer is in BJ_Forget state in the committing transaction.
         */
        BUFFER_TRACE(bitmap_bh, "get undo access for new block");
        fatal = ext3_journal_get_undo_access(handle, bitmap_bh, &credits);
        if (fatal) {
                *errp = fatal;
                goto fail;
        }

repeat:
        if (goal < 0 || !ext3_test_allocatable(goal, bitmap_bh)) {
                goal = find_next_usable_block(goal, bitmap_bh,
                                        EXT3_BLOCKS_PER_GROUP(sb));
                if (goal < 0)
                        goto fail_access;

                for (i = 0; i < 7 && goal > 0 &&
                                ext3_test_allocatable(goal - 1, bitmap_bh);
                        i++, goal--);
        }

        if (!claim_block(sb_bgl_lock(EXT3_SB(sb), group), goal, bitmap_bh)) {
                /*
                 * The block was allocated by another thread, or it was
                 * allocated and then freed by another thread
                 */
                goal++;
                if (goal >= EXT3_BLOCKS_PER_GROUP(sb))
                        goto fail_access;
                goto repeat;
        }

        BUFFER_TRACE(bitmap_bh, "journal_dirty_metadata for bitmap block");
        fatal = ext3_journal_dirty_metadata(handle, bitmap_bh);
        if (fatal) {
                *errp = fatal;
                goto fail;
        }
        return goal;

fail_access:
        BUFFER_TRACE(bitmap_bh, "journal_release_buffer");
        ext3_journal_release_buffer(handle, bitmap_bh, credits);
fail:
        return -1;
}

static int ext3_has_free_blocks(struct ext3_sb_info *sbi)
{
        int free_blocks, root_blocks;

        free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
        root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
        if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
                sbi->s_resuid != current->fsuid &&
                (sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
                return 0;
        }
        return 1;
}

/*
 * ext3_should_retry_alloc() is called when ENOSPC is returned, and if
 * it is profitable to retry the operation, this function will wait
 * for the current or commiting transaction to complete, and then
 * return TRUE.
 */
int ext3_should_retry_alloc(struct super_block *sb, int *retries)
{
        if (!ext3_has_free_blocks(EXT3_SB(sb)) || (*retries)++ > 3)
                return 0;

        jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);

        return journal_force_commit_nested(EXT3_SB(sb)->s_journal);
}

/*
 * ext3_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.
 * This function also updates quota and i_blocks field.
 */
int
ext3_new_block(handle_t *handle, struct inode *inode, unsigned long goal,
                u32 *prealloc_count, u32 *prealloc_block, int *errp)
{
        struct buffer_head *bitmap_bh = NULL;   /* bh */
        struct buffer_head *gdp_bh;             /* bh2 */
        int group_no;                           /* i */
        int ret_block;                          /* j */
        int bgi;                                /* blockgroup iteration index */
        int target_block;                       /* tmp */
        int fatal = 0, err;
        int performed_allocation = 0;
        int free_blocks;
        struct super_block *sb;
        struct ext3_group_desc *gdp;
        struct ext3_super_block *es;
        struct ext3_sb_info *sbi;
#ifdef EXT3FS_DEBUG
        static int goal_hits, goal_attempts;
#endif
        *errp = -ENOSPC;
        sb = inode->i_sb;
        if (!sb) {
                printk("ext3_new_block: nonexistent device");
                return 0;
        }

        /*
         * Check quota for allocation of this block.
         */
        if (DQUOT_ALLOC_BLOCK(inode, 1)) {
                *errp = -EDQUOT;
                return 0;
        }

        sbi = EXT3_SB(sb);
        es = EXT3_SB(sb)->s_es;
        ext3_debug("goal=%lu.\n", goal);

        if (!ext3_has_free_blocks(sbi)) {
                *errp = -ENOSPC;
                goto out;
        }

        /*
         * First, test whether the goal block is free.
         */
        if (goal < le32_to_cpu(es->s_first_data_block) ||
            goal >= le32_to_cpu(es->s_blocks_count))
                goal = le32_to_cpu(es->s_first_data_block);
        group_no = (goal - le32_to_cpu(es->s_first_data_block)) /
                        EXT3_BLOCKS_PER_GROUP(sb);
        gdp = ext3_get_group_desc(sb, group_no, &gdp_bh);
        if (!gdp)
                goto io_error;

        free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
        if (free_blocks > 0) {
                ret_block = ((goal - le32_to_cpu(es->s_first_data_block)) %
                                EXT3_BLOCKS_PER_GROUP(sb));
                bitmap_bh = read_block_bitmap(sb, group_no);
                if (!bitmap_bh)
                        goto io_error;
                ret_block = ext3_try_to_allocate(sb, handle, group_no,
                                        bitmap_bh, ret_block, &fatal);
                if (fatal)
                        goto out;
                if (ret_block >= 0)
                        goto allocated;
        }

        /*
         * Now search the rest of the groups.  We assume that 
         * i and gdp correctly point to the last group visited.
         */
        for (bgi = 0; bgi < EXT3_SB(sb)->s_groups_count; bgi++) {
                group_no++;
                if (group_no >= EXT3_SB(sb)->s_groups_count)
                        group_no = 0;
                gdp = ext3_get_group_desc(sb, group_no, &gdp_bh);
                if (!gdp) {
                        *errp = -EIO;
                        goto out;
                }
                free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
                if (free_blocks <= 0)
                        continue;

                brelse(bitmap_bh);
                bitmap_bh = read_block_bitmap(sb, group_no);
                if (!bitmap_bh)
                        goto io_error;
                ret_block = ext3_try_to_allocate(sb, handle, group_no,
                                                bitmap_bh, -1, &fatal);
                if (fatal)
                        goto out;
                if (ret_block >= 0) 
                        goto allocated;
        }

        /* No space left on the device */
        *errp = -ENOSPC;
        goto out;

allocated:

        ext3_debug("using block group %d(%d)\n",
                        group_no, gdp->bg_free_blocks_count);

        BUFFER_TRACE(gdp_bh, "get_write_access");
        fatal = ext3_journal_get_write_access(handle, gdp_bh);
        if (fatal)
                goto out;

        target_block = ret_block + group_no * EXT3_BLOCKS_PER_GROUP(sb)
                                + le32_to_cpu(es->s_first_data_block);

        if (target_block == le32_to_cpu(gdp->bg_block_bitmap) ||
            target_block == le32_to_cpu(gdp->bg_inode_bitmap) ||
            in_range(target_block, le32_to_cpu(gdp->bg_inode_table),
                      EXT3_SB(sb)->s_itb_per_group))
                ext3_error(sb, "ext3_new_block",
                            "Allocating block in system zone - "
                            "block = %u", target_block);

        performed_allocation = 1;

#ifdef CONFIG_JBD_DEBUG
        {
                struct buffer_head *debug_bh;

                /* Record bitmap buffer state in the newly allocated block */
                debug_bh = sb_find_get_block(sb, target_block);
                if (debug_bh) {
                        BUFFER_TRACE(debug_bh, "state when allocated");
                        BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap state");
                        brelse(debug_bh);
                }
        }
        jbd_lock_bh_state(bitmap_bh);
        spin_lock(sb_bgl_lock(sbi, group_no));
        if (buffer_jbd(bitmap_bh) && bh2jh(bitmap_bh)->b_committed_data) {
                if (ext3_test_bit(ret_block,
                                bh2jh(bitmap_bh)->b_committed_data)) {
                        printk("%s: block was unexpectedly set in "
                                "b_committed_data\n", __FUNCTION__);
                }
        }
        ext3_debug("found bit %d\n", ret_block);
        spin_unlock(sb_bgl_lock(sbi, group_no));
        jbd_unlock_bh_state(bitmap_bh);
#endif

        /* ret_block was blockgroup-relative.  Now it becomes fs-relative */
        ret_block = target_block;

        if (ret_block >= le32_to_cpu(es->s_blocks_count)) {
                ext3_error(sb, "ext3_new_block",
                            "block(%d) >= blocks count(%d) - "
                            "block_group = %d, es == %p ", ret_block,
                        le32_to_cpu(es->s_blocks_count), group_no, es);
                goto out;
        }

        /*
         * It is up to the caller to add the new buffer to a journal
         * list of some description.  We don't know in advance whether
         * the caller wants to use it as metadata or data.
         */
        ext3_debug("allocating block %d. Goal hits %d of %d.\n",
                        ret_block, goal_hits, goal_attempts);

        spin_lock(sb_bgl_lock(sbi, group_no));
        gdp->bg_free_blocks_count =
                        cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count) - 1);
        spin_unlock(sb_bgl_lock(sbi, group_no));
        percpu_counter_mod(&sbi->s_freeblocks_counter, -1);

        BUFFER_TRACE(gdp_bh, "journal_dirty_metadata for group descriptor");
        err = ext3_journal_dirty_metadata(handle, gdp_bh);
        if (!fatal)
                fatal = err;

        sb->s_dirt = 1;
        if (fatal)
                goto out;

        *errp = 0;
        brelse(bitmap_bh);
        return ret_block;

io_error:
        *errp = -EIO;
out:
        if (fatal) {
                *errp = fatal;
                ext3_std_error(sb, fatal);
        }
        /*
         * Undo the block allocation
         */
        if (!performed_allocation)
                DQUOT_FREE_BLOCK(inode, 1);
        brelse(bitmap_bh);
        return 0;
}

unsigned long ext3_count_free_blocks(struct super_block *sb)
{
        unsigned long desc_count;
        struct ext3_group_desc *gdp;
        int i;
#ifdef EXT3FS_DEBUG
        struct ext3_super_block *es;
        unsigned long bitmap_count, x;
        struct buffer_head *bitmap_bh = NULL;

        lock_super(sb);
        es = EXT3_SB(sb)->s_es;
        desc_count = 0;
        bitmap_count = 0;
        gdp = NULL;
        for (i = 0; i < EXT3_SB(sb)->s_groups_count; i++) {
                gdp = ext3_get_group_desc(sb, i, NULL);
                if (!gdp)
                        continue;
                desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
                brelse(bitmap_bh);
                bitmap_bh = read_block_bitmap(sb, i);
                if (bitmap_bh == NULL)
                        continue;

                x = ext3_count_free(bitmap_bh, sb->s_blocksize);
                printk("group %d: stored = %d, counted = %lu\n",
                        i, le16_to_cpu(gdp->bg_free_blocks_count), x);
                bitmap_count += x;
        }
        brelse(bitmap_bh);
        printk("ext3_count_free_blocks: stored = %u, computed = %lu, %lu\n",
               le32_to_cpu(es->s_free_blocks_count), desc_count, bitmap_count);
        unlock_super(sb);
        return bitmap_count;
#else
        desc_count = 0;
        for (i = 0; i < EXT3_SB(sb)->s_groups_count; i++) {
                gdp = ext3_get_group_desc(sb, i, NULL);
                if (!gdp)
                        continue;
                desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
        }

        return desc_count;
#endif
}

static inline int block_in_use(unsigned long block,
                                struct super_block * sb,
                                unsigned char * map)
{
        return ext3_test_bit ((block -
                le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block)) %
                         EXT3_BLOCKS_PER_GROUP(sb), map);
}

static inline int test_root(int a, int b)
{
        if (a == 0)
                return 1;
        while (1) {
                if (a == 1)
                        return 1;
                if (a % b)
                        return 0;
                a = a / b;
        }
}

int ext3_group_sparse(int group)
{
        return (test_root(group, 3) || test_root(group, 5) ||
                test_root(group, 7));
}

/**
 *      ext3_bg_has_super - number of blocks used by the superblock in group
 *      @sb: superblock for filesystem
 *      @group: group number to check
 *
 *      Return the number of blocks used by the superblock (primary or backup)
 *      in this group.  Currently this will be only 0 or 1.
 */
int ext3_bg_has_super(struct super_block *sb, int group)
{
        if (EXT3_HAS_RO_COMPAT_FEATURE(sb,EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
            !ext3_group_sparse(group))
                return 0;
        return 1;
}

/**
 *      ext3_bg_num_gdb - number of blocks used by the group table in group
 *      @sb: superblock for filesystem
 *      @group: group number to check
 *
 *      Return the number of blocks used by the group descriptor table
 *      (primary or backup) in this group.  In the future there may be a
 *      different number of descriptor blocks in each group.
 */
unsigned long ext3_bg_num_gdb(struct super_block *sb, int group)
{
        if (EXT3_HAS_RO_COMPAT_FEATURE(sb,EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
            !ext3_group_sparse(group))
                return 0;
        return EXT3_SB(sb)->s_gdb_count;
}

#ifdef CONFIG_EXT3_CHECK
/* Called at mount-time, super-block is locked */
void ext3_check_blocks_bitmap (struct super_block * sb)
{
        struct ext3_super_block *es;
        unsigned long desc_count, bitmap_count, x, j;
        unsigned long desc_blocks;
        struct buffer_head *bitmap_bh = NULL;
        struct ext3_group_desc *gdp;
        int i;

        es = EXT3_SB(sb)->s_es;
        desc_count = 0;
        bitmap_count = 0;
        gdp = NULL;
        for (i = 0; i < EXT3_SB(sb)->s_groups_count; i++) {
                gdp = ext3_get_group_desc (sb, i, NULL);
                if (!gdp)
                        continue;
                desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
                brelse(bitmap_bh);
                bitmap_bh = read_block_bitmap(sb, i);
                if (bitmap_bh == NULL)
                        continue;

                if (ext3_bg_has_super(sb, i) &&
                                !ext3_test_bit(0, bitmap_bh->b_data))
                        ext3_error(sb, __FUNCTION__,
                                   "Superblock in group %d is marked free", i);

                desc_blocks = ext3_bg_num_gdb(sb, i);
                for (j = 0; j < desc_blocks; j++)
                        if (!ext3_test_bit(j + 1, bitmap_bh->b_data))
                                ext3_error(sb, __FUNCTION__,
                                           "Descriptor block #%ld in group "
                                           "%d is marked free", j, i);

                if (!block_in_use (le32_to_cpu(gdp->bg_block_bitmap),
                                                sb, bitmap_bh->b_data))
                        ext3_error (sb, "ext3_check_blocks_bitmap",
                                    "Block bitmap for group %d is marked free",
                                    i);

                if (!block_in_use (le32_to_cpu(gdp->bg_inode_bitmap),
                                                sb, bitmap_bh->b_data))
                        ext3_error (sb, "ext3_check_blocks_bitmap",
                                    "Inode bitmap for group %d is marked free",
                                    i);

                for (j = 0; j < EXT3_SB(sb)->s_itb_per_group; j++)
                        if (!block_in_use (le32_to_cpu(gdp->bg_inode_table) + j,
                                                        sb, bitmap_bh->b_data))
                                ext3_error (sb, "ext3_check_blocks_bitmap",
                                            "Block #%d of the inode table in "
                                            "group %d is marked free", j, i);

                x = ext3_count_free(bitmap_bh, sb->s_blocksize);
                if (le16_to_cpu(gdp->bg_free_blocks_count) != x)
                        ext3_error (sb, "ext3_check_blocks_bitmap",
                                    "Wrong free blocks count for group %d, "
                                    "stored = %d, counted = %lu", i,
                                    le16_to_cpu(gdp->bg_free_blocks_count), x);
                bitmap_count += x;
        }
        brelse(bitmap_bh);
        if (le32_to_cpu(es->s_free_blocks_count) != bitmap_count)
                ext3_error (sb, "ext3_check_blocks_bitmap",
                        "Wrong free blocks count in super block, "
                        "stored = %lu, counted = %lu",
                        (unsigned long)le32_to_cpu(es->s_free_blocks_count),
                        bitmap_count);
}
#endif