ext2/ext3/ext4: add block bitmap validation

[linux-2.6/kvm.git] / fs / ext2 / balloc.c

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

#include "ext2.h"
#include <linux/quotaops.h>
#include <linux/sched.h>
#include <linux/buffer_head.h>
#include <linux/capability.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 ext2_fill_super).
 */


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

struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
                                             unsigned int block_group,
                                             struct buffer_head ** bh)
{
        unsigned long group_desc;
        unsigned long offset;
        struct ext2_group_desc * desc;
        struct ext2_sb_info *sbi = EXT2_SB(sb);

        if (block_group >= sbi->s_groups_count) {
                ext2_error (sb, "ext2_get_group_desc",
                            "block_group >= groups_count - "
                            "block_group = %d, groups_count = %lu",
                            block_group, sbi->s_groups_count);

                return NULL;
        }

        group_desc = block_group >> EXT2_DESC_PER_BLOCK_BITS(sb);
        offset = block_group & (EXT2_DESC_PER_BLOCK(sb) - 1);
        if (!sbi->s_group_desc[group_desc]) {
                ext2_error (sb, "ext2_get_group_desc",
                            "Group descriptor not loaded - "
                            "block_group = %d, group_desc = %lu, desc = %lu",
                             block_group, group_desc, offset);
                return NULL;
        }

        desc = (struct ext2_group_desc *) sbi->s_group_desc[group_desc]->b_data;
        if (bh)
                *bh = sbi->s_group_desc[group_desc];
        return desc + offset;
}

static inline int
block_in_use(unsigned long block, struct super_block *sb, unsigned char *map)
{
        return ext2_test_bit ((block -
                le32_to_cpu(EXT2_SB(sb)->s_es->s_first_data_block)) %
                         EXT2_BLOCKS_PER_GROUP(sb), map);
}

/*
 * 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)
{
        int i;
        struct ext2_group_desc * desc;
        struct buffer_head * bh = NULL;
        unsigned int bitmap_blk;

        desc = ext2_get_group_desc (sb, block_group, NULL);
        if (!desc)
                return NULL;
        bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
        bh = sb_bread(sb, bitmap_blk);
        if (!bh)
                ext2_error (sb, __FUNCTION__,
                            "Cannot read block bitmap - "
                            "block_group = %d, block_bitmap = %u",
                            block_group, le32_to_cpu(desc->bg_block_bitmap));

        /* check whether block bitmap block number is set */
        if (!block_in_use(bitmap_blk, sb, bh->b_data)) {
                /* bad block bitmap */
                goto error_out;
        }
        /* check whether the inode bitmap block number is set */
        bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
        if (!block_in_use(bitmap_blk, sb, bh->b_data)) {
                /* bad block bitmap */
                goto error_out;
        }
        /* check whether the inode table block number is set */
        bitmap_blk = le32_to_cpu(desc->bg_inode_table);
        for (i = 0; i < EXT2_SB(sb)->s_itb_per_group; i++, bitmap_blk++) {
                if (!block_in_use(bitmap_blk, sb, bh->b_data)) {
                        /* bad block bitmap */
                        goto error_out;
                }
        }

        return bh;

error_out:
        brelse(bh);
        ext2_error(sb, __FUNCTION__,
                        "Invalid block bitmap - "
                        "block_group = %d, block = %u",
                        block_group, bitmap_blk);
        return NULL;
}

/*
 * Set sb->s_dirt here because the superblock was "logically" altered.  We
 * need to recalculate its free blocks count and flush it out.
 */
static int reserve_blocks(struct super_block *sb, int count)
{
        struct ext2_sb_info *sbi = EXT2_SB(sb);
        struct ext2_super_block *es = sbi->s_es;
        unsigned free_blocks;
        unsigned root_blocks;

        free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
        root_blocks = le32_to_cpu(es->s_r_blocks_count);

        if (free_blocks < count)
                count = free_blocks;

        if (free_blocks < root_blocks + count && !capable(CAP_SYS_RESOURCE) &&
            sbi->s_resuid != current->fsuid &&
            (sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
                /*
                 * We are too close to reserve and we are not privileged.
                 * Can we allocate anything at all?
                 */
                if (free_blocks > root_blocks)
                        count = free_blocks - root_blocks;
                else
                        return 0;
        }

        percpu_counter_sub(&sbi->s_freeblocks_counter, count);
        sb->s_dirt = 1;
        return count;
}

static void release_blocks(struct super_block *sb, int count)
{
        if (count) {
                struct ext2_sb_info *sbi = EXT2_SB(sb);

                percpu_counter_add(&sbi->s_freeblocks_counter, count);
                sb->s_dirt = 1;
        }
}

static int group_reserve_blocks(struct ext2_sb_info *sbi, int group_no,
        struct ext2_group_desc *desc, struct buffer_head *bh, int count)
{
        unsigned free_blocks;

        if (!desc->bg_free_blocks_count)
                return 0;

        spin_lock(sb_bgl_lock(sbi, group_no));
        free_blocks = le16_to_cpu(desc->bg_free_blocks_count);
        if (free_blocks < count)
                count = free_blocks;
        desc->bg_free_blocks_count = cpu_to_le16(free_blocks - count);
        spin_unlock(sb_bgl_lock(sbi, group_no));
        mark_buffer_dirty(bh);
        return count;
}

static void group_release_blocks(struct super_block *sb, int group_no,
        struct ext2_group_desc *desc, struct buffer_head *bh, int count)
{
        if (count) {
                struct ext2_sb_info *sbi = EXT2_SB(sb);
                unsigned free_blocks;

                spin_lock(sb_bgl_lock(sbi, group_no));
                free_blocks = le16_to_cpu(desc->bg_free_blocks_count);
                desc->bg_free_blocks_count = cpu_to_le16(free_blocks + count);
                spin_unlock(sb_bgl_lock(sbi, group_no));
                sb->s_dirt = 1;
                mark_buffer_dirty(bh);
        }
}

/* Free given blocks, update quota and i_blocks field */
void ext2_free_blocks (struct inode * inode, unsigned long block,
                       unsigned long count)
{
        struct buffer_head *bitmap_bh = NULL;
        struct buffer_head * bh2;
        unsigned long block_group;
        unsigned long bit;
        unsigned long i;
        unsigned long overflow;
        struct super_block * sb = inode->i_sb;
        struct ext2_sb_info * sbi = EXT2_SB(sb);
        struct ext2_group_desc * desc;
        struct ext2_super_block * es = sbi->s_es;
        unsigned freed = 0, group_freed;

        if (block < le32_to_cpu(es->s_first_data_block) ||
            block + count < block ||
            block + count > le32_to_cpu(es->s_blocks_count)) {
                ext2_error (sb, "ext2_free_blocks",
                            "Freeing blocks not in datazone - "
                            "block = %lu, count = %lu", block, count);
                goto error_return;
        }

        ext2_debug ("freeing block(s) %lu-%lu\n", block, block + count - 1);

do_more:
        overflow = 0;
        block_group = (block - le32_to_cpu(es->s_first_data_block)) /
                      EXT2_BLOCKS_PER_GROUP(sb);
        bit = (block - le32_to_cpu(es->s_first_data_block)) %
                      EXT2_BLOCKS_PER_GROUP(sb);
        /*
         * Check to see if we are freeing blocks across a group
         * boundary.
         */
        if (bit + count > EXT2_BLOCKS_PER_GROUP(sb)) {
                overflow = bit + count - EXT2_BLOCKS_PER_GROUP(sb);
                count -= overflow;
        }
        brelse(bitmap_bh);
        bitmap_bh = read_block_bitmap(sb, block_group);
        if (!bitmap_bh)
                goto error_return;

        desc = ext2_get_group_desc (sb, block_group, &bh2);
        if (!desc)
                goto error_return;

        if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
            in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
            in_range (block, le32_to_cpu(desc->bg_inode_table),
                      sbi->s_itb_per_group) ||
            in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table),
                      sbi->s_itb_per_group))
                ext2_error (sb, "ext2_free_blocks",
                            "Freeing blocks in system zones - "
                            "Block = %lu, count = %lu",
                            block, count);

        for (i = 0, group_freed = 0; i < count; i++) {
                if (!ext2_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
                                                bit + i, bitmap_bh->b_data)) {
                        ext2_error(sb, __FUNCTION__,
                                "bit already cleared for block %lu", block + i);
                } else {
                        group_freed++;
                }
        }

        mark_buffer_dirty(bitmap_bh);
        if (sb->s_flags & MS_SYNCHRONOUS)
                sync_dirty_buffer(bitmap_bh);

        group_release_blocks(sb, block_group, desc, bh2, group_freed);
        freed += group_freed;

        if (overflow) {
                block += count;
                count = overflow;
                goto do_more;
        }
error_return:
        brelse(bitmap_bh);
        release_blocks(sb, freed);
        DQUOT_FREE_BLOCK(inode, freed);
}

static int grab_block(spinlock_t *lock, char *map, unsigned size, int goal)
{
        int k;
        char *p, *r;

        if (!ext2_test_bit(goal, map))
                goto got_it;

repeat:
        if (goal) {
                /*
                 * 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..
                 */
                k = (goal + 63) & ~63;
                goal = ext2_find_next_zero_bit(map, k, goal);
                if (goal < k)
                        goto got_it;
                /*
                 * Search in the remainder of the current group.
                 */
        }

        p = map + (goal >> 3);
        r = memscan(p, 0, (size - goal + 7) >> 3);
        k = (r - map) << 3;
        if (k < size) {
                /* 
                 * We have succeeded in finding a free byte in the block
                 * bitmap.  Now search backwards to find the start of this
                 * group of free blocks - won't take more than 7 iterations.
                 */
                for (goal = k; goal && !ext2_test_bit (goal - 1, map); goal--)
                        ;
                goto got_it;
        }

        k = ext2_find_next_zero_bit ((u32 *)map, size, goal);
        if (k < size) {
                goal = k;
                goto got_it;
        }
        return -1;
got_it:
        if (ext2_set_bit_atomic(lock, goal, (void *) map)) 
                goto repeat;    
        return goal;
}

/*
 * 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.
 * This function also updates quota and i_blocks field.
 */
int ext2_new_block(struct inode *inode, unsigned long goal,
                        u32 *prealloc_count, u32 *prealloc_block, int *err)
{
        struct buffer_head *bitmap_bh = NULL;
        struct buffer_head *gdp_bh;     /* bh2 */
        struct ext2_group_desc *desc;
        int group_no;                   /* i */
        int ret_block;                  /* j */
        int group_idx;                  /* k */
        int target_block;               /* tmp */
        int block = 0;
        struct super_block *sb = inode->i_sb;
        struct ext2_sb_info *sbi = EXT2_SB(sb);
        struct ext2_super_block *es = sbi->s_es;
        unsigned group_size = EXT2_BLOCKS_PER_GROUP(sb);
        unsigned prealloc_goal = es->s_prealloc_blocks;
        unsigned group_alloc = 0, es_alloc, dq_alloc;
        int nr_scanned_groups;

        if (!prealloc_goal--)
                prealloc_goal = EXT2_DEFAULT_PREALLOC_BLOCKS - 1;
        if (!prealloc_count || *prealloc_count)
                prealloc_goal = 0;

        if (DQUOT_ALLOC_BLOCK(inode, 1)) {
                *err = -EDQUOT;
                goto out;
        }

        while (prealloc_goal && DQUOT_PREALLOC_BLOCK(inode, prealloc_goal))
                prealloc_goal--;

        dq_alloc = prealloc_goal + 1;
        es_alloc = reserve_blocks(sb, dq_alloc);
        if (!es_alloc) {
                *err = -ENOSPC;
                goto out_dquot;
        }

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

        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)) / group_size;
        desc = ext2_get_group_desc (sb, group_no, &gdp_bh);
        if (!desc) {
                /*
                 * gdp_bh may still be uninitialised.  But group_release_blocks
                 * will not touch it because group_alloc is zero.
                 */
                goto io_error;
        }

        group_alloc = group_reserve_blocks(sbi, group_no, desc,
                                        gdp_bh, es_alloc);
        if (group_alloc) {
                ret_block = ((goal - le32_to_cpu(es->s_first_data_block)) %
                                        group_size);
                brelse(bitmap_bh);
                bitmap_bh = read_block_bitmap(sb, group_no);
                if (!bitmap_bh)
                        goto io_error;
                
                ext2_debug("goal is at %d:%d.\n", group_no, ret_block);

                ret_block = grab_block(sb_bgl_lock(sbi, group_no),
                                bitmap_bh->b_data, group_size, ret_block);
                if (ret_block >= 0)
                        goto got_block;
                group_release_blocks(sb, group_no, desc, gdp_bh, group_alloc);
                group_alloc = 0;
        }

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

        /*
         * Now search the rest of the groups.  We assume that 
         * i and desc correctly point to the last group visited.
         */
        nr_scanned_groups = 0;
retry:
        for (group_idx = 0; !group_alloc &&
                        group_idx < sbi->s_groups_count; group_idx++) {
                group_no++;
                if (group_no >= sbi->s_groups_count)
                        group_no = 0;
                desc = ext2_get_group_desc(sb, group_no, &gdp_bh);
                if (!desc)
                        goto io_error;
                group_alloc = group_reserve_blocks(sbi, group_no, desc,
                                                gdp_bh, es_alloc);
        }
        if (!group_alloc) {
                *err = -ENOSPC;
                goto out_release;
        }
        brelse(bitmap_bh);
        bitmap_bh = read_block_bitmap(sb, group_no);
        if (!bitmap_bh)
                goto io_error;

        ret_block = grab_block(sb_bgl_lock(sbi, group_no), bitmap_bh->b_data,
                                group_size, 0);
        if (ret_block < 0) {
                /*
                 * If a free block counter is corrupted we can loop inifintely.
                 * Detect that here.
                 */
                nr_scanned_groups++;
                if (nr_scanned_groups > 2 * sbi->s_groups_count) {
                        ext2_error(sb, "ext2_new_block",
                                "corrupted free blocks counters");
                        goto io_error;
                }
                /*
                 * Someone else grabbed the last free block in this blockgroup
                 * before us.  Retry the scan.
                 */
                group_release_blocks(sb, group_no, desc, gdp_bh, group_alloc);
                group_alloc = 0;
                goto retry;
        }

got_block:
        ext2_debug("using block group %d(%d)\n",
                group_no, desc->bg_free_blocks_count);

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

        if (target_block == le32_to_cpu(desc->bg_block_bitmap) ||
            target_block == le32_to_cpu(desc->bg_inode_bitmap) ||
            in_range(target_block, le32_to_cpu(desc->bg_inode_table),
                      sbi->s_itb_per_group))
                ext2_error (sb, "ext2_new_block",
                            "Allocating block in system zone - "
                            "block = %u", target_block);

        if (target_block >= le32_to_cpu(es->s_blocks_count)) {
                ext2_error (sb, "ext2_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 io_error;
        }
        block = target_block;

        /* OK, we _had_ allocated something */
        ext2_debug("found bit %d\n", ret_block);

        dq_alloc--;
        es_alloc--;
        group_alloc--;

        /*
         * Do block preallocation now if required.
         */
        write_lock(&EXT2_I(inode)->i_meta_lock);
        if (group_alloc && !*prealloc_count) {
                unsigned n;

                for (n = 0; n < group_alloc && ++ret_block < group_size; n++) {
                        if (ext2_set_bit_atomic(sb_bgl_lock(sbi, group_no),
                                                ret_block,
                                                (void*) bitmap_bh->b_data))
                                break;
                }
                *prealloc_block = block + 1;
                *prealloc_count = n;
                es_alloc -= n;
                dq_alloc -= n;
                group_alloc -= n;
        }
        write_unlock(&EXT2_I(inode)->i_meta_lock);

        mark_buffer_dirty(bitmap_bh);
        if (sb->s_flags & MS_SYNCHRONOUS)
                sync_dirty_buffer(bitmap_bh);

        ext2_debug ("allocating block %d. ", block);

        *err = 0;
out_release:
        group_release_blocks(sb, group_no, desc, gdp_bh, group_alloc);
        release_blocks(sb, es_alloc);
out_dquot:
        DQUOT_FREE_BLOCK(inode, dq_alloc);
out:
        brelse(bitmap_bh);
        return block;

io_error:
        *err = -EIO;
        goto out_release;
}

#ifdef EXT2FS_DEBUG

static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};

unsigned long ext2_count_free (struct buffer_head * map, unsigned int numchars)
{
        unsigned int i;
        unsigned long sum = 0;

        if (!map)
                return (0);
        for (i = 0; i < numchars; i++)
                sum += nibblemap[map->b_data[i] & 0xf] +
                        nibblemap[(map->b_data[i] >> 4) & 0xf];
        return (sum);
}

#endif  /*  EXT2FS_DEBUG  */

unsigned long ext2_count_free_blocks (struct super_block * sb)
{
        struct ext2_group_desc * desc;
        unsigned long desc_count = 0;
        int i;
#ifdef EXT2FS_DEBUG
        unsigned long bitmap_count, x;
        struct ext2_super_block *es;

        es = EXT2_SB(sb)->s_es;
        desc_count = 0;
        bitmap_count = 0;
        desc = NULL;
        for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
                struct buffer_head *bitmap_bh;
                desc = ext2_get_group_desc (sb, i, NULL);
                if (!desc)
                        continue;
                desc_count += le16_to_cpu(desc->bg_free_blocks_count);
                bitmap_bh = read_block_bitmap(sb, i);
                if (!bitmap_bh)
                        continue;
                
                x = ext2_count_free(bitmap_bh, sb->s_blocksize);
                printk ("group %d: stored = %d, counted = %lu\n",
                        i, le16_to_cpu(desc->bg_free_blocks_count), x);
                bitmap_count += x;
                brelse(bitmap_bh);
        }
        printk("ext2_count_free_blocks: stored = %lu, computed = %lu, %lu\n",
                (long)le32_to_cpu(es->s_free_blocks_count),
                desc_count, bitmap_count);
        return bitmap_count;
#else
        for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
                desc = ext2_get_group_desc (sb, i, NULL);
                if (!desc)
                        continue;
                desc_count += le16_to_cpu(desc->bg_free_blocks_count);
        }
        return desc_count;
#endif
}


static inline int test_root(int a, int b)
{
        int num = b;

        while (a > num)
                num *= b;
        return num == a;
}

static int ext2_group_sparse(int group)
{
        if (group <= 1)
                return 1;
        return (test_root(group, 3) || test_root(group, 5) ||
                test_root(group, 7));
}

/**
 *      ext2_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 ext2_bg_has_super(struct super_block *sb, int group)
{
        if (EXT2_HAS_RO_COMPAT_FEATURE(sb,EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
            !ext2_group_sparse(group))
                return 0;
        return 1;
}

/**
 *      ext2_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 ext2_bg_num_gdb(struct super_block *sb, int group)
{
        if (EXT2_HAS_RO_COMPAT_FEATURE(sb,EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
            !ext2_group_sparse(group))
                return 0;
        return EXT2_SB(sb)->s_gdb_count;
}