/*
 *  linux/fs/ext2/ialloc.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)
 *
 *  BSD ufs-inspired inode and directory 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
 */

#include <linux/config.h>
#include <linux/fs.h>
#include <linux/ext2_fs.h>
#include <linux/locks.h>
#include <linux/quotaops.h>


/*
 * ialloc.c contains the inodes allocation and deallocation routines
 */

/*
 * The free inodes 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).
 */


/*
 * Read the inode allocation bitmap for a given block_group, reading
 * into the specified slot in the superblock's bitmap cache.
 *
 * Return buffer_head of bitmap on success or NULL.
 */
static struct buffer_head *read_inode_bitmap (struct super_block * sb,
                                               unsigned long block_group)
{
        struct ext2_group_desc *desc;
        struct buffer_head *bh = NULL;

        desc = ext2_get_group_desc(sb, block_group, NULL);
        if (!desc)
                goto error_out;

        bh = sb_bread(sb, le32_to_cpu(desc->bg_inode_bitmap));
        if (!bh)
                ext2_error (sb, "read_inode_bitmap",
                            "Cannot read inode bitmap - "
                            "block_group = %lu, inode_bitmap = %lu",
                            block_group, (unsigned long) desc->bg_inode_bitmap);
error_out:
        return bh;
}

/*
 * load_inode_bitmap loads the inode 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 buffer_head of the bitmap or the ERR_PTR(error)
 */
static struct buffer_head *load_inode_bitmap (struct super_block * sb,
                                              unsigned int block_group)
{
        int i, slot = 0;
        struct ext2_sb_info *sbi = &sb->u.ext2_sb;
        struct buffer_head *bh = sbi->s_inode_bitmap[0];

        if (block_group >= sbi->s_groups_count)
                ext2_panic (sb, "load_inode_bitmap",
                            "block_group >= groups_count - "
                            "block_group = %d, groups_count = %lu",
                             block_group, sbi->s_groups_count);

        if (sbi->s_loaded_inode_bitmaps > 0 &&
            sbi->s_inode_bitmap_number[0] == block_group && bh)
                goto found;

        if (sbi->s_groups_count <= EXT2_MAX_GROUP_LOADED) {
                slot = block_group;
                bh = sbi->s_inode_bitmap[slot];
                if (!bh)
                        goto read_it;
                if (sbi->s_inode_bitmap_number[slot] == slot)
                        goto found;
                ext2_panic (sb, "load_inode_bitmap",
                            "block_group != inode_bitmap_number");
        }

        bh = NULL;
        for (i = 0; i < sbi->s_loaded_inode_bitmaps &&
                    sbi->s_inode_bitmap_number[i] != block_group;
             i++)
                ;
        if (i < sbi->s_loaded_inode_bitmaps)
                bh = sbi->s_inode_bitmap[i];
        else if (sbi->s_loaded_inode_bitmaps < EXT2_MAX_GROUP_LOADED)
                sbi->s_loaded_inode_bitmaps++;
        else
                brelse (sbi->s_inode_bitmap[--i]);

        while (i--) {
                sbi->s_inode_bitmap_number[i+1] = sbi->s_inode_bitmap_number[i];
                sbi->s_inode_bitmap[i+1] = sbi->s_inode_bitmap[i];
        }

read_it:
        if (!bh)
                bh = read_inode_bitmap (sb, block_group);
        sbi->s_inode_bitmap_number[slot] = block_group;
        sbi->s_inode_bitmap[slot] = bh;
        if (!bh)
                return ERR_PTR(-EIO);
found:
        return bh;
}

/*
 * NOTE! When we get the inode, we're the only people
 * that have access to it, and as such there are no
 * race conditions we have to worry about. The inode
 * is not on the hash-lists, and it cannot be reached
 * through the filesystem because the directory entry
 * has been deleted earlier.
 *
 * HOWEVER: we must make sure that we get no aliases,
 * which means that we have to call "clear_inode()"
 * _before_ we mark the inode not in use in the inode
 * bitmaps. Otherwise a newly created file might use
 * the same inode number (not actually the same pointer
 * though), and then we'd have two inodes sharing the
 * same inode number and space on the harddisk.
 */
void ext2_free_inode (struct inode * inode)
{
        struct super_block * sb = inode->i_sb;
        int is_directory;
        unsigned long ino;
        struct buffer_head * bh;
        struct buffer_head * bh2;
        unsigned long block_group;
        unsigned long bit;
        struct ext2_group_desc * desc;
        struct ext2_super_block * es;

        ino = inode->i_ino;
        ext2_debug ("freeing inode %lu\n", ino);

        /*
         * Note: we must free any quota before locking the superblock,
         * as writing the quota to disk may need the lock as well.
         */
        if (!is_bad_inode(inode)) {
                /* Quota is already initialized in iput() */
                DQUOT_FREE_INODE(inode);
                DQUOT_DROP(inode);
        }

        lock_super (sb);
        es = sb->u.ext2_sb.s_es;
        is_directory = S_ISDIR(inode->i_mode);

        /* Do this BEFORE marking the inode not in use or returning an error */
        clear_inode (inode);

        if (ino < EXT2_FIRST_INO(sb) ||
            ino > le32_to_cpu(es->s_inodes_count)) {
                ext2_error (sb, "ext2_free_inode",
                            "reserved or nonexistent inode %lu", ino);
                goto error_return;
        }
        block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb);
        bit = (ino - 1) % EXT2_INODES_PER_GROUP(sb);
        bh = load_inode_bitmap (sb, block_group);
        if (IS_ERR(bh))
                goto error_return;

        /* Ok, now we can actually update the inode bitmaps.. */
        if (!ext2_clear_bit (bit, bh->b_data))
                ext2_error (sb, "ext2_free_inode",
                              "bit already cleared for inode %lu", ino);
        else {
                desc = ext2_get_group_desc (sb, block_group, &bh2);
                if (desc) {
                        desc->bg_free_inodes_count =
                                cpu_to_le16(le16_to_cpu(desc->bg_free_inodes_count) + 1);
                        if (is_directory)
                                desc->bg_used_dirs_count =
                                        cpu_to_le16(le16_to_cpu(desc->bg_used_dirs_count) - 1);
                }
                mark_buffer_dirty(bh2);
                es->s_free_inodes_count =
                        cpu_to_le32(le32_to_cpu(es->s_free_inodes_count) + 1);
                mark_buffer_dirty(sb->u.ext2_sb.s_sbh);
        }
        mark_buffer_dirty(bh);
        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);
}

/*
 * There are two policies for allocating an inode.  If the new inode is
 * a directory, then a forward search is made for a block group with both
 * free space and a low directory-to-inode ratio; if that fails, then of
 * the groups with above-average free space, that group with the fewest
 * directories already is chosen.
 *
 * For other inodes, search forward from the parent directory\'s block
 * group to find a free inode.
 */

static int find_group_dir(struct super_block *sb, int parent_group)
{
        struct ext2_super_block * es = sb->u.ext2_sb.s_es;
        int ngroups = sb->u.ext2_sb.s_groups_count;
        int avefreei = le32_to_cpu(es->s_free_inodes_count) / ngroups;
        struct ext2_group_desc *desc, *best_desc = NULL;
        struct buffer_head *bh, *best_bh = NULL;
        int group, best_group = -1;

        for (group = 0; group < ngroups; group++) {
                desc = ext2_get_group_desc (sb, group, &bh);
                if (!desc || !desc->bg_free_inodes_count)
                        continue;
                if (le16_to_cpu(desc->bg_free_inodes_count) < avefreei)
                        continue;
                if (!best_desc || 
                    (le16_to_cpu(desc->bg_free_blocks_count) >
                     le16_to_cpu(best_desc->bg_free_blocks_count))) {
                        best_group = group;
                        best_desc = desc;
                        best_bh = bh;
                }
        }
        if (!best_desc)
                return -1;
        best_desc->bg_free_inodes_count =
                cpu_to_le16(le16_to_cpu(best_desc->bg_free_inodes_count) - 1);
        best_desc->bg_used_dirs_count =
                cpu_to_le16(le16_to_cpu(best_desc->bg_used_dirs_count) + 1);
        mark_buffer_dirty(best_bh);
        return best_group;
}

static int find_group_other(struct super_block *sb, int parent_group)
{
        int ngroups = sb->u.ext2_sb.s_groups_count;
        struct ext2_group_desc *desc;
        struct buffer_head *bh;
        int group, i;

        /*
         * Try to place the inode in its parent directory
         */
        group = parent_group;
        desc = ext2_get_group_desc (sb, group, &bh);
        if (desc && le16_to_cpu(desc->bg_free_inodes_count))
                goto found;

        /*
         * Use a quadratic hash to find a group with a
         * free inode
         */
        for (i = 1; i < ngroups; i <<= 1) {
                group += i;
                if (group >= ngroups)
                        group -= ngroups;
                desc = ext2_get_group_desc (sb, group, &bh);
                if (desc && le16_to_cpu(desc->bg_free_inodes_count))
                        goto found;
        }

        /*
         * That failed: try linear search for a free inode
         */
        group = parent_group + 1;
        for (i = 2; i < ngroups; i++) {
                if (++group >= ngroups)
                        group = 0;
                desc = ext2_get_group_desc (sb, group, &bh);
                if (desc && le16_to_cpu(desc->bg_free_inodes_count))
                        goto found;
        }

        return -1;

found:
        desc->bg_free_inodes_count =
                cpu_to_le16(le16_to_cpu(desc->bg_free_inodes_count) - 1);
        mark_buffer_dirty(bh);
        return group;
}

struct inode * ext2_new_inode (const struct inode * dir, int mode)
{
        struct super_block * sb;
        struct buffer_head * bh;
        struct buffer_head * bh2;
        int group, i;
        ino_t ino;
        struct inode * inode;
        struct ext2_group_desc * desc;
        struct ext2_super_block * es;
        int err;

        sb = dir->i_sb;
        inode = new_inode(sb);
        if (!inode)
                return ERR_PTR(-ENOMEM);

        lock_super (sb);
        es = sb->u.ext2_sb.s_es;
repeat:
        if (S_ISDIR(mode))
                group = find_group_dir(sb, dir->u.ext2_i.i_block_group);
        else 
                group = find_group_other(sb, dir->u.ext2_i.i_block_group);

        err = -ENOSPC;
        if (group == -1)
                goto fail;

        err = -EIO;
        bh = load_inode_bitmap (sb, group);
        if (IS_ERR(bh))
                goto fail2;

        i = ext2_find_first_zero_bit ((unsigned long *) bh->b_data,
                                      EXT2_INODES_PER_GROUP(sb));
        if (i >= EXT2_INODES_PER_GROUP(sb))
                goto bad_count;
        ext2_set_bit (i, bh->b_data);

        mark_buffer_dirty(bh);
        if (sb->s_flags & MS_SYNCHRONOUS) {
                ll_rw_block (WRITE, 1, &bh);
                wait_on_buffer (bh);
        }

        ino = group * EXT2_INODES_PER_GROUP(sb) + i + 1;
        if (ino < EXT2_FIRST_INO(sb) || ino > le32_to_cpu(es->s_inodes_count)) {
                ext2_error (sb, "ext2_new_inode",
                            "reserved inode or inode > inodes count - "
                            "block_group = %d,inode=%ld", group, ino);
                err = -EIO;
                goto fail2;
        }

        es->s_free_inodes_count =
                cpu_to_le32(le32_to_cpu(es->s_free_inodes_count) - 1);
        mark_buffer_dirty(sb->u.ext2_sb.s_sbh);
        sb->s_dirt = 1;
        inode->i_uid = current->fsuid;
        if (test_opt (sb, GRPID))
                inode->i_gid = dir->i_gid;
        else if (dir->i_mode & S_ISGID) {
                inode->i_gid = dir->i_gid;
                if (S_ISDIR(mode))
                        mode |= S_ISGID;
        } else
                inode->i_gid = current->fsgid;
        inode->i_mode = mode;

        inode->i_ino = ino;
        inode->i_blksize = PAGE_SIZE;   /* This is the optimal IO size (for stat), not the fs block size */
        inode->i_blocks = 0;
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
        inode->u.ext2_i.i_state = EXT2_STATE_NEW;
        inode->u.ext2_i.i_flags = dir->u.ext2_i.i_flags & ~EXT2_BTREE_FL;
        if (S_ISLNK(mode))
                inode->u.ext2_i.i_flags &= ~(EXT2_IMMUTABLE_FL|EXT2_APPEND_FL);
        inode->u.ext2_i.i_block_group = group;
        ext2_set_inode_flags(inode);
        insert_inode_hash(inode);
        inode->i_generation = event++;
        mark_inode_dirty(inode);

        unlock_super (sb);
        if(DQUOT_ALLOC_INODE(inode)) {
                DQUOT_DROP(inode);
                inode->i_flags |= S_NOQUOTA;
                inode->i_nlink = 0;
                iput(inode);
                return ERR_PTR(-EDQUOT);
        }
        ext2_debug ("allocating inode %lu\n", inode->i_ino);
        return inode;

fail2:
        desc = ext2_get_group_desc (sb, group, &bh2);
        desc->bg_free_inodes_count =
                cpu_to_le16(le16_to_cpu(desc->bg_free_inodes_count) + 1);
        if (S_ISDIR(mode))
                desc->bg_used_dirs_count =
                        cpu_to_le16(le16_to_cpu(desc->bg_used_dirs_count) - 1);
        mark_buffer_dirty(bh2);
fail:
        unlock_super(sb);
        make_bad_inode(inode);
        iput(inode);
        return ERR_PTR(err);

bad_count:
        ext2_error (sb, "ext2_new_inode",
                    "Free inodes count corrupted in group %d",
                    group);
        /* Is it really ENOSPC? */
        err = -ENOSPC;
        if (sb->s_flags & MS_RDONLY)
                goto fail;

        desc = ext2_get_group_desc (sb, group, &bh2);
        desc->bg_free_inodes_count = 0;
        mark_buffer_dirty(bh2);
        goto repeat;
}

unsigned long ext2_count_free_inodes (struct super_block * sb)
{
#ifdef EXT2FS_DEBUG
        struct ext2_super_block * es;
        unsigned long desc_count = 0, bitmap_count = 0;
        int i;

        lock_super (sb);
        es = sb->u.ext2_sb.s_es;
        for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++) {
                struct ext2_group_desc *desc = ext2_get_group_desc (sb, i, NULL);
                struct buffer_head *bh;
                unsigned x;

                if (!desc)
                        continue;
                desc_count += le16_to_cpu(desc->bg_free_inodes_count);
                bh = load_inode_bitmap (sb, i);
                if (IS_ERR(bh))
                        continue;

                x = ext2_count_free (bh, EXT2_INODES_PER_GROUP(sb) / 8);
                printk ("group %d: stored = %d, counted = %lu\n",
                        i, le16_to_cpu(desc->bg_free_inodes_count), x);
                bitmap_count += x;
        }
        printk("ext2_count_free_inodes: stored = %lu, computed = %lu, %lu\n",
                le32_to_cpu(es->s_free_inodes_count), desc_count, bitmap_count);
        unlock_super (sb);
        return desc_count;
#else
        return le32_to_cpu(sb->u.ext2_sb.s_es->s_free_inodes_count);
#endif
}

#ifdef CONFIG_EXT2_CHECK
/* Called at mount-time, super-block is locked */
void ext2_check_inodes_bitmap (struct super_block * sb)
{
        struct ext2_super_block * es = sb->u.ext2_sb.s_es;
        unsigned long desc_count = 0, bitmap_count = 0;
        int i;

        for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++) {
                struct ext2_group_desc *desc = ext2_get_group_desc(sb, i, NULL);
                struct buffer_head *bh;
                unsigned x;

                if (!desc)
                        continue;
                desc_count += le16_to_cpu(desc->bg_free_inodes_count);
                bh = load_inode_bitmap (sb, i);
                if (IS_ERR(bh))
                        continue;
                
                x = ext2_count_free (bh, EXT2_INODES_PER_GROUP(sb) / 8);
                if (le16_to_cpu(desc->bg_free_inodes_count) != x)
                        ext2_error (sb, "ext2_check_inodes_bitmap",
                                    "Wrong free inodes count in group %d, "
                                    "stored = %d, counted = %lu", i,
                                    le16_to_cpu(desc->bg_free_inodes_count), x);
                bitmap_count += x;
        }
        if (le32_to_cpu(es->s_free_inodes_count) != bitmap_count)
                ext2_error (sb, "ext2_check_inodes_bitmap",
                            "Wrong free inodes count in super block, "
                            "stored = %lu, counted = %lu",
                            (unsigned long)le32_to_cpu(es->s_free_inodes_count),
                            bitmap_count);
}
#endif