/*
 *  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/quotaops.h>
#include <linux/sched.h>
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/random.h>
#include "ext2.h"
#include "xattr.h"
#include "acl.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.
 */


/*
 * 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 = %u",
                            block_group, le32_to_cpu(desc->bg_inode_bitmap));
error_out:
        return bh;
}

static void ext2_release_inode(struct super_block *sb, int group, int dir)
{
        struct ext2_group_desc * desc;
        struct buffer_head *bh;

        desc = ext2_get_group_desc(sb, group, &bh);
        if (!desc) {
                ext2_error(sb, "ext2_release_inode",
                        "can't get descriptor for group %d", group);
                return;
        }

        spin_lock(sb_bgl_lock(EXT2_SB(sb), group));
        desc->bg_free_inodes_count =
                cpu_to_le16(le16_to_cpu(desc->bg_free_inodes_count) + 1);
        if (dir)
                desc->bg_used_dirs_count =
                        cpu_to_le16(le16_to_cpu(desc->bg_used_dirs_count) - 1);
        spin_unlock(sb_bgl_lock(EXT2_SB(sb), group));
        if (dir)
                percpu_counter_dec(&EXT2_SB(sb)->s_dirs_counter);
        sb->s_dirt = 1;
        mark_buffer_dirty(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 *bitmap_bh = NULL;
        unsigned long block_group;
        unsigned long bit;
        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() */
                ext2_xattr_delete_inode(inode);
                DQUOT_FREE_INODE(inode);
                DQUOT_DROP(inode);
        }

        es = EXT2_SB(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);
        brelse(bitmap_bh);
        bitmap_bh = read_inode_bitmap(sb, block_group);
        if (!bitmap_bh)
                goto error_return;

        /* Ok, now we can actually update the inode bitmaps.. */
        if (!ext2_clear_bit_atomic(sb_bgl_lock(EXT2_SB(sb), block_group),
                                bit, (void *) bitmap_bh->b_data))
                ext2_error (sb, "ext2_free_inode",
                              "bit already cleared for inode %lu", ino);
        else
                ext2_release_inode(sb, block_group, is_directory);
        mark_buffer_dirty(bitmap_bh);
        if (sb->s_flags & MS_SYNCHRONOUS)
                sync_dirty_buffer(bitmap_bh);
error_return:
        brelse(bitmap_bh);
}

/*
 * We perform asynchronous prereading of the new inode's inode block when
 * we create the inode, in the expectation that the inode will be written
 * back soon.  There are two reasons:
 *
 * - When creating a large number of files, the async prereads will be
 *   nicely merged into large reads
 * - When writing out a large number of inodes, we don't need to keep on
 *   stalling the writes while we read the inode block.
 *
 * FIXME: ext2_get_group_desc() needs to be simplified.
 */
static void ext2_preread_inode(struct inode *inode)
{
        unsigned long block_group;
        unsigned long offset;
        unsigned long block;
        struct ext2_group_desc * gdp;
        struct backing_dev_info *bdi;

        bdi = inode->i_mapping->backing_dev_info;
        if (bdi_read_congested(bdi))
                return;
        if (bdi_write_congested(bdi))
                return;

        block_group = (inode->i_ino - 1) / EXT2_INODES_PER_GROUP(inode->i_sb);
        gdp = ext2_get_group_desc(inode->i_sb, block_group, NULL);
        if (gdp == NULL)
                return;

        /*
         * Figure out the offset within the block group inode table
         */
        offset = ((inode->i_ino - 1) % EXT2_INODES_PER_GROUP(inode->i_sb)) *
                                EXT2_INODE_SIZE(inode->i_sb);
        block = le32_to_cpu(gdp->bg_inode_table) +
                                (offset >> EXT2_BLOCK_SIZE_BITS(inode->i_sb));
        sb_breadahead(inode->i_sb, block);
}

/*
 * 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, struct inode *parent)
{
        int ngroups = EXT2_SB(sb)->s_groups_count;
        int avefreei = ext2_count_free_inodes(sb) / ngroups;
        struct ext2_group_desc *desc, *best_desc = NULL;
        int group, best_group = -1;

        for (group = 0; group < ngroups; group++) {
                desc = ext2_get_group_desc (sb, group, NULL);
                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;
                }
        }
        if (!best_desc)
                return -1;

        return best_group;
}

/* 
 * Orlov's allocator for directories. 
 * 
 * We always try to spread first-level directories.
 *
 * If there are blockgroups with both free inodes and free blocks counts 
 * not worse than average we return one with smallest directory count. 
 * Otherwise we simply return a random group. 
 * 
 * For the rest rules look so: 
 * 
 * It's OK to put directory into a group unless 
 * it has too many directories already (max_dirs) or 
 * it has too few free inodes left (min_inodes) or 
 * it has too few free blocks left (min_blocks) or 
 * it's already running too large debt (max_debt). 
 * Parent's group is prefered, if it doesn't satisfy these 
 * conditions we search cyclically through the rest. If none 
 * of the groups look good we just look for a group with more 
 * free inodes than average (starting at parent's group). 
 * 
 * Debt is incremented each time we allocate a directory and decremented 
 * when we allocate an inode, within 0--255. 
 */ 

#define INODE_COST 64
#define BLOCK_COST 256

static int find_group_orlov(struct super_block *sb, struct inode *parent)
{
        int parent_group = EXT2_I(parent)->i_block_group;
        struct ext2_sb_info *sbi = EXT2_SB(sb);
        struct ext2_super_block *es = sbi->s_es;
        int ngroups = sbi->s_groups_count;
        int inodes_per_group = EXT2_INODES_PER_GROUP(sb);
        int freei;
        int avefreei;
        int free_blocks;
        int avefreeb;
        int blocks_per_dir;
        int ndirs;
        int max_debt, max_dirs, min_blocks, min_inodes;
        int group = -1, i;
        struct ext2_group_desc *desc;

        freei = percpu_counter_read_positive(&sbi->s_freeinodes_counter);
        avefreei = freei / ngroups;
        free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
        avefreeb = free_blocks / ngroups;
        ndirs = percpu_counter_read_positive(&sbi->s_dirs_counter);

        if ((parent == sb->s_root->d_inode) ||
            (EXT2_I(parent)->i_flags & EXT2_TOPDIR_FL)) {
                struct ext2_group_desc *best_desc = NULL;
                int best_ndir = inodes_per_group;
                int best_group = -1;

                get_random_bytes(&group, sizeof(group));
                parent_group = (unsigned)group % ngroups;
                for (i = 0; i < ngroups; i++) {
                        group = (parent_group + i) % ngroups;
                        desc = ext2_get_group_desc (sb, group, NULL);
                        if (!desc || !desc->bg_free_inodes_count)
                                continue;
                        if (le16_to_cpu(desc->bg_used_dirs_count) >= best_ndir)
                                continue;
                        if (le16_to_cpu(desc->bg_free_inodes_count) < avefreei)
                                continue;
                        if (le16_to_cpu(desc->bg_free_blocks_count) < avefreeb)
                                continue;
                        best_group = group;
                        best_ndir = le16_to_cpu(desc->bg_used_dirs_count);
                        best_desc = desc;
                }
                if (best_group >= 0) {
                        desc = best_desc;
                        group = best_group;
                        goto found;
                }
                goto fallback;
        }

        if (ndirs == 0)
                ndirs = 1;      /* percpu_counters are approximate... */

        blocks_per_dir = (le32_to_cpu(es->s_blocks_count)-free_blocks) / ndirs;

        max_dirs = ndirs / ngroups + inodes_per_group / 16;
        min_inodes = avefreei - inodes_per_group / 4;
        min_blocks = avefreeb - EXT2_BLOCKS_PER_GROUP(sb) / 4;

        max_debt = EXT2_BLOCKS_PER_GROUP(sb) / max(blocks_per_dir, BLOCK_COST);
        if (max_debt * INODE_COST > inodes_per_group)
                max_debt = inodes_per_group / INODE_COST;
        if (max_debt > 255)
                max_debt = 255;
        if (max_debt == 0)
                max_debt = 1;

        for (i = 0; i < ngroups; i++) {
                group = (parent_group + i) % ngroups;
                desc = ext2_get_group_desc (sb, group, NULL);
                if (!desc || !desc->bg_free_inodes_count)
                        continue;
                if (sbi->s_debts[group] >= max_debt)
                        continue;
                if (le16_to_cpu(desc->bg_used_dirs_count) >= max_dirs)
                        continue;
                if (le16_to_cpu(desc->bg_free_inodes_count) < min_inodes)
                        continue;
                if (le16_to_cpu(desc->bg_free_blocks_count) < min_blocks)
                        continue;
                goto found;
        }

fallback:
        for (i = 0; i < ngroups; i++) {
                group = (parent_group + i) % ngroups;
                desc = ext2_get_group_desc (sb, group, NULL);
                if (!desc || !desc->bg_free_inodes_count)
                        continue;
                if (le16_to_cpu(desc->bg_free_inodes_count) >= avefreei)
                        goto found;
        }

        if (avefreei) {
                /*
                 * The free-inodes counter is approximate, and for really small
                 * filesystems the above test can fail to find any blockgroups
                 */
                avefreei = 0;
                goto fallback;
        }

        return -1;

found:
        return group;
}

static int find_group_other(struct super_block *sb, struct inode *parent)
{
        int parent_group = EXT2_I(parent)->i_block_group;
        int ngroups = EXT2_SB(sb)->s_groups_count;
        struct ext2_group_desc *desc;
        int group, i;

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

        /*
         * We're going to place this inode in a different blockgroup from its
         * parent.  We want to cause files in a common directory to all land in
         * the same blockgroup.  But we want files which are in a different
         * directory which shares a blockgroup with our parent to land in a
         * different blockgroup.
         *
         * So add our directory's i_ino into the starting point for the hash.
         */
        group = (group + parent->i_ino) % ngroups;

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

        /*
         * That failed: try linear search for a free inode, even if that group
         * has no free blocks.
         */
        group = parent_group;
        for (i = 0; i < ngroups; i++) {
                if (++group >= ngroups)
                        group = 0;
                desc = ext2_get_group_desc (sb, group, NULL);
                if (desc && le16_to_cpu(desc->bg_free_inodes_count))
                        goto found;
        }

        return -1;

found:
        return group;
}

struct inode *ext2_new_inode(struct inode *dir, int mode)
{
        struct super_block *sb;
        struct buffer_head *bitmap_bh = NULL;
        struct buffer_head *bh2;
        int group, i;
        ino_t ino = 0;
        struct inode * inode;
        struct ext2_group_desc *gdp;
        struct ext2_super_block *es;
        struct ext2_inode_info *ei;
        struct ext2_sb_info *sbi;
        int err;

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

        ei = EXT2_I(inode);
        sbi = EXT2_SB(sb);
        es = sbi->s_es;
        if (S_ISDIR(mode)) {
                if (test_opt(sb, OLDALLOC))
                        group = find_group_dir(sb, dir);
                else
                        group = find_group_orlov(sb, dir);
        } else 
                group = find_group_other(sb, dir);

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

        for (i = 0; i < sbi->s_groups_count; i++) {
                gdp = ext2_get_group_desc(sb, group, &bh2);
                brelse(bitmap_bh);
                bitmap_bh = read_inode_bitmap(sb, group);
                if (!bitmap_bh) {
                        err = -EIO;
                        goto fail;
                }
                ino = 0;

repeat_in_this_group:
                ino = ext2_find_next_zero_bit((unsigned long *)bitmap_bh->b_data,
                                              EXT2_INODES_PER_GROUP(sb), ino);
                if (ino >= EXT2_INODES_PER_GROUP(sb)) {
                        /*
                         * Rare race: find_group_xx() decided that there were
                         * free inodes in this group, but by the time we tried
                         * to allocate one, they're all gone.  This can also
                         * occur because the counters which find_group_orlov()
                         * uses are approximate.  So just go and search the
                         * next block group.
                         */
                        if (++group == sbi->s_groups_count)
                                group = 0;
                        continue;
                }
                if (ext2_set_bit_atomic(sb_bgl_lock(sbi, group),
                                                ino, bitmap_bh->b_data)) {
                        /* we lost this inode */
                        if (++ino >= EXT2_INODES_PER_GROUP(sb)) {
                                /* this group is exhausted, try next group */
                                if (++group == sbi->s_groups_count)
                                        group = 0;
                                continue;
                        }
                        /* try to find free inode in the same group */
                        goto repeat_in_this_group;
                }
                goto got;
        }

        /*
         * Scanned all blockgroups.
         */
        err = -ENOSPC;
        goto fail;
got:
        mark_buffer_dirty(bitmap_bh);
        if (sb->s_flags & MS_SYNCHRONOUS)
                sync_dirty_buffer(bitmap_bh);
        brelse(bitmap_bh);

        ino += group * EXT2_INODES_PER_GROUP(sb) + 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=%lu", group,
                            (unsigned long) ino);
                err = -EIO;
                goto fail;
        }

        percpu_counter_add(&sbi->s_freeinodes_counter, -1);
        if (S_ISDIR(mode))
                percpu_counter_inc(&sbi->s_dirs_counter);

        spin_lock(sb_bgl_lock(sbi, group));
        gdp->bg_free_inodes_count =
                cpu_to_le16(le16_to_cpu(gdp->bg_free_inodes_count) - 1);
        if (S_ISDIR(mode)) {
                if (sbi->s_debts[group] < 255)
                        sbi->s_debts[group]++;
                gdp->bg_used_dirs_count =
                        cpu_to_le16(le16_to_cpu(gdp->bg_used_dirs_count) + 1);
        } else {
                if (sbi->s_debts[group])
                        sbi->s_debts[group]--;
        }
        spin_unlock(sb_bgl_lock(sbi, group));

        sb->s_dirt = 1;
        mark_buffer_dirty(bh2);
        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_blocks = 0;
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME_SEC;
        memset(ei->i_data, 0, sizeof(ei->i_data));
        ei->i_flags = EXT2_I(dir)->i_flags & ~EXT2_BTREE_FL;
        if (S_ISLNK(mode))
                ei->i_flags &= ~(EXT2_IMMUTABLE_FL|EXT2_APPEND_FL);
        /* dirsync is only applied to directories */
        if (!S_ISDIR(mode))
                ei->i_flags &= ~EXT2_DIRSYNC_FL;
        ei->i_faddr = 0;
        ei->i_frag_no = 0;
        ei->i_frag_size = 0;
        ei->i_file_acl = 0;
        ei->i_dir_acl = 0;
        ei->i_dtime = 0;
        ei->i_block_alloc_info = NULL;
        ei->i_block_group = group;
        ei->i_dir_start_lookup = 0;
        ei->i_state = EXT2_STATE_NEW;
        ext2_set_inode_flags(inode);
        spin_lock(&sbi->s_next_gen_lock);
        inode->i_generation = sbi->s_next_generation++;
        spin_unlock(&sbi->s_next_gen_lock);
        insert_inode_hash(inode);

        if (DQUOT_ALLOC_INODE(inode)) {
                err = -EDQUOT;
                goto fail_drop;
        }

        err = ext2_init_acl(inode, dir);
        if (err)
                goto fail_free_drop;

        err = ext2_init_security(inode,dir);
        if (err)
                goto fail_free_drop;

        mark_inode_dirty(inode);
        ext2_debug("allocating inode %lu\n", inode->i_ino);
        ext2_preread_inode(inode);
        return inode;

fail_free_drop:
        DQUOT_FREE_INODE(inode);

fail_drop:
        DQUOT_DROP(inode);
        inode->i_flags |= S_NOQUOTA;
        inode->i_nlink = 0;
        iput(inode);
        return ERR_PTR(err);

fail:
        make_bad_inode(inode);
        iput(inode);
        return ERR_PTR(err);
}

unsigned long ext2_count_free_inodes (struct super_block * sb)
{
        struct ext2_group_desc *desc;
        unsigned long desc_count = 0;
        int i;  

#ifdef EXT2FS_DEBUG
        struct ext2_super_block *es;
        unsigned long bitmap_count = 0;
        struct buffer_head *bitmap_bh = NULL;

        es = EXT2_SB(sb)->s_es;
        for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
                unsigned x;

                desc = ext2_get_group_desc (sb, i, NULL);
                if (!desc)
                        continue;
                desc_count += le16_to_cpu(desc->bg_free_inodes_count);
                brelse(bitmap_bh);
                bitmap_bh = read_inode_bitmap(sb, i);
                if (!bitmap_bh)
                        continue;

                x = ext2_count_free(bitmap_bh, EXT2_INODES_PER_GROUP(sb) / 8);
                printk("group %d: stored = %d, counted = %u\n",
                        i, le16_to_cpu(desc->bg_free_inodes_count), x);
                bitmap_count += x;
        }
        brelse(bitmap_bh);
        printk("ext2_count_free_inodes: stored = %lu, computed = %lu, %lu\n",
                percpu_counter_read(&EXT2_SB(sb)->s_freeinodes_counter),
                desc_count, bitmap_count);
        return desc_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_inodes_count);
        }
        return desc_count;
#endif
}

/* Called at mount-time, super-block is locked */
unsigned long ext2_count_dirs (struct super_block * sb)
{
        unsigned long count = 0;
        int i;

        for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
                struct ext2_group_desc *gdp = ext2_get_group_desc (sb, i, NULL);
                if (!gdp)
                        continue;
                count += le16_to_cpu(gdp->bg_used_dirs_count);
        }
        return count;
}