// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/sysv/ialloc.c
 *
 *  minix/bitmap.c
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  ext/freelists.c
 *  Copyright (C) 1992  Remy Card (card@masi.ibp.fr)
 *
 *  xenix/alloc.c
 *  Copyright (C) 1992  Doug Evans
 *
 *  coh/alloc.c
 *  Copyright (C) 1993  Pascal Haible, Bruno Haible
 *
 *  sysv/ialloc.c
 *  Copyright (C) 1993  Bruno Haible
 *
 *  This file contains code for allocating/freeing inodes.
 */

#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/sched.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include "sysv.h"

/* We don't trust the value of
   sb->sv_sbd2->s_tinode = *sb->sv_sb_total_free_inodes
   but we nevertheless keep it up to date. */

/* An inode on disk is considered free if both i_mode == 0 and i_nlink == 0. */

/* return &sb->sv_sb_fic_inodes[i] = &sbd->s_inode[i]; */
static inline sysv_ino_t *
sv_sb_fic_inode(struct super_block * sb, unsigned int i)
{
        struct sysv_sb_info *sbi = SYSV_SB(sb);

        if (sbi->s_bh1 == sbi->s_bh2)
                return &sbi->s_sb_fic_inodes[i];
        else {
                /* 512 byte Xenix FS */
                unsigned int offset = offsetof(struct xenix_super_block, s_inode[i]);
                if (offset < 512)
                        return (sysv_ino_t*)(sbi->s_sbd1 + offset);
                else
                        return (sysv_ino_t*)(sbi->s_sbd2 + offset);
        }
}

struct sysv_inode *
sysv_raw_inode(struct super_block *sb, unsigned ino, struct buffer_head **bh)
{
        struct sysv_sb_info *sbi = SYSV_SB(sb);
        struct sysv_inode *res;
        int block = sbi->s_firstinodezone + sbi->s_block_base;

        block += (ino-1) >> sbi->s_inodes_per_block_bits;
        *bh = sb_bread(sb, block);
        if (!*bh)
                return NULL;
        res = (struct sysv_inode *)(*bh)->b_data;
        return res + ((ino-1) & sbi->s_inodes_per_block_1);
}

static int refill_free_cache(struct super_block *sb)
{
        struct sysv_sb_info *sbi = SYSV_SB(sb);
        struct buffer_head * bh;
        struct sysv_inode * raw_inode;
        int i = 0, ino;

        ino = SYSV_ROOT_INO+1;
        raw_inode = sysv_raw_inode(sb, ino, &bh);
        if (!raw_inode)
                goto out;
        while (ino <= sbi->s_ninodes) {
                if (raw_inode->i_mode == 0 && raw_inode->i_nlink == 0) {
                        *sv_sb_fic_inode(sb,i++) = cpu_to_fs16(SYSV_SB(sb), ino);
                        if (i == sbi->s_fic_size)
                                break;
                }
                if ((ino++ & sbi->s_inodes_per_block_1) == 0) {
                        brelse(bh);
                        raw_inode = sysv_raw_inode(sb, ino, &bh);
                        if (!raw_inode)
                                goto out;
                } else
                        raw_inode++;
        }
        brelse(bh);
out:
        return i;
}

void sysv_free_inode(struct inode * inode)
{
        struct super_block *sb = inode->i_sb;
        struct sysv_sb_info *sbi = SYSV_SB(sb);
        unsigned int ino;
        struct buffer_head * bh;
        struct sysv_inode * raw_inode;
        unsigned count;

        sb = inode->i_sb;
        ino = inode->i_ino;
        if (ino <= SYSV_ROOT_INO || ino > sbi->s_ninodes) {
                printk("sysv_free_inode: inode 0,1,2 or nonexistent inode\n");
                return;
        }
        raw_inode = sysv_raw_inode(sb, ino, &bh);
        if (!raw_inode) {
                printk("sysv_free_inode: unable to read inode block on device "
                       "%s\n", inode->i_sb->s_id);
                return;
        }
        mutex_lock(&sbi->s_lock);
        count = fs16_to_cpu(sbi, *sbi->s_sb_fic_count);
        if (count < sbi->s_fic_size) {
                *sv_sb_fic_inode(sb,count++) = cpu_to_fs16(sbi, ino);
                *sbi->s_sb_fic_count = cpu_to_fs16(sbi, count);
        }
        fs16_add(sbi, sbi->s_sb_total_free_inodes, 1);
        dirty_sb(sb);
        memset(raw_inode, 0, sizeof(struct sysv_inode));
        mark_buffer_dirty(bh);
        mutex_unlock(&sbi->s_lock);
        brelse(bh);
}

struct inode * sysv_new_inode(const struct inode * dir, umode_t mode)
{
        struct super_block *sb = dir->i_sb;
        struct sysv_sb_info *sbi = SYSV_SB(sb);
        struct inode *inode;
        sysv_ino_t ino;
        unsigned count;
        struct writeback_control wbc = {
                .sync_mode = WB_SYNC_NONE
        };

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

        mutex_lock(&sbi->s_lock);
        count = fs16_to_cpu(sbi, *sbi->s_sb_fic_count);
        if (count == 0 || (*sv_sb_fic_inode(sb,count-1) == 0)) {
                count = refill_free_cache(sb);
                if (count == 0) {
                        iput(inode);
                        mutex_unlock(&sbi->s_lock);
                        return ERR_PTR(-ENOSPC);
                }
        }
        /* Now count > 0. */
        ino = *sv_sb_fic_inode(sb,--count);
        *sbi->s_sb_fic_count = cpu_to_fs16(sbi, count);
        fs16_add(sbi, sbi->s_sb_total_free_inodes, -1);
        dirty_sb(sb);
        inode_init_owner(&init_user_ns, inode, dir, mode);
        inode->i_ino = fs16_to_cpu(sbi, ino);
        inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
        inode->i_blocks = 0;
        memset(SYSV_I(inode)->i_data, 0, sizeof(SYSV_I(inode)->i_data));
        SYSV_I(inode)->i_dir_start_lookup = 0;
        insert_inode_hash(inode);
        mark_inode_dirty(inode);

        sysv_write_inode(inode, &wbc);  /* ensure inode not allocated again */
        mark_inode_dirty(inode);        /* cleared by sysv_write_inode() */
        /* That's it. */
        mutex_unlock(&sbi->s_lock);
        return inode;
}

unsigned long sysv_count_free_inodes(struct super_block * sb)
{
        struct sysv_sb_info *sbi = SYSV_SB(sb);
        struct buffer_head * bh;
        struct sysv_inode * raw_inode;
        int ino, count, sb_count;

        mutex_lock(&sbi->s_lock);

        sb_count = fs16_to_cpu(sbi, *sbi->s_sb_total_free_inodes);

        if (0)
                goto trust_sb;

        /* this causes a lot of disk traffic ... */
        count = 0;
        ino = SYSV_ROOT_INO+1;
        raw_inode = sysv_raw_inode(sb, ino, &bh);
        if (!raw_inode)
                goto Eio;
        while (ino <= sbi->s_ninodes) {
                if (raw_inode->i_mode == 0 && raw_inode->i_nlink == 0)
                        count++;
                if ((ino++ & sbi->s_inodes_per_block_1) == 0) {
                        brelse(bh);
                        raw_inode = sysv_raw_inode(sb, ino, &bh);
                        if (!raw_inode)
                                goto Eio;
                } else
                        raw_inode++;
        }
        brelse(bh);
        if (count != sb_count)
                goto Einval;
out:
        mutex_unlock(&sbi->s_lock);
        return count;

Einval:
        printk("sysv_count_free_inodes: "
                "free inode count was %d, correcting to %d\n",
                sb_count, count);
        if (!sb_rdonly(sb)) {
                *sbi->s_sb_total_free_inodes = cpu_to_fs16(SYSV_SB(sb), count);
                dirty_sb(sb);
        }
        goto out;

Eio:
        printk("sysv_count_free_inodes: unable to read inode table\n");
trust_sb:
        count = sb_count;
        goto out;
}