/*
   *  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
  ");
  		return;
  	}
  	raw_inode = sysv_raw_inode(sb, ino, &bh);
  	if (!raw_inode) {
  		printk("sysv_free_inode: unable to read inode block on device "
  		       "%s
  ", 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(inode, dir, mode);
  	inode->i_ino = fs16_to_cpu(sbi, ino);
  	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME_SEC;
  	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
  ",
  		sb_count, count);
  	if (!(sb->s_flags & MS_RDONLY)) {
  		*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
  ");
  trust_sb:
  	count = sb_count;
  	goto out;
  }