/*
   *  linux/fs/adfs/inode.c
   *
   *  Copyright (C) 1997-1999 Russell King
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  #include <linux/buffer_head.h>
  #include <linux/writeback.h>
  #include "adfs.h"
  
  /*
   * Lookup/Create a block at offset 'block' into 'inode'.  We currently do
   * not support creation of new blocks, so we return -EIO for this case.
   */
  static int
  adfs_get_block(struct inode *inode, sector_t block, struct buffer_head *bh,
  	       int create)
  {
  	if (!create) {
  		if (block >= inode->i_blocks)
  			goto abort_toobig;
  
  		block = __adfs_block_map(inode->i_sb, inode->i_ino, block);
  		if (block)
  			map_bh(bh, inode->i_sb, block);
  		return 0;
  	}
  	/* don't support allocation of blocks yet */
  	return -EIO;
  
  abort_toobig:
  	return 0;
  }
  
  static int adfs_writepage(struct page *page, struct writeback_control *wbc)
  {
  	return block_write_full_page(page, adfs_get_block, wbc);
  }
  
  static int adfs_readpage(struct file *file, struct page *page)
  {
  	return block_read_full_page(page, adfs_get_block);
  }
  
  static void adfs_write_failed(struct address_space *mapping, loff_t to)
  {
  	struct inode *inode = mapping->host;
  
  	if (to > inode->i_size)
  		truncate_pagecache(inode, inode->i_size);
  }
  
  static int adfs_write_begin(struct file *file, struct address_space *mapping,
  			loff_t pos, unsigned len, unsigned flags,
  			struct page **pagep, void **fsdata)
  {
  	int ret;
  
  	*pagep = NULL;
  	ret = cont_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
  				adfs_get_block,
  				&ADFS_I(mapping->host)->mmu_private);
  	if (unlikely(ret))
  		adfs_write_failed(mapping, pos + len);
  
  	return ret;
  }
  
  static sector_t _adfs_bmap(struct address_space *mapping, sector_t block)
  {
  	return generic_block_bmap(mapping, block, adfs_get_block);
  }
  
  static const struct address_space_operations adfs_aops = {
  	.readpage	= adfs_readpage,
  	.writepage	= adfs_writepage,
  	.write_begin	= adfs_write_begin,
  	.write_end	= generic_write_end,
  	.bmap		= _adfs_bmap
  };
  
  /*
   * Convert ADFS attributes and filetype to Linux permission.
   */
  static umode_t
  adfs_atts2mode(struct super_block *sb, struct inode *inode)
  {
  	unsigned int attr = ADFS_I(inode)->attr;
  	umode_t mode, rmask;
  	struct adfs_sb_info *asb = ADFS_SB(sb);
  
  	if (attr & ADFS_NDA_DIRECTORY) {
  		mode = S_IRUGO & asb->s_owner_mask;
  		return S_IFDIR | S_IXUGO | mode;
  	}
  
  	switch (ADFS_I(inode)->filetype) {
  	case 0xfc0:	/* LinkFS */
  		return S_IFLNK|S_IRWXUGO;
  
  	case 0xfe6:	/* UnixExec */
  		rmask = S_IRUGO | S_IXUGO;
  		break;
  
  	default:
  		rmask = S_IRUGO;
  	}
  
  	mode = S_IFREG;
  
  	if (attr & ADFS_NDA_OWNER_READ)
  		mode |= rmask & asb->s_owner_mask;
  
  	if (attr & ADFS_NDA_OWNER_WRITE)
  		mode |= S_IWUGO & asb->s_owner_mask;
  
  	if (attr & ADFS_NDA_PUBLIC_READ)
  		mode |= rmask & asb->s_other_mask;
  
  	if (attr & ADFS_NDA_PUBLIC_WRITE)
  		mode |= S_IWUGO & asb->s_other_mask;
  	return mode;
  }
  
  /*
   * Convert Linux permission to ADFS attribute.  We try to do the reverse
   * of atts2mode, but there is not a 1:1 translation.
   */
  static int
  adfs_mode2atts(struct super_block *sb, struct inode *inode)
  {
  	umode_t mode;
  	int attr;
  	struct adfs_sb_info *asb = ADFS_SB(sb);
  
  	/* FIXME: should we be able to alter a link? */
  	if (S_ISLNK(inode->i_mode))
  		return ADFS_I(inode)->attr;
  
  	if (S_ISDIR(inode->i_mode))
  		attr = ADFS_NDA_DIRECTORY;
  	else
  		attr = 0;
  
  	mode = inode->i_mode & asb->s_owner_mask;
  	if (mode & S_IRUGO)
  		attr |= ADFS_NDA_OWNER_READ;
  	if (mode & S_IWUGO)
  		attr |= ADFS_NDA_OWNER_WRITE;
  
  	mode = inode->i_mode & asb->s_other_mask;
  	mode &= ~asb->s_owner_mask;
  	if (mode & S_IRUGO)
  		attr |= ADFS_NDA_PUBLIC_READ;
  	if (mode & S_IWUGO)
  		attr |= ADFS_NDA_PUBLIC_WRITE;
  
  	return attr;
  }
  
  /*
   * Convert an ADFS time to Unix time.  ADFS has a 40-bit centi-second time
   * referenced to 1 Jan 1900 (til 2248) so we need to discard 2208988800 seconds
   * of time to convert from RISC OS epoch to Unix epoch.
   */
  static void
  adfs_adfs2unix_time(struct timespec *tv, struct inode *inode)
  {
  	unsigned int high, low;
  	/* 01 Jan 1970 00:00:00 (Unix epoch) as nanoseconds since
  	 * 01 Jan 1900 00:00:00 (RISC OS epoch)
  	 */
  	static const s64 nsec_unix_epoch_diff_risc_os_epoch =
  							2208988800000000000LL;
  	s64 nsec;
  
  	if (ADFS_I(inode)->stamped == 0)
  		goto cur_time;
  
  	high = ADFS_I(inode)->loadaddr & 0xFF; /* top 8 bits of timestamp */
  	low  = ADFS_I(inode)->execaddr;    /* bottom 32 bits of timestamp */
  
  	/* convert 40-bit centi-seconds to 32-bit seconds
  	 * going via nanoseconds to retain precision
  	 */
  	nsec = (((s64) high << 32) | (s64) low) * 10000000; /* cs to ns */
  
  	/* Files dated pre  01 Jan 1970 00:00:00. */
  	if (nsec < nsec_unix_epoch_diff_risc_os_epoch)
  		goto too_early;
  
  	/* convert from RISC OS to Unix epoch */
  	nsec -= nsec_unix_epoch_diff_risc_os_epoch;
  
  	*tv = ns_to_timespec(nsec);
  	return;
  
   cur_time:
  	*tv = CURRENT_TIME;
  	return;
  
   too_early:
  	tv->tv_sec = tv->tv_nsec = 0;
  	return;
  }
  
  /*
   * Convert an Unix time to ADFS time.  We only do this if the entry has a
   * time/date stamp already.
   */
  static void
  adfs_unix2adfs_time(struct inode *inode, unsigned int secs)
  {
  	unsigned int high, low;
  
  	if (ADFS_I(inode)->stamped) {
  		/* convert 32-bit seconds to 40-bit centi-seconds */
  		low  = (secs & 255) * 100;
  		high = (secs / 256) * 100 + (low >> 8) + 0x336e996a;
  
  		ADFS_I(inode)->loadaddr = (high >> 24) |
  				(ADFS_I(inode)->loadaddr & ~0xff);
  		ADFS_I(inode)->execaddr = (low & 255) | (high << 8);
  	}
  }
  
  /*
   * Fill in the inode information from the object information.
   *
   * Note that this is an inode-less filesystem, so we can't use the inode
   * number to reference the metadata on the media.  Instead, we use the
   * inode number to hold the object ID, which in turn will tell us where
   * the data is held.  We also save the parent object ID, and with these
   * two, we can locate the metadata.
   *
   * This does mean that we rely on an objects parent remaining the same at
   * all times - we cannot cope with a cross-directory rename (yet).
   */
  struct inode *
  adfs_iget(struct super_block *sb, struct object_info *obj)
  {
  	struct inode *inode;
  
  	inode = new_inode(sb);
  	if (!inode)
  		goto out;
  
  	inode->i_uid	 = ADFS_SB(sb)->s_uid;
  	inode->i_gid	 = ADFS_SB(sb)->s_gid;
  	inode->i_ino	 = obj->file_id;
  	inode->i_size	 = obj->size;
  	set_nlink(inode, 2);
  	inode->i_blocks	 = (inode->i_size + sb->s_blocksize - 1) >>
  			    sb->s_blocksize_bits;
  
  	/*
  	 * we need to save the parent directory ID so that
  	 * write_inode can update the directory information
  	 * for this file.  This will need special handling
  	 * for cross-directory renames.
  	 */
  	ADFS_I(inode)->parent_id = obj->parent_id;
  	ADFS_I(inode)->loadaddr  = obj->loadaddr;
  	ADFS_I(inode)->execaddr  = obj->execaddr;
  	ADFS_I(inode)->attr      = obj->attr;
  	ADFS_I(inode)->filetype  = obj->filetype;
  	ADFS_I(inode)->stamped   = ((obj->loadaddr & 0xfff00000) == 0xfff00000);
  
  	inode->i_mode	 = adfs_atts2mode(sb, inode);
  	adfs_adfs2unix_time(&inode->i_mtime, inode);
  	inode->i_atime = inode->i_mtime;
  	inode->i_ctime = inode->i_mtime;
  
  	if (S_ISDIR(inode->i_mode)) {
  		inode->i_op	= &adfs_dir_inode_operations;
  		inode->i_fop	= &adfs_dir_operations;
  	} else if (S_ISREG(inode->i_mode)) {
  		inode->i_op	= &adfs_file_inode_operations;
  		inode->i_fop	= &adfs_file_operations;
  		inode->i_mapping->a_ops = &adfs_aops;
  		ADFS_I(inode)->mmu_private = inode->i_size;
  	}
  
  	insert_inode_hash(inode);
  
  out:
  	return inode;
  }
  
  /*
   * Validate and convert a changed access mode/time to their ADFS equivalents.
   * adfs_write_inode will actually write the information back to the directory
   * later.
   */
  int
  adfs_notify_change(struct dentry *dentry, struct iattr *attr)
  {
  	struct inode *inode = dentry->d_inode;
  	struct super_block *sb = inode->i_sb;
  	unsigned int ia_valid = attr->ia_valid;
  	int error;
  	
  	error = inode_change_ok(inode, attr);
  
  	/*
  	 * we can't change the UID or GID of any file -
  	 * we have a global UID/GID in the superblock
  	 */
  	if ((ia_valid & ATTR_UID && !uid_eq(attr->ia_uid, ADFS_SB(sb)->s_uid)) ||
  	    (ia_valid & ATTR_GID && !gid_eq(attr->ia_gid, ADFS_SB(sb)->s_gid)))
  		error = -EPERM;
  
  	if (error)
  		goto out;
  
  	/* XXX: this is missing some actual on-disk truncation.. */
  	if (ia_valid & ATTR_SIZE)
  		truncate_setsize(inode, attr->ia_size);
  
  	if (ia_valid & ATTR_MTIME) {
  		inode->i_mtime = attr->ia_mtime;
  		adfs_unix2adfs_time(inode, attr->ia_mtime.tv_sec);
  	}
  	/*
  	 * FIXME: should we make these == to i_mtime since we don't
  	 * have the ability to represent them in our filesystem?
  	 */
  	if (ia_valid & ATTR_ATIME)
  		inode->i_atime = attr->ia_atime;
  	if (ia_valid & ATTR_CTIME)
  		inode->i_ctime = attr->ia_ctime;
  	if (ia_valid & ATTR_MODE) {
  		ADFS_I(inode)->attr = adfs_mode2atts(sb, inode);
  		inode->i_mode = adfs_atts2mode(sb, inode);
  	}
  
  	/*
  	 * FIXME: should we be marking this inode dirty even if
  	 * we don't have any metadata to write back?
  	 */
  	if (ia_valid & (ATTR_SIZE | ATTR_MTIME | ATTR_MODE))
  		mark_inode_dirty(inode);
  out:
  	return error;
  }
  
  /*
   * write an existing inode back to the directory, and therefore the disk.
   * The adfs-specific inode data has already been updated by
   * adfs_notify_change()
   */
  int adfs_write_inode(struct inode *inode, struct writeback_control *wbc)
  {
  	struct super_block *sb = inode->i_sb;
  	struct object_info obj;
  	int ret;
  
  	obj.file_id	= inode->i_ino;
  	obj.name_len	= 0;
  	obj.parent_id	= ADFS_I(inode)->parent_id;
  	obj.loadaddr	= ADFS_I(inode)->loadaddr;
  	obj.execaddr	= ADFS_I(inode)->execaddr;
  	obj.attr	= ADFS_I(inode)->attr;
  	obj.size	= inode->i_size;
  
  	ret = adfs_dir_update(sb, &obj, wbc->sync_mode == WB_SYNC_ALL);
  	return ret;
  }