// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  linux/fs/adfs/inode.c
   *
   *  Copyright (C) 1997-1999 Russell King

   */

  #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, ADFS_I(inode)->indaddr,
  					 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_filetype(ADFS_I(inode)->loadaddr)) {

  	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 ia_mode)

  {

  	struct adfs_sb_info *asb = ADFS_SB(sb);

  	umode_t mode;
  	int attr;

  
  	/* FIXME: should we be able to alter a link? */
  	if (S_ISLNK(inode->i_mode))
  		return ADFS_I(inode)->attr;

  	/* Directories do not have read/write permissions on the media */

  	if (S_ISDIR(inode->i_mode))

  		return ADFS_NDA_DIRECTORY;

  	attr = 0;
  	mode = ia_mode & asb->s_owner_mask;

  	if (mode & S_IRUGO)
  		attr |= ADFS_NDA_OWNER_READ;
  	if (mode & S_IWUGO)
  		attr |= ADFS_NDA_OWNER_WRITE;

  	mode = ia_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;
  }

  static const s64 nsec_unix_epoch_diff_risc_os_epoch = 2208988800000000000LL;

  /*
   * 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 timespec64 *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)
  	 */

  	s64 nsec;

  	if (!adfs_inode_is_stamped(inode))

  		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_timespec64(nsec);

  	return;
  
   cur_time:

  	*tv = current_time(inode);

  	return;
  
   too_early:
  	tv->tv_sec = tv->tv_nsec = 0;
  	return;

  }

  /* Convert an Unix time to ADFS time for an entry that is already stamped. */
  static void adfs_unix2adfs_time(struct inode *inode,
  				const struct timespec64 *ts)

  {

  	s64 cs, nsec = timespec64_to_ns(ts);

  	/* convert from Unix to RISC OS epoch */
  	nsec += nsec_unix_epoch_diff_risc_os_epoch;

  	/* convert from nanoseconds to centiseconds */
  	cs = div_s64(nsec, 10000000);
  
  	cs = clamp_t(s64, cs, 0, 0xffffffffff);
  
  	ADFS_I(inode)->loadaddr &= ~0xff;
  	ADFS_I(inode)->loadaddr |= (cs >> 32) & 0xff;
  	ADFS_I(inode)->execaddr = cs;

  }
  
  /*
   * 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->indaddr;

  	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)->indaddr   = obj->indaddr;

  	ADFS_I(inode)->loadaddr  = obj->loadaddr;
  	ADFS_I(inode)->execaddr  = obj->execaddr;
  	ADFS_I(inode)->attr      = obj->attr;

  
  	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;
  	}

  	inode_fake_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 = d_inode(dentry);

  	struct super_block *sb = inode->i_sb;
  	unsigned int ia_valid = attr->ia_valid;
  	int error;
  	

  	error = setattr_prepare(dentry, 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 && adfs_inode_is_stamped(inode)) {
  		adfs_unix2adfs_time(inode, &attr->ia_mtime);
  		adfs_adfs2unix_time(&inode->i_mtime, inode);

  	}

  	/*
  	 * 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, attr->ia_mode);

  		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.indaddr	= ADFS_I(inode)->indaddr;

  	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;
  }