/*
   * fs/logfs/file.c	- prepare_write, commit_write and friends
   *
   * As should be obvious for Linux kernel code, license is GPLv2
   *
   * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
   */
  #include "logfs.h"
  #include <linux/sched.h>
  #include <linux/writeback.h>
  
  static int logfs_write_begin(struct file *file, struct address_space *mapping,
  		loff_t pos, unsigned len, unsigned flags,
  		struct page **pagep, void **fsdata)
  {
  	struct inode *inode = mapping->host;
  	struct page *page;

  	pgoff_t index = pos >> PAGE_SHIFT;

  
  	page = grab_cache_page_write_begin(mapping, index, flags);
  	if (!page)
  		return -ENOMEM;
  	*pagep = page;

  	if ((len == PAGE_SIZE) || PageUptodate(page))

  		return 0;

  	if ((pos & PAGE_MASK) >= i_size_read(inode)) {
  		unsigned start = pos & (PAGE_SIZE - 1);

  		unsigned end = start + len;
  
  		/* Reading beyond i_size is simple: memset to zero */

  		zero_user_segments(page, 0, start, end, PAGE_SIZE);

  		return 0;
  	}
  	return logfs_readpage_nolock(page);
  }
  
  static int logfs_write_end(struct file *file, struct address_space *mapping,
  		loff_t pos, unsigned len, unsigned copied, struct page *page,
  		void *fsdata)
  {
  	struct inode *inode = mapping->host;
  	pgoff_t index = page->index;

  	unsigned start = pos & (PAGE_SIZE - 1);

  	unsigned end = start + copied;
  	int ret = 0;

  	BUG_ON(PAGE_SIZE != inode->i_sb->s_blocksize);

  	BUG_ON(page->index > I3_BLOCKS);
  
  	if (copied < len) {
  		/*
  		 * Short write of a non-initialized paged.  Just tell userspace
  		 * to retry the entire page.
  		 */
  		if (!PageUptodate(page)) {
  			copied = 0;
  			goto out;
  		}
  	}
  	if (copied == 0)
  		goto out; /* FIXME: do we need to update inode? */

  	if (i_size_read(inode) < (index << PAGE_SHIFT) + end) {
  		i_size_write(inode, (index << PAGE_SHIFT) + end);

  		mark_inode_dirty_sync(inode);
  	}
  
  	SetPageUptodate(page);
  	if (!PageDirty(page)) {
  		if (!get_page_reserve(inode, page))
  			__set_page_dirty_nobuffers(page);
  		else
  			ret = logfs_write_buf(inode, page, WF_LOCK);
  	}
  out:
  	unlock_page(page);

  	put_page(page);

  	return ret ? ret : copied;
  }
  
  int logfs_readpage(struct file *file, struct page *page)
  {
  	int ret;
  
  	ret = logfs_readpage_nolock(page);
  	unlock_page(page);
  	return ret;
  }
  
  /* Clear the page's dirty flag in the radix tree. */
  /* TODO: mucking with PageWriteback is silly.  Add a generic function to clear
   * the dirty bit from the radix tree for filesystems that don't have to wait
   * for page writeback to finish (i.e. any compressing filesystem).
   */
  static void clear_radix_tree_dirty(struct page *page)
  {
  	BUG_ON(PagePrivate(page) || page->private);
  	set_page_writeback(page);
  	end_page_writeback(page);
  }
  
  static int __logfs_writepage(struct page *page)
  {
  	struct inode *inode = page->mapping->host;
  	int err;
  
  	err = logfs_write_buf(inode, page, WF_LOCK);
  	if (err)
  		set_page_dirty(page);
  	else
  		clear_radix_tree_dirty(page);
  	unlock_page(page);
  	return err;
  }
  
  static int logfs_writepage(struct page *page, struct writeback_control *wbc)
  {
  	struct inode *inode = page->mapping->host;
  	loff_t i_size = i_size_read(inode);

  	pgoff_t end_index = i_size >> PAGE_SHIFT;

  	unsigned offset;
  	u64 bix;
  	level_t level;
  
  	log_file("logfs_writepage(%lx, %lx, %p)
  ", inode->i_ino, page->index,
  			page);
  
  	logfs_unpack_index(page->index, &bix, &level);
  
  	/* Indirect blocks are never truncated */
  	if (level != 0)
  		return __logfs_writepage(page);
  
  	/*
  	 * TODO: everything below is a near-verbatim copy of nobh_writepage().
  	 * The relevant bits should be factored out after logfs is merged.
  	 */
  
  	/* Is the page fully inside i_size? */
  	if (bix < end_index)
  		return __logfs_writepage(page);
  
  	 /* Is the page fully outside i_size? (truncate in progress) */

  	offset = i_size & (PAGE_SIZE-1);

  	if (bix > end_index || offset == 0) {
  		unlock_page(page);
  		return 0; /* don't care */
  	}
  
  	/*
  	 * The page straddles i_size.  It must be zeroed out on each and every
  	 * writepage invokation because it may be mmapped.  "A file is mapped
  	 * in multiples of the page size.  For a file that is not a multiple of
  	 * the  page size, the remaining memory is zeroed when mapped, and
  	 * writes to that region are not written out to the file."
  	 */

  	zero_user_segment(page, offset, PAGE_SIZE);

  	return __logfs_writepage(page);
  }

  static void logfs_invalidatepage(struct page *page, unsigned int offset,
  				 unsigned int length)

  {

  	struct logfs_block *block = logfs_block(page);
  
  	if (block->reserved_bytes) {
  		struct super_block *sb = page->mapping->host->i_sb;
  		struct logfs_super *super = logfs_super(sb);
  
  		super->s_dirty_pages -= block->reserved_bytes;
  		block->ops->free_block(sb, block);
  		BUG_ON(bitmap_weight(block->alias_map, LOGFS_BLOCK_FACTOR));
  	} else
  		move_page_to_btree(page);

  	BUG_ON(PagePrivate(page) || page->private);
  }
  
  static int logfs_releasepage(struct page *page, gfp_t only_xfs_uses_this)
  {
  	return 0; /* None of these are easy to release */
  }

  long logfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

  {

  	struct inode *inode = file_inode(file);

  	struct logfs_inode *li = logfs_inode(inode);
  	unsigned int oldflags, flags;
  	int err;
  
  	switch (cmd) {
  	case FS_IOC_GETFLAGS:
  		flags = li->li_flags & LOGFS_FL_USER_VISIBLE;
  		return put_user(flags, (int __user *)arg);
  	case FS_IOC_SETFLAGS:
  		if (IS_RDONLY(inode))
  			return -EROFS;

  		if (!inode_owner_or_capable(inode))

  			return -EACCES;
  
  		err = get_user(flags, (int __user *)arg);
  		if (err)
  			return err;

  		inode_lock(inode);

  		oldflags = li->li_flags;
  		flags &= LOGFS_FL_USER_MODIFIABLE;
  		flags |= oldflags & ~LOGFS_FL_USER_MODIFIABLE;
  		li->li_flags = flags;

  		inode_unlock(inode);

  		inode->i_ctime = current_time(inode);

  		mark_inode_dirty_sync(inode);
  		return 0;
  
  	default:
  		return -ENOTTY;
  	}
  }

  int logfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)

  {

  	struct super_block *sb = file->f_mapping->host->i_sb;

  	struct inode *inode = file->f_mapping->host;
  	int ret;
  
  	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
  	if (ret)
  		return ret;

  	inode_lock(inode);

  	logfs_get_wblocks(sb, NULL, WF_LOCK);

  	logfs_write_anchor(sb);

  	logfs_put_wblocks(sb, NULL, WF_LOCK);

  	inode_unlock(inode);

  	return 0;
  }
  
  static int logfs_setattr(struct dentry *dentry, struct iattr *attr)
  {

  	struct inode *inode = d_inode(dentry);

  	int err = 0;

  	err = setattr_prepare(dentry, attr);

  	if (err)
  		return err;

  	if (attr->ia_valid & ATTR_SIZE) {

  		err = logfs_truncate(inode, attr->ia_size);

  		if (err)
  			return err;
  	}

  	setattr_copy(inode, attr);
  	mark_inode_dirty(inode);
  	return 0;

  }
  
  const struct inode_operations logfs_reg_iops = {
  	.setattr	= logfs_setattr,
  };
  
  const struct file_operations logfs_reg_fops = {

  	.read_iter	= generic_file_read_iter,

  	.write_iter	= generic_file_write_iter,

  	.fsync		= logfs_fsync,

  	.unlocked_ioctl	= logfs_ioctl,

  	.llseek		= generic_file_llseek,
  	.mmap		= generic_file_readonly_mmap,
  	.open		= generic_file_open,

  };
  
  const struct address_space_operations logfs_reg_aops = {
  	.invalidatepage	= logfs_invalidatepage,
  	.readpage	= logfs_readpage,
  	.releasepage	= logfs_releasepage,
  	.set_page_dirty	= __set_page_dirty_nobuffers,
  	.writepage	= logfs_writepage,
  	.writepages	= generic_writepages,
  	.write_begin	= logfs_write_begin,
  	.write_end	= logfs_write_end,
  };