/*
   * High-level sync()-related operations
   */
  
  #include <linux/kernel.h>
  #include <linux/file.h>
  #include <linux/fs.h>
  #include <linux/module.h>

  #include <linux/sched.h>

  #include <linux/writeback.h>
  #include <linux/syscalls.h>
  #include <linux/linkage.h>
  #include <linux/pagemap.h>

  #include <linux/quotaops.h>
  #include <linux/buffer_head.h>

  
  #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
  			SYNC_FILE_RANGE_WAIT_AFTER)
  
  /*

   * sync everything.  Start out by waking pdflush, because that writes back
   * all queues in parallel.
   */
  static void do_sync(unsigned long wait)
  {
  	wakeup_pdflush(0);
  	sync_inodes(0);		/* All mappings, inodes and their blockdevs */

  	vfs_dq_sync(NULL);

  	sync_supers();		/* Write the superblocks */
  	sync_filesystems(0);	/* Start syncing the filesystems */
  	sync_filesystems(wait);	/* Waitingly sync the filesystems */
  	sync_inodes(wait);	/* Mappings, inodes and blockdevs, again. */
  	if (!wait)
  		printk("Emergency Sync complete
  ");
  	if (unlikely(laptop_mode))
  		laptop_sync_completion();
  }

  SYSCALL_DEFINE0(sync)

  {
  	do_sync(1);
  	return 0;
  }

  static void do_sync_work(struct work_struct *work)
  {
  	do_sync(0);
  	kfree(work);
  }

  void emergency_sync(void)
  {

  	struct work_struct *work;
  
  	work = kmalloc(sizeof(*work), GFP_ATOMIC);
  	if (work) {
  		INIT_WORK(work, do_sync_work);
  		schedule_work(work);
  	}

  }
  
  /*
   * Generic function to fsync a file.
   *
   * filp may be NULL if called via the msync of a vma.
   */
  int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
  {
  	struct inode * inode = dentry->d_inode;
  	struct super_block * sb;
  	int ret, err;
  
  	/* sync the inode to buffers */
  	ret = write_inode_now(inode, 0);
  
  	/* sync the superblock to buffers */
  	sb = inode->i_sb;
  	lock_super(sb);

  	if (sb->s_dirt && sb->s_op->write_super)

  		sb->s_op->write_super(sb);
  	unlock_super(sb);
  
  	/* .. finally sync the buffers to disk */
  	err = sync_blockdev(sb->s_bdev);
  	if (!ret)
  		ret = err;
  	return ret;
  }

  /**
   * vfs_fsync - perform a fsync or fdatasync on a file
   * @file:		file to sync
   * @dentry:		dentry of @file
   * @data:		only perform a fdatasync operation
   *
   * Write back data and metadata for @file to disk.  If @datasync is
   * set only metadata needed to access modified file data is written.
   *
   * In case this function is called from nfsd @file may be %NULL and
   * only @dentry is set.  This can only happen when the filesystem
   * implements the export_operations API.
   */
  int vfs_fsync(struct file *file, struct dentry *dentry, int datasync)

  {

  	const struct file_operations *fop;
  	struct address_space *mapping;
  	int err, ret;
  
  	/*
  	 * Get mapping and operations from the file in case we have
  	 * as file, or get the default values for them in case we
  	 * don't have a struct file available.  Damn nfsd..
  	 */
  	if (file) {
  		mapping = file->f_mapping;
  		fop = file->f_op;
  	} else {
  		mapping = dentry->d_inode->i_mapping;
  		fop = dentry->d_inode->i_fop;
  	}

  	if (!fop || !fop->fsync) {

  		ret = -EINVAL;
  		goto out;
  	}
  
  	ret = filemap_fdatawrite(mapping);
  
  	/*
  	 * We need to protect against concurrent writers, which could cause
  	 * livelocks in fsync_buffers_list().
  	 */
  	mutex_lock(&mapping->host->i_mutex);

  	err = fop->fsync(file, dentry, datasync);

  	if (!ret)
  		ret = err;
  	mutex_unlock(&mapping->host->i_mutex);
  	err = filemap_fdatawait(mapping);
  	if (!ret)
  		ret = err;
  out:
  	return ret;
  }

  EXPORT_SYMBOL(vfs_fsync);

  static int do_fsync(unsigned int fd, int datasync)

  {
  	struct file *file;
  	int ret = -EBADF;
  
  	file = fget(fd);
  	if (file) {

  		ret = vfs_fsync(file, file->f_path.dentry, datasync);

  		fput(file);
  	}
  	return ret;
  }

  SYSCALL_DEFINE1(fsync, unsigned int, fd)

  {

  	return do_fsync(fd, 0);

  }

  SYSCALL_DEFINE1(fdatasync, unsigned int, fd)

  {

  	return do_fsync(fd, 1);

  }
  
  /*

   * sys_sync_file_range() permits finely controlled syncing over a segment of
   * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
   * zero then sys_sync_file_range() will operate from offset out to EOF.
   *
   * The flag bits are:
   *
   * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
   * before performing the write.
   *
   * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the

   * range which are not presently under writeback. Note that this may block for
   * significant periods due to exhaustion of disk request structures.

   *
   * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
   * after performing the write.
   *
   * Useful combinations of the flag bits are:
   *
   * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
   * in the range which were dirty on entry to sys_sync_file_range() are placed
   * under writeout.  This is a start-write-for-data-integrity operation.
   *
   * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
   * are not presently under writeout.  This is an asynchronous flush-to-disk
   * operation.  Not suitable for data integrity operations.
   *
   * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
   * completion of writeout of all pages in the range.  This will be used after an
   * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
   * for that operation to complete and to return the result.
   *
   * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
   * a traditional sync() operation.  This is a write-for-data-integrity operation
   * which will ensure that all pages in the range which were dirty on entry to
   * sys_sync_file_range() are committed to disk.
   *
   *
   * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
   * I/O errors or ENOSPC conditions and will return those to the caller, after
   * clearing the EIO and ENOSPC flags in the address_space.
   *
   * It should be noted that none of these operations write out the file's
   * metadata.  So unless the application is strictly performing overwrites of
   * already-instantiated disk blocks, there are no guarantees here that the data
   * will be available after a crash.
   */

  SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
  				unsigned int flags)

  {
  	int ret;
  	struct file *file;
  	loff_t endbyte;			/* inclusive */
  	int fput_needed;
  	umode_t i_mode;
  
  	ret = -EINVAL;
  	if (flags & ~VALID_FLAGS)
  		goto out;
  
  	endbyte = offset + nbytes;
  
  	if ((s64)offset < 0)
  		goto out;
  	if ((s64)endbyte < 0)
  		goto out;
  	if (endbyte < offset)
  		goto out;
  
  	if (sizeof(pgoff_t) == 4) {
  		if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
  			/*
  			 * The range starts outside a 32 bit machine's
  			 * pagecache addressing capabilities.  Let it "succeed"
  			 */
  			ret = 0;
  			goto out;
  		}
  		if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
  			/*
  			 * Out to EOF
  			 */
  			nbytes = 0;
  		}
  	}
  
  	if (nbytes == 0)

  		endbyte = LLONG_MAX;

  	else
  		endbyte--;		/* inclusive */
  
  	ret = -EBADF;
  	file = fget_light(fd, &fput_needed);
  	if (!file)
  		goto out;

  	i_mode = file->f_path.dentry->d_inode->i_mode;

  	ret = -ESPIPE;
  	if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
  			!S_ISLNK(i_mode))
  		goto out_put;

  	ret = do_sync_mapping_range(file->f_mapping, offset, endbyte, flags);

  out_put:
  	fput_light(file, fput_needed);
  out:
  	return ret;
  }

  #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
  asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
  				    long flags)
  {
  	return SYSC_sync_file_range((int) fd, offset, nbytes,
  				    (unsigned int) flags);
  }
  SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
  #endif

  /* It would be nice if people remember that not all the world's an i386
     when they introduce new system calls */

  SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
  				 loff_t offset, loff_t nbytes)

  {
  	return sys_sync_file_range(fd, offset, nbytes, flags);
  }

  #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
  asmlinkage long SyS_sync_file_range2(long fd, long flags,
  				     loff_t offset, loff_t nbytes)
  {
  	return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
  				     offset, nbytes);
  }
  SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
  #endif

  /*
   * `endbyte' is inclusive
   */

  int do_sync_mapping_range(struct address_space *mapping, loff_t offset,
  			  loff_t endbyte, unsigned int flags)

  {
  	int ret;

  	if (!mapping) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	ret = 0;
  	if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
  		ret = wait_on_page_writeback_range(mapping,
  					offset >> PAGE_CACHE_SHIFT,
  					endbyte >> PAGE_CACHE_SHIFT);
  		if (ret < 0)
  			goto out;
  	}
  
  	if (flags & SYNC_FILE_RANGE_WRITE) {
  		ret = __filemap_fdatawrite_range(mapping, offset, endbyte,

  						WB_SYNC_ALL);

  		if (ret < 0)
  			goto out;
  	}
  
  	if (flags & SYNC_FILE_RANGE_WAIT_AFTER) {
  		ret = wait_on_page_writeback_range(mapping,
  					offset >> PAGE_CACHE_SHIFT,
  					endbyte >> PAGE_CACHE_SHIFT);
  	}
  out:
  	return ret;
  }

  EXPORT_SYMBOL_GPL(do_sync_mapping_range);