/*
   * 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>

  #include "internal.h"

  
  #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
  			SYNC_FILE_RANGE_WAIT_AFTER)

  /*

   * Do the filesystem syncing work. For simple filesystems
   * writeback_inodes_sb(sb) just dirties buffers with inodes so we have to
   * submit IO for these buffers via __sync_blockdev(). This also speeds up the
   * wait == 1 case since in that case write_inode() functions do
   * sync_dirty_buffer() and thus effectively write one block at a time.

   */

  static int __sync_filesystem(struct super_block *sb, int wait)

  {

  	/*
  	 * This should be safe, as we require bdi backing to actually
  	 * write out data in the first place
  	 */
  	if (!sb->s_bdi)
  		return 0;

  	if (sb->s_qcop && sb->s_qcop->quota_sync)
  		sb->s_qcop->quota_sync(sb, -1, wait);
  
  	if (wait)

  		sync_inodes_sb(sb);

  	else
  		writeback_inodes_sb(sb);

  	if (sb->s_op->sync_fs)
  		sb->s_op->sync_fs(sb, wait);
  	return __sync_blockdev(sb->s_bdev, wait);
  }
  
  /*
   * Write out and wait upon all dirty data associated with this
   * superblock.  Filesystem data as well as the underlying block
   * device.  Takes the superblock lock.
   */

  int sync_filesystem(struct super_block *sb)

  {
  	int ret;

  	/*
  	 * We need to be protected against the filesystem going from
  	 * r/o to r/w or vice versa.
  	 */
  	WARN_ON(!rwsem_is_locked(&sb->s_umount));
  
  	/*
  	 * No point in syncing out anything if the filesystem is read-only.
  	 */
  	if (sb->s_flags & MS_RDONLY)
  		return 0;

  	ret = __sync_filesystem(sb, 0);

  	if (ret < 0)
  		return ret;

  	return __sync_filesystem(sb, 1);

  }

  EXPORT_SYMBOL_GPL(sync_filesystem);

  
  /*
   * Sync all the data for all the filesystems (called by sys_sync() and
   * emergency sync)
   *
   * This operation is careful to avoid the livelock which could easily happen
   * if two or more filesystems are being continuously dirtied.  s_need_sync
   * is used only here.  We set it against all filesystems and then clear it as
   * we sync them.  So redirtied filesystems are skipped.
   *
   * But if process A is currently running sync_filesystems and then process B
   * calls sync_filesystems as well, process B will set all the s_need_sync
   * flags again, which will cause process A to resync everything.  Fix that with
   * a local mutex.
   */
  static void sync_filesystems(int wait)
  {
  	struct super_block *sb;
  	static DEFINE_MUTEX(mutex);
  
  	mutex_lock(&mutex);		/* Could be down_interruptible */
  	spin_lock(&sb_lock);

  	list_for_each_entry(sb, &super_blocks, s_list)

  		sb->s_need_sync = 1;

  
  restart:
  	list_for_each_entry(sb, &super_blocks, s_list) {
  		if (!sb->s_need_sync)
  			continue;
  		sb->s_need_sync = 0;

  		sb->s_count++;
  		spin_unlock(&sb_lock);

  		down_read(&sb->s_umount);

  		if (!(sb->s_flags & MS_RDONLY) && sb->s_root && sb->s_bdi)

  			__sync_filesystem(sb, wait);

  		up_read(&sb->s_umount);

  		/* restart only when sb is no longer on the list */
  		spin_lock(&sb_lock);
  		if (__put_super_and_need_restart(sb))
  			goto restart;
  	}
  	spin_unlock(&sb_lock);
  	mutex_unlock(&mutex);
  }

  /*
   * sync everything.  Start out by waking pdflush, because that writes back
   * all queues in parallel.
   */

  SYSCALL_DEFINE0(sync)

  {

  	wakeup_flusher_threads(0);

  	sync_filesystems(0);
  	sync_filesystems(1);

  	if (unlikely(laptop_mode))
  		laptop_sync_completion();

  	return 0;
  }

  static void do_sync_work(struct work_struct *work)
  {

  	/*
  	 * Sync twice to reduce the possibility we skipped some inodes / pages
  	 * because they were temporarily locked
  	 */
  	sync_filesystems(0);
  	sync_filesystems(0);
  	printk("Emergency Sync complete
  ");

  	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;

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

  		sb->s_op->write_super(sb);

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

  EXPORT_SYMBOL(file_fsync);

  /**

   * vfs_fsync_range - helper to sync a range of data & metadata to disk

   * @file:		file to sync
   * @dentry:		dentry of @file

   * @start:		offset in bytes of the beginning of data range to sync
   * @end:		offset in bytes of the end of data range (inclusive)
   * @datasync:		perform only datasync

   *

   * Write back data in range @start..@end 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_range(struct file *file, struct dentry *dentry, loff_t start,
  		    loff_t end, 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_write_and_wait_range(mapping, start, end);

  
  	/*
  	 * 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);

  out:
  	return ret;
  }

  EXPORT_SYMBOL(vfs_fsync_range);
  
  /**
   * vfs_fsync - perform a fsync or fdatasync on a file
   * @file:		file to sync
   * @dentry:		dentry of @file
   * @datasync:		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)
  {
  	return vfs_fsync_range(file, dentry, 0, LLONG_MAX, datasync);
  }

  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);

  }

  /**
   * generic_write_sync - perform syncing after a write if file / inode is sync
   * @file:	file to which the write happened
   * @pos:	offset where the write started
   * @count:	length of the write
   *
   * This is just a simple wrapper about our general syncing function.
   */
  int generic_write_sync(struct file *file, loff_t pos, loff_t count)
  {

  	if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))

  		return 0;
  	return vfs_fsync_range(file, file->f_path.dentry, pos,

  			       pos + count - 1,
  			       (file->f_flags & __O_SYNC) ? 0 : 1);

  }
  EXPORT_SYMBOL(generic_write_sync);

  /*

   * 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;

  	struct address_space *mapping;

  	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;

  	mapping = file->f_mapping;
  	if (!mapping) {
  		ret = -EINVAL;
  		goto out_put;
  	}
  
  	ret = 0;
  	if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
  		ret = filemap_fdatawait_range(mapping, offset, endbyte);
  		if (ret < 0)
  			goto out_put;
  	}
  
  	if (flags & SYNC_FILE_RANGE_WRITE) {
  		ret = filemap_fdatawrite_range(mapping, offset, endbyte);
  		if (ret < 0)
  			goto out_put;
  	}
  
  	if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
  		ret = filemap_fdatawait_range(mapping, offset, endbyte);

  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