/*

   *  linux/fs/ext4/fsync.c

   *
   *  Copyright (C) 1993  Stephen Tweedie (sct@redhat.com)
   *  from
   *  Copyright (C) 1992  Remy Card (card@masi.ibp.fr)
   *                      Laboratoire MASI - Institut Blaise Pascal
   *                      Universite Pierre et Marie Curie (Paris VI)
   *  from
   *  linux/fs/minix/truncate.c   Copyright (C) 1991, 1992  Linus Torvalds
   *

   *  ext4fs fsync primitive

   *
   *  Big-endian to little-endian byte-swapping/bitmaps by
   *        David S. Miller (davem@caip.rutgers.edu), 1995
   *
   *  Removed unnecessary code duplication for little endian machines
   *  and excessive __inline__s.
   *        Andi Kleen, 1997
   *
   * Major simplications and cleanup - we only need to do the metadata, because
   * we can depend on generic_block_fdatasync() to sync the data blocks.
   */
  
  #include <linux/time.h>
  #include <linux/fs.h>
  #include <linux/sched.h>
  #include <linux/writeback.h>

  #include <linux/jbd2.h>

  #include <linux/blkdev.h>

  #include "ext4.h"
  #include "ext4_jbd2.h"

  #include <trace/events/ext4.h>

  /*

   * If we're not journaling and this is a just-created file, we have to
   * sync our parent directory (if it was freshly created) since
   * otherwise it will only be written by writeback, leaving a huge
   * window during which a crash may lose the file.  This may apply for
   * the parent directory's parent as well, and so on recursively, if
   * they are also freshly created.
   */

  static int ext4_sync_parent(struct inode *inode)

  {
  	struct dentry *dentry = NULL;

  	struct inode *next;

  	int ret = 0;

  	if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
  		return 0;
  	inode = igrab(inode);
  	while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {

  		ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);

  		dentry = d_find_any_alias(inode);

  		if (!dentry)

  			break;

  		next = igrab(dentry->d_parent->d_inode);
  		dput(dentry);
  		if (!next)
  			break;
  		iput(inode);
  		inode = next;

  		ret = sync_mapping_buffers(inode->i_mapping);
  		if (ret)
  			break;

  		ret = sync_inode_metadata(inode, 1);

  		if (ret)
  			break;

  	}

  	iput(inode);

  	return ret;

  }

  /**
   * __sync_file - generic_file_fsync without the locking and filemap_write
   * @inode:	inode to sync
   * @datasync:	only sync essential metadata if true
   *
   * This is just generic_file_fsync without the locking.  This is needed for
   * nojournal mode to make sure this inodes data/metadata makes it to disk
   * properly.  The i_mutex should be held already.
   */
  static int __sync_inode(struct inode *inode, int datasync)
  {
  	int err;
  	int ret;
  
  	ret = sync_mapping_buffers(inode->i_mapping);
  	if (!(inode->i_state & I_DIRTY))
  		return ret;
  	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
  		return ret;
  
  	err = sync_inode_metadata(inode, 1);
  	if (ret == 0)
  		ret = err;
  	return ret;
  }

  /*

   * akpm: A new design for ext4_sync_file().

   *
   * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
   * There cannot be a transaction open by this task.
   * Another task could have dirtied this inode.  Its data can be in any
   * state in the journalling system.
   *
   * What we do is just kick off a commit and wait on it.  This will snapshot the
   * inode to disk.

   *
   * i_mutex lock is held when entering and exiting this function

   */

  int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)

  {

  	struct inode *inode = file->f_mapping->host;

  	struct ext4_inode_info *ei = EXT4_I(inode);

  	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;

  	int ret, err;

  	tid_t commit_tid;

  	bool needs_barrier = false;

  	J_ASSERT(ext4_journal_current_handle() == NULL);

  	trace_ext4_sync_file_enter(file, datasync);

  	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
  	if (ret)
  		return ret;
  	mutex_lock(&inode->i_mutex);

  	if (inode->i_sb->s_flags & MS_RDONLY)

  		goto out;

  	ret = ext4_flush_unwritten_io(inode);

  	if (ret < 0)

  		goto out;

  	if (!journal) {

  		ret = __sync_inode(inode, datasync);

  		if (!ret && !hlist_empty(&inode->i_dentry))

  			ret = ext4_sync_parent(inode);

  		goto out;

  	}

  	/*

  	 * data=writeback,ordered:

  	 *  The caller's filemap_fdatawrite()/wait will sync the data.

  	 *  Metadata is in the journal, we wait for proper transaction to
  	 *  commit here.

  	 *
  	 * data=journal:
  	 *  filemap_fdatawrite won't do anything (the buffers are clean).

  	 *  ext4_force_commit will write the file data into the journal and

  	 *  will wait on that.
  	 *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
  	 *  (they were dirtied by commit).  But that's OK - the blocks are
  	 *  safe in-journal, which is all fsync() needs to ensure.
  	 */

  	if (ext4_should_journal_data(inode)) {
  		ret = ext4_force_commit(inode->i_sb);
  		goto out;
  	}

  	commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;

  	if (journal->j_flags & JBD2_BARRIER &&
  	    !jbd2_trans_will_send_data_barrier(journal, commit_tid))
  		needs_barrier = true;
  	jbd2_log_start_commit(journal, commit_tid);
  	ret = jbd2_log_wait_commit(journal, commit_tid);

  	if (needs_barrier) {
  		err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
  		if (!ret)
  			ret = err;
  	}

   out:

  	mutex_unlock(&inode->i_mutex);

  	trace_ext4_sync_file_exit(inode, ret);

  	return ret;
  }