/*
   *  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;
  }
  
  /*
   * 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.
   */
  
  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 = 0, err;
  	tid_t commit_tid;
  	bool needs_barrier = false;
  
  	J_ASSERT(ext4_journal_current_handle() == NULL);
  
  	trace_ext4_sync_file_enter(file, datasync);
  
  	if (inode->i_sb->s_flags & MS_RDONLY) {
  		/* Make sure that we read updated s_mount_flags value */
  		smp_rmb();
  		if (EXT4_SB(inode->i_sb)->s_mount_flags & EXT4_MF_FS_ABORTED)
  			ret = -EROFS;
  		goto out;
  	}
  
  	if (!journal) {
  		ret = generic_file_fsync(file, start, end, datasync);
  		if (!ret && !hlist_empty(&inode->i_dentry))
  			ret = ext4_sync_parent(inode);
  		goto out;
  	}
  
  	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
  	if (ret)
  		return ret;
  	/*
  	 * 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;
  	ret = jbd2_complete_transaction(journal, commit_tid);
  	if (needs_barrier) {
  		err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
  		if (!ret)
  			ret = err;
  	}
  out:
  	trace_ext4_sync_file_exit(inode, ret);
  	return ret;
  }