/*
   *  linux/fs/ext3/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
   *
   *  ext3fs 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/blkdev.h>
  #include <linux/writeback.h>
  #include "ext3.h"
  
  /*
   * akpm: A new design for ext3_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 ext3_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
  {
  	struct inode *inode = file->f_mapping->host;
  	struct ext3_inode_info *ei = EXT3_I(inode);
  	journal_t *journal = EXT3_SB(inode->i_sb)->s_journal;
  	int ret, needs_barrier = 0;
  	tid_t commit_tid;
  
  	trace_ext3_sync_file_enter(file, datasync);
  
  	if (inode->i_sb->s_flags & MS_RDONLY) {
  		/* Make sure that we read updated state */
  		smp_rmb();
  		if (EXT3_SB(inode->i_sb)->s_mount_state & EXT3_ERROR_FS)
  			return -EROFS;
  		return 0;
  	}
  	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
  	if (ret)
  		goto out;
  
  	J_ASSERT(ext3_journal_current_handle() == NULL);
  
  	/*
  	 * data=writeback,ordered:
  	 *  The caller's filemap_fdatawrite()/wait will sync the data.
  	 *  Metadata is in the journal, we wait for a proper transaction
  	 *  to commit here.
  	 *
  	 * data=journal:
  	 *  filemap_fdatawrite won't do anything (the buffers are clean).
  	 *  ext3_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 (ext3_should_journal_data(inode)) {
  		ret = ext3_force_commit(inode->i_sb);
  		goto out;
  	}
  
  	if (datasync)
  		commit_tid = atomic_read(&ei->i_datasync_tid);
  	else
  		commit_tid = atomic_read(&ei->i_sync_tid);
  
  	if (test_opt(inode->i_sb, BARRIER) &&
  	    !journal_trans_will_send_data_barrier(journal, commit_tid))
  		needs_barrier = 1;
  	log_start_commit(journal, commit_tid);
  	ret = log_wait_commit(journal, commit_tid);
  
  	/*
  	 * In case we didn't commit a transaction, we have to flush
  	 * disk caches manually so that data really is on persistent
  	 * storage
  	 */
  	if (needs_barrier) {
  		int err;
  
  		err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
  		if (!ret)
  			ret = err;
  	}
  out:
  	trace_ext3_sync_file_exit(inode, ret);
  	return ret;
  }