ext4: use generic_file_fsync() in ext4_file_fsync() in nojournal mode

Just use the generic function instead of duplicating it.  We only need
to reshuffle the read-only check a bit (which is there to prevent
writing to a filesystem which has been remounted read-only after error
I assume).
Reviewed-by: NZheng Liu <wenqing.lz@taobao.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/fsync.c

@@ -73,32 +73,6 @@ static int ext4_sync_parent(struct inode *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().
  *
@@ -116,7 +90,7 @@ 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;
+	int ret = 0, err;
 	tid_t commit_tid;
 	bool needs_barrier = false;
 
@@ -124,21 +98,21 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 
 	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;
+		goto out_trace;
 
 	if (!journal) {
-		ret = __sync_inode(inode, datasync);
+		ret = generic_file_fsync(file, start, end, datasync);
 		if (!ret && !hlist_empty(&inode->i_dentry))
 			ret = ext4_sync_parent(inode);
-		goto out;
+		goto out_trace;
 	}
 
+	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	if (ret)
+		return ret;
+	mutex_lock(&inode->i_mutex);
+
 	/*
 	 * data=writeback,ordered:
 	 *  The caller's filemap_fdatawrite()/wait will sync the data.
@@ -168,8 +142,9 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 		if (!ret)
 			ret = err;
 	}
- out:
+out:
 	mutex_unlock(&inode->i_mutex);
+out_trace:
 	trace_ext4_sync_file_exit(inode, ret);
 	return ret;
 }