fs/ext4/ext4.h

1066 	 * i_disksize keeps track of what the inode size is ON DISK, not
1069 	 * set i_disksize to 0 until the truncate is actually under way.
1071 	 * The intent is that i_disksize always represents the blocks which
1073 	 * on orphans if we crash during truncate.  We actually write i_disksize
1076 	 * The only time when i_disksize and i_size may be different is when
1077 	 * a truncate is in progress.  The only things which change i_disksize
1080 	loff_t	i_disksize;
3378 /* Update i_disksize. Requires i_rwsem to avoid races with truncate */
3384 	if (newsize > EXT4_I(inode)->i_disksize)
3385 		WRITE_ONCE(EXT4_I(inode)->i_disksize, newsize);
3389 /* Update i_size, i_disksize. Requires i_rwsem to avoid races with truncate */
3398 	if (newsize > EXT4_I(inode)->i_disksize) {