On 10/11/13 10:14 AM, Emil Karlson wrote: >> If the filesystem is clever enough to know that the range in question has >> not been written to since the last discard, then it takes no action, and >> reports zero bytes. > > File system images can be rewritten on a new media so there is a > drawback to that. It's in-memory for the mounted filesystem, not on disk. It checks the EXT4_GROUP_INFO_WAS_TRIMMED_BIT flag stored in bb_state in the ext4_group_info structure. So when you mount a dd'd copy, it takes a fresh look, and DTRT. -Eric > Best Regards > -Emil > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
