On Mon, Jul 14, 2014 at 08:27:26PM +0400, Dmitry Monakhov wrote: > Actually they are differ. EXT4_IOC_MOVE_EXT copy data inside kernel, > but XFS_IOC_SWAPEXT live this job to userpsace see: > http://oss.sgi.com/cgi-bin/gitweb.cgi?p=xfs/cmds/xfsprogs.git;a=blob;f=fsr/xfs_fsr.c packfile > And I'll vote to make EXT4_IOC_MOVE_EXT deprecated, and implement EXT4_IOC_SWAPEXT > as XFS does that. > Ted, Lukas what do you think about that? The reason why EXT4_IOC_MOVE_EXT moves the data via the cache is to avoid being subject to races if the file happens to mmap'ed and being actively modified at the time of the defrag operation. I'm not sure how XFS handles that case, but if it's not somehow locking the file against mmap's before it starts the userspace copy, it would seem to me to be fairly dangerous in terms of prevent potential data loss in this scenario. Unless they are doing some especially clever? Regards, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
