On Tue, Jan 12, 2021 at 11:39:58AM -0700, Andreas Dilger wrote: > > XFS already has a XFS_IOC_ALLOCSP64 that is defined to actually > > allocate written extents. It does not currently use > > blkdev_issue_zeroout, but could be changed pretty trivially to do so. > > > >> But note it will need to be plumbed down to md and dm to be generally > >> useful. > > > > DM and MD already support mddev_check_write_zeroes, at least for the > > usual targets. > > Similarly, ext4 also has EXT4_GET_BLOCKS_CREATE_ZERO that can allocate zero > filled extents rather than unwritten extents (without clobbering existing > data like FALLOC_FL_ZERO_RANGE does), and just needs a flag from fallocate() > to trigger it. This is plumbed down to blkdev_issue_zeroout() as well. XFS_IOC_ALLOCSP64 actually is an ioctl that has been around since 1995 on IRIX (as an fcntl).
