Hi, Is BLKZEROOUT ioctl supposed to work on dm devices ? When I try this ioctl on an LV that sits on a WRITE SAME capable SCSI device, I see that conventional zeroing is done since the WRITE SAME support isn't advertised by the dm device. # lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 50G 0 disk └─mpathb (dm-12) 252:12 0 50G 0 mpath └─ws_vg-lvol0 (dm-11) 252:11 0 1G 0 lvm sde 8:64 0 50G 0 disk └─mpathb (dm-12) 252:12 0 50G 0 mpath └─ws_vg-lvol0 (dm-11) 252:11 0 1G 0 lvm # cat /sys/block/sda/queue/write_same_max_bytes 268435456 # cat /sys/block/dm-12/queue/write_same_max_bytes 0 # cat /sys/block/dm-11/queue/write_same_max_bytes 0 [root@llmvm02 ~]# cat /sys/dev/block/8\:0/queue/write_same_max_bytes 268435456 [root@llmvm02 ~]# cat /sys/dev/block/252\:12/queue/write_same_max_bytes 0 [root@llmvm02 ~]# cat /sys/dev/block/252\:11/queue/write_same_max_bytes 0 >From commit d54eaa5a0fde0a202e4e91f200f818edcef15bee, I gather that WRITE SAME is advertised by a dm device if all of its target and underlying devices support WRITE SAME. Also as per 4f0b70b0479101522b8645ddc1f5ee7137821db3, WRITE SAME is supported for linear dm devices. Both of these seem to be true in my case, but still BLKZEROOUT ioctl resorts to conventional zeroing. What am I missing here ? Regards, Bharata. -- http://raobharata.wordpress.com/ -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
