>>>>> "Mike" == Mike Snitzer <snitzer@xxxxxxxxxx> writes: Mike, Mike> OK, so is MD somehow getting things wrong? (You originally said Mike> that with the new stacking function MD resulted in an error but DM Mike> did not). MD is passing in absolute offsets and got the right result in both cases. Mike> "start" isn't a relative offset. It's relative to the beginning of the partition (block_device), not relative to the beginning of the disk (request_queue). My beef here is that DM created a device like this: [root@10 ~]# pvs -o +pe_start PV VG Fmt Attr PSize PFree 1st PE /dev/sde1 foo lvm2 a- 508.00M 256.00M 192.00K /dev/sde2 foo lvm2 a- 512.00M 260.00M 192.00K [root@10 ~]# dmsetup table foo-bar: 0 1032192 striped 2 32 8:66 384 8:65 384 /dev/sde has an alignment_offset of 3584 /dev/sde1 has an alignment_offset of 0 /dev/sde2 has an alignment_offset of 1024 dm_set_device_limits() calls blk_stack_limits() with a byte offset of 196608 for both sde1 and sde2. And that offset is checked for alignment with the queue's limits which has an alignment_offset of 3584. The two PVs are misaligned but that information is lost because you use blk_stack_limits() with partition-relative offsets. My patch was an attempt to fix that. Test case: # modprobe scsi_debug dev_size_mb=1024 num_parts=2 lowest_aligned=7 physblk_exp=3 # pvcreate /dev/sde1 # pvcreate /dev/sde2 # vgcreate foo /dev/sde1 /dev/sde2 # lvcreate -I 16 -i 2 -L 500M -n bar foo -- Martin K. Petersen Oracle Linux Engineering -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
