Hi Neil When testing 07revert-grow, found the RAID4/5/6 grow stuck issue, pls check below info: Steps: mdadm --quiet -CR --assume-clean /dev/md0 -l6 -n4 -x1 /dev/loop0 /dev/loop1 /dev/loop2 /dev/loop3 /dev/loop4 sleep 3 mdadm --wait /dev/md0 mdadm -G /dev/md0 -n 5 [root@dhcp-12-171 bug]# cat /proc/mdstat Personalities : [raid6] [raid5] [raid4] md0 : active raid6 loop4[4] loop3[3] loop2[2] loop1[1] loop0[0] 38912 blocks super 1.2 level 6, 512k chunk, algorithm 2 [5/5] [UUUUU] [>....................] reshape = 0.0% (0/19456) finish=3344.0min speed=0K/sec unused devices: <none> kernel: 4.2.0 dmesg: [ 563.248753] md: bind<loop0> [ 563.248825] md: bind<loop1> [ 563.248892] md: bind<loop2> [ 563.248954] md: bind<loop3> [ 563.251515] md: bind<loop4> [ 563.257778] md/raid:md0: device loop3 operational as raid disk 3 [ 563.257784] md/raid:md0: device loop2 operational as raid disk 2 [ 563.257787] md/raid:md0: device loop1 operational as raid disk 1 [ 563.257789] md/raid:md0: device loop0 operational as raid disk 0 [ 563.258543] md/raid:md0: allocated 4366kB [ 563.258613] md/raid:md0: raid level 6 active with 4 out of 4 devices, algorithm 2 [ 563.258617] RAID conf printout: [ 563.258621] --- level:6 rd:4 wd:4 [ 563.258624] disk 0, o:1, dev:loop0 [ 563.258628] disk 1, o:1, dev:loop1 [ 563.258632] disk 2, o:1, dev:loop2 [ 563.258634] disk 3, o:1, dev:loop3 [ 563.258651] md/raid456: discard support disabled due to uncertainty. [ 563.258653] Set raid456.devices_handle_discard_safely=Y to override. [ 563.258694] md0: detected capacity change from 0 to 39845888 [ 563.258814] RAID conf printout: [ 563.258821] --- level:6 rd:4 wd:4 [ 563.258825] disk 0, o:1, dev:loop0 [ 563.258829] disk 1, o:1, dev:loop1 [ 563.258833] disk 2, o:1, dev:loop2 [ 563.258838] disk 3, o:1, dev:loop3 [ 566.566752] RAID conf printout: [ 566.566758] --- level:6 rd:5 wd:5 [ 566.566762] disk 0, o:1, dev:loop0 [ 566.566765] disk 1, o:1, dev:loop1 [ 566.566767] disk 2, o:1, dev:loop2 [ 566.566770] disk 3, o:1, dev:loop3 [ 566.566772] disk 4, o:1, dev:loop4 [ 566.567770] md: reshape of RAID array md0 [ 566.567776] md: minimum _guaranteed_ speed: 1000 KB/sec/disk. [ 566.567779] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reshape. [ 566.567785] md: using 128k window, over a total of 19456k Best Regards, Yi Zhang -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html