----- Original Message ----- > From: "Xiao Ni" <xni@xxxxxxxxxx> > To: "NeilBrown" <neilb@xxxxxxx> > Cc: linux-raid@xxxxxxxxxxxxxxx > Sent: Thursday, May 21, 2015 11:37:57 AM > Subject: Re: raid5 reshape is stuck > > > > ----- Original Message ----- > > From: "NeilBrown" <neilb@xxxxxxx> > > To: "Xiao Ni" <xni@xxxxxxxxxx> > > Cc: linux-raid@xxxxxxxxxxxxxxx > > Sent: Thursday, May 21, 2015 7:48:37 AM > > Subject: Re: raid5 reshape is stuck > > > > On Fri, 15 May 2015 03:00:24 -0400 (EDT) Xiao Ni <xni@xxxxxxxxxx> wrote: > > > > > Hi Neil > > > > > > I encounter the problem when I reshape a 4-disks raid5 to raid5. It > > > just > > > can > > > appear with loop devices. > > > > > > The steps are: > > > > > > [root@dhcp-12-158 mdadm-3.3.2]# mdadm -CR /dev/md0 -l5 -n5 /dev/loop[0-4] > > > --assume-clean > > > mdadm: /dev/loop0 appears to be part of a raid array: > > > level=raid5 devices=6 ctime=Fri May 15 13:47:17 2015 > > > mdadm: /dev/loop1 appears to be part of a raid array: > > > level=raid5 devices=6 ctime=Fri May 15 13:47:17 2015 > > > mdadm: /dev/loop2 appears to be part of a raid array: > > > level=raid5 devices=6 ctime=Fri May 15 13:47:17 2015 > > > mdadm: /dev/loop3 appears to be part of a raid array: > > > level=raid5 devices=6 ctime=Fri May 15 13:47:17 2015 > > > mdadm: /dev/loop4 appears to be part of a raid array: > > > level=raid5 devices=6 ctime=Fri May 15 13:47:17 2015 > > > mdadm: Defaulting to version 1.2 metadata > > > mdadm: array /dev/md0 started. > > > [root@dhcp-12-158 mdadm-3.3.2]# mdadm /dev/md0 -a /dev/loop5 > > > mdadm: added /dev/loop5 > > > [root@dhcp-12-158 mdadm-3.3.2]# mdadm --grow /dev/md0 --raid-devices 6 > > > mdadm: Need to backup 10240K of critical section.. > > > [root@dhcp-12-158 mdadm-3.3.2]# cat /proc/mdstat > > > Personalities : [raid6] [raid5] [raid4] > > > md0 : active raid5 loop5[5] loop4[4] loop3[3] loop2[2] loop1[1] loop0[0] > > > 8187904 blocks super 1.2 level 5, 512k chunk, algorithm 2 [6/6] > > > [UUUUUU] > > > [>....................] reshape = 0.0% (0/2046976) > > > finish=6396.8min > > > speed=0K/sec > > > > > > unused devices: <none> > > > > > > It because the sync_max is set to 0 when run the command --grow > > > > > > [root@dhcp-12-158 mdadm-3.3.2]# cd /sys/block/md0/md/ > > > [root@dhcp-12-158 md]# cat sync_max > > > 0 > > > > > > I tried reproduce with normal sata devices. The progress of reshape is > > > no problem. Then > > > I checked the Grow.c. If I use sata devices, in function reshape_array, > > > the > > > return value > > > of set_new_data_offset is 0. But if I used loop devices, it return 1. > > > Then > > > it call the function > > > start_reshape. > > > > set_new_data_offset returns '0' if there is room on the devices to reduce > > the > > data offset so that the reshape starts writing to unused space on the > > array. > > This removes the need for a backup file, or the use of a spare device to > > store a temporary backup. > > It returns '1' if there was no room for relocating the data_offset. > > > > So on your sata devices (which are presumably larger than your loop > > devices) > > there was room. On your loop devices there was not. > > > > > > > > > > In the function start_reshape it set the sync_max to reshape_progress. > > > But in sysfs_read it > > > doesn't read reshape_progress. So it's 0 and the sync_max is set to 0. > > > Why > > > it need to set the > > > sync_max at this? I'm not sure about this. > > > > sync_max is set to 0 so that the reshape does not start until the backup > > has > > been taken. > > Once the backup is taken, child_monitor() should set sync_max to "max". > > > > Can you check if that is happening? > > > > Thanks, > > NeilBrown > > > > > > Thanks very much for the explaining. The problem maybe is fixed. I tried > reproduce this with newest > kernel and newest mdadm. Now the problem don't exist. I'll do more tests and > give the answer above later. > Hi Neil As you said, it doesn't enter child monitor. The problem still exist. The kernel version : [root@intel-canoepass-02 tmp]# uname -r 4.0.4 mdadm I used is the newest git code from git://git.neil.brown.name/mdadm.git In the function continue_via_systemd the parent find pid is bigger than 0 and status is 0. So it return 1. So it have no opportunity to call child_monitor. And if it want to set sync_max to 0 until the backup has been taken. Why does not set sync_max to 0 directly, but use the value reshape_progress? There is a little confused. Best Regards Xiao -- 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
