On Fri, Sep 21, 2018 at 5:51 AM Guoqing Jiang <gqjiang@xxxxxxxx> wrote: > > > > On 9/20/18 9:36 PM, Gi-Oh Kim wrote: > > On Wed, Sep 19, 2018 at 5:09 PM Gi-Oh Kim <gi-oh.kim@xxxxxxxxxxxxxxxx> wrote: > > Hi, > > I found a weird behavior of re-adding a device. > I think it is a kernel bug. > I would appreciate it if somebody can confirm if it is a bug or feature. > > I tested re-adding a device as following. > 1. create md with ram0 and ram1 > 2. add ram2 > 3. grow raid-device number to 3 > 4. remove ram2 > 5. grow raid-device number to 2 > 6. add ram2 > 7. ram0 become faulty and ram2 become active > 8. stop md > 9. assemble md with ram0 and ram1 => fail because ram0 is faulty > > Hi, > > I checked the kernel function raid1_spare_active() in raid1.c and > found out ram0 is set as faulty on purpose. > If ram0 is set as fauly to replace it with ram2, i think it should be > successful to assemble ram1 and ram2. > But "mdadm -A /dev/md111 /dev/ram1 /dev/ram2" creates md111 with only ram2. > I do not understand why it is necessary to set ram0 faulty. > > > When ram2 is add back to array, seems array prefers to use the previous role > which is recorded by saved_raid_disk. > > How can I re-add ram2 device as the spare device without setting ram0 faulty? > > > I guess you can achieve the goal by remove the superblock of ram2 (before step 6). > BTW, could you try the below change? I think it can fix the issue. Yes, I think so. But I think it would be better to set ram0 as spare, not faulty. And another problem is "mdadm -A /dev/md111 /dev/ram1 /dev/ram2" does not work well. ram1 does not assembled to md111. If ram0 should be faulty, I think assembling ram1 and ram2 should work. > > diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c > index 4e990246225e..1d54109071cc 100644 > --- a/drivers/md/raid1.c > +++ b/drivers/md/raid1.c > @@ -1734,6 +1734,7 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev) > */ > if (rdev->saved_raid_disk >= 0 && > rdev->saved_raid_disk >= first && > + rdev->saved_raid_disk < conf->raid_disks && > conf->mirrors[rdev->saved_raid_disk].rdev == NULL) > first = last = rdev->saved_raid_disk; > > > > Thanks, > Guoqing -- GIOH KIM Linux Kernel Entwickler ProfitBricks GmbH Greifswalder Str. 207 D - 10405 Berlin Tel: +49 176 2697 8962 Fax: +49 30 577 008 299 Email: gi-oh.kim@xxxxxxxxxxxxxxxx URL: https://www.profitbricks.de Sitz der Gesellschaft: Berlin Registergericht: Amtsgericht Charlottenburg, HRB 125506 B Geschäftsführer: Achim Weiss, Matthias Steinberg, Christoph Steffens
