On Mon, Sep 2, 2019 at 12:04 AM Yufen Yu <yuyufen@xxxxxxxxxx> wrote:
>
> We have a test case as follow:
>
> mdadm -CR /dev/md1 -l 1 -n 4 /dev/sd[a-d] --assume-clean --bitmap=internal
> mdadm -S /dev/md1
> mdadm -A /dev/md1 /dev/sd[b-c] --run --force
>
> mdadm --zero /dev/sda
> mdadm /dev/md1 -a /dev/sda
>
> echo offline > /sys/block/sdc/device/state
> echo offline > /sys/block/sdb/device/state
> sleep 5
> mdadm -S /dev/md1
>
> echo running > /sys/block/sdb/device/state
> echo running > /sys/block/sdc/device/state
> mdadm -A /dev/md1 /dev/sd[a-c] --run --force
>
> When we readd /dev/sda to the array, it started to do recovery.
> After offline the other two disks in md1, the recovery have
> been interrupted and superblock update info cannot be written
> to the offline disks. While the spare disk (/dev/sda) can continue
> to update superblock info.
>
> After stopping the array and assemble it, we found the array
> run fail, with the follow kernel message:
>
> [ 172.986064] md: kicking non-fresh sdb from array!
> [ 173.004210] md: kicking non-fresh sdc from array!
> [ 173.022383] md/raid1:md1: active with 0 out of 4 mirrors
> [ 173.022406] md1: failed to create bitmap (-5)
> [ 173.023466] md: md1 stopped.
>
> Since both sdb and sdc have the value of 'sb->events' smaller than
> that in sda, they have been kicked from the array. However, the only
> remained disk sda is in 'spare' state before stop and it cannot be
> added to conf->mirrors[] array. In the end, raid array assemble and run fail.
>
> In fact, we can use the older disk sdb or sdc to assemble the array.
> That means we should not choose the 'spare' disk as the fresh disk in
> analyze_sbs().
>
> To fix the problem, we do not compare superblock events when it is
> a spare disk, as same as validate_super.
>
> Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx>
> ---
> drivers/md/md.c | 27 +++++++++++++++++----------
> 1 file changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 24638ccedce4..350e1f152e97 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -1092,7 +1092,7 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor
> {
> char b[BDEVNAME_SIZE], b2[BDEVNAME_SIZE];
> mdp_super_t *sb;
> - int ret;
> + int ret = 0;
>
> /*
> * Calculate the position of the superblock (512byte sectors),
> @@ -1160,10 +1160,13 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor
> }
> ev1 = md_event(sb);
> ev2 = md_event(refsb);
> - if (ev1 > ev2)
> - ret = 1;
> - else
> - ret = 0;
> +
> + /* Insist on good event counter while assembling, except
> + * for spares (which don't need an event count) */
> + if (sb->disks[rdev->desc_nr].state & (
> + (1<<MD_DISK_SYNC) | (1 << MD_DISK_ACTIVE)))
> + if (ev1 > ev2)
> + ret = 1;
Instead of skipping the test, I guess we should make sure refsb passes
a non-spare sb?
In other words, we should fix the refdev of the super_*_load function.
Does this make sense?
Thanks,
Song
