On 2019/10/16 15:46, Song Liu wrote:
On Oct 16, 2019, at 1:00 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>
Please add "---" before "v1->v2:". etc. This will hint git to not
include these change lists during git-am.
OK
v1->v2:
fix wrong return value in super_90_load
v2->v3:
adjust the patch format to avoid scripts/checkpatch.pl warning
v3->v4:
fix the bug pointed out by Song, when the spare disk is the first
device for load_super
---
drivers/md/md.c | 57 +++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 51 insertions(+), 6 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 1be7abeb24fd..fc6ae8276a92 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1149,7 +1149,15 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor
rdev->desc_nr = sb->this_disk.number;
if (!refdev) {
- ret = 1;
+ /*
+ * 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)))
+ ret = 1;
+ else
+ ret = 0;
Have you tried only passing a couple spare disks to mdadm -A? I guess
we will end up with freshest == NULL in analyze_sbs(), which will
crash in validate_super().
Yes, freshest can be 'NULL'. So, I have added a test in analyze_sbs() in
the patch.
+ /* Cannot find a valid fresh disk */
+ if (!freshest) {
+ pr_warn("md: cannot find a valid disk\n");
+ return -EINVAL;
+ }
+
Thanks,
Yufen
