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SubjectRe: [DRBD-user] [PATCH] xen-blkback: Switch to closed state after releasing the backing device
On Fri, Sep 07, 2018 at 07:14:59PM +0200, Valentin Vidic wrote:
> In fact the first one is the original code path before I modified
> blkback. The problem is it gets executed async from workqueue so
> it might not always run before the call to drbdadm secondary.

As the DRBD device gets released only when the last IO request
has finished, I found a way to check and wait for this in the
block-drbd script:

--- block-drbd.orig 2018-09-08 09:07:23.499648515 +0200
+++ block-drbd 2018-09-08 09:28:12.892193649 +0200
@@ -230,6 +230,24 @@
and so cannot be mounted ${m2}${when}."
}

+wait_for_inflight()
+{
+ local dev="$1"
+ local inflight="/sys/block/${dev#/dev/}/inflight"
+ local rd wr
+
+ if ! [ -f "$inflight" ]; then
+ return
+ fi
+
+ while true; do
+ read rd wr < $inflight
+ if [ "$rd" = "0" -a "$wr" = "0" ]; then
+ return
+ fi
+ sleep 1
+ done
+}

t=$(xenstore_read_default "$XENBUS_PATH/type" 'MISSING')

@@ -285,6 +303,8 @@
drbd_lrole="${drbd_role%%/*}"
drbd_dev="$(drbdadm sh-dev $drbd_resource)"

+ wait_for_inflight $drbd_dev
+
if [ "$drbd_lrole" != 'Secondary' ]; then
drbdadm secondary $drbd_resource
fi
--
Valentin

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