drbd: allow write-ordering policy to be bumped up again

Previously, once you disabled flushes as a means of enforcing
write-ordering, you'd need to detach/re-attach to enable them again.

Allow drbdsetup disk-options to re-enable previously disabled
write-ordering policy options at runtime.

While at it fix RCU in drbd_bump_write_ordering()
max_allowed_wo() uses rcu_dereference, therefore it must
be called within rcu_read_lock()/rcu_read_unlock()

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 0bf8a6082bb843b0838f00a0aab067a4555427a2..66065e60fdbcb4084a77d8c471093113e9502092 100644 (file)
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1294,6 +1294,13 @@ static unsigned int drbd_al_extents_max(struct drbd_backing_dev *bdev)
        return (al_size_4k - 1) * AL_CONTEXT_PER_TRANSACTION;
 }
 
+static bool write_ordering_changed(struct disk_conf *a, struct disk_conf *b)
+{
+       return  a->disk_barrier != b->disk_barrier ||
+               a->disk_flushes != b->disk_flushes ||
+               a->disk_drain != b->disk_drain;
+}
+
 int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
 {
        struct drbd_config_context adm_ctx;
@@ -1400,7 +1407,8 @@ int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
        else
                set_bit(MD_NO_FUA, &device->flags);
 
-       drbd_bump_write_ordering(device->resource, NULL, WO_bdev_flush);
+       if (write_ordering_changed(old_disk_conf, new_disk_conf))
+               drbd_bump_write_ordering(device->resource, NULL, WO_bdev_flush);
 
        drbd_md_sync(device);
 

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index bb1434dfec8ad6c3f70a601acbfb58eb6731b77a..8d8a6b7f8f5d7cb72c2652316e6cf95c961770e6 100644 (file)
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1290,7 +1290,8 @@ void drbd_bump_write_ordering(struct drbd_resource *resource, struct drbd_backin
        };
 
        pwo = resource->write_ordering;
-       wo = min(pwo, wo);
+       if (wo != WO_bdev_flush)
+               wo = min(pwo, wo);
        rcu_read_lock();
        idr_for_each_entry(&resource->devices, device, vnr) {
                if (get_ldev(device)) {
@@ -1300,11 +1301,12 @@ void drbd_bump_write_ordering(struct drbd_resource *resource, struct drbd_backin
                        put_ldev(device);
                }
        }
-       rcu_read_unlock();
 
        if (bdev)
                wo = max_allowed_wo(bdev, wo);
 
+       rcu_read_unlock();
+
        resource->write_ordering = wo;
        if (pwo != resource->write_ordering || wo == WO_bdev_flush)
                drbd_info(resource, "Method to ensure write ordering: %s\n", write_ordering_str[resource->write_ordering]);