drbd: Take a more conservative approach when deciding max_bio_size

The old (optimistic) implementation could shrink the bio size
on an primary device.

Shrinking the bio size on a primary device is bad. Since there
we might get BIOs with the old (bigger) size shortly after
we published the new size.

The new implementation is more conservative, and eventually
increases the max_bio_size on a primary device (which is valid).
It does so, when it knows the local limit AND the remote limit.

 We cache the last seen max_bio_size of the peer in the meta
 data, and rely on that, to make the operation of single
 nodes more efficient.

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

1 files changed, 3 insertions, 17 deletions

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index b0b0ba345e8..6ea0a4b51ec 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -899,11 +899,6 @@ retry:
 
         drbd_thread_start(&mdev->asender);
 
-        if (mdev->agreed_pro_version < 95 && get_ldev(mdev)) {
-                drbd_setup_queue_param(mdev, DRBD_MAX_SIZE_H80_PACKET);
-                put_ldev(mdev);
-        }
-
         if (drbd_send_protocol(mdev) == -1)
                 return -1;
         drbd_send_sync_param(mdev, &mdev->sync_conf);
@@ -2939,7 +2934,6 @@ static int receive_sizes(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 {
         struct p_sizes *p = &mdev->data.rbuf.sizes;
         enum determine_dev_size dd = unchanged;
-        unsigned int max_bio_size;
         sector_t p_size, p_usize, my_usize;
         int ldsc = 0; /* local disk size changed */
         enum dds_flags ddsf;
@@ -3004,23 +2998,15 @@ static int receive_sizes(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
                 drbd_set_my_capacity(mdev, p_size);
         }
 
+        mdev->peer_max_bio_size = be32_to_cpu(p->max_bio_size);
+        drbd_reconsider_max_bio_size(mdev);
+
         if (get_ldev(mdev)) {
                 if (mdev->ldev->known_size != drbd_get_capacity(mdev->ldev->backing_bdev)) {
                         mdev->ldev->known_size = drbd_get_capacity(mdev->ldev->backing_bdev);
                         ldsc = 1;
                 }
 
-                if (mdev->agreed_pro_version < 94)
-                        max_bio_size = be32_to_cpu(p->max_bio_size);
-                else if (mdev->agreed_pro_version == 94)
-                        max_bio_size = DRBD_MAX_SIZE_H80_PACKET;
-                else /* drbd 8.3.8 onwards */
-                        max_bio_size = DRBD_MAX_BIO_SIZE;
-
-                if (max_bio_size != queue_max_hw_sectors(mdev->rq_queue) << 9)
-                        drbd_setup_queue_param(mdev, max_bio_size);
-
-                drbd_setup_order_type(mdev, be16_to_cpu(p->queue_order_type));
                 put_ldev(mdev);
         }