drbd: transfer log epoch numbers are now per resource

cherry-picked from drbd 9 devel branch.

In preparation of multiple connections, the "barrier number" or
"epoch number" needs to be tracked per-resource, not per connection.
The sequence number space will not be reset anymore.

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

3 files changed, 6 insertions, 8 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 5b1789af6cdf..d7ca76ce00cb 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -864,6 +864,7 @@ struct drbd_tconn {			/* is a resource from the config file */
         spinlock_t epoch_lock;
         unsigned int epochs;
         enum write_ordering_e write_ordering;
+        atomic_t current_tle_nr;        /* transfer log epoch number */
 
         unsigned long last_reconnect_jif;
         struct drbd_thread receiver;
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 843d0af68f96..bfe6975ef94c 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -208,7 +208,7 @@ static int tl_init(struct drbd_tconn *tconn)
         INIT_LIST_HEAD(&b->requests);
         INIT_LIST_HEAD(&b->w.list);
         b->next = NULL;
-        b->br_number = 4711;
+        b->br_number = atomic_inc_return(&tconn->current_tle_nr);
         b->n_writes = 0;
         b->w.cb = NULL; /* if this is != NULL, we need to dec_ap_pending in tl_clear */
 
@@ -241,16 +241,13 @@ static void tl_cleanup(struct drbd_tconn *tconn)
  */
 void _tl_add_barrier(struct drbd_tconn *tconn, struct drbd_tl_epoch *new)
 {
-        struct drbd_tl_epoch *newest_before;
-
         INIT_LIST_HEAD(&new->requests);
         INIT_LIST_HEAD(&new->w.list);
         new->w.cb = NULL; /* if this is != NULL, we need to dec_ap_pending in tl_clear */
         new->next = NULL;
         new->n_writes = 0;
 
-        newest_before = tconn->newest_tle;
-        new->br_number = newest_before->br_number+1;
+        new->br_number = atomic_inc_return(&tconn->current_tle_nr);
         if (tconn->newest_tle != new) {
                 tconn->newest_tle->next = new;
                 tconn->newest_tle = new;
@@ -406,7 +403,7 @@ void _tl_restart(struct drbd_tconn *tconn, enum drbd_req_event what)
                                 list_splice(&carry_reads, &b->requests);
                                 INIT_LIST_HEAD(&b->w.list);
                                 b->w.cb = NULL;
-                                b->br_number = net_random();
+                                b->br_number = atomic_inc_return(&tconn->current_tle_nr);
                                 b->n_writes = 0;
 
                                 *pn = b;
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 34e791dfaf81..a131174b6677 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -187,7 +187,7 @@ static void _about_to_complete_local_write(struct drbd_conf *mdev,
          */
         if (mdev->state.conn >= C_CONNECTED &&
             (s & RQ_NET_SENT) != 0 &&
-            req->epoch == mdev->tconn->newest_tle->br_number)
+            req->epoch == atomic_read(&mdev->tconn->current_tle_nr))
                 queue_barrier(mdev);
 }
 
@@ -518,7 +518,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                  * just after it grabs the req_lock */
                 D_ASSERT(test_bit(CREATE_BARRIER, &mdev->tconn->flags) == 0);
 
-                req->epoch = mdev->tconn->newest_tle->br_number;
+                req->epoch = atomic_read(&mdev->tconn->current_tle_nr);
 
                 /* increment size of current epoch */
                 mdev->tconn->newest_tle->n_writes++;