drbd: Work on the Ahead -> SyncSource transition

The test if rs_pending_cnt == 0 was too weak. Using Test for
unacked_cnt == 0 instead. Moved that into the worker.

Since unacked_cnt gets already increased when an P_RS_DATA_REQ
comes in.

Also using a timer to make Ahead -> SyncSource -> Ahead cycles
slower...

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

4 files changed, 25 insertions, 6 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 3c8eecd9666d..cfe7fff459e3 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -850,6 +850,7 @@ enum {
         GOT_PING_ACK,           /* set when we receive a ping_ack packet, misc wait gets woken */
         NEW_CUR_UUID,           /* Create new current UUID when thawing IO */
         AL_SUSPENDED,           /* Activity logging is currently suspended. */
+        AHEAD_TO_SYNC_SOURCE,   /* Ahead -> SyncSource queued */
 };
 
 struct drbd_bitmap; /* opaque for drbd_conf */
@@ -961,6 +962,7 @@ struct drbd_conf {
                           start_resync_work;
         struct timer_list resync_timer;
         struct timer_list md_sync_timer;
+        struct timer_list start_resync_timer;
 #ifdef DRBD_DEBUG_MD_SYNC
         struct {
                 unsigned int line;
@@ -1544,6 +1546,7 @@ extern int w_send_oos(struct drbd_conf *, struct drbd_work *, int);
 extern int w_start_resync(struct drbd_conf *, struct drbd_work *, int);
 
 extern void resync_timer_fn(unsigned long data);
+extern void start_resync_timer_fn(unsigned long data);
 
 /* drbd_receiver.c */
 extern int drbd_rs_should_slow_down(struct drbd_conf *mdev, sector_t sector);
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index b3b6d3190f65..8ec7c65988be 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2984,12 +2984,16 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
         mdev->go_diskless.cb  = w_go_diskless;
         mdev->md_sync_work.cb = w_md_sync;
         mdev->bm_io_work.w.cb = w_bitmap_io;
+        mdev->start_resync_work.cb = w_start_resync;
         init_timer(&mdev->resync_timer);
         init_timer(&mdev->md_sync_timer);
+        init_timer(&mdev->start_resync_timer);
         mdev->resync_timer.function = resync_timer_fn;
         mdev->resync_timer.data = (unsigned long) mdev;
         mdev->md_sync_timer.function = md_sync_timer_fn;
         mdev->md_sync_timer.data = (unsigned long) mdev;
+        mdev->start_resync_timer.function = start_resync_timer_fn;
+        mdev->start_resync_timer.data = (unsigned long) mdev;
 
         init_waitqueue_head(&mdev->misc_wait);
         init_waitqueue_head(&mdev->state_wait);
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 7991183749e3..18cb8b609fe4 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -4392,11 +4392,9 @@ static int got_BarrierAck(struct drbd_conf *mdev, struct p_header80 *h)
 
         if (mdev->state.conn == C_AHEAD &&
             atomic_read(&mdev->ap_in_flight) == 0 &&
-            atomic_read(&mdev->rs_pending_cnt) == 0 &&
-            list_empty(&mdev->start_resync_work.list)) {
-                    struct drbd_work *w = &mdev->start_resync_work;
-                    w->cb = w_start_resync;
-                    drbd_queue_work(&mdev->data.work, w);
+            !test_and_set_bit(AHEAD_TO_SYNC_SOURCE, &mdev->current_epoch->flags)) {
+                mdev->start_resync_timer.expires = jiffies + HZ;
+                add_timer(&mdev->start_resync_timer);
         }
 
         return true;
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 147f76b26810..3a95b701b5d0 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -712,10 +712,24 @@ static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int ca
 }
 
 
+void start_resync_timer_fn(unsigned long data)
+{
+        struct drbd_conf *mdev = (struct drbd_conf *) data;
+
+        drbd_queue_work(&mdev->data.work, &mdev->start_resync_work);
+}
+
 int w_start_resync(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 {
-        drbd_start_resync(mdev, C_SYNC_SOURCE);
+        if (atomic_read(&mdev->unacked_cnt) || atomic_read(&mdev->rs_pending_cnt)) {
+                dev_warn(DEV, "w_start_resync later...\n");
+                mdev->start_resync_timer.expires = jiffies + HZ/10;
+                add_timer(&mdev->start_resync_timer);
+                return 1;
+        }
 
+        drbd_start_resync(mdev, C_SYNC_SOURCE);
+        clear_bit(AHEAD_TO_SYNC_SOURCE, &mdev->current_epoch->flags);
         return 1;
 }