[PATCH 02/30] drbd: change bitmap write-out when leaving resync states

[Philipp Reisner]

From: Lars Ellenberg <lars.ellenb...@linbit.com>

When leaving resync states because of disconnect,
do the bitmap write-out synchronously in the drbd_disconnected() path.

When leaving resync states because we go back to AHEAD/BEHIND, or
because resync actually finished, or some disk was lost during resync,
trigger the write-out from after_state_ch().

The bitmap write-out for resync -> ahead/behind was missing completely before.

Note that this is all only an optimization to avoid double-resyncs of
already completed blocks in case this node crashes.

Signed-off-by: Philipp Reisner <philipp.reis...@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenb...@linbit.com>
---
 drivers/block/drbd/drbd_receiver.c | 8 +++++---
 drivers/block/drbd/drbd_state.c    | 9 +++++++--
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/block/drbd/drbd_receiver.c 
b/drivers/block/drbd/drbd_receiver.c
index 050aaa1..8b30ab5 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -4783,9 +4783,11 @@ static int drbd_disconnected(struct drbd_peer_device 
*peer_device)
 
        drbd_md_sync(device);
 
-       /* serialize with bitmap writeout triggered by the state change,
-        * if any. */
-       wait_event(device->misc_wait, !test_bit(BITMAP_IO, &device->flags));
+       if (get_ldev(device)) {
+               drbd_bitmap_io(device, &drbd_bm_write_copy_pages,
+                               "write from disconnected", 
BM_LOCKED_CHANGE_ALLOWED);
+               put_ldev(device);
+       }
 
        /* tcp_close and release of sendpage pages can be deferred.  I don't
         * want to use SO_LINGER, because apparently it can be deferred for
diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
index 5a7ef78..59c6467 100644
--- a/drivers/block/drbd/drbd_state.c
+++ b/drivers/block/drbd/drbd_state.c
@@ -1934,12 +1934,17 @@ static void after_state_ch(struct drbd_device *device, 
union drbd_state os,
 
        /* This triggers bitmap writeout of potentially still unwritten pages
         * if the resync finished cleanly, or aborted because of peer disk
-        * failure, or because of connection loss.
+        * failure, or on transition from resync back to AHEAD/BEHIND.
+        *
+        * Connection loss is handled in drbd_disconnected() by the receiver.
+        *
         * For resync aborted because of local disk failure, we cannot do
         * any bitmap writeout anymore.
+        *
         * No harm done if some bits change during this phase.
         */
-       if (os.conn > C_CONNECTED && ns.conn <= C_CONNECTED && 
get_ldev(device)) {
+       if ((os.conn > C_CONNECTED && os.conn < C_AHEAD) &&
+           (ns.conn == C_CONNECTED || ns.conn >= C_AHEAD) && get_ldev(device)) 
{
                drbd_queue_bitmap_io(device, &drbd_bm_write_copy_pages, NULL,
                        "write from resync_finished", BM_LOCKED_CHANGE_ALLOWED);
                put_ldev(device);
-- 
2.7.4