drbd: Ensure that an epoch contains only requests of one kind

The assert in drbd_req.c:755 forces us to have only requests of
one kind in an epoch. The two kinds we distinguish here are:
local-only or mirrored.

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

3 files changed, 28 insertions, 26 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 1061b9fff2b0..34ee8e44a751 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1261,9 +1261,14 @@ __drbd_set_state(struct drbd_conf *mdev, union drbd_state ns,
         if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED)
                 drbd_resume_al(mdev);
 
-        if (os.conn == C_AHEAD && ns.conn != C_AHEAD)
+        /* Start a new epoch in case we start to mirror write requests */
+        if (!drbd_should_do_remote(os) && drbd_should_do_remote(ns))
                 tl_forget(mdev);
 
+        /* Do not add local-only requests to an epoch with mirrored requests */
+        if (drbd_should_do_remote(os) && !drbd_should_do_remote(ns))
+                set_bit(CREATE_BARRIER, &mdev->flags);
+
         ascw = kmalloc(sizeof(*ascw), GFP_ATOMIC);
         if (ascw) {
                 ascw->os = os;
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 6f9d1bfcca58..336937a14d3f 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -762,27 +762,6 @@ static int drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int s
         return 0 == drbd_bm_count_bits(mdev, sbnr, ebnr);
 }
 
-static bool drbd_should_do_remote(struct drbd_conf *mdev)
-{
-        union drbd_state s = mdev->state;
-
-        return s.pdsk == D_UP_TO_DATE ||
-                (s.pdsk >= D_INCONSISTENT &&
-                 s.conn >= C_WF_BITMAP_T &&
-                 s.conn < C_AHEAD);
-        /* Before proto 96 that was >= CONNECTED instead of >= C_WF_BITMAP_T.
-           That is equivalent since before 96 IO was frozen in the C_WF_BITMAP*
-           states. */
-}
-static bool drbd_should_send_oos(struct drbd_conf *mdev)
-{
-        union drbd_state s = mdev->state;
-
-        return s.conn == C_AHEAD || s.conn == C_WF_BITMAP_S;
-        /* pdsk = D_INCONSISTENT as a consequence. Protocol 96 check not necessary
-           since we enter state C_AHEAD only if proto >= 96 */
-}
-
 static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio, unsigned long start_time)
 {
         const int rw = bio_rw(bio);
@@ -854,8 +833,8 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio, uns
                 drbd_al_begin_io(mdev, sector);
         }
 
-        remote = remote && drbd_should_do_remote(mdev);
-        send_oos = rw == WRITE && drbd_should_send_oos(mdev);
+        remote = remote && drbd_should_do_remote(mdev->state);
+        send_oos = rw == WRITE && drbd_should_send_oos(mdev->state);
         D_ASSERT(!(remote && send_oos));
 
         if (!(local || remote) && !is_susp(mdev->state)) {
@@ -896,8 +875,8 @@ allocate_barrier:
         }
 
         if (remote || send_oos) {
-                remote = drbd_should_do_remote(mdev);
-                send_oos = rw == WRITE && drbd_should_send_oos(mdev);
+                remote = drbd_should_do_remote(mdev->state);
+                send_oos = rw == WRITE && drbd_should_send_oos(mdev->state);
                 D_ASSERT(!(remote && send_oos));
 
                 if (!(remote || send_oos))
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index 077c47b1e9d7..32c1f2a31266 100644
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -360,4 +360,22 @@ static inline int req_mod(struct drbd_request *req,
 
         return rv;
 }
+
+static inline bool drbd_should_do_remote(union drbd_state s)
+{
+        return s.pdsk == D_UP_TO_DATE ||
+                (s.pdsk >= D_INCONSISTENT &&
+                 s.conn >= C_WF_BITMAP_T &&
+                 s.conn < C_AHEAD);
+        /* Before proto 96 that was >= CONNECTED instead of >= C_WF_BITMAP_T.
+           That is equivalent since before 96 IO was frozen in the C_WF_BITMAP*
+           states. */
+}
+static inline bool drbd_should_send_oos(union drbd_state s)
+{
+        return s.conn == C_AHEAD || s.conn == C_WF_BITMAP_S;
+        /* pdsk = D_INCONSISTENT as a consequence. Protocol 96 check not necessary
+           since we enter state C_AHEAD only if proto >= 96 */
+}
+
 #endif