drbd: fix resend/resubmit of frozen IO

DRBD can freeze IO, due to fencing policy (fencing resource-and-stonith),
or because we lost access to data (on-no-data-accessible suspend-io).

Resuming from there (re-connect, or re-attach, or explicit admin
intervention) should "just work".

Unfortunately, if the re-attach/re-connect did not happen within
the timeout, since the commit
  drbd: Implemented real timeout checking for request processing time
if so configured, the request_timer_fn() would timeout and
detach/disconnect virtually immediately.

This change tracks the most recent attach and connect, and does not
timeout within <configured timeout interval> after attach/connect.

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

3 files changed, 48 insertions, 15 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index f215ad430bb..302a6e786f7 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1049,6 +1049,8 @@ struct drbd_conf {
         struct crypto_hash *csums_tfm;
         struct crypto_hash *verify_tfm;
 
+        unsigned long last_reattach_jif;
+        unsigned long last_reconnect_jif;
         struct drbd_thread receiver;
         struct drbd_thread worker;
         struct drbd_thread asender;
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index deccff3af77..ab501b23b50 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1326,6 +1326,15 @@ __drbd_set_state(struct drbd_conf *mdev, union drbd_state ns,
         if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED)
                 drbd_resume_al(mdev);
 
+        /* remember last connect and attach times so request_timer_fn() won't
+         * kill newly established sessions while we are still trying to thaw
+         * previously frozen IO */
+        if (os.conn != C_WF_REPORT_PARAMS && ns.conn == C_WF_REPORT_PARAMS)
+                mdev->last_reconnect_jif = jiffies;
+        if ((os.disk == D_ATTACHING || os.disk == D_NEGOTIATING) &&
+            ns.disk > D_NEGOTIATING)
+                mdev->last_reattach_jif = jiffies;
+
         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 340d57b9856..4a642ce62ba 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -1200,43 +1200,65 @@ void request_timer_fn(unsigned long data)
         struct drbd_request *req; /* oldest request */
         struct list_head *le;
         unsigned long ent = 0, dt = 0, et, nt; /* effective timeout = ko_count * timeout */
+        unsigned long now;
 
         if (get_net_conf(mdev)) {
-                ent = mdev->net_conf->timeout*HZ/10 * mdev->net_conf->ko_count;
+                if (mdev->state.conn >= C_WF_REPORT_PARAMS)
+                        ent = mdev->net_conf->timeout*HZ/10
+                                * mdev->net_conf->ko_count;
                 put_net_conf(mdev);
         }
-        if (get_ldev(mdev)) {
+        if (get_ldev(mdev)) { /* implicit state.disk >= D_INCONSISTENT */
                 dt = mdev->ldev->dc.disk_timeout * HZ / 10;
                 put_ldev(mdev);
         }
         et = min_not_zero(dt, ent);
 
-        if (!et || (mdev->state.conn < C_WF_REPORT_PARAMS && mdev->state.disk <= D_FAILED))
+        if (!et)
                 return; /* Recurring timer stopped */
 
+        now = jiffies;
+
         spin_lock_irq(&mdev->req_lock);
         le = &mdev->oldest_tle->requests;
         if (list_empty(le)) {
                 spin_unlock_irq(&mdev->req_lock);
-                mod_timer(&mdev->request_timer, jiffies + et);
+                mod_timer(&mdev->request_timer, now + et);
                 return;
         }
 
         le = le->prev;
         req = list_entry(le, struct drbd_request, tl_requests);
-        if (ent && req->rq_state & RQ_NET_PENDING) {
-                if (time_is_before_eq_jiffies(req->start_time + ent)) {
-                        dev_warn(DEV, "Remote failed to finish a request within ko-count * timeout\n");
-                        _drbd_set_state(_NS(mdev, conn, C_TIMEOUT), CS_VERBOSE | CS_HARD, NULL);
-                }
+
+        /* The request is considered timed out, if
+         * - we have some effective timeout from the configuration,
+         *   with above state restrictions applied,
+         * - the oldest request is waiting for a response from the network
+         *   resp. the local disk,
+         * - the oldest request is in fact older than the effective timeout,
+         * - the connection was established (resp. disk was attached)
+         *   for longer than the timeout already.
+         * Note that for 32bit jiffies and very stable connections/disks,
+         * we may have a wrap around, which is catched by
+         *   !time_in_range(now, last_..._jif, last_..._jif + timeout).
+         *
+         * Side effect: once per 32bit wrap-around interval, which means every
+         * ~198 days with 250 HZ, we have a window where the timeout would need
+         * to expire twice (worst case) to become effective. Good enough.
+         */
+        if (ent && req->rq_state & RQ_NET_PENDING &&
+                 time_after(now, req->start_time + ent) &&
+                !time_in_range(now, mdev->last_reconnect_jif, mdev->last_reconnect_jif + ent)) {
+                dev_warn(DEV, "Remote failed to finish a request within ko-count * timeout\n");
+                _drbd_set_state(_NS(mdev, conn, C_TIMEOUT), CS_VERBOSE | CS_HARD, NULL);
         }
-        if (dt && req->rq_state & RQ_LOCAL_PENDING) {
-                if (time_is_before_eq_jiffies(req->start_time + dt)) {
-                        dev_warn(DEV, "Local backing device failed to meet the disk-timeout\n");
-                        __drbd_chk_io_error(mdev, 1);
-                }
+        if (dt && req->rq_state & RQ_LOCAL_PENDING &&
+                 time_after(now, req->start_time + dt) &&
+                !time_in_range(now, mdev->last_reattach_jif, mdev->last_reattach_jif + dt)) {
+                dev_warn(DEV, "Local backing device failed to meet the disk-timeout\n");
+                __drbd_chk_io_error(mdev, 1);
         }
-        nt = (time_is_before_eq_jiffies(req->start_time + et) ? jiffies : req->start_time) + et;
+        nt = (time_after(now, req->start_time + et) ? now : req->start_time) + et;
         spin_unlock_irq(&mdev->req_lock);
         mod_timer(&mdev->request_timer, nt);
 }