drbd: If we detect late that IO got frozen, retry after we thawed.

If we detect late (= after grabing mdev->req_lock) that IO got frozen, we
return 1 to generic_make_request(), which simply will retry to make a
request for that bio.

In the subsequent call of generic_make_request() into drbd_make_request_26()
we sleep in inc_ap_bio().

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

2 files changed, 28 insertions, 9 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 4b97f30bb7c6..c194348a46ed 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -2223,7 +2223,7 @@ static inline int __inc_ap_bio_cond(struct drbd_conf *mdev)
 /* I'd like to use wait_event_lock_irq,
  * but I'm not sure when it got introduced,
  * and not sure when it has 3 or 4 arguments */
-static inline void inc_ap_bio(struct drbd_conf *mdev, int one_or_two)
+static inline void inc_ap_bio(struct drbd_conf *mdev, int count)
 {
         /* compare with after_state_ch,
          * os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S */
@@ -2245,7 +2245,7 @@ static inline void inc_ap_bio(struct drbd_conf *mdev, int one_or_two)
                 finish_wait(&mdev->misc_wait, &wait);
                 spin_lock_irq(&mdev->req_lock);
         }
-        atomic_add(one_or_two, &mdev->ap_bio_cnt);
+        atomic_add(count, &mdev->ap_bio_cnt);
         spin_unlock_irq(&mdev->req_lock);
 }
 
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 343e0e6dd532..3397f11d0ba9 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -722,6 +722,7 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
         struct drbd_request *req;
         int local, remote;
         int err = -EIO;
+        int ret = 0;
 
         /* allocate outside of all locks; */
         req = drbd_req_new(mdev, bio);
@@ -784,7 +785,7 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
                             (mdev->state.pdsk == D_INCONSISTENT &&
                              mdev->state.conn >= C_CONNECTED));
 
-        if (!(local || remote)) {
+        if (!(local || remote) && !mdev->state.susp) {
                 dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
                 goto fail_free_complete;
         }
@@ -810,6 +811,16 @@ allocate_barrier:
         /* GOOD, everything prepared, grab the spin_lock */
         spin_lock_irq(&mdev->req_lock);
 
+        if (mdev->state.susp) {
+                /* If we got suspended, use the retry mechanism of
+                   generic_make_request() to restart processing of this
+                   bio. In the next call to drbd_make_request_26
+                   we sleep in inc_ap_bio() */
+                ret = 1;
+                spin_unlock_irq(&mdev->req_lock);
+                goto fail_free_complete;
+        }
+
         if (remote) {
                 remote = (mdev->state.pdsk == D_UP_TO_DATE ||
                             (mdev->state.pdsk == D_INCONSISTENT &&
@@ -947,12 +958,14 @@ fail_and_free_req:
                 req->private_bio = NULL;
                 put_ldev(mdev);
         }
-        bio_endio(bio, err);
+        if (!ret)
+                bio_endio(bio, err);
+
         drbd_req_free(req);
         dec_ap_bio(mdev);
         kfree(b);
 
-        return 0;
+        return ret;
 }
 
 /* helper function for drbd_make_request
@@ -1065,15 +1078,21 @@ int drbd_make_request_26(struct request_queue *q, struct bio *bio)
 
                 /* we need to get a "reference count" (ap_bio_cnt)
                  * to avoid races with the disconnect/reconnect/suspend code.
-                 * In case we need to split the bio here, we need to get two references
+                 * In case we need to split the bio here, we need to get three references
                  * atomically, otherwise we might deadlock when trying to submit the
                  * second one! */
-                inc_ap_bio(mdev, 2);
+                inc_ap_bio(mdev, 3);
 
                 D_ASSERT(e_enr == s_enr + 1);
 
-                drbd_make_request_common(mdev, &bp->bio1);
-                drbd_make_request_common(mdev, &bp->bio2);
+                while (drbd_make_request_common(mdev, &bp->bio1))
+                        inc_ap_bio(mdev, 1);
+
+                while (drbd_make_request_common(mdev, &bp->bio2))
+                        inc_ap_bio(mdev, 1);
+
+                dec_ap_bio(mdev);
+
                 bio_pair_release(bp);
         }
         return 0;