drbd: simplify retry path of failed READ requests

If a local or remote READ request fails, just push it back to the retry
workqueue.  It will re-enter __drbd_make_request, and be re-assigned to
a suitable local or remote path, or failed, if we do not have access to
good data anymore.

This obsoletes w_read_retry_remote(),
and eliminates two goto...retry blocks in __req_mod()

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

3 files changed, 19 insertions, 67 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index caeb01eef44e..ab9926e915cb 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1439,7 +1439,6 @@ extern void drbd_csum_bio(struct drbd_conf *, struct crypto_hash *, struct bio *
 extern void drbd_csum_ee(struct drbd_conf *, struct crypto_hash *,
                          struct drbd_peer_request *, void *);
 /* worker callbacks */
-extern int w_read_retry_remote(struct drbd_work *, int);
 extern int w_e_end_data_req(struct drbd_work *, int);
 extern int w_e_end_rsdata_req(struct drbd_work *, int);
 extern int w_e_end_csum_rs_req(struct drbd_work *, int);
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index f708aa1809f0..1249672519ca 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -263,7 +263,6 @@ void req_may_be_completed(struct drbd_request *req, struct bio_and_error *m)
 {
         const unsigned long s = req->rq_state;
         struct drbd_conf *mdev = req->w.mdev;
-        int rw = req->rq_state & RQ_WRITE ? WRITE : READ;
 
         /* we must not complete the master bio, while it is
          *      still being processed by _drbd_send_zc_bio (drbd_send_dblock)
@@ -282,6 +281,8 @@ void req_may_be_completed(struct drbd_request *req, struct bio_and_error *m)
                 return;
 
         if (req->master_bio) {
+                int rw = bio_rw(req->master_bio);
+
                 /* this is DATA_RECEIVED (remote read)
                  * or protocol C P_WRITE_ACK
                  * or protocol B P_RECV_ACK
@@ -326,7 +327,18 @@ void req_may_be_completed(struct drbd_request *req, struct bio_and_error *m)
                 /* Update disk stats */
                 _drbd_end_io_acct(mdev, req);
 
-                if (!(s & RQ_POSTPONED)) {
+                /* if READ failed,
+                 * have it be pushed back to the retry work queue,
+                 * so it will re-enter __drbd_make_request,
+                 * and be re-assigned to a suitable local or remote path,
+                 * or failed if we do not have access to good data anymore.
+                 * READA may fail.
+                 * WRITE should have used all available paths already.
+                 */
+                if (!ok && rw == READ)
+                        req->rq_state |= RQ_POSTPONED;
+
+                if (!(req->rq_state & RQ_POSTPONED)) {
                         m->error = ok ? 0 : (error ?: -EIO);
                         m->bio = req->master_bio;
                         req->master_bio = NULL;
@@ -420,10 +432,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
         case ABORT_DISK_IO:
                 req->rq_state |= RQ_LOCAL_ABORTED;
-                if (req->rq_state & RQ_WRITE)
-                        req_may_be_completed_not_susp(req, m);
-                else
-                        goto goto_queue_for_net_read;
+                req_may_be_completed_not_susp(req, m);
                 break;
 
         case WRITE_COMPLETED_WITH_ERROR:
@@ -451,20 +460,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                 D_ASSERT(!(req->rq_state & RQ_NET_MASK));
 
                 __drbd_chk_io_error(mdev, false);
-
-        goto_queue_for_net_read:
-
-                /* no point in retrying if there is no good remote data,
-                 * or we have no connection. */
-                if (mdev->state.pdsk != D_UP_TO_DATE) {
-                        req_may_be_completed_not_susp(req, m);
-                        break;
-                }
-
-                /* _req_mod(req,TO_BE_SENT); oops, recursion... */
-                req->rq_state |= RQ_NET_PENDING;
-                inc_ap_pending(mdev);
-                /* fall through: _req_mod(req,QUEUE_FOR_NET_READ); */
+                break;
 
         case QUEUE_FOR_NET_READ:
                 /* READ or READA, and
@@ -483,10 +479,9 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                 set_bit(UNPLUG_REMOTE, &mdev->flags);
 
                 D_ASSERT(req->rq_state & RQ_NET_PENDING);
+                D_ASSERT((req->rq_state & RQ_LOCAL_MASK) == 0);
                 req->rq_state |= RQ_NET_QUEUED;
-                req->w.cb = (req->rq_state & RQ_LOCAL_MASK)
-                        ? w_read_retry_remote
-                        : w_send_read_req;
+                req->w.cb = w_send_read_req;
                 drbd_queue_work(&mdev->tconn->data.work, &req->w);
                 break;
 
@@ -604,13 +599,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                 if (req->rq_state & RQ_NET_SENT && req->rq_state & RQ_WRITE)
                         atomic_sub(req->i.size >> 9, &mdev->ap_in_flight);
 
-                /* if it is still queued, we may not complete it here.
-                 * it will be canceled soon. */
-                if (!(req->rq_state & RQ_NET_QUEUED)) {
-                        if (p)
-                                goto goto_read_retry_local;
-                        req_may_be_completed(req, m); /* Allowed while state.susp */
-                }
+                req_may_be_completed(req, m); /* Allowed while state.susp */
                 break;
 
         case DISCARD_WRITE:
@@ -668,27 +657,11 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
                 req->rq_state |= RQ_NET_DONE;
 
-                if (!(req->rq_state & RQ_WRITE))
-                        goto goto_read_retry_local;
-
                 maybe_wakeup_conflicting_requests(req);
                 req_may_be_completed_not_susp(req, m);
                 /* else: done by HANDED_OVER_TO_NETWORK */
                 break;
 
-        goto_read_retry_local:
-                if (!drbd_may_do_local_read(mdev, req->i.sector, req->i.size)) {
-                        req_may_be_completed_not_susp(req, m);
-                        break;
-                }
-                D_ASSERT(!(req->rq_state & RQ_LOCAL_PENDING));
-                req->rq_state |= RQ_LOCAL_PENDING;
-
-                get_ldev(mdev);
-                req->w.cb = w_restart_disk_io;
-                drbd_queue_work(&mdev->tconn->data.work, &req->w);
-                break;
-
         case FAIL_FROZEN_DISK_IO:
                 if (!(req->rq_state & RQ_LOCAL_COMPLETED))
                         break;
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index f10451701cdb..d7573f4b7421 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -244,26 +244,6 @@ void drbd_request_endio(struct bio *bio, int error)
                 complete_master_bio(mdev, &m);
 }
 
-int w_read_retry_remote(struct drbd_work *w, int cancel)
-{
-        struct drbd_request *req = container_of(w, struct drbd_request, w);
-        struct drbd_conf *mdev = w->mdev;
-
-        /* We should not detach for read io-error,
-         * but try to WRITE the P_DATA_REPLY to the failed location,
-         * to give the disk the chance to relocate that block */
-
-        spin_lock_irq(&mdev->tconn->req_lock);
-        if (cancel || mdev->state.pdsk != D_UP_TO_DATE) {
-                _req_mod(req, READ_RETRY_REMOTE_CANCELED);
-                spin_unlock_irq(&mdev->tconn->req_lock);
-                return 0;
-        }
-        spin_unlock_irq(&mdev->tconn->req_lock);
-
-        return w_send_read_req(w, 0);
-}
-
 void drbd_csum_ee(struct drbd_conf *mdev, struct crypto_hash *tfm,
                   struct drbd_peer_request *peer_req, void *digest)
 {