drbd: introduce completion_ref and kref to struct drbd_request

cherry-picked and adapted from drbd 9 devel branch

completion_ref will count pending events necessary for completion.
kref is for destruction.

This only introduces these new members of struct drbd_request,
a followup patch will make actual use of them.

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

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 8536fab..52ad1bf 100644 (file)
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -577,6 +577,11 @@ struct drbd_request {
        struct bio *master_bio;       /* master bio pointer */
        unsigned long rq_state; /* see comments above _req_mod() */
        unsigned long start_time;
+
+       /* once it hits 0, we may complete the master_bio */
+       atomic_t completion_ref;
+       /* once it hits 0, we may destroy this drbd_request object */
+       struct kref kref;
 };
 
 struct drbd_epoch {

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 6bac415..ae894af 100644 (file)
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -85,17 +85,15 @@ static struct drbd_request *drbd_req_new(struct drbd_conf *mdev,
        INIT_LIST_HEAD(&req->tl_requests);
        INIT_LIST_HEAD(&req->w.list);
 
+       atomic_set(&req->completion_ref, 1);
+       kref_init(&req->kref);
        return req;
 }
 
-static void drbd_req_free(struct drbd_request *req)
-{
-       mempool_free(req, drbd_request_mempool);
-}
-
-/* rw is bio_data_dir(), only READ or WRITE */
-static void _req_is_done(struct drbd_conf *mdev, struct drbd_request *req, const int rw)
+static void drbd_req_destroy(struct kref *kref)
 {
+       struct drbd_request *req = container_of(kref, struct drbd_request, kref);
+       struct drbd_conf *mdev = req->w.mdev;
        const unsigned long s = req->rq_state;
 
        /* remove it from the transfer log.
@@ -109,7 +107,7 @@ static void _req_is_done(struct drbd_conf *mdev, struct drbd_request *req, const
        /* if it was a write, we may have to set the corresponding
         * bit(s) out-of-sync first. If it had a local part, we need to
         * release the reference to the activity log. */
-       if (rw == WRITE) {
+       if (s & RQ_WRITE) {
                /* Set out-of-sync unless both OK flags are set
                 * (local only or remote failed).
                 * Other places where we set out-of-sync:
@@ -146,7 +144,7 @@ static void _req_is_done(struct drbd_conf *mdev, struct drbd_request *req, const
        if (s & RQ_POSTPONED)
                drbd_restart_request(req);
        else
-               drbd_req_free(req);
+               mempool_free(req, drbd_request_mempool);
 }
 
 static void wake_all_senders(struct drbd_tconn *tconn) {
@@ -196,12 +194,10 @@ static
 void req_may_be_done(struct drbd_request *req)
 {
        const unsigned long s = req->rq_state;
-       struct drbd_conf *mdev = req->w.mdev;
-       int rw = req->rq_state & RQ_WRITE ? WRITE : READ;
 
        /* req->master_bio still present means: Not yet completed.
         *
-        * Unless this is RQ_POSTPONED, which will cause _req_is_done() to
+        * Unless this is RQ_POSTPONED, which will cause drbd_req_destroy() to
         * queue it on the retry workqueue instead of destroying it.
         */
        if (req->master_bio && !(s & RQ_POSTPONED))
@@ -216,7 +212,7 @@ void req_may_be_done(struct drbd_request *req)
                /* this is disconnected (local only) operation,
                 * or protocol A, B, or C P_BARRIER_ACK,
                 * or killed from the transfer log due to connection loss. */
-               _req_is_done(mdev, req, rw);
+               kref_put(&req->kref, drbd_req_destroy);
        }
        /* else: network part and not DONE yet. that is
         * protocol A, B, or C, barrier ack still pending... */
@@ -250,6 +246,15 @@ void req_may_be_completed(struct drbd_request *req, struct bio_and_error *m)
        if (s & RQ_NET_PENDING)
                return;
 
+       /* FIXME
+        * instead of all the RQ_FLAGS, actually use the completion_ref
+        * to decide if this is ready to be completed. */
+       if (req->master_bio) {
+               int complete = atomic_dec_and_test(&req->completion_ref);
+               D_ASSERT(complete != 0);
+       } else
+               D_ASSERT(atomic_read(&req->completion_ref) == 0);
+
        if (req->master_bio) {
                int rw = bio_rw(req->master_bio);
 
@@ -1113,7 +1118,7 @@ struct drbd_request *find_oldest_request(struct drbd_tconn *tconn)
         * and find the oldest not yet completed request */
        struct drbd_request *r;
        list_for_each_entry(r, &tconn->transfer_log, tl_requests) {
-               if (r->rq_state & (RQ_NET_PENDING|RQ_LOCAL_PENDING))
+               if (atomic_read(&r->completion_ref))
                        return r;
        }
        return NULL;