drbd: fix list corruption (recent regression)

The commit 288f422ec13667de40b278535d2a5fb5c77352c4
 drbd: Track all IO requests on the TL, not writes only
moved a list_add_tail(req, ) into a region where req
may have just been freed due to conflict detection.

Fix this by adding a proper cleanup section for that code path.

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

1 files changed, 17 insertions, 25 deletions

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 4e1e10d67c4b..3b61d767d9c4 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -917,31 +917,8 @@ allocate_barrier:
         /* check this request on the collision detection hash tables.
          * if we have a conflict, just complete it here.
          * THINK do we want to check reads, too? (I don't think so...) */
-        if (rw == WRITE && _req_conflicts(req)) {
-                /* this is a conflicting request.
-                 * even though it may have been only _partially_
-                 * overlapping with one of the currently pending requests,
-                 * without even submitting or sending it, we will
-                 * pretend that it was successfully served right now.
-                 */
-                if (local) {
-                        bio_put(req->private_bio);
-                        req->private_bio = NULL;
-                        drbd_al_complete_io(mdev, req->sector);
-                        put_ldev(mdev);
-                        local = 0;
-                }
-                if (remote)
-                        dec_ap_pending(mdev);
-                _drbd_end_io_acct(mdev, req);
-                /* THINK: do we want to fail it (-EIO), or pretend success? */
-                bio_endio(req->master_bio, 0);
-                req->master_bio = NULL;
-                dec_ap_bio(mdev);
-                drbd_req_free(req);
-                remote = 0;
-        }
-
+        if (rw == WRITE && _req_conflicts(req))
+                goto fail_conflicting;
 
         list_add_tail(&req->tl_requests, &mdev->newest_tle->requests);
 
@@ -976,6 +953,21 @@ allocate_barrier:
 
         return 0;
 
+fail_conflicting:
+        /* this is a conflicting request.
+         * even though it may have been only _partially_
+         * overlapping with one of the currently pending requests,
+         * without even submitting or sending it, we will
+         * pretend that it was successfully served right now.
+         */
+        _drbd_end_io_acct(mdev, req);
+        spin_unlock_irq(&mdev->req_lock);
+        if (remote)
+                dec_ap_pending(mdev);
+        /* THINK: do we want to fail it (-EIO), or pretend success?
+         * this pretends success. */
+        err = 0;
+
 fail_free_complete:
         if (rw == WRITE && local)
                 drbd_al_complete_io(mdev, sector);