drbd: fix for spin_lock_irqsave in endio callback

In commit 9b7f76dc37919ea36caa9680a3f765e5b19b25fb,
 Author: Lars Ellenberg <lars.ellenberg@linbit.com>
 Date:   Wed Aug 11 23:40:24 2010 +0200

    drbd: new configuration parameter c-min-rate

a bad chunk slipped through, which is now reverted as well,
restoring the correct irqsave for the endio callback.

This patch also add comments at both req_mod()
and in the endio callback so it should not happen again.

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

2 files changed, 11 insertions, 2 deletions

diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index 181ea0364822..ab2bd09d54b4 100644
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -339,7 +339,8 @@ static inline int _req_mod(struct drbd_request *req, enum drbd_req_event what)
 }
 
 /* completion of master bio is outside of spinlock.
- * If you need it irqsave, do it your self! */
+ * If you need it irqsave, do it your self!
+ * Which means: don't use from bio endio callback. */
 static inline int req_mod(struct drbd_request *req,
                 enum drbd_req_event what)
 {
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 47d223c2409c..34f224b018b3 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -193,8 +193,10 @@ void drbd_endio_sec(struct bio *bio, int error)
  */
 void drbd_endio_pri(struct bio *bio, int error)
 {
+        unsigned long flags;
         struct drbd_request *req = bio->bi_private;
         struct drbd_conf *mdev = req->mdev;
+        struct bio_and_error m;
         enum drbd_req_event what;
         int uptodate = bio_flagged(bio, BIO_UPTODATE);
 
@@ -220,7 +222,13 @@ void drbd_endio_pri(struct bio *bio, int error)
         bio_put(req->private_bio);
         req->private_bio = ERR_PTR(error);
 
-        req_mod(req, what);
+        /* not req_mod(), we need irqsave here! */
+        spin_lock_irqsave(&mdev->req_lock, flags);
+        __req_mod(req, what, &m);
+        spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+        if (m.bio)
+                complete_master_bio(mdev, &m);
 }
 
 int w_read_retry_remote(struct drbd_conf *mdev, struct drbd_work *w, int cancel)