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-rw-r--r--drivers/block/drbd/drbd_worker.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 933091ffefca..62bde5ae17f7 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -77,10 +77,21 @@ void drbd_md_io_complete(struct bio *bio, int error)
md_io->error = error;
+ /* We grabbed an extra reference in _drbd_md_sync_page_io() to be able
+ * to timeout on the lower level device, and eventually detach from it.
+ * If this io completion runs after that timeout expired, this
+ * drbd_md_put_buffer() may allow us to finally try and re-attach.
+ * During normal operation, this only puts that extra reference
+ * down to 1 again.
+ * Make sure we first drop the reference, and only then signal
+ * completion, or we may (in drbd_al_read_log()) cycle so fast into the
+ * next drbd_md_sync_page_io(), that we trigger the
+ * ASSERT(atomic_read(&mdev->md_io_in_use) == 1) there.
+ */
+ drbd_md_put_buffer(mdev);
md_io->done = 1;
wake_up(&mdev->misc_wait);
bio_put(bio);
- drbd_md_put_buffer(mdev);
put_ldev(mdev);
}