rbd: ignore zero-length requests

The old request code simply ignored zero-length requests.  We should
still operate that same way to avoid any changes in behavior.  We
can implement handling for special zero-length requests separately
(see http://tracker.ceph.com/issues/4236).

Add some assertions based on this new constraint.

This resolves:
    http://tracker.ceph.com/issues/4237

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index b0eea3eaee93..3cc003b26610 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1560,6 +1560,7 @@ static int rbd_img_request_fill_bio(struct rbd_img_request *img_request,
         image_offset = img_request->offset;
         rbd_assert(image_offset == bio_list->bi_sector << SECTOR_SHIFT);
         resid = img_request->length;
+        rbd_assert(resid > 0);
         while (resid) {
                 const char *object_name;
                 unsigned int clone_size;
@@ -1627,8 +1628,10 @@ static void rbd_img_obj_callback(struct rbd_obj_request *obj_request)
         bool more = true;
 
         img_request = obj_request->img_request;
+
         rbd_assert(img_request != NULL);
         rbd_assert(img_request->rq != NULL);
+        rbd_assert(img_request->obj_request_count > 0);
         rbd_assert(which != BAD_WHICH);
         rbd_assert(which < img_request->obj_request_count);
         rbd_assert(which >= img_request->next_completion);
@@ -1918,6 +1921,19 @@ static void rbd_request_fn(struct request_queue *q)
                 /* Ignore any non-FS requests that filter through. */
 
                 if (rq->cmd_type != REQ_TYPE_FS) {
+                        dout("%s: non-fs request type %d\n", __func__,
+                                (int) rq->cmd_type);
+                        __blk_end_request_all(rq, 0);
+                        continue;
+                }
+
+                /* Ignore/skip any zero-length requests */
+
+                offset = (u64) blk_rq_pos(rq) << SECTOR_SHIFT;
+                length = (u64) blk_rq_bytes(rq);
+
+                if (!length) {
+                        dout("%s: zero-length request\n", __func__);
                         __blk_end_request_all(rq, 0);
                         continue;
                 }
@@ -1947,9 +1963,6 @@ static void rbd_request_fn(struct request_queue *q)
                         goto end_request;
                 }
 
-                offset = (u64) blk_rq_pos(rq) << SECTOR_SHIFT;
-                length = (u64) blk_rq_bytes(rq);
-
                 result = -EINVAL;
                 if (WARN_ON(offset && length > U64_MAX - offset + 1))
                         goto end_request;       /* Shouldn't happen */