1 files changed, 54 insertions, 10 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index c34719c917b1..ee53d8e52801 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1437,20 +1437,20 @@ static void rbd_osd_trivial_callback(struct rbd_obj_request *obj_request)
 static void rbd_osd_read_callback(struct rbd_obj_request *obj_request)
 {
 	struct rbd_img_request *img_request = NULL;
+	struct rbd_device *rbd_dev = NULL;
 	bool layered = false;
 
 	if (obj_request_img_data_test(obj_request)) {
 		img_request = obj_request->img_request;
 		layered = img_request && img_request_layered_test(img_request);
-	} else {
-		img_request = NULL;
-		layered = false;
+		rbd_dev = img_request->rbd_dev;
 	}
 
 	dout("%s: obj %p img %p result %d %llu/%llu\n", __func__,
 		obj_request, img_request, obj_request->result,
 		obj_request->xferred, obj_request->length);
-	if (layered && obj_request->result == -ENOENT)
+	if (layered && obj_request->result == -ENOENT &&
+			obj_request->img_offset < rbd_dev->parent_overlap)
 		rbd_img_parent_read(obj_request);
 	else if (img_request)
 		rbd_img_obj_request_read_callback(obj_request);
@@ -2166,6 +2166,16 @@ static int rbd_img_obj_parent_read_full(struct rbd_obj_request *obj_request)
 	length = (u64)1 << rbd_dev->header.obj_order;
 
 	/*
+	 * There is no defined parent data beyond the parent
+	 * overlap, so limit what we read at that boundary if
+	 * necessary.
+	 */
+	if (img_offset + length > rbd_dev->parent_overlap) {
+		rbd_assert(img_offset < rbd_dev->parent_overlap);
+		length = rbd_dev->parent_overlap - img_offset;
+	}
+
+	/*
 	 * Allocate a page array big enough to receive the data read
 	 * from the parent.
 	 */
@@ -2325,21 +2335,28 @@ out:
 static int rbd_img_obj_request_submit(struct rbd_obj_request *obj_request)
 {
 	struct rbd_img_request *img_request;
+	struct rbd_device *rbd_dev;
 	bool known;
 
 	rbd_assert(obj_request_img_data_test(obj_request));
 
 	img_request = obj_request->img_request;
 	rbd_assert(img_request);
+	rbd_dev = img_request->rbd_dev;
 
 	/*
-	 * Only layered writes need special handling.  If it's not a
-	 * layered write, or it is a layered write but we know the
-	 * target object exists, it's no different from any other
-	 * object request.
+	 * Only writes to layered images need special handling.
+	 * Reads and non-layered writes are simple object requests.
+	 * Layered writes that start beyond the end of the overlap
+	 * with the parent have no parent data, so they too are
+	 * simple object requests.  Finally, if the target object is
+	 * known to already exist, its parent data has already been
+	 * copied, so a write to the object can also be handled as a
+	 * simple object request.
 	 */
 	if (!img_request_write_test(img_request) ||
 		!img_request_layered_test(img_request) ||
+		rbd_dev->parent_overlap <= obj_request->img_offset ||
 		((known = obj_request_known_test(obj_request)) &&
 			obj_request_exists_test(obj_request))) {
 
@@ -2386,14 +2403,41 @@ static int rbd_img_request_submit(struct rbd_img_request *img_request)
 static void rbd_img_parent_read_callback(struct rbd_img_request *img_request)
 {
 	struct rbd_obj_request *obj_request;
+	struct rbd_device *rbd_dev;
+	u64 obj_end;
 
 	rbd_assert(img_request_child_test(img_request));
 
 	obj_request = img_request->obj_request;
-	rbd_assert(obj_request != NULL);
+	rbd_assert(obj_request);
+	rbd_assert(obj_request->img_request);
+
 	obj_request->result = img_request->result;
-	obj_request->xferred = img_request->xferred;
+	if (obj_request->result)
+		goto out;
 
+	/*
+	 * We need to zero anything beyond the parent overlap
+	 * boundary.  Since rbd_img_obj_request_read_callback()
+	 * will zero anything beyond the end of a short read, an
+	 * easy way to do this is to pretend the data from the
+	 * parent came up short--ending at the overlap boundary.
+	 */
+	rbd_assert(obj_request->img_offset < U64_MAX - obj_request->length);
+	obj_end = obj_request->img_offset + obj_request->length;
+	rbd_dev = obj_request->img_request->rbd_dev;
+	if (obj_end > rbd_dev->parent_overlap) {
+		u64 xferred = 0;
+
+		if (obj_request->img_offset < rbd_dev->parent_overlap)
+			xferred = rbd_dev->parent_overlap -
+					obj_request->img_offset;
+
+		obj_request->xferred = min(img_request->xferred, xferred);
+	} else {
+		obj_request->xferred = img_request->xferred;
+	}
+out:
 	rbd_img_obj_request_read_callback(obj_request);
 	rbd_obj_request_complete(obj_request);
 }