From 9638556a276125553549fdfe349c464481ec2f39 Mon Sep 17 00:00:00 2001 From: Ilya Dryomov Date: Tue, 10 Jun 2014 13:53:29 +0400 Subject: [PATCH] rbd: handle parent_overlap on writes correctly The following check in rbd_img_obj_request_submit() rbd_dev->parent_overlap <= obj_request->img_offset allows the fall through to the non-layered write case even if both parent_overlap and obj_request->img_offset belong to the same RADOS object. This leads to data corruption, because the area to the left of parent_overlap ends up unconditionally zero-filled instead of being populated with parent data. Suppose we want to write 1M to offset 6M of image bar, which is a clone of foo@snap; object_size is 4M, parent_overlap is 5M: rbd_data..0000000000000001 ---------------------|----------------------|------------ | should be copyup'ed | should be zeroed out | write ... ---------------------|----------------------|------------ 4M 5M 6M parent_overlap obj_request->img_offset 4..5M should be copyup'ed from foo, yet it is zero-filled, just like 5..6M is. Given that the only striping mode kernel client currently supports is chunking (i.e. stripe_unit == object_size, stripe_count == 1), round parent_overlap up to the next object boundary for the purposes of the overlap check. Cc: stable@vger.kernel.org # 3.10+ Signed-off-by: Ilya Dryomov Reviewed-by: Josh Durgin --- drivers/block/rbd.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index bbeb404b3a07..b2c98c1bc037 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -1431,6 +1431,14 @@ static bool obj_request_exists_test(struct rbd_obj_request *obj_request) return test_bit(OBJ_REQ_EXISTS, &obj_request->flags) != 0; } +static bool obj_request_overlaps_parent(struct rbd_obj_request *obj_request) +{ + struct rbd_device *rbd_dev = obj_request->img_request->rbd_dev; + + return obj_request->img_offset < + round_up(rbd_dev->parent_overlap, rbd_obj_bytes(&rbd_dev->header)); +} + static void rbd_obj_request_get(struct rbd_obj_request *obj_request) { dout("%s: obj %p (was %d)\n", __func__, obj_request, @@ -2748,7 +2756,7 @@ static int rbd_img_obj_request_submit(struct rbd_obj_request *obj_request) */ if (!img_request_write_test(img_request) || !img_request_layered_test(img_request) || - rbd_dev->parent_overlap <= obj_request->img_offset || + !obj_request_overlaps_parent(obj_request) || ((known = obj_request_known_test(obj_request)) && obj_request_exists_test(obj_request))) { -- 2.20.1