From 2761713d35e370fd640b5781109f753066b746c4 Mon Sep 17 00:00:00 2001 From: Ilya Dryomov Date: Thu, 16 Jul 2015 17:36:11 +0300 Subject: [PATCH] rbd: fix copyup completion race For write/discard obj_requests that involved a copyup method call, the opcode of the first op is CEPH_OSD_OP_CALL and the ->callback is rbd_img_obj_copyup_callback(). The latter frees copyup pages, sets ->xferred and delegates to rbd_img_obj_callback(), the "normal" image object callback, for reporting to block layer and putting refs. rbd_osd_req_callback() however treats CEPH_OSD_OP_CALL as a trivial op, which means obj_request is marked done in rbd_osd_trivial_callback(), *before* ->callback is invoked and rbd_img_obj_copyup_callback() has a chance to run. Marking obj_request done essentially means giving rbd_img_obj_callback() a license to end it at any moment, so if another obj_request from the same img_request is being completed concurrently, rbd_img_obj_end_request() may very well be called on such prematurally marked done request: handle_reply() rbd_osd_req_callback() rbd_osd_trivial_callback() rbd_obj_request_complete() rbd_img_obj_copyup_callback() rbd_img_obj_callback() handle_reply() rbd_osd_req_callback() rbd_osd_trivial_callback() for_each_obj_request(obj_request->img_request) { rbd_img_obj_end_request(obj_request-1/2) rbd_img_obj_end_request(obj_request-2/2) <-- } Calling rbd_img_obj_end_request() on such a request leads to trouble, in particular because its ->xfferred is 0. We report 0 to the block layer with blk_update_request(), get back 1 for "this request has more data in flight" and then trip on rbd_assert(more ^ (which == img_request->obj_request_count)); with rhs (which == ...) being 1 because rbd_img_obj_end_request() has been called for both requests and lhs (more) being 1 because we haven't got a chance to set ->xfferred in rbd_img_obj_copyup_callback() yet. To fix this, leverage that rbd wants to call class methods in only two cases: one is a generic method call wrapper (obj_request is standalone) and the other is a copyup (obj_request is part of an img_request). So make a dedicated handler for CEPH_OSD_OP_CALL and directly invoke rbd_img_obj_copyup_callback() from it if obj_request is part of an img_request, similar to how CEPH_OSD_OP_READ handler invokes rbd_img_obj_request_read_callback(). Since rbd_img_obj_copyup_callback() is now being called from the OSD request callback (only), it is renamed to rbd_osd_copyup_callback(). Cc: Alex Elder Cc: stable@vger.kernel.org # 3.10+, needs backporting for < 3.18 Signed-off-by: Ilya Dryomov Reviewed-by: Alex Elder --- drivers/block/rbd.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index d94529d..bc67a93 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -523,6 +523,7 @@ void rbd_warn(struct rbd_device *rbd_dev, const char *fmt, ...) # define rbd_assert(expr) ((void) 0) #endif /* !RBD_DEBUG */ +static void rbd_osd_copyup_callback(struct rbd_obj_request *obj_request); static int rbd_img_obj_request_submit(struct rbd_obj_request *obj_request); static void rbd_img_parent_read(struct rbd_obj_request *obj_request); static void rbd_dev_remove_parent(struct rbd_device *rbd_dev); @@ -1818,6 +1819,16 @@ static void rbd_osd_stat_callback(struct rbd_obj_request *obj_request) obj_request_done_set(obj_request); } +static void rbd_osd_call_callback(struct rbd_obj_request *obj_request) +{ + dout("%s: obj %p\n", __func__, obj_request); + + if (obj_request_img_data_test(obj_request)) + rbd_osd_copyup_callback(obj_request); + else + obj_request_done_set(obj_request); +} + static void rbd_osd_req_callback(struct ceph_osd_request *osd_req, struct ceph_msg *msg) { @@ -1866,6 +1877,8 @@ static void rbd_osd_req_callback(struct ceph_osd_request *osd_req, rbd_osd_discard_callback(obj_request); break; case CEPH_OSD_OP_CALL: + rbd_osd_call_callback(obj_request); + break; case CEPH_OSD_OP_NOTIFY_ACK: case CEPH_OSD_OP_WATCH: rbd_osd_trivial_callback(obj_request); @@ -2530,13 +2543,15 @@ out_unwind: } static void -rbd_img_obj_copyup_callback(struct rbd_obj_request *obj_request) +rbd_osd_copyup_callback(struct rbd_obj_request *obj_request) { struct rbd_img_request *img_request; struct rbd_device *rbd_dev; struct page **pages; u32 page_count; + dout("%s: obj %p\n", __func__, obj_request); + rbd_assert(obj_request->type == OBJ_REQUEST_BIO || obj_request->type == OBJ_REQUEST_NODATA); rbd_assert(obj_request_img_data_test(obj_request)); @@ -2563,9 +2578,7 @@ rbd_img_obj_copyup_callback(struct rbd_obj_request *obj_request) if (!obj_request->result) obj_request->xferred = obj_request->length; - /* Finish up with the normal image object callback */ - - rbd_img_obj_callback(obj_request); + obj_request_done_set(obj_request); } static void @@ -2650,7 +2663,6 @@ rbd_img_obj_parent_read_full_callback(struct rbd_img_request *img_request) /* All set, send it off. */ - orig_request->callback = rbd_img_obj_copyup_callback; osdc = &rbd_dev->rbd_client->client->osdc; img_result = rbd_obj_request_submit(osdc, orig_request); if (!img_result) -- 2.7.4