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authorIlya Dryomov <idryomov@gmail.com>2015-07-16 17:36:11 +0300
committerIlya Dryomov <idryomov@gmail.com>2015-07-31 11:38:57 +0300
commit2761713d35e370fd640b5781109f753066b746c4 (patch)
tree666214eac7b140de1d9444e4207e418acadf78cb /drivers/block
parentfc927cd32feca2acefd90a4ac317fa4f0a2e5955 (diff)
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: <obj_request-1/2 reply> handle_reply() rbd_osd_req_callback() rbd_osd_trivial_callback() rbd_obj_request_complete() rbd_img_obj_copyup_callback() rbd_img_obj_callback() <obj_request-2/2 reply> 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 <elder@linaro.org> Cc: stable@vger.kernel.org # 3.10+, needs backporting for < 3.18 Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Reviewed-by: Alex Elder <elder@linaro.org>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/rbd.c22
1 files changed, 17 insertions, 5 deletions
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index d94529d5c8e9..bc67a93aa4f4 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)