On Wed, 27 Mar 2013, Alex Elder wrote:
> (This patch is available in the branch "review/wip-4559" in the
> ceph-client git repository.)
>
> A result of ENOENT from a read request for an object that's part of
> an rbd image indicates that there is a hole in that portion of the
> image. Similarly, a short read for such an object indicates that
> the remainder of the read should be interpreted a full read with
> zeros filling out the end of the request.
>
> This behavior is not correct for objects that are not backing rbd
> image data. Currently rbd_img_obj_request_callback() assumes it
> should be done for all objects.
>
> Change rbd_img_obj_request_callback() so it only does this zeroing
> for image objects. Encapsulate that special handling in its own
> function. Add an assertion that the image object request is a bio
> request, since we assume that (and we currently don't support any
> other types).
Does this only affect the current -rc or is this problem older than that?
We should add some workunit tests that verify that mapping nonexistent
images behaves.
sage
>
> Reported-by: Dan van der Ster <dan@xxxxxxxxxxxxxx>
> Signed-off-by: Alex Elder <elder@xxxxxxxxxxx>
> ---
> drivers/block/rbd.c | 47 ++++++++++++++++++++++++++++++-----------------
> 1 file changed, 30 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index cc74b2c..d54a045 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -1264,6 +1264,32 @@ static bool obj_request_done_test(struct
> rbd_obj_request *obj_request)
> return atomic_read(&obj_request->done) != 0;
> }
>
> +static void
> +rbd_img_obj_request_read_callback(struct rbd_obj_request *obj_request)
> +{
> + dout("%s: obj %p img %p result %d %llu/%llu\n", __func__,
> + obj_request, obj_request->img_request, obj_request->result,
> + obj_request->xferred, obj_request->length);
> + /*
> + * ENOENT means a hole in the image. We zero-fill the
> + * entire length of the request. A short read also implies
> + * zero-fill to the end of the request. Either way we
> + * update the xferred count to indicate the whole request
> + * was satisfied.
> + */
> + BUG_ON(obj_request->type != OBJ_REQUEST_BIO);
> + if (obj_request->result == -ENOENT) {
> + zero_bio_chain(obj_request->bio_list, 0);
> + obj_request->result = 0;
> + obj_request->xferred = obj_request->length;
> + } else if (obj_request->xferred < obj_request->length &&
> + !obj_request->result) {
> + zero_bio_chain(obj_request->bio_list, obj_request->xferred);
> + obj_request->xferred = obj_request->length;
> + }
> + obj_request_done_set(obj_request);
> +}
> +
> static void rbd_obj_request_complete(struct rbd_obj_request *obj_request)
> {
> dout("%s: obj %p cb %p\n", __func__, obj_request,
> @@ -1284,23 +1310,10 @@ static void rbd_osd_read_callback(struct
> rbd_obj_request *obj_request)
> {
> dout("%s: obj %p result %d %llu/%llu\n", __func__, obj_request,
> obj_request->result, obj_request->xferred, obj_request->length);
> - /*
> - * ENOENT means a hole in the object. We zero-fill the
> - * entire length of the request. A short read also implies
> - * zero-fill to the end of the request. Either way we
> - * update the xferred count to indicate the whole request
> - * was satisfied.
> - */
> - if (obj_request->result == -ENOENT) {
> - zero_bio_chain(obj_request->bio_list, 0);
> - obj_request->result = 0;
> - obj_request->xferred = obj_request->length;
> - } else if (obj_request->xferred < obj_request->length &&
> - !obj_request->result) {
> - zero_bio_chain(obj_request->bio_list, obj_request->xferred);
> - obj_request->xferred = obj_request->length;
> - }
> - obj_request_done_set(obj_request);
> + if (obj_request->img_request)
> + rbd_img_obj_request_read_callback(obj_request);
> + else
> + obj_request_done_set(obj_request);
> }
>
> static void rbd_osd_write_callback(struct rbd_obj_request *obj_request)
> --
> 1.7.9.5
>
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