On Thu, Apr 12, 2018 at 2:58 PM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote: > On Thu, Apr 12, 2018 at 4:23 AM, handong He <hedongho@xxxxxxxxx> wrote: >> Hi, cephers: >> >> I did some test about rbd cli operation and have some doubt. >> >> 1. rbd can be removed during copy operation. And both 'cp' and >> 'rm' command return success. However the dest-image data is diff from >> the src-image. >> why not set a watcher for the rbd_header obj for the opening >> image. So it will occur error and return image ebusy when run 'rm'. >> >> easy to reproduce: >> 1. rbd cp rbd/img0 rbd/img1 >> 2. while cp is runing, exec: rbd rm rbd/img0 >> 3. after finish, just compare two img's du(USED): rbd du rbd/img1 > > The rationale is that reading from an image should only require > read-access to the pool. Establishing a watch on an image requires > write access. You could also hit a similar problem if you deleted an > image while exporting it, or deleting a snapshot while reading from > it, or overwrite an image while copying it, etc, etc, etc. I'd be > interesting in your use-case where you are realistically hitting these > scenarios. > >> 2. in krbd, image-feature should be only set 'layering' for the >> 'map' operation.But for clone image: the child img set layering, but >> parent img has more feature that krbd not support. it will fail while >> child img exec ' rbd map'. >> i think it is logical, but maybe a little complex while the >> chain is long. we have to lookup every ancestors and make sure their >> feature is match krbd's support features. will that be any optimize? >> >> easy to reproduce: >> 1. rbd clone rbd/img0@sn1 rbd/img1 --image-feature=layering >> 2. parent img0 has default feature, which make 'rbd map >> rbd/img1' failed. > > This could probably be improved by having krbd pass the optional > read-only flag down to the 'get_features' rbd class method [1][2]. For > the parent image case, it would be opened read-only which means that > its feature flags would be ANDed with a mask to reduce the > incompatible feature set [3]. > > [1] https://github.com/torvalds/linux/blob/master/drivers/block/rbd.c#L4471 > [2] https://github.com/ceph/ceph/blob/master/src/cls/rbd/cls_rbd.cc#L403 > [3] https://github.com/ceph/ceph/blob/master/src/include/rbd/features.h#L32 Yeah, we don't make any distinction between rw and ro access in krbd. I have filed http://tracker.ceph.com/issues/23688. Thanks, Ilya -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
