On Thu, Jun 27, 2019 at 1:24 PM John Snow <js...@redhat.com> wrote: > > > > On 6/27/19 4:48 AM, Stefano Garzarella wrote: > > On Wed, Jun 26, 2019 at 05:04:25PM -0400, John Snow wrote: > >> It looks like this has hit a 30 day expiration without any reviews or > >> being merged; do we still want this? If so, can you please resend? > > > > Yes, I think we still want :) > > > > Is it okay if I send a v3 following your comments? > > > > Yes, but I don't know who is responsible for final approval; I guess > that's Josh Durgin?
I'm the new (for the past several years) upstream PTL for RBD, so feel free to tag me. > >> > >> On 5/10/19 11:33 AM, Stefano Garzarella wrote: > >>> This patch allows 'qemu-img info' to show the 'disk size' for > >>> the RBD images that have the fast-diff feature enabled. > >>> > >>> If this feature is enabled, we use the rbd_diff_iterate2() API > >>> to calculate the allocated size for the image. > >>> > >>> Signed-off-by: Stefano Garzarella <sgarz...@redhat.com> > >>> --- > >>> v2: > >>> - calculate the actual usage only if the fast-diff feature is > >>> enabled [Jason] > >>> --- > >>> block/rbd.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++ > >>> 1 file changed, 54 insertions(+) > >>> > >>> diff --git a/block/rbd.c b/block/rbd.c > >>> index 0c549c9935..f1bc76ab80 100644 > >>> --- a/block/rbd.c > >>> +++ b/block/rbd.c > >>> @@ -1046,6 +1046,59 @@ static int64_t qemu_rbd_getlength(BlockDriverState > >>> *bs) > >>> return info.size; > >>> } > >>> > >>> +static int rbd_allocated_size_cb(uint64_t offset, size_t len, int exists, > >>> + void *arg) > >>> +{ > >>> + int64_t *alloc_size = (int64_t *) arg; > >>> + > >>> + if (exists) { > >>> + (*alloc_size) += len; > >>> + } > >>> + > >>> + return 0; > >>> +} > >>> + > >>> +static int64_t qemu_rbd_get_allocated_file_size(BlockDriverState *bs) > >>> +{ > >>> + BDRVRBDState *s = bs->opaque; > >>> + uint64_t flags, features; > >>> + int64_t alloc_size = 0; > >>> + int r; > >>> + > >>> + r = rbd_get_flags(s->image, &flags); > >>> + if (r < 0) { > >>> + return r; > >>> + } > >>> + > >> > >> Do you know where rbd_get_flags is documented? I can't seem to quickly > >> find a reference that tells me what to expect from calling it. It > >> returns an int, I guess an error code, but how can I confirm this? > >> > >> *clones the ceph repository* > >> > >> src/librbd/internal.cc get_flags convinces me it probably works like I > >> think, but is there not a reference here? > >> > > > > Good question! > > I didn't find any docs, but looking in the ceph tests test/librbd/fsx.cc, > > they print an error message if the return value is less than 0. > > > > A 'get_flags' implemented in cls/rbd/cls_rbd.cc for example returns 0 at the > > end and -EINVAL in a try/catch. It also uses 'read_key()' that in some cases > > returns -EIO, so I hope that the error returned by rbd_get_flags() is one of > > the errors defined in errno.h > > > >>> + r = rbd_get_features(s->image, &features); > >>> + if (r < 0) { > >>> + return r; > >>> + } > >>> + > >>> + /* > >>> + * We use rbd_diff_iterate2() only if the RBD image have fast-diff > >>> + * feature enabled. If it is disabled, rbd_diff_iterate2() could be > >>> + * very slow on a big image. > >>> + */ > >>> + if (!(features & RBD_FEATURE_FAST_DIFF) || > >>> + (flags & RBD_FLAG_FAST_DIFF_INVALID)) { > >>> + return -1; > >>> + } > >>> + > >> > >> (Is there a reference for the list of flags to make sure there aren't > >> other cases we might want to skip this?) > > > > Unfortunately no :( > > As Jason suggested, I followed what libvirt did in the > > volStorageBackendRBDUseFastDiff() [src/storage/storage_backend_rbd.c] These are the only ones. > >> > >> It looks reasonable at a glance, but maybe let's return -ENOTSUP instead > >> of -1, based on the idea that bdrv_get_allocated_file_size returns > >> -ENOMEDIUM in a prominent error case -- let's match that error convention. > > > > Sure, -ENOTSUP is absolutely better! > > > >> > >> (Well, I wonder what the librbd calls are returning and if THOSE mean > >> anything.) > > > > I hope they return an errno.h errors, but I'm not sure if the meaning > > make sense for us. > > > > Do you think is better to return -ENOTSUP or -EIO when librbd calls > > fail? > > > > I'll be honest, I have no idea because I don't know what failure of > these calls means _at all_, so I don't know if it should be something > severe like EIO or something more mundane. > > I guess just leave them alone in absence of better information, honestly. It looks like QEMU treats any negative error code like the actual size isn't available. However, for clarity I would vote for -ENOTSUPP since that's what would be returned if the driver doesn't support it. > > > > Thanks for your comments, > > Stefano > > > > Thank you for trying to patch rbd :) -- Jason