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callback X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Josh Durgin , qemu-block@nongnu.org, qemu-devel@nongnu.org, Max Reitz , Jason Dillaman Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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? >> >> 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 >>> --- >>> 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] > >> >> 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. > > Thanks for your comments, > Stefano > Thank you for trying to patch rbd :)