On Thu, Jan 6, 2022 at 5:33 PM Peter Lieven <p...@kamp.de> wrote: > > Am 06.01.22 um 17:01 schrieb Ilya Dryomov: > > On Thu, Jan 6, 2022 at 4:27 PM Peter Lieven <p...@kamp.de> wrote: > >> Am 05.10.21 um 10:36 schrieb Ilya Dryomov: > >>> On Tue, Oct 5, 2021 at 10:19 AM Peter Lieven <p...@kamp.de> wrote: > >>>> Am 05.10.21 um 09:54 schrieb Ilya Dryomov: > >>>>> On Thu, Sep 16, 2021 at 2:21 PM Peter Lieven <p...@kamp.de> wrote: > >>>>>> the qemu rbd driver currently lacks support for bdrv_co_block_status. > >>>>>> This results mainly in incorrect progress during block operations (e.g. > >>>>>> qemu-img convert with an rbd image as source). > >>>>>> > >>>>>> This patch utilizes the rbd_diff_iterate2 call from librbd to detect > >>>>>> allocated and unallocated (all zero areas). > >>>>>> > >>>>>> To avoid querying the ceph OSDs for the answer this is only done if > >>>>>> the image has the fast-diff feature which depends on the object-map and > >>>>>> exclusive-lock features. In this case it is guaranteed that the > >>>>>> information > >>>>>> is present in memory in the librbd client and thus very fast. > >>>>>> > >>>>>> If fast-diff is not available all areas are reported to be allocated > >>>>>> which is the current behaviour if bdrv_co_block_status is not > >>>>>> implemented. > >>>>>> > >>>>>> Signed-off-by: Peter Lieven <p...@kamp.de> > >>>>>> --- > >>>>>> V2->V3: > >>>>>> - check rbd_flags every time (they can change during runtime) [Ilya] > >>>>>> - also check for fast-diff invalid flag [Ilya] > >>>>>> - *map and *file cant be NULL [Ilya] > >>>>>> - set ret = BDRV_BLOCK_ZERO | BDRV_BLOCK_OFFSET_VALID in case of an > >>>>>> unallocated area [Ilya] > >>>>>> - typo: catched -> caught [Ilya] > >>>>>> - changed wording about fast-diff, object-map and exclusive lock in > >>>>>> commit msg [Ilya] > >>>>>> > >>>>>> V1->V2: > >>>>>> - add commit comment [Stefano] > >>>>>> - use failed_post_open [Stefano] > >>>>>> - remove redundant assert [Stefano] > >>>>>> - add macro+comment for the magic -9000 value [Stefano] > >>>>>> - always set *file if its non NULL [Stefano] > >>>>>> > >>>>>> block/rbd.c | 126 > >>>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++ > >>>>>> 1 file changed, 126 insertions(+) > >>>>>> > >>>>>> diff --git a/block/rbd.c b/block/rbd.c > >>>>>> index dcf82b15b8..3cb24f9981 100644 > >>>>>> --- a/block/rbd.c > >>>>>> +++ b/block/rbd.c > >>>>>> @@ -1259,6 +1259,131 @@ static ImageInfoSpecific > >>>>>> *qemu_rbd_get_specific_info(BlockDriverState *bs, > >>>>>> return spec_info; > >>>>>> } > >>>>>> > >>>>>> +typedef struct rbd_diff_req { > >>>>>> + uint64_t offs; > >>>>>> + uint64_t bytes; > >>>>>> + int exists; > >>>>> Hi Peter, > >>>>> > >>>>> Nit: make exists a bool. The one in the callback has to be an int > >>>>> because of the callback signature but let's not spread that. > >>>>> > >>>>>> +} rbd_diff_req; > >>>>>> + > >>>>>> +/* > >>>>>> + * rbd_diff_iterate2 allows to interrupt the exection by returning a > >>>>>> negative > >>>>>> + * value in the callback routine. Choose a value that does not > >>>>>> conflict with > >>>>>> + * an existing exitcode and return it if we want to prematurely stop > >>>>>> the > >>>>>> + * execution because we detected a change in the allocation status. > >>>>>> + */ > >>>>>> +#define QEMU_RBD_EXIT_DIFF_ITERATE2 -9000 > >>>>>> + > >>>>>> +static int qemu_rbd_co_block_status_cb(uint64_t offs, size_t len, > >>>>>> + int exists, void *opaque) > >>>>>> +{ > >>>>>> + struct rbd_diff_req *req = opaque; > >>>>>> + > >>>>>> + assert(req->offs + req->bytes <= offs); > >>>>>> + > >>>>>> + if (req->exists && offs > req->offs + req->bytes) { > >>>>>> + /* > >>>>>> + * we started in an allocated area and jumped over an > >>>>>> unallocated area, > >>>>>> + * req->bytes contains the length of the allocated area > >>>>>> before the > >>>>>> + * unallocated area. stop further processing. > >>>>>> + */ > >>>>>> + return QEMU_RBD_EXIT_DIFF_ITERATE2; > >>>>>> + } > >>>>>> + if (req->exists && !exists) { > >>>>>> + /* > >>>>>> + * we started in an allocated area and reached a hole. > >>>>>> req->bytes > >>>>>> + * contains the length of the allocated area before the hole. > >>>>>> + * stop further processing. > >>>>>> + */ > >>>>>> + return QEMU_RBD_EXIT_DIFF_ITERATE2; > >>>>> Do you have a test case for when this branch is taken? > >>>> That would happen if you diff from a snapshot, the question is if it can > >>>> also happen if the image is a clone from a snapshot? > >>>> > >>>> > >>>>>> + } > >>>>>> + if (!req->exists && exists && offs > req->offs) { > >>>>>> + /* > >>>>>> + * we started in an unallocated area and hit the first > >>>>>> allocated > >>>>>> + * block. req->bytes must be set to the length of the > >>>>>> unallocated area > >>>>>> + * before the allocated area. stop further processing. > >>>>>> + */ > >>>>>> + req->bytes = offs - req->offs; > >>>>>> + return QEMU_RBD_EXIT_DIFF_ITERATE2; > >>>>>> + } > >>>>>> + > >>>>>> + /* > >>>>>> + * assert that we caught all cases above and allocation state has > >>>>>> not > >>>>>> + * changed during callbacks. > >>>>>> + */ > >>>>>> + assert(exists == req->exists || !req->bytes); > >>>>>> + req->exists = exists; > >>>>>> + > >>>>>> + /* > >>>>>> + * assert that we either return an unallocated block or have got > >>>>>> callbacks > >>>>>> + * for all allocated blocks present. > >>>>>> + */ > >>>>>> + assert(!req->exists || offs == req->offs + req->bytes); > >>>>>> + req->bytes = offs + len - req->offs; > >>>>>> + > >>>>>> + return 0; > >>>>>> +} > >>>>>> + > >>>>>> +static int coroutine_fn qemu_rbd_co_block_status(BlockDriverState *bs, > >>>>>> + bool want_zero, > >>>>>> int64_t offset, > >>>>>> + int64_t bytes, > >>>>>> int64_t *pnum, > >>>>>> + int64_t *map, > >>>>>> + BlockDriverState > >>>>>> **file) > >>>>>> +{ > >>>>>> + BDRVRBDState *s = bs->opaque; > >>>>>> + int ret, r; > >>>>> Nit: I would rename ret to status or something like that to make > >>>>> it clear(er) that it is an actual value and never an error. Or, > >>>>> even better, drop it entirely and return one of the two bitmasks > >>>>> directly. > >>>>> > >>>>>> + struct rbd_diff_req req = { .offs = offset }; > >>>>>> + uint64_t features, flags; > >>>>>> + > >>>>>> + assert(offset + bytes <= s->image_size); > >>>>>> + > >>>>>> + /* default to all sectors allocated */ > >>>>>> + ret = BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID; > >>>>>> + *map = offset; > >>>>>> + *file = bs; > >>>>>> + *pnum = bytes; > >>>>>> + > >>>>>> + /* check if RBD image supports fast-diff */ > >>>>>> + r = rbd_get_features(s->image, &features); > >>>>>> + if (r < 0) { > >>>>>> + goto out; > >>>>>> + } > >>>>>> + if (!(features & RBD_FEATURE_FAST_DIFF)) { > >>>>>> + goto out; > >>>>>> + } > >>>>>> + > >>>>>> + /* check if RBD fast-diff result is valid */ > >>>>>> + r = rbd_get_flags(s->image, &flags); > >>>>>> + if (r < 0) { > >>>>>> + goto out; > >>>>>> + } > >>>>>> + if (flags & RBD_FLAG_FAST_DIFF_INVALID) { > >>>>>> + goto out; > >>>>> Nit: I'm not a fan of labels that cover just the return statement. > >>>>> Feel free to ignore this one but I would get rid of it and replace > >>>>> these gotos with returns. > >>>> That would be return with the bitmask directly coded in if I also > >>>> > >>>> drop the ret variable. I can change that, no problem. > >>>> > >>>> > >>>>>> + } > >>>>>> + > >>>>>> + r = rbd_diff_iterate2(s->image, NULL, offset, bytes, true, true, > >>>>>> + qemu_rbd_co_block_status_cb, &req); > >>>>>> + if (r < 0 && r != QEMU_RBD_EXIT_DIFF_ITERATE2) { > >>>>>> + goto out; > >>>>>> + } > >>>>>> + assert(req.bytes <= bytes); > >>>>>> + if (!req.exists) { > >>>>>> + if (r == 0 && !req.bytes) { > >>>>>> + /* > >>>>>> + * rbd_diff_iterate2 does not invoke callbacks for > >>>>>> unallocated areas > >>>>>> + * except for the case where an overlay has a hole where > >>>>>> the parent > >>>>>> + * has not. This here catches the case where no callback > >>>>>> was > >>>>>> + * invoked at all. > >>>>>> + */ > >>>>> The above is true in the case of diffing against a snapshot, i.e. when > >>>>> the "from" snapshot has some data where the "to" revision (whether HEAD > >>>>> or another snapshot) has a hole. I don't think it is true for child vs > >>>>> parent (but it has been a while since I looked at the diff code). As > >>>>> long as NULL is passed for fromsnapname, I would expect the callback to > >>>>> be invoked only for allocated areas. If I'm right, we could simplify > >>>>> qemu_rbd_co_block_status_cb() considerably. > >>>> See my comment in the callback. Can you look at the diff code or give > >>>> me at least a pointer where I can find it. I am not that familiar with > >>>> the librbd code yet. > >>> I assumed that you added !exists handling because it came up in your > >>> testing. If you don't have a test case then let's proceed under the > >>> assumption that it doesn't happen for clones. > >> > >> Hi Ilya, > >> > >> > >> it seems that our assumption was false. I have an image which shows holes > >> without diffing against > >> > >> a snapshot. Do you have an idea why? > >> > >> > >> $ rbd --conf /etc/ceph/ceph-dev01.conf --id lieven info > >> dhp-standard/c4ca7ee9-36ce-4fc9-9d3b-ece8a4f8b83e/c1ad11d0-4f6a-4cc1-8aa3-ff3c413c1471.raw > >> rbd image 'c1ad11d0-4f6a-4cc1-8aa3-ff3c413c1471.raw': > >> size 20 GiB in 20000 objects > >> order 20 (1 MiB objects) > >> snapshot_count: 2 > >> id: 3d6daa102e4d9f > >> block_name_prefix: rbd_data.3d6daa102e4d9f > >> format: 2 > >> features: layering, exclusive-lock, object-map, fast-diff, > >> deep-flatten > >> op_features: > >> flags: > >> create_timestamp: Tue Sep 21 14:16:56 2021 > >> access_timestamp: Thu Jan 6 15:24:46 2022 > >> modify_timestamp: Thu Jan 6 15:45:42 2022 > >> > >> > >> $ rbd --conf /etc/ceph/ceph-dev01.conf --id lieven snap ls > >> dhp-standard/c4ca7ee9-36ce-4fc9-9d3b-ece8a4f8b83e/c1ad11d0-4f6a-4cc1-8aa3-ff3c413c1471.raw > >> SNAPID NAME SIZE PROTECTED TIMESTAMP > >> 12297 dlp-20210921-144509 20 GiB Tue Sep 21 14:45:09 2021 > >> 17745 dlp-20220106-040000 20 GiB Thu Jan 6 04:00:01 2022 > >> > >> > >> $ rbd --conf /etc/ceph/ceph-dev01.conf --id lieven diff --whole-object > >> dhp-standard/c4ca7ee9-36ce-4fc9-9d3b-ece8a4f8b83e/c1ad11d0-4f6a-4cc1-8aa3-ff3c413c1471.raw > >> | grep zero > >> 204472320 1048576 zero > >> 1114636288 1048576 zero > >> 1115684864 1048576 zero > >> 1116733440 1048576 zero > >> 1117782016 1048576 zero > >> 1218445312 1048576 zero > >> 1219493888 1048576 zero > >> 1220542464 1048576 zero > > Hi Peter, > > > > Yes, I stumbled upon this just yesterday while looking into another > > librbd issue surfaced by this patch [1] and was going to email you and > > the list after wrapping my head around this behavior. I see where it > > is coming from but I'm not sure what the right fix is. I would prefer > > to patch librbd but that may turn out to be not feasible. Let me get > > back on this next week. > > > > [1] https://tracker.ceph.com/issues/53784 > > > Looks like it was a good idea to add all these asserts... > > > The issue I see does occur with a simple qemu-img convert on the given image > as source. It triggers the assert(exists) in the cb.
Right, "qemu-img convert" issues a block status request. Does your image have snapshots? This behavior should be caused by a snapshot that contains a discarded object: $ rbd create --size 16M foo $ sudo rbd map foo /dev/rbd0 $ sudo xfs_io -d -c 'pwrite -b 4M 0 16M' /dev/rbd0 wrote 16777216/16777216 bytes at offset 0 16 MiB, 4 ops; 0.4607 sec (34.726 MiB/sec and 8.6814 ops/sec) $ rbd snap create foo@snap Creating snap: 100% complete...done. $ rbd diff foo Offset Length Type 0 4194304 data 4194304 4194304 data 8388608 4194304 data 12582912 4194304 data $ blkdiscard -o 4M -l 8M /dev/rbd0 $ rbd diff foo Offset Length Type 0 4194304 data 4194304 4194304 zero 8388608 4194304 zero 12582912 4194304 data If you remove that snapshot, these "holes" should disappear from the report: $ rbd snap rm foo@snap Removing snap: 100% complete...done. $ rbd diff foo Offset Length Type 0 4194304 data 12582912 4194304 data Thanks, Ilya