Am 29.01.2019 um 16:29 hat Vladimir Sementsov-Ogievskiy geschrieben: > 29.01.2019 17:35, Vladimir Sementsov-Ogievskiy wrote: > > 29.01.2019 17:23, Kevin Wolf wrote: > >> Am 29.01.2019 um 15:06 hat Vladimir Sementsov-Ogievskiy geschrieben: > >>> 29.01.2019 16:17, Kevin Wolf wrote: > >>>> Am 29.01.2019 um 13:50 hat Vladimir Sementsov-Ogievskiy geschrieben: > >>>>> 29.01.2019 15:38, Kevin Wolf wrote: > >>>>>> Am 29.01.2019 um 13:04 hat Andrey Shinkevich geschrieben: > >>>>>>>>> > >>>>>>>>> diff --git a/block/qapi.c b/block/qapi.c > >>>>>>>>> index c66f949..0fde98c 100644 > >>>>>>>>> --- a/block/qapi.c > >>>>>>>>> +++ b/block/qapi.c > >>>>>>>>> @@ -38,6 +38,7 @@ > >>>>>>>>> #include "qapi/qmp/qstring.h" > >>>>>>>>> #include "sysemu/block-backend.h" > >>>>>>>>> #include "qemu/cutils.h" > >>>>>>>>> +#include "qemu/error-report.h" > >>>>>>>>> BlockDeviceInfo *bdrv_block_device_info(BlockBackend *blk, > >>>>>>>>> BlockDriverState *bs, > >>>>>>>>> Error **errp) > >>>>>>>>> @@ -868,6 +869,11 @@ void bdrv_image_info_dump(fprintf_function > >>>>>>>>> func_fprintf, void *f, > >>>>>>>>> if (info->has_format_specific) { > >>>>>>>>> func_fprintf(f, "Format specific information:\n"); > >>>>>>>>> + if (info->format_specific && > >>>>>>>>> + info->format_specific->type == > >>>>>>>>> IMAGE_INFO_SPECIFIC_KIND_QCOW2 && > >>>>>>>>> + info->format_specific->u.qcow2.data->has_bitmaps == > >>>>>>>>> false) { > >>>>>>>>> + warn_report("Failed to load bitmap list"); > >>>>>>>>> + } > >>>>>>>>> bdrv_image_info_specific_dump(func_fprintf, f, > >>>>>>>>> info->format_specific); > >>>>>>>>> } > >>>>>>>>> } > >>>>>>>> > >>>>>>>> Is it really necessary to introduce qcow2 specific knowledge in > >>>>>>>> block/qapi.c (where it definitely doesn't belong), just to emit a > >>>>>>>> warning? > >>>>>>>> > >>>>>>>> Why can't you print the warning in qcow2_get_specific_info()? > >>>>>>> > >>>>>>> Dear Kevin, > >>>>>>> The reason behind the idea to move the warning to qapi is that we > >>>>>>> wouldn't like to print that in case of JSON format. > >>>>>>> > >>>>>>>> > >>>>>>>>> diff --git a/block/qcow2.c b/block/qcow2.c > >>>>>>>>> index 4897aba..07b99ee 100644 > >>>>>>>>> --- a/block/qcow2.c > >>>>>>>>> +++ b/block/qcow2.c > >>>>>>>>> @@ -4386,8 +4386,14 @@ static ImageInfoSpecific > >>>>>>>>> *qcow2_get_specific_info(BlockDriverState *bs) > >>>>>>>>> *spec_info->u.qcow2.data = (ImageInfoSpecificQCow2){ > >>>>>>>>> .compat = g_strdup("0.10"), > >>>>>>>>> .refcount_bits = s->refcount_bits, > >>>>>>>>> + .has_bitmaps = true, /* To handle error check > >>>>>>>>> properly */ > >>>>>>>>> + .bitmaps = NULL, /* Unsupported for version > >>>>>>>>> 2 */ > >>>>>>>> > >>>>>>>> .has_bitmaps = false would be nicer if the format doesn't even > >>>>>>>> support > >>>>>>>> bitmaps. You only need this here because you put the warning in the > >>>>>>>> wrong place. > >>>>>>>> > >>>>>>>>> }; > >>>>>>>>> } else if (s->qcow_version == 3) { > >>>>>>>>> + Qcow2BitmapInfoList *bitmaps; > >>>>>>>>> + Error *local_err = NULL; > >>>>>>>>> + > >>>>>>>>> + bitmaps = qcow2_get_bitmap_info_list(bs, &local_err); > >>>>>>>> > >>>>>>>> Here you even had a good error message to print... > >>>>>>>> > >>>>>>>>> *spec_info->u.qcow2.data = (ImageInfoSpecificQCow2){ > >>>>>>>>> .compat = g_strdup("1.1"), > >>>>>>>>> .lazy_refcounts = s->compatible_features & > >>>>>>>>> @@ -4397,7 +4403,14 @@ static ImageInfoSpecific > >>>>>>>>> *qcow2_get_specific_info(BlockDriverState *bs) > >>>>>>>>> QCOW2_INCOMPAT_CORRUPT, > >>>>>>>>> .has_corrupt = true, > >>>>>>>>> .refcount_bits = s->refcount_bits, > >>>>>>>>> + .has_bitmaps = !local_err, > >>>>>>>>> + .bitmaps = bitmaps, > >>>>>>>>> }; > >>>>>>>>> + /* > >>>>>>>>> + * If an error occurs in obtaining bitmaps, ignore > >>>>>>>>> + * it to show other QCOW2 specific information. > >>>>>>>>> + */ > >>>>>>>>> + error_free(local_err); > >>>>>>>> > >>>>>>>> ...but you decided to discard it. > >>>>>>>> > >>>>>>>> How about you do this here: > >>>>>>>> > >>>>>>>> warn_reportf_err(local_err, "Failed to load bitmap list: "); > >>>>>>> > >>>>>>> In case of JSON format, we can fail here. > >>>>>>> It will happen in the current implementation of the new test #239. > >>>>>> > >>>>>> Why do you want to silently leave out the bitmap list for JSON output? > >>>>>> > >>>>>> Essentially, this is the same question I asked here: > >>>>>> > >>>>>>>> And then get rid of the code in block/qapi.c and the version 2 path? > >>>>>>>> > >>>>>>>> Actually, should this really only be a warning, or in fact an error? > >>>>>>>> What's the case where we expect that loading the bitmap list can > >>>>>>>> fail, > >>>>>>>> but the management tool doesn't need to know that and we just want to > >>>>>>>> log a message? > >>>>>> > >>>>>> I don't understand why it's okay not to print bitmaps without making it > >>>>>> an error. Do you have a specific use case in mind for this behaviour? > >>>>>> > >>>>> > >>>>> > >>>>> We just can't print anything here, as this code is executed from qmp > >>>>> command. > >>>>> > >>>>> It was discussed, that we don't want to fail the whole query, if failed > >>>>> to > >>>>> obtain bitmaps. > >>>> > >>>> It's obvious that you don't want to fail the query command, but I > >>>> haven't found any explanation for _why_ you want this. > >>>> > >>>> The thing that is closest to an explanation is "it may be sad to fail > >>>> get any information because of repeating some disk/qcow2 error", written > >>>> by you in the v4 thread. > >>>> > >>>> I don't think "may be sad" is a good justification for non-standard > >>>> behaviour. If we can't load the bitmaps, the image is broken. And if the > >>>> image is broken, the rest of the information may be invalid, too. > >>> > >>> So, you mean that we go wrong way. And it was my idea. That is sad too. > >>> > >>> Than, seems like we should add errp to the function and to the full stack > >>> down to qmp_query_block. And drop extra partial-success qapi logic. > >> > >> I'm not necessarily saying that it's the wrong way, though possibly it > >> is wrong indeed. > >> > >> But ignoring some kind of failures is special, so what I was looking for > >> were comments or documentation to explain the reason behind it at least. > >> Now from the replies I got so far it looks to me that possibly the > >> reasons are not only undocumented, but we might actually not have any. > >> > >>>>> So, to show, that there were error during bitmaps querying > >>>>> we decided to use the following semantics: > >>>>> > >>>>> empty list (has_bitmaps=true) means that there no bitmaps, and there > >>>>> were > >>>>> no errors during bitmaps quering (if it was) > >>>>> > >>>>> absence of the field (has_bitmaps=false) means that there _were_ errors > >>>>> during > >>>>> bitmaps querying. > >>>> > >>>> ...or that you're running an old QEMU version. I'm not sure if making > >>>> old QEMU versions and image errors look the same is a good move. > >>> > >>> No, for old versions we return empty list, to show that there were no > >>> errors. > >> > >> You mean old image format versions? > > > > yes. > > > > I'm talking about old QEMU versions > >> that don't even know the 'bitmaps' field. > > > > hmm. Yes, that's a problem, which we didn't considered. > > > >> > >> A QMP client would have to parse the schema to understand whether a > >> missing 'bitmaps' field means that it's talking to an old QEMU (then > >> 'bitmaps' doesn't exist in the schema), or that an error happened (then > >> the field does exist in the schema). > >> > >> Looking at the schema is not impossible, so if we require this for a > >> good reason, it's okay. But it's not trivial either. If we really want > >> to go with this semantics, we should probably mention both the old and > >> the new meaning in the QAPI documentation, with the recommendation that > >> you parse the schema to determine the meaning of a missing 'bitmaps' > >> field. > > > > Hm, now I think that if we really face the case when we need partial success > > of info querying, it should be additional optional parameter which enables > > it, like > > skip-failed=true (default false) or something, which is more clear than > > parsing the > > schema. And, which we can add later if needed. > > Note also, that we already skip some errors, for example, > block_crypto_get_specific_info_luks > will return NULL on errors (unlike qcow2_get_specific_info, which aborts), and > bdrv_query_image_info skip these errors, in same manner as for formats which > don't support > bdrv_get_specific_info. > > Looks like a good moment to fix this too, do you agree?
Yes, once we add an Error **errp to .bdrv_get_specific_info, returning errors for failing qcrypto_block_get_info() calls as well (both in crypto and qcow2) makes sense to me. Or in fact, remove the errp parameter from qcrypto_block_get_info(). It seems to never return errors. Kevin