04.02.2019 19:35, Vladimir Sementsov-Ogievskiy wrote: > 04.02.2019 19:24, Eric Blake wrote: >> On 2/4/19 10:03 AM, Vladimir Sementsov-Ogievskiy wrote: >> >>>>>> What would QMP clients do with this information? >>>>> >>>>> 'qemu-img info' is the intended QMP client; and it will print the >>>>> unknown-flags along with everything else. In other words, we're trying >>>>> to make qemu-img become useful for inspecting as much useful information >>>>> as possible from an image with unknown origins. Knowing that an image >>>>> uses bitmaps with flags unknown to THIS version of qemu is a good >>>>> indication that you should be careful about using/altering the image >>>>> without first upgrading qemu, as it may destroy data that some other >>>>> product desires to utilize. >>>> >>>> Okay. Now work that into the documentation :) >>>> >>> >>> I'll try: >>> >>> @unknown-flags: any flags except 'in-use' and 'auto' set for the bitmap. >>> Presence of non-zero @unknown-flags definitely shows that >>> image was created by newer version of software (which >>> supports more bitmap flags) or corrupted. Image can't be >>> used for r-w with non-zero @unknown-flags in any bitmap. >> >> The grammar still feels awkward. Maybe: >> >> @unknown-flags: If present, this is the value of additional bitmap flags >> that were set in the image but not reported in @flags, implying that the >> image was created with a newer version of software (that supports new >> flags) or has been corrupted. Modifying the image without upgrading qemu >> first will likely break the contents of the bitmap. >> > > Thank you! > > Oops, hm, I now doubt, how Andrey's patches work, if bitmap_list_load function > fails when unknown flags are found. So, can we really show unknown-flags, > or we'll fail if there any? > > And if we fail (I hope we fail) on unknown flags, than we don't need this > field :). >
But we can update bitmap_list_load, to have a flag, and show bitmaps with unknown flags in qemu-img info.. And we have to somehow not fail on open before it. I'm very sorry that I understand it all only now :(. So, do we really need unknown-flags field? If yes, may be, do it as a next step? And proceed now without them? -- Best regards, Vladimir
