qemu-img: Add --skip-broken-bitmaps for 'convert --bitmaps'

The point of 'qemu-img convert --bitmaps' is to be a convenience for
actions that are already possible through a string of smaller
'qemu-i

qemu-img: Add --skip-broken-bitmaps for 'convert --bitmaps'

The point of 'qemu-img convert --bitmaps' is to be a convenience for
actions that are already possible through a string of smaller
'qemu-img bitmap' sub-commands. One situation not accounted for
already is that if a source image contains an inconsistent bitmap (for
example, because a qemu process died abruptly before flushing bitmap
state), the user MUST delete those inconsistent bitmaps before
anything else useful can be done with the image.

We don't want to delete inconsistent bitmaps by default: although a
corrupt bitmap is only a loss of optimization rather than a corruption
of user-visible data, it is still nice to require the user to opt in
to the fact that they are aware of the loss of the bitmap. Still,
requiring the user to check 'qemu-img info' to see whether bitmaps are
consistent, then use 'qemu-img bitmap --remove' to remove offenders,
all before using 'qemu-img convert', is a lot more work than just
adding a knob 'qemu-img convert --bitmaps --skip-broken-bitmaps' which
opts in to skipping the broken bitmaps.

After testing the new option, also demonstrate the way to manually fix
things (either deleting bad bitmaps, or re-creating them as empty) so
that it is possible to convert without the option.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1946084
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210709153951.2801666-4-eblake@redhat.com>
[eblake: warning message tweak, test enhancements]
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

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qemu-img: Fail fast on convert --bitmaps with inconsistent bitmap

Waiting until the end of the convert operation (a potentially
time-consuming task) to finally detect that we can't copy a bitmap is

qemu-img: Fail fast on convert --bitmaps with inconsistent bitmap

Waiting until the end of the convert operation (a potentially
time-consuming task) to finally detect that we can't copy a bitmap is
bad, comparing to failing fast up front. Furthermore, this prevents
us from leaving a file behind with a bitmap that is not marked as
inconsistent even though it does not have sane contents.

This fixes the problems exposed in the previous patch to the iotest:
it adds a fast failure up front, and even if we don't fail early, it
ensures that any bitmap we add but do not properly populate is removed
again rather than left behind incomplete.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210709153951.2801666-3-eblake@redhat.com>
[eblake: add a hint to the warning message, simplify name computation]
Reviewed-by: Nir Soffer <nsoffer@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

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iotests: Improve and rename test 291 to qemu-img-bitmap

Enhance the test to demonstrate existing less-than-stellar behavior of
qemu-img with a qcow2 image containing an inconsistent bitmap: we
don't

iotests: Improve and rename test 291 to qemu-img-bitmap

Enhance the test to demonstrate existing less-than-stellar behavior of
qemu-img with a qcow2 image containing an inconsistent bitmap: we
don't diagnose the problem until after copying the entire image (a
potentially long time), and when we do diagnose the failure, we still
end up leaving an empty bitmap in the destination. This mess will be
cleaned up in the next patch.

While at it, rename the test now that we support useful iotest names,
and fix a missing newline in the error message thus exposed.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210709153951.2801666-2-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Nir Soffer <nsoffer@redhat.com>

show more ...