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block/qcow2-bitmap: Allow resizes with persistent bitmaps

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Since we now load all bitmaps into memory anyway, we can just truncate
them in-memory and then flush them back to disk. Just in case, we will
still check and enforce that this shortcut is valid -- i.e. that any
bitmap described on-disk is indeed in-memory and can be modified.

If there are any inconsistent bitmaps, we refuse to allow the truncate
as we do not actually load these bitmaps into memory, and it isn't safe
or reasonable to attempt to truncate corrupted data.

Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190311185147.52309-4-vsementsov@virtuozzo.com
  [vsementsov: drop bitmap flushing, fix block comments style]
Signed-off-by: John Snow <jsnow@redhat.com>
This commit is contained in:
John Snow 2019-03-11 21:51:46 +03:00
parent bf5f0cf5d8
commit d19c6b36ff
3 changed files with 48 additions and 3 deletions
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4
block/qcow2.c
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@ -3646,9 +3646,7 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
}
/* cannot proceed if image has bitmaps */
if (s->nb_bitmaps) {
/* TODO: resize bitmaps in the image */
error_setg(errp, "Can't resize an image which has bitmaps");
if (qcow2_truncate_bitmaps_check(bs, errp)) {
ret = -ENOTSUP;
goto fail;
}