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qcow2: truncate the tail of the image file after shrinking the image

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Now after shrinking the image, at the end of the image file, there might be a
tail that probably will never be used. So we can find the last used cluster and
cut the tail.

Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20170929121613.25997-3-pbutsykin@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Pavel Butsykin 2017-09-29 15:16:13 +03:00 • committed by Max Reitz
parent 76a2a30a99
commit 163bc39d2c
3 changed files with 46 additions and 0 deletions
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22
block/qcow2-refcount.c
View file

@ -3181,3 +3181,25 @@ out:
g_free(reftable_tmp);
return ret;
}
int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size)
{
BDRVQcow2State *s = bs->opaque;
int64_t i;
for (i = size_to_clusters(s, size) - 1; i >= 0; i--) {
uint64_t refcount;
int ret = qcow2_get_refcount(bs, i, &refcount);
if (ret < 0) {
fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n",
i, strerror(-ret));
return ret;
}
if (refcount > 0) {
return i;
}
}
qcow2_signal_corruption(bs, true, -1, -1,
"There are no references in the refcount table.");
return -EIO;
}