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qcow2: simple case support for downgrading of qcow2 images with zstd

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If image doesn't have any compressed cluster we can easily switch to
zlib compression, which may allow to downgrade the image.

That's mostly needed to support IMGOPTS='compression_type=zstd' in some
iotests which do qcow2 downgrade.

While being here also fix checkpatch complain against '#' in printf
formatting.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20211223160144.1097696-13-vsementsov@virtuozzo.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2021-12-23 17:01:37 +01:00 committed by Hanna Reitz
parent c30175d6fb
commit 083c24561a
1 changed files with 56 additions and 2 deletions
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58
block/qcow2.c
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@ -5279,6 +5279,38 @@ static int qcow2_load_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
return bs->drv->bdrv_co_preadv_part(bs, offset, qiov->size, qiov, 0, 0);
}
static int qcow2_has_compressed_clusters(BlockDriverState *bs)
{
int64_t offset = 0;
int64_t bytes = bdrv_getlength(bs);
if (bytes < 0) {
return bytes;
}
while (bytes != 0) {
int ret;
QCow2SubclusterType type;
unsigned int cur_bytes = MIN(INT_MAX, bytes);
uint64_t host_offset;
ret = qcow2_get_host_offset(bs, offset, &cur_bytes, &host_offset,
&type);
if (ret < 0) {
return ret;
}
if (type == QCOW2_SUBCLUSTER_COMPRESSED) {
return 1;
}
offset += cur_bytes;
bytes -= cur_bytes;
}
return 0;
}
/*
* Downgrades an image's version. To achieve this, any incompatible features
* have to be removed.
@ -5336,9 +5368,10 @@ static int qcow2_downgrade(BlockDriverState *bs, int target_version,
* the first place; if that happens nonetheless, returning -ENOTSUP is the
* best thing to do anyway */
if (s->incompatible_features) {
if (s->incompatible_features & ~QCOW2_INCOMPAT_COMPRESSION) {
error_setg(errp, "Cannot downgrade an image with incompatible features "
"%#" PRIx64 " set", s->incompatible_features);
"0x%" PRIx64 " set",
s->incompatible_features & ~QCOW2_INCOMPAT_COMPRESSION);
return -ENOTSUP;
}
@ -5356,6 +5389,27 @@ static int qcow2_downgrade(BlockDriverState *bs, int target_version,
return ret;
}
if (s->incompatible_features & QCOW2_INCOMPAT_COMPRESSION) {
ret = qcow2_has_compressed_clusters(bs);
if (ret < 0) {
error_setg(errp, "Failed to check block status");
return -EINVAL;
}
if (ret) {
error_setg(errp, "Cannot downgrade an image with zstd compression "
"type and existing compressed clusters");
return -ENOTSUP;
}
/*
* No compressed clusters for now, so just chose default zlib
* compression.
*/
s->incompatible_features &= ~QCOW2_INCOMPAT_COMPRESSION;
s->compression_type = QCOW2_COMPRESSION_TYPE_ZLIB;
}
assert(s->incompatible_features == 0);
s->qcow_version = target_version;
ret = qcow2_update_header(bs);
if (ret < 0) {