On 6/21/23 20:46, Denis V. Lunev wrote:
> On 6/21/23 19:08, Denis V. Lunev wrote:
>> On 6/7/23 17:26, Andrey Drobyshev wrote:
>>> Functions qcow2_get_host_offset(), get_cluster_offset() explicitly
>>> report compressed cluster types when data is compressed. However, this
>>> information is never passed further. Let's make use of it by adding new
>>> BDRV_BLOCK_COMPRESSED flag for bdrv_block_status(), so that caller may
>>> know that the data range is compressed. In particular, we're going to
>>> use this flag to tweak "qemu-img map" output.
>>>
>>> This new flag is only being utilized by qcow and qcow2 formats, as only
>>> these two support compression.
>>>
>>> Signed-off-by: Andrey Drobyshev <andrey.drobys...@virtuozzo.com>
>>> ---
>>> block/qcow.c | 5 ++++-
>>> block/qcow2.c | 3 +++
>>> include/block/block-common.h | 3 +++
>>> 3 files changed, 10 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/block/qcow.c b/block/qcow.c
>>> index 3644bbf5cb..8416bcc2c3 100644
>>> --- a/block/qcow.c
>>> +++ b/block/qcow.c
>>> @@ -549,7 +549,10 @@ qcow_co_block_status(BlockDriverState *bs, bool
>>> want_zero,
>>> if (!cluster_offset) {
>>> return 0;
>>> }
>>> - if ((cluster_offset & QCOW_OFLAG_COMPRESSED) || s->crypto) {
>>> + if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
>>> + return BDRV_BLOCK_DATA | BDRV_BLOCK_COMPRESSED;
>>> + }
>>> + if (s->crypto) {
>>> return BDRV_BLOCK_DATA;
>>> }
>>> *map = cluster_offset | index_in_cluster;
>>> diff --git a/block/qcow2.c b/block/qcow2.c
>>> index e23edd48c2..8e01adc610 100644
>>> --- a/block/qcow2.c
>>> +++ b/block/qcow2.c
>>> @@ -2162,6 +2162,9 @@ qcow2_co_block_status(BlockDriverState *bs,
>>> bool want_zero, int64_t offset,
>>> {
>>> status |= BDRV_BLOCK_RECURSE;
>>> }
>>> + if (type == QCOW2_SUBCLUSTER_COMPRESSED) {
>>> + status |= BDRV_BLOCK_COMPRESSED;
>>> + }
>>> return status;
>>> }
>>> diff --git a/include/block/block-common.h
>>> b/include/block/block-common.h
>>> index e15395f2cb..f7a4e7d4db 100644
>>> --- a/include/block/block-common.h
>>> +++ b/include/block/block-common.h
>>> @@ -282,6 +282,8 @@ typedef enum {
>>> * layer rather than any backing, set by
>>> block layer
>>> * BDRV_BLOCK_EOF: the returned pnum covers through end of file for
>>> this
>>> * layer, set by block layer
>>> + * BDRV_BLOCK_COMPRESSED: the underlying data is compressed; only
>>> valid for
>>> + * the formats supporting compression: qcow,
>>> qcow2
>>> *
>>> * Internal flags:
>>> * BDRV_BLOCK_RAW: for use by passthrough drivers, such as raw, to
>>> request
>>> @@ -317,6 +319,7 @@ typedef enum {
>>> #define BDRV_BLOCK_ALLOCATED 0x10
>>> #define BDRV_BLOCK_EOF 0x20
>>> #define BDRV_BLOCK_RECURSE 0x40
>>> +#define BDRV_BLOCK_COMPRESSED 0x80
>>> typedef QTAILQ_HEAD(BlockReopenQueue, BlockReopenQueueEntry)
>>> BlockReopenQueue;
>> Reviewed-by: Denis V. Lunev <d...@openvz.org>
> Looking into the second patch I have found that I was a too fast here :)
>
> The comment is misleading and the patch is incomplete.
>
> static inline bool TSA_NO_TSA block_driver_can_compress(BlockDriver *drv)
> {
> return drv->bdrv_co_pwritev_compressed ||
> drv->bdrv_co_pwritev_compressed_part;
> }
>
> which means that
>
> 1 257 block/copy-on-read.c <<GLOBAL>>
> .bdrv_co_pwritev_compressed = cor_co_pwritev_compressed,
> 2 1199 block/qcow.c <<GLOBAL>>
> .bdrv_co_pwritev_compressed = qcow_co_pwritev_compressed,
> 3 255 block/throttle.c <<GLOBAL>>
> .bdrv_co_pwritev_compressed = throttle_co_pwritev_compressed,
> 4 3108 block/vmdk.c <<GLOBAL>>
> .bdrv_co_pwritev_compressed = vmdk_co_pwritev_compressed,
> 1 6121 block/qcow2.c <<GLOBAL>>
> .bdrv_co_pwritev_compressed_part...cow2_co_pwritev_compressed_part,
>
> We have missed at least VMDK images.
Thanks, my bad I didn't check that more thoroughly, I was mainly looking
in the docs when making this conclusion.
man qemu-img:
> Only the formats qcow and qcow2 support compression. The com‐
> pression is read-only. It means that if a compressed sector is
> rewritten, then it is rewritten as uncompressed data.
Apparently man pages got a bit outdated on this.
