Re: [PATCH v2 4/6] block: support compressed write for copy-on-read

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

02.10.2019 17:22, Andrey Shinkevich wrote:
> Support the data compression during block-stream job over a backup
> backing chain implemented in the following patch 'block-stream:
> add compress option'.
> 
> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>   block/io.c         | 21 ++++++++++++++++-----
>   block/trace-events |  2 +-
>   2 files changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/block/io.c b/block/io.c
> index f8c3596..a7cd24f 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -1264,12 +1264,13 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
>        * allocating cluster in the image file.  Note that this value may exceed
>        * BDRV_REQUEST_MAX_BYTES (even when the original read did not), which
>        * is one reason we loop rather than doing it all at once.
> +     * Also, this is crucial for compressed copy-on-read.
>        */
>       bdrv_round_to_clusters(bs, offset, bytes, &cluster_offset, &cluster_bytes);
>       skip_bytes = offset - cluster_offset;
>   
>       trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
> -                                   cluster_offset, cluster_bytes);
> +                                   cluster_offset, cluster_bytes, flags);
>   
>       while (cluster_bytes) {
>           int64_t pnum;
> @@ -1328,9 +1329,15 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
>                   /* This does not change the data on the disk, it is not
>                    * necessary to flush even in cache=writethrough mode.
>                    */
> -                ret = bdrv_driver_pwritev(bs, cluster_offset, pnum,
> -                                          &local_qiov, 0,
> -                                          BDRV_REQ_WRITE_UNCHANGED);
> +                if (flags & BDRV_REQ_WRITE_COMPRESSED) {
> +                    ret = bdrv_driver_pwritev_compressed(bs, cluster_offset,
> +                                                         pnum, &local_qiov,
> +                                                         qiov_offset);

qiov_offset is wrong: you should use 0 together with local_qiov, as local_qiov is buffer with
data to be written.

> +                } else {
> +                    ret = bdrv_driver_pwritev(bs, cluster_offset, pnum,
> +                                              &local_qiov, 0,
> +                                              BDRV_REQ_WRITE_UNCHANGED);
> +                }
>               }
>   
>               if (ret < 0) {
> @@ -1396,7 +1403,11 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
>        * to pass through to drivers.  For now, there aren't any
>        * passthrough flags.  */
>       assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ |
> -                       BDRV_REQ_PREFETCH)));
> +                       BDRV_REQ_PREFETCH | BDRV_REQ_WRITE_COMPRESSED)));
> +
> +    /* write compressed only makes sense with copy on read */
> +    assert(!(flags & BDRV_REQ_WRITE_COMPRESSED) ||
> +           (flags & BDRV_REQ_COPY_ON_READ));
>   
>       /* Handle Copy on Read and associated serialisation */
>       if (flags & BDRV_REQ_COPY_ON_READ) {
> diff --git a/block/trace-events b/block/trace-events
> index 3aa27e6..f444548 100644
> --- a/block/trace-events
> +++ b/block/trace-events
> @@ -14,7 +14,7 @@ blk_root_detach(void *child, void *blk, void *bs) "child %p blk %p bs %p"
>   bdrv_co_preadv(void *bs, int64_t offset, int64_t nbytes, unsigned int flags) "bs %p offset %"PRId64" nbytes %"PRId64" flags 0x%x"
>   bdrv_co_pwritev(void *bs, int64_t offset, int64_t nbytes, unsigned int flags) "bs %p offset %"PRId64" nbytes %"PRId64" flags 0x%x"
>   bdrv_co_pwrite_zeroes(void *bs, int64_t offset, int count, int flags) "bs %p offset %"PRId64" count %d flags 0x%x"
> -bdrv_co_do_copy_on_readv(void *bs, int64_t offset, unsigned int bytes, int64_t cluster_offset, int64_t cluster_bytes) "bs %p offset %"PRId64" bytes %u cluster_offset %"PRId64" cluster_bytes %"PRId64
> +bdrv_co_do_copy_on_readv(void *bs, int64_t offset, unsigned int bytes, int64_t cluster_offset, int64_t cluster_bytes, int flags) "bs %p offset %"PRId64" bytes %u cluster_offset %"PRId64" cluster_bytes %"PRId64" flags 0x%x"
>   bdrv_co_copy_range_from(void *src, uint64_t src_offset, void *dst, uint64_t dst_offset, uint64_t bytes, int read_flags, int write_flags) "src %p offset %"PRIu64" dst %p offset %"PRIu64" bytes %"PRIu64" rw flags 0x%x 0x%x"
>   bdrv_co_copy_range_to(void *src, uint64_t src_offset, void *dst, uint64_t dst_offset, uint64_t bytes, int read_flags, int write_flags) "src %p offset %"PRIu64" dst %p offset %"PRIu64" bytes %"PRIu64" rw flags 0x%x 0x%x"
>   
> 


-- 
Best regards,
Vladimir