Re: [Qemu-devel] [PATCH v4 03/23] block: Make bdrv_round_to_clusters() signature more useful

[John Snow <jsnow@redhat.com>]

On 09/13/2017 12:03 PM, Eric Blake wrote:
> In the process of converting sector-based interfaces to bytes,
> I'm finding it easier to represent a byte count as a 64-bit
> integer at the block layer (even if we are internally capped
> by SIZE_MAX or even INT_MAX for individual transactions, it's
> still nicer to not have to worry about truncation/overflow
> issues on as many variables).  Update the signature of
> bdrv_round_to_clusters() to uniformly use int64_t, matching
> the signature already chosen for bdrv_is_allocated and the
> fact that off_t is also a signed type, then adjust clients
> according to the required fallout.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: Fam Zheng <famz@redhat.com>
> 
> ---
> v4: only context changes
> v3: no change
> v2: fix commit message [John], rebase to earlier changes, including
> mirror_clip_bytes() signature update
> ---
>  include/block/block.h | 4 ++--
>  block/io.c            | 7 ++++---
>  block/mirror.c        | 7 +++----
>  block/trace-events    | 2 +-
>  4 files changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/include/block/block.h b/include/block/block.h
> index 2ad18775af..bb3b95d491 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -475,9 +475,9 @@ int bdrv_get_flags(BlockDriverState *bs);
>  int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi);
>  ImageInfoSpecific *bdrv_get_specific_info(BlockDriverState *bs);
>  void bdrv_round_to_clusters(BlockDriverState *bs,
> -                            int64_t offset, unsigned int bytes,
> +                            int64_t offset, int64_t bytes,
>                              int64_t *cluster_offset,
> -                            unsigned int *cluster_bytes);
> +                            int64_t *cluster_bytes);
> 
>  const char *bdrv_get_encrypted_filename(BlockDriverState *bs);
>  void bdrv_get_backing_filename(BlockDriverState *bs,
> diff --git a/block/io.c b/block/io.c
> index 6509c804d4..b362b46e3d 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -446,9 +446,9 @@ static void mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
>   * Round a region to cluster boundaries
>   */
>  void bdrv_round_to_clusters(BlockDriverState *bs,
> -                            int64_t offset, unsigned int bytes,
> +                            int64_t offset, int64_t bytes,
>                              int64_t *cluster_offset,
> -                            unsigned int *cluster_bytes)
> +                            int64_t *cluster_bytes)
>  {
>      BlockDriverInfo bdi;
> 
> @@ -946,7 +946,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
>      struct iovec iov;
>      QEMUIOVector bounce_qiov;
>      int64_t cluster_offset;
> -    unsigned int cluster_bytes;
> +    int64_t cluster_bytes;
>      size_t skip_bytes;
>      int ret;
> 
> @@ -967,6 +967,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
>      trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
>                                     cluster_offset, cluster_bytes);
> 
> +    assert(cluster_bytes < SIZE_MAX);

later in this function, is there any real or imagined risk of
cluster_bytes exceeding INT_MAX when it's passed to
bdrv_co_do_pwrite_zeroes?

>      iov.iov_len = cluster_bytes;
>      iov.iov_base = bounce_buffer = qemu_try_blockalign(bs, iov.iov_len);
>      if (bounce_buffer == NULL) {
> diff --git a/block/mirror.c b/block/mirror.c
> index 032cfe91fa..67f45cec4e 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -190,10 +190,9 @@ static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset,
>      bool need_cow;
>      int ret = 0;
>      int64_t align_offset = *offset;
> -    unsigned int align_bytes = *bytes;
> +    int64_t align_bytes = *bytes;
>      int max_bytes = s->granularity * s->max_iov;
> 
> -    assert(*bytes < INT_MAX);
>      need_cow = !test_bit(*offset / s->granularity, s->cow_bitmap);
>      need_cow |= !test_bit((*offset + *bytes - 1) / s->granularity,
>                            s->cow_bitmap);
> @@ -388,7 +387,7 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
>      while (nb_chunks > 0 && offset < s->bdev_length) {
>          int64_t ret;
>          int io_sectors;
> -        unsigned int io_bytes;
> +        int64_t io_bytes;
>          int64_t io_bytes_acct;
>          enum MirrorMethod {
>              MIRROR_METHOD_COPY,
> @@ -413,7 +412,7 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
>              io_bytes = s->granularity;
>          } else if (ret >= 0 && !(ret & BDRV_BLOCK_DATA)) {
>              int64_t target_offset;
> -            unsigned int target_bytes;
> +            int64_t target_bytes;
>              bdrv_round_to_clusters(blk_bs(s->target), offset, io_bytes,
>                                     &target_offset, &target_bytes);
>              if (target_offset == offset &&
> diff --git a/block/trace-events b/block/trace-events
> index 25dd5a3026..4c6586f156 100644
> --- a/block/trace-events
> +++ b/block/trace-events
> @@ -12,7 +12,7 @@ blk_co_pwritev(void *blk, void *bs, int64_t offset, unsigned int bytes, int flag
>  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, unsigned int cluster_bytes) "bs %p offset %"PRId64" bytes %u cluster_offset %"PRId64" cluster_bytes %u"
> +bdrv_co_do_copy_on_readv(void *bs, int64_t offset, int64_t bytes, int64_t cluster_offset, unsigned int cluster_bytes) "bs %p offset %"PRId64" bytes %"PRId64" cluster_offset %"PRId64" cluster_bytes %u"
> 
>  # block/stream.c
>  stream_one_iteration(void *s, int64_t offset, uint64_t bytes, int is_allocated) "s %p offset %" PRId64 " bytes %" PRIu64 " is_allocated %d"
> 

Everything else looks obviously correct to me.