Re: [Qemu-devel] [PATCH v2 2/6] block: Add ImageInfoSpecific to BlockDriverInfo

[Fam Zheng <famz@redhat.com>]

On Fri, 09/06 15:12, Max Reitz wrote:
> Add the new ImageInfoSpecific type also to BlockDriverInfo.
> 
> To prevent memory leaks, this field has to be initialized to NULL every
> time before calling bdrv_get_info and qapi_free_ImageInfoSpecific has to
> be called on it when the BlockDriverInfo object is no longer required.
> 
I don't understand here. I think bdi is always passed into bdrv_get_info()
uninitialized and in bdrv_get_info() there is:

    memset(bdi, 0, sizeof(*bdi));

before passing it on to driver, so it's always set to NULL.

And why pointer, not a member to save a free() call?

> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block.c               | 3 ++-
>  block/mirror.c        | 6 ++++--
>  block/qapi.c          | 6 +++++-
>  include/block/block.h | 2 ++
>  qemu-img.c            | 3 ++-
>  qemu-io-cmds.c        | 6 +++++-
>  6 files changed, 20 insertions(+), 6 deletions(-)
> 
> diff --git a/block.c b/block.c
> index 26639e8..1a5d2a4 100644
> --- a/block.c
> +++ b/block.c
> @@ -1921,7 +1921,7 @@ void bdrv_round_to_clusters(BlockDriverState *bs,
>                              int64_t *cluster_sector_num,
>                              int *cluster_nb_sectors)
>  {
> -    BlockDriverInfo bdi;
> +    BlockDriverInfo bdi = { .format_specific = NULL };
>  
>      if (bdrv_get_info(bs, &bdi) < 0 || bdi.cluster_size == 0) {
>          *cluster_sector_num = sector_num;
> @@ -1932,6 +1932,7 @@ void bdrv_round_to_clusters(BlockDriverState *bs,
>          *cluster_nb_sectors = QEMU_ALIGN_UP(sector_num - *cluster_sector_num +
>                                              nb_sectors, c);
>      }
> +    qapi_free_ImageInfoSpecific(bdi.format_specific);
>  }
>  
>  static bool tracked_request_overlaps(BdrvTrackedRequest *req,
> diff --git a/block/mirror.c b/block/mirror.c
> index 86de458..cfef7e9 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -295,7 +295,7 @@ static void coroutine_fn mirror_run(void *opaque)
>      BlockDriverState *bs = s->common.bs;
>      int64_t sector_num, end, sectors_per_chunk, length;
>      uint64_t last_pause_ns;
> -    BlockDriverInfo bdi;
> +    BlockDriverInfo bdi = { .format_specific = NULL };
>      char backing_filename[1024];
>      int ret = 0;
>      int n;
> @@ -325,6 +325,7 @@ static void coroutine_fn mirror_run(void *opaque)
>              s->buf_size = MAX(s->buf_size, bdi.cluster_size);
>              s->cow_bitmap = bitmap_new(length);
>          }
> +        qapi_free_ImageInfoSpecific(bdi.format_specific);
>      }
>  
>      end = s->common.len >> BDRV_SECTOR_BITS;
> @@ -544,13 +545,14 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target,
>      if (granularity == 0) {
>          /* Choose the default granularity based on the target file's cluster
>           * size, clamped between 4k and 64k.  */
> -        BlockDriverInfo bdi;
> +        BlockDriverInfo bdi = { .format_specific = NULL };
>          if (bdrv_get_info(target, &bdi) >= 0 && bdi.cluster_size != 0) {
>              granularity = MAX(4096, bdi.cluster_size);
>              granularity = MIN(65536, granularity);
>          } else {
>              granularity = 65536;
>          }
> +        qapi_free_ImageInfoSpecific(bdi.format_specific);
>      }
>  
>      assert ((granularity & (granularity - 1)) == 0);
> diff --git a/block/qapi.c b/block/qapi.c
> index a4bc411..f13fbd5 100644
> --- a/block/qapi.c
> +++ b/block/qapi.c
> @@ -110,7 +110,7 @@ void bdrv_query_image_info(BlockDriverState *bs,
>      uint64_t total_sectors;
>      const char *backing_filename;
>      char backing_filename2[1024];
> -    BlockDriverInfo bdi;
> +    BlockDriverInfo bdi = { .format_specific = NULL };
>      int ret;
>      Error *err = NULL;
>      ImageInfo *info = g_new0(ImageInfo, 1);
> @@ -133,6 +133,10 @@ void bdrv_query_image_info(BlockDriverState *bs,
>          }
>          info->dirty_flag = bdi.is_dirty;
>          info->has_dirty_flag = true;
> +        if (bdi.format_specific) {
> +            info->format_specific = bdi.format_specific;
> +            info->has_format_specific = true;
> +        }
>      }
>      backing_filename = bs->backing_file;
>      if (backing_filename[0] != '\0') {
> diff --git a/include/block/block.h b/include/block/block.h
> index e6b391c..85e9703 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -18,6 +18,8 @@ typedef struct BlockDriverInfo {
>      /* offset at which the VM state can be saved (0 if not possible) */
>      int64_t vm_state_offset;
>      bool is_dirty;
> +    /* additional information; NULL if none */
> +    ImageInfoSpecific *format_specific;
>  } BlockDriverInfo;
>  
>  typedef struct BlockFragInfo {
> diff --git a/qemu-img.c b/qemu-img.c
> index b9a848d..ec1ecca 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -1125,7 +1125,7 @@ static int img_convert(int argc, char **argv)
>      uint64_t bs_sectors;
>      uint8_t * buf = NULL;
>      const uint8_t *buf1;
> -    BlockDriverInfo bdi;
> +    BlockDriverInfo bdi = { .format_specific = NULL };
>      QEMUOptionParameter *param = NULL, *create_options = NULL;
>      QEMUOptionParameter *out_baseimg_param;
>      char *options = NULL;
> @@ -1369,6 +1369,7 @@ static int img_convert(int argc, char **argv)
>              error_report("could not get block driver info");
>              goto out;
>          }
> +        qapi_free_ImageInfoSpecific(bdi.format_specific);
>          cluster_size = bdi.cluster_size;
>          if (cluster_size <= 0 || cluster_size > IO_BUF_SIZE) {
>              error_report("invalid cluster size");
> diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
> index f91b6c4..563dd40 100644
> --- a/qemu-io-cmds.c
> +++ b/qemu-io-cmds.c
> @@ -1677,7 +1677,7 @@ static const cmdinfo_t length_cmd = {
>  
>  static int info_f(BlockDriverState *bs, int argc, char **argv)
>  {
> -    BlockDriverInfo bdi;
> +    BlockDriverInfo bdi = { .format_specific = NULL };
>      char s1[64], s2[64];
>      int ret;
>  
> @@ -1699,6 +1699,10 @@ static int info_f(BlockDriverState *bs, int argc, char **argv)
>      printf("cluster size: %s\n", s1);
>      printf("vm state offset: %s\n", s2);
>  
> +    if (bdi.format_specific) {
> +        qapi_free_ImageInfoSpecific(bdi.format_specific);
> +    }
> +
>      return 0;
>  }
>  
> -- 
> 1.8.3.1
> 
>