Re: [Qemu-devel] [PATCH 09/10] block: Reuse success path from bdrv_open()

[Jeff Cody <jcody@redhat.com>]

On Sun, Jan 26, 2014 at 08:02:42PM +0100, Max Reitz wrote:
> The fail and success paths of bdrv_file_open() may be further shortened
> by reusing code already existent in bdrv_open(). This includes
> bdrv_file_open() not taking the reference to options which allows the
> removal of QDECREF(options) in that function.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block.c | 33 ++++++++++++---------------------
>  1 file changed, 12 insertions(+), 21 deletions(-)
> 
> diff --git a/block.c b/block.c
> index f847c4b..b1bae23 100644
> --- a/block.c
> +++ b/block.c
> @@ -943,9 +943,7 @@ free_and_fail:
>   * Opens a file using a protocol (file, host_device, nbd, ...)
>   *
>   * options is a QDict of options to pass to the block drivers, or NULL for an
> - * empty set of options. The reference to the QDict belongs to the block layer
> - * after the call (even on failure), so if the caller intends to reuse the
> - * dictionary, it needs to use QINCREF() before calling bdrv_file_open.
> + * empty set of options.
>   */
>  static int bdrv_file_open(BlockDriverState *bs, const char *filename,
>                            QDict *options, int flags, Error **errp)
> @@ -1010,8 +1008,8 @@ static int bdrv_file_open(BlockDriverState *bs, const char *filename,
>      }
>  
>      if (!drv->bdrv_file_open) {
> +        QINCREF(options);
>          ret = bdrv_open(&bs, filename, NULL, options, flags, drv, &local_err);
> -        options = NULL;
>      } else {
>          ret = bdrv_open_common(bs, NULL, options, flags, drv, &local_err);
>      }
> @@ -1020,21 +1018,10 @@ static int bdrv_file_open(BlockDriverState *bs, const char *filename,
>          goto fail;
>      }
>  
> -    /* Check if any unknown options were used */
> -    if (options && (qdict_size(options) != 0)) {
> -        const QDictEntry *entry = qdict_first(options);
> -        error_setg(errp, "Block protocol '%s' doesn't support the option '%s'",
> -                   drv->format_name, entry->key);
> -        ret = -EINVAL;
> -        goto fail;
> -    }
> -    QDECREF(options);
> -
>      bs->growable = 1;
>      return 0;
>  
>  fail:
> -    QDECREF(options);
>      return ret;
>  }
>  
> @@ -1238,7 +1225,6 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
>          assert(!drv);
>          ret = bdrv_file_open(bs, filename, options, flags & ~BDRV_O_PROTOCOL,
>                               &local_err);
> -        options = NULL;
>          if (ret) {
>              if (bs->drv) {
>                  goto close_and_fail;
> @@ -1246,8 +1232,7 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
>                  goto fail;
>              }
>          }
> -        *pbs = bs;
> -        return 0;
> +        goto done;
>      }
>  
>      /* For snapshot=on, create a temporary qcow2 overlay */
> @@ -1377,12 +1362,18 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
>          }
>      }
>  
> +done:
>      /* Check if any unknown options were used */
>      if (qdict_size(options) != 0) {
>          const QDictEntry *entry = qdict_first(options);
> -        error_setg(errp, "Block format '%s' used by device '%s' doesn't "
> -                   "support the option '%s'", drv->format_name, bs->device_name,
> -                   entry->key);
> +        if (flags & BDRV_O_PROTOCOL) {
> +            error_setg(errp, "Block protocol '%s' doesn't support the option "
> +                       "'%s'", drv->format_name, entry->key);

Tests 071 and 072 segfault, and gdb shows that it occurs here.  More
investigation shows that entry is NULL, although qdict_size() is
returning 1.

> +        } else {
> +            error_setg(errp, "Block format '%s' used by device '%s' doesn't "
> +                       "support the option '%s'", drv->format_name,
> +                       bs->device_name, entry->key);
> +        }
>  
>          ret = -EINVAL;
>          goto close_and_fail;
> -- 
> 1.8.5.3
> 
>